Illumination optical apparatus and exposure apparatus

Abstract

An illumination optical apparatus ( 14 - 40 ) and exposure apparatus ( 10 ) provided with the illumination apparatus, capable of employing a high-output light source. The illumination apparatus comprises, in order along an optical axis, a light source ( 14 ) capable of providing a primary light beam (B) having a cross-section, a condenser optical system ( 30 ) to condense the primary light beam so as to form a convergence point (F) adjacent the condenser optical system, a light-pipe optical integrator ( 160 ) having a rectangular cross-sectional shape with a first side of length dx, a second side of length dy, and a most light-source-wise incident surface ( 160 a ) axially spaced from the convergence point by a spacing (L2). The integrator is capable of forming a plurality of secondary light sources and corresponding secondary light beams (B′) from the primary light beam. Adjacent the integrator is an imaging optical system ( 40 ) to converge the primary and secondary light beams to illuminate the illumination surface. The apparatus preferably satisfies the following conditions: 0.1≦ L 2≦ dx /(2×tan α x ) 0.1≦ L 2≦ dy /(2×tan α y ), wherein αx is the divergence angle of the primary light beam when incident the integrator incident surface, as measured in a first plane that includes the optical axis. Likewise, αy is the corresponding angle as measured in a second plane orthogonal to the first plane. These conditions ensure that the integrator will not be damaged or otherwise broken by high concentrations of light on the integrator incident surface. The exposure apparatus comprises the above-described illumination optical system and further includes a projection optical system ( 54 ) arranged adjacent the illumination surface so as to project an image of a pattern on a mask ( 48 ) onto a photosensitive substrate ( 60 ), thereby patterning the substrate.

What is claimed is:  
     
         1 . An illumination optical apparatus for illuminating an illumination surface, comprising, in order along an optical axis: 
 a) a light source capable of providing a primary light beam having a cross-section;    b) a condenser optical system to condense said primary light beam so as to form a convergence point adjacent said condenser optical system;    c) a light-pipe optical integrator having a rectangular cross-sectional shape with a first side of length dx, a second side of length dy, and a most light-source-wise incident surface axially spaced from said convergence point by a spacing L, said integrator capable of forming a plurality of secondary light sources and corresponding secondary light beams from said primary light beam;    d) an imaging optical system to converge said primary and secondary light beams to illuminate the illumination surface; and    e) wherein the following conditions are satisfied:    0.1≦ L≦dx /(2×tan α x ) 0.1≦ L≦dy /(2×tan α y ),     wherein αx is an angle of said primary light beam incident said incident surface, as measured in a first plane that includes the optical axis, and αy is an angle of said primary light beam incident said incident surface, as measured in a second plane orthogonal to said first plane.    
     
     
         2 . An illumination optical apparatus according to  claim 1 , further including first and second variable optical members, arranged between said light source and said light pipe optical integrator, capable of shaping said primary light beam cross-section so as to make said light beam cross-section and said light pipe optical integrator cross-sectional shape substantially similar.  
     
     
         3 . An illumination optical apparatus according to  claim 2 , wherein said condenser optical system has a variable focal length to allow a change in said at least one of angles αx and αy while maintaining said convergence point at a fixed position.  
     
     
         4 . An illumination optical apparatus according to  claim 1 , further including first and second variable optical members capable of shaping said light beam cross-section.  
     
     
         5 . An illumination optical apparatus according to  claim 4 , wherein said first and second variable optical members are capable of being arranged so as to shape said light beam cross-section to form an annular light source.  
     
     
         6 . An illumination optical apparatus according to  claim 4 , wherein said first and second variable optical members are capable of being arranged so as to shape said light beam cross-section to form a plurality of light sources eccentric to the optical axis.  
     
     
         7 . An illumination optical apparatus according to  claim 4 , wherein said first variable optical member comprises, in order along the optical axis: 
 a) a first conical prism with a most light-source-wise planar surface and an opposing conical concave surface symmetric with respect to the optical axis;    b) a second conical prism with a most light-source-wise conical convex surface symmetric with respect to the optical axis, and an opposing planar surface; and    c) wherein at least one of said first conical prism and said second conical prism is designed so as to be moveable along the optical axis.    
     
     
         8 . An illumination optical apparatus according to  claim 7 , wherein said second variable optical member comprises, in order along the optical axis: 
 a) a first pyramidal prism with a most light-source-wise planar surface and an opposing pyramidal concave surface symmetric with respect to the optical axis;    b) a second pyramidal prism with a most light-source-wise pyramidal convex surface symmetric with respect to the optical axis, and an opposing planar surface; and    c) wherein at least one of said first pyramidal prism and said second pyramidal prism is designed so as to be moveable along the optical axis.    
     
     
         9 . An illumination optical apparatus, comprising in order along an optical axis: 
 a) a light source capable of supplying a primary light beam having a first cross-section;    b) a condenser optical system capable of condensing said light beam;    c) a light pipe optical integrator having a most light-source-wise incident surface with an incident surface shape, and capable of forming, from said primary light beam, a plurality of secondary light sources and associated secondary light beams;    d) an imaging optical system designed to converge said secondary light beams to illuminate the surface to be irradiated; and    e) a light beam shaping apparatus designed to shape said light beam first cross-section to form a second light-beam cross-section having a shape substantially similar to said light pipe incident surface shape.    
     
     
         10 . An illumination optical apparatus according to  claim 9 , wherein said condenser optical system is capable of forming a convergence point spaced apart from said light pipe incident surface by spacing L.  
     
     
         11 . An illumination optical apparatus according to  claim 10 , wherein said spacing L satisfied the conditions:  
       0.1≦ L≦dx /(2×tan α x ) 0.1≦ L≦dy /(2×tan α y ),  
       wherein αx is an angle in said primary light beam incident said incident surface, as measured in a first plane that includes the optical axis, and αy is an angle in said incident light beam incident said incident surface, as measured in a second plane orthogonal to said first plane.  
     
     
         12 . An exposure apparatus for patterning a photosensitive substrate with pattern present on a mask, comprising in order along an optical axis: 
 a) an illumination optical system as set forth in  claim 1;  and    b) a projection optical system arranged adjacent the illumination surface, with the mask arranged at the illumination surface, so as to project the mask pattern onto the photosensitive substrate.    
     
     
         13 . An exposure apparatus for exposing a pattern present on a mask onto a photosensitive substrate, comprising in order along an optical axis: 
 a) an illumination optical system as set forth in  claim 9;  and    b) a projection optical system arranged adjacent the illumination surface, with the mask arranged at the illumination surface, so as to project the mask pattern onto the photosensitive substrate.    
     
     
         14 . A method of uniformly illuminating a surface with an illumination optical apparatus having a light pipe optical integrator with an integrator cross-section, an incident surface and an exit surface, comprising the steps of: 
 a) providing a primary light beam having a primary light beam cross-section;    b) condensing said primary light beam and forming a convergence point at a position spaced apart from said incident surface;    c) collecting light emanating from said convergence point at an angle α using said light pipe optical integrator;    d) forming a plurality of secondary light sources and associated secondary light beams by multiply internally reflecting said light within said light pipe optical integrator; and    e) converging said primary and secondary light beams emanating from said exit surface to uniformly illuminate the illumination surface.    
     
     
         15 . A method according to  claim 14 , wherein said condensing step b) further includes the step of varying said angle α while maintaining said convergence point at a fixed position.  
     
     
         16 . A method according to  claim 14 , further including the step after said step a) but before said step b), of varying said primary light beam cross-section to be substantially similar in size and shape to said integrator cross-section.  
     
     
         17 . A method of patterning a photosensitive substrate by uniformly illuminating a mask having a pattern thereon with an exposure apparatus including a light pipe optical integrator having an integrator cross-section, an incident surface and an exit surface, comprising the steps of: 
 a) providing a primary light beam having a primary light beam cross-section;    b) condensing said primary light beam and forming a convergence point at a position spaced apart from said incident surface;    c) collecting light emanating from said convergence point at an angle α using said light pipe optical integrator;    d) forming a plurality of secondary light sources and associated secondary light beams by multiply internally reflecting said light within said light pipe optical integrator;    e) converging said primary and secondary light beams emanating from said exit surface to uniformly illuminate the mask; and    f) projecting an image of the mask onto the photosensitive substrate so as to form a pattern thereon.    
     
     
         18 . A method according to  claim 17 , wherein said condensing step b) further includes the step of varying said angle α while maintaining said convergence point at a fixed position.  
     
     
         19 . A method according to  claim 17 , further including the step after said step a) but before said step b), of varying said primary light beam cross-section to be substantially similar in size and shape to said integrator cross-section.