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: 
 interchangeable optical elements which are interchangeably set at a light path to produce a desired light intensity distribution on a predetermined plane;    an axicon which is arranged in an optical path between a position where the optical element is set and the surface;    a zoom optical system which is arranged in the optical path between a position where the optical element is set and the surface; and    an optical integrator which is arranged in an optical path between the zoom optical system and the surface.    
     
     
         2 . The system according to  claim 1 , wherein the optical elements have a diffractive optical element.  
     
     
         3 . The system according to  claim 2 , wherein the optical elements comprising at least one of an optical element which produces a circular light intensity distribution, an optical element which produces an annular light intensity distribution, and an optical element which produces a multipole light intensity distribution.  
     
     
         4 . The system according to  claim 3 , wherein the zoom optical system is arranged in an optical path between the axicon and the optical integrator.  
     
     
         5 . The system according to  claim 1 , wherein the optical elements comprise at least one of an optical element which produces a circular light intensity distribution, an optical element which produces an annular light intensity distribution, and an optical element which produces a multipole light intensity distribution.  
     
     
         6 . The system according to  claim 5 , wherein the optical element is arranged in a parallel light beam from the light source.  
     
     
         7 . The system according to  claim 1 , wherein the zoom optical system is arranged in an optical path between the axicon and the optical integrator.  
     
     
         8 . The system according to  claim 1 , wherein the axicon has an adjustable axicon.  
     
     
         9 . 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.    
     
     
         10 . 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.    
     
     
         11 . A lithographic method comprising the steps of: 
 generating a light beam;    producing a desired light intensity distribution on a predetermined plane by use of optical elements which are interchangeably set at a light path; and    generating a multipole illumination mode, using an adjustable axicon and a zoom optical system, based on a light from the optical element, whereby at least one spatial parameter of the multipole illumination can be continuously varied.