Projection objective for immersion lithography

Abstract

In a projection objective provided for imaging a pattern arranged in an object plane of the projection objective into an image plane of the projection objective with the aid of an immersion medium arranged between a last optical element of the projection objective in the light path and the image plane, the last optical element has a transparent substrate and a protective layer system that is fitted to the substrate, is provided for contact with the immersion medium and serves for increasing the resistance of the last optical element to degradation caused by the immersion medium.

1 .- 69 . (canceled) 
   
   
       70 . An optical element usable for a projection optical system which exposes a substrate by projecting a predetermined pattern onto the substrate, the optical element comprising:
 a base of the optical element which is installed to an end of the projection optical system on a side of the substrate and through which the exposure is performed in a state that a liquid is maintained between the optical element and the substrate; and   a corrosion resistant film which is formed on at least a part of a surface of the base of the optical element to avoid corrosion of the base by the liquid.   
   
   
       71 . The optical element according to  claim 70 , wherein the corrosion resistant film is an oxide film. 
   
   
       72 . The optical element according to  claim 71 , wherein the oxide film is at least one of a silicon oxide film and an aluminum oxide film. 
   
   
       73 . The optical element according to  claim 70 , wherein the base of the optical element is fluorite. 
   
   
       74 . The optical element according to  claim 70 , wherein a light beam, which is used for the exposure, is an ArF laser beam. 
   
   
       75 . The optical element according to  claim 70 , wherein the liquid is pure water. 
   
   
       76 . An exposure apparatus which exposes a substrate by projecting an image of a predetermined pattern onto the substrate through a liquid, the exposure apparatus comprising:
 a projection optical system which projects the image of the pattern onto the substrate;   an optical element which is installed to an end of the projection optical system on a side of the substrate; and   an apparatus which supplies the liquid to a space between the optical element and the substrate, wherein:   the optical element includes a base, and a corrosion resistant film which is formed on at least a part of a surface of the base in order to avoid corrosion of the base.   
   
   
       77 . The exposure apparatus according to  claim 76 , wherein the corrosion resistant film is an oxide film. 
   
   
       78 . The exposure apparatus according to  claim 77 , wherein the corrosion resistant film is a multilayer oxide film. 
   
   
       79 . The exposure apparatus according to  claim 77 , wherein the oxide film is at least one of a silicon oxide film and an aluminum oxide film. 
   
   
       80 . The exposure apparatus according to  claim 76 , wherein the base of the optical element is fluorite. 
   
   
       81 . The exposure apparatus according to  claim 80 , wherein a light beam, which is used for the exposure, is an ArF laser beam. 
   
   
       82 . The exposure apparatus according to  claim 76 , wherein the liquid is pure water. 
   
   
       83 . An optical element used for a liquid immersion exposure apparatus which exposes a substrate with an exposure beam via the optical element and a liquid, the optical element comprising:
 a base; and   a member which prevents the base from contacting with the liquid to avoid corrosion of the base by the liquid,   wherein the optical element makes contact with the liquid when the substrate is exposed with the exposure beam via the optical element and the liquid.   
   
   
       84 . The optical element according to  claim 83 , wherein the member includes a corrosion resistant film. 
   
   
       85 . The optical element according to  claim 84 , wherein the corrosion resistant film includes a multi-layer film. 
   
   
       86 . The optical element according to  claim 84 , wherein the corrosion resistant film includes an oxide coating layer. 
   
   
       87 . The optical element according to  claim 86 , wherein the oxide coating layer has a corrosion resistance. 
   
   
       88 . The optical element according to  claim 85 , wherein the multi-layer film has at least one layer which has a corrosion resistance. 
   
   
       89 . The optical element according to  claim 85 , wherein an outermost layer of the multi-layer film has a corrosion resistance. 
   
   
       90 . The optical element according to  claim 85 , wherein each of layers included in the multi-layer film has a corrosion resistance. 
   
   
       91 . The optical element according to  claim 84 , wherein the corrosion resistant film has a thickness of 50 to 2000 angstrom. 
   
   
       92 . The optical element according to  claim 85 , wherein the multi-layer film has an antireflection function as a whole. 
   
   
       93 . The optical element according to  claim 86 , wherein the oxide coating layer has a corrosion resistance against pure water. 
   
   
       94 . The optical element according to  claim 86 , wherein the oxide coating layer is made of silicon oxide. 
   
   
       95 . The optical element according to  claim 83 , wherein the exposure beam passes through the member. 
   
   
       96 . The optical element according to  claim 95 , wherein the exposure beam passes through a light-outgoing surface of the optical element. 
   
   
       97 . The optical element according to  claim 96 , wherein the exposure beam passed through the base is incident on the member, and the exposure beam passed through the member is incident on the liquid. 
   
   
       98 . The optical element according to  claim 83 , wherein the member is provided on a liquid side with respect to the base. 
   
   
       99 . The optical element according to  claim 98 , wherein the member makes contact with the liquid. 
   
   
       100 . The optical element according to  claim 98 , wherein the member is provided on the base. 
   
   
       101 . The optical element according to  claim 83 , wherein the member makes contact with the liquid. 
   
   
       102 . The optical element according to  claim 101 , wherein the exposure beam passes through the member. 
   
   
       103 . The optical element according to  claim 101 , wherein the exposure beam passes through a light-outgoing surface of the optical element. 
   
   
       104 . The optical element according to  claim 83 , wherein the member is provided on the base. 
   
   
       105 . The optical element according to  claim 83 , wherein the member is provided on a surface of the base which contacts with the liquid. 
   
   
       106 . The optical element according to  claim 83 , wherein the base is a plate-shaped base. 
   
   
       107 . An optical system used for a liquid immersion exposure apparatus, comprising the optical element as defined in  claim 83 . 
   
   
       108 . A liquid immersion exposure apparatus comprising an optical element as defined in  claim 83 . 
   
   
       109 . A liquid immersion exposure apparatus which exposes a substrate with an exposure beam through a liquid, the apparatus comprising:
 an optical element including a base; and a member which prevents the base from contacting with the liquid to avoid corrosion of the base by the liquid,   wherein the optical element contacts with the liquid when the substrate is exposed with the exposure beam via the optical element and the liquid.   
   
   
       110 . The liquid immersion exposure apparatus according to  claim 109 , further comprising a liquid supply member having a liquid supply outlet for supplying the liquid, wherein the substrate is moved relative to the liquid supply member. 
   
   
       111 . The liquid immersion exposure apparatus according to  claim 109 , wherein the member includes a corrosion resistant film. 
   
   
       112 . The liquid immersion exposure apparatus according to  claim 111 , wherein the corrosion resistant film includes a multi-layer film. 
   
   
       113 . The liquid immersion exposure apparatus according to  claim 111 , wherein the corrosion resistant film includes an oxide coating layer. 
   
   
       114 . The liquid immersion exposure apparatus according to  claim 112 , wherein the multi-layer film has at least one layer which has a corrosion resistance. 
   
   
       115 . The liquid immersion exposure apparatus according to  claim 112 , wherein an outermost layer of the multi-layer film has a corrosion resistance. 
   
   
       116 . The liquid immersion exposure apparatus according to  claim 112 , wherein the multi-layer film has at least one oxide layer which has a corrosion resistance. 
   
   
       117 . The liquid immersion exposure apparatus according to  claim 109 , wherein the beam passed through the base is incident on the member, and the beam passed through the member is incident on the liquid. 
   
   
       118 . The liquid immersion exposure apparatus according to  claim 109 , wherein the member is provided on a liquid side with respect to the base and makes contact with the liquid. 
   
   
       119 . The liquid immersion exposure apparatus according to  claim 109 , wherein the member makes contact with the liquid. 
   
   
       120 . The liquid immersion exposure apparatus according to  claim 119 , wherein the exposure beam passes through a light-outgoing surface of the optical element. 
   
   
       121 . The liquid immersion exposure apparatus according to  claim 109 , wherein the member is provided on the base. 
   
   
       122 . A method for producing an optical element used for a liquid immersion exposure apparatus, comprising:
 providing a base; and   providing a member on a surface of the base, the member prevents any portion of the base from contacting with the liquid.   
   
   
       123 . The method according to  claim 122 , wherein the member is formed by film forming method which is one of a sputtering method, an ion beam assist method, an ion plating method and a heating vapor deposition method. 
   
   
       124 . A method for producing an optical element used for a liquid immersion exposure apparatus, comprising:
 providing a plate-shaped base; and   providing a member on a surface of the base where the optical element makes contact with the liquid to prevent any portion of the base from contacting with the liquid.   
   
   
       125 . A method for producing a liquid immersion exposure apparatus which exposes a substrate with an exposure beam through a liquid, comprising:
 providing an optical element including a base and a member which is provided on a surface of the base and which prevents any portion of the base from contacting with the liquid; and   providing a projection optical system in which the optical element is installed.