Study On Technology Of Thin Film Thickness Measurement Based On Interferometry Fringe

With the extensive using of thin film devices, especially the widespread of the weapon system upgrade process, the enhancement of film properties, the evaluation of the Film of the pros and cons put forward higher requirements. Accurate detection of the film thickness became the focus of attention. Therefore, the combination of image acquisition technology and digital image processing technology will be the best solution for the high efficiency and high-precision film thickness measurements.In this paper,the measured thin film interference fringes samples are achieved by using Twyman-Green interferometer system. Firstly, the image of the interference fringes need prepossessing which is including noise reduction and edge extraction. Secondly, the OTSU calculate the pretreated interference pattern image segmentation threshold and select the optimal threshold for image binarization. Thirdly, the interference images thinning algorithm based on Mathematical morphology is proposed to calculate the thin film samples which is binaried used in this paper. Finally, by refined fringes quadratic curve fitting, the final film thickness is calculated by interference fringes fractional part and integer part. The entire process using Matlab software program for processing, automated measurement of film thickness, replace the traditional skilled workers and high-intensity long hours of work to enhance the film thickness measurement accuracy.The different interference film samples which are coated in the vacuum environment using the proposed algorithm, the analysis results were compared with the results which tested by ZYGO interferometer used the same film samples. The results showed that:ZYGO interferometer measures one of the SiO2 thin film samples and the mean thickness is 164.6nm. This algorithm processes the same film sample and the mean thickness is 165.9nm. Because the environmental parameters correction value is 0.00157nm which is accounting for the measurement of the average film thickness of 0.009‰, the correction is negligible.Experiments show that the interference method for measuring film thickness is feasible and is greatly improving the accuracy of the measurement of film thickness. The method can solve most of the optical detection of interferogram processing problem.