Method and apparatus for inspecting photomasks to detect defects

摘要

The present invention is directed to an improved method and apparatus for detecting defects in photomasks containing features with different arbitrary orientations, said apparatus including in one form therof a detector for detecting orientations of the features so that the optical signals from the features may be suppressed by suitable apparatus such as spatial filtering. The spatial filtering is adjusted electronically based on the determined orientation of the mask features. In one form of the invention the spatial filtering is effected by accepting photodetected signals from only a selected number of photodetectors in a photodetector array, the selection being determined by the orientation of the mask features.