Patent ID: 7514274

Claim:
A method comprising: storing a reference image of a test structure, said test structure comprising a first set of features and a second set of features, said first set of features comprising a subset that is extracted from product features to be monitored in a chip, said second set of features comprising a rotating, space scaling, and linewidth scaling of said first set of features, said second set disposed adjacent to said first set, said second set representing 3 to 15 percent of said first set, said second set being distinguishable from other similar structures in the vicinity to provide uniqueness to said test structure; loading a sample on a stage; moving said stage; focusing and fine-tuning a test image of said test structure on said sample; capturing said test image; scanning a plurality of portions of said test image; performing pattern recognition of each of said portions; evaluating similarity of said test image to said reference image; determining a score for each of said portions; ranking said portions from highest score to lowest score; and determining location on said sample of said portion with highest score.