Radially polarized light in lithographic apparatus

Abstract

The present invention relates to a lithographic apparatus and a method of using the apparatus in the manufacture of a device such as an integrated circuit (IC). In particular, the present invention relates to a lithographic apparatus designed to be used with radiation having a wavelength in the Deep Ultra-Violet (DUV) and wherein radially polarized light is used to enhance the image contrast. In particular the present invention relates to partial clipping of the first order.

1 . A lithographic apparatus comprising: 
 an illumination system configured to condition a radiation beam;    a support constructed to support a patterning device, the patterning device being capable of imparting the radiation beam with a pattern in its cross-section;    a substrate table constructed to hold a substrate; and    a projection system configured to project the radiation beam, after it has been patterned, onto a target portion of the substrate;    wherein the radiation beam is substantially radially polarized which has the effect of improving the image contrast.    
   
   
       2 . A lithographic apparatus according to  claim 1 , wherein the radiation beam is radially polarized substantially at a pupil plane of the illumination system.  
   
   
       3 . A lithographic apparatus according to  claim 1 , wherein the radiation beam is radially polarized at its source.  
   
   
       4 . A lithographic apparatus according to  claim 1 , wherein the radiation beam is more than about 80% radially polarized.  
   
   
       5 . A lithographic apparatus according to  claim 1 , wherein the radial polarization is obtained by positioning a polarizing optical element in a pupil plane of an illuminator of the lithographic apparatus.  
   
   
       6 . A lithographic apparatus according to  claim 4 , wherein the polarizing optical element changes the direction of the E-field vector.  
   
   
       7 . A lithographic apparatus according to  claim 1 , wherein by using radially polarized on-axis illumination allows the image contrast to be improved thereby allowing dense features to be formed.  
   
   
       8 . A lithographic apparatus according to  claim 1 , wherein using radially polarized illumination allows k 1  values down to about 0.28 to be formed.  
   
   
       9 . A lithographic apparatus according to  claim 1 , wherein the radially polarized illumination is any of diamond, circular, star-shaped or rectangularly shaped on-axis illumination.  
   
   
       10 . A lithographic apparatus according to  claim 1 , wherein about 12.5% of the first order is clipped by a variable numerical aperture diaphragm.  
   
   
       11 . A lithographic apparatus according to  claim 1 , wherein the projection system comprises a variable numerical aperture.  
   
   
       12 . A lithographic apparatus according to  claim 1 , wherein the radiation used in the lithographic apparatus has a wavelength of about 157 nm, 193 nm, 248 nm or 365 nm.  
   
   
       13 . A lithographic apparatus according to  claim 1 , wherein the depth of focus is also enhanced by clipping the first order.  
   
   
       14 . A lithographic apparatus wherein a substantially radially polarized radiation beam is used which has the effect of enhancing the image contrast.  
   
   
       15 . A lithographic apparatus according to  claim 14 , wherein the radiation beam is more than about 80% radially polarized.  
   
   
       16 . A lithographic apparatus according to  claim 14 , comprising a polarizing optical element in a pupil plane of an illuminator of the illumination system.  
   
   
       17 . A lithographic apparatus according to  claim 14 , wherein the polarizing optical element changes a direction of the E-field vector.  
   
   
       18 . A lithographic apparatus according to  claim 14 , wherein using radially polarized on-axis illumination allows the image contrast to be improved thereby allowing dense features to be formed.  
   
   
       19 . A lithographic apparatus according to  claim 14 , wherein using radially polarized illumination allows k 1  values down to about 0.28 to be formed.  
   
   
       20 . A lithographic apparatus according to  claim 14 , wherein the radially polarized illumination is any of diamond, circular, star-shaped or rectangularly shaped on-axis illumination.  
   
   
       21 . A lithographic apparatus according to  claim 14 , wherein about 12.5% of the first order is clipped by a variable numerical aperture diaphragm.  
   
   
       22 . A lithographic apparatus according to  claim 14 , wherein the lithographic apparatus comprises a variable numerical aperture.  
   
   
       23 . A lithographic apparatus according to  claim 14 , wherein the radiation used in the lithographic apparatus has a wavelength of about 157 nm, 193 nm, 248 nm or 365 nm.  
   
   
       24 . A lithographic apparatus according to  claim 14 , wherein the depth of focus is also enhanced by clipping the first order.  
   
   
       25 . A device manufacturing method comprising: 
 radially polarizing a beam of radiation;    patterning the beam of radiation; and    projecting the beam of radiation, after it has been patterned, onto a target portion of a substrate.    
   
   
       26 . A method according to  claim 25  wherein the radially polarizing further comprises producing the beam of radiation with a substantially radial polarization.  
   
   
       27 . A method according to  claim 25  wherein the radially polarizing further comprises radially polarizing the beam of radiation prior to the patterning.  
   
   
       28 . A device manufacturing method according to  claim 25 , wherein the radiation beam is more than about 80% polarized.  
   
   
       29 . A device manufacturing method according to  claim 25 , further comprising: 
 positioning a polarizing optical element in a pupil plane of an illumination system of a lithographic apparatus used in the method to form the beam of substantially radially polarized radiation.    
   
   
       30 . A device manufacturing method according to  claim 25 , wherein the polarizing optical element changes the direction of the E-field vector.  
   
   
       31 . A device manufacturing method according to  claim 25 , wherein using radially polarized on-axis illumination allows the image contrast to be improved thereby allowing dense features to be formed.  
   
   
       32 . A device manufacturing method according to  claim 25 , wherein using radially polarized illumination allows k 1  values down to about 0.28 to be formed.  
   
   
       33 . A device manufacturing method according to  claim 25 , wherein the radially polarized illumination is any of diamond, circular, star-shaped or rectangularly shaped on-axis illumination.  
   
   
       34 . A lithographic apparatus according to  claim 25 , wherein about 12.5% of the first order is clipped by a variable numerical aperture diaphragm.  
   
   
       35 . A device manufacturing method according to  claim 34 , wherein the numerical aperture is tuned to enhance the image contrast.  
   
   
       36 . A device manufacturing method according to  claim 25 , wherein the radiation used in the lithographic apparatus has a wavelength of about 157 nm, 193 nm, 248 nm and 365 nm.  
   
   
       37 . A device manufacturing method according to  claim 25 , wherein the depth of focus is also enhanced by clipping the first order.  
   
   
       38 . A device manufacturing method comprising: 
 providing a substrate;    providing a conditioned radiation beam using an illumination system;    imparting a pattern to the radiation beam; and    projecting the patterned beam of radiation onto a target portion of the substrate; and    substantially radially polarizing the radiation beam to enhance image contrast.    
   
   
       39 . A device manufacturing method according to  claim 38 , wherein the radiation beam is more than about 80% radially polarized.  
   
   
       40 . A device manufacturing method according to  claim 38 , wherein the radially polarizing further comprises positioning a polarizing optical element in a pupil plane of an illuminator of the illumination system.  
   
   
       41 . A device manufactured according to the method of: 
 projecting a patterned beam of radiation onto a substrate;    wherein the radiation beam is substantially radially polarized which has the effect of improving the image contrast.    
   
   
       42 . A device manufactured according to  claim 41 , wherein the manufactured device is any of the following: integrated circuits (ICs), integrated optical systems, guidance and detection patterns for magnetic domain memories, liquid crystal displays (LCDs) and thin-film magnetic heads.