Study of SiGe oxidation kinetics for preferential SiO2 formation under a low O2 pressure condition

TLDR: In this article, the authors studied the oxidation kinetics of SiGe as parameters of O2 pressure and temperature and found that Si was predominantly oxidized in the Si 0.5Ge0.5 oxidation under lower O2 pressures.

Abstract: We have studied the oxidation kinetics of SiGe as parameters of O2 pressure and temperature. This paper first discusses the SiGe oxidation experimentally and thermodynamically. It was found that Si was predominantly oxidized in the Si0.5Ge0.5 oxidation under lower O2 pressures. This fact is thermodynamically reasonable, but the Ge remaining after Si oxidation may be a big concern in terms of SiGe gate stacks, because it should form defects at the interface or inside the SiO2 film. Therefore, it is critically important to understand how the Ge atoms behave after the SiO2 formation. Second, the GeO2/Si reaction, which might be a key part to well controlled SiGe gate stacks in the preferential SiO2 formation, is discussed. Two kinds of metallic Ge formation kinetics at the SiGe interface in the annealing of GeO2/Si are conjectured: One is the metallic Ge diffusion into the Si substrate and the other is the Ge precipitation at the interface, which should be avoided for improving the SiGe interface properties. The experimental results indicate that the former case is made possible by annealing under the low O2 pressure condition in a very thin SiO2 formation region.