Journal of the Electrochemical Society, Vol.143, No.1, 339-346, 1996
Low-Background Instrumental Neutron-Activation Analysis of Silicon Semiconductor-Materials
Samples of silicon wafers, some implanted with zinc, some with memory circuits fabricated on them, and some with oxide coatings were activated with neutrons and analyzed for trace element impurities with low background germanium gamma-ray spectrometers. Results are presented for these samples as well as for a reference material. Because the silicon matrix activation is so small, reduced spectrometer system background permits the detection of significantly lower impurity concentrations than would otherwise be possible. For our highest efficiency and lowest background system, limits on the lowest levels of trace element concentrations have been measured for wafer sized (1 to 10 g) samples and inferred for bulk sized (365 g) samples. For wafer-sized samples, parts-per-trillion detection capabilities are demonstrated for a variety of elemental contaminants important in semiconductor fabrication.