Patent ID: 9726979
Date: 2017-08-08
CPC Classifications: G02B,G03F

Claim:
1. A catadioptric projection objective for imaging a pattern, which is arranged on an object plane of the projection objective, to an image plane of the projection objective when the pattern is illuminated with ultraviolet light, the projection objective comprising: a first objective part for imaging the pattern to a first intermediate image; a second objective part comprising at least two optical elements for imaging the first intermediate image to a second intermediate image, the at least two optical elements comprising a concave mirror; and a third objective part for imaging the second intermediate image to the image plane, wherein: at least one of the optical elements in the second objective part is positioned in a path of ultraviolet light from the pattern between the concave mirror and the second intermediate image; the concave mirror is an active mirror comprising manipulators to manipulate the concave mirror; the third objective part comprises a first lens group having a positive refractive power, a second lens group immediately following the first lens group and having negative refractive power, a third lens group immediately following the second lens group and having positive refractive power, a fourth lens group immediately following the third lens group and having positive refractive power, and an aperture stop which is arranged between the third lens group and the fourth lens group, wherein the imaging by the projection objective defines a marginal ray having a marginal ray height, and wherein the marginal ray height has a point of inflection in the third objective part between the second intermediate image and the aperture stop, and wherein the catadioptric projection objective has an image-side numerical aperture of at least 1.25 up to and including 1.35.