Catadioptric projection objective with parallel, offset optical axes

Abstract

A projection objective configured to image an object field in an object plane into an image field in an image field plane includes a reflective unit, a first refractive unit, and a second refractive unit. An optical axis of the first refractive unit is parallel to but displaced from an optical axis of the second refractive unit. The reflective unit includes a first curved mirror and a second curved mirror. The second curved mirror is immediately downstream from the first curved mirror in a path of light from the object plane to the image plane. The projection objective is a microlithography projection objective.

1 - 16 . (canceled) 
     
     
         17 . A lithographic process for making an integrated circuit, comprising:
 projecting, using ultraviolet light, a pattern of a mask onto a semiconductor wafer supporting a layer sensitive to the ultraviolet light, the projecting comprising:   imaging the pattern to a first intermediate image using a first objective part of a catadioptric projection objective, a first pupil surface being formed between the pattern and the first intermediate image;   imaging the first intermediate image to a second intermediate image using a second objective part of the catadioptric projection objective, the second objective part comprising two concave mirrors, the ultraviolet light illuminating a continuous area of a reflective surface of each of the two concave mirrors, and a second pupil surface being formed between the first intermediate image and the second intermediate image;   imaging the second intermediate image to a final image at the semiconductor wafer using a third objective part of the catadioptric projection objective, a third pupil surface being formed between the second intermediate image and the final image,   wherein both concave mirrors are arranged optically remote from the pupil surfaces.   
     
     
         18 . The process of  claim 17 , wherein the numerical aperture of the catadioptric projection objective at the semiconductor wafer is 1.05 or more and the ultraviolet light has a wavelength of 193 nm. 
     
     
         19 . The process of  claim 17 , wherein the pattern is imaged to the first intermediate image by focusing the ultraviolet light solely by refraction. 
     
     
         20 . The process of  claim 17 , wherein the first intermediate image is imaged to the second intermediate image by focusing the ultraviolet light solely by reflection. 
     
     
         21 . The process of  claim 20 , wherein the first intermediate image is imaged to the second intermediate image by focusing the ultraviolet light by both refraction and reflection. 
     
     
         22 . The process of  claim 17 , wherein the projecting further comprises providing liquid water in a path of the ultraviolet light between the catadioptric projection objective and the semiconductor wafer. 
     
     
         23 . The process of  claim 17 , wherein both concave mirrors are arranged optically remote from a pupil surface at a position where a chief ray height exceeds a marginal ray height of the imaging process. 
     
     
         24 . The process of  claim 17 , wherein the first, second, and third objective parts share a common straight optical axis. 
     
     
         25 . The process of  claim 17 , wherein at least one of the two concave mirrors is aspheric. 
     
     
         26 . The process of  claim 17 , wherein the third objective part comprises at least two negative lenses. 
     
     
         27 . The process of  claim 26 , wherein an aperture stop is located in the third objective part and the at least two negative lenses are positioned between the second intermediate image and the aperture stop. 
     
     
         28 . The process of  claim 17 , wherein the catadioptric projection objective comprises an optical axis and the pattern is projected from a field that does not intersect the optical axis. 
     
     
         29 . The process of  claim 28 , wherein the pattern is projected into a field at the semiconductor wafer that does not intersect the optical axis. 
     
     
         30 . The process of  claim 29 , wherein the field at the semiconductor wafer has a dimension of 5.5 mm or more. 
     
     
         31 . The process of  claim 30 , wherein the field at the semiconductor wafer has a size of 26 mm×5.5 mm. 
     
     
         32 . The process of  claim 17 , wherein the image at the semiconductor wafer is reduced in size relative to the pattern.