Defect compensation method for smoothing a surface of a transparent plate with an ArF excimer laser beam

Abstract

A defect compensation method for smoothing a surface of a transparent plate by radiating an ArF excimer laser beam to a defect at the surface. The ArF excimer laser beam is radiated by use of a mask having an opening which is shaped in accordance with the shape of the defect, through a lens, or while the size of the beam at the defect is changed to a plurality of values. As the mask, an iris mask having an opening which is larger than the defect is usable. The size of the beam is changed by exchanging, a plurality of masks each having an opening of a different size from one another, or by use of a mask having a plurality of openings of different sizes. Alternatively, the ArF excimer laser beam is radiated so as to have an energy which is high at a center and low at a periphery of the defect. Or, the ArF excimer laser beam has a smaller size than the size of the defect, and the transparent plate having the defect is moved so as to allow different portions of the defect to be irradiated sequentially by the ArF excimer laser beam and simultaneously the number of shots of the ArF excimer laser beam is changed.

Dependencies are inferred from the claim text.