Patent ID: 8705007
Filing Date: 2014-04-22
Classification: G01J,G01N,G03F

Abstract:
1. An inspection apparatus configured to measure a property of a substrate, the apparatus comprising: an illumination system configured to provide a beam of radiation; a radiation projector configured to project the beam of radiation onto the substrate; a numerical aperture lens; a substrate comprising a mark with a line of symmetry that is parallel to and in alignment with a plane of symmetry of an illumination profile of the beam of radiation projected by the radiation projector, wherein the illumination profile comprises two quadrants spaced apart from each other, the two quadrants being substantially illuminated; and a detector configured to detect the radiation beam reflected from a surface of the substrate and separately detect a zeroth diffraction order and a higher diffraction order, wherein the illumination profile is such that at least one characteristic of the mark is reconstructed using the separately detected zeroth diffraction order and the higher diffraction order.