Method and apparatus for illuminating a surface using a projection imaging apparatus

Abstract

A method and illumination optical system forms a modified illumination configuration on an optical integrator so that a secondary light source having a desired modified illumination configuration is formed and light loss is minimized. A light beam shape changing element that diffuses illumination in a plurality of directions, and an angular light beam forming element that forms a plurality of light source images operate together to create a modified illumination configuration on the optical integrator. Since the secondary light source has a desired modified illumination configuration, an aperture stop used to restrict the size and/or shape of the secondary light source blocks only a small amount of illumination, or can be eliminated altogether. It is possible to alter the annular ratio and outer diameter of an annular or quadrupole modified illumination configuration by changing the magnification of a zoom optical system positioned between the light beam shape changing element and the angular light beam forming element. Furthermore, by changing the focal length of a zoom optical system (which is positioned upstream of the optical integrator), it is possible to change the outer diameter of the annular or quadrupole secondary light source without changing the annular ratio thereof.

What is claimed is:  
     
         1 . An illumination system for illuminating a surface by use of light from a light source, and for defining an intensity distribution of a projection beam at a plane, the illumination system comprising: 
 an adjustor, arranged in an optical path of the illumination system, for controlling an inner and/or outer radial extent of the intensity distribution,    wherein the adjustor comprises at least one exchanger for inserting and removing at least one of a plurality of optical elements into and out of a projection beam path, each of the optical elements defining at least one parameter of the intensity distribution.    
     
     
         2 . A system according to  claim 1 , wherein at least one optical element comprises diffractive and/or refractive elements.  
     
     
         3 . A system according to  claim 2 , wherein at least one optical element comprises an array of refractive or diffractive microlenses or microprisms.  
     
     
         4 . A system according to  claim 3 , wherein at least two of the optical elements are arranged in parallel in the beam path.  
     
     
         5 . A system according to  claim 1 , wherein at least two of the optical elements are arranged in parallel in the beam path.  
     
     
         6 . A system according to  claim 5 , wherein at least two of the optical elements are arranged in series along the beam path.  
     
     
         7 . A system according to  claim 1 , wherein at least two of the optical elements are arranged in series along the beam path.  
     
     
         8 . A system according to  claim 1 , wherein the parameters of the intensity distribution are selected from: an outer radial extent, an annularity, an inner radial extent, a perimetric form, a perimetric orientation, a number of poles, an orientation of poles, a pole size and a pole shape, intensity gradient.  
     
     
         9 . A system according to  claim 1 , wherein the adjustor produces from a substantially collimated radiation beam an intensity distribution with a desired outer and/or inner radial extent.  
     
     
         10 . A system according to  claim 9 , further comprising an optical integrator serving to improve the cross-sectional intensity uniformity of the beam, and a focusing optical system for focusing the beam onto an entrance surface of the optical integrator.  
     
     
         11 . An illumination system that successively comprises: 
 an adjustor, for producing from a substantially collimated radiation beam an intensity distribution with a desired outer and/or inner radial extent; and    a focusing optical system, for focusing the beam onto an entrance surface of an integrator means, the integrator means serving to improve the cross-sectional intensity uniformity of the beam,    wherein the adjustor does not comprise an axicon.    
     
     
         12 . An illumination system that successively comprises: 
 an adjustor, for producing from a substantially collimated radiation beam an intensity distribution with a desired outer and/or inner radial extent; and    a focusing optical system, for focusing the beam onto an entrance surface of an integrator means, the integrator means serving to improve the cross- sectional intensity uniformity of the beam,    wherein the adjustor comprises a holding means for arranging at least two optical elements in parallel in the beam.    
     
     
         13 . An illumination system that successively comprises: 
 an adjustor, for producing from a substantially collimated radiation beam an intensity distribution with a desired outer and/or inner radial extent; and    a focusing optical system, for focusing the beam onto an entrance surface of an integrator means, the integrator means serving to improve the cross-sectional intensity uniformity of the beam,    wherein the adjustor comprises a holder that can be provided with a single optical element, the optical element comprising an array of refractive or diffractive microlenses or microprisms.    
     
     
         14 . An illumination system for illuminating a surface by use of light from a light source, and for defining the intensity distribution of the projection beam at a plane, the illumination system comprising: 
 an adjustor, arranged in an optical path of the illumination system, for controlling an inner and/or outer radial extent of the intensity distribution,    wherein the adjustor comprises at least one exchanger for inserting and removing at least one of a plurality of optical elements into and out of a projection beam path, each of the optical elements defining at least one parameter of a intensity distribution; and    wherein the at least one parameter of the intensity distribution comprising at least one of an outer radial extent, an annularity, an inner radial extent, a perimetric form, a perimetric orientation, a number of poles, an orientation of poles and a pole size.    
     
     
         15 . A lithographic projection apparatus comprising: 
 the illumination system according to  claim 1;  and    a projection system for imaging a pattern onto a target portion of a substrate.    
     
     
         16 . A lithographic projection apparatus comprising: 
 the illumination system according to  claim 11;  and    a projection system for imaging a pattern onto a target portion of a substrate.    
     
     
         17 . A lithographic projection apparatus comprising: 
 the illumination system according to  claim 12;  and    a projection system for imaging a pattern onto a target portion of a substrate.    
     
     
         18 . A lithographic projection apparatus comprising: 
 the illumination system according to  claim 13;  and    a projection system for imaging a pattern onto a target portion of a substrate.    
     
     
         19 . A lithographic projection apparatus comprising: 
 the illumination system according to  claim 14;  and    a projection system for imaging a pattern onto a target portion of a substrate.    
     
     
         20 . A lithographic method comprising: 
 illuminating a pattern with the illumination system according to  claim 1;  and    projecting the illuminated pattern onto a target portion of a substrate.    
     
     
         21 . A lithographic method comprising: 
 illuminating a pattern with the illumination system according to  claim 11;  and    projecting the illuminated pattern onto a target portion of a substrate.    
     
     
         22 . A lithographic method comprising: 
 illuminating a pattern with the illumination system according to  claim 12;  and    projecting the illuminated pattern onto a target portion of a substrate.    
     
     
         23 . A lithographic method comprising: 
 illuminating a pattern with the illumination system according to  claim 13;  and    projecting the illuminated pattern onto a target portion of a substrate.    
     
     
         24 . A lithographic method comprising: 
 illuminating a pattern with the illumination system according to  claim 14;  and    projecting the illuminated pattern onto a target portion of a substrate.