Lithographic apparatus and associated methods

Abstract

A lithographic method includes forming an image of a reticle on a substrate a plurality of times. Each such image formation process includes: illuminating a first portion of a reticle and pellicle assembly with a radiation beam; and projecting radiation scattered by the reticle onto a target region of a substrate using projection optics. The lithographic method further includes periodically illuminating a second portion of the reticle and pellicle assembly with a radiation beam, the second portion of the reticle and pellicle assembly at least partially surrounding the first portion. Some pellicles are susceptible to hydrogen etching and such pellicles tend to fail in a region surrounding a central portion. By periodically illuminating a second portion of the reticle and pellicle assembly with a radiation beam, hydrogen etching of the second portion of the reticle and pellicle assembly may be suppressed.

Dependencies are inferred from the claim text.