EXAMINATION OF THIN SIO2-FILMS ON SI USING SPECTROSCOPIC POLARIZATION MODULATION ELLIPSOMETRY

A series of SiO2 films with thicknesses varying from 3 to 325 nm have been grown on silicon using standard dry oxygen growth techniques and examined using the two-channel polarization modulation ellipsometer, which has increased sensitivity for very thin insulating films on silicon. Using a biased estimator fitting technique, the ellipsometric data are fit to either an air-SiO2-Si model or an air-SiO2-interface-Si model, where the optical functions of the SiO2 layer are approximated using an isotropic one-term Sellmeier approximation. The results from the one-term Sellmeier approximation show that the refractive index of the SiO2 layer increases with decreasing film thickness, while the interfacial layer thickness decreases with decreasing film thickness.