X-ray-diffraction characterization of silicon-on-insulator films

Abstract

Silicon-on-insulator layers produced by the processes of oxygen implantation into single-crystal silicon substrates, zone melt recrystallization of deposited polysilicon films, and silicon epitaxy on sapphire substrates have been examined by an improved x-ray-diffraction technique. The technique incorporates a position-sensitive x-ray detector placed on the 2θ arm of a conventional double-crystal diffractometer, thus allowing the measurement of scattered x-ray intensity in both the incident and diffracted x-ray beam angles simultaneously. X-ray scattering intensity maps plotted in k space reveal the relative strain and mosaic spread of the silicon overlayers with respect to the (001) silicon substrates. Oxygen-implanted films and graphite strip recrystallized films exhibit mosaic spreads (<±0.08° and ±0.05°, respectively) approaching that of bulk single-crystal Si. The electron-beam-recrystallized films exhibit significantly larger mosaic spreads (≊±0.52°). These silicon overlayer films all exhibit similar perpendicular strain values with an average of approximately 0.08%. Silicon layers produced by both zone melt recrystallization techniques contain a preferential tilt of the diffraction planes along the recrystallization scan direction with respect to the underlying (001)-oriented silicon substrate. Silicon-on-sapphire samples exhibit both a large mosaic spread (±0.18°) and a large perpendicular strain (0.13%). These x-ray results are consistent with crystalline data taken by backscattered electron images and Rutherford ion backscattering.