Comprehensive Study Of Low Temperature (<1000 ℃) Oxidation Process In Sige/soi Structures

摘要

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 ℃), middle (700-800 ℃), and high (>800 ℃) temperature regions. Very thin SiO_2 layers (<150 nm) were formed during low (<680 ℃) 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 ℃) 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.