Characterization of Biaxial Strained-Silicon by Spectroscopic Ellipsometry

Abstract

Spectroscopic ellipsometry (SE) and synchrotron x-ray scattering have been applied to the non-destructive characterization of biaxial tensile strained silicon (ξ-Si). SE data from 250nm - 500nm were acquired from three epitaxial ξ-Si samples grown on silicon germanium (SiGe) virtual substrates by chemical vapor deposition (CVD). The SE data was fitted by a two-step procedure using a parametric dielectric function model for crystalline semiconductors and structural data obtained separately from X-ray scattering. By monitoring the shift of the E1 critical point in the fitted dielectric function spectrum, the tensile strain of ξ-Si can be determined from known elastic constants and deformation potentials of Si. Strain values obtained are generally in agreement with Raman measurements. The structural characteristic of the sample with the highest germanium concentration in the virtual substrate was further studied by reciprocal space mapping (RSM) and atomic force microscopy.