Foreign particle inspection apparatus and method with front and back

Abstract

A method of inspecting a phase shift reticle comprising a transparent or translucent substrate, a circuit pattern of an opaque film formed on the front surface of the substrate and a pattern of a transparent or translucent film formed on the front surface of the substrate comprises: obliquely projecting a front illuminating light beam on the front surface of the substrate by a front illuminating system; concentrating scattered light scattered by the surface of the substrate and the surfaces of the patterns, obliquely projecting a back illuminating light beam on the back surface of the substrate by a back illuminating system, concentrating transmitted-and-diffracted light transmitted and diffracted by the substrate and the patterns; intercepting the scattered light scattered by the patterns and the transmitted-and-diffracted light transmitted and diffracted by the patterns with spatial filters disposed on Fourier transform planes, focusing the scattered light and the transmitted-and-diffracted light transmitted by the spatial filters on detectors; and comparing detection signals provided by the detectors to see if there are any foreign particles on the phase shift reticle.