Wet Oxidation of Si_1-x-yGe_xC_y Layers on (100) Si

Abstract

Single crystal Si_0.63Ge_0.36C_0.01 and amorphous Si_0.65Ge_0.27C_0.08 layers have been oxidized in a wet ambient at 700 °C and 900 °C. The oxide growth has been studied using Rutherford backscattering spectrometry and transmission electron microscopy. A reference sample of Si_0.63Ge_0.37 was also oxidized in order to determine the influence of C on the oxidation behavior. The lower C content alloy behaved similar to the SiGe alloy. Uniform Si_1-xGe_xO₂ was obtained at 700 °C whereas SiO₂ was formed at 900 °C, and Ge piled up underneath the oxide. In both cases, C was not detected in the oxide layer. The amorphous Si_0.65Ge_0.27C_0.08 alloy behaved significantly different at both oxidation temperatures in comparison with the crystalline Si_0.63Ge_0.36C_0.01 and Si_0.63Ge_0.37. Negligible oxidation occurred at 700 °C whereas SiO₂ was obtained at 900 °C and the rejected Ge distributed uniformly throughout the SiGeC alloy. It is proposed that fast Ge diffusion during oxidation at 900 °C resulted from diffusion at grain boundaries, since crystallization of the amorphous SiGeC layer occurred in conjunction with oxidation, leading to nucleation of ∼5 nm nanocrystals.