Ellipsometry applied to films on dielectric substrates

Abstract

The thickness and refractive index of thin dielectric films deposited in vacuo on silica substrates have been determined using a photoelectric ellipsometer. The ellipsometer utilised Faraday effect modulation and a description is given of some novel achromatic quarter-wave retardation systems. Thickness values obtained by ellipsometry have been compared with step height measurements made on the same films by both optical and mechanical methods. The agreement between ellipsometric and step height thickness was often poor and was considered to be due to film inhomogeneity, i.e. variation in refractive index through the thickness of the film. Further ellipsometric measurements on similar films deposited on other dielectric and metallic substrates supported the hypothesis of film inhomogeneity.