Use of the ion microanalyzer for the characterization of bulk and epitaxial silicon and gallium arsenide

The ion microanalyzer permits a localized mass spectrometric analysis, i.e. the qualitative and quantitative analysis of the impurities contained in a small selected volume. This procedure makes possible the analysis of very thin epitaxial layers (for example silicon and gallium arsenide). As regards qualitative analysis, the apparatus is designed for the selection of ions. After the recording and analysis of the ion spectrum, a large number of the impurities present in the sample are determined qualitatively. Quantitative analysis can be performed with the equipment, but this requires the analysis of a homogeneous standard sample previously dosed by spark-source mass spectrometry. The quantitative analysis of bulk and epitaxial silicon and gallium arsenide is described and the limits of detection of the principal impurities are given. It is also shown how the possibility of localized analysis was exploited. A correlation was established between the existing impurities and the chemically revealed crystal imperfections. A comparative analysis of the distribution of the impurities in the epitaxial layers was also carried out. The periodic analysis of epitaxial layers makes it possible to follow the deterioration by contamination, if any, under the epitaxial conditions, and to improve the sample quality.