Method and apparatus for polarizing electromagnetic radiation

Abstract

According to one aspect of the invention, a method and apparatus for polarizing electromagnetic radiation is provided. The electromagnetic radiation may be divided into first and second portions, substantially all of the first portion may be linearly polarized in a first direction and substantially all of the second portion may be linearly polarized in a second direction, the first direction being substantially orthogonal to the second direction. The linear polarization of at least one of the first and second portions may be changed such that substantially all of both of the first and second portions are linearly polarized in a third direction. At least one of the first and second portions may be redirected such that substantially all of both the first and second portions are propagating in a fourth direction.

1 . A method comprising: 
 dividing electromagnetic radiation into first and second portions, substantially all of the first portion being linearly polarized in a first direction and substantially all of the second portion being linearly polarized in a second direction, the first direction being substantially orthogonal to the second direction;    changing the linear polarization of at least one of the first and second portions such that substantially all of both of the first and second portions are linearly polarized in a third direction; and    redirecting at least one of the first and second portions such that substantially all of both the first and second portions are propagating in a fourth direction.    
   
   
       2 . The method of  claim 1 , wherein the electromagnetic radiation is light.  
   
   
       3 . The method of  claim 2 , wherein said dividing of the light occurs within a polarizing beam splitter, the second portion of light propagating from the beam splitter in substantially the first direction.  
   
   
       4 . The method of  claim 3 , wherein said changing the linear polarization of the at least one of the first and second portions comprises propagating the at least one of the first and second portions through a wave-plate.  
   
   
       5 . The method of  claim 4 , wherein only the first portion of light propagates through the wave-plate.  
   
   
       6 . The method of  claim 5 , wherein the first portion of light propagates from the beam splitter about a central axis of the beam splitter.  
   
   
       7 . The method of  claim 6 , wherein said redirecting comprises: 
 reflecting the second portion of the light propagating from the beam splitter with a first reflective device; and    reflecting the second portion of the light from the first reflective device with a second reflective device, at least some of the second portion of the light intersecting the central axis of the beam splitter after said reflection with the second reflective device.    
   
   
       8 . The method of  claim 7 , wherein said redirecting further comprises reflecting the second portion of the light with a third reflective device such that substantially all of both the first and second portions of the light are propagating in the fourth direction with the second portion of the light being on opposing sides of the central axis of the beam splitter.  
   
   
       9 . The method of  claim 6 , wherein said redirecting comprises diffracting the first and second portions of light, the first and second portions of light propagating in the fourth direction after said diffraction.  
   
   
       10 . The method of  claim 9 , wherein said diffracting is performed by at least one of a hologram and a diffractive optical element.  
   
   
       11 . A method comprising: 
 directing a beam of electromagnetic radiation through a substantially uniform magnetic field, the beam having an axis, the electromagnetic radiation being substantially linearly polarized in a first direction, flux lines of the magnetic field extending in a second direction, the first direction being substantially orthogonal to the second direction, a first line extending from the axis of the beam and a first portion of the beam being substantially perpendicular to the first direction; and    propagating a second portion of the beam through a first material, within the magnetic field, having a first Verdet value, the second portion of the beam being linearly polarized in a third direction after said propagation, a second line extending from the axis of the beam and the second portion of the beam being substantially perpendicular to the third direction.    
   
   
       12 . The method of  claim 11 , further comprising propagating a third portion of the beam through a second material, within the magnetic field, having a second Verdet value, the third portion of the beam being linearly polarized in a fourth direction after said propagation through the second material, a third line extending from the axis of the beam and the third portion of the beam being substantially perpendicular to the fourth direction.  
   
   
       13 . The method of  claim 12 , wherein the first portion of the beam extends from the axis of the beam to an outer edge of the beam, the second portion of the beam extends from the axis of the beam to the outer edge of the beam, and the third portion of the beam extends from the axis of the beam to the outer edge of the beam.  
   
   
       14 . The method of  claim 13 , wherein the electromagnetic radiation is light.  
   
   
       15 . The method of  claim 14 , wherein a cross-section of the beam perpendicular to the axis is substantially circular and the axis of the beam is a central axis.  
   
   
       16 . The method of  claim 15 , wherein the first, second, and third materials have substantially the same Verdet constant, the first material has a first thickness, the second material has second thickness, and the third material has a third thickness.  
   
   
       17 . A semiconductor processing apparatus comprising: 
 a substrate support to support a semiconductor substrate;    an electromagnetic radiation source to emit electromagnetic radiation;    a polarization subsystem comprising: 
 a polarizing beam splitter to split the electromagnetic radiation into first and second portions, substantially all of the first portion being linearly polarized in a first direction and substantially all of the second portion being linearly polarized in a second direction, the first direction being substantially orthogonal to the second direction;  
 at least one wave-plate to change the linear polarization of at least one of the first and second portions such that substantially all of both of the first and second portions are linearly polarized in a third direction; and  
 at least one reflective device to reflect at least one of the first and second portions such that substantially all of both the first and second portions are propagating in a fourth direction; and  
   a reticle positioned between the polarization subsystem and the substrate support, the first and second portions of the electromagnetic radiation to pass through the reticle onto the semiconductor substrate.    
   
   
       18 . The semiconductor substrate processing apparatus of  claim 17 , wherein the at least one wave-plate comprises a half wave-plate to change the linear polarization of the first portion of electromagnetic radiation from the first direction to the second direction and the second and third directions are substantially parallel.  
   
   
       19 . The semiconductor substrate processing apparatus of  claim 18 , wherein the first portion propagates from the beam splitter and through the half wave-plate about a central axis of the beam splitter.  
   
   
       20 . The semiconductor substrate processing apparatus of  claim 19 , wherein the at least one reflective device comprises a first mirror to reflect the second portion of light from the beam splitter, a second mirror to reflect the second portion of light from the first mirror, and a third mirror having portions on opposing sides of the central axis of the beam splitter to reflect the second portion of light from the second mirror into the fourth direction.  
   
   
       21 . The semiconductor substrate processing apparatus of  claim 20 , wherein the third mirror has an opening therein, the first portion of electromagnetic radiation propagating through the opening in the fourth direction.  
   
   
       22 . The semiconductor substrate processing apparatus of  claim 17 , wherein the first and second portions of electromagnetic radiation jointly form a beam of electromagnetic radiation, the beam having an axis, and wherein the polarization subsystem further comprises: 
 a magnetic field generator to generate a substantially uniform magnetic field, flux lines of the magnetic field extending substantially in the fourth direction, the beam of electromagnetic radiation to propagate through the magnetic field, a first line extending from the axis of the beam and a first portion of the beam being substantially perpendicular to the third direction; and    a first piece of material, having a first Verdet value, within the magnetic field, a second portion of the beam to propagate through the first piece of material, the second portion being linearly polarized in a fifth direction after said propagation through the first piece of material, a second line extending from the axis of the beam to the second portion of the beam being substantially perpendicular to the fifth direction.    
   
   
       23 . The semiconductor substrate processing apparatus of  claim 22 , wherein the polarization subsystem further comprises a second piece of material, having a second Verdet value, within the magnetic field, a third portion of the beam to propagate through the second piece of material, the third portion of the beam being linearly polarized in a sixth direction after said propagation through the second piece of material, a third line extending from the axis of the beam to the third portion of the beam being substantially perpendicular to the sixth direction.  
   
   
       24 . The semiconductor substrate processing apparatus of  claim 23 , wherein the first portion of the beam extends from the axis of the beam to an outer edge thereof, the second portion of the beam extends from the axis to the outer edge of the beam, and the third portion of the beam extends from the axis of the beam to the outer edge of the beam.  
   
   
       25 . The semiconductor substrate processing apparatus of  claim 24 , wherein the electromagnetic radiation source is a light source, a cross-section of the beam perpendicular to the axis of the beam is substantially circular, the axis of the beam is a central axis, the first, second, and third materials have substantially the same Verdet constant, the first material has a first thickness, the second material has a second thickness, and the third material has a third thickness.  
   
   
       26 . A semiconductor substrate processing apparatus comprising: 
 a substrate support to support a semiconductor substrate;    an electromagnetic radiation source to emit electromagnetic radiation;    a polarization subsystem comprising: 
 a polarizing beam splitter being radially symmetric about a central axis thereof to split the electromagnetic radiation into first and second portions, each of the first and second portions having a plurality of sections, the first portion propagating in a first direction substantially parallel to the central axis of the beam splitter, each respective section of the first portion being linearly polarized in an a direction parallel to a line extending between the central axis of the beam splitter and the respective section of the first portion, the second portion propagating radially from the central axis of the beam splitter, each respective section of the second portion being linearly polarized in a direction perpendicular to a line extending between the central axis of the beam splitter and the respective section of the second portion;  
 a wave-plate being radially symmetric about the central axis of the beam splitter to change the linear polarization of the first portion of the first portion such that each respective section of the first portion is linearly polarized in a direction perpendicular to the line extending between the central axis of the beam splitter and the respective section of the first portion; and  
 at least one reflective device to reflect the second portion from the beam splitter into substantially the first direction; and  
   a reticle positioned between the polarization subsystem and the substrate support, the first and second portions of the electromagnetic radiation to pass through the reticle and onto the semiconductor wafer.    
   
   
       27 . The semiconductor substrate processing apparatus of  claim 26 , wherein the at least one reflective device comprises a first annular mirror being radially symmetric about the central axis of the beam splitter to reflect the second portion of electromagnetic radiation from the beam splitter, a second annular mirror being radially symmetric about the central axis of the beam splitter to reflect the second portion of the electromagnetic radiation from the first mirror, and a third annular mirror being radially symmetric about the central axis of the beam splitter to reflect the second portion of electromagnetic radiation from the second mirror into the first direction.  
   
   
       28 . The semiconductor substrate processing apparatus of  claim 27 , wherein the third mirror has an opening therein, the first portion of electromagnetic radiation to propagate through the opening in the first direction.  
   
   
       29 . The semiconductor substrate processing apparatus of  claim 28 , wherein the electromagnetic radiation source is a light source.