Arch Chemicals and Semitool to Market MicrOzone.

NORWALK, Conn.--(BUSINESS WIRE)--July 13, 1999--

Arch Chemicals, a leading supplier of microelectronic chemicals, and Semitool, Inc., the semiconductor industry leader in spray cleaning technology, announce their agreement to collaborate in the commercialization of MicrOzone(TM). MicrOzone(TM) is a process application that creates an environmentally superior solution for the removal of post-etch residues and residual photoresist by combining two environmentally safe processes. This unique combination integrates Arch's patented Microstrip(R) 5002, aqueous-based cleaner, with a modified version of Semitool's patent pending HydrOzone(TM) ozonated water process. The process is delivered in an automated Semitool Spectrum(TM) or Class 1 semi-automated spray tool.

"The collaboration between Arch Chemicals and Semitool stems from the industry's need to move towards more cost-effective and environmentally friendly processes," stated Dana Scranton, Semitool Surface Preparation Division Director of Marketing. "The flexible nature of the HydrOzone(TM) process permits the removal of resist and organic residue without damage to surface films. It is an excellent complement to Arch's Microstrip(R) 5002 chemistry," he added.

"MicrOzone(TM) effectively removes post-etch residues and residual resist without generating any solvent waste, thereby lowering the cost of ownership," stated Dr. Brian E. O'Donnelly, business manager, photopolymer ancillaries for Arch Chemicals.

"The collaboration has created a system that eliminates the handling and disposal of chemical solvents and reduces the number of steps in the cleaning process, thereby increasing throughput and ultimately saving the customer both time and money."

Semitool, Inc., based in Kalispell, MT, designs, manufactures, markets, and services equipment used in the fabrication of semiconductors. The company's products include batch and single wafer spray surface preparation and cleaning equipment, electrochemical deposition tools for copper interconnects, and other metal deposition applications, thermal processing equipment, and supervisory control systems for semiconductor manufacturing equipment. The company's stock is traded on the Nasdaq National Market under the symbol SMTL.

Arch Chemicals manufactures and supplies leading-edge photoresists, ancillary materials and polyimides to the semiconductor industry. Arch Chemicals, headquartered in Norwalk, CT, has built market leadership in three business segments that serve global markets: Microelectronic Chemicals, Water Chemicals and Performance Chemicals. The company employs over 3,000 individuals and has manufacturing capabilities in North America, South America, Europe, Asia and Africa. Arch's 1998 sales were approximately $900 million.

Safe Harbor Statement

Except for historical information, the matters discussed in this news release are forward-looking statements, including in particular those statements relating to the commercialization of MicrOzone(TM). Such forward-looking statements are subject to certain risks and uncertainties including, but not limited to, industry conditions, economic conditions, and non-acceptance of new technologies, as well as other risks indicated from time to time in the Company's filings with the Securities and Exchange Commission. The company assumes no obligation to update or supplement forward-looking statements that become untrue because of subsequent events.