Catadioptric projection system for 157 nm lithography

Abstract

A photolithographic reduction projection catadioptric objective includes a first optical group G 1 including an even number of at least four mirrors M 1 -M 6; and a second at least substantially dioptric optical group G 2 imageward than the first optical group G 1 including a number of lenses E 4 -E 13. The first optical group G 1 provides compensative axial aberrative correction for the second optical group G 2 which forms an image with a numerical aperture of at least substantially 0.65, and preferably at least 0.70 or 0.75. Six mirror examples are shown.

What is claimed is:  
     
         1 . A photolithographic reduction projection catadioptric objective with a beam path, comprising: a first optical group (G 1 ) including an even number of at least four mirrors (M 1 -M 6 ); and a second at least substantially dioptric optical group (G 2 ) more imageward than said first optical group including a number of lenses (E 4 -E 13 ), and wherein said first optical group (G 1 ) provides compensative axial color correction for said second optical group (G 2 ).  
     
     
         2 . The objective of  claim 1 , wherein said image is formed with a numerical aperture of at least substantially 0.65 preferably 0.70 and more preferably 0.75 and more.  
     
     
         3 . The objective of  claim 1  or  2 , said first optical group producing an intermediate virtual image (VF).  
     
     
         4 . The objective of  claim 1 , wherein said at least four mirrors (M 1 -M 6 ) of said first optical group (G 1 ) include a convex mirror (M 6 ) arranged most imageward in the beam path of the objective, and wherein said second optical group (G 2 ) receives a beam from said convex mirror (M 6 ).  
     
     
         5 . The objective of  claim 1 , wherein optical surfaces of each mirror M 1 -M 6  of said objective are at least sections of surfaces of revolution each having a common axis (A) of symmetry.  
     
     
         6 . The objective of  claim 1 , wherein said second optical group is configured for independent compensative lateral aberrative correction.  
     
     
         7 . A photolithographic reduction projection catadioptric objective, comprising: a first optical group (G 1 ) including an even number of at least four mirrors (M 1 -M 6 ) for producing a virtual intermediate image (V 1 ); and a second at least substantially dioptric optical group (G 2 ) more imageward than said first optical group (G 1 ), said second optical group (G 2 ) including a number of lenses (E 4 -E 13 ) for receiving the virtual image (V 1 ) and providing image reduction, and wherein said first optical group (G 1 ) provides compensative axial color correction for said second optical group (G 2 ).  
     
     
         8 . The objective of  claim 7 , wherein said second optical group (G 2 ) is configured for independent compensative lateral color correction.  
     
     
         9 . A photolithographic reduction projection catadioptric objective, comprising: a first optical group (G 1 ) including an even number of at least four mirrors (M 1 -M 6 ) including a convex most imageward mirror (M 6 ), and a second at least substantially dioptric optical group (G 2 ) more imageward than said first optical group (G 1 ) receiving a beam from the convex most imageward mirror (M 6 ) of the first optical group (G 1 ), said second optical group (G 2 ) including a number of lenses (E 4 -E 13 ) providing image reduction, and wherein said first optical group (G 1 ) provides compensative axial color correction for said second optical group (G 2 ).  
     
     
         10 . The objective of  claim 9 , wherein said second optical group (G 2 ) is configured for independent compensative lateral color correction.  
     
     
         11 . A photolithographic reduction projection catadioptric objective, comprising: a first optical group (G 1 ) including an even number of at least six mirrors (M 1 -M 6 ); and a second at least substantially dioptric optical group more imageward than said first optical group (G 1 ) including a number of lenses (E 4 -E 13 ) for providing image reduction.  
     
     
         12 . The objective of  claim 11 , wherein said image is formed with a numerical aperture of at least substantially 0.65, preferably 0.70 and more preferably 0.75 or more.  
     
     
         13 . The objective of  claim 11  or  12 , said first optical group (G 1 ) producing an intermediate virtual image (VI).  
     
     
         14 . The objective of  claim 11 , wherein said at least six mirrors (M 1 -M 6 ) of said first optical group (G 1 ) include a convex most imageward mirror (M 6 ), and wherein said second optical group (G 2 ) receives a beam from said convex most imageward mirror (M 6 ).  
     
     
         15 . The objective of  claim 11 , wherein optical surfaces of each mirror of said objective are at least sections of surfaces of revolution each having a common axis of symmetry (A).  
     
     
         16 . The objective of  claim 11 , wherein said second optical group (G 2 ) is configured for independent compensative lateral color correction.  
     
     
         17 . The objective of  claim 11 , further comprising an unobscured system aperture (AS).  
     
     
         18 . The objective of  claim 17 , wherein said unobscured aperture AS is located within said second optical group (G 2 ).  
     
     
         19 . The objective of  claim 11 , further being devoid of any planar folding mirrors.  
     
     
         20 . The objective of  claim 11 , wherein an optical beam incident at said first optical group (G 1 ) is divergent after a most imageward mirror (M 6 ) of said first optical group (G 1 ).  
     
     
         21 . The objective of  claim 11 , which is further an unobscured system comprising parallel axes (A) of symmetry of curvatures of each optical element (M 1 -M 6 , E 1 -E 13 ) of said first (G 1 ) and second optical groups (G 2 ), and wherein no more than three (M 3 , M 4 , M 5 ) of said optical elements are cut to deviate in a substantially non-rotationally symmetric form.  
     
     
         22 . The objective of  claim 11 , comprising in sequence, in an optical direction from an object (Ob) side of said objective before said first optical group (G 1 ) to an image (Im) side of said objective after said second optical group (G 2 ), a first catadioptric sub group (E 1 -M 4 ) for producing a real intermediate image (IMI), a second sub group (M 5 , M 6 ) including catoptric components for producing a virtual image (V 1 ), and said second at least substantially dioptric group (G 2 ) for producing a real image.  
     
     
         23 . The objective of  claim 11 , comprising in sequence, in an optical direction from an object side of said objective before said first optical group (G 1 ) to an image (Im) side of said objective after said second optical group (G 2 ), a first field lens sub group (E 1 ), a second catadioptric sub group comprising one or more negative lenses (E 2 , E 3 ) and a concave mirror (M 2 ), generating axial chromatic aberration, a third sub group including an odd number of catoptric components (M 4 , M 5 , M 6 ), and a fourth positive lens group (G 2 ).  
     
     
         24 . The objective of  claim 11 , wherein said second optical group (G 2 ) comprises a plurality of lenses (E 4 -E 13 ), wherein a diameter of a beam incident upon each of said plurality of lenses is at least half of a diameter of said each lens (E 4 -E 13 ).  
     
     
         25 . The objective of  claim 11 , wherein said objective is doubly telecentric.  
     
     
         26 . The objective of  claim 11 , wherein optical paths of projected rays are redirected at each lens element (E 4 -E 13 ) of said second optical group at an angle of less than substantially  20 °.