PATTERN RECOGNIZING METHOD

摘要

PURPOSE:To make a pattern alignment accuracy smaller than the size of a detected pixel and reduce the effect of sampling errors by extracting and comparing the errors of two patterns whose positions are aligned with each other with the accuracy not larger than the size of one pixel. CONSTITUTION:The pattern of a wafer 1 illuminated by a light source 3 and an illumination optical system 4 in synchronism with the scanning of an X-Y stage under a command from a total controller 21 is photoelectrically converted by a one- dimensional image sensor 6 via an objective lens 5 to detect a two-dimensional pattern and a binary-coded 7 two-dimensional picture image 10 is obtained to be stored 8. A matching unit 13 calculates a difference between the detected picture image 10 and a comparison picture image 11 and outputs the picture image 14 wherein pixel unit position correction is terminated. Then, a sub-pixel matching unit 15 calculates the position alignment quantity of not larger than the size of a pixel. A position aligning unit 16 conducts position alignment on the basis of a position alignment quantity. A picture image extracting unit 18 extracts a difference picture image from the picture image wherein a position correction is terminated. The difference image 17 is binary-coded at a threshold value in a defect decision unit 19, a variety of characteristic quantities are extracted and defect decision is performed.