Imaging defects in strained-silicon thin films by glancing-incidence x-ray topography

Abstract

X-ray topographical images from thin (⩽50nm) strained-Si films grown on relaxed, planarized crystalline SiGe-on-Si (001) virtual substrates have been imaged by glancing-incidence monochromatic x-ray topography. This extremely asymmetric diffraction geometry, utilizing (311) diffraction planes, can limit penetration into the sample to as little as 6nm and allows separate images from the thin strained-Si film, the SiGe layer, and the base Si wafer to be recorded at different angles above the critical angle. Strain fields from the misfit dislocations in the SiGe layer penetrate the Si wafer and act as a template for the defect structure of the strained-Si films, even after an ex situ planarization step was inserted during the growth of the SiGe layer. This defect structure remains in the strained-Si film throughout the fabrication of strained-Si-on-insulator substrates.