Patent ID: 6768543
Filing Date: 2004-07-27
Classification: G01N

Abstract:
A method of inspecting a surface of a substrate having periodic or non-periodic structures comprising:directing light onto the surface of the substrate using polarizing beam splitters and mirrors that are configured to propagate the light beam in two planes of incidence, said two planes of incidence being generally orthogonal; directing light appropriately so that the polarizing beam splitters and mirrors generate a counter propagating light beam that travels through corresponding two planes of incidence; using detectors to sense light diffracted by features on the surface wherein the diffracted light of zero order, specular reflection, or higher order originate from each one of the counter propagating beams; obtaining detector signals from the detectors; and determining presence or absence of a defect by processing the detector signals corresponding to diffraction signals generated by the counter propagating beams.