METHOD FOR LASER ALIGNMENT IN MASK REPAIR

A laser mask repair uses an alignment process comprising the step of normalized pattern matching between a search area encircling a matrix of contact holes including a defective contact hole and reference area encircling a similar matrix of contact holes including a correct contact hole. A slit image is first aligned with the center of the correct contact hole, then shifted to the center of the defective contact hole. The alignment light beam passing through the slit is replaced by a repair laser beam. The defective contact hole is repaired by the laser beam having the slit size equal to the size of the correct contact hole.