Monitoring and Characterization of Bacterial Contamination in a High-Purity Water System Used for Semiconductor Manufacturing
2000
Kim In-Seop | Lee Kye-Joon Seoul National University, Seoul (Korea Republic)
Hydrogen peroxide has been used in cleaning the piping of an advanced high-purity water system that supplies ultra-high purity water(UHPW) for 16 megabyte DRAM semiconductor manufacturing. The level of hydrogen peroxide-resistant bacteria in UHPW water was monitored prior to and after disinfecting the piping with hydrogen peroxide. Most of the bacteria isolated after hydrogen peroxide disinfection were highly resistant to hydrogen peroxide. However, the percentage of resistant bacteria decreased with time. The hydrogen peroxide-resistant bacteria were identified as Micrococcus luteus, Bacillus cereus, Alcaligenes latus, Xanthomonas sp. and Flavobacterium indologenes. The susceptibility of the bacteria to hydrogen peroxide was tested as either planktonic cells or attached cells on glass. Attached bacteria as the biofilm on glass exhibited increased hydrogen peroxide resistance, with the resistance increasing with respect to the age of the biofilm. These results indicate that bacteria resistant to hydrogen peroxide play an important role in biofilm regrowth on piping after hydrogen peroxide treatment. In order to optimize the cleaning strategy for poping of the high-purity water system, the disinfecting effect of hydrogen peroxide and peracetic acid on the bacteria was evaluated. The combined use of hydrogen peroxied and peracetic acid was very effective in killing attached becteria as well as planktonic bacteria.
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