Catadioptric projection objective with adaptive mirror and projection exposure method

Abstract

A catadioptric projection objective for microlithography has at least one curved mirror that is deformable and adjusting elements that can deform the deformable mirror. The adjusting elements are mated to given image errors and their correction. The invention is suitable for astigmatism, fourfold wavefront-deformations due to lens heating, compaction, and the like.

1 - 35 . (canceled)  
   
   
       36 . A system, comprising: 
 a mirror having a curved mirror surface;    an apparatus comprising a plurality of actuators coupled to the mirror at eight discrete locations, the apparatus being configured so that during operation one or more of the actuators deform the mirror surface by applying a force to the mirror simultaneously at two or more of the discrete locations,    wherein the system is a microlithography projection objective.    
   
   
       37 . The system of  claim 36 , wherein each actuator is coupled to the mirror at two or four of the eight discrete locations.  
   
   
       38 . The system of  claim 36 , wherein each actuator is coupled to the mirror at a subset of the discrete locations and each actuator is configured to simultaneously apply a force to the mirror at each of the discrete locations at which it is coupled to the mirror.  
   
   
       39 . The system of  claim 36 , wherein the mirror surface has a symmetry axis and each actuator is coupled to the mirror at discrete locations that are symmetrically arranged with respect to the symmetry axis.  
   
   
       40 . The system of  claim 39 , wherein the symmetry axis corresponds to an optical axis of the microlithography projection objective.  
   
   
       41 . The system of  claim 36 , wherein the microlithography projection objective is a catadioptric projection objective.  
   
   
       42 . The system of  claim 36 , wherein the microlithography projection objective is a reduction objective.  
   
   
       43 . The system of  claim 36 , wherein the microlithography projection objective is configured to have a rectangular image field.  
   
   
       44 . The system of  claim 36 , wherein the apparatus is configured to deform the mirror to correct imaging errors of the microlithography projection objective.  
   
   
       45 . The system of  claim 44 , wherein the imaging errors comprise an astigmatism or a coma of the microlithography projection objective.  
   
   
       46 . The system of  claim 36 , wherein the force comprises an axial force.  
   
   
       47 . The system of  claim 36 , wherein the force comprises a moment.  
   
   
       48 . A system, comprising: 
 a mirror having a curved mirror surface having a symmetry axis;    an apparatus comprising a plurality of actuators each coupled to the mirror at two or more discrete locations, the apparatus being configured so that during operation one or more of the actuators deform the mirror surface by applying a force to the mirror at the corresponding discrete locations,    wherein the deformation is non-rotationally symmetric with respect to the symmetry axis and the system is a microlithography projection objective.    
   
   
       49 . The system of  claim 48 , wherein the apparatus is configured to deform the mirror to correct imaging errors of the microlithography projection objective, where the errors are not distributed rotationally symmetrically with respect to the symmetry axis of the mirror surface.  
   
   
       50 . The system of  claim 49 , wherein the imaging errors comprise an astigmatism or a coma of the microlithography projection objective.  
   
   
       51 . The system of  claim 48 , wherein the symmetry axis coincides with an optical axis of the microlithography projection objective.  
   
   
       52 . The system of  claim 48 , wherein the microlithography projection objective is configured to have a rectangular image field.  
   
   
       53 . The system of  claim 48 , wherein the force comprises an axial force.  
   
   
       54 . The system of  claim 48 , wherein the force comprises a moment.  
   
   
       55 . A system, comprising: 
 a microlithography projection objective an image plane, the microlithography projection objective comprising:    a mirror having a mirror surface;    a first adjusting element comprising an actuator coupled to the mirror at two discrete locations, the adjusting element being configured to that during operation the actuator deforms the mirror surface by applying a force simultaneously to the two discrete locations;    a sensor configured so that during operation of the system the sensor measures a parameter related to the imaging quality of the microlithography projection objective; and    a control unit in communication with the first adjusting element and the sensor, wherein during operation the control unit causes the first adjusting element to deform the mirror to correct imaging errors if of the microlithography projection objective based on measurements made by the sensor.    
   
   
       56 . The system of  claim 55 , wherein the sensor is positioned at the image plane.  
   
   
       57 . The system of  claim 55 , wherein the imaging errors comprise an astigmatism or a coma of the microlithography projection objective  
   
   
       58 . The system of  claim 55 , wherein the sensor is a wavefront sensor.  
   
   
       59 . The system of  claim 55 , wherein the sensor is an interferometer.  
   
   
       60 . The system of  claim 55 , wherein the sensor is configured to measure the parameter during exposure of a wafer by the system.  
   
   
       61 . The system of  claim 55 , wherein the sensor is configured to measure the parameter between exposures of different wafers by the system.  
   
   
       62 . The system of  claim 55 , wherein the microlithography projection objective comprises at least one other mirror.  
   
   
       63 . A system, comprising: 
 a mirror having a mirror surface; and    an adjusting element comprising a first actuator coupled to the mirror at a first location and a second location, the first location being different from the second locations and the adjusting element being configured so that during operation the first actuator deforms the mirror surface by applying a moment to the mirror in a direction non-parallel to the optical axis at the first and second locations,    wherein the system is a microlithography projection objective.    
   
   
       64 . A system, comprising: 
 a mirror having a mirror surface;    a first adjusting element comprising an actuator coupled to the mirror at a first location and a second location, the first location being different from the second locations and the adjusting element being configured so that during operation the actuator deforms the mirror surface by applying a moment to the mirror in a direction non-parallel to the optical axis at the first and second locations; and    a control unit in communication with the first adjusting element, wherein during operation the control unit causes the first adjusting element to deform the mirror to correct imaging errors of the microlithography projection objective,    wherein the system is a microlithography projection objective.