Patent ID: 7952085

Claim:
A defect inspection apparatus comprising: a first illumination optical system which is configured to illuminate an inspection area on a sample surface from a normal line direction or a direction near thereof with respect to said sample surface; a second illumination optical system which is configured to illuminate said inspection area from a slant direction with respect to said sample surface; a detection optical system having a plurality of first detectors including: at least one front detector located in front of said inspection area to detect light scattered to a front direction from the inspection area, at least two side detectors respectively located on sides of said inspection area to detect light scattered to side directions from the inspection area, and a back detector located behind said inspection area to detect light scattered to a back direction from the inspection area, respectively, with respect to the illumination direction of said second illumination optical system, and where a regular reflected light component, from said sample surface, resultant from illumination light of said second illumination optical system, is not converged by the detection optical system; and a signal processing system which is configured to inspect a defect, by processing signals obtained from said plurality of first detectors; wherein the signal processing system detects a large scratch by comparing a signal ratio with a predetermined threshold, said signal ratio is calculated from two signals among signals output from the first detectors and one of the two signals is output from a detector which detects a strongest light scattered from the inspection area on the sample among lights detected by the first detectors and the other signal is output from another detector among the first detectors.