Fabrication of thick SiGe on insulator (Si0.2Ge0.8OI) by condensation of SiGe∕Si superlattice grown on silicon on insulator

Abstract

In this work, the authors demonstrate a fabrication methodology for obtaining a thick (∼250nm) high Ge content SiGe-on-insulator (SGOI) film. About 800nm thick low Ge content (∼25%) SGOI film was fabricated by intermixing SiGe and Si through thermal annealing of a superlattice comprising of 60 periods of Si0.7Ge0.3 and Si on silicon-on-insulator (SOI) substrate. A combination of oxidation and annealing processes was used to condense and diffuse the Ge through SiGe film to obtain thick Si0.2Ge0.8OI. It is also found that the oxidation termination is due to residual stress in the thick SGOI layer. The transmission electron microscopy measurements showed that the Si0.2Ge0.8OI film exhibits a single crystalline nature with an orientation that is the same as the starting SOI. X-ray diffraction measurements confirmed that the in-plane strain of the SGOI layers is compressive or nearly relaxed.