Precise Measurement of Thickness Distribution of Non- Uniform Thin Films by Imaging Spectroscopic Reflectometry

− A new method of imaging spectroscopic photometry enabling us to perform the complete optical characterization of thin films exhibiting area non-uniformity in optical parameters is presented. An original imaging spectroscopic photometer operating in the reflection mode at normal incidence is used to apply this method. A CCD camera serves as a detector in this photometer. Therefore the spectral dependences of the reflectance of the films characterized are simultaneously measured in small areas of the films surface corresponding to the individual pixels of the CCD camera. These areas form a matrix along a relatively large part of the films surface. The spectral reflectance measured by the individual pixels of the CCD camera is treated separately using the formulae for the reflectance corresponding to the uniform thin films. Using these formulae it is possible to determine the values of the local thickness and local optical constants for every small area of the matrix. In this way it is possible to determine distributions (maps) of the local thickness and local optical constants of the non-uniform films simultaneously in principle. The method described was used to characterize carbon-nitride thin films exhibiting only the thickness nonuniformity deposited by the method of dielectric barrier discharge onto the silicon single crystal substrates.