Owing to reduction of LSI device pattern, verification of mask pattern after optical proximity correction, OPC, by using
Litho-Simulation becomes common practice. The verification using Litho-Simulation does not only increase reliability,
but also the verification time. To solve this problem, we extract error patterns and categorize them, and we review only
the representative pattern of each category to save time. But further reduction of device pattern might increase the
verification time. There is loose matching method to save the time, but it has a week point such that accuracy of
categorization is trade-off with error pattern number to be reviewed.
We tried a method of categorization referring to original pattern, CROP. The CROP method categorizes error patterns
referring to original pattern extracted by the position data of the error pattern. For this reason, categorization of error
patterns is accurate, and the number category of a product pattern is reduced to1/50 compared with pattern matching
method, which is loose matching method with 0 nm matching size.