ADVANCED ULTRAPURE WATER BY HF ADDITION

To improve ultrapure water, the additional effect of HF in pure water was investigated. Both formation of native oxide on the Si wafer surfa ce and generation of viable cells in pure water can be prevented by us ing pure water containing HF on the order of parts per million instead of conventional pure water. Moreover, by using PFA or PTFE as a pipe material, pure water containing HF which was not contaminated by metal ions and viable cells can be fed to point of use without a circular l ine such as a conventional pure water feeding line.