Anisotropic incoherent reflection model for spectroscopic ellipsometry of a thick semitransparent anisotropic substrate

An anisotropic incoherent reflection model for the Mueller matrix elements of an optically thick uniaxial anisotropic semitransparent substrate with i ts anisotropy axis along its surface normal is developed. The Mueller matri x elements are measured by phase-modulated spectroscopic ellipsometry (SE) and compared with incoherent reflection model simulations. In the case of a sapphire substrate the oscillations observed are accurately modeled, and, in addition, the oscillating degree of polarization is correctly predicted. A straightforward generalization of the optical model, in the case of an a rbitrary stack of layers containing a thick anisotropic semitransparent sub strate, is also proposed and experimentally validated. The model is further applied to study the anisotropic dielectric function of a semi-insulating 4H-SiC wafer. An approximation based on a simple variation in the optical t ransition element is proposed to model the SiC birefringence. In conclusion , SE is shown to be a powerful alternative for investigating and predicting the behavior of optically thick birefringent materials. (C) 2000 Optical S ociety of America.