Illumination optical system, exposure apparatus, and exposure method

Abstract

An illumination optical system illuminates an irradiated surface with light supplied from a light source. The illumination optical system includes a diffractive optical element disposed in an optical path of linearly polarized light supplied from the light source. The diffractive optical element forms a multipole illumination field. including a plurality of illumination fields. The illumination optical system also includes an optical integrator that forms a multipole light source including a plurality of planar light sources with light that has passed through the multipole illumination field. The illumination optical system also includes a polarization optical member disposed in an illumination optical path and that sets a polarization direction of light that has passed through the multipole light source to a predetermined polarization direction.

1 . An illumination optical system that illuminates an irradiated surface with light supplied from a light source, the illumination optical system comprising:
 a diffractive optical element disposed in an optical path of linearly polarized light supplied from the light source and that forms a multipole illumination field including a plurality of illumination fields;   an optical integrator that forms a multipole light source including a plurality of planar light sources with light that has passed through the multipole illumination field; and   a polarization optical member disposed in an illumination optical path and that sets a polarization direction of light that has passed through the multipole light source to a predetermined polarization direction.   
     
     
         2 . The illumination optical system according to  claim 1 , wherein the diffractive optical element forms two illumination fields aligned along a first direction crossing an optical axis of the illumination optical system. 
     
     
         3 . The illumination optical system according to  claim 2 , wherein the polarization optical member sets the predetermined polarization direction to a second direction perpendicular to the first direction. 
     
     
         4 . The illumination optical system according to  claim 3 , wherein the diffractive optical element is interchangeable with a second diffractive optical element that forms two illumination fields aligned along the second direction. 
     
     
         5 . The illumination optical system according to claim , wherein when the second diffractive optical element is set in the illumination optical path, the polarization optical member sets the predetermined polarization direction to the first direction. 
     
     
         6 . The illumination optical system according to  claim 1 , wherein the polarization optical member includes a phase member that is arranged in the optical path of the illumination optical system and that rotates the polarization direction of the linearly polarized light about an optical axis of the illumination optical system. 
     
     
         7 . The illumination optical system according to  claim 6 ,
 wherein the phase member is a ½ wavelength plate, which is rotatable about the optical axis.   
     
     
         8 . The illumination optical system according to  claim 6 ,
 wherein the polarization optical member includes a second phase member, which is arranged closer to the light source than the phase member in the optical path of the illumination optical system and that changes an elliptical degree of the polarized light emitted by the polarization optical member.   
     
     
         9 . The illumination optical system according to  claim 8 ,
 wherein the second phase member includes a ¼ wavelength plate, which is rotatable about the optical axis.   
     
     
         10 . The illumination optical system according to  claim 1 ,
 wherein the illumination optical system is used in an exposure apparatus while a mask and a substrate are being moved in a scan direction, and the substrate is exposed via a projection optical system; and   the predetermined polarization direction is the scan direction or a direction perpendicular to the scan direction.   
     
     
         11 . The illumination optical system according to  claim 1 ,
 wherein the multipole illumination field and light source are dipole or quadrupole.   
     
     
         12 . The illumination optical system according to  claim 1 , further comprising:
 a depolarizer that is selectively positioned in the optical path of the illumination optical system.   
     
     
         13 . The illumination optical system according to  claim 1 , wherein the linearly polarized light supplied from the light source has a polarization degree of 95% or more. 
     
     
         14 . A method of illuminating an irradiated surface with light supplied from a light source, the method comprising:
 diffracting linearly polarized light from the light source to form a multipole illumination field including a plurality of illumination fields;   forming a multipole light source including a plurality of planar light sources with light that has passed through the multipole illumination field; and   setting a polarization direction of light that has passed through the multipole light source to a predetermined polarization direction.   
     
     
         15 . The illumination method according to  claim 14 ,
 wherein forming the multipole illumination field includes forming two illumination fields aligned along a first direction crossing an optical axis of an illumination optical system that performs the method.   
     
     
         16 . The illumination method according to  claim 15 ,
 wherein the predetermined polarization direction is set to a second direction perpendicular to the first direction.   
     
     
         17 . The illumination method according to  claim 16 ,
 wherein forming the multipole illumination field includes forming two illumination fields aligned along the second direction, instead of forming the two illumination fields aligned along the first direction.   
     
     
         18 . The illumination method according to  claim 17 ,
 wherein when the two illumination fields aligned along the second direction are formed, the predetermined polarization direction is set to the first direction.   
     
     
         19 . The illumination method according to  claim 14 ,
 wherein setting the polarization direction to the predetermined polarization direction includes rotating the polarization direction of the linearly polarized light about an optical axis of an illumination optical system that performs the method.   
     
     
         20 . The illumination method according to  claim 19 ,
 wherein setting the polarization direction to the predetermined polarization direction includes changing an elliptical degree of polarized light that is emitted, and   the polarization direction of the linearly polarized light about the optical axis of the illumination optical system is rotated subsequent to changing the elliptical degree.   
     
     
         21 . The illumination method according to  claim 14 ,
 wherein the illumination method is used in an exposure process while a mask and a substrate are being moved in a scan direction, and the substrate is exposed via a projection optical system; and   the predetermined polarization direction is the scan direction or a direction perpendicular to the scan direction.   
     
     
         22 . The illumination method according to  claim 14 ,
 wherein the multipole illumination field and light source are dipole or quadrupole.   
     
     
         23 . The illumination method according to  claim 14 ,
 wherein the linearly polarized light supplied from the light source has a polarization degree of 95% or more.