METHOD FOR DEFECT INSPECTION

A method for defect inspection includes receiving a substrate having a plurality of patterns; obtaining a gray scale image of the substrate, wherein the gray scale image includes a plurality of regions, and each of the regions has a gray scale value; comparing the gray scale value of each region to a gray scale references to define a first group, a second group and an Nth group, wherein each of the first group, the second group and the Nth group has at least a region; performing a calculation to obtain a score; and when the score is greater than a value, the substrate is determined to have an ESD defect, and when the score is less than the value, the substrate is determined to be free of the ESD defect.