A Study on Oxidation Behavior of Poly-Si1 xGex Films

We have investigated the oxidation behavior of poly-Si1−xGex films with 20 %, 40 %, and 60 % Ge content in both dry and wet oxygen ambient. Poly-Si1−xGex films with various compositions and about 1000 A in thickness were deposited on oxidized Si wafers (with 1000 A thick thermal SiO2). Oxidation was carried out in a conventional tube furnace at 800 ◦C. The composition and thickness of the oxide were analyzed by RBS using rump simulation. The redistribution and chemical bonding of Si, Ge, and O elements were analyzed by XPS. The microstructure and phases formed in the films were analyzed by HR-TEM. In this study, it was found that Si was oxidized preferentially when the content of Ge in the alloy was low (20 %, 40 %). SiO2 was formed on the poly-Si1−xGex films, rejecting Ge and the oxidation rate of the poly-Si1−xGex films depends weakly on the Ge concentration. On the other hand, Si and Ge were oxidized simultaneously when the content of Ge was high (60 %). The formation of a mixed oxide layer on the poly-Si1−xGex films was observed. It was also found that oxide surface has a tendency to be flat from the initial oxidation stage due to the fast oxidation rate of Ge-rich films.