COMPARISON OF LOW-TEMPERATURE OXIDATION OF CRYSTALLINE SI AND B WITH A-SI-B ALLOY - AN X-RAY PHOTOELECTRON-SPECTROSCOPY STUDY

The low-temperature (25-600 degrees C) oxidation of amorphous silicon boron alloy (a-Si:B) prepared by low-pressure chemical-vapor depositio n, with varying boron contents (0%-25%), has been qualitatively studie d using x-ray photoelectron spectroscopy. The oxidation of these amorp hous a-Si:B films has been compared to that of crystalline silicon (c- Si) and boron (c-B). It was found that higher boron concentration in t he Si:B alloy caused faster oxidation of both the Si and B components in the amorphous alloy as compared to either c-Si or c-B. At room temp erature, suboxides were formed (Si+, Si2+, Si3+, B+, B2+) as opposed t o oxides (Si4+, B3+). At higher temperature the oxidation was faster, as expected. In addition, at higher temperatures the SiO2 and B2O3 oxi des were preferentially formed by the conversion of the suboxides. All the evidence suggests that the availability of three-coordinated B bo nds in the Si:B alloy accelerates the oxidation process when compared to the oxidation of the tightly bounded c-Si or c-B. (C) 1997 American Vacuum Society.