シリコン基板の熱酸化に及ぼす臭素の影響

Abstract

Silicon substrates were oxidized in an O2/Br2 ambient. In the initial stage of the oxidation, the rate was slower than that of the conventional oxidation. In the course of the O2/Br2 oxidation, however, the rate was gradually accelerated.The oxidation reaction was analyzed on the basis of the mixed control model of the diffusion of oxygen in the SiO2 film and the chemical reaction at the SiO2/Si interface. The linear rate constant, kL was smaller and the parabolic rate constant, kP was larger in comparison with those of the conventional oxidation, respectively. But the activation energies were almost the same as the conventional ones.SIMS (Secondary ion mass spectroscopy) and FT-IR (Fourier transform infrared spectroscopy) were employed. The bromine in the SiO2 films existed near the oxide films as Si-Br bonds.The above results led to the following conclusion. In the initial stage, the Si-Br bonds formed at the SiO2/Si interface reduced the number of the SiO2 production sites, which retarded the oxidation rate. On the other hand, the Si-Br bonds in the SiO2 films increased the numbers of the solubility- and the diffusion-sites of oxygen in the SiO2 films, resulting in the acceleration of the oxidation rate, in the course of the process.