Observation of Crystalline Imperfections in Supercritical Thickness Strained Silicon on Insulator Wafers by Synchrotron X-ray Topography

A commercial supercritical thickness strained Si-on-insulator (SC-sSOI) wafer was characterized by large-area synchrotron x-ray topography at the glancing incident condition. Several kinds of contrast showing crystalline imperfections were observed all over the wafers, such as macule and crosshatch patterns. Similar crosshatch patterns were also observed in the x-ray topographs of a conventional strained Si-on-insulator (sSOI) wafer and a strained Si wafer that has the strained Si layer epitaxially grown on the relaxed SiGe layer on the insulator (SGOI) structure. This indicates that the crosshatch pattern of the SC-sSOI wafer originates from the lattice distortion in the original SiGe substrate of the strained Si layer.