Wet oxidation of Si _1-x-yGe _xC _y layers on (100) Si

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 _xO ₂ was obtained at 700°C whereas SiO ₂ 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 SiO ₂ 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 approx. 5 nm nanocrystals.