1 EXHIBIT 23.1 INDEPENDENT AUDITORS' CONSENT We consent to the incorporation by reference in the Registration Statements Nos. 33-31298, 33-85020, 333-39499 and 333-80079 of Silicon Valley Group, Inc. on Forms S-8 of our report dated October 25, 1999 appearing in this Annual Report on Form 10-K of Silicon Valley Group, Inc. for the year ended September 30, 1999. /s/ DELOITTE & TOUCHE LLP - ------------------------------------ Deloitte & Touche LLP San Jose, California December 20, 1999