A self-reliance technique is developed for detecting defects in repeated pattern wafers and masks with low-order distortions. If the patterns are located on a perfect rectangular grid, it is possible to estimate the period of repeated patterns in both directions, and then produce a defect-free reference image for making comparison with the actual image. But in some applications, the repeated patterns are somehow shifted from their desired position on a rectangular grid, and the aforementioned algorithm cannot be directly applied. In these situations, to produce a defect-free reference image and locate the defected cells, it is necessary to estimate the amount of misalignment of each cell beforehand. The proposed technique first estimates the misalignment of repeated patterns in each row and column. After estimating the location of all cells in the image, a defect-free reference image is generated by averaging over all the cells and is compared with the input image to localize the possible defects.

Date Published: 11 March 1994
PDF: 7 pages
Proc. SPIE 2183, Machine Vision Applications in Industrial Inspection II, (11 March 1994); doi: 10.1117/12.171210

Published in SPIE Proceedings Vol. 2183:
Machine Vision Applications in Industrial Inspection II
Benjamin M. Dawson; Stephen S. Wilson; Frederick Y. Wu, Editor(s)