FREMONT, Calif.- April 30, 2002 - Mattson Technology (NASDAQ: MTSN), a leading supplier of advanced process equipment used to manufacture semiconductors, today announced that it has completed the closing of its previously announced private placement transaction in the amount of $45.6 million. As a result, the Company has issued approximately 7.4 million shares of its common stock at a price of $6.15 per share, and has received cash proceeds of $37.5 million and reduced its outstanding promissory notes to STEAG Electronic Systems AG, Mattson's largest shareholder, by $8.1 million.

The transaction included 5.1 million shares sold to the State of Wisconsin Investment Board and 1.3 million shares sold to STEAG Electronic Systems AG. The Company intends to use net proceeds from this private placement for general corporate purposes. Bear, Stearns & Co., Inc. served as sole placement agent for this transaction.

About Mattson Technology, Inc.

Mattson Technology, Inc. is a leading supplier of semiconductor wafer processing equipment used in "front-end" fabrication of integrated circuits. The company is a market leader in dry strip and RTP equipment, and its products combine advanced process technology on high-productivity platforms backed by industry-leading support. Since beginning operations in 1989, the company’s core vision has been to help bring technology leadership and productivity gains to semiconductor manufacturers worldwide. Headquartered in Fremont, Calif., the company maintains sales and support centers throughout the United States, Europe and Asia. For more information, please contact Mattson Technology, Inc., 47131 Bayside Parkway, Fremont, Calif. 94538. Telephone: (800) MATTSON/(510) 657-5900. Fax: (510) 492-5911. Internet: www.mattson.com.