Patent ID: 6100970
Filing Date: 2000-08-08
Classification: G01N,G03F

Abstract:
An apparatus for inspecting slight defects in a pattern of a photomask, an image of said pattern being projected onto an imaging position by using exposure light with an exposure wavelength, said pattern comprising light transmitting portions formed on a transparent base and light intercepting portions formed on the transparent base which transmit part of the exposure light a phase of which is delayed with respect to a phase of the illumination light passing through said light transmitting portions, said apparatus comprising:an X-Y table for supporting said photomask;an illumination light source radiating inspection light having an inspection wavelength different from the exposure wavelength onto said photomask;means for detecting defects in said pattern based on a signal obtained by illuminating said pattern with said inspection light, said inspection light satisfying the relational expressionT.gtoreq.(Thr-0.01).sup.1/1.8where T is a transmittance of said light intercepting portions with respect to said inspection light with the inspection wavelength, and Thr is a signal detection limit of an inspection circuit, given that a signal level of said inspection light passing through said light transmitting portions is 1.