Apparatus for detecting defects in patterns

摘要

An apparatus for detecting defects in patterns, particularly defects in chip patterns of photomasks for use in manufacturing semiconductor integrated circuits comprising an optically scanning means for scanning identical portions of the two patterns to be compared with each other with a pair of scanning light spots to produce a pair of picture signals each corresponding to a respective one of the scanned pattern portions; and a defect detecting section for receiving said pair of picture signals and producing a defect signal as a difference between the two picture signals. In order to remove pseudo-defects which appear in the vicinity of contours of the patterns mainly due to registration error between the two patterns there are further provided a contour signal producing section for receiving at least one of said pair of picture signals to produce a contour signal having a given width and a control section for receiving said contour signal and decreasing a defect detection sensitivity in the vicinity of the pattern contours. In an embodiment of the control section it comprises a gate which is controlled by the contour signal in such a manner that the defect signal from the defect detecting signal is blocked by the gate while the contour signal is supplied from the contour signal generating section. In this embodiment the sensitivity for defect detection in the vicinity of the contours of patterns is decreased to zero.