Optimized optical lithography illumination source for use during the manufacture of a semiconductor device

Abstract

A method and structure for optimizing an optical lithography illumination source comprises a shaped diffractive optical element (DOE) interposed between the illuminator and a lens during the exposure of a photoresist layer over a semiconductor wafer. The DOE may, in some instances, increase depth of focus, improve the normalized image log-slope, and improve pattern fidelity. The DOE is customized for the particular pattern to be exposed. Descriptions and depictions of specific DOE's are provided. Additionally, a pupilgram having a particular pattern, and methods for forming the pupilgram, are discussed.

1 . A method used during fabrication of a semiconductor device, comprising: 
 providing a light mask comprising a vertical axis and a horizontal axis and a plurality of openings therethrough;    interposing the light mask between an optical lithography illuminator and a photomask;    shaping a coherent light source from the optical lithography illuminator by passing the coherent light source through: 
 first and second openings of about the same area in the light mask, the first and second openings being equidistant from, and mirror images each with the other, about the horizontal axis; and  
 third and fourth openings of about the same area in the light mask, the third and fourth openings being equidistant from, and mirror images each with the other, about the vertical axis;  
   wherein the areas of the third and fourth openings are substantially different from the areas of the first and second openings; and    passing the shaped coherent light source through the photomask.    
   
   
       2 . The method of  claim 1  further comprising passing the coherent light source through the first and second openings, each comprising a dimension in a first direction which is about 2.0 inches and a dimension in a second direction perpendicular with the first direction which is about 0.5 inches.  
   
   
       3 . The method of  claim 2  further comprising passing the coherent light source through the first and second openings, wherein the dimension in the second direction is a first dimension in the second direction and wherein each of the first and second openings in the light mask has second dimension in the second direction which is about 0.6 inches and has an edge located about 1.9 inches from the horizontal axis.  
   
   
       4 . The method of  claim 1  further comprising passing the coherent light source through the third and fourth openings, each comprising an arc length of about 78 degrees and located about 1.4 inches from the vertical axis.  
   
   
       5 . The method of  claim 4  further comprising passing the coherent light source through the third and fourth openings, each comprising a step on an inside wall and a flat edge on an outside radius located furthest from the vertical axis.  
   
   
       6 . A method used during fabrication of a semiconductor device, comprising: 
 providing a light mask comprising a central point and a plurality of openings therethrough;    interposing the light mask between an optical lithography illuminator and a photomask;    shaping a coherent light source from the optical lithography illuminator by passing the coherent light source through: 
 first and second openings in the light mask, the first and second openings being equidistant from, and mirror images each with the other, about the central point, and each being defined on first and second sides by concentric arcs having an arc length of 30 degrees and on third and fourth sides by first and second nonparallel lines having a radial length extending from 0.5 inches to 2.26 inches from one of a vertical axis and horizontal axis; and  
 third and fourth openings in the light mask, the third and fourth openings being equidistant from, and mirror images, each with the other, about the other of the vertical axis and horizontal axis, and each being defined on first and second sides by concentric arcs having an arc length of 100 degrees and on third and fourth sides by nonparallel lines having a radial length extending from 0.5 inches to 2.26 inches from the central point; and  
   passing the shaped coherent light source through the photomask.    
   
   
       7 . The method of  claim 6  further comprising passing the coherent light source through the light mask having the central point defined by an intersection of a vertical axis and a horizontal axis.  
   
   
       8 . A method used during fabrication of a semiconductor device, comprising: 
 providing a photosensitive layer;    exposing the photosensitive layer to a light pattern comprising areas having first and second light intensities, wherein the first intensity is higher than the second intensity, and the pattern further comprises: 
 first and second first intensity pattern elements each centered on a first axis wherein each of the first and second first intensity pattern elements sweeps about 100°, with about 50° on each side of the first axis;  
 third and fourth first intensity pattern elements each centered on a second axis which is perpendicular to the first axis, wherein each of the third and fourth first intensity pattern elements sweeps about 30°, with about 15° on each side of the horizontal axis; and  
 four second intensity pattern elements with each of the second intensity pattern elements sweeping about 25°, wherein each second intensity pattern element separates two adjacent first intensity pattern elements,  
 wherein an inside radius of the first intensity pattern elements is about 0.72 σ and an outside radius of the first intensity pattern elements is about 0.92σ.  
   
   
   
       9 . A method used during fabrication of a semiconductor device, comprising: 
 providing a photosensitive layer;    exposing the photosensitive layer to a light pattern comprising areas having first and second light intensities, wherein the first intensity is higher than the second intensity, and the pattern further comprises: 
 first and second second intensity pattern elements each centered on a first axis wherein each of the first and second second intensity pattern elements sweeps about 100°, with about 50° on each side of the first axis;  
 third and fourth second intensity pattern elements each centered on a second axis which is perpendicular to the first axis, wherein each of the third and fourth second intensity pattern elements sweeps about 30°, with about 15° on each side of the horizontal axis; and  
 four first intensity pattern elements with each of the first intensity pattern elements sweeping about 25°, wherein each first intensity pattern element separates two adjacent second intensity pattern elements,  
   wherein an inside radius of the second intensity pattern elements is about 0.72 σ and an outside radius of the second intensity pattern elements is about 0.92σ.    
   
   
       10 . A method used during fabrication of a semiconductor device, comprising: 
 providing a light mask comprising a vertical axis and a horizontal axis and a plurality of openings therethrough;    interposing the light mask between an optical lithography illuminator and a photomask;    shaping a coherent light source form the optical lithography illuminator by passing the coherent light source through: 
 first and second openings in the light mask, the first and second openings being mirror images, each with the other, about one of the vertical and horizontal axes, and each being defined on first and second sides by concentric arcs having an arc length of 30 degrees and on third and fourth sides by first and second nonparallel lines having a radial length extending from 0.5 inches to 2.26 inches from one of the vertical axis and the horizontal axis; and  
 third and fourth openings in the light mask, the third and fourth openings being mirror images, each with the other, about one of the vertical and horizontal axes, and each being defined on first and second sides by concentric arcs having an arc length of 100 degrees on third and fourth sides by first and second nonparallel lines having a radial length extending from 0.5 inches to 2.26 inches from one of the vertical axis and the horizontal axis, wherein the light mask comprises only the first, second, third, and fourth openings therein adapted for the passage of light therethrough.  
   
   
   
       11 . A method used during fabrication of a semiconductor device, comprising: 
 providing a light mask comprising a vertical axis and a horizontal axis and a plurality of openings therethrough;    interposing the light mask between an optical lithography illuminator and a photomask;    shaping a coherent light source from the optical lithography illuminator by passing the coherent light source through: 
 first and second openings in the light mask, the first and second openings being mirror images, each with the other, about one of the vertical and horizontal axes, and each defined on first and second sides by concentric arcs having a first arc length and on third and fourth sides by first and second nonparallel lines having a second radial length extending from one of the vertical axis and the horizontal axis; and  
 third and fourth openings in the light mask, the third and fourth openings being mirror images, each with the other, about one of the vertical and horizontal axes, and each defined on first and second sides by concentric arcs having a second arc length different from the first arc length on third and fourth sides by first and second nonparallel lines having a second radial length different from the first radial length extending from one of the vertical axis and the horizontal axis; and  
   passing the shaped coherent light source through the photomask.    
   
   
       12 . The method of  claim 11  further comprising passing the coherent light source through the light mask which comprises only the first, second, third, and fourth openings therein adapted for the passage of light therethrough.