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, the illumination system comprising: 
 an emission angle conserving optical unit effective to emit the light from the light source at a constant divergent angle; and    a diffractive optical element for producing a desired light intensity distribution on a predetermined plane,    wherein the diffractive optical element is disposed at or adjacent to a position where light from the emission angle conserving optical unit is collected.    
     
     
         2 . The illumination system according to  claim 1 , further comprising a multiple-beam producing element, and a light projecting element for superposing light beams from the multiple-beam producing element one upon another on the surface to be illuminated, wherein the predetermined plane corresponds to a light entrance surface of the multiple-beam producing element.  
     
     
         3 . The illumination system according to  claim 2 , further comprising a zoom optical system for projecting the light intensity distribution, produced by the diffractive optical element, upon the light entrance surface of the multiple-beam producing element at a predetermined magnification.  
     
     
         4 . The illumination system according to  claim 3 , wherein a plurality of emission angle conserving optical units of different divergent angles are provided, and wherein the emission angle conserving optical units are interchangeably set at a light path in accordance with a change in magnification of the zoom optical system.  
     
     
         5 . The illumination system according to  claim 1 , wherein a plurality of diffractive optical elements for producing different light intensity distributions on the predetermined plane are provided, wherein the diffractive optical elements are interchangeably set at a light path to produce a desired light intensity distribution on the predetermined plane.  
     
     
         6 . The illumination system according to  claim 1 , wherein the diffractive optical element is a phase type.  
     
     
         7 . The illumination system according to  claim 1 , wherein the emission angle conserving optical unit comprises a flys eye lens having small lenses arrayed two-dimensionally.  
     
     
         8 . An exposure apparatus, comprising: 
 an illumination optical system for illuminating a mask surface, as a surface to be illuminated, with use of light from a light source, the illumination optical system including (i) an emission angle conserving optical unit effective to emit the light from the light source at a constant divergent angle, and (ii) a diffractive optical element for producing a desired light intensity distribution on a predetermined plane, wherein the diffractive optical element is disposed at or adjacent to a position where light from the emission angle conserving optical unit is collected; and    a projection optical system for projecting a pattern formed on the mask surface, as illuminated with the light from the illumination optical system, onto a wafer.    
     
     
         9 . A device manufacturing method, comprising the steps of: 
 applying a photosensitive material to a wafer;    illuminating a mask surface, as a surface to be illuminated, with use of light from an illumination optical system, wherein the illumination optical system includes (i) an emission angle conserving optical unit effective to emit the light from the light source at a constant divergent angle, and (ii) a diffractive optical element for producing a desired light intensity distribution on a predetermined plane,    wherein the diffractive optical element is disposed at or adjacent to a position where light from the emission angle conserving optical unit is collected;    projecting, through a projection optical system, a pattern formed on the mask surface onto a wafer; and    developing the transferred pattern.    
     
     
         10 . An illumination system for illuminating a surface by use of light from a light source, the illumination system comprising: 
 an optical integrator which is arranged in a light path of the illumination system;    an illumination pupil having a light intensity distribution such that a lower light intensity is formed at a position near an optical axis relative to positions away from the optical axis;    an annular ratio changer which is arranged in an optical path between the light source and the optical integrator and which changes the annular ratio of the light intensity distribution; and    an outer diameter changer which is arranged in an optical path between the light source and the optical integrator and which changes the outer diameter of the light intensity distribution.    
     
     
         11 . The system according to  claim 10 , wherein the light intensity distribution comprises a multipole shape.  
     
     
         12 . The system according to  claim 11 , further comprising an optical element which is arranged in an optical path between the light source and the changers and which converts the light from the light source to a divergence light beam.  
     
     
         13 . The system according to  claim 12 , wherein the optical element has at least one of a diffractive and a refractive optical element.  
     
     
         14 . The system according to  claim 12 , further comprising another optical element which is interchangeable with the optical element and which converts the light from the light source to a divergence light beam different from the divergence light beam created by the optical element.  
     
     
         15 . An exposure 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 . An exposure 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.    
     
     
         17 . A method of transferring a pattern on an original onto a work, comprising the steps of: 
 preparing said original;    preparing said work;    illuminating said original with the illumination optical system of  claim 1;  and    transferring said pattern onto said work.    
     
     
         18 . An illumination optical system for a projection imaging apparatus, comprising: 
 a light source that emits illumination light;    a light beam shape changing element that diffuses incident light emitted by the light source in a plurality of directions;    a zoom optical system that receives the diffused light; and    an optical integrator that receives light from the zoom optical system in a modified illumination configuration having a light intensity distribution such that a lower light intensity is formed at a position near an optical axis relative to positions away from the optical axis, and the optical integrator forms a secondary light source having a modified illumination configuration from the received light.    
     
     
         19 . The system of  claim 18 , wherein: 
 the light beam shape changing element comprises a plurality of interchangeable optical elements.    
     
     
         20 . The system of  claim 19 , wherein: 
 the light beam shape changing element comprises a plurality of interchangeable diffractive optical elements that each form a different modified illumination configuration in cooperation with the zoom optical system at the optical integrator.    
     
     
         21 . The system of  claim 20 , wherein: 
 at least one diffractive optical element uses a phase difference of transmitted light to form a modified illumination configuration.    
     
     
         22 . The system of  claim 18 , wherein: 
 the light beam shape changing element forms a modified illumination configuration on the optical integrator such that edges of illumination regions are inclined with respect to a scanning direction of elemental lenses in the optical integrator.    
     
     
         23 . The system of  claim 18 , wherein: 
 the light beam shape changing element comprises at least one element housed within a protective housing.    
     
     
         24 . The system of  claim 18 , further comprising: 
 a vibrator that vibrates at least one of the light beam shape changing element and an optical device positioned optically between the light beam shape changing element and the optical integrator.    
     
     
         25 . The system of  claim 18 , further comprising: 
 an annular ratio variable optical system that receives light from the light beam shape changing element and transmits light to the zoom optical system,    wherein the light beam shape changing element is a diffractive optical element that forms a ring shaped pattern in a far field, and optical elements within the annular ratio variable optical system are adjustable to vary the annular ratio of an annular illumination pattern formed at the optical integrator.    
     
     
         26 . The system of  claim 25 , wherein: 
 the zoom optical system is adjustable to vary a diameter of the annular illumination pattern formed at the optical integrator.    
     
     
         27 . The system of  claim 25 , wherein: 
 the optical integrator is a wave front splitting type optical integrator.    
     
     
         28 . An illumination optical system for a projection imaging apparatus, comprising: 
 means for generating illumination light;    means for diffusing the emitted light in a plurality of different directions;    means for forming a plurality of light source images from the emitted light; and    means for forming a secondary light source having a modified illumination configuration from light that is diffused and used to form the plurality of light source images, the modified illumination configuration having a light intensity distribution such that a lower light intensity is formed at a position near an optical axis relative to positions away from the optical axis.