Detection and Quantification of Carboxylic Acid Excursions in High-Purity Water Using an On-Line TOC Analyzer
By Terry Stange, Ph.D., Zhao Lu, and Emek Blair, Ph.D.
In a recent paper by Hanson (1), the author described carboxylic acid breakthrough in several high-purity water polish loops at Texas Instrument (TI) fabs in Dallas, Texas. Mr. Hanson was able to trace the source of these organic acids back to the plants feedwater and attributed acid formation to implementation of a new municipal water ozonation system. The carboxylic acids were apparently ozonation by-products that were not destroyed before leaving the water treatment facility. The level of incoming carboxylic acids that lead to the high-purity water breakthrough was not explicitly given, but data indicates concentrations of 200 to 400 parts per billion (ppb) were necessary (1). The levels of carboxylic acid that reached the wafer fab were also not given, but due to the efficiency of the high-purity water plant for removing ionic contamination, we assume levels were ranging between 5 to 20 parts per billion (ppb).
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