Study on thin film thickness measurement method based on digital image processing

Digital Image Processing has many advantages of large image information, high precision, rich content, complex nonlinear processing and integrated performance and so on. Application of digital image processing in the film thickness measurement is deeply researched in this paper and the actual thickness of the SiO2 thin film is detected. In MATLAB environment, the surface morphology of the tested film was obtained after several image processing to the interferogram of the thin film sample which is obtained by CCD with high resolution, including reducing the noise, recognizing the edge, spreading the region, doing two-dimensional Fourier transform and unwrapping the phase. On this basis, the thin film thickness is obtained through extracting the section in the special place corresponding to the information of the thin film thickness with certain step length from the 3-D topography and making data processing and analysis. The results indicate that the thin film thickness used the method in this paper can reach good measurement accuracy with its error less than 2 nm.