Comprehensive study of low temperature (< 1000 °C) oxidation process in SiGe/SOI structures

Abstract

Oxidation of SiGe/SOI (Ge fraction: 0–50%) structures was investigated in a wide temperature range. Different oxidation features were observed for samples oxidized in low (< 680 °C), middle (700–800 °C), and high (> 800 °C) temperature regions. Very thin SiO 2 layers (< 150 nm) were formed during low (< 680 °C) temperature oxidation. Thus, the Ge fractions at the SiO 2/SiGe interfaces were almost the same as the initial Ge fractions (< 50%). Therefore, the initial Ge fraction dependent enhanced oxidation was observed. On the other hand, very thick SiO 2 (> 200 nm) was formed during high (> 800 °C) temperature oxidation. Thus, the oxidation rate was limited by the diffusion process of O in SiO 2. Therefore, the oxidation rate did not depend on the Ge fraction. At middle temperatures, the oxidation rate does not depend on the temperature for samples with high initial Ge fractions (> 20%). This is due to that increase in oxidation rate by increasing temperature was cancelled by the retardation of oxidation due to high Ge fractions (> 50%) piled-up at the SiO 2/SiGe interfaces.