Effects of HCl and Cl2 additions on silicon oxidation kinetics
Abstract
The growth kinetics of SiO2 films (100-18000Å) on [100], 2Ωcm silicon have been investigated between 900-1100‡C with additions of 0-9 vol.% HC1 or 0-2 vol.% Cl2 to the dry oxygen ambient. The thickness-time data could best be fitted numerically to a mixed linear-parabolic equation that included a correction for fast initial growth. Equivalent amounts of chlorine (e.g., 2 vol.% HC1 or 1 vol.% Cl2) produced completely different effects on the rate of SiO2 growth. The quantitative effects of halogen additions were studied in greatest detail at 900‡C. At that temperature, the parabolic rate constant increased linearly with the HC1 concentration. At the same time, the linear rate constant remained constant. Both rate constants did change when Cl2 was used as an additive. The effect of HC1 additions on the parabolic rate constant reaches a maximum around 1000‡C. Possible mechanisms for the halogen effects are discussed,← and it is seen that the gas phase reaction 4 HC1 + 02 → 2 H2O + 2 Cl2 is not reflected in the growth kinetics. © 1974 American Institute of Mining, Metallurgical, and Petroleum Engineers, Inc.