Thermal stability of strained Si/Si1-xGex/Si structures

Abstract
The thermal stability of strained Si1-xGex layers grown epitaxially by molecular beam epitaxy on Si(100) and capped by a Si top layer was studied using Rutherford backscattering spectrometry. Diffusion coefficients were evaluated from the Ge scattering profiles of a 50 nm SiGe film, capped with 50 nm Si, for anneal temperatures between 850 degrees C and 1010 degrees C. The diffusion coefficient, calculated from the increase in signal in the tail of the Ge profile, proved to be comparable with the value for Ge in bulk Si. An enhanced decrease in signal at the centre of the Ge profile indicated a faster diffusion within the SiGe layer. This was confirmed by analysis of the FWHM of the Ge profile, from which a diffusion coefficient was derived which was up to 20 times higher.