The possibilities of multi-angle spectrophotometry for determining the parameters of films on single-layer structures

Abstract

Single-layer Ta-Si-C-N films on fused quartz substrates were made by direct current magnetron sputtering. The structural perfection of the film was investigated by X-ray diffraction analysis, scanning electron microscopy and optical emission spectroscopy of glow discharge. The optical parameters of the films were determined by the method of multi-angle spectrophotometry. Spectral dependences of the transmission coefficients of substrates and structures at normal light incidence in the wavelength range of 200—2500 nm are obtained. It is shown that the transmission spectrum of the sample has an oscillating character, which is caused by interference phenomena characteristic of layered structures. Spectral dependences of the reflection coefficients of films and substrates in the wavelength range of 200—2500 nm at small angles of incidence of light are obtained. By the magnitude of the difference between the reflection coefficient at the maximum of the interference of the film and the corresponding reflection coefficient of the substrate at the same wavelength, it is shown that the absorption in the film is low. A formula is obtained for determining the absorption coefficient of a film from the measured parameters. Based on the experimental data obtained, spectral dependences of the absorption coefficients of the substrate, structure and film are constructed. The method of reflection at two angles of incidence, based on the determination of the position of the interference extremes on the spectral dependences of the reflection coefficients, calculated discrete values of the refractive coefficients in the wavelength range 400—1200 nm. The obtained values are approximated by the Cauchy equation. The film thickness was calculated, which was d = 1046 nm ± 13%. Spectral dependences of the film attenuation indices with and without reflection are constructed. A summary table is presented with the obtained values of the refractive coefficients and absorption indices with and without reflection.