METHOD AND APPARATUS FOR OVERLAY MEASURING

摘要

PROBLEM TO BE SOLVED: To enable a simple measurement with good cost efficiency to be performed by converting the image of a repeat overlay mark into a phase image by an image processor, and analyzing the phase difference between repeat overlay marks on different levels in overlay measurement. SOLUTION: A digitizer 43 digitizes a first photo to generate a first digitized image. The digitizer 43 digitizes a second photo to generate an image. A Fourier transformer 45 transforms the second digitized image to a second geometric spectrum or a phase image. A phase comparator 48 calculates a phae difference between the first and second geometric spectra to measure alignment between two levels on a wafer 33. The digitizer 43 generates respective digitized images from a first and second portions of the photo. A signal processor 45 transforms the first and second digitized images to first and second geometric spectra. The phase comparator 48 calculates a phase difference between two geometric spectra to execute alignment measurement.