Patent ID: 6980278

Claim:
A self-cleaning method for a semiconductor exposure apparatus comprising a light source for emitting ultraviolet light for exposure, an optical system for guiding ultraviolet light emitted from the light source to an exposure mask on which an exposure pattern is formed, and a projection lens for projecting the exposure pattern to a subject to be processed, the method comprising: arranging, at a position where the exposure mask is to be disposed, a transmittable plate for diffusing ultraviolet light guided by the optical system and irradiating the projection lens with it, the transmittable plate being made of a quartz glass plate having a lens-shaped concave portion on one surface thereof and bracelet-shaped concave lenses concentrically arranged on the other surface thereof; and irradiating an entire surface of the projection lens with the ultraviolet light emitted from the light source and diffused by the transmittable plate to optically clean a surface of the projection lens, and wherein the transmittable plate for self-cleaning includes a Fresnel lens made of a heat resistant transparent resin.