Method and apparatus for redressing defective photomask

Abstract

A method and apparatus for repairing defect portions of a photomask. A complex material from which a light shading material can be deposited is applied over the photomask. A white (blank) defect region is irradiated with a continuous wave laser light beam projected in a slit-like light image to thereby convert the complex material into the shading material. After washing, a half-deposited portion formed in a peripheral portion of the light shading region is further deposited by a post-baking process. Those portions of the light shading film which depart from the desired mask pattern are removed together with black (solid) defect portion originally present in the photomask through irradiation with a pulse laser light beam. The pulse laser is constituted by a Dye-laser, while the continuous wave laser is constituted by an Ar-laser. A specific half-mirror which transmits therethrough Ar-laser light while reflecting Dye-laser light is displaceable provided. The white and the black defects are selectively centered on a same optical axis of an optical projection system including a slit and a condenser lens, whereby the white and the black defect portions are each removed through irradiation with the associated laser light projected thereto in a slit-like light image through the same optical projection system.