Thermal Oxidation of Amorphous Silicon-Germanium-Boron Alloy

Amorphous Si–Ge–B prepared by low pressure CVD is thermally oxidized much faster than crystalline Si in a wet oxygen ambient. Oxidation rates more than ten times as large as those for crystalline Si are obtained. The oxidation rate increases with increasing B content in starting a-Si–Ge–B films, whereas it decreases with increasing Ge content. It is deduced from infrared absorption and Auger electron spectra that Si–Ge–B oxides are substantially composed of Si, B and O. In contrast to conventional CVD borosilicate glasses prepared at 300–400°C , Si–Ge–B oxides are very stable to high humidity. Electrical properties such as resistivity, maximum dielectric strength and dielectric loss are comparable to those of high quality SiO2. A model of oxidation is proposed and discussed.