Patent ID: 7466853

Claim:
A method of detecting a defect on a substrate, the method comprising: irradiating a light on a substrate, wherein the substrate has a plurality of device units formed thereon with the same pattern, the plurality of device units each including a plurality of pixels; measuring image information for the plurality of pixels by sensing the light reflected by a surface of the substrate from the irradiating light; calculating a raw datum of a target pixel by subtracting the image information of a corresponding pixel from the image information of the target pixel, wherein the target pixel is a subject pixel for detecting a defect, and wherein the corresponding pixel is located in a first device unit that is adjacent to a second device unit that includes the target pixel, the corresponding pixel corresponding to the target pixel; presetting a threshold region including at least one pair of upper and lower limits; comparing the threshold region with the raw datum; and marking the target pixel as defective if the raw datum is within the threshold region.