TRACE ANALYSIS OF CONTAMINATION IN LSI FABRICATION PROCESS ENVIRONMENT

Silicon wafer is subjected to various contamination from clean room environment in LSI fabrication process. This paper presents an analytical methods and results of trace chemical contamination derived from clean room air and gases. These contamination has been investigated by a combination of an impinger and trace analyzers such as graphite furnace atomic absorption spectroscopy, inductively coupled plasma mass spectrometry, and ion chromatography. Detection limits of both cations and anions are mostly a few ng/m(3) or less. Cation impurity concentrations of Na+,Ca2+, and Zn2+ and anion concentrations of Cl-, and SO42- show normal correlation, although it is not necessarily strong. The concentrations of Cl-, NO2-, NO3- and SO42- anions tend to increase after passing purifiers both in nitrogen gas and oxygen gas.