Patent ID: 9134618
Filing Date: 2015-09-15
Classification: G02B,G03F

Abstract:
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, wherein all elements in the first objective part having optical power to image the pattern from the object plane to the first intermediate image are refractive elements, a second objective part for imaging the first intermediate image to a second intermediate image, wherein the second objective part comprises a single concave mirror, a third objective part for imaging the second intermediate image to the image plane, and a first folding mirror for deflecting the ultraviolet light toward the concave mirror and a second folding mirror for deflecting the ultraviolet light from the concave mirror to a first lens group in the third objective part having a positive power, wherein the third objective part comprises the first lens group having positive refractive power, a second lens group, which immediately follows the first lens group and has a negative refractive power, a third lens group which immediately follows the second lens group and has a positive refractive power, a fourth lens group which immediately follows the third lens group and has a positive refractive power, and an aperture stop which is arranged in a transitional region from the third lens group to the fourth lens group, wherein the fourth lens group comprises fewer than five lenses, and wherein the first, second, and third objective parts are configured such that during operation of the projection objective with water as an immersion liquid between the third objective part and the image plane, the projection objective has an image-side numerical aperture NA of at least 1.2.