The life of a high-purity water treatment project may be compared to roli¡ng a boulder down a dome-shaped hill (1). The project gets rolling with a fairly small nudge. Once ¡t ¡s rolling, however, ¡t takes a great deal of effort (time and money) to change the direction or go back up the hill. The projectto design, build, instali, and commission the “E” high-purity water system at VLSI lechnology’s San Antonio, Texas, manufacturing site followed this model. Nowthat we are at the bottom of the hill with a functional system, we will take a look back to see the major decisions and players that made the new system successful.
Every custom water system carnes a “flavor” from the owner. VLSI Technology Inc. makes custom and semi-custom integrated circuits (lOs) primarily for the digital communications and graphics industries. VLSI currently has one wafer fabrication plant for production quantities of lCs. This plant in San Antonio has approximately 60,000 square feet of Class 1/Class 100 cleanroom space making a variety of products with minimum line sizes of 0.8 micron ([Jm) to 0.2 pm on 150-millimeter (mm) (6 inch) wafers. The plant is currently converting to 200-mm (8 inch) wafers. VLSI had 1998 revenue from continuing operations of $548 million and employs about 2,200 people worldwide of which 600 to 700 work in San Antonio.
The Start of the Project.
In the summer of 1997, VLSI initiated a project to expand the manufacturing cleanroom by roughly 15,000 square feet. This new space holds chemical mechanical polishing units ([CMP], a process required for line widths of 0.35 pm and smaller) and other fab equipment.
The “E” high-purity water system was builtto supply watertothefabto support the extra demand from the CMP process and the conversion to 200-mm wafers. VLSI-San Antonio had four existing water systems operating in parallel with a combined capacity of 600 gallons per minute (gpm). We identified the need for a high-purity water system supplying 300 gpm, butrecognizedthat previous estimating efforts had fallen short by 10% to 25% of eventual demand. We also saw that the water quality from the existing systems was adequate for current technologies, but was starting to cause problems for the manufacturing organization usually when the systems were not working in “normal” mode.