Comparison of low-temperature oxidation of crystalline Si and B with a-Si:B alloy: An x-ray photoelectron spectroscopy study

Abstract

The low-temperature (25–600 °C) oxidation of amorphous silicon boron alloy (a-Si:B) prepared by low-pressure chemical-vapor deposition, with varying boron contents (0%–25%), has been qualitatively studied using x-ray photoelectron spectroscopy. The oxidation of these amorphous 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 the 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 temperature, suboxides were formed (Si+, Si2+, Si3+, B+, B2+) as opposed to oxides (Si4+, B3+). At higher temperature the oxidation was faster, as expected. In addition, at higher temperatures the SiO2 and B2O3 oxides were preferentially formed by the conversion of the suboxides. All the evidence suggests that the availability of three-coordinated B bonds in the Si:B alloy accelerates the oxidation process when compared to the oxidation of the tightly bounded c-Si or c-B.

Comparison of shallow depth profiles of cobalt-implanted Si wafers determined by total reflection x-ray fluorescence analysis after repeated stratified etching and by rutherford backscattering spectrometry

“…An incomplete oxidation of Si in the O 2 plasma could be a reason for the shifted profile. As reported recently, 11 suboxides of Si can be formed at lower temperatures <100°C . In order to take such a potential effect into consideration, the formation of nonstoichiometric SiO 1.5 has been assumed instead of SiO 2 and included in the calculations.…”