Patent ID: 7697130

Claim:
A surface inspection apparatus, comprising: a stage for supporting and horizontally moving a wafer; an optical system for projecting and enlarging light reflected from a surface of the wafer supported on the stage; an image acquisition system for acquiring image data of the wafer surface from the light obtained by the optical system; an image processing unit for processing an image corresponding to the wafer surface by using the image data acquired in the image acquisition system; a defect-detecting unit for detecting defects of the wafer surface present in the image processed in the image processing unit; a defect density-counting unit for computing a density of the defects detected by the defect-detecting unit; a density comparison unit for comparing a corresponding defect density of the image computed in the defect density-counting unit with a previous defect density acquired in a preceding defect measurement; and a scanning speed decision unit for varying a horizontal moving speed of the stage for a subsequent defect measurement on the basis of a difference between the corresponding defect density and the previous defect density, so as to control a wafer scanning speed, wherein when the corresponding defect density is higher than the previous defect density, the scanning speed decision unit reduces a horizontal moving speed of the stage, and when the corresponding defect density is lower than the previous defect density, the scanning speed decision unit increases a horizontal moving speed of the stage.