Projection lens and microlithographic projection exposure apparatus

Abstract

A projection exposure apparatus for microlithography has a light source, an illumination system, a mask-positioning system and a projection lens. The latter has a system aperture plane and an image plane and contains at least one lens that is made of a material which has a birefringence dependent on the transmission angle. The exposure apparatus further has an optical element, which has a position-dependent polarization-rotating effect or a position-dependent birefringence. This element, which is provided close to a pupil plane of the projection exposure apparatus, compensates at least partially for the birefringent effects produced in the image plane by the at least one lens.

1 . A projection exposure apparatus for microlithography comprising: 
 a) a light source;    b) an illumination system;    c) a mask-positioning system;    d) a projection lens having a system aperture plane and an image plane and comprising at least one lens made of a material which has a birefringence dependent on the transmission angle;    e) an object-positioning system;    d) an optical element, which 
 has a position-dependent polarization-rotating effect or a position-dependent birefringence,  
 compensates at least partially for the birefringent effects produced in the image plane by the at least one lens, and which  
 is provided close to a pupil plane of the projection exposure apparatus.  
   
   
   
       2 . The projection exposure apparatus according to  claim 1 , wherein the pupil plane is in the illumination system.  
   
   
       3 . The projection exposure apparatus according to  claim 1 , wherein the pupil plane is in the projection lens.  
   
   
       4 . The projection exposure apparatus according to  claim 1 , wherein projection light produced by the light source has a wavelength in the range from about 250 nm to about 100 nm.  
   
   
       5 . The projection exposure apparatus according to  claim 1 , wherein the projection lens has a numerical aperture on the image side in the range from 0.7 to 0.95.  
   
   
       6 . The projection exposure apparatus according to  claim 1 , wherein the optical element is arranged close to the image plane.  
   
   
       7 . The projection exposure apparatus according to  claim 1 , wherein the material of the at least one lens is a cubic fluoride crystal, in particular CaF 2 , BaF 2  or SrF 2 .  
   
   
       8 . The projection exposure apparatus according to  claim 1 , wherein the birefringence dependent on the transmission angle on the one hand and the position-dependent polarization-rotating effect or position-dependent birefringence on the other hand have the same manifold, in particular threefold or fourfold, rotational symmetry.  
   
   
       9 . The projection exposure apparatus according to  claim 1 , wherein the at least one lens is arranged between the system aperture plane and the image plane.  
   
   
       10 . The projection exposure apparatus according to  claim 4 , wherein the at least one lens is a final lens on an image side of the projection lens.  
   
   
       11 . The projection exposure apparatus according to  claim 1 , wherein the optical element is arranged close to a system aperture plane of the projection lens.  
   
   
       12 . The projection exposure apparatus according to  claim 1 , wherein the optical element is an optically active element, in particular made of quartz.  
   
   
       13 . The projection exposure apparatus according to  claim 1 , wherein the optical element is a birefringent element with locally varying thickness.  
   
   
       14 . The projection exposure apparatus according to  claim 1 , wherein tangential or radial polarization exists in the image plane.  
   
   
       15 . The projection exposure apparatus according to  claim 14 , wherein a polarization is produced in the illumination system or in a part of the projection lens on an object side, and wherein an optically active element is arranged close to a system aperture plane, said optically active element causing, by a suitable local thickness distribution, a polarization rotation to the tangential polarization with superimposed compensation for the birefringent effects produced by the at least one lens.  
   
   
       16 . A projection lens for a projection exposure apparatus, said projection lens comprising: 
 a) at least one first optical element that 
 is arranged close to a field plane and  
 causes a perturbation of a transmitted light beam, said perturbation depending on the polarization and the angle of light rays constituting the light beam;  
   b) at least one second optical element that 
 is arranged close to a pupil plane Fourier-transformed with respect to the field plane and  
 has an influence on the polarization of the light rays depending on their position at the at least one second optical element such that the perturbation caused by the at least one first optical element is compensated for at least partially.  
   
   
   
       17 . The projection lens according to  claim 16 , wherein the perturbation caused by the at least one first optical element and the influence on the polarization of the at least one second optical element have the same manifold, in particular threefold or fourfold, rotational symmetry.  
   
   
       18 . The projection lens according to  claim 16 , wherein the at least one first and the at least one second optical elements are rotated with respect to one another about a common symmetry axis so that the rotation-angle ranges of maximum birefringence for the at least one first and the at least one second elements are mutually offset.  
   
   
       19 . The projection lens according to  claim 16 , wherein the at least one second optical element influences the polarization of the light rays by stress-induced and position-dependent rotation of the polarization.  
   
   
       20 . The projection lens according to  claim 16 , wherein the at least one second optical element influences the polarization of the light rays by a stress-induced position-dependent birefringence.