Characterization of biaxial stressed silicon by spectroscopic ellipsometry and synchrotron x-ray scattering

Abstract

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