Microscopic Ellipsometric Analysis of Thin Films Formed by Chemical Vapor Deposition

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A microscopic ellipsometer which equips two groups of lenses behind the computer-aided rotating analyzer for magnifying the reflection image of the specimen, in addition to a polarizer-sample-analyzer configuration. This combination of lenses can provide a maximum magnification of ca. 1000 times and makes it possible to determine the thickness and optical constant of a thin surface film on an area of ca. 3um in diameter. Using this ellipsometer the spatial distributions of film thickness and optical constant have been measured for the films of BN, TiN and SiO_2 formed on polycrystalline Pt substrate by plasma-enhanced chemical vapor deposition(PECVD). The corresponding distributions of plasma parameters, the electron density and electron temperature, were measured using a Langmuir probe technique. It was found that the film thickness depended remarkably on the grain orientation of the substrate, while the optical constant was almost independent of the grain orientation. The distribution of film thickness within each grain was less significant. The electron density and electron temperature of plasma were, almost constant over the area of the substrate, 25mmXl5mm. It is-therefore thought that the spatial distributions of film thickness arise from differences in the catalytic activity of individual grains of the substrate.