Patent ID: 9279969
Filing Date: 2016-03-08
CPC Classification: G02B,G03F

Claim Text:
1. A catadioptric projection objective for microlithography for imaging an object field in an object plane onto an image field in an image plane when the object field is illuminated with radiation, comprising: a first partial objective for imaging the object field onto a first real intermediate image; a second partial objective for imaging the first intermediate image onto a second real intermediate image, wherein the second partial objective is a catadioptric partial objective having exactly one concave mirror and having at least one lens; a third partial objective for imaging the second intermediate image onto the image field, the third partial objective comprising an aperture stop and no more than four lenses between the aperture stop and the image plane; and a first folding mirror for deflecting the radiation from the object plane toward the concave mirror and a second folding mirror for deflecting the radiation from the concave mirror toward the image plane; wherein the catadioptric projection objective is an immersion projection objective in which during operation an immersion liquid is situated between a last lens surface and the image plane, and at least one surface of the at least one lens in the second partial objective has an antireflection coating comprising at least six layers.