Polarization-modulating element, illumination optical apparatus, exposure apparatus, and exposure method

Abstract

An illumination optical apparatus illuminates an object with illumination light. The illumination optical apparatus includes an optical integrator arranged in an optical path of the illumination light; and a polarization modulating member which modulates a polarization of the illumination light, the polarization modulating member being made of an optical material with optical activity and being arranged in the optical path on an incidence side of the optical integrator such that a direction of an optic axis of the optical material is coincident with a direction of an optical axis of the illumination optical apparatus. The polarization modulating member has a thickness profile varying with respect to azimuthal positions about the optical axis.

What is claimed is: 
     
         1 . An illumination optical apparatus which illuminates an object with illumination light, the illumination optical apparatus comprising:
 an optical integrator arranged in an optical path of the illumination light; and   a polarization modulating member which modulates a polarization of the illumination light, the polarization modulating member being made of an optical material with optical activity and being arranged in the optical path on an incidence side of the optical integrator such that a direction of an optic axis of the optical material is coincident with a direction of an optical axis of the illumination optical apparatus,   wherein the polarization modulating member has a thickness profile varying with respect to azimuthal positions about the optical axis.   
     
     
         2 . The illumination optical apparatus according to  claim 1 , wherein the thickness profile is formed so that thicknesses of the polarization modulating member are equal to each other at positions which are located symmetrically with respect to the optical axis. 
     
     
         3 . The illumination optical apparatus according to  claim 2 , wherein the thickness profile is formed so that a first thickness of the polarization modulating member at a first position and a second thickness of the polarization modulating member at a second position are different from each other, the first position and the second position are different from each other with respect to an azimuthal direction about the optical axis. 
     
     
         4 . The illumination optical apparatus according to  claim 3 , wherein the thickness profile is formed so that the thickness profile varies continuously between the first position and the second position with respect to the azimuthal direction. 
     
     
         5 . The illumination optical apparatus according to  claim 3 , wherein the thickness profile is formed so that the thickness profile includes a stepped profile so as to vary discontinuously between the first position and the second position with respect to the azimuthal direction. 
     
     
         6 . The illumination optical apparatus according to  claim 1 , further comprising a polarization state converter arranged in the optical path on an incidence side of the polarization modulating member, wherein
 the polarization state converter converts a polarization state of the illumination light from a first polarization state, in which a principal component is a substantially single polarization light, into a second polarization state different from the first polarization state.   
     
     
         7 . The illumination optical apparatus according to  claim 6 , wherein a principal component of the second polarization state is linearly polarized light polarized in a substantially single direction. 
     
     
         8 . The illumination optical apparatus according to  claim 6 , wherein the polarization state converter comprises at least one of a half wavelength plate and a quarter wavelength plate. 
     
     
         9 . The illumination optical apparatus according to  claim 1 , wherein the polarization modulating member generates an azimuthal polarization state in an annular region on a pupil plane about the optical axis. 
     
     
         10 . The illumination optical apparatus according to  claim 1 , wherein the polarization modulating member generates an azimuthal polarization state in a plurality of substantially discrete regions on a pupil plane about the optical axis. 
     
     
         11 . The illumination optical apparatus according to  claim 10 , wherein the plurality of substantially discrete regions are aligned along a circumference about the optical axis. 
     
     
         12 . The illumination optical apparatus according to  claim 10 , wherein the plurality of substantially discrete regions on the pupil plane comprises a pair of regions arranged symmetrically with respect to the optical axis. 
     
     
         13 . The illumination optical apparatus according to  claim 1 , wherein the optical integrator comprises a fly's eye lens of which a surface of an exit side is arranged at a position substantially equivalent to a pupil plane. 
     
     
         14 . The illumination optical apparatus according to  claim 1 , further comprising a polarization monitor which detects a polarization state of the illumination light from the polarization modulating member. 
     
     
         15 . The illumination optical apparatus according to  claim 14 , wherein the polarization monitor comprises
 a beam splitter arranged in the optical path of the illumination light from the polarization modulating member which takes out a beam that is a part of the illumination light; and   a detector which detects the beam from the beam splitter.   
     
     
         16 . An exposure apparatus which exposes a substrate with light from a pattern on a mask, the exposure apparatus comprising:
 a stage which holds the substrate;   the illumination optical apparatus according to  claim 1 , which illuminates the pattern with the light; and   a projection optical system which projects an image of the pattern illuminated with the light from the illumination optical apparatus onto the substrate held by the stage.   
     
     
         17 . The exposure apparatus according to  claim 16 , configured to expose the substrate with the light through liquid. 
     
     
         18 . The exposure apparatus according to  claim 16 , further comprising a polarization monitor which detects a polarization state of the light from the projection optical system. 
     
     
         19 . The exposure apparatus according to  claim 18 , wherein the polarization monitor which detects the polarization state of the light from the projection optical system is disposed on the stage. 
     
     
         20 . An exposure method which exposes a substrate with light from a pattern on a mask, the exposure method comprising:
 holding the substrate by a stage;   illuminating the pattern with light from the illumination optical apparatus according to  claim 1 ; and   projecting an image of the pattern illuminated with the light from the illumination optical apparatus onto the substrate held by the stage.   
     
     
         21 . The exposure method according to  claim 20 , wherein the substrate is exposed with the light through liquid. 
     
     
         22 . A device manufacturing method, comprising:
 transferring a pattern to a substrate by using the exposure apparatus according to  claim 16 ; and   developing the substrate to which the pattern has been transferred.