Patent ID: 7483128

Claim:
A foreign matter inspection apparatus comprising: a light source for irradiating, while scanning, a laser beam having a predetermined polarization angle to the surface of an inspection object substrate; a main detector which includes a main optical unit for extinguishing scattered/diffracted light caused by a circuit pattern formed on the surface of the inspection object substrate among scattered/diffracted light generated on the surface of the inspection object substrate along with irradiation of the laser beam, and includes a first polarization member and detects an output signal from the main optical unit; a reference detector which has a reference optical unit for transmitting scattered/diffracted light caused by the circuit pattern, and includes a second polarization member having a different polarization component than a first polarization component and detects an output signal from the reference optical unit; and a signal processor for calculating a difference signal by subtracting the intensity of the polarization component detected by the reference detector from the intensity of the polarization component detected by the main detector, and obtaining a second difference signal between a first signal including a signal with a large width caused by the circuit pattern and a signal with an acute peak caused by foreign matter and a second signal that cuts off the signal with the acute peak with a filter, and comparing the value of the second difference signal with a threshold value to determine the presence of foreign matter.