Influence of thickness distribution on spectroscopic ellipsometry of SOS

Abstract

The influence of thickness distribution on spectroscopic ellipsometry (SE) of silicon on sapphire (SOS) was studied. The measured optical spectra (Ψ and Δ) of epitaxial Si and polycrystalline Si films were fitted with a multilayer structure, ambient/native oxide/silicon/Al2O3. In the analysis of the Ψ and Δ spectra, the model dielectric functions proposed for Si were used for both epitaxial Si and polycrystalline Si films, and in addition established optical constants of Si were used for epitaxial Si film. The thickness distribution of the Si layer was taken into account in the calculation of Ψ and Δ spectra using an arbitrary thickness distribution function. It was found that the measured optical properties of these silicon films can be explained well by the assumed thickness distribution of the silicon layer.