Preparation of Ultra-High Purity Higher Silanes and Germanes

Abstract

Disilane and trisilane were synthesized by silent electric discharge (SED) in high purity silane. Within two hours 60–70% monosilane was converted into a mixture of higher silanes. Pure disilane and trisilane were obtained by variable temperature distillation of mixed higher silanes. In contrast to other sources of disilane, no impurities greater than 0.1 ppm could be detected in the SED produced disilane by gas chromatographick analysis. High purity digermane was prepared in 42% yield by SED in pure germane. Routine gas chromatographic methods have been developed to identify trace impurities in the semiconductor process gases (such as silanes, phosphines, etc.) down to the part per million level.