Patent attributes
An apparatus for inspecting foreign matter on substrates on which circuit patterns, such as reticles or masks, are formed, reduces false detection due to scattered/diffracted light from circuit patterns and also reduces the occurrence of undetected foreign matters. A light source such as a scanning laser beam having a certain polarization angle to the surface of an inspection object substrate is provided. A main detector extinguishes scattered/diffracted light caused by a circuit pattern formed on the surface of the inspection substrate and detects an output signal. A reference detector transmits scattered/diffracted light caused by the circuit pattern, and detects an output signal. A signal processor calculates a difference signal by subtracting the intensity of a polarization component detected by the reference detector from the intensity of a polarization component detected by the main detector, and discriminates a signal with a large width caused by the circuit pattern and a signal with an acute peak caused by foreign matter.
