PROJECTION OBJECTIVE FOR MICROLITHOGRAPHY

摘要

An optical system comprising an illumination optics and a projection objective (16) for microlithography is used for imaging an object field (4) in an object plane (5) into an image field (8) in an image plane (9). The illumination optics (6) is designed in such a way that the illumination light (3) has an intermediate focus (23) between the light source (2) and the object field (4). A ratio between overall length (T) of the projection objective (16) and an intermediate-focus image shift (D) is smaller than 3. By use of such an optical system, reflection losses are reduced to a minimum when guiding the illumination light.