Interpretation of UV reflectance measurements on silicon on sapphire by spectral reflectance and ellipsometry studies

Spectral reflectance and spectroscopic ellipsometry measurements have been made on SOS wafers with haze ratings 1-5. The wavelength dependence of reflectance is dominated by surface scattering, but degraded crystallinity effects are also observed, and are significant in some samples. Analysis of dielectric function spectra using an effective medium approximation has indicated the presence of α-Si and voids in surface layers up to 300Å thick in medium haze wafers, with concentrations decreasing away from the surface. The assessment parameter normally used for SOS, UVR No., has been shown to includeboth crystallinity and scattering effects, and their relative importance cannot be determined without more detailed measurements.