Axcelis (ACLS) 10-Q 6 May 21 2021 Q1 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	3 Months Ended
	Mar. 31, 2021	May 03, 2021
Document and Entity Information
Document Type	10-Q
Document Quarterly Report	true
Document Transition Report	false
Document Period End Date	Mar. 31, 2021
Entity File Number	000-30941
Entity Registrant Name	AXCELIS TECHNOLOGIES INC
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	34-1818596
Entity Address, Address Line One	108 Cherry Hill Drive
Entity Address, City or Town	Beverly
Entity Address, State or Province	MA
Entity Address, Postal Zip Code	01915
City Area Code	978
Local Phone Number	787-4000
Title of 12(b) Security	Common Stock, $0.001 par value
Trading Symbol	ACLS
Security Exchange Name	NASDAQ
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		33,599,897
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2021
Document Fiscal Period Focus	Q1
Entity Central Index Key	0001113232
Amendment Flag	false

Consolidated Statements of Oper

Consolidated Statements of Operations - USD ($) shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Revenue:
Revenue	$ 132,776	$ 118,991
Cost of revenue:
Cost of revenue	76,341	73,442
Gross profit	56,435	45,549
Operating expenses:
Research and development	15,685	14,606
Sales and marketing	10,387	8,204
General and administrative	10,013	9,036
Total operating expenses	36,085	31,846
Income from operations	20,350	13,703
Other (expense) income:
Interest income	33	482
Interest expense	(1,029)	(1,303)
Other, net	(1,153)	(620)
Total other expense	(2,149)	(1,441)
Income before income taxes	18,201	12,262
Income tax provision	1,721	1,041
Net income	$ 16,480	$ 11,221
Net income per share:
Basic	$ 0.49	$ 0.34
Diluted	$ 0.48	$ 0.33
Shares used in computing net income per share:
Basic weighted average common shares	33,715	32,872
Diluted weighted average common shares	34,643	34,057
Product
Revenue:
Revenue	$ 126,609	$ 112,133
Cost of revenue:
Cost of revenue	70,334	67,172
Services
Revenue:
Revenue	6,167	6,858
Cost of revenue:
Cost of revenue	$ 6,007	$ 6,270

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Consolidated Statements of Comprehensive Income
Net income	$ 16,480	$ 11,221
Other comprehensive loss:
Foreign currency translation adjustments	(1,372)	(1,112)
Amortization of actuarial loss and other adjustments from pension plan, net of tax	20	57
Total other comprehensive loss	(1,352)	(1,055)
Comprehensive income	$ 15,128	$ 10,166

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Current assets:
Cash and cash equivalents	$ 206,766	$ 203,479
Accounts receivable, net	75,932	86,865
Inventories, net	174,381	161,076
Prepaid expenses and other current assets	22,513	19,371
Total current assets	479,592	470,791
Property, plant and equipment, net	30,459	29,840
Operating lease assets	4,213	4,542
Finance lease assets, net	20,216	20,544
Long-term restricted cash	753	753
Deferred income taxes	54,936	57,851
Other assets	39,123	40,303
Total assets	629,292	624,624
Current liabilities:
Accounts payable	40,476	24,013
Accrued compensation	8,573	24,562
Warranty	4,181	4,280
Income taxes	648	654
Deferred revenue	20,417	21,221
Current portion of finance lease obligation	809	756
Other current liabilities	8,774	8,945
Total current liabilities	83,878	84,431
Long-term finance lease obligation	47,167	47,393
Long-term deferred revenue	1,725	1,837
Other long-term liabilities	8,862	9,361
Total liabilities	141,632	143,022
Commitments and contingencies (Note 16)
Stockholders' equity:
Common stock, $0.001 par value, 75,000 shares authorized; 33,679 shares issued and outstanding at March 31, 2021; 33,633 shares issued and outstanding at December 31, 2020	34	34
Additional paid-in capital	567,199	570,102
Accumulated deficit	(81,656)	(91,969)
Accumulated other comprehensive income	2,083	3,435
Total stockholders' equity	487,660	481,602
Total liabilities and stockholders' equity	$ 629,292	$ 624,624

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - $ / shares shares in Thousands	Mar. 31, 2021	Dec. 31, 2020
Consolidated Balance Sheets
Common stock, par value (in dollars per share)	$ 0.001	$ 0.001
Common stock, shares authorized	75,000	75,000
Common stock, shares issued	33,679	33,633
Common stock, shares outstanding	33,679	33,633

Consolidated Statements of Stoc

Consolidated Statements of Stockholders' Equity - USD ($) shares in Thousands, $ in Thousands	Common Stock	Additional Paid-in Capital	Accumulated Deficit	Accumulated Other Comprehensive Income (Loss)	Total
Balance (in shares) at Dec. 31, 2019	32,585
Balance at Dec. 31, 2019	$ 33	$ 559,878	$ (140,226)	$ (258)	$ 419,427
Increase (Decrease) in Stockholders' Equity
Net income			11,221		11,221
Foreign currency translation adjustments				(1,112)	(1,112)
Change in pension obligation, net of tax				57	57
Exercise of stock options (in shares)	540
Exercise of stock options	$ 1	4,498			4,499
Issuance of shares under Employee Stock Purchase Plan (in shares)	1
Issuance of shares under Employee Stock Purchase Plan		19			19
Issuance of restricted common shares (in shares)	69
Issuance of restricted common shares		(1,162)			(1,162)
Stock-based compensation expense		1,724			1,724
Repurchase of common stock (in shares)	(358)
Repurchase of common stock	$ (1)	(5,775)	(1,725)		(7,501)
Balance (in shares) at Mar. 31, 2020	32,837
Balance at Mar. 31, 2020	$ 33	559,182	(130,730)	(1,313)	427,172
Balance (in shares) at Dec. 31, 2020	33,633
Balance at Dec. 31, 2020	$ 34	570,102	(91,969)	3,435	481,602
Increase (Decrease) in Stockholders' Equity
Net income			16,480		16,480
Foreign currency translation adjustments				(1,372)	(1,372)
Change in pension obligation, net of tax				20	20
Exercise of stock options (in shares)	268
Exercise of stock options		2,512			2,512
Issuance of restricted common shares (in shares)	81
Issuance of restricted common shares		(2,354)			(2,354)
Stock-based compensation expense		2,407			2,407
Repurchase of common stock (in shares)	(303)
Repurchase of common stock		(5,468)	(6,167)		(11,635)
Balance (in shares) at Mar. 31, 2021	33,679
Balance at Mar. 31, 2021	$ 34	$ 567,199	$ (81,656)	$ 2,083	$ 487,660

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Cash flows from operating activities
Net income	$ 16,480	$ 11,221
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	2,645	2,363
Deferred income taxes	1,613	899
Stock-based compensation expense	2,407	1,724
Provision for excess and obsolete inventory	984	802
Changes in operating assets and liabilities:
Accounts receivable	10,431	19,223
Inventories	(16,503)	1,924
Prepaid expenses and other current assets	(3,325)	(4,435)
Accounts payable and other current liabilities	(1,008)	1,689
Deferred revenue	(909)	4,859
Income taxes	2	53
Other assets and liabilities	2,281	(645)
Net cash provided by operating activities	15,098	39,677
Cash flows from investing activities
Expenditures for property, plant and equipment and capitalized software	(1,347)	(1,290)
Net cash used in investing activities	(1,347)	(1,290)
Cash flows from financing activities
Net settlement on restricted stock grants	(2,354)	(1,162)
Repurchase of common stock	(11,635)	(7,501)
Proceeds from Employee Stock Purchase Plan		19
Principal payments on finance lease obligation	(175)
Proceeds from exercise of stock options	2,512	4,499
Net cash used in financing activities	(11,652)	(4,145)
Effect of exchange rate changes on cash and cash equivalents	1,188	640
Net increase in cash, cash equivalents and restricted cash	3,287	34,882
Cash, cash equivalents and restricted cash at beginning of period	204,232	146,534
Cash, cash equivalents and restricted cash at end of period	$ 207,519	$ 181,416

Nature of Business

Nature of Business	3 Months Ended
	Mar. 31, 2021
Nature of Business
Nature of Business	Note 1. Nature of Business ​ Axcelis Technologies, Inc. (“Axcelis” or the “Company”) was incorporated in Delaware in 1995, and is a producer of ion implantation equipment used in the fabrication of semiconductor chips in the United States, Europe and Asia. In addition, we provide extensive worldwide aftermarket service and support, including spare parts, equipment upgrades, used equipment and maintenance services to the semiconductor industry. ​ The accompanying unaudited consolidated financial statements have been prepared in accordance with U.S. generally accepted accounting principles for interim financial information and with the instructions to Form 10-Q and Article 10 of Regulation S-X. Accordingly, they do not include all of the information and footnotes required by generally accepted accounting principles for complete financial statements. In the opinion of management, all adjustments which are of a normal recurring nature and considered necessary for a fair presentation of these financial statements have been included. Operating results for the interim periods presented are not necessarily indicative of the results that may be expected for other interim periods or for the year as a whole. ​ The balance sheet at December 31, 2020 has been derived from the audited consolidated financial statements at that date but does not include all of the information and footnotes required by generally accepted accounting principles for complete financial statements. For further information, refer to the consolidated financial statements and footnotes thereto included in Axcelis Technologies, Inc.’s Annual Report on Form 10-K for the year ended December 31, 2020.

Stock Based Compensation

Stock Based Compensation	3 Months Ended
	Mar. 31, 2021
Stock Based Compensation
Stock Based Compensation	Note 2. Stock-Based Compensation ​ We maintain the Axcelis Technologies, Inc. 2012 Equity Incentive Plan, as amended (the “2012 Equity Plan”), which became effective on May 2, 2012, and permits the issuance of options, restricted stock, restricted stock units (“RSUs”) and performance awards to selected employees, directors and consultants of the Company. Our 2000 Stock Plan (the “2000 Stock Plan”) expired on May 1, 2012 and no new grants may be made under that plan after that date. However, unexpired options granted under the 2000 Stock Plan, which have a ​ The 2012 Equity Plan is more fully described in Note 13 to the consolidated financial statements in our Annual Report on Form 10-K for the year ended December 31, 2020. ​ We recognized stock-based compensation expense of $2.4 million and $1.7 million for the three-month periods ended March 31, 2021 and 2020, respectively. These amounts include compensation expense related to RSUs and non-qualified stock options. ​ In the three-month periods ended March 31, 2021 and 2020, we issued 0.3 million and 0.6 million shares of common stock, respectively, upon stock option exercises and vesting of RSUs. In the three-month periods ended March 31, 2021 and 2020, we received proceeds of $2.5 million and $4.5 million, respectively, in connection with the exercise of stock options. ​

Leases

Leases	3 Months Ended
	Mar. 31, 2021
Leases
Leases	Note 3. Leases ​ We have operating leases for office space, warehouse space, computer and office equipment and vehicles used in our business operations. We have a finance lease as a result of the 2015 sale-leaseback of our corporate headquarters in Beverly, Massachusetts. All new agreements are reviewed to determine if they contain a lease component. A lease is a contract or part of a contract that conveys the right to control the use of identified property, plant or equipment for a period of time in exchange for consideration. We recognize the lease obligation on a discounted basis using the explicit or implicit discount rate stated within the agreement. We recognize a corresponding right-of-use asset, which is initially determined based upon the net present value of the associated liability and is adjusted for deferred costs and possible impairment, if any. For those lease agreements that do not indicate the applicable discount rate, we use our incremental borrowing rate. We have made the following policy elections: (i) operating leases with an initial term of 12 months or less are not recorded on the consolidated balance sheet; (ii) we recognize lease expense for operating leases on a straight-line basis over the lease term; and (iii) we account for lease components and non-lease components that are fixed payments as one component. Some of our operating leases include one or more options to renew, with renewal terms that can extend the respective lease term 1 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ March 31, ​ December 31, ​ ​ ​ Leases Classification ​ 2021 2020 ​ Assets ​ ​ (in thousands) ​ ​ Operating leases Operating lease assets ​ $ 4,213 ​ $ 4,542 ​ ​ ​ Finance lease Finance lease assets * ​ 20,216 ​ 20,544 ​ ​ ​ Total leased assets ​ ​ $ 24,429 ​ $ 25,086 ​ ​ ​ Liabilities ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Current ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Operating Other current liabilities ​ $ 2,387 ​ $ 2,573 ​ ​ ​ Finance Current portion of finance lease obligation ​ ​ 809 ​ ​ 756 ​ ​ ​ Noncurrent ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Operating Other long-term liabilities ​ ​ 1,812 ​ ​ 1,949 ​ ​ ​ Finance Finance lease obligation ​ 47,167 ​ 47,393 ​ ​ ​ Total lease liabilities ​ ​ $ 52,175 ​ $ 52,671 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ * Finance lease assets are recorded net of accumulated depreciation of $48.7 million and include $0.7 million of prepaid financing costs as of March 31, 2021. Finance lease assets are recorded net of accumulated depreciation of $48.4 million and include $0.7 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three months ended ​ ​ ​ ​ ​ March 31, ​ ​ ​ Lease cost Classification ​ 2021 2020 ​ Operating lease cost ​ ​ (in thousands) ​ Service Cost of revenue ​ $ 639 ​ $ 550 ​ ​ ​ Research and development Operating expenses ​ 130 ​ 81 ​ ​ ​ Sales and marketing* Operating expenses ​ 378 ​ 332 ​ ​ ​ General and administrative* Operating expenses ​ 260 ​ 215 ​ ​ ​ Total operating lease cost ​ ​ $ 1,407 ​ $ 1,178 ​ ​ ​ Finance lease cost ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Depreciation of leased assets Cost of revenue, R&D, Sales and marketing and G&A ​ $ 328 ​ $ 353 ​ ​ ​ Interest on lease liabilities Interest expense ​ 1,279 ​ 1,303 ​ ​ ​ Total finance lease cost ​ ​ $ 1,607 ​ $ 1,656 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total lease cost ​ ​ $ 3,014 ​ $ 2,834 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ * Sales and marketing and general and administrative expense also includes short-term lease and variable lease costs of approximately $0.4 million and $0.2 million for the three months ended March 31, 2021 and 2020, respectively. ​ ​ ​ ​ 1 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Finance ​ Operating Total Maturity of Lease Liabilities ​ Leases ​ Leases ​ Leases ​ ​ ​ (in thousands) ​ 2021 ​ $ 4,394 ​ $ 2,129 ​ $ 6,523 ​ 2022 ​ 5,980 ​ 1,673 ​ 7,653 ​ 2023 ​ 6,114 ​ 534 ​ 6,648 ​ 2024 ​ 6,252 ​ 126 ​ 6,378 ​ 2025 ​ ​ 5,930 ​ ​ 74 ​ ​ 6,004 ​ Thereafter ​ ​ 73,723 ​ ​ 145 ​ ​ 73,868 ​ Total lease payments ​ $ 102,393 ​ $ 4,681 ​ $ 107,074 ​ Less interest portion* ​ ​ (54,417) ​ ​ (482) ​ ​ (54,899) ​ Finance lease and operating lease obligations ​ $ 47,976 ​ $ 4,199 ​ $ 52,175 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ * Finance lease interest calculated using the implied interest rate; operating lease interest calculated using estimated corporate borrowing rate. ​ ​ ​ ​ ​ ​ ​ ​ ​ March 31, ​ Lease term and discount rate 2021 ​ Weighted-average remaining lease term (years): ​ ​ ​ ​ Operating leases ​ ​ 2.3 ​ Finance leases ​ 15.8 ​ Weighted-average discount rate: ​ ​ ​ ​ Operating leases ​ 4.5% ​ Finance leases ​ 10.5% ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three months ended ​ ​ ​ March 31, ​ Cash paid for amounts included in the measurement of lease liabilities 2021 ​ 2020 ​ ​ ​ (in thousands) ​ Operating cash outflows from operating leases ​ $ 1,407 ​ $ 1,178 ​ Operating cash outflows from finance leases ​ 1,279 ​ 1,422 ​ Financing cash outflows from finance leases ​ ​ 175 ​ ​ — ​ Operating lease assets obtained in exchange for operating lease liabilities ​ 791 ​ 765 ​ Finance lease assets obtained in exchange for new finance lease liabilities ​ $ — ​ $ — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​

Revenue

Revenue	3 Months Ended
	Mar. 31, 2021
Revenue.
Revenue	Note 4. Revenue ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three months ended ​ ​ March 31, ​ ​ 2021 ​ 2020 ​ ​ (in thousands) Systems ​ $ 80,991 ​ $ 82,338 Aftermarket ​ ​ 51,785 ​ ​ 36,653 Total Revenue ​ $ 132,776 ​ $ 118,991 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three months ended ​ ​ March 31, ​ ​ 2021 ​ 2020 ​ ​ ​ (in thousands) North America ​ $ 9,508 ​ $ 10,661 ​ Asia Pacific ​ ​ 103,391 ​ ​ 96,828 ​ Europe ​ ​ 19,877 ​ ​ 11,502 ​ Total Revenue ​ $ 132,776 ​ $ 118,991 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ March 31, ​ December 31, ​ ​ 2021 ​ 2020 ​ ​ (in thousands) Contract liabilities ​ $ 22,142 ​ $ 23,058 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three months ended ​ March 31, ​ ​ 2021 ​ 2020 ​ ​ (in thousands) Balance, beginning of the period ​ $ 23,058 ​ $ 29,251 Deferral of revenue ​ ​ 11,264 ​ ​ 9,799 Recognition of deferred revenue ​ ​ (12,180) ​ ​ (4,944) Balance, end of the period ​ $ 22,142 ​ $ 34,106 ​

Receivable and Allowance for Cr

Receivable and Allowance for Credit Losses	3 Months Ended
	Mar. 31, 2021
Receivable and Allowance for Credit Losses
Receivable and Allowance for Credit Losses	Note 5. Receivables and Allowances for Credit Losses ​ All trade receivables are reported on the Consolidated Balance Sheets at their amortized cost adjusted for any write-offs and net of allowances for credit losses. ​ Axcelis maintains an allowance for credit losses, which represent an estimate of expected losses over the remaining contractual life of its receivables considering current market conditions and estimates for supportable forecasts when appropriate. The estimate is a result of the Company’s ongoing assessments and evaluations of collectability, historical loss experience, and future expectations in estimating credit losses in its receivable portfolio. Axcelis uses historical loss experience rates and applies them to a related aging analysis while also considering customer and/or economic risk where appropriate. Determination of the proper amount of allowances requires management to exercise judgment about the timing, frequency and severity of credit losses that could materially affect the provision for credit losses and, as a result, net earnings. The allowance takes into consideration numerous quantitative and qualitative factors that include receivable type, historical loss experience, loss migration, delinquency trends, collection experience, current economic conditions, estimates for supportable forecasts, when appropriate, and credit risk characteristics. ​ Axcelis evaluates the credit risk of the customer when extending credit based on a combination of various financial and qualitative factors that may affect its customers’ ability to pay. These factors may include the customer’s financial condition, past payment experience, and credit bureau report, as well as the value of the underlying collateral. ​ Management performs detailed reviews of Axcelis’ receivables on a quarterly basis to assess the adequacy of the allowances and to determine if any impairment has occurred. Amounts determined to be uncollectable are charged directly against the allowances, while amounts recovered on previously written-off accounts increase the allowances. Changes to the allowances for credit losses are maintained through adjustments to the provision for credit losses, which are charged to current period earnings. ​ The following table shows changes of the allowances for credit losses related to trade receivables for the three months ended March 31, 2021 and 2020, respectively: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three months ended ​ ​ ​ March 31, ​ ​ ​ 2021 ​ 2020 ​ ​ ​ (in thousands) ​ Balance, beginning of period ​ $ — ​ $ 818 ​ Provision for credit losses ​ ​ — ​ ​ — ​ Charge-offs ​ ​ — ​ ​ (818) ​ Recoveries ​ ​ — ​ ​ — ​ Balance, end of period ​ $ — ​ $ — ​ ​

Computation of Net Earnings per

Computation of Net Earnings per Share	3 Months Ended
	Mar. 31, 2021
Computation of Net Earnings per Share
Computation of Net Earnings per Share	Note 6. Computation of Net Earnings per Share ​ Basic earnings per share is computed by dividing income available to common stockholders (the numerator) by the weighted-average number of common shares outstanding (the denominator) for the period. The computation of diluted earnings per share is similar to basic earnings per share, except that the denominator is increased by the number of additional common shares that would have been outstanding if the potentially dilutive common shares issuable on exercise of stock options and vesting of RSUs had been issued, calculated using the treasury stock method. ​ The components of net earnings per share are as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three months ended ​ ​ ​ March 31, ​ ​ 2021 2020 ​ ​ ​ ​ ​ ​ ​ ​ Net income available to common stockholders ​ $ 16,480 ​ $ 11,221 ​ Weighted average common shares outstanding used in computing basic income per share ​ 33,715 ​ 32,872 ​ Incremental options and RSUs ​ 928 ​ 1,185 ​ Weighted average common shares used in computing diluted net income per share ​ 34,643 ​ 34,057 ​ Net income per share ​ ​ ​ ​ ​ ​ ​ Basic ​ $ 0.49 ​ $ 0.34 ​ Diluted ​ $ 0.48 ​ $ 0.33 ​ ​ ​ Diluted weighted average common shares outstanding does not include 1,429 and 1,675 common equivalent shares issuable with respect to outstanding equity awards for the three-month periods ended March 31, 2021 and 2020, respectively, as their effect would have been anti-dilutive.

Accumulated Other Comprehensive

Accumulated Other Comprehensive Income	3 Months Ended
	Mar. 31, 2021
Accumulated Other Comprehensive Income
Accumulated Other Comprehensive Income	Note 7. Accumulated Other Comprehensive Income ​ The following table presents the changes in accumulated other comprehensive income, net of tax, by component, for the three months ended March 31, 2021: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Foreign Defined benefit ​ ​ ​ ​ currency ​ pension plan ​ Total ​ ​ (in thousands) Balance at December 31, 2020 ​ $ 3,945 ​ $ (510) ​ $ 3,435 ​ Other comprehensive loss and pension reclassification ​ (1,372) ​ 20 ​ (1,352) ​ Balance at March 31, 2021 ​ $ 2,573 ​ $ (490) ​ $ 2,083 ​ ​

Cash, cash equivalents and rest

Cash, cash equivalents and restricted cash	3 Months Ended
	Mar. 31, 2021
Cash, cash equivalents and restricted cash
Cash, cash equivalents and restricted cash	Note 8. Cash, cash equivalents and restricted cash ​ The following table provides a reconciliation of cash, cash equivalents, and restricted cash reported within the consolidated balance sheets to the total of the amounts shown in the statement of cash flows: ​ ​ ​ ​ ​ ​ ​ ​ ​ March 31, ​ December 31, ​ ​ 2021 ​ ​ 2020 ​ ​ (in thousands) ​ Cash and cash equivalents $ 206,766 ​ $ 203,479 ​ Long-term restricted cash ​ 753 ​ ​ 753 ​ Total cash, cash equivalents and restricted cash $ 207,519 ​ $ 204,232 ​ ​ As of March 31, 2021, we had $0.8 million in restricted cash representing the total of (i) cash collateral for a $0.7 million letter of credit relating to workers’ compensation insurance and (ii) a $0.1 million deposit relating to customs activity.

Inventories, net

Inventories, net	3 Months Ended
	Mar. 31, 2021
Inventories, net
Inventories, net	Note 9. Inventories, net ​ The components of inventories are as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ March 31, ​ December 31, ​ ​ 2021 2020 ​ ​ (in thousands) ​ Raw materials ​ $ 100,634 ​ $ 100,254 ​ Work in process ​ 34,283 ​ 33,867 ​ Finished goods (completed systems) ​ 39,464 ​ 26,955 ​ Inventories, net ​ $ 174,381 ​ $ 161,076 ​ ​ When recorded, inventory reserves reduce the carrying value of inventories to their net realizable value. We establish inventory reserves when conditions exist that indicate inventory may be in excess of anticipated demand or is obsolete based upon assumptions about future demand for the Company’s products or market conditions. We regularly evaluate the ability to realize the value of inventories based on a combination of factors including the following: forecasted sales or usage, estimated product end of life dates, estimated current and future market value and new product introductions. Purchasing and usage alternatives are also explored to mitigate inventory exposure.

Product Warranty

Product Warranty	3 Months Ended
	Mar. 31, 2021
Product Warranty
Product Warranty	Note 10. Product Warranty ​ We generally offer a one-year warranty for all of our systems, the terms and conditions of which vary depending upon the product sold. For all systems sold, we accrue a liability for the estimated cost of standard warranty at the time of system shipment and defer the portion of systems revenue attributable to the fair value of non-standard warranty. Costs for non-standard warranty are expensed as incurred. Factors that affect our warranty liability include the number of installed units, historical and anticipated product failure rates, material usage and service labor costs. We periodically assess the adequacy of our recorded liability and adjust the amount as necessary. ​ The changes in our standard product warranty liability are as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three months ended ​ ​ ​ March 31, ​ ​ 2021 2020 ​ ​ (in thousands) ​ Balance at January 1 (beginning of year) ​ $ 4,612 ​ $ 3,244 ​ Warranties issued during the period ​ 1,288 ​ 1,385 ​ Settlements made during the period ​ (968) ​ (950) ​ Changes in estimate of liability for pre-existing warranties during the period ​ (192) ​ 126 ​ Balance at March 31 (end of period) ​ $ 4,740 ​ $ 3,805 ​ ​ ​ ​ ​ ​ ​ ​ ​ Amount classified as current ​ $ 4,181 ​ $ 3,431 ​ Amount classified as long-term ​ 559 ​ 374 ​ Total warranty liability ​ $ 4,740 ​ $ 3,805 ​ ​

Fair Value Measurements

Fair Value Measurements	3 Months Ended
	Mar. 31, 2021
Fair Value Measurements
Fair Value Measurements	Note 11. Fair Value Measurements ​ Certain assets on our balance sheets are reported at their fair value. Fair value is defined as the price that would be received for an asset or paid to transfer a liability (an exit price) in the principal or most advantageous market for the asset or liability in an orderly transaction between market participants on the measurement date. ​ (a) Fair Value Hierarchy ​ The accounting guidance for fair value measurement requires an entity to maximize the use of observable inputs and minimize the use of unobservable inputs when measuring fair value. The standard establishes a fair value hierarchy based on the level of independent, objective evidence surrounding the inputs used to measure fair value. A financial instrument’s categorization within the fair value hierarchy is based upon the lowest level of input that is significant to the fair value measurement. The fair value hierarchy is as follows: ​ Level 1 ​ Level 2 ​ Level 3 ​ (b) Fair Value Measurements ​ Our money market funds and short-term investments are included in cash and cash equivalents in the consolidated balance sheets. ​ The following table sets forth our assets by level within the fair value hierarchy: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ March 31, 2021 ​ ​ Fair Value Measurements ​ Level 1 Level 2 Level 3 Total ​ ​ (in thousands) Assets ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Cash equivalents: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Money market funds, U.S. Government Securities and Agency Investments ​ $ 174,752 ​ $ — ​ $ — ​ $ 174,752 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, 2020 ​ ​ Fair Value Measurements ​ Level 1 Level 2 Level 3 Total ​ ​ (in thousands) Assets ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Cash equivalents: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Money market funds, U.S. Government Securities and Agency Investments ​ $ 172,119 ​ $ — ​ $ — ​ $ 172,119 ​ ​ (c) Other Financial Instruments ​ The carrying amounts reflected in the consolidated balance sheets for accounts receivable, prepaid expenses and other current assets and non-current assets, restricted cash, accounts payable and accrued expenses approximate fair value due to their short-term maturities.

Financing Arrangements

Financing Arrangements	3 Months Ended
	Mar. 31, 2021
Financing Arrangements
Financing Arrangements	Note 12. Financing Arrangements ​ On January 30, 2015, we sold our corporate headquarters facility in Beverly, Massachusetts for $48.9 million. As part of the sale, we also entered into a 22-year lease agreement of our headquarters facility. This sale-leaseback is accounted for as a financing lease under generally accepted accounting principles and, as such, we have recorded a financing obligation of $48.0 million as of March 31, 2021. The associated lease payments include both an interest component and payment of principal, with the remaining liability being extinguished at the end of the original lease term. We posted a security deposit of $5.9 million in the form of an irrevocable letter of credit at the time of the closing. This letter of credit reduces our availability under our credit facility, as described in the next paragraph. ​ On July 31, 2020, we entered into a Senior Secured Credit Facilities Credit Agreement (the “Credit Agreement”) with Silicon Valley Bank, in its capacity as administrative agent and collateral agent for itself and as a lender, and such other banks and financial institutions or entities that from time to time join as lenders under the Credit Agreement. The Credit Agreement provides for a revolving credit facility in an aggregate principal amount not to exceed $40.0 million. Our obligations under the Credit Agreement are secured by a security interest, senior to any current and future debts and to any security interest, in all of our rights, title, and interest in, to and under substantially all of our assets, subject to limited exceptions, including permitted liens. The revolving credit facility terminates on July 31, 2023. As of March 31, 2021, we were in compliance with all covenant requirements of the Credit Agreement. As of such date, no borrowings had been made under the Credit Agreement, although a letter of credit for $5.9 million, previously issued by Silicon Valley Bank, had been rolled under the Credit Agreement, reducing the funds available for borrowing under the credit line. We entered into a First Amendment to the Credit Agreement with Silicon Valley Bank in March 2021 to (i) align the covenants with our 2021 stock repurchase program, and (ii) establish terms to transition from a Eurodollar based interest rate option to an interest rate benchmark using a secured overnight financing rate (known as “SOFR”) published by the Federal Reserve Bank of New York.

Income Taxes

Income Taxes	3 Months Ended
	Mar. 31, 2021
Income Taxes
Income Taxes	Note 13. Income Taxes ​ Income tax expense was $1.7 million for the three months ended March 31, 2021, compared to $1.0 million for the three months ended March 31, 2020. The $0.7 million increase was primarily due to a $6.0 million increase in pretax income partially offset by a tax benefit of $0.2 million due to the expiration of a statute of limitations on an uncertain tax position. The effective tax rate for the three months ended March 31, 2021 and 2020, respectively, was less than the U.S. statutory rate of 21% due to favorable discrete items related to equity compensation in those periods and Federal research and development tax credits that reduce the annual tax rate. ​ We had $54.9 million and $57.9 million of net deferred tax assets worldwide relating to net operating loss carryforwards, tax credit carryforwards and other temporary differences, as of March 31, 2021 and December 31, 2020, respectively. These deferred tax assets are available to reduce income taxes in future years. We have a $9.1 million valuation allowance in the U.S. against certain tax credits and state net operating losses due to the uncertainty of their realization based on long-term Company forecasts and the expiration dates on these tax assets. If future operating results of the Company within the U.S. or these foreign jurisdictions are significantly less than our expectations, it is reasonably possible that we would be required to record an additional valuation allowance on our deferred tax assets in the future. ​

Concentration of Risk

Concentration of Risk	3 Months Ended
	Mar. 31, 2021
Concentration of Risk
Concentration of Risk	Note 14. Concentration of Risk ​ For the three months ended March 31, 2021, one customer accounted for 29.6% of total revenue. For the three months ended March 31, 2020, four customers accounted for 20.9%, 16.9%, 14.6% and 10.7% of total revenue, respectively. ​ At March 31, 2021, one customer accounted for 19.8% of accounts receivable. At December 31, 2020, two customers accounted for 23.8% and 11.9% of accounts receivable, respectively.

Share Repurchase

Share Repurchase	3 Months Ended
	Mar. 31, 2021
Share Repurchase
Share Repurchase	Note 15. Share Repurchase ​ In December 2020, our Board of Directors approved stock repurchases of up to $100 million of our common stock through the end of 2021. During the three months ended March 31, 2021, we purchased 0.3 million shares at an average cost of $38.41 per share. The timing and actual number of shares repurchased under this program will depend on various factors including price, corporate and regulatory requirements, alternative investment opportunities and other market conditions. ​ Shares repurchased by us are accounted for when the transaction is settled. There were 22,160 unsettled share repurchases totaling approximately $0.9 million at March 31, 2021. Shares repurchased and retired are deducted from common stock for par value and from additional paid-in capital for the excess over par value. If additional paid-in capital has been exhausted, the excess over par value is deducted from retained earnings. Direct costs incurred to acquire the shares are included in the total cost of the shares.

Contingencies

Contingencies	3 Months Ended
	Mar. 31, 2021
Contingencies
Contingencies	Note 16. Contingencies ​ (a) Litigation ​ We are from time to time a party to litigation that arises in the normal course of our business operations. We are not presently a party to any litigation that we believe might have a material adverse effect on our business operations. ​ (b) Indemnifications ​ Our system sales agreements typically include provisions under which we agree to take certain actions, provide certain remedies and defend our customers against third-party claims of intellectual property infringement under specified conditions and indemnify customers against any damage and costs awarded in connection with such claims. We have not incurred any material costs as a result of such indemnifications and have not accrued any liabilities related to such obligations in the accompanying consolidated financial statements.

Recent Accounting Guidance

Recent Accounting Guidance	3 Months Ended
	Mar. 31, 2021
Recent Accounting Guidance
Recent Accounting Guidance	Note 17. Recent Accounting Guidance ​ i. Accounting Standards Update 2019-12 Income Taxes (Topic 740) ​ We adopted Financial Accounting Standards Board ASU No. 2019-12 “ Income Taxes (Topic 740) ​

Leases (Tables)

Leases (Tables)	3 Months Ended
	Mar. 31, 2021
Leases
Schedule of operating and finance lease right-of-use assets and related lease obligations	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ March 31, ​ December 31, ​ ​ ​ Leases Classification ​ 2021 2020 ​ Assets ​ ​ (in thousands) ​ ​ Operating leases Operating lease assets ​ $ 4,213 ​ $ 4,542 ​ ​ ​ Finance lease Finance lease assets * ​ 20,216 ​ 20,544 ​ ​ ​ Total leased assets ​ ​ $ 24,429 ​ $ 25,086 ​ ​ ​ Liabilities ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Current ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Operating Other current liabilities ​ $ 2,387 ​ $ 2,573 ​ ​ ​ Finance Current portion of finance lease obligation ​ ​ 809 ​ ​ 756 ​ ​ ​ Noncurrent ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Operating Other long-term liabilities ​ ​ 1,812 ​ ​ 1,949 ​ ​ ​ Finance Finance lease obligation ​ 47,167 ​ 47,393 ​ ​ ​ Total lease liabilities ​ ​ $ 52,175 ​ $ 52,671 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ * Finance lease assets are recorded net of accumulated depreciation of $48.7 million and include $0.7 million of prepaid financing costs as of March 31, 2021. Finance lease assets are recorded net of accumulated depreciation of $48.4 million and include $0.7 ​ ​ ​ ​
Schedule of lease costs	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three months ended ​ ​ ​ ​ ​ March 31, ​ ​ ​ Lease cost Classification ​ 2021 2020 ​ Operating lease cost ​ ​ (in thousands) ​ Service Cost of revenue ​ $ 639 ​ $ 550 ​ ​ ​ Research and development Operating expenses ​ 130 ​ 81 ​ ​ ​ Sales and marketing* Operating expenses ​ 378 ​ 332 ​ ​ ​ General and administrative* Operating expenses ​ 260 ​ 215 ​ ​ ​ Total operating lease cost ​ ​ $ 1,407 ​ $ 1,178 ​ ​ ​ Finance lease cost ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Depreciation of leased assets Cost of revenue, R&D, Sales and marketing and G&A ​ $ 328 ​ $ 353 ​ ​ ​ Interest on lease liabilities Interest expense ​ 1,279 ​ 1,303 ​ ​ ​ Total finance lease cost ​ ​ $ 1,607 ​ $ 1,656 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total lease cost ​ ​ $ 3,014 ​ $ 2,834 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ * Sales and marketing and general and administrative expense also includes short-term lease and variable lease costs of approximately $0.4 million and $0.2 million for the three months ended March 31, 2021 and 2020, respectively. ​ ​
Schedule of future minimum operating and finance leases	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Finance ​ Operating Total Maturity of Lease Liabilities ​ Leases ​ Leases ​ Leases ​ ​ ​ (in thousands) ​ 2021 ​ $ 4,394 ​ $ 2,129 ​ $ 6,523 ​ 2022 ​ 5,980 ​ 1,673 ​ 7,653 ​ 2023 ​ 6,114 ​ 534 ​ 6,648 ​ 2024 ​ 6,252 ​ 126 ​ 6,378 ​ 2025 ​ ​ 5,930 ​ ​ 74 ​ ​ 6,004 ​ Thereafter ​ ​ 73,723 ​ ​ 145 ​ ​ 73,868 ​ Total lease payments ​ $ 102,393 ​ $ 4,681 ​ $ 107,074 ​ Less interest portion* ​ ​ (54,417) ​ ​ (482) ​ ​ (54,899) ​ Finance lease and operating lease obligations ​ $ 47,976 ​ $ 4,199 ​ $ 52,175 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ * Finance lease interest calculated using the implied interest rate; operating lease interest calculated using estimated corporate borrowing rate. ​
Schedule of weighted-average remaining lease term and discount rates	​ ​ ​ ​ ​ ​ ​ ​ March 31, ​ Lease term and discount rate 2021 ​ Weighted-average remaining lease term (years): ​ ​ ​ ​ Operating leases ​ ​ 2.3 ​ Finance leases ​ 15.8 ​ Weighted-average discount rate: ​ ​ ​ ​ Operating leases ​ 4.5% ​ Finance leases ​ 10.5% ​ ​ ​ ​ ​ ​
Schedule of cash outflows by lease type	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three months ended ​ ​ ​ March 31, ​ Cash paid for amounts included in the measurement of lease liabilities 2021 ​ 2020 ​ ​ ​ (in thousands) ​ Operating cash outflows from operating leases ​ $ 1,407 ​ $ 1,178 ​ Operating cash outflows from finance leases ​ 1,279 ​ 1,422 ​ Financing cash outflows from finance leases ​ ​ 175 ​ ​ — ​ Operating lease assets obtained in exchange for operating lease liabilities ​ 791 ​ 765 ​ Finance lease assets obtained in exchange for new finance lease liabilities ​ $ — ​ $ — ​ ​ ​ ​ ​ ​ ​ ​ ​

Revenue (Tables)

Revenue (Tables)	3 Months Ended
	Mar. 31, 2021
Revenue.
Schedule of revenue by discipline	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three months ended ​ ​ March 31, ​ ​ 2021 ​ 2020 ​ ​ (in thousands) Systems ​ $ 80,991 ​ $ 82,338 Aftermarket ​ ​ 51,785 ​ ​ 36,653 Total Revenue ​ $ 132,776 ​ $ 118,991
Schedule of revenue by geographic markets	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three months ended ​ ​ March 31, ​ ​ 2021 ​ 2020 ​ ​ ​ (in thousands) North America ​ $ 9,508 ​ $ 10,661 ​ Asia Pacific ​ ​ 103,391 ​ ​ 96,828 ​ Europe ​ ​ 19,877 ​ ​ 11,502 ​ Total Revenue ​ $ 132,776 ​ $ 118,991 ​
Schedule of Contract liabilities	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ March 31, ​ December 31, ​ ​ 2021 ​ 2020 ​ ​ (in thousands) Contract liabilities ​ $ 22,142 ​ $ 23,058 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three months ended ​ March 31, ​ ​ 2021 ​ 2020 ​ ​ (in thousands) Balance, beginning of the period ​ $ 23,058 ​ $ 29,251 Deferral of revenue ​ ​ 11,264 ​ ​ 9,799 Recognition of deferred revenue ​ ​ (12,180) ​ ​ (4,944) Balance, end of the period ​ $ 22,142 ​ $ 34,106

Receivable and Allowance for _2

Receivable and Allowance for Credit Losses (Tables)	3 Months Ended
	Mar. 31, 2021
Receivable and Allowance for Credit Losses
Schedule of allowances for credit losses related to trade receivables	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three months ended ​ ​ ​ March 31, ​ ​ ​ 2021 ​ 2020 ​ ​ ​ (in thousands) ​ Balance, beginning of period ​ $ — ​ $ 818 ​ Provision for credit losses ​ ​ — ​ ​ — ​ Charge-offs ​ ​ — ​ ​ (818) ​ Recoveries ​ ​ — ​ ​ — ​ Balance, end of period ​ $ — ​ $ — ​

Computation of Net Earnings p_2

Computation of Net Earnings per Share (Tables)	3 Months Ended
	Mar. 31, 2021
Computation of Net Earnings per Share
Schedule of components of net income per share	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three months ended ​ ​ ​ March 31, ​ ​ 2021 2020 ​ ​ ​ ​ ​ ​ ​ ​ Net income available to common stockholders ​ $ 16,480 ​ $ 11,221 ​ Weighted average common shares outstanding used in computing basic income per share ​ 33,715 ​ 32,872 ​ Incremental options and RSUs ​ 928 ​ 1,185 ​ Weighted average common shares used in computing diluted net income per share ​ 34,643 ​ 34,057 ​ Net income per share ​ ​ ​ ​ ​ ​ ​ Basic ​ $ 0.49 ​ $ 0.34 ​ Diluted ​ $ 0.48 ​ $ 0.33 ​

Accumulated Other Comprehensi_2

Accumulated Other Comprehensive Income (Tables)	3 Months Ended
	Mar. 31, 2021
Accumulated Other Comprehensive Income
Schedule of changes in accumulated other comprehensive loss, net of tax	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Foreign Defined benefit ​ ​ ​ ​ currency ​ pension plan ​ Total ​ ​ (in thousands) Balance at December 31, 2020 ​ $ 3,945 ​ $ (510) ​ $ 3,435 ​ Other comprehensive loss and pension reclassification ​ (1,372) ​ 20 ​ (1,352) ​ Balance at March 31, 2021 ​ $ 2,573 ​ $ (490) ​ $ 2,083 ​

Cash, cash equivalents and re_2

Cash, cash equivalents and restricted cash (Tables)	3 Months Ended
	Mar. 31, 2021
Cash, cash equivalents and restricted cash
Schedule of reconciliation of cash, cash equivalents and restricted cash	​ ​ ​ ​ ​ ​ ​ ​ ​ March 31, ​ December 31, ​ ​ 2021 ​ ​ 2020 ​ ​ (in thousands) ​ Cash and cash equivalents $ 206,766 ​ $ 203,479 ​ Long-term restricted cash ​ 753 ​ ​ 753 ​ Total cash, cash equivalents and restricted cash $ 207,519 ​ $ 204,232 ​

Inventories, net (Tables)

Inventories, net (Tables)	3 Months Ended
	Mar. 31, 2021
Inventories, net
Schedule of components of inventories	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ March 31, ​ December 31, ​ ​ 2021 2020 ​ ​ (in thousands) ​ Raw materials ​ $ 100,634 ​ $ 100,254 ​ Work in process ​ 34,283 ​ 33,867 ​ Finished goods (completed systems) ​ 39,464 ​ 26,955 ​ Inventories, net ​ $ 174,381 ​ $ 161,076 ​

Product Warranty (Tables)

Product Warranty (Tables)	3 Months Ended
	Mar. 31, 2021
Product Warranty
Schedule of product warranty liability	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three months ended ​ ​ ​ March 31, ​ ​ 2021 2020 ​ ​ (in thousands) ​ Balance at January 1 (beginning of year) ​ $ 4,612 ​ $ 3,244 ​ Warranties issued during the period ​ 1,288 ​ 1,385 ​ Settlements made during the period ​ (968) ​ (950) ​ Changes in estimate of liability for pre-existing warranties during the period ​ (192) ​ 126 ​ Balance at March 31 (end of period) ​ $ 4,740 ​ $ 3,805 ​ ​ ​ ​ ​ ​ ​ ​ ​ Amount classified as current ​ $ 4,181 ​ $ 3,431 ​ Amount classified as long-term ​ 559 ​ 374 ​ Total warranty liability ​ $ 4,740 ​ $ 3,805 ​

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	3 Months Ended
	Mar. 31, 2021
Fair Value Measurements
Schedule of Company's assets and liabilities by level within the fair value hierarchy	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ March 31, 2021 ​ ​ Fair Value Measurements ​ Level 1 Level 2 Level 3 Total ​ ​ (in thousands) Assets ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Cash equivalents: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Money market funds, U.S. Government Securities and Agency Investments ​ $ 174,752 ​ $ — ​ $ — ​ $ 174,752 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, 2020 ​ ​ Fair Value Measurements ​ Level 1 Level 2 Level 3 Total ​ ​ (in thousands) Assets ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Cash equivalents: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Money market funds, U.S. Government Securities and Agency Investments ​ $ 172,119 ​ $ — ​ $ — ​ $ 172,119 ​ ​

Stock-Based Compensation (Detai

Stock-Based Compensation (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Stock-Based Compensation
Stock-based compensation expense	$ 2,400	$ 1,700
Proceeds from exercise of stock options	$ 2,512	$ 4,499
Common Stock
Stock-Based Compensation
Exercise of stock options (in shares)	268,000	540,000
Common Stock | 2020 Employee stock purchase plan
Stock-Based Compensation
Exercise of stock options (in shares)	300,000	600,000
Proceeds from exercise of stock options	$ 2,500	$ 4,500
2000 Stock Plan
Stock-Based Compensation
Awards granted (in shares)	0
2000 Stock Plan | Stock Options
Stock-Based Compensation
Options Expiration period	10 years

Leases (Details)

Leases (Details)	3 Months Ended
	Mar. 31, 2021
Lessee, Lease, Description [Line Items]
Option to extend	true
Minimum
Lessee, Lease, Description [Line Items]
Renewal term	1 year
Maximum
Lessee, Lease, Description [Line Items]
Renewal term	3 years

Leases - Operating and Finance

Leases - Operating and Finance Lease Right-of-use-assets and Related Lease Obligations (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Leases
Operating lease assets	$ 4,213	$ 4,542
Operating Lease, Right-of-Use Asset, Statement of Financial Position [Extensible List]	Operating lease assets
Finance lease assets	$ 20,216	20,544
Finance Lease, Right-of-Use Asset, Statement of Financial Position [Extensible List]	Finance lease assets
Total leased assets	$ 24,429	25,086
Operating liabilities current	$ 2,387	$ 2,573
Operating Lease, Liability, Current, Statement of Financial Position [Extensible List]	Other Liabilities, Current	Other Liabilities, Current
Finance liabilities current	$ 809	$ 756
Finance Lease, Liability, Current, Statement of Financial Position [Extensible List]	Other Liabilities, Current
Operating liabilities noncurrent	$ 1,812	$ 1,949
Operating Lease, Liability, Noncurrent, Statement of Financial Position [Extensible List]	Other Liabilities, Noncurrent	Other Liabilities, Noncurrent
Finance liabilities noncurrent	$ 47,167	$ 47,393
Finance Lease, Liability, Noncurrent, Statement of Financial Position [Extensible List]	Finance liabilities noncurrent
Total lease liabilities	$ 52,175	52,671
Operating Lease, Liability, Statement of Financial Position [Extensible List]	us-gaap:OtherLiabilitiesCurrent us-gaap:OtherLiabilitiesNoncurrent
Finance lease, accumulated depreciation	$ 48,700	48,400
Prepaid financing costs	$ 700	$ 700

Leases - Lease Cost (Details)

Leases - Lease Cost (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Lease cost
Total operating lease cost	$ 1,407	$ 1,178
Depreciation of leased assets	328	353
Interest on lease liabilities	1,279	1,303
Total finance lease cost	1,607	1,656
Total lease cost	3,014	2,834
Short-term lease and variable lease costs	400	200
Service
Lease cost
Total operating lease cost	639	550
Research and development
Lease cost
Total operating lease cost	130	81
Sales and marketing*
Lease cost
Total operating lease cost	378	332
General and administrative*
Lease cost
Total operating lease cost	$ 260	$ 215

Leases - Future Minimum Cash Ou

Leases - Future Minimum Cash Outflow and Weighted-average Remaining Lease Term and Discount Rate (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Future minimum lease payments finance lease
2021	$ 4,394
2022	5,980
2023	6,114
2024	6,252
2025	5,930
Thereafter	73,723
Total lease payments	102,393
Less interest portion	(54,417)
Finance lease obligations	47,976
Future minimum lease payments operating lease
2021	2,129
2022	1,673
2023	534
2024	126
2025	74
Thereafter	145
Total lease payments	4,681
Less interest portion	(482)
Operating lease obligations	4,199
Future minimum lease payments finance and operating lease
2021	6,523
2022	7,653
2023	6,648
2024	6,378
2025	6,004
Thereafter	73,868
Total lease payments	107,074
Less interest portion	(54,899)
Total lease liabilities	$ 52,175	$ 52,671
Lease term and discount rate
Operating leases -Weighted-average remaining lease term (in years)	2 years 3 months 18 days
Finance leases - Weighted-average remaining lease term (in years)	15 years 9 months 18 days
Operating leases - Weighted-average discount rate	4.50%
Finance leases - Weighted-average discount rate	10.50%
Finance lease term	22 years
Minimum
Lease term and discount rate
Operating lease term	1 year
Maximum
Lease term and discount rate
Operating lease term	10 years

Leases - Cash Flow by Lease Typ

Leases - Cash Flow by Lease Type (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Leases
Operating cash outflows from operating leases	$ 1,407	$ 1,178
Operating cash outflows from finance leases	1,279	1,422
Financing cash outflows from finance leases	175
Operating lease assets obtained in exchange for operating lease liabilities	$ 791	$ 765

Revenue (Details)

Revenue (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Dec. 31, 2020	Mar. 31, 2020	Dec. 31, 2019
Disaggregation of Revenue
Contract liabilities	$ 22,142	$ 23,058	$ 34,106	$ 29,251
Deferred revenue	20,417	21,221
Long-term deferred revenue	$ 1,725	$ 1,837
Systems
Disaggregation of Revenue
Payment upon shipment of tool, as a percent	90.00%
Payment upon installation, as a percent	10.00%
Systems | Minimum
Disaggregation of Revenue
Payment upon delivery of parts, period	30 days
Systems | Maximum
Disaggregation of Revenue
Payment upon delivery of parts, period	60 days

Revenue - Revenue by discipline

Revenue - Revenue by discipline & geographical areas (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Disaggregation of Revenue
Total Revenue	$ 132,776	$ 118,991
North America
Disaggregation of Revenue
Total Revenue	9,508	10,661
Asia Pacific
Disaggregation of Revenue
Total Revenue	103,391	96,828
Europe
Disaggregation of Revenue
Total Revenue	19,877	11,502
Systems
Disaggregation of Revenue
Total Revenue	80,991	82,338
CS&I/Aftermarket
Disaggregation of Revenue
Total Revenue	$ 51,785	$ 36,653

Revenue - Contract liabilities

Revenue - Contract liabilities (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020	Mar. 31, 2020	Dec. 31, 2019
Revenue.
Contract liabilities	$ 22,142	$ 23,058	$ 34,106	$ 29,251

Revenue - Deferred revenue (Det

Revenue - Deferred revenue (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Revenue.
Balance, beginning of the period	$ 23,058	$ 29,251
Deferral of revenue	11,264	9,799
Recognition of deferred revenue	(12,180)	(4,944)
Balance, end of the period	$ 22,142	$ 34,106

Receivable and Allowance for _3

Receivable and Allowance for Credit Losses - Allowances for Credit Losses Related to Trade Receivables (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2020USD ($)
Receivable and Allowance for Credit Losses
Balance, beginning of period	$ 818
Charge-offs	$ (818)

Computation of Net Earnings p_3

Computation of Net Earnings per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Computation of Net Earnings per Share
Net income available to common stockholders	$ 16,480	$ 11,221
Weighted average common shares outstanding used in computing basic income per share	33,715	32,872
Incremental options and RSUs	928	1,185
Weighted average common shares used in computing diluted net income per share	34,643	34,057
Net income per share
Basic	$ 0.49	$ 0.34
Diluted	$ 0.48	$ 0.33
Anti-dilutive common equivalent shares excluded from calculation	1,429	1,675

Accumulated Other Comprehensi_3

Accumulated Other Comprehensive Income (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Changes in accumulated other comprehensive income, net of tax
Balance at December 31, 2020	$ 3,435
Other comprehensive income and pension reclassification	(1,352)	$ (1,055)
Balance at March 31, 2021	2,083
Foreign currency
Changes in accumulated other comprehensive income, net of tax
Balance at December 31, 2020	3,945
Other comprehensive income and pension reclassification	(1,372)
Balance at March 31, 2021	2,573
Defined benefit pension plan
Changes in accumulated other comprehensive income, net of tax
Balance at December 31, 2020	(510)
Other comprehensive income and pension reclassification	20
Balance at March 31, 2021	$ (490)

Cash, cash equivalents and re_3

Cash, cash equivalents and restricted cash (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020	Mar. 31, 2020	Dec. 31, 2019
Cash and cash equivalents	$ 206,766	$ 203,479
Long-term restricted cash	753	753
Total cash, cash equivalents and restricted cash	207,519	$ 204,232	$ 181,416	$ 146,534
Letter of credit related to workers' compensation insurance	700
Deposit related to customs activity	100
Revolving credit facility
Restricted cash which relates to support of outstanding letters of credit	$ 800

Inventories, net (Details)

Inventories, net (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Inventories, net
Raw materials	$ 100,634	$ 100,254
Work in process	34,283	33,867
Finished goods (completed systems)	39,464	26,955
Inventories, net	$ 174,381	$ 161,076

Product Warranty (Details)

Product Warranty (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Mar. 31, 2021	Dec. 31, 2020	Mar. 31, 2020
Product Warranty
Product warranty period	1 year
Changes in standard product warranty liability
Balance at January 1 (beginning of year)	$ 4,612	$ 3,244
Warranties issued during the period	1,288	1,385
Settlements made during the period	(968)	(950)
Changes in estimate of liability for pre-existing warranties during the period	(192)	126
Balance at March 31 (end of period)	4,740	3,805
Product warranty classification
Amount classified as current			$ 4,181	$ 4,280	$ 3,431
Amount classified as long-term			559		374
Total warranty liability	$ 4,740	$ 3,805	$ 4,740	$ 4,612	$ 3,805

Fair Value Measurements (Detail

Fair Value Measurements (Details) - Recurring - Money market funds, US Government Securities and Agency Investments - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Total
Fair Value Measurements
Money market funds, U.S. Government Securities and Agency Investments	$ 174,752	$ 172,119
Level 1
Fair Value Measurements
Money market funds, U.S. Government Securities and Agency Investments	$ 174,752	$ 172,119

Financing Arrangements (Details

Financing Arrangements (Details) - USD ($) $ in Thousands	Jan. 30, 2015	Mar. 31, 2021	Dec. 31, 2020	Jul. 31, 2020
Financing Arrangements
Long-term finance lease obligation		$ 47,167	$ 47,393
Sale leaseback obligation
Financing Arrangements
Long-term finance lease obligation		48,000
Security deposit		5,900
Beverly Property Owner LLC | Buildings
Financing Arrangements
Sale price	$ 48,900
Lease term	22 years
Silicon Valley Bank | Revolving credit facility
Financing Arrangements
Maximum borrowing capacity under the credit facility				$ 40,000
Borrowings amount		0
Silicon Valley Bank | Revolving credit facility | Letter of credit
Financing Arrangements
Letter of credit		$ 5,900

Income Taxes (Details)

Income Taxes (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Dec. 31, 2020
Valuation allowance
Income tax provision	$ 1,721	$ 1,041
Increase in income tax	700
Increase in income tax due to decrease in pretax income	6,000
Deferred tax assets, net	54,936		$ 57,851
Deferred tax assets valuation allowance	9,100
Decrease in income tax due to tax benefit recognized upon expiration of statute of limitation regarding uncertain tax position previously recorded	$ 200
Maximum
Valuation allowance
Statutory Income Tax Rate (as a Percent)	21.00%

Concentration of Risk (Details)

Concentration of Risk (Details) - customer	3 Months Ended		12 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Dec. 31, 2020
Revenue | Customer concentration risk
Concentration of Risk
Number of customers	1	4
Revenue | Customer concentration risk | First customer
Concentration of Risk
Percentage of concentration risk	29.60%	20.90%
Revenue | Customer concentration risk | Second customer
Concentration of Risk
Percentage of concentration risk		16.90%
Revenue | Customer concentration risk | Third customer
Concentration of Risk
Percentage of concentration risk		14.60%
Revenue | Customer concentration risk | Fourth customer
Concentration of Risk
Percentage of concentration risk		10.70%
Consolidated accounts receivable | Credit concentration risk
Concentration of Risk
Number of customers	1		2
Consolidated accounts receivable | Credit concentration risk | First customer
Concentration of Risk
Percentage of concentration risk	19.80%		23.80%
Consolidated accounts receivable | Credit concentration risk | Second customer
Concentration of Risk
Percentage of concentration risk			11.90%

Share Repurchase (Details)

Share Repurchase (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended
	Mar. 31, 2021	Dec. 31, 2020
Share Repurchase
Share repurchase program common stock authorized amount		$ 100
Number of shares repurchased	300,000
Average cost	$ 38.41
Unsettled share repurchases	22,160
Stock repurchase program, remaining authorized repurchase amount	$ 0.9