Projection exposure system for microlithography and method of monitoring a lateral imaging stability

Abstract

A projection exposure system ( 10 ) for microlithography includes projection optics ( 12 ) configured to image mask structures into a substrate plane ( 16 ), an input diffraction element ( 28 ) configured to convert irradiated measurement radiation ( 21 ) into at least two test waves ( 30 ) directed onto the projection optics ( 12 ) with differing propagation directions, a detection diffraction element ( 34; 28 ) disposed in the optical path of the test waves ( 30 ) after they have passed through the projection optics ( 12 ) and configured to produce a detection beam ( 36 ) from the test waves ( 30 ) which has a mixture of radiation portions of both test waves ( 30 ), a photo detector ( 38 ) disposed in the optical path of the detection beam ( 36 ) configured to record the radiation intensity of the detection beam ( 36 ), time resolved, and an evaluation unit configured to determine the lateral imaging stability of the projection optics ( 12 ) from the radiation intensity recorded.

1 .- 17 . (canceled) 
     
     
         18 . A projection exposure system for microlithography comprising:
 projection optics configured to image mask structures into a substrate plane,   a detection diffraction element, disposed in an optical path of at least two different test waves having passed through the projection optics and configured to produce a first detection beam and a second detection beam from the test waves, which first detection beam comprises a mixture of radiation portions of the at least two test waves and which second detection beam comprises at least one radiation portion of a first of the two test waves, and   an evaluation unit configured to determine a lateral imaging stability of the projection optics from radiation intensities of the detection beams.   
     
     
         19 . The projection exposure system according to  claim 18 ,
 wherein the detection diffraction element is further configured to produce a third detection beam from the test waves, which third detection beam comprises at least one radiation portion of the second of the two test waves.   
     
     
         20 . The projection exposure system according to  claim 18 ,
 further comprising an input diffraction element configured to convert irradiated measurement radiation into the at least two different test waves, which test waves are directed onto the projection optics with different propagation directions.   
     
     
         21 . The projection exposure system according to  claim 18 ,
 further comprising photo detectors, disposed and configured to record a time-resolved radiation intensity of each of the detection beams, wherein the lateral imaging stability is determined from the recorded intensities.   
     
     
         22 . The projection exposure system according to  claim 18 ,
 wherein the evaluation unit is configured to determine the lateral imaging stability of the projection optics from the time resolved radiation intensity recorded at a temporal resolution of at least 10 Hz.   
     
     
         23 . The projection exposure system according to  claim 18 ,
 wherein the at least two test waves are spatially separate from each other in at least one plane of the projection optics.   
     
     
         24 . The projection exposure system according to  claim 20 ,
 wherein the input diffraction element is disposed on a mask side of the projection optics and the detection diffraction element on a substrate side of the projection optics.   
     
     
         25 . The projection exposure system according to  claim 20 ,
 further comprising an illumination diffraction element disposed in the optical path of the measurement radiation upstream of the input diffraction element and is configured to convert the measurement radiation into at least two measurement radiation partial beams with differing propagation directions.   
     
     
         26 . The projection exposure system according to  claim 25 ,
 further comprising an imaging optical element, disposed between the illumination diffraction element and the input diffraction element, and configured to direct the measurement radiation partial beams onto the input diffraction element.   
     
     
         27 . The projection exposure system according to  claim 25 ,
 wherein the illumination diffraction element and the input diffraction element are configured to convert each of the at least two measurement radiation partial beams from the illumination diffraction element into at least two diffraction individual beams by diffraction on the input diffraction element, and wherein at least one of the diffraction individual beams is produced by diffracting a first of the measurement radiation partial beams overlaid by one of the diffraction individual beams produced by diffracting a second of the measurement radiation partial beams such that the overlaid diffraction individual beams together form one of the test waves.   
     
     
         28 . The projection exposure system according to  claim 18 ,
 further comprising an exposure radiation source configured to produce radiation for imaging the mask structures into the substrate plane, and a measurement radiation source independent of the exposure radiation source configured to produce measurement radiation for generating the test waves.   
     
     
         29 . The projection exposure system according to any of  claim 18 ,
 wherein the test waves comprise measurement radiation and the projection exposure system further comprises: an exposure optical path arranged to image the mask structures into the substrate plane, and a coupling mirror arranged to couple, on the mask side, the measurement radiation into the exposure optical path.   
     
     
         30 . The projection exposure system according to  claim 18 ,
 further comprising: an exposure optical path arranged to image the mask structures into the substrate plane, and an uncoupling mirror arranged to uncouple the test waves from the exposure optical path.   
     
     
         31 . The projection exposure system according to  claim 20 ,
 wherein the input diffraction element and the detection diffraction element are formed by a single diffraction element, and the projection exposure system further comprises a retro-reflector configured to reflect the test waves back on themselves after the test waves pass through the projection optics, such that the test waves take a second pass through the projection optics and thereafter strike the detection diffraction element.   
     
     
         32 . The projection exposure system according to  claim 18 ,
 wherein the test waves comprise measurement radiation and the projection optics consist essentially of mirrors, and wherein individual regions of the surfaces of the mirrors are provided with respective reflective coatings selected in accordance with a wavelength of the measurement radiation.   
     
     
         33 . The projection exposure system according to  claim 18 ,
 wherein the projection optics are configured to image the mask structures with light in at least the extreme-ultraviolet frequency wavelength range into the substrate plane.   
     
     
         34 . A method for monitoring a lateral imaging stability of projection optics of a projection exposure system for microlithography, comprising:
 generating at least two different test waves and passing the test waves through the projection optics,   causing the test waves, after passing through the projection optics, to strike a detection diffraction element, and producing, by diffraction, a first detection beam and a second detection beam, which first detection beam comprises a mixture of radiation portions of the at least two test waves and which second detection beam comprises at least one radiation portion of a first of the two test waves, and   recording radiation intensities of the detection beams and, from said recording, establishing a lateral imaging stability of the projection optics.