PDF Solutions (PDFS) 10-K 1 Mar 23 2022 FY Annual report Financial data

Document And Entity Information

Document And Entity Information - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Feb. 24, 2023	Jun. 30, 2021
Document and Entity Information
Document Type	10-K
Document Annual Report	true
Document Period End Date	Dec. 31, 2022
Document Transition Report	false
Entity File Number	000-31311
Entity Registrant Name	PDF SOLUTIONS INC
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	25-1701361
Entity Address, Address Line One	2858 De La Cruz Blvd.
Entity Address, City or Town	Santa Clara
Entity Address, State or Province	CA
Entity Address, Postal Zip Code	95050
City Area Code	408
Local Phone Number	280-7900
Title of 12(b) Security	Common Stock, $0.00015 par value
Trading Symbol	PDFS
Security Exchange Name	NASDAQ
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
ICFR Auditor Attestation Flag	true
Entity Shell Company	false
Entity Public Float			$ 601
Entity Common Stock, Shares Outstanding		37,768,010
Entity Central Index Key	0001120914
Amendment Flag	false
Current Fiscal Year End Date	--12-31
Document Fiscal Period Focus	FY
Document Fiscal Year Focus	2022
Auditor Name	BPM LLP
Auditor Firm ID	207
Auditor Location	San Jose, CA

CONSOLIDATED BALANCE SHEETS

CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021
Current assets:
Cash and cash equivalents	$ 119,624	$ 27,684
Short-term investments	19,557	112,542
Accounts receivable, net	42,164	40,087
Prepaid expenses and other current assets	12,063	8,194
Total current assets	193,408	188,507
Property and equipment, net	40,174	35,295
Operating lease right-of-use assets, net	6,002	5,408
Goodwill	14,123	14,123
Intangible assets, net	18,055	21,239
Deferred tax assets, net	64	75
Other non-current assets	6,845	9,121
Total assets	278,671	273,768
Current liabilities:
Accounts payable	6,388	5,554
Accrued compensation and related benefits	16,948	9,495
Accrued and other current liabilities	5,581	3,328
Operating lease liabilities - current portion	1,412	1,758
Deferred revenues - current portion	26,019	23,691
Billings in excess of recognized revenues	1,852
Total current liabilities	58,200	43,826
Long-term income taxes payable	2,622	2,656
Non-current operating lease liabilities	5,932	5,258
Non-current portion of deferred revenue	1,905	2,443
Total liabilities	68,659	54,183
Commitments and contingencies (Note 8)
Stockholders' equity:
Preferred stock, $0.00015 par value, 5,000 shares authorized, no shares issued and outstanding
Common stock, $0.00015 par value, 70,000 shares authorized; shares issued 48,613 and 47,414, respectively; shares outstanding 37,431 and 37,411, respectively	6	6
Additional paid-in-capital	447,415	423,069
Treasury stock at cost, 11,182 and 10,003 shares, respectively	(133,709)	(104,705)
Accumulated deficit	(101,150)	(97,721)
Accumulated other comprehensive loss	(2,550)	(1,064)
Total stockholders' equity	210,012	219,585
Total liabilities and stockholders' equity	$ 278,671	$ 273,768

CONSOLIDATED BALANCE SHEETS (Pa

CONSOLIDATED BALANCE SHEETS (Parentheticals) - $ / shares shares in Thousands	Dec. 31, 2022	Dec. 31, 2021
CONSOLIDATED BALANCE SHEETS
Preferred stock, par value (in dollars per share)	$ 0.00015
Preferred stock, shares authorized (in shares)	5,000
Preferred stock, shares issued (in shares)	0
Preferred stock, shares outstanding (in shares)	0
Common stock, par value (in dollars per share)	$ 0.00015
Common stock, shares authorized (in shares)	70,000
Common stock, shares issued (in shares)	48,613	47,414
Common stock, shares outstanding (in shares)	37,431	37,411
Treasury stock, shares (in shares)	11,182	10,003

CONSOLIDATED STATEMENTS OF COMP

CONSOLIDATED STATEMENTS OF COMPREHENSIVE LOSS - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Revenues:
Revenues	$ 148,549	$ 111,060	$ 88,046
Costs and Expenses:
Costs of revenues	47,907	44,193	36,765
Research and development	56,126	43,780	34,654
Selling, general and administrative	45,338	37,649	32,677
Amortization of acquired intangible assets	1,270	1,255	741
Interest and other expense (income), net	(2,562)	(683)	1,269
Income (loss) before income taxes	470	(18,317)	(18,060)
Income tax expense	3,899	3,171	22,303
Net income (loss)	(3,429)	(21,488)	(40,363)
Other comprehensive loss:
Foreign currency translation adjustments, net of tax	(1,493)	(825)	1,253
Change in unrealized gain (loss) related to available-for-sale debt securities, net of tax	7	(14)	2
Total other comprehensive loss	(1,486)	(839)	1,255
Comprehensive income (loss)	$ (4,915)	$ (22,327)	$ (39,108)
Net income (loss) per share, basic (in dollars per share)	$ (0.09)	$ (0.58)	$ (1.17)
Net income (loss) per share, diluted (in dollars per share)	$ (0.09)	$ (0.58)	$ (1.17)
Weighted average common shares used to calculate net income (loss) per share, basic (in shares)	37,309	37,138	34,458
Weighted average common shares used to calculate net income (loss) per share, diluted (in shares)	37,309	37,138	34,458
Analytics
Revenues:
Revenues	$ 130,480	$ 93,415	$ 57,232
Integrated Yield Ramp
Revenues:
Revenues	$ 18,069	$ 17,645	$ 30,814

CONSOLIDATED STATEMENTS OF STOC

CONSOLIDATED STATEMENTS OF STOCKHOLDERS EQUITY - USD ($) shares in Thousands, $ in Thousands	Common Stock Outstanding	Additional Paid-in Capital	Treasury Stock	Retained Earnings	AOCI Attributable to Parent	Total
Balances (in shares) at Dec. 31, 2019	32,503		9,294
Balances at Dec. 31, 2019	$ 5	$ 325,197	$ (91,695)	$ (35,870)	$ (1,480)	$ 196,157
Issuance of common stock, net of issuance of $0.1 million	$ 1	65,077				65,078
Issuance of common stock, net of issuance of $0.1 million (in shares)	3,307
Issuance of common stock in connection with employee stock purchase plan (in shares)	183
Issuance of common stock in connection with employee stock purchase plan		1,670				$ 1,670
Issuance of common stock in connection with exercise of options (in shares)	246					246
Issuance of common stock in connection with exercise of options		2,570				$ 2,570
Vesting of restricted stock units (in shares)	611
Purchases of treasury stock in connection with tax withholdings on restricted stock grants (in shares)			256
Purchases of treasury stock in connection with tax withholdings on restricted stock grants			$ (4,520)			(4,520)
Stock-based compensation expense		12,659				12,659
Comprehensive income (loss)				(40,363)	1,255	(39,108)
Balances (in shares) at Dec. 31, 2020	36,850		9,550
Balances at Dec. 31, 2020	$ 6	407,173	$ (96,215)	(76,233)	(225)	234,506
Issuance of common stock in connection with employee stock purchase plan (in shares)	109
Issuance of common stock in connection with employee stock purchase plan		1,035				$ 1,035
Issuance of common stock in connection with exercise of options (in shares)	216					216
Issuance of common stock in connection with exercise of options		1,930				$ 1,930
Vesting of restricted stock units (in shares)	487
Purchases of treasury stock in connection with tax withholdings on restricted stock grants (in shares)			202
Purchases of treasury stock in connection with tax withholdings on restricted stock grants			$ (3,967)			(3,967)
Repurchase of common stock (in shares)	(251)		251
Repurchase of common stock			$ (4,523)			(4,523)
Stock-based compensation expense		12,931				12,931
Comprehensive income (loss)				(21,488)	(839)	(22,327)
Balances (in shares) at Dec. 31, 2021	37,411		10,003
Balances at Dec. 31, 2021	$ 6	423,069	$ (104,705)	(97,721)	(1,064)	219,585
Balances (in shares) at Dec. 31, 2020	36,850		9,550
Balances at Dec. 31, 2020	$ 6	407,173	$ (96,215)	(76,233)	(225)	234,506
Balances (in shares) at Dec. 31, 2022	37,431		11,182
Balances at Dec. 31, 2022	$ 6	447,415	$ (133,709)	(101,150)	(2,550)	210,012
Balances (in shares) at Dec. 31, 2021	37,411		10,003
Balances at Dec. 31, 2021	$ 6	423,069	$ (104,705)	(97,721)	(1,064)	219,585
Issuance of common stock in connection with employee stock purchase plan (in shares)	187
Issuance of common stock in connection with employee stock purchase plan		3,011				$ 3,011
Issuance of common stock in connection with exercise of options (in shares)	150					150
Issuance of common stock in connection with exercise of options		1,686				$ 1,686
Vesting of restricted stock units (in shares)	616
Purchases of treasury stock in connection with tax withholdings on restricted stock grants (in shares)			246
Purchases of treasury stock in connection with tax withholdings on restricted stock grants			$ (6,533)			(6,533)
Repurchase of common stock (in shares)	(933)		933
Repurchase of common stock			$ (22,471)			(22,471)
Stock-based compensation expense		(19,649)				(19,649)
Comprehensive income (loss)				(3,429)	(1,486)	(4,915)
Balances (in shares) at Dec. 31, 2022	37,431		11,182
Balances at Dec. 31, 2022	$ 6	$ 447,415	$ (133,709)	$ (101,150)	$ (2,550)	$ 210,012

CONSOLIDATED STATEMENTS OF CASH

CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($)	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Cash flows from operating activities:
Net loss	$ (3,429,000)	$ (21,488,000)	$ (40,363,000)
Adjustments to reconcile net loss to net cash provided by (used in) operating activities:
Depreciation and amortization	5,526,000	6,218,000	6,725,000
Stock-based compensation expense	19,649,000	12,931,000	12,463,000
Amortization of acquired intangible assets	3,484,000	3,334,000	1,446,000
Amortization of costs capitalized to obtain revenue contracts	1,550,000	674,000	549,000
Loss on disposal and write-down in value of property and equipment		3,183,000	500,000
Deferred taxes	(4,000)	1,373,000	21,007,000
Other	(187,000)	147,000	(25,000)
Changes in operating assets and liabilities:
Accounts receivable	(2,143,000)	(5,980,000)	8,101,000
Prepaid expenses and other current assets	(5,787,000)	1,136,000	(433,000)
Operating lease right-of-use assets	1,821,000	1,414,000	1,193,000
Other non-current assets	2,258,000	(1,336,000)	2,069,000
Accounts payable	(1,423,000)	(86,000)	(918,000)
Accrued compensation and related benefits	7,720,000	1,264,000	1,926,000
Accrued and other liabilities	1,671,000	(648,000)	928,000
Deferred revenues	1,822,000	5,028,000	7,755,000
Billings in excess of recognized revenues	1,852,000	(1,337,000)	220,000
Operating lease liabilities	(2,082,000)	(1,584,000)	(1,360,000)
Net cash provided by (used in) operating activities	32,298,000	4,243,000	21,783,000
Cash flows from investing activities:
Proceeds from maturities and sales of short-term investments	151,500,000	171,000,000	16,500,000
Purchases of short-term investments	(58,321,000)	(168,560,000)	(131,454,000)
Purchases of property and equipment	(8,409,000)	(3,672,000)	(6,005,000)
Prepayment for the purchase of property and equipment	(21,000)	(381,000)	(963,000)
Purchases of intangible assets	150,000
Payment for business acquisition, net of cash acquired		(3,054,000)	(28,580,000)
Net cash provided by investing activities	84,599,000	(4,667,000)	(150,502,000)
Cash flows from financing activities:
Proceeds from exercise of stock options	1,686,000	1,930,000	2,570,000
Proceeds from employee stock purchase plan	3,011,000	1,035,000	1,670,000
Payments for taxes related to net share settlement of equity awards	(6,533,000)	(3,967,000)	(4,520,000)
Repurchases of common stock	(22,471,000)	(4,523,000)
Proceeds from issuance of common stock, net of issuance costs paid			65,078,000
Net cash used in financing activities	(24,307,000)	(5,525,000)	64,798,000
Effect of exchange rate changes on cash and cash equivalents	(650,000)	(182,000)	131,000
Net change in cash, cash equivalents, and restricted cash	91,940,000	(6,131,000)	(63,790,000)
Cash, cash equivalents, and restricted cash at beginning of period	27,684,000	33,815,000	97,605,000
Cash, cash equivalents, and restricted cash at end of period	119,624,000	27,684,000	33,815,000
Reconciliation of cash, cash equivalents, and restricted cash to the balance sheets:
Cash and cash equivalents	119,624,000	27,684,000	30,315,000
Restricted cash			3,500,000
Total cash, cash equivalents and restricted cash	119,624,000	27,684,000	33,815,000
Supplemental disclosure of cash flow information:
Cash paid during the period for taxes	2,850,000	1,873,000	2,707,000
Cash paid for amounts included in the measurement of operating lease liabilities	1,744,000	1,947,000	2,022,000
Supplemental disclosure of noncash information:
Property and equipment received and accrued in accounts payable and accrued and other liabilities	3,201,000	1,359,000	133,000
Advances for purchase of fixed assets transferred from prepaid assets to property and equipment	336,000	963,000
Operating lease liabilities arising from obtaining right-of-use assets	$ 2,502,000	$ 161,000	286,000
Stock-based compensation capitalized as software development costs			$ 190,000

DESCRIPTION OF BUSINESS AND SUM

DESCRIPTION OF BUSINESS AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES	12 Months Ended
	Dec. 31, 2022
BASIS OF PRESENTATION AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES
DESCRIPTION OF BUSINESS AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES	1. DESCRIPTION OF BUSINESS AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES Description of Business PDF Solutions, Inc. (the “Company” or “PDF”), provides products and services designed to empower organizations across the semiconductor ecosystem to connect, collect, manage, and analyze data about design, equipment, manufacturing, and test to improve the yield and quality of their products and operational efficiency. The Company’s products, services, and solutions include proprietary software, physical intellectual property (“IP”) for integrated circuit (“IC”) designs, electrical measurement hardware tools, proven methodologies, and professional services. Basis of Presentation The consolidated financial statements include the accounts of the Company and its wholly-owned subsidiaries after the elimination of all significant intercompany balances and transactions. Use of Estimates The preparation of financial statements in conformity with generally accepted accounting principles in the United States (“U.S. GAAP”) requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, the disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenues and expenses during the reporting period. Significant estimates in these financial statements include revenue recognition, the estimated useful lives of property and equipment and intangible assets, assumptions made in analysis of allowance for doubtful accounts, fair values of assets acquired and liabilities assumed in business combinations, impairment of goodwill and long-lived assets, valuation for deferred tax assets, and accounting for lease obligations, stock-based compensation expense, and income tax uncertainties and contingencies. Actual results could differ from those estimates and may result in material effects on the Company’s operating results and financial position. The global COVID-19 pandemic has impacted the operations and purchasing decisions of companies worldwide. As of the date of issuance of the consolidated financial statements, the Company is not aware of any specific event or circumstance relating to COVID-19 that would require updates to the Company’s estimates and judgments or revisions to the carrying value of its assets or liabilities. These estimates may change, as new events occur and additional information is obtained, and are recognized in the consolidated financial statements as soon as they become known. Actual results could differ from those estimates and any such differences may be material to the financial statements. Concentration of Credit Risk Financial instruments that potentially expose the Company to concentrations of credit risk consist primarily of cash and cash equivalents, short-term investments, and accounts receivable. The Company maintains its cash and cash equivalents and short-term investments with what it considers high credit quality financial institutions. The Company primarily sells its products and services to companies in Asia, Europe and North America within the semiconductor industry. As of December 31, 2022, three customers accounted for 53% of the Company’s gross accounts receivable and two customers accounted for 41% of the Company’s total revenues for 2022. As of December 31, 2021, two customers accounted for 44% of the Company’s gross accounts receivable and two customers accounted for 27% of the Company’s revenues for 2021. See Note 13 for further details. The Company does not require collateral or other security to support accounts receivable. To reduce credit risk, management performs ongoing credit evaluations of its customers’ financial condition. The Company maintains allowances for potential credit losses. The allowance for doubtful accounts, which was based on management’s best estimates, could be adjusted in the near term from current estimates depending on actual experience. Such adjustments could be material to the consolidated financial statements. Cash and Cash Equivalents, and Short-term Investments The Company considers all highly liquid investments with an original maturity of 90 days or less or investments with a remaining maturity of 90 days or less at the purchase to be cash equivalents and investments with original maturities greater than 90 days but less than one year to be short-term investments. The Company classifies securities with readily determinable market values as available-for-sale. Short-term investments include available-for-sale securities and are carried at estimated fair value, with the unrealized gains and losses deemed temporary in nature, net of tax, reported as a component of accumulated other comprehensive loss in stockholders’ equity. Realized gains and losses and declines in value determined to be other than temporary are based on the specific identification method and are included as a component of other expense, net in the Consolidated Statements of Comprehensive Loss. The Company periodically reviews short-term investments for impairment. In the event a decline in value is determined to be other-than-temporary, an impairment loss is recognized. When determining if a decline in value is other-than-temporary, the Company takes into consideration the current market conditions, the duration and severity of and the reason for the decline, and the likelihood that it would need to sell the security prior to a recovery of par value. As of December 31, 2022, and 2021, short-term investments consisted solely of U.S. Treasury bills. The cost of these securities approximated fair value and there was no material gross realized or unrealized gains or losses as of December 31, 2022 and 2021. There were also no impairments in the investments’ value in the year ended December 31, 2022 and 2021. Refer to Note 14, “Fair Value Measurements” for further discussion on the Company’s investments. Restricted cash of $3.5 million noted in the Consolidated Statement of Cash Flows for the year ended December 31, 2020 pertains to the amount specifically designated to pay for the Holdback amount related to the Company’s acquisition of Cimetrix Incorporated (“Cimetrix”). Refer to Note 4, “Business Combination” for further discussion about the payment of Holdback Amount in fiscal 2021. Accounts Receivable Accounts receivable include amounts that are unbilled at the end of the period that are expected to be billed and collected within a 12-month period. Unbilled accounts receivable are determined on an individual contract basis. Unbilled accounts receivable, included in accounts receivable, totaled $13.5 million and $11.8 million as of December 31, 2022 and 2021, respectively. Unbilled accounts receivable that are not expected to be billed and collected during the succeeding 12-month period are recorded in other non-current assets and totaled $0.8 million and $1.3 million as of December 31, 2022 and 2021, respectively. The Company performs ongoing credit evaluations of its customers’ financial condition. An allowance for doubtful accounts is maintained for probable credit losses based upon the Company’s assessment of the expected collectability of the accounts receivable. The allowance for doubtful accounts is reviewed on a quarterly basis to assess the adequacy of the allowance. Accounts receivable reserves are summarized below (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Deductions/ ​ ​ ​ ​ Balance at ​ ​ ​ ​ Charged ​ Write-offs ​ Balance at ​ ​ Beginning ​ Charged to ​ Against ​ of Accounts ​ End of ​ of Period Expense (1) Revenue (1) Receivable Period 2022 ​ $ 890 ​ $ — ​ $ — ​ $ — ​ $ 890 2021 ​ $ 963 ​ $ — ​ $ — ​ $ (73) ​ $ 890 2020 ​ $ 213 ​ $ — ​ $ 800 ​ $ (50) ​ $ 963 (1) Additions to the accounts receivable reserve for doubtful accounts are charged to bad debt expense. Additions to the receivable reserve for billing adjustments are charged against revenue. Property and Equipment Property and equipment are stated at cost and are depreciated using the straight-line method over the estimated useful lives (in years) of the related asset as follows: ​ ​ ​ ​ Computer equipment 3 Software 3 Furniture, fixtures, and equipment 5-10 Laboratory and test equipment 3-10 Leasehold improvements ​ Shorter of estimated useful life or term of lease ​ Intangible Assets Intangible assets consist of acquired technology, certain contract rights, customer relationships, patents, trademarks and trade names. These intangible assets may be acquired through business combinations or direct purchases. Intangible assets are amortized on a straight-line basis over their estimated useful lives which range from one ten Goodwill The Company records goodwill when the purchase consideration of an acquisition exceeds the fair value of the net tangible and identified intangible assets as of the date of acquisition. The Company has one operating segment and one operating unit. The Company performs a qualitative analysis when testing a reporting unit’s goodwill for impairment. The Company performs an annual impairment assessment of goodwill during the fourth quarter of each calendar year or more frequently, if required to determine if any events or circumstances exist, such as an adverse change in business climate or a decline in the overall industry demand, that would indicate that it would more likely than not reduce the fair value of a reporting unit below its carrying amount, including goodwill. If events or circumstances do not indicate that the fair value of a reporting unit is below its carrying amount, then goodwill is not considered to be impaired and no further testing is required. If the carrying amount exceeds its fair value, an impairment loss would be recognized equal to the amount of excess, limited to the amount of total goodwill. Leases The Company has operating leases for administrative and sales offices, research and development laboratory and clean room. The Company recognizes long-term operating lease rights and commitments as operating lease right-of-use assets (ROU), operating lease liabilities and operating lease liabilities, non-current, respectively, in the Consolidated Balance Sheets. The Company elected to not separate lease and non-lease components for all of its leases. The Company determines if an arrangement is, or contains, a lease at inception. Operating lease right-of-use assets, and operating lease liabilities are initially recorded based on the present value of lease payments over the lease term. Lease terms include the minimum unconditional term of the lease, and may include options to extend or terminate the lease when it is reasonably certain at the commencement date that such options will be exercised. The decision to include these options involves consideration of our overall future business plans and other relevant business economic factors that may affect our business. Since the determination of the lease term requires an application of judgment, lease terms that differ in reality from our initial judgment may potentially have a material impact on the Company’s Consolidated Balance Sheets. In addition, the Company’s leases do not provide an implicit rate. In determining the present value of the Company’s expected lease payments, the discount rate is calculated using the Company’s incremental borrowing rate determined based on the information available, which requires additional judgment. Software Development Costs Internally developed software is software developed to meet our internal needs to provide certain services to the customers. The Company’s capitalized software development costs consist of internal compensation related costs and external direct costs incurred during the application development stage and are amortized over their useful lives, generally five six Cost of Revenues Costs of revenues consist primarily of costs incurred to provide and support our services, costs recognized in connection with licensing our software, IT and facilities-related costs and amortization of acquired technology. Service costs include material, personnel-related costs including compensation, employee benefits, bonus and stock-based compensation expense, subcontractor costs, overhead costs, travel, and allocated facilities-related costs. Software license costs consist of costs associated with cloud-delivery related expenses and licensing third-party software used by us in providing services to the Company’s customers in solution engagements or sold in conjunction with the Company’s software products. Research and Development Expenses Research and development expenses consist primarily of personnel-related costs including compensation, employee benefits, bonus and stock-based compensation expense, outside development services, travel, third-party cloud-services related costs, IT and facilities cost allocations to support product development activities. Research and development expenses are charged to operations as incurred. Selling, General and Administrative Expenses Selling, general and administrative expenses consist primarily of personnel-related costs including compensation, employee benefits, bonus, commission and stock-based compensation expense for sales, marketing and general and administrative personnel, legal, tax and accounting services, marketing communications expenses, third-party cloud-services related costs, travel, IT and facilities cost allocations. Stock-Based Compensation The Company accounts for stock-based compensation using the fair value method, which requires the Company to measure stock-based compensation based on the grant-date fair value of the awards and recognize the compensation expense over the requisite service period. As stock-based compensation expense recognized is based on awards ultimately expected to vest, it has been reduced for estimated forfeitures. Forfeitures are estimated at the time of grant and revised, if necessary, in subsequent periods if actual forfeitures differ from those estimates. The fair value of the Company’s restricted stock units (“RSUs”) is equal to the market value of the Company’s common stock on the date of the grant. These awards are subject to time-based vesting which generally occurs over a period of four years The fair value of the Company’s stock options is estimated using the Black-Scholes-Merton option-pricing model, which incorporates various assumptions including volatility, expected life and interest rates. The expected volatility is based on the historical volatility of the Company’s common stock over the most recent period commensurate with the estimated expected life of the Company’s stock options. The expected life is based on historical experience and on the terms and conditions of the stock options granted. The interest rate assumption is based upon observed Treasury yield curve rates appropriate for the expected life of the Company’s stock options. Income Taxes The Company’s provision for income tax comprises its current tax liability and change in deferred tax assets and liabilities. Deferred tax assets and liabilities are recognized for the expected tax consequences of temporary differences between the tax bases of assets and liabilities. The measurement of current and deferred tax assets and liabilities is based on provisions of enacted tax laws; the effect of future changes in tax laws or rates are not anticipated. Valuation allowances are provided to reduce deferred tax assets to an amount that in management’s judgment is more likely than not to be recoverable against future taxable income. No U.S. taxes are provided on earnings of non-U.S. subsidiaries, to the extent such earnings are deemed to be permanently invested. The Company’s income tax calculations are based on application of applicable U.S. federal and state or foreign tax laws. The Company’s tax filings, however, are subject to audit by the respective tax authorities. Accordingly, the Company recognizes tax liabilities based upon its estimate of whether, and the extent to which, additional taxes will be due when such estimates are more-likely-than-not to be sustained. An uncertain income tax position will not be recognized if it has less than a 50% likelihood of being sustained. To the extent the final tax liabilities are different from the amounts originally accrued, the increases or decreases are recorded as income tax expense or benefit in the Consolidated Statements of Comprehensive Loss. Net Income (Loss) Per Share Basic net income (loss) per share is computed by dividing net income by weighted average number of common shares outstanding for the period (excluding outstanding stock options and shares subject to repurchase). Diluted net income (loss) per share is computed using the weighted-average number of common shares outstanding for the period plus the potential effect of dilutive securities which are convertible into common shares (using the treasury stock method), except in cases in which the effect would be anti-dilutive. Dilutive potential common shares consist of incremental common shares issuable upon exercise of stock options, upon vesting of RSUs, contingently issuable shares for all periods and assumed issuance of shares under the Company’s employee stock purchase plan. No dilutive potential common shares are included in the computation of any diluted per share amount when a loss from continuing operations was reported by the Company. Foreign Currency Translation The functional currency of the Company’s foreign subsidiaries is the local currency for the respective subsidiary. The assets and liabilities are translated at the period-end exchange rate, and statements of comprehensive loss are translated at the average exchange rate during the year. Gains and losses resulting from foreign currency translations are included as a component of other comprehensive loss. Gains and losses resulting from foreign currency transactions are included in the Consolidated Statements of Comprehensive Loss. Derivative Financial Instruments The Company operates internationally and is exposed to potentially adverse movements in foreign currency exchange rates. From time to time, the Company enters into foreign currency forward contracts to reduce the exposure to foreign currency exchange rate fluctuations on certain foreign currency denominated monetary assets and liabilities. The Company does not use foreign currency contracts for speculative or trading purposes. The Company records these forward contracts at fair value. The counterparty to these foreign currency forward contracts is a financial institution that the Company believes is creditworthy, and therefore, we believe the credit risk of counterparty non-performance is not significant. These foreign currency forward contracts are not designated for hedge accounting treatment. Therefore, the change in fair value of these derivatives is recorded into earnings as a component of interest and other income (expense), net and offsets the change in fair value of the foreign currency denominated monetary assets and liabilities, which are also recorded in interest and other income (expense), net. The duration of these forward contracts is usually three months. Business Combinations The Company allocates the fair value of purchase consideration to the tangible assets acquired, liabilities assumed and intangible assets acquired based on their estimated fair values at the date of the business combination. The excess of the fair value of purchase consideration over the fair values of these identifiable assets and liabilities is recorded as goodwill. Such valuations require management to make significant estimates and assumptions, especially with respect to intangible assets. Significant estimates in valuing certain intangible assets include, but are not limited to, estimated replacement costs and future expected cash flows from acquired customers, acquired technology, acquired patents, and trade names from a market participant perspective, useful lives and discount rates. Management’s estimates of fair value are based upon assumptions believed to be reasonable, but which are inherently uncertain and unpredictable and, as a result, actual results may differ from estimates. Allocation of purchase consideration to identifiable assets and liabilities affects the Company’s amortization expense, as acquired finite-lived intangible assets are amortized over the useful life, whereas any indefinite lived intangible assets, including in-process research and development, and goodwill, are not amortized but tested annually for impairment. During the measurement period, which is not to exceed one year from the acquisition date, the Company records adjustments to the assets acquired and liabilities assumed, with the corresponding offset to goodwill. Upon the conclusion of the measurement period, any subsequent adjustments are recorded to earnings. Litigation From time to time, the Company is subject to various claims and legal proceedings that arise in the ordinary course of business. The Company accrues for losses related to litigation when a potential loss is probable and the loss can be reasonably estimated in accordance with Financial Accounting Standards Board (FASB) requirements. See Note 8, “Commitments and Contingencies”. Accounting Standards Not Yet Effective In June 2016, the FASB issued ASU No. 2016-13, Financial Instruments – Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments (ASU 2016-13), which requires measurement and recognition of expected credit losses for financial assets held at the reporting date based on internal information, external information, or a combination of both relating to past events, current conditions, and reasonable and supportable forecasts. ASU No. 2016-13 replaces the existing incurred loss impairment model with a forward-looking expected credit loss model, which will result in earlier recognition of credit losses. Subsequent to the issuance of ASU No. 2016-13, the FASB issued ASU No. 2018-19, Codification Improvements to Topic 326, Financial Instruments – Credit Losses, ASU No. 2019-04, Codification Improvements to Topic 326, Financial Instruments – Credit Losses, Topic 815, Derivatives and Hedging, and Topic 825, Financial Instrument, ASU No. 2019-05, Financial Instruments – Credit Losses (Topic 326) Targeted Transition Relief, ASU No. 2016-13, ASU No. 2019-10 Financial Instruments-Credit Losses (Topic 326), Derivatives and Hedging (Topic 815), and Leases (Topic 842), and ASU No. 2019-11 Codification Improvements to Topic 326, Financial Instruments-Credit Losses. The subsequent ASUs do not change the core principle of the guidance in ASU No. 2016-13. Instead, these amendments are intended to clarify and improve operability of certain topics included within ASU No. 2016-13. Additionally, ASU No. 2019-10 defers the effective date for the adoption of the new standard on credit losses for public filers that are considered small reporting companies (“SRC”) as defined by the SEC to fiscal years beginning after December 15, 2022, including interim periods within those fiscal years. The Company will adopt this standard effective the first quarter of 2023. In February 2020, the FASB issued ASU 2020-02, which provides guidance regarding methodologies, documentation, and internal controls related to expected credit losses. The subsequent amendments will have the same effective date and transition requirements as ASU No. 2016-13. Topic 326 requires a modified retrospective approach by recording a cumulative-effect adjustment to retained earnings as of the beginning of the period of adoption. The Company is in the process of evaluating the impact of Topic 326 on its consolidated financial statements and the related disclosure but does not believe it will have a material effect. Management has reviewed other recently issued accounting pronouncements issued or proposed by the FASB, and does not believe any of these accounting pronouncements has had or will have a material impact on the consolidated financial statements.

REVENUE

REVENUE	12 Months Ended
	Dec. 31, 2022
REVENUE
REVENUE	​ ​ 2. REVENUE The Company derives revenue from two sources: Analytics revenue and Integrated Yield Ramp revenue. The Company recognizes revenue in accordance with FASB ASC Topic 606, Revenue from Contracts with Customers The Company determines revenue recognition through the following five steps: ● Identification of the contract, or contracts, with a customer ● Identification of the performance obligations in the contract ● Determination of the transaction price ● Allocation of the transaction price to the performance obligations in the contract ● Recognition of revenue when, or as, performance obligations are satisfied The Company accounts for a contract when it has approval and commitment from both parties, the rights of the parties are identified, payment terms are identified, the contract has commercial substance, and collectability of consideration is probable. Contracts with multiple performance obligations The Company enters into contracts that can include various combinations of licenses, products and services, some of which are distinct and are accounted for as separate performance obligations. For contracts with multiple performance obligations, the Company allocates the transaction price of the contract to each performance obligation on a relative basis using the standalone selling price (“SSP”). Analytics Revenue Analytics revenue is derived from the following primary offerings: licenses and services for standalone software (which is primarily Exensio ® ® ® Revenue from standalone software is recognized depending on whether the license is perpetual or time-based. Perpetual (one-time charge) license software is recognized at the time of the inception of the arrangement when control transfers to the customers, if the software license is considered as a separate performance obligation from the services offered by the Company. Revenue from post-contract support is recognized over the contract term on a straight-line basis, because we are providing (i) support and (ii) unspecified software updates on a when-and-if available basis over the contract term. Revenue from time-based-licensed software is allocated to each performance obligation and is recognized either at a point in time or over time as follows. The license component is recognized at the time when control transfers to customers, with the post-contract support component recognized ratably over the committed term of the contract. For contracts with any combination of licenses, support, and other services, distinct performance obligations are accounted for separately. For contracts with multiple performance obligations, we allocate the transaction price of the contract to each performance obligation on a relative basis using the SSP attributed to each performance obligation. Revenue from SaaS arrangements, which allow for the use of a cloud-based software product or service over a contractually determined period of time without the customer having to take possession of software, is accounted for as a subscription and is recognized as revenue ratably, on a straight-line basis, over the subscription period beginning on the date the service is first made available to customers. For contracts with any combination of SaaS and related services, distinct performance obligations are accounted for separately. For contracts with multiple performance obligations, we allocate the transaction price of the contract to each performance obligation on a relative basis using SSP attributed to each performance obligation. Revenue from DFI systems and CV systems (including Characterization services) that do not include performance incentives based on customers’ yield achievement is recognized primarily as services are performed. Where there are distinct performance obligations, the Company allocates revenue to all deliverables based on their SSPs. For those contracts with multiple performance obligations, the Company allocates the transaction price of the contract to each performance obligation on a relative basis using SSP attributed to each performance obligation. Where there are not discrete performance obligations, historically, revenue is primarily recognized as services are performed using a percentage of completion method based on costs or labor-hours inputs, whichever is the most appropriate measure of the progress towards completion of the contract. The estimation of percentage of completion method is complex and subject to many variables that require significant judgement. Please refer to “Significant Judgments” section of this Note for further discussion. Integrated Yield Ramp Revenue Integrated Yield Ramp revenue is derived from the Company’s fixed-fee engagements that include performance incentives based on customers’ yield achievement (which consists primarily of Gainshare royalties) typically based on customer’s wafer shipments, pertaining to these fixed-price contracts, which royalties are variable. Revenue under these project–based contracts, which are delivered over a specific period of time, typically for a fixed fee component paid on a set schedule, is recognized as services are performed using a percentage of completion method based on costs or labor-inputs, whichever is the most appropriate measure of the progress towards completion of the contract. Where there are distinct performance obligations, the Company allocates revenue to all deliverables based on their SSPs and allocates the transaction price of the contract to each performance obligation on a relative basis using SSP. Similar to the services provided in connection with DFI systems and CV systems that are contributing to Analytics revenue, due to the nature of the work performed in these arrangements, the estimation of percentage of completion method is complex and subject to many variables that require significant judgement. Please refer to “Significant Judgments” section of this Note for further discussion. The Gainshare royalty contained in IYR contracts is a variable fee related to continued usage of the Company’s intellectual property after the fixed-fee service period ends, based on a customer’s yield achievement. Revenue derived from Gainshare is contingent upon the Company’s customers reaching certain defined production yield levels. Gainshare royalty periods are generally subsequent to the delivery of all contractual services and performance obligations. The Company records Gainshare as a usage-based royalty derived from customers’ usage of intellectual property and records it in the same period in which the usage occurs. Disaggregation of Revenue The Company disaggregates revenue from contracts with customers into the timing of the transfer of goods and services and the geographical regions. The Company determined that disaggregating revenue into these categories achieves the disclosure objective to depict how the nature, amount, timing, and uncertainty of revenue and cash flows are affected by economic factors. The Company’s performance obligations are satisfied either over time or at a point-in-time. The following table represents a disaggregation of revenue by timing of revenue: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year Ended December 31, ​ 2022 2021 ​ 2020 ​ Over time ​ 69 % 65 % 63 % Point-in-time 31 % 35 % 37 % Total 100 % 100 % 100 % ​ International revenues accounted for approximately 50%, 55% and 58% of total revenues for the years ended December 31, 2022, 2021 and 2020, respectively. See Note 13, “Customer and Geographic Information”. Significant Judgments Judgments and estimates are required under ASC 606. Due to the complexity of certain contracts, the actual revenue recognition treatment required under ASC 606 for the Company’s arrangements may be dependent on contract-specific terms and may vary in some instances. For revenue under project-based contracts for fixed-price implementation services, revenue is recognized as services are performed using a percentage-of-completion method based on costs or labor-hours input method, whichever is the most appropriate measure of the progress towards completion of the contract. Due to the nature of the work performed in these arrangements, the estimation of percentage of completion method is complex, subject to many variables and requires significant judgment. Key factors reviewed by the Company to estimate costs to complete each contract are future labor and product costs and expected productivity efficiencies. If circumstances arise that change the original estimates of revenues, costs, or extent of progress toward completion, revisions to the estimates are made. These revisions may result in increases or decreases in estimated revenues or costs, and such revisions are reflected in revenue on a cumulative catch-up basis in the period in which the circumstances that gave rise to the revision become known. The Company’s contracts with customers often include promises to transfer products, licenses software and provide services, including professional services, technical support services, and rights to unspecified updates to a customer. Determining whether licenses and services are distinct performance obligations that should be accounted for separately, or not distinct and thus accounted for together, requires significant judgment. The Company rarely licenses software on a standalone basis, so the Company is required to estimate the range of SSPs for each performance obligation. In instances where SSP is not directly observable because the Company does not license the software or sell the service separately, the Company determines the SSP using information that may include market conditions and other observable inputs. The Company is required to record Gainshare royalty revenue in the same period in which the usage occurs. Because the Company generally does not receive the acknowledgment reports from its customers during a given quarter within the time frame necessary to adequately review the reports and include the actual amounts in quarterly results for such quarter, the Company accrues the related revenue based on estimates of customers underlying sales achievement. The Company’s estimation process can be based on historical data, trends, seasonality, changes in the contract rate, knowledge of the changes in the industry and changes in the customer’s manufacturing environment learned through discussions with customers and sales personnel. As a result of accruing revenue for the quarter based on such estimates, adjustments will be required in the following quarter to true-up revenue to the actual amounts reported. Contract Balances The Company performs its obligations under a contract with a customer by licensing software or providing services in exchange for consideration from the customer. The timing of the Company’s performance often differs from the timing of the customer’s payment, which results in the recognition of a receivable, a contract asset or a contract liability. The Company classifies the right to consideration in exchange for software or services transferred to a customer as either a receivable or a contract asset. A receivable is a right to consideration that is unconditional, as compared to a contract asset, which is a right to consideration that is conditional upon factors other than the passage of time. The majority of the Company’s contract assets represent unbilled amounts related to fixed-price service contracts when the revenue recognized exceeds the amount billed to the customer. The contract assets are generally classified as current and are recorded on a net basis with deferred revenue (i.e. contract liabilities) at the contract level. At December 31, 2022 and 2021, contract assets of $3.3 million and $0.4 million, respectively, are included in prepaid expenses and other current assets in the accompanying Consolidated Balance Sheets. The Company did not record any asset impairment charges related to contract assets during fiscal year 2022 and 2021. Deferred revenues and billings in excess of recognized revenues consist substantially of amounts invoiced in advance of revenue recognition and are recognized as the revenue recognition criteria are met. Deferred revenues that will be recognized during the succeeding twelve-month period are recorded as current deferred revenues and the remaining portion is recorded as non-current deferred revenues in the accompanying Consolidated Balance Sheets. Revenue recognized for the years ended December 31, 2022, 2021 and 2020, that was included in the deferred revenues and billings in excess of recognized revenues balances at the beginning of each reporting period was $24.9 million, $16.9 million and $10.7 million, respectively. At December 31, 2022, the aggregate amount of the transaction price allocated to the remaining performance obligations related to customer contracts that were unsatisfied or partially unsatisfied was approximately $277.7 million. Given the applicable contract terms with customers, the majority of this amount is expected to be recognized as revenue over the next two years three years The adjustment to revenue recognized in the years ended December 31, 2022, 2021 and 2020 from performance obligations satisfied (or partially satisfied) in previous periods was an increase of $0.4 million, a decrease of $0.4 million and an increase $0.1 million, respectively. These amounts primarily represent changes in estimated percentage-of-completion based contracts and changes in actual versus estimated Gainshare royalty. Costs to obtain or fulfill a contract The Company capitalizes the incremental costs to obtain or fulfill a contract with a customer, including direct sales commissions and related fees, when it expects to recover those costs. Amortization expense related to these capitalized costs is recognized over the period associated with the revenue from which the cost was incurred. Total capitalized direct sales commission costs included in prepaid expenses and other current assets in the accompanying Consolidated Balance Sheets as of December 31, 2022 and 2021 was $1.7 million and $0.6 million, respectively. Total capitalized direct sales commission costs included in other non-current assets in the accompanying Consolidated Balance Sheets as of December 31, 2022 and 2021 was $2.1 million and $2.1 million, respectively. Amortization of these assets for each of the years ended December 31, 2022, 2021 and 2020 was $1.5 Practical Expedients The Company does not adjust transaction price for the effects of a significant financing component when the period between the transfers of the promised good or service to the customer and payment for that good or service by the customer is expected to be one year or less. The Company assessed each of its revenue generating arrangements in order to determine whether a significant financing component exists, and determined its contracts did not include a significant financing component for the years ended December 31, 2022 and 2021.

STRATEGIC PARTNERSHIP AGREEMENT

STRATEGIC PARTNERSHIP AGREEMENT WITH ADVANTEST AND RELATED PARTY TRANSACTIONS	12 Months Ended
	Dec. 31, 2022
STRATEGIC PARTNERSHIP AGREEMENT WITH ADVANTEST AND RELATED PARTY TRANSACTIONS
STRATEGIC PARTNERSHIP AGREEMENT WITH ADVANTEST AND RELATED PARTY TRANSACTIONS	3. STRATEGIC PARTNERSHIP AGREEMENT WITH ADVANTEST AND RELATED PARTY TRANSACTIONS On July 29, 2020, the Company entered into a long-term strategic partnership with Advantest Corporation through its wholly-owned subsidiary, Advantest America, Inc. (collectively referred to herein as “Advantest”) that included the following agreements. ● A Securities Purchase Agreement for the purchase by Advantest of an aggregate of 3,306,924 shares of the Company’s common stock for aggregate gross proceeds of $65.2 million and a related Stockholder Agreement. ● An Amendment #1 to that certain Software License and Related Services Agreement, dated as of March 25, 2020, for an exclusive commercial arrangement in which the Company and Advantest will collaborate on, and the Company will initially host, develop and maintain, an Advantest-specific cloud layer on the Exensio platform. On June 5, 2022, the parties amended Amendment #1 to provide another approved DEX Site (as defined therein). On November 11, 2022, the parties entered into a further amendment to Amendment #1 that provided, effective October 31, 2022: (i) flexibility for Advantest to spend the remainder of their committed $50.0 million over the remainder of the original term on its choice of products and services from a price list, instead of limiting Advantest to the original, fixed bundle of software and services; (ii) revised exclusivity; and (iii) the Company with free access/use of certain Advantest software. ● An Amended and Restated Master Development Agreement with Advantest, pursuant to which the Company and Advantest agreed to collaborate on extensions to or combinations of both of their existing technology and new technology to address mutual customers’ needs through one or more development phases subject to certain conditions as set forth therein. Costs and expenses incurred related to this agreement have no t been significant for the year ended December 31, 2022 and 2021. ● A Master Commercial Terms and Support Services Agreement for the commercialization and support of integrated products of the Company and Advantest that are the outcome of the above development agreement. No material costs and expenses incurred related to the Commercial Agreement with Advantest during the years ended December 31, 2022 and 2021. Analytics revenue recognized from Advantest during the years ended December 31, 2022, 2021 and 2020 was $10.3 million, $10.6 million and $3.4 million, respectively. Accounts receivable from Advantest amounted to $0.3 million at December 31, 2022. There were no outstanding accounts receivable from Advantest at December 31, 2021. Deferred revenue amounted to $7.1 million and $6.8 million as of December 31, 2022 and 2021, respectively. There was no occurrence of any termination events under these agreements as of the issuance of these consolidated financial statements. The Company carries out transactions with Advantest on arm’s length commercial customary terms.

BUSINESS COMBINATION

BUSINESS COMBINATION	12 Months Ended
	Dec. 31, 2022
BUSINESS COMBINATION
BUSINESS COMBINATION	4. BUSINESS COMBINATION On December 1, 2020 (the “Acquisition Date”), the Company acquired all the stock of Cimetrix Incorporated (“Cimetrix”). Cimetrix a global provider of equipment connectivity products for smart manufacturing and Industry 4.0 that enable factory equipment to communicate to increase productivity, reduce costs, and improve quality. The combination of Cimetrix connectivity products and platforms with the Company’s Exensio analytics platform powered by machine learning, is intended to enable IC, assembly, and electronics manufacturer customers to extract more intelligence from their tools, not just data, to build more reliable chips and systems at lower manufacturing costs. The gross purchase price was approximately $37.5 million ($31.6 million net of cash acquired) for all of the outstanding equity of Cimetrix. The net cash payment for this acquisition which also include the payment of adjusted Holdback Amount, as discussed below, was funded from the available cash of the Company. At the Acquisition Date, the Company held back $3.5 million of the purchase price (the “Holdback Amount”) to satisfy adjustments and claims for indemnity arising out of breaches of certain representations, warranties and covenants, and certain other enumerated items in the merger agreement. In fiscal 2021, the Company recorded a measurement period adjustment which reduced the Holdback Amount to $3.1 million. The measurement period adjustment did not have an impact on the Company’s Consolidated Statement of Comprehensive Loss during the year ended December 31, 2021. The adjusted Holdback Amount of $3.1 million was paid to the participating equity holders in December 2021. The Company accounted for this acquisition as a business combination in accordance with FASB ASC Topic 805, Business Combinations. This method requires that assets acquired and liabilities assumed in a business combination be recognized at their respective estimated fair values as of the Acquisition Date. The excess of purchase consideration over the fair value of net tangible and identifiable intangible assets acquired was recorded as goodwill. The goodwill recorded from this acquisition represents business benefits the Company anticipates from the acquired workforce and expectation for expanded sales opportunities to foster further business growth. Due to the nature of the transaction, the goodwill associated with the acquisition is not deductible for tax purposes. The final purchase price allocation, completed in the fourth quarter of 2021, resulted in adjustments to certain assets and liabilities primarily related to Holdback amount, as discussed above, and a reduction to net deferred tax liabilities of approximately $1.3 million. The corresponding offset of measurement period acquisition adjustments to goodwill aggregated $1.7 million. ​ The following summarizes the final allocation of the purchase price for this acquisition, as of the date of the acquisition, is as follows (in thousands, except amortization period): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Amortization ​ Amount Period (Years) Allocation of Purchase Price: ​ Assets ​ Fair value of tangible assets (including cash of $5,900) ​ $ 8,298 Fair value of intangible assets: ​ Developed technology ​ 12,541 8 In-process R&D ​ 3,635 N/A Customer relationships ​ 1,967 10 Noncompetition agreements ​ 848 3 Tradenames and trademarks ​ 808 10 Goodwill ​ 11,830 N/A Total assets acquired ​ $ 39,927 Liabilities ​ Accounts payable and accrued expenses ​ $ 1,447 Deferred revenue ​ 375 Operating lease liabilities ​ 132 Deferred tax liabilities ​ 439 Total liabilities assumed ​ $ 2,393 Total purchase price allocation ​ $ 37,534 ​ The estimated fair value of accounts receivable acquired approximates the contractual value of $1.6 million. Pursuant to the merger agreement, the Company will also make payments to certain employees, subject to their continued employment with Cimetrix, through the second quarter of 2024. The estimated total cash payout is about $1.4 million at Acquisition Date and will be paid at various scheduled payout dates. This amount will be recognized as compensation expense over the period as services are rendered. As of December 31, 2022 and 2021, such accrued compensation recorded under “Accrued compensation and related benefits” in the accompanying Consolidated Balance Sheets amounted to $0.2 million and $0.5 million, respectively. Acquisition-Related Transaction Costs –

PROPERTY AND EQUIPMENT

PROPERTY AND EQUIPMENT	12 Months Ended
	Dec. 31, 2022
PROPERTY AND EQUIPMENT
PROPERTY AND EQUIPMENT	5. PROPERTY AND EQUIPMENT Property and equipment consist of (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, ​ 2022 2021 Computer equipment ​ $ 11,853 ​ $ 11,924 Software ​ 5,395 ​ 5,419 Furniture, fixtures and equipment ​ 2,484 ​ 2,506 Leasehold improvements ​ 6,467 ​ 6,272 Laboratory and other equipment ​ 4,431 ​ 3,981 Test equipment ​ 28,403 ​ 24,452 Construction-in-progress ​ 27,336 ​ 22,158 ​ ​ 86,369 ​ 76,712 Less: Accumulated depreciation and amortization ​ (46,195) ​ (41,417) Total ​ $ 40,174 ​ $ 35,295 ​ Test equipment mainly includes DFI™ systems and CV® systems assets at customer sites that are contributing to revenue. Among assets under construction, the construction-in-progress balance related to construction of DFI™ systems assets amounted to $22.2 million and $20.0 million as of December 31, 2022, and December 31, 2021, respectively. Depreciation and amortization expense for years ended December 31, 2022, 2021 and 2020 was $5.5 million, $6.2 million and $6.7 million, respectively. In 2021, the Company wrote down the value of its property and equipment by $3.2 million related to its first-generation of e-beam tools for DFI™ systems wherein carrying values may not be fully recoverable due to lack of market demand and future needs of our customers for these tools.

GOODWILL AND INTANGIBLE ASSETS

GOODWILL AND INTANGIBLE ASSETS	12 Months Ended
	Dec. 31, 2022
GOODWILL AND INTANGIBLE ASSETS
GOODWILL AND INTANGIBLE ASSETS	6. GOODWILL AND INTANGIBLE ASSETS The Company completed the acquisition of Cimetrix in the year ended December 31, 2020. Refer to Note 4 for additional information related to the goodwill and intangible assets added from this acquisition. As of December 31, 2022 and 2021, the carrying amount of goodwill was $14.1 million. The following table summarizes goodwill transaction for the years ended December 31, 2022, 2021 and 2020 (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year Ended December 31, ​ ​ 2022 2021 ​ 2020 Balance at beginning of year ​ $ 14,123 ​ $ 15,774 ​ $ 2,293 Addition ​ ​ — ​ ​ — ​ ​ 13,481 Measurement period acquisition adjustment (1) ​ — ​ (1,651) ​ — Balance at end of year ​ $ 14,123 ​ $ 14,123 ​ $ 15,774 ​ (1) Goodwill adjustment was recorded within the measurement period with a corresponding reduction in the Holdback Amount and reduction to net deferred tax liabilities. See Note 4, “Business Combination”. ​ Intangible assets balance was $18.1 million and $21.2 million as of December 31, 2022 and 2021, respectively. Intangible assets as of December 31, 2022 and 2021, consist of the following (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, 2022 ​ December 31, 2021 ​ ​ Amortization ​ Gross ​ ​ ​ ​ Net ​ Gross ​ ​ ​ ​ Net ​ ​ Period ​ Carrying ​ Accumulated ​ Carrying ​ Carrying ​ Accumulated ​ Carrying ​ ​ (Years) Amount Amortization Amount Amount Amortization Amount Acquired identifiable intangibles: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Customer relationships 1 - 10 ​ $ 9,407 ​ $ (6,684) ​ $ 2,723 ​ $ 9,407 ​ $ (6,041) ​ $ 3,366 Developed technology 4 - 9 ​ 33,635 ​ (19,647) ​ 13,988 ​ 33,635 ​ (17,250) ​ 16,385 Tradename and trademarks 2 - 10 ​ 1,598 ​ (918) ​ 680 ​ 1,598 ​ (812) ​ 786 Patent 6 - 10 ​ 2,100 ​ (1,696) ​ 404 ​ 1,800 ​ (1,640) ​ 160 Noncompetition agreements 3 ​ 848 ​ (588) ​ 260 ​ 848 ​ (306) ​ 542 Total ​ ​ ​ $ 47,588 ​ $ (29,533) ​ $ 18,055 ​ $ 47,288 ​ $ (26,049) ​ $ 21,239 ​ The weighted average amortization period for acquired identifiable intangible assets was 5.9 years as of December 31, 2022. The following table summarizes intangible assets amortization expense in the Consolidated Statements of Comprehensive Loss (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year Ended December 31, ​ 2022 2021 2020 Amortization of acquired technology included under Costs of Revenues ​ $ 2,214 ​ $ 2,079 ​ $ 705 Amortization of acquired intangible assets presented separately under Costs and Expenses ​ 1,270 ​ 1,255 ​ 741 Total amortization of acquired intangible assets ​ $ 3,484 ​ $ 3,334 ​ $ 1,446 ​ The Company expects annual amortization of acquired identifiable intangible assets to be as follows (in thousands): ​ ​ ​ ​ ​ Year Ending December 31, Amount 2023 ​ $ 3,491 2024 ​ 3,093 2025 ​ 2,928 2026 ​ 2,759 2027 ​ 2,606 2028 and thereafter ​ 3,178 Total future amortization expense ​ $ 18,055 ​ There were no impairment charges

LEASES

LEASES	12 Months Ended
	Dec. 31, 2022
LEASES
LEASES	7. LEASES In 2022, the Company early terminated an office lease contract. The termination of this lease reduced the Company’s operating lease right-of-use assets and lease liabilities by approximately $0.5 million and $0.6 million, respectively. The gain from the lease termination of approximately $0.1 million was recorded under selling, general and administrative expense in the accompanying Consolidated Statement of Comprehensive Loss for the year ended December 31, 2022. Lease expense was comprised of the following (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year Ended December 31, ​ 2022 2021 2020 Operating lease expense (1) ​ $ 1,457 ​ $ 1,860 ​ $ 1,828 Short-term lease and variable lease expense (2) ​ 1,032 ​ 822 ​ 545 Total lease expense ​ $ 2,489 ​ $ 2,682 ​ $ 2,373 ​ (1) Net of gain recognized upon lease termination of $0.1 million in the year ended December 31, 2022. (2) Leases with an initial term of 12 months or less are not recorded on the Consolidated Balance Sheets, and the Company recognizes lease expense for these leases on a straight-line basis over the lease term. Variable lease expense for the periods presented primarily included common area maintenance charges. Supplemental consolidated balance sheets information related to leases was as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, ​ 2022 2021 Weighted average remaining lease term under operating ROU leases (in years) ​ ​ 5.3 ​ ​ 5.7 ​ Weighted average discount rate for operating lease liabilities ​ 4.87 % ​ 5.25 % ​ Maturity of operating lease liabilities as of December 31, 2022, are as follows (in thousands): ​ ​ ​ ​ ​ Year Ending December 31, Amount (1) 2023 ​ $ 1,570 2024 ​ 1,633 2025 ​ 1,547 2026 ​ 1,357 2027 ​ 1,294 2028 and thereafter ​ ​ 991 Total future minimum lease payments ​ $ 8,392 Less: Interest (2) ​ (1,048) Present value of future minimum lease payments under operating lease liabilities (3) ​ $ 7,344 (1) As of December 31, 2022, the total operating lease liability includes $0.9 million related to an option to extend a lease term that is reasonably certain to be exercised . (2) Calculated using incremental borrowing interest rate for each lease. (3) Includes the current portion of operating lease liabilities of $1.4 million as of December 31, 2022.

COMMITMENTS AND CONTINGENCIES

COMMITMENTS AND CONTINGENCIES	12 Months Ended
	Dec. 31, 2022
COMMITMENTS AND CONTINGENCIES
COMMITMENTS AND CONTINGENCIES	8. COMMITMENTS AND CONTINGENCIES Strategic Partnership with Advantest See Note 3 for the discussion about the Company’s commitments under the strategic partnership with Advantest. Operating Leases Refer to Note 7, “Leases”, for the discussion about the Company’s lease commitments. Indemnifications The Company generally provides a warranty to its customers that its software will perform substantially in accordance with documented specifications typically for a period of 90 days following delivery of its products. The Company also indemnifies certain customers from third-party claims of intellectual property infringement relating to the use of its products. Historically, costs related to these guarantees have not been significant. The Company is unable to estimate the maximum potential impact of these guarantees on its future results of operations. Purchase obligations The Company has purchase obligations with certain suppliers for the purchase of goods and services entered in the ordinary course of business. As of December 31, 2022, total outstanding purchase obligations were $30.4 million, the majority of which due within the next 24 months. Indemnification of Officers and Directors As permitted by the Delaware general corporation law, the Company has included a provision in its certificate of incorporation to eliminate the personal liability of its officers and directors for monetary damages for breach or alleged breach of their fiduciary duties as officers or directors, other than in cases of fraud or other willful misconduct. In addition, the Bylaws of the Company provide that the Company is required to indemnify its officers and directors even when indemnification would otherwise be discretionary, and the Company is required to advance expenses to its officers and directors as incurred in connection with proceedings against them for which they may be indemnified. The Company has entered into indemnification agreements with its officers and directors containing provisions that are in some respects broader than the specific indemnification provisions contained in the Delaware general corporation law. The indemnification agreements require the Company to indemnify its officers and directors against liabilities that may arise by reason of their status or service as officers and directors other than for liabilities arising from willful misconduct of a culpable nature, to advance their expenses incurred as a result of any proceeding against them as to which they could be indemnified, and to obtain directors’ and officers’ insurance if available on reasonable terms. The Company has obtained directors’ and officers’ liability insurance in amounts comparable to other companies of the Company’s size and in the Company’s industry. Since a maximum obligation of the Company is not explicitly stated in the Company’s Bylaws or in its indemnification agreements and will depend on the facts and circumstances that arise out of any future claims, the overall maximum amount of the obligations cannot be reasonably estimated. Litigation From time to time, the Company is subject to various claims and legal proceedings that arise in the ordinary course of business. The Company accrues for losses related to litigation when a potential loss is probable, and the loss can be reasonably estimated in accordance with FASB requirements. As of December 31, 2022, except as disclosed below, the Company was not party to any material legal proceedings for which a loss was probable or an amount was accrued. On May 6, 2020, the Company initiated an arbitration proceeding with the Hong Kong International Arbitration Center against SMIC New Technology Research & Development (Shanghai) Corporation (“SMIC”) due to SMIC’s failure to pay fees due to PDF under a series of contracts. The Company seeks to recover the unpaid fees, a declaration requiring SMIC to pay fees under the contracts in the future (or a lump sum payment to end the contract), and costs associated with bringing the arbitration proceeding. SMIC denies liability and an arbitration hearing was held in February 2023. The decision is expected within approximately three to six months.

STOCKHOLDERS' EQUITY

STOCKHOLDERS' EQUITY	12 Months Ended
	Dec. 31, 2022
STOCKHOLDERS EQUITY
STOCKHOLDERS' EQUITY	9. STOCKHOLDERS’ EQUITY Issuance of Common Stock On July 30, 2020, the Company issued 3,306,924 shares of common stock, at a purchase price of $19.7085 per share, for aggregate gross proceeds of $65.2 million pursuant to a Securities Purchase Agreement with Advantest dated July 29, 2020. Issuance costs related to this private placement aggregated $0.1 million. See Note 3, “Strategic Partnership Agreement with Advantest and Related Party Transactions”, for further details. Stock Repurchase Program On May 28, 2020, the Company’s 2018 stock repurchase program (the “2018 Program”) that was originally adopted on May 29, 2018, expired. As of May 28, 2020, approximately 786,000 shares had been repurchased at an average price of $12.43 per share, for a total price of $9.8 million under the 2018 Program. On June 4, 2020, the Company’s Board of Directors adopted a stock repurchase program (the “2020 Program”) to repurchase up to $25.0 million of the Company’s common stock both on the open market and in privately negotiated transactions, including through Rule 10b5-1 plans, over the next two years. During the year ended December 31, 2022, the Company repurchased 218,858 shares under the 2020 Program at an average price of $26.40 per share for an aggregate total price of $5.8 million. During the year ended December 31, 2021, the Company repurchased 251,212 shares under the 2020 Program at an average price of $18.01 per share for an aggregate total price of $4.5 million. In total, 470,070 shares were repurchased under the 2020 Program at an average price of $21.91 per share, for an aggregate total price of $10.3 million. On April 11, 2022, the Board of Directors terminated the 2020 Program, and adopted a new program (the “2022 Program”) to repurchase up to $35.0 million of the Company’s common stock both on the open market and in privately negotiated transactions, from time to time, over the next two years. During the year ended December 31, 2022, the Company repurchased 714,600 shares under the 2022 Program at an average price of $23.36 per share for an aggregate total price of $16.7 million.

EMPLOYEE BENEFIT PLANS

EMPLOYEE BENEFIT PLANS	12 Months Ended
	Dec. 31, 2022
EMPLOYEE BENEFIT PLANS
EMPLOYEE BENEFIT PLANS	10. EMPLOYEE BENEFIT PLANS On December 31, 2022, the Company had the following stock-based compensation plans: Employee Stock Purchase Plans In July 2001, the Company’s stockholders initially approved the 2001 Employee Stock Purchase Plan, which was subsequently amended and restated in 2010 (as amended, the “2010 Purchase Plan”) to extend the term of the plan through May 17, 2020. Under the 2010 Purchase Plan, eligible employees can contribute up to 10% of their compensation, as defined in the Purchase Plan, towards the purchase of shares of PDF common stock at a price of 85% of the lower of the fair market value at the beginning of the offering period or the end of the purchase period. The 2010 Purchase Plan provided for twenty-four-month offering periods with four six-month The Company estimated the fair value of purchase rights granted under the Employee Purchase Plans during the period using the Black-Scholes-Merton option-pricing model with the following weighted average assumptions, resulting in the following weighted average fair values: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ 2021 Purchase Plan ​ ​ 2010 Purchase Plan ​ ​ ​ Year Ended December 31, ​ ​ Year Ended December 31, ​ ​ Year Ended December 31, ​ ​ ​ 2022 ​ 2021 ​ 2020 Expected life (in years) ​ ​ 1.25 ​ ​ 1.25 ​ ​ 1.25 Volatility ​ ​ 48.73 % ​ ​ 48.00 % ​ ​ 34.25 % Risk-free interest rate ​ ​ 2.75 % ​ ​ 0.11 % ​ ​ 1.43 % Expected dividend ​ ​ — ​ ​ — ​ ​ — Weighted average fair value of purchase rights granted during the period ​ $ 10.00 ​ ​ $ 6.71 ​ ​ $ 4.83 ​ ​ During the year ended December 31, 2022, a total of 182,083 shares were issued under the 2021 Purchase Plan, at a weighted-average purchase price of $16.15 per share. During the years ended December 31, 2022, 2021 and 2020, a total of 5,203, 108,623 and 183,078 shares, respectively, were issued under the 2010 Purchase Plan, at a weighted-average purchase price of $13.40 per share, $9.53 per share and $9.12 per share, respectively. As of December 31, 2022, unrecognized compensation cost related to the 2021 Purchase Plan was $1.1 million. This estimated unrecognized cost is expected to be recognized over a weighted average period of 1.0 year. There was no unrecognized compensation cost related to the 2010 Purchase Plan as of December 31, 2022. As of December 31, 2022, 817,917 shares were available for future issuance under the 2021 Purchase Plan. Stock Incentive Plans On November 16, 2011, the Company’s stockholders initially approved the 2011 Stock Incentive Plan, which has been amended and restated and approved by the Company’s stockholders a number of times since then (as amended, the “2011 Plan”). Under the 2011 Plan, the Company may award stock options, stock appreciation rights (“SARs”), stock grants or stock units covering shares of the Company’s common stock to employees, directors, non-employee directors and contractors. The aggregate number of shares reserved for awards under the 2011 Plan is 12,800,000 shares, plus up to 3,500,000 shares previously issued under the 2001 Stock Plan adopted by the Company in 2001, which expired in 2011 (the “2001 Plan”) that are either (i) forfeited or (ii) repurchased by the Company or are shares subject to awards previously issued under the 2001 Plan that expire or that terminate without having been exercised or settled in full on or after November 16, 2011. In case of awards other than options or SARs, the aggregate number of shares reserved under the 2011 Plan will be decreased at a rate of 1.33 shares issued pursuant to such awards. The exercise price for stock options must generally be at prices no less than the fair market value at the date of grant. Stock options generally expire ten As of December 31, 2022, 13.3 million shares of common stock were reserved to cover stock-based awards under the 2011 Plan, of which 3.5 million shares were available for future grant. The number of shares reserved and available under the 2011 Plan includes 0.5 million shares that were subject to awards previously made under the 2001 Plan and were forfeited, expired or repurchased by the Company after the adoption of the 2011 Plan through December 31, 2022. As of December 31, 2022, there were no outstanding awards that had been granted outside of the 2011 or 2001 Plans (collectively, the “Stock Plans”). The Company has elected to use the Black-Scholes-Merton option-pricing model, which incorporates various assumptions including volatility, expected life, interest rate and expected dividend. The expected volatility is based on the historical volatility of the Company’s common stock over the most recent period commensurate with the estimated expected life of the Company’s stock options. The expected life of an award is based on historical experience and on the terms and conditions of the stock awards granted to employees. The interest rate assumption is based upon observed Treasury yield curve rates appropriate for the expected life of the Company’s stock options. ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year Ended December 31, ​ ​ 2022 2021 2020 Expected life (in years) ​ ​ — ​ ​ — ​ ​ 4.45 ​ Volatility ​ — % ​ — % ​ 40.90 % Risk-free interest rate ​ — % ​ — % ​ 0.60 % Expected dividend ​ — ​ — ​ ​ — ​ Weighted average fair value per share of options granted during the period ​ $ — ​ $ — ​ $ 5.75 ​ ​ No stock options were granted during the years ended December 31, 2022 and 2021. Stock-based compensation is estimated at the grant date based on the award’s fair value and is recognized on a straight-line basis over the vesting periods, generally four Stock-based compensation expenses related to the Company’s stock plans and employee stock purchase plans were allocated as follows (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year Ended December 31, ​ 2022 2021 2020 Costs of revenues ​ $ 2,974 ​ $ 2,563 ​ $ 3,454 Research and development ​ 9,391 ​ 5,515 ​ 4,800 Selling, general and administrative ​ 7,284 ​ 4,853 ​ 4,209 Stock-based compensation expenses ​ $ 19,649 ​ $ 12,931 ​ $ 12,463 ​ The stock-based compensation expense in the table above includes immaterial expense or credit adjustments related to cash-settled SARs granted to certain employees. The Company accounted for these awards as liability awards and the amount was included in accrued compensation and related benefits. SARs were fully exercised in the third quarter of 2020. Stock-based compensation capitalized in the capitalized software development costs included in property and equipment, net, was nil, nil and approximately $0.2 million for the years ended December 31, 2022, 2021 and 2020, respectively. Additional information with respect to options under the Plans is as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Outstanding Options ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted ​ ​ ​ ​ ​ ​ ​ Weighted ​ Average ​ ​ ​ ​ ​ ​ ​ Average ​ Remaining ​ Aggregate ​ ​ Number of ​ Exercise ​ Contractual ​ Intrinsic ​ ​ Options ​ Price ​ Term ​ Value ​ (in thousands) per Share (Years) (in thousands) Outstanding, January 1, 2020 745 ​ $ 10.64 ​ Granted (weighted average fair value of $5.75 per share) 24 ​ $ 16.72 ​ Exercised (246) ​ $ 10.46 ​ Canceled (57) ​ $ 11.65 ​ Expired (10) ​ $ 10.06 ​ Outstanding, December 31, 2020 456 ​ $ 10.95 ​ Granted — ​ $ — ​ Exercised (216) ​ $ 8.90 ​ Canceled (10) ​ $ 15.56 ​ Expired (4) ​ $ 6.90 ​ Outstanding, December 31, 2021 226 ​ $ 12.78 ​ Granted — ​ ​ — ​ Exercised (150) ​ ​ 11.27 ​ Canceled (6) ​ ​ 13.52 ​ Expired (2) ​ ​ 8.79 ​ Outstanding, December 31, 2022 68 ​ $ 16.11 4.89 ​ $ 847 Vested and expected to vest, December 31, 2022 68 ​ $ 16.11 4.87 ​ $ 842 Exercisable, December 31, 2022 57 ​ $ 16.07 4.46 ​ $ 706 ​ The aggregate intrinsic value in the table above represents the total intrinsic value based on the Company’s closing stock price of $28.52 as of December 31, 2022, which would have been received by the option holders had all option holders exercised their options as of that date. The total intrinsic value of options exercised during the years ended December 31, 2022, 2021 and 2020 was $2.3 million, $3.0 million and $2.2 million, respectively. As of December 31, 2022, there was $0.1 million of total unrecognized compensation cost, net of forfeitures, related to unvested stock options. That cost is expected to be recognized over a weighted average period of 1.0 years. The total fair value of options vested during the year ended December 31, 2022, was $0.1 million. Nonvested shares (restricted stock units) were as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted ​ ​ ​ ​ Average Grant ​ ​ Shares ​ Date Fair Value ​ (in thousands) Per Share Nonvested, January 1, 2020 1,887 ​ $ 12.30 Granted 890 ​ $ 21.31 Vested (867) ​ $ 13.25 Forfeited (163) ​ $ 13.23 Nonvested, December 31, 2020 1,747 ​ $ 16.33 Granted 977 ​ $ 19.43 Vested (689) ​ $ 15.23 Forfeited (163) ​ $ 17.63 Nonvested, December 31, 2021 1,872 ​ $ 18.24 Granted 1,210 ​ $ 23.23 Vested (862) ​ $ 17.57 Forfeited (96) ​ $ 19.71 Nonvested, December 31, 2022 2,124 ​ $ 21.29 ​ As of December 31, 2022, there was $32.7 million of total unrecognized compensation cost related to restricted stock units. That cost is expected to be recognized over a weighted average period of 2.6 years. Restricted stock units do not have rights to dividends prior to vesting. 401(k) Savings Plan The Company sponsors a 401(k) Retirement Savings Plan (the “401(k) Plan”) covering substantially all of its US employees. The Company’s 401(k) Plan is a defined contribution plan with a 401(k) salary deferral arrangement qualified under appropriate provisions of the Internal Revenue Code (the “Code”) and applicable state laws. Under the 401(k) Plan, eligible employees may make pre-tax salary or after-tax contributions up to 60% of annual compensation, as defined by the 401(k) Plan. In addition, participants who have reached the age of 50 can elect to withhold additional catch-up contributions subject to the Code and the 401(k) Plan limits. Participants may also contribute amounts representing distributions from other qualified plans (rollovers). The Company may make discretionary matching contributions. In fiscal 2022, the Company matches from 50% to 100% of each employee’s contribution up to a maximum of 4% of the employee’s total eligible earnings. The Company’s matching contributions to the 401(k) Plan aggregated $1.6 million for the year ended December 31, 2022. No discretionary Company contributions have been made to the Plan through December 31, 2021.

INCOME TAXES

INCOME TAXES	12 Months Ended
	Dec. 31, 2022
INCOME TAXES
INCOME TAXES	11. INCOME TAXES During the years ended December 31, 2022, 2021 and 2020, loss before income taxes from U.S. operations was ($1.2) million, ($19.7) million and ($18.4) million, respectively, and income before income taxes from foreign operations was $1.7 million, $1.4 million and $0.3 million, respectively. ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year Ended December 31, ​ 2022 2021 ​ 2020 ​ ​ (In thousands) U.S. ​ ​ ​ ​ ​ ​ ​ Current ​ $ 1,210 ​ $ (67) ​ $ (1,325) Deferred ​ 13 ​ 1,318 ​ 21,056 Foreign ​ ​ ​ Current ​ 577 ​ 237 ​ 238 Withholding ​ 2,111 ​ 1,591 ​ 2,392 Deferred ​ (12) ​ 92 ​ (58) Total income tax expense ​ $ 3,899 ​ $ 3,171 ​ $ 22,303 ​ The income tax expense differs from the amount estimated by applying the statutory federal income tax rate (21% for 2022, 2021 and 2020) for the following reasons (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year Ended December 31, ​ 2022 2021 2020 Federal statutory tax expense ​ $ 106 ​ $ (3,847) ​ $ (3,793) State tax provision ​ 949 ​ 239 ​ 703 Stock compensation expense ​ (898) ​ (499) ​ (602) Tax credits ​ (2,877) ​ (2,676) ​ (3,488) Foreign tax, net ​ 2,195 ​ 1,653 ​ 2,443 Foreign-derived intangible income (FDII) deduction ​ ​ (830) ​ ​ — ​ ​ — Change in valuation allowance ​ 5,122 ​ 8,099 ​ 29,034 Unrealized tax benefit reserve changes ​ ​ 136 ​ ​ (151) ​ ​ — Business combination costs ​ ​ — ​ ​ — ​ ​ 356 Tax law changes ​ — ​ — ​ (2,237) Other ​ (4) ​ 353 ​ (113) Total income tax expense ​ $ 3,899 ​ $ 3,171 ​ $ 22,303 ​ As of December 31, 2022, the Company had Federal and California net operating loss carry-forwards (“NOLs”) of approximately $9.9 million and $11.2 million, respectively. Some of the Federal NOLs, acquired as part of a past acquisition, have expirations at the end of this fiscal year and onwards, and the California NOLs begin expiring in 2028 onwards. As of December 31, 2022, the Company had federal and state research and experimental and other tax credit (“R&D credits”) carry-forwards of approximately $21.8 million and $22.8 million, respectively. The federal credits began to expire in 2022, while the California credits have no expiration. The extent to which the federal and state credit carry forwards can be used to offset future tax liabilities, respectively, may be limited, depending on the extent of ownership changes within any three-year period as provided in the Tax Reform Act of 1986 and the California Conformity Act of 1987. The Company assesses its deferred tax assets for recoverability on a regular basis, and where applicable, a valuation allowance is recorded to reduce the total deferred tax asset to an amount that will, more likely than not, be realized in the future. Based on all available evidence, both positive and negative, the Company determined a full valuation allowance was still appropriate for its federal and state net deferred tax assets (DTAs) at December 31, 2022, primarily driven by a cumulative loss incurred over the 12-quarter period ended December 31, 2022 and the likelihood that the Company will not utilize tax attributes before they begin to expire. The valuation allowance was approximately $59.2 million and $51.6 million as of December 31, 2022 and 2021, respectively. The increase in the valuation allowance from December 31, 2021 to December 31, 2022 was primarily driven by a net increase in timing differences relating to deferred revenue, accrued bonus and credits generated in the current year which require a valuation allowance. Management will continue to evaluate the need for a valuation allowance and may change its conclusion in a future period based on any change in facts (e.g. 12-quarter cumulative profit, significant new revenue, and other relevant factors). If the Company concludes that it is more likely than not to utilize some or all of its US DTAs, it will release some or all of its valuation allowance and our tax provision will decrease in the period in which we make such determination. Net deferred tax assets, after the US valuation allowance, was immaterial as of December 31, 2022, and December 31, 2021. The components of the net deferred tax assets are comprised of (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, ​ 2022 2021 Deferred tax assets ​ ​ Net operating loss carry forward ​ $ 3,861 ​ $ 13,149 Research and development and other credit carry forward ​ 28,046 ​ 26,591 Foreign tax credit carry forward ​ 11,764 ​ 11,010 Capitalized research and experimental expenses ​ ​ 10,069 ​ ​ — Accruals deductible in different periods ​ 7,713 ​ 3,362 Leases ​ 1,623 ​ 1,472 Stock-based compensation ​ 1,948 ​ 1,442 Total deferred tax assets ​ 65,024 ​ 57,026 Less: valuation allowance ​ (59,215) ​ (51,586) Deferred tax assets, net of valuation allowance ​ $ 5,809 ​ $ 5,440 ​ ​ ​ ​ ​ ​ ​ Deferred tax liabilities ​ ​ Property and equipment, net ​ (540) ​ 178 Operating lease right-of-use assets ​ (1,635) ​ (1,472) Intangible assets ​ (3,617) ​ (4,129) Deferred tax liabilities ​ $ (5,792) ​ $ (5,423) ​ ​ ​ ​ ​ ​ ​ Net deferred tax assets ​ $ 17 ​ $ 17 ​ In accordance with the accounting standard relating to accounting for uncertain tax positions, the Company classifies its liabilities for income tax exposures as long-term. The Company includes interest and penalties related to unrecognized tax benefits within the Company’s income tax provision. As of December 31, 2022, 2021 and 2020, the Company had accrued interest and penalties related to unrecognized tax benefits of $0.7 million, $0.7 million, and $0.8 million, respectively. In the years ended December 31, 2022, 2021 and 2020, the Company recognized (reversal of) charges for interest and penalties related to unrecognized tax benefits of ($61,000), ($89,000) and $33,000 respectively, in the Consolidated Statements of Comprehensive Loss. The Company’s total amount of unrecognized tax benefits, excluding interest and penalties, as of December 31, 2022 was $15.1 million, of which $2.0 million, if recognized, would impact the Company’s effective tax rate. As of December 31, 2022, the Company has recorded unrecognized tax benefits of $2.6 million, including interest and penalties of $0.7 million, as long-term income taxes payable in its Consolidated Balance Sheet. The remaining $13.2 million has been recorded within our deferred tax assets, which is subject to a full valuation allowance. The Company does not expect the change in unrecognized tax benefits over the next twelve months to materially impact its results of operations and financial position. A reconciliation of the beginning and ending amount of unrecognized tax benefits is as follows (in thousands): ​ ​ ​ ​ ​ ​ Amount Gross unrecognized tax benefits, January 1, 2020 ​ $ 13,615 Increases in tax positions for current year ​ 1,024 Increases in tax positions for prior years ​ 71 Lapse in statute of limitations ​ (410) Gross unrecognized tax benefits, December 31, 2020 ​ 14,300 Increases in tax positions for current year ​ 853 Increases in tax positions for prior years ​ 1 Lapse in statute of limitations ​ (411) Gross unrecognized tax benefits, December 31, 2021 ​ 14,743 Increases in tax positions for current year ​ 988 Increases in tax positions for prior years ​ — Lapse in statute of limitations ​ (622) Gross unrecognized tax benefits, December 31, 2022 ​ $ 15,109 ​ The Company does not provide deferred taxes on undistributed earnings of its foreign subsidiaries as it intends to indefinitely reinvest those earnings. The Company conducts business globally and, as a result, files numerous consolidated and separate income tax returns in the U.S. federal, various state and foreign jurisdictions. For U.S. federal and California income tax purposes, the statute of limitations currently remains open for the years ended 2019 to present and 2018 to present, respectively. In addition, due to NOL carryback claims, the tax years 2013 through 2015 may be subject to federal examination and all of the net operating loss and research and development credit carryforwards that may be utilized in future years may be subject to federal and state examination. The Company is not currently under income tax examinations in the US or in any other of its major foreign subsidiaries’ jurisdictions. Valuation allowance for deferred tax assets is summarized (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Balance at ​ Charged to ​ Deductions/ ​ Balance at ​ ​ Beginning ​ Costs and ​ Write-offs of ​ End of ​ of Period Expenses Accounts Period Valuation allowance for deferred tax assets ​ ​ ​ ​ 2022 ​ $ 51,586 ​ $ 7,629 ​ $ — ​ $ 59,215 2021 ​ $ 41,859 ​ $ 9,727 ​ $ — ​ $ 51,586 2020 ​ $ 10,486 ​ $ 31,373 ​ $ — ​ $ 41,859 ​ ​ ​

NET LOSS PER SHARE

NET LOSS PER SHARE	12 Months Ended
	Dec. 31, 2022
NET LOSS PER SHARE
NET LOSS PER SHARE	12. NET LOSS PER SHARE Basic net loss per share is computed by dividing net loss by weighted average number of common shares outstanding for the period (excluding outstanding stock options and shares subject to repurchase). Diluted net loss per share is computed using the weighted-average number of common shares outstanding for the period plus the potential effect of dilutive securities which are convertible into common shares (using the treasury stock method), except in cases in which the effect would be anti-dilutive. The following is a reconciliation of the numerators and denominators used in computing basic and diluted net loss per share (in thousands except per share amount): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year Ended December 31, ​ 2022 2021 2020 Numerator: ​ ​ ​ Net loss ​ $ (3,429) ​ $ (21,488) ​ $ (40,363) Denominator: ​ ​ ​ Basic weighted-average shares outstanding ​ 37,309 ​ 37,138 ​ 34,458 Effect of dilutive options and restricted stock units ​ — ​ — ​ — Diluted weighted-average shares outstanding ​ 37,309 ​ 37,138 ​ 34,458 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Net loss per share, basic and diluted ​ $ (0.09) ​ $ (0.58) ​ $ (1.17) ​ For the years ended December 31, 2022, 2021, and 2020, because the Company was in a loss position, basic net loss per share is the same as diluted net loss per share as the inclusion of the potential common shares would have been anti-dilutive. The following table sets forth potential shares of common stock that are not included in the diluted net loss per share calculation above because to do so would be anti-dilutive for the periods indicated (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year Ended December 31, ​ 2022 2021 2020 Outstanding options 56 170 332 Non-vested restricted stock units 787 ​ 968 ​ 921 Employee Stock Purchase Plan 84 ​ 33 ​ 160 Total 927 ​ 1,171 ​ 1,413 ​

CUSTOMER AND GEOGRAPHIC INFORMA

CUSTOMER AND GEOGRAPHIC INFORMATION	12 Months Ended
	Dec. 31, 2022
CUSTOMER AND GEOGRAPHIC INFORMATION
CUSTOMER AND GEOGRAPHIC INFORMATION	13. CUSTOMER AND GEOGRAPHIC INFORMATION Operating segments are defined as components of an enterprise about which separate financial information is available that is evaluated regularly by the chief operating decision maker, or group, in deciding how to allocate resources and in assessing performance. The Company’s chief operating decision maker, the chief executive officer, reviews discrete financial information presented on a consolidated basis for purposes of regularly making operating decisions, allocation of resources, and assessing financial performance. Accordingly, the Company considers itself to be in one operating and reporting Revenues from individual customers that are approximately 10% or more of the Company’s consolidated total revenues are as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year Ended December 31, Customer 2022 ​ 2021 ​ 2020 A ​ 31 % ​ 17 % ​ * % B ​ 10 % ​ * % ​ * % D ​ * % ​ 10 % ​ * % E ​ * % ​ * % ​ 23 % ​ Gross accounts receivable balances (including amounts that are unbilled) from individual customers that are approximately 10% or more of the Company’s gross accounts receivable balance are as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, Customer 2022 2021 A 29 % 29 % B 12 % 15 % C ​ 12 % * % * represents less than 10% Revenues from customers by geographic area based on the location of the customers’ work sites are as follows (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year Ended December 31, ​ ​ 2022 ​ ​ 2021 ​ 2020 ​ ​ ​ ​ ​ Percentage ​ ​ ​ ​ ​ Percentage ​ ​ ​ ​ Percentage ​ Revenues of Revenues ​ Revenues of Revenues ​ Revenues of Revenues United States ​ $ 73,625 50 % ​ $ 50,374 ​ 45 % ​ $ 36,723 ​ 42 % China ​ 24,494 16 ​ ​ 14,267 ​ 13 ​ ​ 13,776 ​ 16 ​ Japan ​ ​ 13,916 ​ 9 ​ ​ ​ 11,097 ​ 10 ​ ​ ​ 4,762 ​ 5 ​ Rest of the world ​ 36,514 25 ​ ​ 35,322 ​ 32 ​ ​ 32,785 ​ 37 ​ Total revenue ​ $ 148,549 100 % ​ $ 111,060 100 % ​ $ 88,046 100 % ​ Long-lived assets, net by geographic area is as follows (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, ​ 2022 2021 United States (1) ​ $ 44,730 ​ $ 39,158 Rest of the world ​ 1,446 ​ 1,545 Total long-lived assets, net ​ $ 46,176 ​ $ 40,703 ​ ​ ​ ​ ​ ​ (1) Includes assets deployed at customer sites which could be outside the U.S.

FINANCIAL INSTRUMENTS

FINANCIAL INSTRUMENTS	12 Months Ended
	Dec. 31, 2022
FINANCIAL INSTRUMENTS
FINANCIAL INSTRUMENTS	14. FAIR VALUE MEASUREMENTS Fair value is the exit price, or the amount that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants as of the measurement date. The multiple assumptions used to value financial instruments are referred to as inputs, and a hierarchy for inputs used in measuring fair value is established, that maximizes the use of observable inputs and minimizes the use of unobservable inputs by requiring that the most observable inputs be used when available. Observable inputs reflect assumptions market participants would use in pricing an asset or liability based on market data obtained from independent sources while unobservable inputs reflect a reporting entity’s pricing based upon its own market assumptions. These inputs are ranked according to a fair value hierarchy that prioritizes the inputs to valuation techniques used to measure fair value into three broad levels. ​ Level 1 - Inputs are quoted prices in active markets for identical assets or liabilities. Level 2 - Inputs are quoted prices for similar assets or liabilities in an active market, quoted prices for identical or similar assets or liabilities in markets that are not active, inputs other than quoted prices that are observable and market-corroborated inputs which are derived principally from or corroborated by observable market data. Level 3 - Inputs are derived from valuation techniques in which one or more significant inputs or value drivers are unobservable. ​ The following table represents the Company’s assets measured at fair value on a recurring basis as of December 31, 2022 and the basis for that measurement (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Fair Value Measurements Using ​ ​ ​ ​ ​ Quoted ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Prices in ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Active ​ Significant ​ ​ ​ ​ ​ ​ ​ ​ Markets for ​ Other ​ ​ ​ ​ ​ ​ ​ ​ Identical ​ Observable ​ Significant ​ ​ December 31, ​ Assets ​ Inputs ​ Unobservable Assets 2022 (Level 1) (Level 2) Inputs (Level 3) Cash equivalents ​ ​ ​ ​ Money market mutual funds ​ $ 75,738 ​ $ 75,738 ​ $ — ​ $ — U.S. Government securities (1) ​ ​ 1,990 ​ ​ 1,990 ​ ​ — ​ ​ — Short-term investments (available-for-sale debt securities) ​ ​ ​ ​ U.S. Government securities (1) ​ 19,557 ​ 19,557 ​ — ​ — Total ​ $ 97,285 ​ $ 97,285 ​ $ — ​ $ — ​ The following table represents the Company’s assets measured at fair value on a recurring basis as of December 31, 2021 and the basis for that measurement (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Fair Value Measurements Using ​ ​ ​ ​ ​ Quoted ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Prices in ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Active ​ Significant ​ ​ ​ ​ ​ ​ ​ ​ Markets for ​ Other ​ Significant ​ ​ ​ ​ ​ Identical ​ Observable ​ Unobservable ​ ​ December 31, ​ Assets ​ Inputs ​ Inputs Assets 2021 (Level 1) (Level 2) (Level 3) Cash equivalents ​ ​ ​ ​ Money market mutual funds ​ $ 12,474 ​ $ 12,474 ​ $ — ​ $ — Short-term investments (available-for-sale debt securities) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ U.S. Government securities (1) ​ ​ 112,542 ​ ​ 112,542 ​ ​ — ​ ​ — Total ​ $ 125,016 ​ $ 125,016 ​ $ — ​ $ — (1) The carrying amount of the Company’s investments in U.S. Government securities approximate fair value due to their short-term maturities, and there have been no events or changes in circumstances that would have had a significant effect on the fair value of these securities at December 31, 2022 and 2021. From time to time, the Company enters into foreign currency forward contracts to reduce the exposure to foreign currency exchange rate fluctuations on certain foreign currency denominated monetary assets and liabilities, primarily on third-party accounts payables and intercompany balances. The primary objective of the Company’s hedging program is to reduce volatility of earnings related to foreign currency exchange rate fluctuations. The counterparty to these foreign currency forward contracts is a financial institution that the Company believes is creditworthy, and therefore, the Company believes the credit risk of counterparty nonperformance is not significant. These foreign currency forward contracts are not designated for hedge accounting treatment. Therefore, the change in fair value of these contracts is recorded into earnings as a component of other expense (income), net, and offsets the change in fair value of the foreign currency denominated assets and liabilities, which is also recorded in other expense (income), net in the Company’s Consolidated Statements of Comprehensive Loss. There was no realized gain or loss

SELECTED QUARTERLY FINANCIAL DA

SELECTED QUARTERLY FINANCIAL DATA (UNAUDITED)	12 Months Ended
	Dec. 31, 2022
SELECTED QUARTERLY FINANCIAL DATA (UNAUDITED)
SELECTED QUARTERLY FINANCIAL DATA (UNAUDITED)	15. SELECTED QUARTERLY FINANCIAL DATA (UNAUDITED) The following is a summary of the Company’s quarterly consolidated results of operations (unaudited) for the fiscal years ended December 31, 2022 and 2021. ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year Ended December 31, 2022 ​ Q1 Q2 Q3 Q4 ​ ​ (In thousands, except for per share amounts) Total revenues ​ $ 33,498 ​ $ 34,668 ​ $ 39,860 ​ $ 40,523 Costs of revenues ​ $ 11,529 ​ $ 12,042 ​ $ 12,545 ​ $ 11,791 Net income (loss) ​ $ (4,150) ​ $ (1,147) ​ $ 1,385 ​ $ 483 Net income (loss) per share: ​ ​ ​ ​ Basic and diluted ​ $ (0.11) ​ $ (0.03) ​ $ 0.04 ​ $ 0.01 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year Ended December 31, 2021 ​ Q1 Q2 Q3 Q4 ​ ​ (In thousands, except for per share amounts) Total revenues ​ $ 24,200 ​ $ 27,419 ​ $ 29,555 ​ $ 29,886 Costs of revenues ​ $ 10,663 ​ $ 10,785 ​ $ 11,070 ​ $ 11,675 Net loss ​ $ (7,597) ​ $ (4,484) ​ $ (2,407) ​ $ (7,000) Net loss per share: ​ ​ ​ ​ Basic and diluted ​ $ (0.21) ​ $ (0.12) ​ $ (0.06) ​ $ (0.19) ​

SIGNIFICANT ACCOUNTING POLICIES

SIGNIFICANT ACCOUNTING POLICIES (Policies)	12 Months Ended
	Dec. 31, 2022
BASIS OF PRESENTATION AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES
Basis of Presentation, Policy	Basis of Presentation The consolidated financial statements include the accounts of the Company and its wholly-owned subsidiaries after the elimination of all significant intercompany balances and transactions.
Use of Estimates, Policy	Use of Estimates The preparation of financial statements in conformity with generally accepted accounting principles in the United States (“U.S. GAAP”) requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, the disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenues and expenses during the reporting period. Significant estimates in these financial statements include revenue recognition, the estimated useful lives of property and equipment and intangible assets, assumptions made in analysis of allowance for doubtful accounts, fair values of assets acquired and liabilities assumed in business combinations, impairment of goodwill and long-lived assets, valuation for deferred tax assets, and accounting for lease obligations, stock-based compensation expense, and income tax uncertainties and contingencies. Actual results could differ from those estimates and may result in material effects on the Company’s operating results and financial position. The global COVID-19 pandemic has impacted the operations and purchasing decisions of companies worldwide. As of the date of issuance of the consolidated financial statements, the Company is not aware of any specific event or circumstance relating to COVID-19 that would require updates to the Company’s estimates and judgments or revisions to the carrying value of its assets or liabilities. These estimates may change, as new events occur and additional information is obtained, and are recognized in the consolidated financial statements as soon as they become known. Actual results could differ from those estimates and any such differences may be material to the financial statements.
Concentration of Credit Risk, Policy	Concentration of Credit Risk Financial instruments that potentially expose the Company to concentrations of credit risk consist primarily of cash and cash equivalents, short-term investments, and accounts receivable. The Company maintains its cash and cash equivalents and short-term investments with what it considers high credit quality financial institutions. The Company primarily sells its products and services to companies in Asia, Europe and North America within the semiconductor industry. As of December 31, 2022, three customers accounted for 53% of the Company’s gross accounts receivable and two customers accounted for 41% of the Company’s total revenues for 2022. As of December 31, 2021, two customers accounted for 44% of the Company’s gross accounts receivable and two customers accounted for 27% of the Company’s revenues for 2021. See Note 13 for further details. The Company does not require collateral or other security to support accounts receivable. To reduce credit risk, management performs ongoing credit evaluations of its customers’ financial condition. The Company maintains allowances for potential credit losses. The allowance for doubtful accounts, which was based on management’s best estimates, could be adjusted in the near term from current estimates depending on actual experience. Such adjustments could be material to the consolidated financial statements.
Cash and Cash Equivalents, and Short-term Investments, Policy	Cash and Cash Equivalents, and Short-term Investments The Company considers all highly liquid investments with an original maturity of 90 days or less or investments with a remaining maturity of 90 days or less at the purchase to be cash equivalents and investments with original maturities greater than 90 days but less than one year to be short-term investments. The Company classifies securities with readily determinable market values as available-for-sale. Short-term investments include available-for-sale securities and are carried at estimated fair value, with the unrealized gains and losses deemed temporary in nature, net of tax, reported as a component of accumulated other comprehensive loss in stockholders’ equity. Realized gains and losses and declines in value determined to be other than temporary are based on the specific identification method and are included as a component of other expense, net in the Consolidated Statements of Comprehensive Loss. The Company periodically reviews short-term investments for impairment. In the event a decline in value is determined to be other-than-temporary, an impairment loss is recognized. When determining if a decline in value is other-than-temporary, the Company takes into consideration the current market conditions, the duration and severity of and the reason for the decline, and the likelihood that it would need to sell the security prior to a recovery of par value. As of December 31, 2022, and 2021, short-term investments consisted solely of U.S. Treasury bills. The cost of these securities approximated fair value and there was no material gross realized or unrealized gains or losses as of December 31, 2022 and 2021. There were also no impairments in the investments’ value in the year ended December 31, 2022 and 2021. Refer to Note 14, “Fair Value Measurements” for further discussion on the Company’s investments. Restricted cash of $3.5 million noted in the Consolidated Statement of Cash Flows for the year ended December 31, 2020 pertains to the amount specifically designated to pay for the Holdback amount related to the Company’s acquisition of Cimetrix Incorporated (“Cimetrix”). Refer to Note 4, “Business Combination” for further discussion about the payment of Holdback Amount in fiscal 2021.
Accounts Receivable, Policy	Accounts Receivable Accounts receivable include amounts that are unbilled at the end of the period that are expected to be billed and collected within a 12-month period. Unbilled accounts receivable are determined on an individual contract basis. Unbilled accounts receivable, included in accounts receivable, totaled $13.5 million and $11.8 million as of December 31, 2022 and 2021, respectively. Unbilled accounts receivable that are not expected to be billed and collected during the succeeding 12-month period are recorded in other non-current assets and totaled $0.8 million and $1.3 million as of December 31, 2022 and 2021, respectively. The Company performs ongoing credit evaluations of its customers’ financial condition. An allowance for doubtful accounts is maintained for probable credit losses based upon the Company’s assessment of the expected collectability of the accounts receivable. The allowance for doubtful accounts is reviewed on a quarterly basis to assess the adequacy of the allowance. Accounts receivable reserves are summarized below (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Deductions/ ​ ​ ​ ​ Balance at ​ ​ ​ ​ Charged ​ Write-offs ​ Balance at ​ ​ Beginning ​ Charged to ​ Against ​ of Accounts ​ End of ​ of Period Expense (1) Revenue (1) Receivable Period 2022 ​ $ 890 ​ $ — ​ $ — ​ $ — ​ $ 890 2021 ​ $ 963 ​ $ — ​ $ — ​ $ (73) ​ $ 890 2020 ​ $ 213 ​ $ — ​ $ 800 ​ $ (50) ​ $ 963 (1) Additions to the accounts receivable reserve for doubtful accounts are charged to bad debt expense. Additions to the receivable reserve for billing adjustments are charged against revenue.
Property and Equipment, Policy	Property and Equipment Property and equipment are stated at cost and are depreciated using the straight-line method over the estimated useful lives (in years) of the related asset as follows: ​ ​ ​ ​ Computer equipment 3 Software 3 Furniture, fixtures, and equipment 5-10 Laboratory and test equipment 3-10 Leasehold improvements ​ Shorter of estimated useful life or term of lease ​
Intangible Assets, Policy	Intangible Assets Intangible assets consist of acquired technology, certain contract rights, customer relationships, patents, trademarks and trade names. These intangible assets may be acquired through business combinations or direct purchases. Intangible assets are amortized on a straight-line basis over their estimated useful lives which range from one ten
Goodwill, Policy	Goodwill The Company records goodwill when the purchase consideration of an acquisition exceeds the fair value of the net tangible and identified intangible assets as of the date of acquisition. The Company has one operating segment and one operating unit. The Company performs a qualitative analysis when testing a reporting unit’s goodwill for impairment. The Company performs an annual impairment assessment of goodwill during the fourth quarter of each calendar year or more frequently, if required to determine if any events or circumstances exist, such as an adverse change in business climate or a decline in the overall industry demand, that would indicate that it would more likely than not reduce the fair value of a reporting unit below its carrying amount, including goodwill. If events or circumstances do not indicate that the fair value of a reporting unit is below its carrying amount, then goodwill is not considered to be impaired and no further testing is required. If the carrying amount exceeds its fair value, an impairment loss would be recognized equal to the amount of excess, limited to the amount of total goodwill.
Leases, Policy	Leases The Company has operating leases for administrative and sales offices, research and development laboratory and clean room. The Company recognizes long-term operating lease rights and commitments as operating lease right-of-use assets (ROU), operating lease liabilities and operating lease liabilities, non-current, respectively, in the Consolidated Balance Sheets. The Company elected to not separate lease and non-lease components for all of its leases. The Company determines if an arrangement is, or contains, a lease at inception. Operating lease right-of-use assets, and operating lease liabilities are initially recorded based on the present value of lease payments over the lease term. Lease terms include the minimum unconditional term of the lease, and may include options to extend or terminate the lease when it is reasonably certain at the commencement date that such options will be exercised. The decision to include these options involves consideration of our overall future business plans and other relevant business economic factors that may affect our business. Since the determination of the lease term requires an application of judgment, lease terms that differ in reality from our initial judgment may potentially have a material impact on the Company’s Consolidated Balance Sheets. In addition, the Company’s leases do not provide an implicit rate. In determining the present value of the Company’s expected lease payments, the discount rate is calculated using the Company’s incremental borrowing rate determined based on the information available, which requires additional judgment.
Software Development Costs, Policy	Software Development Costs Internally developed software is software developed to meet our internal needs to provide certain services to the customers. The Company’s capitalized software development costs consist of internal compensation related costs and external direct costs incurred during the application development stage and are amortized over their useful lives, generally five six
Cost of Revenues, Policy	Cost of Revenues Costs of revenues consist primarily of costs incurred to provide and support our services, costs recognized in connection with licensing our software, IT and facilities-related costs and amortization of acquired technology. Service costs include material, personnel-related costs including compensation, employee benefits, bonus and stock-based compensation expense, subcontractor costs, overhead costs, travel, and allocated facilities-related costs. Software license costs consist of costs associated with cloud-delivery related expenses and licensing third-party software used by us in providing services to the Company’s customers in solution engagements or sold in conjunction with the Company’s software products.
Research and Development Expenses, Policy	Research and Development Expenses Research and development expenses consist primarily of personnel-related costs including compensation, employee benefits, bonus and stock-based compensation expense, outside development services, travel, third-party cloud-services related costs, IT and facilities cost allocations to support product development activities. Research and development expenses are charged to operations as incurred.
Selling, General and Administrative Expenses, Policy	Selling, General and Administrative Expenses Selling, general and administrative expenses consist primarily of personnel-related costs including compensation, employee benefits, bonus, commission and stock-based compensation expense for sales, marketing and general and administrative personnel, legal, tax and accounting services, marketing communications expenses, third-party cloud-services related costs, travel, IT and facilities cost allocations.
Stock-Based Compensation, Policy	Stock-Based Compensation The Company accounts for stock-based compensation using the fair value method, which requires the Company to measure stock-based compensation based on the grant-date fair value of the awards and recognize the compensation expense over the requisite service period. As stock-based compensation expense recognized is based on awards ultimately expected to vest, it has been reduced for estimated forfeitures. Forfeitures are estimated at the time of grant and revised, if necessary, in subsequent periods if actual forfeitures differ from those estimates. The fair value of the Company’s restricted stock units (“RSUs”) is equal to the market value of the Company’s common stock on the date of the grant. These awards are subject to time-based vesting which generally occurs over a period of four years The fair value of the Company’s stock options is estimated using the Black-Scholes-Merton option-pricing model, which incorporates various assumptions including volatility, expected life and interest rates. The expected volatility is based on the historical volatility of the Company’s common stock over the most recent period commensurate with the estimated expected life of the Company’s stock options. The expected life is based on historical experience and on the terms and conditions of the stock options granted. The interest rate assumption is based upon observed Treasury yield curve rates appropriate for the expected life of the Company’s stock options.
Income Taxes, Policy	Income Taxes The Company’s provision for income tax comprises its current tax liability and change in deferred tax assets and liabilities. Deferred tax assets and liabilities are recognized for the expected tax consequences of temporary differences between the tax bases of assets and liabilities. The measurement of current and deferred tax assets and liabilities is based on provisions of enacted tax laws; the effect of future changes in tax laws or rates are not anticipated. Valuation allowances are provided to reduce deferred tax assets to an amount that in management’s judgment is more likely than not to be recoverable against future taxable income. No U.S. taxes are provided on earnings of non-U.S. subsidiaries, to the extent such earnings are deemed to be permanently invested. The Company’s income tax calculations are based on application of applicable U.S. federal and state or foreign tax laws. The Company’s tax filings, however, are subject to audit by the respective tax authorities. Accordingly, the Company recognizes tax liabilities based upon its estimate of whether, and the extent to which, additional taxes will be due when such estimates are more-likely-than-not to be sustained. An uncertain income tax position will not be recognized if it has less than a 50% likelihood of being sustained. To the extent the final tax liabilities are different from the amounts originally accrued, the increases or decreases are recorded as income tax expense or benefit in the Consolidated Statements of Comprehensive Loss.
Net Income (Loss) Per Share, Policy	Net Income (Loss) Per Share Basic net income (loss) per share is computed by dividing net income by weighted average number of common shares outstanding for the period (excluding outstanding stock options and shares subject to repurchase). Diluted net income (loss) per share is computed using the weighted-average number of common shares outstanding for the period plus the potential effect of dilutive securities which are convertible into common shares (using the treasury stock method), except in cases in which the effect would be anti-dilutive. Dilutive potential common shares consist of incremental common shares issuable upon exercise of stock options, upon vesting of RSUs, contingently issuable shares for all periods and assumed issuance of shares under the Company’s employee stock purchase plan. No dilutive potential common shares are included in the computation of any diluted per share amount when a loss from continuing operations was reported by the Company.
Foreign Currency Translation, Policy	Foreign Currency Translation The functional currency of the Company’s foreign subsidiaries is the local currency for the respective subsidiary. The assets and liabilities are translated at the period-end exchange rate, and statements of comprehensive loss are translated at the average exchange rate during the year. Gains and losses resulting from foreign currency translations are included as a component of other comprehensive loss. Gains and losses resulting from foreign currency transactions are included in the Consolidated Statements of Comprehensive Loss.
Derivative Financial Instruments, Policy	Derivative Financial Instruments The Company operates internationally and is exposed to potentially adverse movements in foreign currency exchange rates. From time to time, the Company enters into foreign currency forward contracts to reduce the exposure to foreign currency exchange rate fluctuations on certain foreign currency denominated monetary assets and liabilities. The Company does not use foreign currency contracts for speculative or trading purposes. The Company records these forward contracts at fair value. The counterparty to these foreign currency forward contracts is a financial institution that the Company believes is creditworthy, and therefore, we believe the credit risk of counterparty non-performance is not significant. These foreign currency forward contracts are not designated for hedge accounting treatment. Therefore, the change in fair value of these derivatives is recorded into earnings as a component of interest and other income (expense), net and offsets the change in fair value of the foreign currency denominated monetary assets and liabilities, which are also recorded in interest and other income (expense), net. The duration of these forward contracts is usually three months.
Business Combinations, Policy	Business Combinations The Company allocates the fair value of purchase consideration to the tangible assets acquired, liabilities assumed and intangible assets acquired based on their estimated fair values at the date of the business combination. The excess of the fair value of purchase consideration over the fair values of these identifiable assets and liabilities is recorded as goodwill. Such valuations require management to make significant estimates and assumptions, especially with respect to intangible assets. Significant estimates in valuing certain intangible assets include, but are not limited to, estimated replacement costs and future expected cash flows from acquired customers, acquired technology, acquired patents, and trade names from a market participant perspective, useful lives and discount rates. Management’s estimates of fair value are based upon assumptions believed to be reasonable, but which are inherently uncertain and unpredictable and, as a result, actual results may differ from estimates. Allocation of purchase consideration to identifiable assets and liabilities affects the Company’s amortization expense, as acquired finite-lived intangible assets are amortized over the useful life, whereas any indefinite lived intangible assets, including in-process research and development, and goodwill, are not amortized but tested annually for impairment. During the measurement period, which is not to exceed one year from the acquisition date, the Company records adjustments to the assets acquired and liabilities assumed, with the corresponding offset to goodwill. Upon the conclusion of the measurement period, any subsequent adjustments are recorded to earnings.
Litigation, Policy	Litigation From time to time, the Company is subject to various claims and legal proceedings that arise in the ordinary course of business. The Company accrues for losses related to litigation when a potential loss is probable and the loss can be reasonably estimated in accordance with Financial Accounting Standards Board (FASB) requirements. See Note 8, “Commitments and Contingencies”.
Accounting Standards Not Yet Effective, Policy	Accounting Standards Not Yet Effective In June 2016, the FASB issued ASU No. 2016-13, Financial Instruments – Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments (ASU 2016-13), which requires measurement and recognition of expected credit losses for financial assets held at the reporting date based on internal information, external information, or a combination of both relating to past events, current conditions, and reasonable and supportable forecasts. ASU No. 2016-13 replaces the existing incurred loss impairment model with a forward-looking expected credit loss model, which will result in earlier recognition of credit losses. Subsequent to the issuance of ASU No. 2016-13, the FASB issued ASU No. 2018-19, Codification Improvements to Topic 326, Financial Instruments – Credit Losses, ASU No. 2019-04, Codification Improvements to Topic 326, Financial Instruments – Credit Losses, Topic 815, Derivatives and Hedging, and Topic 825, Financial Instrument, ASU No. 2019-05, Financial Instruments – Credit Losses (Topic 326) Targeted Transition Relief, ASU No. 2016-13, ASU No. 2019-10 Financial Instruments-Credit Losses (Topic 326), Derivatives and Hedging (Topic 815), and Leases (Topic 842), and ASU No. 2019-11 Codification Improvements to Topic 326, Financial Instruments-Credit Losses. The subsequent ASUs do not change the core principle of the guidance in ASU No. 2016-13. Instead, these amendments are intended to clarify and improve operability of certain topics included within ASU No. 2016-13. Additionally, ASU No. 2019-10 defers the effective date for the adoption of the new standard on credit losses for public filers that are considered small reporting companies (“SRC”) as defined by the SEC to fiscal years beginning after December 15, 2022, including interim periods within those fiscal years. The Company will adopt this standard effective the first quarter of 2023. In February 2020, the FASB issued ASU 2020-02, which provides guidance regarding methodologies, documentation, and internal controls related to expected credit losses. The subsequent amendments will have the same effective date and transition requirements as ASU No. 2016-13. Topic 326 requires a modified retrospective approach by recording a cumulative-effect adjustment to retained earnings as of the beginning of the period of adoption. The Company is in the process of evaluating the impact of Topic 326 on its consolidated financial statements and the related disclosure but does not believe it will have a material effect. Management has reviewed other recently issued accounting pronouncements issued or proposed by the FASB, and does not believe any of these accounting pronouncements has had or will have a material impact on the consolidated financial statements.

DESCRIPTION OF BUSINESS AND S_2

DESCRIPTION OF BUSINESS AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Tables)	12 Months Ended
	Dec. 31, 2022
Notes Tables
Allowance for Doubtful Accounts [Table Text Block]	Accounts receivable reserves are summarized below (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Deductions/ ​ ​ ​ ​ Balance at ​ ​ ​ ​ Charged ​ Write-offs ​ Balance at ​ ​ Beginning ​ Charged to ​ Against ​ of Accounts ​ End of ​ of Period Expense (1) Revenue (1) Receivable Period 2022 ​ $ 890 ​ $ — ​ $ — ​ $ — ​ $ 890 2021 ​ $ 963 ​ $ — ​ $ — ​ $ (73) ​ $ 890 2020 ​ $ 213 ​ $ — ​ $ 800 ​ $ (50) ​ $ 963 (1) Additions to the accounts receivable reserve for doubtful accounts are charged to bad debt expense. Additions to the receivable reserve for billing adjustments are charged against revenue.
Property Plant and Equipment Estimated Useful Lives [Table Text Block]	Property and equipment are stated at cost and are depreciated using the straight-line method over the estimated useful lives (in years) of the related asset as follows: ​ ​ ​ ​ Computer equipment 3 Software 3 Furniture, fixtures, and equipment 5-10 Laboratory and test equipment 3-10 Leasehold improvements ​ Shorter of estimated useful life or term of lease ​

REVENUE (Tables)

REVENUE (Tables)	12 Months Ended
	Dec. 31, 2022
REVENUE
Schedule of Disaggregation of Revenue	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year Ended December 31, ​ 2022 2021 ​ 2020 ​ Over time ​ 69 % 65 % 63 % Point-in-time 31 % 35 % 37 % Total 100 % 100 % 100 % ​

BUSINESS COMBINATION (Tables)

BUSINESS COMBINATION (Tables)	12 Months Ended
	Dec. 31, 2022
Notes Tables
Schedule of Business Acquisitions, by Acquisition [Table Text Block]	The following summarizes the final allocation of the purchase price for this acquisition, as of the date of the acquisition, is as follows (in thousands, except amortization period): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Amortization ​ Amount Period (Years) Allocation of Purchase Price: ​ Assets ​ Fair value of tangible assets (including cash of $5,900) ​ $ 8,298 Fair value of intangible assets: ​ Developed technology ​ 12,541 8 In-process R&D ​ 3,635 N/A Customer relationships ​ 1,967 10 Noncompetition agreements ​ 848 3 Tradenames and trademarks ​ 808 10 Goodwill ​ 11,830 N/A Total assets acquired ​ $ 39,927 Liabilities ​ Accounts payable and accrued expenses ​ $ 1,447 Deferred revenue ​ 375 Operating lease liabilities ​ 132 Deferred tax liabilities ​ 439 Total liabilities assumed ​ $ 2,393 Total purchase price allocation ​ $ 37,534 ​

PROPERTY AND EQUIPMENT (Tables)

PROPERTY AND EQUIPMENT (Tables)	12 Months Ended
	Dec. 31, 2022
PROPERTY AND EQUIPMENT
Schedule of Property, Plant and Equipment	Property and equipment consist of (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, ​ 2022 2021 Computer equipment ​ $ 11,853 ​ $ 11,924 Software ​ 5,395 ​ 5,419 Furniture, fixtures and equipment ​ 2,484 ​ 2,506 Leasehold improvements ​ 6,467 ​ 6,272 Laboratory and other equipment ​ 4,431 ​ 3,981 Test equipment ​ 28,403 ​ 24,452 Construction-in-progress ​ 27,336 ​ 22,158 ​ ​ 86,369 ​ 76,712 Less: Accumulated depreciation and amortization ​ (46,195) ​ (41,417) Total ​ $ 40,174 ​ $ 35,295 ​

GOODWILL AND INTANGIBLE ASSETS

GOODWILL AND INTANGIBLE ASSETS (Tables)	12 Months Ended
	Dec. 31, 2022
GOODWILL AND INTANGIBLE ASSETS
Schedule of Goodwill	As of December 31, 2022 and 2021, the carrying amount of goodwill was $14.1 million. The following table summarizes goodwill transaction for the years ended December 31, 2022, 2021 and 2020 (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year Ended December 31, ​ ​ 2022 2021 ​ 2020 Balance at beginning of year ​ $ 14,123 ​ $ 15,774 ​ $ 2,293 Addition ​ ​ — ​ ​ — ​ ​ 13,481 Measurement period acquisition adjustment (1) ​ — ​ (1,651) ​ — Balance at end of year ​ $ 14,123 ​ $ 14,123 ​ $ 15,774 ​ (1) Goodwill adjustment was recorded within the measurement period with a corresponding reduction in the Holdback Amount and reduction to net deferred tax liabilities. See Note 4, “Business Combination”. ​
Schedule of Finite-Lived Intangible Assets, Net	Intangible assets balance was $18.1 million and $21.2 million as of December 31, 2022 and 2021, respectively. Intangible assets as of December 31, 2022 and 2021, consist of the following (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, 2022 ​ December 31, 2021 ​ ​ Amortization ​ Gross ​ ​ ​ ​ Net ​ Gross ​ ​ ​ ​ Net ​ ​ Period ​ Carrying ​ Accumulated ​ Carrying ​ Carrying ​ Accumulated ​ Carrying ​ ​ (Years) Amount Amortization Amount Amount Amortization Amount Acquired identifiable intangibles: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Customer relationships 1 - 10 ​ $ 9,407 ​ $ (6,684) ​ $ 2,723 ​ $ 9,407 ​ $ (6,041) ​ $ 3,366 Developed technology 4 - 9 ​ 33,635 ​ (19,647) ​ 13,988 ​ 33,635 ​ (17,250) ​ 16,385 Tradename and trademarks 2 - 10 ​ 1,598 ​ (918) ​ 680 ​ 1,598 ​ (812) ​ 786 Patent 6 - 10 ​ 2,100 ​ (1,696) ​ 404 ​ 1,800 ​ (1,640) ​ 160 Noncompetition agreements 3 ​ 848 ​ (588) ​ 260 ​ 848 ​ (306) ​ 542 Total ​ ​ ​ $ 47,588 ​ $ (29,533) ​ $ 18,055 ​ $ 47,288 ​ $ (26,049) ​ $ 21,239 ​
Schedule of Finite-lived Intangible Assets Amortization Expense	The weighted average amortization period for acquired identifiable intangible assets was 5.9 years as of December 31, 2022. The following table summarizes intangible assets amortization expense in the Consolidated Statements of Comprehensive Loss (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year Ended December 31, ​ 2022 2021 2020 Amortization of acquired technology included under Costs of Revenues ​ $ 2,214 ​ $ 2,079 ​ $ 705 Amortization of acquired intangible assets presented separately under Costs and Expenses ​ 1,270 ​ 1,255 ​ 741 Total amortization of acquired intangible assets ​ $ 3,484 ​ $ 3,334 ​ $ 1,446 ​
Schedule of Finite-Lived Intangible Assets, Future Amortization Expense	The Company expects annual amortization of acquired identifiable intangible assets to be as follows (in thousands): ​ ​ ​ ​ ​ Year Ending December 31, Amount 2023 ​ $ 3,491 2024 ​ 3,093 2025 ​ 2,928 2026 ​ 2,759 2027 ​ 2,606 2028 and thereafter ​ 3,178 Total future amortization expense ​ $ 18,055 ​

LEASES (Tables)

LEASES (Tables)	12 Months Ended
	Dec. 31, 2022
LEASES
Schedule of Lease Expenses	In 2022, the Company early terminated an office lease contract. The termination of this lease reduced the Company’s operating lease right-of-use assets and lease liabilities by approximately $0.5 million and $0.6 million, respectively. The gain from the lease termination of approximately $0.1 million was recorded under selling, general and administrative expense in the accompanying Consolidated Statement of Comprehensive Loss for the year ended December 31, 2022. Lease expense was comprised of the following (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year Ended December 31, ​ 2022 2021 2020 Operating lease expense (1) ​ $ 1,457 ​ $ 1,860 ​ $ 1,828 Short-term lease and variable lease expense (2) ​ 1,032 ​ 822 ​ 545 Total lease expense ​ $ 2,489 ​ $ 2,682 ​ $ 2,373 ​ (1) Net of gain recognized upon lease termination of $0.1 million in the year ended December 31, 2022. (2) Leases with an initial term of 12 months or less are not recorded on the Consolidated Balance Sheets, and the Company recognizes lease expense for these leases on a straight-line basis over the lease term. Variable lease expense for the periods presented primarily included common area maintenance charges. Supplemental consolidated balance sheets information related to leases was as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, ​ 2022 2021 Weighted average remaining lease term under operating ROU leases (in years) ​ ​ 5.3 ​ ​ 5.7 ​ Weighted average discount rate for operating lease liabilities ​ 4.87 % ​ 5.25 % ​
Schedule of Operating Lease Liabilities and Maturities	Maturity of operating lease liabilities as of December 31, 2022, are as follows (in thousands): ​ ​ ​ ​ ​ Year Ending December 31, Amount (1) 2023 ​ $ 1,570 2024 ​ 1,633 2025 ​ 1,547 2026 ​ 1,357 2027 ​ 1,294 2028 and thereafter ​ ​ 991 Total future minimum lease payments ​ $ 8,392 Less: Interest (2) ​ (1,048) Present value of future minimum lease payments under operating lease liabilities (3) ​ $ 7,344 (1) As of December 31, 2022, the total operating lease liability includes $0.9 million related to an option to extend a lease term that is reasonably certain to be exercised . (2) Calculated using incremental borrowing interest rate for each lease. (3) Includes the current portion of operating lease liabilities of $1.4 million as of December 31, 2022.

EMPLOYEE BENEFIT PLANS (Tables)

EMPLOYEE BENEFIT PLANS (Tables)	12 Months Ended
	Dec. 31, 2022
EMPLOYEE BENEFIT PLANS
Schedule of Share-Based Payment Award, Employee Stock Purchase Plan, Valuation Assumptions	The Company estimated the fair value of purchase rights granted under the Employee Purchase Plans during the period using the Black-Scholes-Merton option-pricing model with the following weighted average assumptions, resulting in the following weighted average fair values: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ 2021 Purchase Plan ​ ​ 2010 Purchase Plan ​ ​ ​ Year Ended December 31, ​ ​ Year Ended December 31, ​ ​ Year Ended December 31, ​ ​ ​ 2022 ​ 2021 ​ 2020 Expected life (in years) ​ ​ 1.25 ​ ​ 1.25 ​ ​ 1.25 Volatility ​ ​ 48.73 % ​ ​ 48.00 % ​ ​ 34.25 % Risk-free interest rate ​ ​ 2.75 % ​ ​ 0.11 % ​ ​ 1.43 % Expected dividend ​ ​ — ​ ​ — ​ ​ — Weighted average fair value of purchase rights granted during the period ​ $ 10.00 ​ ​ $ 6.71 ​ ​ $ 4.83 ​ ​
Schedule of Share-based Payment Awards, Stock Options, Valuation Assumptions	The Company has elected to use the Black-Scholes-Merton option-pricing model, which incorporates various assumptions including volatility, expected life, interest rate and expected dividend. The expected volatility is based on the historical volatility of the Company’s common stock over the most recent period commensurate with the estimated expected life of the Company’s stock options. The expected life of an award is based on historical experience and on the terms and conditions of the stock awards granted to employees. The interest rate assumption is based upon observed Treasury yield curve rates appropriate for the expected life of the Company’s stock options. ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year Ended December 31, ​ ​ 2022 2021 2020 Expected life (in years) ​ ​ — ​ ​ — ​ ​ 4.45 ​ Volatility ​ — % ​ — % ​ 40.90 % Risk-free interest rate ​ — % ​ — % ​ 0.60 % Expected dividend ​ — ​ — ​ ​ — ​ Weighted average fair value per share of options granted during the period ​ $ — ​ $ — ​ $ 5.75 ​ ​ No stock options were granted during the years ended December 31, 2022 and 2021.
Schedule of Share-based Payment Arrangement, Expensed and Capitalized Amounts	Stock-based compensation expenses related to the Company’s stock plans and employee stock purchase plans were allocated as follows (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year Ended December 31, ​ 2022 2021 2020 Costs of revenues ​ $ 2,974 ​ $ 2,563 ​ $ 3,454 Research and development ​ 9,391 ​ 5,515 ​ 4,800 Selling, general and administrative ​ 7,284 ​ 4,853 ​ 4,209 Stock-based compensation expenses ​ $ 19,649 ​ $ 12,931 ​ $ 12,463 ​
Schedule of Share-based Payment Arrangement, Options Activity - Additional Information	Additional information with respect to options under the Plans is as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Outstanding Options ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted ​ ​ ​ ​ ​ ​ ​ Weighted ​ Average ​ ​ ​ ​ ​ ​ ​ Average ​ Remaining ​ Aggregate ​ ​ Number of ​ Exercise ​ Contractual ​ Intrinsic ​ ​ Options ​ Price ​ Term ​ Value ​ (in thousands) per Share (Years) (in thousands) Outstanding, January 1, 2020 745 ​ $ 10.64 ​ Granted (weighted average fair value of $5.75 per share) 24 ​ $ 16.72 ​ Exercised (246) ​ $ 10.46 ​ Canceled (57) ​ $ 11.65 ​ Expired (10) ​ $ 10.06 ​ Outstanding, December 31, 2020 456 ​ $ 10.95 ​ Granted — ​ $ — ​ Exercised (216) ​ $ 8.90 ​ Canceled (10) ​ $ 15.56 ​ Expired (4) ​ $ 6.90 ​ Outstanding, December 31, 2021 226 ​ $ 12.78 ​ Granted — ​ ​ — ​ Exercised (150) ​ ​ 11.27 ​ Canceled (6) ​ ​ 13.52 ​ Expired (2) ​ ​ 8.79 ​ Outstanding, December 31, 2022 68 ​ $ 16.11 4.89 ​ $ 847 Vested and expected to vest, December 31, 2022 68 ​ $ 16.11 4.87 ​ $ 842 Exercisable, December 31, 2022 57 ​ $ 16.07 4.46 ​ $ 706 ​
Schedule of Share-based Payment Arrangement, Restricted Stock Unit Activity	Nonvested shares (restricted stock units) were as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted ​ ​ ​ ​ Average Grant ​ ​ Shares ​ Date Fair Value ​ (in thousands) Per Share Nonvested, January 1, 2020 1,887 ​ $ 12.30 Granted 890 ​ $ 21.31 Vested (867) ​ $ 13.25 Forfeited (163) ​ $ 13.23 Nonvested, December 31, 2020 1,747 ​ $ 16.33 Granted 977 ​ $ 19.43 Vested (689) ​ $ 15.23 Forfeited (163) ​ $ 17.63 Nonvested, December 31, 2021 1,872 ​ $ 18.24 Granted 1,210 ​ $ 23.23 Vested (862) ​ $ 17.57 Forfeited (96) ​ $ 19.71 Nonvested, December 31, 2022 2,124 ​ $ 21.29 ​

INCOME TAXES (Tables)

INCOME TAXES (Tables)	12 Months Ended
	Dec. 31, 2022
INCOME TAXES
Schedule of Components of Income Tax Expense (Benefit)	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year Ended December 31, ​ 2022 2021 ​ 2020 ​ ​ (In thousands) U.S. ​ ​ ​ ​ ​ ​ ​ Current ​ $ 1,210 ​ $ (67) ​ $ (1,325) Deferred ​ 13 ​ 1,318 ​ 21,056 Foreign ​ ​ ​ Current ​ 577 ​ 237 ​ 238 Withholding ​ 2,111 ​ 1,591 ​ 2,392 Deferred ​ (12) ​ 92 ​ (58) Total income tax expense ​ $ 3,899 ​ $ 3,171 ​ $ 22,303 ​
Schedule of Effective Income Tax Rate Reconciliation	The income tax expense differs from the amount estimated by applying the statutory federal income tax rate (21% for 2022, 2021 and 2020) for the following reasons (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year Ended December 31, ​ 2022 2021 2020 Federal statutory tax expense ​ $ 106 ​ $ (3,847) ​ $ (3,793) State tax provision ​ 949 ​ 239 ​ 703 Stock compensation expense ​ (898) ​ (499) ​ (602) Tax credits ​ (2,877) ​ (2,676) ​ (3,488) Foreign tax, net ​ 2,195 ​ 1,653 ​ 2,443 Foreign-derived intangible income (FDII) deduction ​ ​ (830) ​ ​ — ​ ​ — Change in valuation allowance ​ 5,122 ​ 8,099 ​ 29,034 Unrealized tax benefit reserve changes ​ ​ 136 ​ ​ (151) ​ ​ — Business combination costs ​ ​ — ​ ​ — ​ ​ 356 Tax law changes ​ — ​ — ​ (2,237) Other ​ (4) ​ 353 ​ (113) Total income tax expense ​ $ 3,899 ​ $ 3,171 ​ $ 22,303 ​
Schedule of Deferred Tax Assets and Liabilities	The components of the net deferred tax assets are comprised of (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, ​ 2022 2021 Deferred tax assets ​ ​ Net operating loss carry forward ​ $ 3,861 ​ $ 13,149 Research and development and other credit carry forward ​ 28,046 ​ 26,591 Foreign tax credit carry forward ​ 11,764 ​ 11,010 Capitalized research and experimental expenses ​ ​ 10,069 ​ ​ — Accruals deductible in different periods ​ 7,713 ​ 3,362 Leases ​ 1,623 ​ 1,472 Stock-based compensation ​ 1,948 ​ 1,442 Total deferred tax assets ​ 65,024 ​ 57,026 Less: valuation allowance ​ (59,215) ​ (51,586) Deferred tax assets, net of valuation allowance ​ $ 5,809 ​ $ 5,440 ​ ​ ​ ​ ​ ​ ​ Deferred tax liabilities ​ ​ Property and equipment, net ​ (540) ​ 178 Operating lease right-of-use assets ​ (1,635) ​ (1,472) Intangible assets ​ (3,617) ​ (4,129) Deferred tax liabilities ​ $ (5,792) ​ $ (5,423) ​ ​ ​ ​ ​ ​ ​ Net deferred tax assets ​ $ 17 ​ $ 17 ​
Schedule of Unrecognized Tax Benefits Roll Forward	A reconciliation of the beginning and ending amount of unrecognized tax benefits is as follows (in thousands): ​ ​ ​ ​ ​ ​ Amount Gross unrecognized tax benefits, January 1, 2020 ​ $ 13,615 Increases in tax positions for current year ​ 1,024 Increases in tax positions for prior years ​ 71 Lapse in statute of limitations ​ (410) Gross unrecognized tax benefits, December 31, 2020 ​ 14,300 Increases in tax positions for current year ​ 853 Increases in tax positions for prior years ​ 1 Lapse in statute of limitations ​ (411) Gross unrecognized tax benefits, December 31, 2021 ​ 14,743 Increases in tax positions for current year ​ 988 Increases in tax positions for prior years ​ — Lapse in statute of limitations ​ (622) Gross unrecognized tax benefits, December 31, 2022 ​ $ 15,109 ​
Summary of Valuation Allowance	Valuation allowance for deferred tax assets is summarized (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Balance at ​ Charged to ​ Deductions/ ​ Balance at ​ ​ Beginning ​ Costs and ​ Write-offs of ​ End of ​ of Period Expenses Accounts Period Valuation allowance for deferred tax assets ​ ​ ​ ​ 2022 ​ $ 51,586 ​ $ 7,629 ​ $ — ​ $ 59,215 2021 ​ $ 41,859 ​ $ 9,727 ​ $ — ​ $ 51,586 2020 ​ $ 10,486 ​ $ 31,373 ​ $ — ​ $ 41,859

NET LOSS PER SHARE (Tables)

NET LOSS PER SHARE (Tables)	12 Months Ended
	Dec. 31, 2022
NET LOSS PER SHARE
Schedule of Earnings Per Share, Basic and Diluted	Basic net loss per share is computed by dividing net loss by weighted average number of common shares outstanding for the period (excluding outstanding stock options and shares subject to repurchase). Diluted net loss per share is computed using the weighted-average number of common shares outstanding for the period plus the potential effect of dilutive securities which are convertible into common shares (using the treasury stock method), except in cases in which the effect would be anti-dilutive. The following is a reconciliation of the numerators and denominators used in computing basic and diluted net loss per share (in thousands except per share amount): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year Ended December 31, ​ 2022 2021 2020 Numerator: ​ ​ ​ Net loss ​ $ (3,429) ​ $ (21,488) ​ $ (40,363) Denominator: ​ ​ ​ Basic weighted-average shares outstanding ​ 37,309 ​ 37,138 ​ 34,458 Effect of dilutive options and restricted stock units ​ — ​ — ​ — Diluted weighted-average shares outstanding ​ 37,309 ​ 37,138 ​ 34,458 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Net loss per share, basic and diluted ​ $ (0.09) ​ $ (0.58) ​ $ (1.17) ​
Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share	The following table sets forth potential shares of common stock that are not included in the diluted net loss per share calculation above because to do so would be anti-dilutive for the periods indicated (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year Ended December 31, ​ 2022 2021 2020 Outstanding options 56 170 332 Non-vested restricted stock units 787 ​ 968 ​ 921 Employee Stock Purchase Plan 84 ​ 33 ​ 160 Total 927 ​ 1,171 ​ 1,413

CUSTOMER AND GEOGRAPHIC INFOR_2

CUSTOMER AND GEOGRAPHIC INFORMATION (Tables)	12 Months Ended
	Dec. 31, 2022
CUSTOMER AND GEOGRAPHIC INFORMATION
Schedule of Revenue by Major Customers by Reporting Segments	Revenues from individual customers that are approximately 10% or more of the Company’s consolidated total revenues are as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year Ended December 31, Customer 2022 ​ 2021 ​ 2020 A ​ 31 % ​ 17 % ​ * % B ​ 10 % ​ * % ​ * % D ​ * % ​ 10 % ​ * % E ​ * % ​ * % ​ 23 % ​ Gross accounts receivable balances (including amounts that are unbilled) from individual customers that are approximately 10% or more of the Company’s gross accounts receivable balance are as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, Customer 2022 2021 A 29 % 29 % B 12 % 15 % C ​ 12 % * % * represents less than 10%
Schedule of Revenue from External Customers Attributed to Foreign Countries by Geographic Area	Revenues from customers by geographic area based on the location of the customers’ work sites are as follows (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year Ended December 31, ​ ​ 2022 ​ ​ 2021 ​ 2020 ​ ​ ​ ​ ​ Percentage ​ ​ ​ ​ ​ Percentage ​ ​ ​ ​ Percentage ​ Revenues of Revenues ​ Revenues of Revenues ​ Revenues of Revenues United States ​ $ 73,625 50 % ​ $ 50,374 ​ 45 % ​ $ 36,723 ​ 42 % China ​ 24,494 16 ​ ​ 14,267 ​ 13 ​ ​ 13,776 ​ 16 ​ Japan ​ ​ 13,916 ​ 9 ​ ​ ​ 11,097 ​ 10 ​ ​ ​ 4,762 ​ 5 ​ Rest of the world ​ 36,514 25 ​ ​ 35,322 ​ 32 ​ ​ 32,785 ​ 37 ​ Total revenue ​ $ 148,549 100 % ​ $ 111,060 100 % ​ $ 88,046 100 % ​
Schedule of Disclosure on Geographic Areas, Long-Lived Assets in Individual Foreign Countries by Country	Long-lived assets, net by geographic area is as follows (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, ​ 2022 2021 United States (1) ​ $ 44,730 ​ $ 39,158 Rest of the world ​ 1,446 ​ 1,545 Total long-lived assets, net ​ $ 46,176 ​ $ 40,703 ​ ​ ​ ​ ​ ​ (1) Includes assets deployed at customer sites which could be outside the U.S.

FINANCIAL INSTRUMENTS (Tables)

FINANCIAL INSTRUMENTS (Tables)	12 Months Ended
	Dec. 31, 2022
FINANCIAL INSTRUMENTS
Schedule of Fair Value, Assets Measured on Recurring Basis	The following table represents the Company’s assets measured at fair value on a recurring basis as of December 31, 2022 and the basis for that measurement (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Fair Value Measurements Using ​ ​ ​ ​ ​ Quoted ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Prices in ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Active ​ Significant ​ ​ ​ ​ ​ ​ ​ ​ Markets for ​ Other ​ ​ ​ ​ ​ ​ ​ ​ Identical ​ Observable ​ Significant ​ ​ December 31, ​ Assets ​ Inputs ​ Unobservable Assets 2022 (Level 1) (Level 2) Inputs (Level 3) Cash equivalents ​ ​ ​ ​ Money market mutual funds ​ $ 75,738 ​ $ 75,738 ​ $ — ​ $ — U.S. Government securities (1) ​ ​ 1,990 ​ ​ 1,990 ​ ​ — ​ ​ — Short-term investments (available-for-sale debt securities) ​ ​ ​ ​ U.S. Government securities (1) ​ 19,557 ​ 19,557 ​ — ​ — Total ​ $ 97,285 ​ $ 97,285 ​ $ — ​ $ — ​ The following table represents the Company’s assets measured at fair value on a recurring basis as of December 31, 2021 and the basis for that measurement (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Fair Value Measurements Using ​ ​ ​ ​ ​ Quoted ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Prices in ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Active ​ Significant ​ ​ ​ ​ ​ ​ ​ ​ Markets for ​ Other ​ Significant ​ ​ ​ ​ ​ Identical ​ Observable ​ Unobservable ​ ​ December 31, ​ Assets ​ Inputs ​ Inputs Assets 2021 (Level 1) (Level 2) (Level 3) Cash equivalents ​ ​ ​ ​ Money market mutual funds ​ $ 12,474 ​ $ 12,474 ​ $ — ​ $ — Short-term investments (available-for-sale debt securities) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ U.S. Government securities (1) ​ ​ 112,542 ​ ​ 112,542 ​ ​ — ​ ​ — Total ​ $ 125,016 ​ $ 125,016 ​ $ — ​ $ —

SELECTED QUARTERLY FINANCIAL _2

SELECTED QUARTERLY FINANCIAL DATA (UNAUDITED) (Tables)	12 Months Ended
	Dec. 31, 2022
SELECTED QUARTERLY FINANCIAL DATA (UNAUDITED)
Schedule of selected quarterly financial data (unaudited)	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year Ended December 31, 2022 ​ Q1 Q2 Q3 Q4 ​ ​ (In thousands, except for per share amounts) Total revenues ​ $ 33,498 ​ $ 34,668 ​ $ 39,860 ​ $ 40,523 Costs of revenues ​ $ 11,529 ​ $ 12,042 ​ $ 12,545 ​ $ 11,791 Net income (loss) ​ $ (4,150) ​ $ (1,147) ​ $ 1,385 ​ $ 483 Net income (loss) per share: ​ ​ ​ ​ Basic and diluted ​ $ (0.11) ​ $ (0.03) ​ $ 0.04 ​ $ 0.01 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year Ended December 31, 2021 ​ Q1 Q2 Q3 Q4 ​ ​ (In thousands, except for per share amounts) Total revenues ​ $ 24,200 ​ $ 27,419 ​ $ 29,555 ​ $ 29,886 Costs of revenues ​ $ 10,663 ​ $ 10,785 ​ $ 11,070 ​ $ 11,675 Net loss ​ $ (7,597) ​ $ (4,484) ​ $ (2,407) ​ $ (7,000) Net loss per share: ​ ​ ​ ​ Basic and diluted ​ $ (0.21) ​ $ (0.12) ​ $ (0.06) ​ $ (0.19)

DESCRIPTION OF BUSINESS AND S_3

DESCRIPTION OF BUSINESS AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Narrative (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2022 USD ($)	Dec. 31, 2021 USD ($)	Dec. 31, 2020 USD ($)
Gain (Loss) on Investments, Total	$ 0
Other than Temporary Impairment Losses, Investments, Total	0
Restricted Cash, Total			$ 3,500
Unbilled Receivables, Current	13,500	$ 11,800
Contract with Customer, Asset, Unbilled Receivables, Not Billable, Amount Expected to be Collected after Next Twelve Months	$ 800	$ 1,300
Finite-Lived Intangible Asset, Useful Life (Minimum in Years)	1 year
Finite-Lived Intangible Asset, Useful Life (Maximum in Years)	10 years
Number of Operating Segments	1
Number of Reporting Units	1
Capitalized Computer Software, Useful Life (Minimum in Years)	5 years
Capitalized Computer Software, Useful Life (Maximum in Years)	6 years
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period (Year)	4 years
Customer Concentration Risk [Member] | Accounts Receivable [Member]
Number of Major Customers	3	2
Customer Concentration Risk [Member] | Accounts Receivable [Member] | Two Customers [Member]
Concentration Risk, Percentage	53%	44%
Customer Concentration Risk [Member] | Revenue Benchmark [Member]
Number of Major Customers	2	2
Customer Concentration Risk [Member] | Revenue Benchmark [Member] | Two Customers [Member]
Concentration Risk, Percentage	41%
Customer Concentration Risk [Member] | Revenue Benchmark [Member] | One Customer [Member]
Concentration Risk, Percentage		27%

DESCRIPTION OF BUSINESS AND S_4

DESCRIPTION OF BUSINESS AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Allowance for Doubtful Accounts (Details) - SEC Schedule, 12-09, Allowance, Credit Loss [Member] - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Balance at Beginning of Period		$ 890	$ 963	$ 213
Charged Against Revenue	[1]			800
Deductions/ Write-offs of Accounts Receivable			(73)	(50)
Balance at End of Period		$ 890	$ 890	$ 963
[1] Additions to the accounts receivable reserve for doubtful accounts are charged to bad debt expense. Additions to the receivable reserve for billing adjustments are charged against revenue.

DESCRIPTION OF BUSINESS AND S_5

DESCRIPTION OF BUSINESS AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Estimated Useful Lives of Property and Equipment (Details)	12 Months Ended
	Dec. 31, 2022
Computer Equipment [Member]
Property, plant and equipment, useful life (Year)	3 years
Software and Software Development Costs [Member]
Property, plant and equipment, useful life (Year)	3 years
Furniture and Fixtures [Member] | Minimum [Member]
Property, plant and equipment, useful life (Year)	5 years
Furniture and Fixtures [Member] | Maximum [Member]
Property, plant and equipment, useful life (Year)	10 years
Laboratory and Test Equipment [Member] | Minimum [Member]
Property, plant and equipment, useful life (Year)	3 years
Laboratory and Test Equipment [Member] | Maximum [Member]
Property, plant and equipment, useful life (Year)	10 years
Leaseholds and Leasehold Improvements [Member]
Leasehold improvements useful life	Shorter of estimated useful life or term of lease

REVENUE (Details)

REVENUE (Details)	12 Months Ended				24 Months Ended
	Dec. 31, 2022 USD ($) item	Dec. 31, 2021 USD ($)	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)	Dec. 31, 2022 USD ($)
Number of revenue sources | item	2
Capitalized Contract Cost, Impairment Loss					$ 0
Contract with Customer, Liability, Revenue Recognized		$ 24,900,000	$ 16,900,000	$ 10,700,000
Revenue, Remaining Performance Obligation, Amount	$ 277,700,000				277,700,000
Contract with Customer, Performance Obligation Satisfied in Previous Period	400,000	(400,000)	100,000
Capitalized Contract Cost, Amortization	1,550,000	674,000	$ 549,000
Prepaid Expenses and Other Current Assets [Member]
Contract with Customer, Asset, after Allowance for Credit Loss, Current, Total	3,300,000	400,000			3,300,000
Capitalized Contract Cost, Net, Total	1,700,000	600,000			1,700,000
Other Noncurrent Assets [Member]
Capitalized Contract Cost, Net, Total	$ 2,100,000	$ 2,100,000			$ 2,100,000
Geographic Concentration Risk [Member] | Revenue Benchmark [Member]
Concentration Risk, Percentage	100%	100%	100%
Geographic Concentration Risk [Member] | Revenue Benchmark [Member] | Non-US [Member]
Concentration Risk, Percentage	50%	55%	58%

REVENUE - Additional informatio

REVENUE - Additional information (Details) - Software License and Related Services Agreement [Member] - Advantest America, Inc. [Member]	Dec. 31, 2022
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2022-01-01 | Minimum [Member]
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Period (Year)	2 years
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2024-01-01 | Maximum [Member]
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Period (Year)	3 years

REVENUE - Disaggregation of Rev

REVENUE - Disaggregation of Revenue (Details)	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Percent of revenues	100%	100%	100%
Transferred over Time [Member]
Percent of revenues	69%	65%	63%
Transferred at Point in Time [Member]
Percent of revenues	31%	35%	37%

STRATEGIC PARTNERSHIP AGREEME_2

STRATEGIC PARTNERSHIP AGREEMENT WITH ADVANTEST AND RELATED PARTY TRANSACTIONS (Details) - USD ($)			12 Months Ended
	Oct. 31, 2022	Jul. 29, 2020	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Proceeds from Issuance of Common Stock					$ 65,078,000
Deferred revenues - current portion			$ 26,019,000	$ 23,691,000
Strategic Partnership for Joint Development and Sales Technology Solutions
Stock Issued During Period, Shares, New Issues (in shares)		3,306,924
Proceeds from Issuance of Common Stock		$ 65,200,000
Amendment #1 to Software License & Related Services Agreement
Commitments from Advantest	$ 50,000,000
Commercial Agreement With Advantest
Related party receivables			300,000	0
Contract with Customer, Liability, Total			7,100,000	6,800,000
Material costs and expenses incurred			0	0
Commercial Agreement With Advantest | Analytics
Advantest analytics revenue			$ 10,300,000	$ 10,600,000	$ 3,400,000

BUSINESS COMBINATION - Narrativ

BUSINESS COMBINATION - Narrative (Details) - USD ($) $ in Thousands		3 Months Ended	12 Months Ended
	Dec. 01, 2020	Dec. 31, 2021	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Payments to Acquire Businesses, Net of Cash Acquired, Total				$ 3,054	$ 28,580
Increase (decrease) in goodwill due to the acquisition purchase price adjustment			$ 0	(1,651)	0
Cimetrix Incorporated [Member]
Business Combination, Consideration Transferred, Total	$ 37,500
Payments to Acquire Businesses, Net of Cash Acquired, Total	31,600
Business Combination, Holdback Amount	3,500
Business Combination, Acquired Receivables, Gross Contractual Amount	1,600
Business Combination, Estimated Cash Payout to Certain Employees	$ 1,400
Goodwill after purchase price adjustment			3,100
Increase (decrease) in deferred tax liabilities		$ (1,300)
Increase (decrease) in goodwill due to the acquisition purchase price adjustment		(1,700)
Business Combination, Acquisition Related Costs					$ 1,600
Cimetrix Incorporated [Member] | Accrued Compensation and Related Benefits [Member]
Business Combination, Accrued Estimated Cash Payout to Certain Employees		$ 500	$ 200	$ 500

BUSINESS COMBINATION - Fair Val

BUSINESS COMBINATION - Fair Values of Assets Acquired and Liabilities Assumed and the Related Useful Lives (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Finite-lived intangible assets, amortization period (Year)	1 year
Goodwill	$ 14,123	$ 14,123	$ 15,774	$ 2,293
Cimetrix Incorporated [Member]
Fair value of tangible assets (including cash of $5,900)		8,298
Goodwill		11,830
Total assets acquired		39,927
Accounts payable and accrued expenses		1,447
Deferred revenue		375
Operating lease liabilities		132
Deferred tax liabilities		439
Total liabilities assumed		2,393
Total purchase price allocation		37,534
Cimetrix Incorporated [Member] | In Process Research and Development [Member]
Fair value of indefinite-lived intangible assets		3,635
Developed Technology Rights [Member] | Cimetrix Incorporated [Member]
Fair value of cash		5,900
Fair value of finite-lived intangible assets		$ 12,541
Finite-lived intangible assets, amortization period (Year)		8 years
Customer Relationships [Member] | Cimetrix Incorporated [Member]
Fair value of finite-lived intangible assets		$ 1,967
Finite-lived intangible assets, amortization period (Year)		10 years
Noncompete Agreements [Member] | Cimetrix Incorporated [Member]
Fair value of finite-lived intangible assets		$ 848
Finite-lived intangible assets, amortization period (Year)		3 years
Trademarks and Trade Names [Member] | Cimetrix Incorporated [Member]
Fair value of finite-lived intangible assets		$ 808
Finite-lived intangible assets, amortization period (Year)		10 years

BUSINESS COMBINATION - Fair V_2

BUSINESS COMBINATION - Fair Values of Assets Acquired and Liabilities Assumed and the Related Useful Lives Other (Details) $ in Millions	Dec. 31, 2021 USD ($)
Developed Technology Rights [Member] | Cimetrix Incorporated [Member]
Fair value of cash	$ 5.9

PROPERTY AND EQUIPMENT - Narrat

PROPERTY AND EQUIPMENT - Narrative (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Write-down in value of property and equipment		$ 3,183
DFI Test Equipment [Member]
Construction in Progress, Gross	$ 22,200	20,000
Depreciation, Depletion and Amortization, Nonproduction, Total	$ 5,500	6,200	$ 6,700
Write-down in value of property and equipment		$ 3,200

PROPERTY AND EQUIPMENT - Proper

PROPERTY AND EQUIPMENT - Property and Equipment (Details) - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021
Property and equipment, gross	$ 86,369	$ 76,712
Less: accumulated depreciation and amortization	(46,195)	(41,417)
Total	40,174	35,295
Computer Equipment [Member]
Property and equipment, gross	11,853	11,924
Software and Software Development Costs [Member]
Property and equipment, gross	5,395	5,419
Furniture and Fixtures [Member]
Property and equipment, gross	2,484	2,506
Leasehold Improvements [Member]
Property and equipment, gross	6,467	6,272
Laboratory and Test Equipment [Member]
Property and equipment, gross	4,431	3,981
Test Equipment [Member]
Property and equipment, gross	28,403	24,452
Construction in Progress [Member]
Property and equipment, gross	$ 27,336	$ 22,158

GOODWILL AND INTANGIBLE ASSET_2

GOODWILL AND INTANGIBLE ASSETS - Narrative (Details) - USD ($)	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Goodwill	$ 14,123,000	$ 14,123,000	$ 15,774,000	$ 2,293,000
Net Carrying Amount, Total	$ 18,055,000	21,239,000
Finite-Lived Intangible Assets, Remaining Amortization Period (Year)	5 years 10 months 24 days
Amortization of Intangible Assets, Total	$ 3,484,000	3,334,000	1,446,000
Impairment of Intangible Assets, Finite-lived	0	0	0
Costs of Revenues
Amortization of Intangible Assets, Total	2,214,000	2,079,000	705,000
Costs and Expenses
Amortization of Intangible Assets, Total	$ 1,270,000	$ 1,255,000	$ 741,000

GOODWILL AND INTANGIBLE ASSET_3

GOODWILL AND INTANGIBLE ASSETS - Change in Carrying Amount of Goodwill (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
GOODWILL AND INTANGIBLE ASSETS
Balance at beginning of period	$ 14,123	$ 15,774	$ 2,293
Addition			13,481
Measurement period acquisition adjustment (1)	0	(1,651)	0
Balance at end of period	$ 14,123	$ 14,123	$ 15,774

GOODWILL AND INTANGIBLE ASSET_4

GOODWILL AND INTANGIBLE ASSETS - Intangible Assets (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Accumulated Amortization	$ (29,533)	$ (26,049)
Net Carrying Amount	18,055
Gross Carrying Amount, Total	47,588	47,288
Net Carrying Amount, Total	18,055	21,239
Customer Relationships [Member]
Gross Carrying Amount	9,407	9,407
Accumulated Amortization	(6,684)	(6,041)
Net Carrying Amount	$ 2,723	3,366
Customer Relationships [Member] | Minimum [Member]
Amortization Period (Year)	1 year
Customer Relationships [Member] | Maximum [Member]
Amortization Period (Year)	10 years
Developed Technology Rights [Member]
Gross Carrying Amount	$ 33,635	33,635
Accumulated Amortization	(19,647)	(17,250)
Net Carrying Amount	$ 13,988	16,385
Developed Technology Rights [Member] | Minimum [Member]
Amortization Period (Year)	4 years
Developed Technology Rights [Member] | Maximum [Member]
Amortization Period (Year)	9 years
Trademarks and Trade Names [Member]
Gross Carrying Amount	$ 1,598	1,598
Accumulated Amortization	(918)	(812)
Net Carrying Amount	$ 680	786
Trademarks and Trade Names [Member] | Minimum [Member]
Amortization Period (Year)	2 years
Trademarks and Trade Names [Member] | Maximum [Member]
Amortization Period (Year)	10 years
Patents [Member]
Gross Carrying Amount	$ 2,100	1,800
Accumulated Amortization	(1,696)	(1,640)
Net Carrying Amount	$ 404	160
Patents [Member] | Minimum [Member]
Amortization Period (Year)	6 years
Patents [Member] | Maximum [Member]
Amortization Period (Year)	10 years
Noncompete Agreements [Member]
Amortization Period (Year)	3 years
Gross Carrying Amount	$ 848	848
Accumulated Amortization	(588)	(306)
Net Carrying Amount	$ 260	$ 542

GOODWILL AND INTANGIBLE ASSET_5

GOODWILL AND INTANGIBLE ASSETS - Annual Amortization of Identifiable Intangible Assets (Details) $ in Thousands	Dec. 31, 2022 USD ($)
GOODWILL AND INTANGIBLE ASSETS
2023	$ 3,491
2024	3,093
2025	2,928
2026	2,759
2027	2,606
2028 and thereafter	3,178
Total future amortization expense	$ 18,055

LEASES - Other (Details)

LEASES - Other (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
LEASES
Operating Lease, Liability, Amount Related to Extension of Lease Term	$ 900
Operating Lease, Liability, Current	1,412	$ 1,758
Operating lease right of use assets decrease from early lease termination	500
Operating lease liability decrease from early lease termination	600
Lease termination gain	$ 100

LEASES - Lease Cost (Details)

LEASES - Lease Cost (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
LEASES
Operating lease expense	$ 1,457	$ 1,860	$ 1,828
Short-term lease and variable lease expense	1,032	822	545
Total lease expense	$ 2,489	$ 2,682	2,373
Weighted average remaining lease term under operating ROU leases (in years) (Year)	5 years 3 months 18 days	5 years 8 months 12 days
Weighted average discount rate for operating lease liabilities	4.87%	5.25%
Operating lease ROU assets obtained (in thousands)	$ 2,502	$ 161	$ 286

LEASES - Maturity of Operating

LEASES - Maturity of Operating Lease Liabilities (Details) $ in Thousands	Dec. 31, 2022 USD ($)
LEASES
2023	$ 1,570
2024	1,633
2025	1,547
2026	1,357
2027	1,294
2028 and thereafter	991
Total future minimum lease payments	8,392
Less: Interest (2)	(1,048)
Present value of future minimum lease payments under operating lease liabilities (3)	$ 7,344

COMMITMENTS AND CONTINGENCIES (

COMMITMENTS AND CONTINGENCIES (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2022 USD ($)
COMMITMENTS AND CONTINGENCIES
Future Lease payments	$ 8,392
Term of Product Warranty	90 days
Purchase Obligation, Total	$ 30,400
Threshold payment period	24 months

STOCKHOLDERS EQUITY (Details)

STOCKHOLDERS EQUITY (Details) - USD ($) $ / shares in Units, $ in Thousands					12 Months Ended			24 Months Ended
	Apr. 11, 2022	Jul. 30, 2020	Jun. 04, 2020	May 28, 2020	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2022
Proceeds from Issuance of Common Stock							$ 65,078
Treasury Stock, Value, Acquired, Cost Method					$ 22,471	$ 4,523
The 2018 Stock Repurchase Program [Member]
Treasury Stock, Shares, Acquired (in shares)				786,000
Treasury Stock Acquired, Average Cost Per Share (in dollars per share)				$ 12.43
Treasury Stock, Value, Acquired, Cost Method				$ 9,800
The 2020 Stock Repurchase Program [Member]
Treasury Stock, Shares, Acquired (in shares)					218,858	251,212		470,070
Treasury Stock Acquired, Average Cost Per Share (in dollars per share)					$ 26.40	$ 18.01		$ 21.91
Treasury Stock, Value, Acquired, Cost Method					$ 5,800	$ 4,500		$ 10,300
Stock Repurchase Program, Authorized Amount			$ 25,000
Stock Repurchase Program, Period in Force (Year)			2 years
Stock Repurchase Program 2022 [Member]
Treasury Stock, Shares, Acquired (in shares)					714,600
Treasury Stock Acquired, Average Cost Per Share (in dollars per share)					$ 23.36
Treasury Stock, Value, Acquired, Cost Method					$ 16,700
Stock Repurchase Program, Authorized Amount	$ 35,000
Stock Repurchase Program, Period in Force (Year)	2 years
Strategic Partnership for Joint Development and Sales Technology Solutions
Stock Issued During Period, Shares, New Issues (in shares)		3,306,924
Shares Issued, Price Per Share (in dollars per share)		$ 19.7085
Proceeds from Issuance of Common Stock		$ 65,200
Payments of Stock Issuance Costs		$ 100

EMPLOYEE BENEFIT PLANS - Other

EMPLOYEE BENEFIT PLANS - Other (Details)		1 Months Ended	12 Months Ended
	Jun. 15, 2021	Jul. 31, 2001 item	Dec. 31, 2022 USD ($) $ / shares shares	Dec. 31, 2021 USD ($) $ / shares shares	Dec. 31, 2020 USD ($) $ / shares shares	Dec. 31, 2019 shares
Share-based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Amount, Total | $			$ 100,000
Share-based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Period for Recognition (Year)			1 year
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period (Year)			4 years
Share-based Compensation Arrangement by Share-based Payment Award, Options, Cumulative Forfeitures of Plan (in shares)			6,000	10,000	57,000
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Number, Ending Balance (in shares)			68,000	226,000	456,000	745,000
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Gross (in shares)			0		24,000
Share-based Payment Arrangement, Amount Capitalized | $					$ 190,000
Share Price (in dollars per share) | $ / shares			$ 28.52
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period, Intrinsic Value | $			$ 2,300,000	$ 3,000,000	2,200,000
Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested in Period, Fair Value | $			100,000
Software Development [Member]
Share-based Payment Arrangement, Amount Capitalized | $			0	$ 0	$ 200,000
Restricted Stock Units (RSUs) [Member]
Share-based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Amount, Total | $			$ 32,700,000
Share-based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Period for Recognition (Year)			2 years 7 months 6 days
401(k) Savings Plan
Defined Contribution Plan, Employer Discretionary Contribution Amount | $			$ 1,600,000
401(k) Savings Plan | Minimum [Member]
Defined Contribution Plan, Percentage of Employee Gross Pay Match			50%
401(k) Savings Plan | Maximum [Member]
Defined Contribution Plan, Maximum Annual Contributions Per Employee, Percent			60%
Defined Contribution Plan, Percentage of Employee Gross Pay Match			100%
Defined Contribution Plan, Employer Matching Contribution, Percent of Match			4%
The 2010 Purchase Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Maximum Employee Subscription Rate		10%
Share-based Compensation Arrangement by Share-based Payment Award, Purchase Price of Common Stock, Percent		85%
Share-based Compensation Arrangement by Share-based Payment Award, Offering Period		24 months
Share-based Compensation Arrangement by Share-based Payment Award, Number of Purchase Period | item		4
Stock Issued During Period, Shares, Employee Stock Purchase Plans (in shares)			5,203	108,623	183,078
Employee Stock Purchase Plan Weighted Average Purchase Price of Shares Purchased (in dollars per share) | $ / shares			$ 13.40	$ 9.53	$ 9.12
Share-based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Amount, Total | $			$ 0
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period (Year)		6 months
The 2021 Purchase Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Offering Period	24 months
Stock Issued During Period, Shares, Employee Stock Purchase Plans (in shares)			182,083
Employee Stock Purchase Plan Weighted Average Purchase Price of Shares Purchased (in dollars per share) | $ / shares			$ 16.15
Share-based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Amount, Total | $			$ 1,100,000
Share-based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Period for Recognition (Year)			1 year
Share-based Compensation Arrangement by Share-based Payment Award, Expiration Period (Year)	10 years
Twenty Eleven Stock Incentive Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Expiration Period (Year)			10 years
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period (Year)			4 years
Common Stock, Capital Shares Reserved for Future Issuance (in shares)			12,800,000
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Available for Grant (in shares)			3,500,000
Number of additional common stock capital shares reserved for future issuance			13,300,000
Twenty Twenty-One Employee Stock Purchase Plan [Member]
Number Of ESPP Shares Available For Future Issuance (in shares)			817,917
Shares Previously Issued Under the 2001 Plan [Member]
Common Stock, Capital Shares Reserved for Future Issuance (in shares)			3,500,000
Share-based Compensation Arrangement by Share-based Payment Award, Options, Cumulative Forfeitures of Plan (in shares)			500,000
Outside of the 2011, 2001 or IDS Plans [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Number, Ending Balance (in shares)			0

EMPLOYEE BENEFIT PLANS - Stock

EMPLOYEE BENEFIT PLANS - Stock Options, Valuation Assumptions (Details) - $ / shares	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Twenty Eleven Stock Incentive Plan [Member]
Expected life (in years) (Year)			4 years 5 months 12 days
Volatility			40.90%
Risk-free interest rate			0.60%
Weighted average fair value per share of options granted during the period (in dollars per share)			$ 5.75
The 2021 Purchase Plan [Member]
Expected life (in years) (Year)	1 year 3 months	1 year 3 months
Volatility	48.73%	48%
Risk-free interest rate	2.75%	0.11%
Expected dividend	0%	0%
Weighted average fair value of purchase rights granted during the period (in dollars per share)	$ 10	$ 6.71
The 2010 Purchase Plan [Member]
Expected life (in years) (Year)	1 year 3 months
Volatility	34.25%
Risk-free interest rate	1.43%
Expected dividend	0%
Weighted average fair value of purchase rights granted during the period (in dollars per share)	$ 4.83

EMPLOYEE BENEFIT PLANS - Alloca

EMPLOYEE BENEFIT PLANS - Allocation of Recognized Period Costs (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Stock-based compensation expenses	$ 19,649	$ 12,931	$ 12,463
Costs of Revenues
Stock-based compensation expenses	2,974	2,563	3,454
Research and Development Expense [Member]
Stock-based compensation expenses	9,391	5,515	4,800
Selling, General and Administrative Expenses [Member]
Stock-based compensation expenses	$ 7,284	$ 4,853	$ 4,209

EMPLOYEE BENEFIT PLANS - Stoc_2

EMPLOYEE BENEFIT PLANS - Stock Options Activity (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
EMPLOYEE BENEFIT PLANS
Outstanding, beginning balance (in shares)	226,000	456,000	745,000
Granted (in shares)	0		24,000
Exercised (in shares)	(150,000)	(216,000)	(246,000)
Canceled (in shares)	(6,000)	(10,000)	(57,000)
Expired (in shares)	(2,000)	(4,000)	(10,000)
Outstanding, ending balance (in shares)	68,000	226,000	456,000
Vested and expected to vest (in shares)	68,000
Exercisable (in shares)	57,000
Outstanding, weighted average exercise price, beginning balance (in dollars per share)	$ 12.78	$ 10.95	$ 10.64
Granted, weighted average exercise price (in dollars per share)			16.72
Exercised, weighted average exercise price (in dollars per share)	11.27	8.90	10.46
Canceled, weighted average exercise price (in dollars per share)	13.52	15.56	11.65
Expired, weighted average exercise price (in dollars per share)	8.79	6.90	10.06
Outstanding, weighted average exercise price, ending balance (in dollars per share)	16.11	$ 12.78	$ 10.95
Vested and expected to vest, weighted average exercise price (in dollars per share)	16.11
Exercisable, weighted average exercise price (in dollars per share)	$ 16.07
Outstanding, weighted average remaining contractual (Year)	4 years 10 months 20 days
Vested and expected to vest, weighted average remaining contractual term (Year)	4 years 10 months 13 days
Exercisable, weighted average remaining contractual term (Year)	4 years 5 months 15 days
Outstanding, aggregate intrinsic value	$ 847
Vested and expected to vest, aggregate intrinsic value	842
Exercisable, aggregate intrinsic value	$ 706

EMPLOYEE BENEFIT PLANS - Nonves

EMPLOYEE BENEFIT PLANS - Nonvested Restricted Stock Units Activity (Details) - Restricted Stock Units (RSUs) [Member] - $ / shares shares in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Nonvested, Opening Balance (in shares)	1,872	1,747	1,887
Granted (in shares)	1,210	977	890
Vested (in shares)	(862)	(689)	(867)
Forfeited (in shares)	(96)	(163)	(163)
Nonvested, Ending Balance (in shares)	2,124	1,872	1,747
Nonvested, weighted average grant date fair value (in dollars per share)	$ 18.24	$ 16.33	$ 12.30
Granted, weighted average grant date fair value (in dollars per share)	23.23	19.43	21.31
Vested, weighted average grant date fair value (in dollars per share)	17.57	15.23	13.25
Forfeited, weighted average grant date fair value (in dollars per share)	19.71	17.63	13.23
Nonvested, weighted average grant date fair value (in dollars per share)	$ 21.29	$ 18.24	$ 16.33

INCOME TAXES (Details)

INCOME TAXES (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
INCOME TAXES
Income Tax Expense (Benefit), Total	$ 3,899	$ 3,171	$ 22,303
Unrecognized Tax Benefits, Ending Balance	15,109	14,743	14,300	$ 13,615
Unrecognized Tax Benefits that Would Impact Effective Tax Rate	2,000
Unrecognized tax benefits including income tax penalties and interest accrued in long term liabilities	2,600
Unrecognized tax benefits related to income tax penalties and interest accrued in long-term liabilities	700	700	$ 800
Unrecognized tax benefits, penalties and interest	700
Deferred Tax Assets, Valuation Allowance, Total	$ 59,215	$ 51,586

INCOME TAXES - Income Tax Expen

INCOME TAXES - Income Tax Expense (Benefit) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Total income tax expense	$ 3,899	$ 3,171	$ 22,303
U.S.
Current	1,210	(67)	(1,325)
Deferred	13	1,318	21,056
Foreign
Current	577	237	238
Withholding	2,111	1,591	2,392
Deferred	$ (12)	$ 92	$ (58)

INCOME TAXES - Income Tax Recon

INCOME TAXES - Income Tax Reconciliation (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
INCOME TAXES
Federal statutory tax provision	$ 106	$ (3,847)	$ (3,793)
State tax provision	949	239	703
Stock compensation expense	(898)	(499)	(602)
Tax credits	(2,877)	(2,676)	(3,488)
Foreign tax, net	2,195	1,653	2,443
Foreign-derived intangible income (FDII) deduction	(830)
Change in valuation allowance	5,122	8,099	29,034
Unrealized tax benefit reserve changes	136	(151)
Business combination costs			356
Tax law changes			(2,237)
Other	(4)	353	(113)
Total income tax expense	$ 3,899	$ 3,171	$ 22,303

INCOME TAXES - Deferred Tax Ass

INCOME TAXES - Deferred Tax Assets (Details) - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021
Deferred tax assets:
Net operating loss carry forward	$ 3,861	$ 13,149
Research and development and other credit carry forward	28,046	26,591
Foreign tax credit carry forward	11,764	11,010
Capitalized research and experimental expenses	10,069	0
Accruals deductible in different periods	7,713	3,362
Leases	1,623	1,472
Stock-based compensation	1,948	1,442
Total deferred tax assets	65,024	57,026
Less: valuation allowance	(59,215)	(51,586)
Deferred tax assets, net of valuation allowance	5,809	5,440
Deferred tax liabilities
Property and equipment, net	(540)	178
Operating lease right-of-use assets	(1,635)	(1,472)
Intangible assets	(3,617)	(4,129)
Deferred tax liabilities	(5,792)	(5,423)
Net deferred tax assets	$ 17	$ 17

INCOME TAXES - Unrecognized Tax

INCOME TAXES - Unrecognized Tax Benefits (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
INCOME TAXES
Gross unrecognized tax benefits, Beginning Balance	$ 14,743	$ 14,300	$ 13,615
Increases in tax positions for current year	988	853	1,024
Increases in tax positions for prior years	0	1	71
Lapse in statute of limitations	(622)	(411)	(410)
Gross unrecognized tax benefits, Ending Balance	$ 15,109	$ 14,743	$ 14,300

INCOME TAXES - Narrative (Detai

INCOME TAXES - Narrative (Details) - USD ($)	12 Months Ended			24 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2022	Dec. 31, 2019
Income (Loss) from Continuing Operations before Income Taxes, Domestic	$ 1,200,000	$ 19,700,000	$ (18,400,000)
Income (Loss) from Continuing Operations before Income Taxes, Foreign	1,700,000	1,400,000	300,000
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent				21%
Deferred Tax Assets, Valuation Allowance, Total	59,215,000	51,586,000		$ 59,215,000
Deferred Tax Assets, Net, Total	17,000	17,000		17,000
Unrecognized tax benefits related to income tax penalties and interest accrued in long-term liabilities	700,000	700,000	800,000	700,000
Unrecognized Tax Benefits, Income Tax Penalties and Interest Expense (Reversal)	(61,000)	(89,000)	33,000
Unrecognized Tax Benefits, Ending Balance	15,109,000	14,743,000	$ 14,300,000	15,109,000	$ 13,615,000
Unrecognized Tax Benefits that Would Impact Effective Tax Rate	2,000,000			2,000,000
Unrecognized tax benefits including income tax penalties and interest accrued in long term liabilities	2,600,000			2,600,000
Unrecognized Tax Benefits In Deferred Tax Asset Subject To Full Valuation Allowance	13,200,000			13,200,000
California R&D Tax Credits [Member]
Deferred Tax Assets, Valuation Allowance, Total	59,200,000	$ 51,600,000		59,200,000
U.S.
Tax Credit Carryforward, Amount	21,800,000			21,800,000
U.S. | Internal Revenue Service (IRS) [Member]
Operating Loss Carryforwards, Total	9,900,000			9,900,000
U.S. | California Franchise Tax Board [Member]
Operating Loss Carryforwards, Total	11,200,000			11,200,000
State and Local
Tax Credit Carryforward, Amount	$ 22,800,000			$ 22,800,000

INCOME TAXES - Valuation Allowa

INCOME TAXES - Valuation Allowance of Deferred Tax Assets (Details) - SEC Schedule, 12-09, Valuation Allowance, Deferred Tax Asset [Member] - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Balance at Beginning of Period	$ 51,586	$ 41,859	$ 10,486
Charged to Expense	7,629	9,727	31,373
Balance at End of Period	$ 59,215	$ 51,586	$ 41,859

NET LOSS PER SHARE - Calculatio

NET LOSS PER SHARE - Calculation of Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2022	Sep. 30, 2022	Jun. 30, 2022	Mar. 31, 2022	Dec. 31, 2021	Sep. 30, 2021	Jun. 30, 2021	Mar. 31, 2021	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
NET LOSS PER SHARE
Net loss	$ 483	$ 1,385	$ (1,147)	$ (4,150)	$ (7,000)	$ (2,407)	$ (4,484)	$ (7,597)	$ (3,429)	$ (21,488)	$ (40,363)
Basic weighted-average shares outstanding (in shares)									37,309	37,138	34,458
Diluted weighted-average shares outstanding (in shares)									37,309	37,138	34,458
Basic (in dollars per share)	$ 0.01	$ 0.04	$ (0.03)	$ (0.11)	$ (0.19)	$ (0.06)	$ (0.12)	$ (0.21)	$ (0.09)	$ (0.58)	$ (1.17)
Diluted (in dollars per share)	$ 0.01	$ 0.04	$ (0.03)	$ (0.11)	$ (0.19)	$ (0.06)	$ (0.12)	$ (0.21)	$ (0.09)	$ (0.58)	$ (1.17)

NET LOSS PER SHARE - Anti-dilut

NET LOSS PER SHARE - Anti-dilutive Securities (Details) - shares shares in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Anti-dilutive securities (in shares)	927	1,171	1,413
Share-based Payment Arrangement, Option [Member]
Anti-dilutive securities (in shares)	56	170	332
Restricted Stock Units (RSUs) [Member]
Anti-dilutive securities (in shares)	787	968	921
Employee Stock Purchase Plan [Member]
Anti-dilutive securities (in shares)	84	33	160

CUSTOMER AND GEOGRAPHIC INFOR_3

CUSTOMER AND GEOGRAPHIC INFORMATION - Other (Details)	12 Months Ended
	Dec. 31, 2022
CUSTOMER AND GEOGRAPHIC INFORMATION
Number of Operating Segments	1
Number of Reportable Segments	1

CUSTOMER AND GEOGRAPHIC INFOR_4

CUSTOMER AND GEOGRAPHIC INFORMATION - Revenue Percentage by Major Customers (Details) - Customer Concentration Risk [Member]	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Revenue Benchmark [Member] | Customer A [Member]
Concentration risk	31%	17%
Revenue Benchmark [Member] | Customer B [Member]
Concentration risk	10%
Revenue Benchmark [Member] | Customer D [Member]
Concentration risk		10%
Revenue Benchmark [Member] | Customer E [Member]
Concentration risk			23%
Accounts Receivable [Member] | Customer A [Member]
Concentration risk	29%	29%
Accounts Receivable [Member] | Customer B [Member]
Concentration risk	12%	15%
Accounts Receivable [Member] | Customer C [Member]
Concentration risk	12%

CUSTOMER AND GEOGRAPHIC INFOR_5

CUSTOMER AND GEOGRAPHIC INFORMATION - Revenues by Geographic Area (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2022	Sep. 30, 2022	Jun. 30, 2022	Mar. 31, 2022	Dec. 31, 2021	Sep. 30, 2021	Jun. 30, 2021	Mar. 31, 2021	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Revenues	$ 40,523	$ 39,860	$ 34,668	$ 33,498	$ 29,886	$ 29,555	$ 27,419	$ 24,200	$ 148,549	$ 111,060	$ 88,046
Geographic Concentration Risk [Member] | Revenue Benchmark [Member]
Revenues									$ 148,549	$ 111,060	$ 88,046
Concentration risk									100%	100%	100%
Geographic Concentration Risk [Member] | Revenue Benchmark [Member] | UNITED STATES
Revenues									$ 73,625	$ 50,374	$ 36,723
Concentration risk									50%	45%	42%
Geographic Concentration Risk [Member] | Revenue Benchmark [Member] | CHINA
Revenues									$ 24,494	$ 14,267	$ 13,776
Concentration risk									16%	13%	16%
Geographic Concentration Risk [Member] | Revenue Benchmark [Member] | JAPAN
Revenues									$ 13,916	$ 11,097	$ 4,762
Concentration risk									9%	10%	5%
Geographic Concentration Risk [Member] | Revenue Benchmark [Member] | Rest of the World [Member]
Revenues									$ 36,514	$ 35,322	$ 32,785
Concentration risk									25%	32%	37%

CUSTOMER AND GEOGRAPHIC INFOR_6

CUSTOMER AND GEOGRAPHIC INFORMATION - Long-lived Assets by Geographic Area (Details) - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021
Long-lived assets, net	$ 46,176	$ 40,703
UNITED STATES
Long-lived assets, net	44,730	39,158
Rest of the World [Member]
Long-lived assets, net	$ 1,446	$ 1,545

FINANCIAL INSTRUMENTS - Fair Va

FINANCIAL INSTRUMENTS - Fair Value, Assets Measured on a Recurring Basis (Details) - USD ($) $ in Thousands	Dec. 31, 2022		Dec. 31, 2021
Total	$ 97,285		$ 125,016
Fair Value, Inputs, Level 1 [Member]
Total	97,285		125,016
Money Market Funds [Member]
Money market mutual funds	75,738		12,474
Money Market Funds [Member] | Fair Value, Inputs, Level 1 [Member]
Money market mutual funds	75,738		12,474
US Government Corporations and Agencies Securities [Member]
Money market mutual funds	1,990
Short-term investments	19,557	[1]	112,542
US Government Corporations and Agencies Securities [Member] | Fair Value, Inputs, Level 1 [Member]
Money market mutual funds	1,990
Short-term investments	$ 19,557	[1]	$ 112,542
[1] The carrying amount of the Company’s investments in U.S. Government securities approximate fair value due to their short-term maturities, and there have been no events or changes in circumstances that would have had a significant effect on the fair value of these securities at December 31, 2022 and 2021.

FINANCIAL INSTRUMENTS - Other (

FINANCIAL INSTRUMENTS - Other (Details)	12 Months Ended
	Dec. 31, 2022 USD ($) item	Dec. 31, 2020 USD ($)
Foreign Exchange Contract [Member]
Derivative, Gain on Derivative	$ 0
Derivative, Loss on Derivative	$ 0	$ 200,000
Forward Contracts [Member]
Derivative, Number of Instruments Held | item	0

SELECTED QUARTERLY FINANCIAL _3

SELECTED QUARTERLY FINANCIAL DATA (UNAUDITED) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2022	Sep. 30, 2022	Jun. 30, 2022	Mar. 31, 2022	Dec. 31, 2021	Sep. 30, 2021	Jun. 30, 2021	Mar. 31, 2021	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
SELECTED QUARTERLY FINANCIAL DATA (UNAUDITED)
Revenues	$ 40,523	$ 39,860	$ 34,668	$ 33,498	$ 29,886	$ 29,555	$ 27,419	$ 24,200	$ 148,549	$ 111,060	$ 88,046
Costs of revenues	11,791	12,545	12,042	11,529	11,675	11,070	10,785	10,663	47,907	44,193	36,765
Net loss	$ 483	$ 1,385	$ (1,147)	$ (4,150)	$ (7,000)	$ (2,407)	$ (4,484)	$ (7,597)	$ (3,429)	$ (21,488)	$ (40,363)
Basic (in dollars per share)	$ 0.01	$ 0.04	$ (0.03)	$ (0.11)	$ (0.19)	$ (0.06)	$ (0.12)	$ (0.21)	$ (0.09)	$ (0.58)	$ (1.17)
Diluted (in dollars per share)	$ 0.01	$ 0.04	$ (0.03)	$ (0.11)	$ (0.19)	$ (0.06)	$ (0.12)	$ (0.21)	$ (0.09)	$ (0.58)	$ (1.17)