Projection objective and method for its manufacture

Abstract

A method of manufacturing a projection objective ( 22 ) of a microlithographic projection exposure apparatus ( 10 ). The projection objective ( 22 ) comprises at least one mirror (M 1 to M 6 ) that each have a mirror support ( 241 to 246 ) and a reflective coating ( 26 ) applied thereon. First imaging aberrations of a pre-assembled projection objective are measured. Before the coating ( 26 ) is applied, the mirror supports ( 241 to 246 ) are provided with a desired surface deformation ( 34 ). If the mirrors (M 1 to M 6 ) are not reflective for projection light without the coating ( 26 ), measuring light is used that has another wavelength. Alternatively, two identical mirror supports ( 246 ) may be provided. One support having a reflective coating is part of the pre-assembled projection objective whose imaging aberrations are measured. The other support is provided with surface deformations before coating and mounting the support into the objective.

1 . A projection objective for a microlithographic projection exposure apparatus, comprising at least one mirror that has
 a mirror support with a surface that has a local surface deformation for correcting at least one imaging aberration,   a reflective coating applied on the surface of the mirror support.   
   
   
       2 . The projection objective of  claim 1 , wherein the surface deformation is produced by local removal of material. 
   
   
       3 . A microlithographic projection exposure apparatus comprising:
 an illumination system for producing short-wave projection light; and   a projection objective comprising at least one mirror that has a mirror support with a surface that has a local surface deformation for correcting at least one imaging aberration and a reflective coating applied on the surface of the mirror support.   
   
   
       4 . The microlithographic projection exposure apparatus of  claim 3 , wherein the illumination system comprises a source for X-ray radiation. 
   
   
       5 . An optical system comprising at least one mirror, wherein the at least one mirror comprises:
 a mirror support including a surface having a local surface deformation for correcting at least one imaging aberration,   a reflective coating applied on the surface of the mirror support, wherein the optical system is contained in a microlithographic a projection exposure apparatus   
   
   
       6 . The optical system of  claim 5  wherein the surface deformation is produced by local removal of material. 
   
   
       7 . The optical system of  claim 5  wherein the reflective coating comprises a plurality of layers. 
   
   
       8 . The optical system of  claim 5  wherein the reflective coating is configured to reflect X-rays. 
   
   
       9 . The optical system of  claim 5  wherein the mirror support is, apart from the local surface deformation, rotationally symmetric. 
   
   
       10 . The optical system of  claim 5  wherein the maximum depth of the surface deformation is in a range from about several angstrom to a few nanometers. 
   
   
       11 . The optical system of  claim 5  wherein the surface deformation has a shape that is defined such that wavefront phase changes caused in the coating correct at least partly aberrations of the optical system. 
   
   
       12 . The optical system of  claim 5  wherein the coating applied on the surface comprises a recess having a form that substantially corresponds to the surface deformation. 
   
   
       13 . The optical system of  claim 5  wherein the optical system is an objective which is configured to image structures on a light sensitive layer. 
   
   
       14 . The optical system of  claim 5  wherein the objective comprises exclusively reflective mirrors as imaging elements. 
   
   
       15 . A microlithographic projection exposure apparatus comprising:
 an optical system comprising at least one mirror having a mirror support, the mirror support including a surface having a local surface deformation for correcting at least one imaging aberration; and   a reflective coating applied on the surface of the mirror support.   
   
   
       16 . The apparatus of  claim 15  further comprising an illumination system which is configured to produce X-ray radiation.