High purity of silicon wafers is demanded by the high performance and highly integrated IC and LSI semiconductors. Impurities on, or in, the silicon wafer have a big influence on the characteristics of the semiconductor as a final product. Usually, these impurities are introduced by water during washing, by bad handling, or by reagents and processes.

Typical influences of these impurities are shown in Table 1. These elements are present at too small concentration to he detected by ordinary analytical methods (except for oxygen). Usually, XPS , AES, NAA, SIMS, ICPAES, ICP-MS and AAS are used for trace analysis.