Patent ID: 8106355

Claim:
An apparatus for automated inspection of a substrate comprising: a movable stage configured to hold the substrate having a repeating pattern of cells formed on a surface thereof; stage electronics configured to control the movable stage; a controller including a processor and memory; a controllable beam source for generating a beam and scanning the beam over the surface of the substrate; a detector for detecting image data; processor-executable code configured to control the stage electronics to move the substrate under the beam using a continuous motion in a substrate-translation direction; processor-executable code configured to scan the beam over the surface of the substrate and collect corresponding image data, wherein scan lines of the scan are in a scan-line direction perpendicular to the substrate-translation direction; processor-executable code configured to select from the image data a first pair of two cells of the repeating pattern on the surface of the substrate, wherein the two cells in the first pair comprise a candidate cell and a reference cell; processor-executable code configured to generate a first difference image by subtracting image data from said two cells of the first pair on a pixel-by-pixel basis; processor-executable code configured to select from the image data a second pair of two cells of the repeating pattern on the surface of the substrate, wherein one of the two cells is the candidate cell of the first pair, and wherein the two cells in the second pair are displaced from each other by one or multiple cell widths in the substrate-translation direction; processor-executable code configured to generate a second difference image by subtracting image data from said two cells of the second pair on a pixel-by-pixel basis; and processor-executable code configured to verify a defect found in the candidate cell using the first difference image if the defect is also found in the second difference image.