Thin Film Thickness Measurement of Whole Field Based on Spatial Carrier Frequency Interferometry

The kernel of modern interferometry is to the obtain necessary surface shape and parameter by processing interferogram with a reasonable algorithm. On the basis of the study the basic principle of interferometry by using 2-D FFT arithmetic, a new method to measure the thin film thickness is proposed based on the FFT algorithm. A test sample is placed into the light path in Twyman-Green interferometer, the interference fringes were generated by the reference beam with the tested beam reflected respectively from the film surface and the substrate surface. The interferogram is collected by the image acquisition system. The algorithm processing software is prepared to realize identification of the films edge, regional extension, filtering, unwrapping the wrapped phase etc, the film thickness distribution in whole field can be obtained to realize the thickness measurement of thin film samples automatically. The results indicate that the new method has the advantages of high precision, whole test and non-contact measurement.