Thickness determination of thin polycrystalline film by grazing incidence X-ray diffraction

Three methods of thickness measurement based on absorption of X-rays in thin films were tested on polycrystalline titanium nitride film deposited on tungsten carbide substrate. The intensities of three reflections from each material were measured in the incidence range from 3∘ to 35∘ of the primary beam. After experimental correction for texture effects, data from the TiN film, the WC substrate or from their ratio were fitted by known functions using least squares routines. The substrate reflection intensities were found to be the most suitable for determining the thickness of the overlaying thin film. The average thickness of TiN film (2.0 ± 0.16 μm) determined from the substrate reflections was in fair agreement with the average value obtained from optical microscopy (2.2 ± 0.8 μm). The use of substrate reflections is generally preferable unless their intensities are spoiled by statistical errors (e.g., low intensity, grain size effect, texture etc.). The method based on the ratio thin-film/substrate reflection intensities is not complicated by correlation of the least square parameters but suffers strongly from accumulated experimental errors.