Projection objective for a microlithographic projection exposure apparatus

Abstract

A projection objective of a microlithographic projection exposure apparatus contains a plurality of optical elements arranged in N>−2 successive sections A 1 to A N of the projection objective which are separated from one another by pupil planes or intermediate image planes. According to the invention, in order to correct a wavefront deformation, at least two optical elements each have an optically active surface locally reprocessed aspherically. A first optical element is in this case arranged in one section A j , j=1 . . . N and a second optical element is arranged in another section A k , k=1 . . . N, the magnitude difference |k−j| being an odd number.

1 .- 6 . (canceled) 
     
     
         7 . A catadioptric projection objective comprising:
 a plurality of optical elements arranged to, during operation, direct light from a first field plane to a second field plane to form a reduced image of a reticle positioned in the first field plane at the second field plane, there being at least one intermediate image at a corresponding field plane and at least two pupil planes in a path of the light between the first field plane and the second field plane, the plurality of optical elements comprising a first lens and a concave mirror, the first lens having at least one curved surface, a surface of the first lens comprising a first corrective structure; and   a pair of fold mirrors in the path of the light, a first of the fold mirrors being positioned in the path to direct the light towards the concave mirror and a second of the fold mirrors being positioned in the path to receive light reflected from the concave mirror,   wherein the first lens is positioned in the projection objective in the path between the pair of fold mirrors and the concave mirror, the first corrective structure reducing an imaging error of the projection objective at the second field plane relative to an initial arrangement of the projection objective that does not include the first corrective structure.   
     
     
         8 . The catadioptric projection objective of  claim 7 , wherein one of the intermediate images is downstream from the concave mirror in the light path. 
     
     
         9 . The catadioptric projection objective of  claim 7 , wherein the plurality of optical elements comprises a second lens comprising a surface having a second corrective structure that is in the path of the light. 
     
     
         10 . The catadioptric projection objective of  claim 9 , wherein the second lens is positioned in the path downstream from the pair of fold mirrors. 
     
     
         11 . The catadioptric projection objective of  claim 9 , wherein the first and second corrective structures are positioned relative to each other so their combined effect is to reduce one or more imaging errors of the projection objective at the second field plane relative to the initial arrangement. 
     
     
         12 . The catadioptric projection objective of  claim 9 , wherein the first and second corrective structures jointly correct even symmetry components of the field-dependency of the wavefront deformation in addition to odd components. 
     
     
         13 . The catadioptric projection objective of  claim 12 , wherein the plurality of optical elements comprises an additional optical element arranged in or close to one of the pupil planes, the additional optical element comprising a corrective structure at a surface in the path of the light. 
     
     
         14 . The catadioptric projection objective of  claim 13 , wherein the corrective structure at the surface of the additional optical element corrects a field-independent wavefront error during operation of the projection objective. 
     
     
         15 . The catadioptric projection objective of  claim 9 , wherein the plurality of optical elements comprises a third lens comprising a surface having a third corrective structure that is in the path of the light. 
     
     
         16 . The catadioptric projection objective of  claim 7 , wherein the first corrective structure is formed by reprocessing the lens surface. 
     
     
         17 . The catadioptric projection objective of  claim 16 , wherein the lens surface is reprocessed by erosion of a lens material at the lens surface. 
     
     
         18 . The catadioptric projection objective of  claim 17 , wherein a depth by which the lens material is eroded is less than 500 nm. 
     
     
         19 . The catadioptric projection objective of  claim 7 , wherein the imaging error is caused by a form error in one of the optical elements or a refractive index inhomogeneity of a lens material. 
     
     
         20 . The catadioptric projection objective of  claim 7 , wherein the plurality of optical elements comprises an additional optical element arranged in or close to one of the pupil planes, the additional optical element comprising a corrective structure at a surface in the path of the light. 
     
     
         21 . The catadioptric projection objective of  claim 17 , wherein the corrective structure at the surface of the additional optical element corrects a field-independent wavefront error during operation of the projection objective. 
     
     
         22 . The catadioptric projection objective of  claim 20 , wherein the corrective structure at the surface of the additional optical element corrects a field-independent wavefront error during operation of the projection objective. 
     
     
         23 . A microlithographic projection exposure apparatus, comprising:
 the catadioptric projection objective of claim  1 ; and   an illumination device, which during operation, generates light for illuminating the reticle positioned in the first field plane.