Cleaner, Cheaper, HCl
The purification process feeds industrial-grade hydrochloric acid into a heated recirculating acid stream. Purified hydrochloric acid evaporates, leaving the metals and other contaminants in the recirculation stream. The vapor passes through a de-mister column to remove residual small droplets. The vapor then is condensed and collected as an ultra-high-purity hydrochloric acid with less than 100 parts per trillion of each contaminant metal. This level of purity meets current proposed SEMI standards, but Wayne Hammond, director of product management at Koch, told Semiconductor Online that most of the semiconductor industry now uses acid with contaminants in the one-to-ten parts/billion range.
According to Evan Jones, a development engineer at Pacific Northwest, all components of the system are made from high purity fluropolymer, thermally welded by a proprietary method. The smooth surfaces of these joints prevent residue accumulation. Though fluropolymer piping and thermally welded joints are standard in the semiconductor industry, Hammond said, most chemical processing systems use glass and ceramic tubing. The typical flange connections present a greater risk for both contamination and leaks.
The new ultra high purity hydrochloric acid (UHP HCl) system is capable of producing several million pounds of acid per year, enough to supply several fabs. Though the cost of the system itself is comparable to other UHP HCl systems, Hammond explained, it can use less expensive industrial grade feedstocks. Developers expect the system to pay for itself within six months.
By Katherine Derbyshire
For more information:
Pacific Northwest National Laboratory
P.O. Box 999
902 Battelle Boulevard
Richland, WA 99352
Voice: +1 (509) 375-2121
Fax: +1 (509) 372-4791