Patent ID: 8035071

Claim:
A contamination-inspecting apparatus for inspecting a wafer surface for a contaminant comprising: an irradiation optical system for irradiating the wafer surface with laser light; a detection optical system for detecting light scattered from the wafer surface; and a detection unit for converting the scattered light detected with the detection optical system into an electric signal to make a correction; wherein the detection unit has a plurality of detection circuits with different amplification factors; and wherein the detection unit has a means for correcting the electric signal by use of a piece of correction data derived from a difference in amplification factor between the plurality of detection circuits and held in advance; and wherein the detection unit has a switching means for switching between a piece of output data of a first detection circuit and a piece of data output by a second detection circuit and then corrected based on the piece of correction data thereby to selectively output the pieces of data, provided that the first and second detection circuits are each one of the plurality of detection circuits.