Methods of determining quality of a light source

Abstract

Methods for determining a quality of a light source applied to a photolithographic process are provided. An image sensor array is exposed to a light from a light source. Addresses and respective intensities corresponding to a plurality of locations on a pupil map representing intensity of the light from on the image sensor array. At least one of an inner curve and an outer curve of the pupil map is defined based upon the collected addresses and respective intensities. The light source is applied to a photolithographic process if the addresses have a predetermined pattern relative to the at least one of the inner curve and the outer curve.

What is claimed is: 
     
       1. A method of determining a quality of a light source applied to a photolithographic process, comprising:
 a) exposing an image sensor array to a light from the light source;   b) collecting addresses and respective intensities corresponding to a plurality of locations on a pupil map representing intensity of the light from the light source on the image sensor array;   c) summing together the intensities to calculate a total intensity of the light from the light source collected by the image sensor array;   d) defining at least one of an inner curve or an outer curve on the pupil map, the at least one of the inner curve or the outer curve having a radius that corresponds to a percentage of the total intensity of the light collected by the image sensor array; and   e) applying the light source to a photolithographic process for forming a device on a semiconductor wafer if a predetermined amount of a normalized intensity contour line is disposed externally of or within the at least one of the inner curve or the outer curve, respectively.   
     
     
       2. The method of  claim 1 , wherein the at least one of the inner curve or the outer curve include at least one selected from a group consisting of a circle, an oval, and a part of a circle. 
     
     
       3. The method of  claim 1 , wherein addresses on the inner circle correspond to intensities having equal or approximately equal normalized intensities. 
     
     
       4. The method of  claim 1 , further comprising:
 f) converting the addresses and the intensities into a three-dimensional (3-D) drawing; and   g) cross-sectioning the 3-D drawing to generate an intensity distribution pattern externally of or within the at least one of the inner curve or the outer curve, respectively.   
     
     
       5. The method of  claim 4 , wherein the intensity distribution pattern is generated by a polynomial regression method. 
     
     
       6. The method of  claim 1 , wherein the addresses are based on a Cartesian coordinate system, the method further comprising transforming the addresses to a Polar coordinate system. 
     
     
       7. The method of  claim 1 , further comprising:
 f) modifying the light source if the predetermined amount of the normalized intensity contour line is not disposed externally of or within the at least one of the inner curve or the outer curve, respectively; and   g) repeating steps a) through e).   
     
     
       8. A method of determining a quality of a light source applied to a photolithographic process, comprising:
 a) exposing an image sensor array to a light from the light source;   b) collecting addresses and respective intensities corresponding to a plurality of locations on a pupil map representing intensity of the light from the light source on the image sensor array;   c) defining at least one of an inner curve or an outer curve on the pupil map based upon the collected addresses and respective intensities, the at least one of the inner curve or the outer curve having a radius that corresponds to a percentage of a sum total of the intensities of the light from the light source collected by the image sensor array;   d) converting the addresses and the intensities into a three-dimensional (3-D) drawing;   e) cross-sectioning the 3-D drawing to generate an intensity distribution pattern externally of or within the at least one of the inner curve or the outer curve, respectively; and   f) applying the light source to a photolithographic process for forming a device on a semiconductor wafer if a predetermined amount of the intensity distribution pattern is disposed externally of or within the at least one of the inner curve or the outer curve, respectively.   
     
     
       9. The method of  claim 8 , wherein addresses on the inner circle correspond to intensities having equal or approximately equal normalized intensities. 
     
     
       10. The method of  claim 8 , wherein the at least one of the inner curve or the outer curve include at least one selected from a group consisting of a circle, an oval, and a part of a circle. 
     
     
       11. The method of  claim 8 , wherein the intensity distribution pattern is generated by a polynomial regression method. 
     
     
       12. The method of  claim 8 , wherein the addresses are based on a Cartesian coordinate system, the method further comprising transforming the addresses to a Polar coordinate system. 
     
     
       13. The method of  claim 8 , further comprising:
 g) modifying the light source if the predetermined amount of the intensity distribution pattern is not disposed externally of or within the at least one of the inner curve or the outer curve, respectively; and   h) repeating steps a) through f).   
     
     
       14. A non-transitory computer readable storage medium encoded with program code, wherein when the program code is executed by a processor, the processor performs a method, the method comprising:
 a) exposing an image sensor array to a light from a light source;   b) collecting addresses and respective intensities corresponding to a plurality of locations on a pupil map representing intensity of the light from the light source on the image sensor array;   c) summing together the intensities to calculate a total intensity of the light from the light source collected by the image sensor array;   d) defining at least one of an inner curve or an outer curve on the pupil map, the at least one of the inner curve or the outer curve having a radius that corresponds to a percentage of the total intensity of the light collected by the image sensor array; and   e) determining if a predetermined amount of a normalized intensity contour line is disposed externally of or within the at least one of the inner curve or the outer curve, respectively.   
     
     
       15. The non-transitory computer readable storage medium of  claim 14 , wherein the method includes:
 f) applying the light source to a photolithographic process if the predetermined amount of the normalized intensity contour line is disposed externally of or within the at least one of the inner curve or the outer curve, respectively; and   g) modifying the light source if the predetermined amount of the normalized intensity contour line is not disposed externally of or within the at least one of the inner curve or the outer curve, respectively.   
     
     
       16. The non-transitory computer readable storage medium of  claim 14 , wherein addresses on the inner circle correspond to intensities having equal or approximately equal normalized intensities. 
     
     
       17. The non-transitory computer readable storage medium of  claim 14 , wherein the method further comprises:
 f) converting the addresses and the intensities into a three-dimensional (3-D) drawing; and   g) cross-sectioning the 3-D drawing to generate an intensity distribution pattern externally of or within the at least one of the inner curve or the outer curve, respectively.   
     
     
       18. The non-transitory computer readable storage medium of  claim 14 , wherein the intensity distribution pattern is generated by a polynomial regression method. 
     
     
       19. The non-transitory computer readable storage medium of  claim 14 , wherein the addresses are based on a Cartesian coordinate system, the method further comprising transforming the addresses to a Polar coordinate system. 
     
     
       20. The non-transitory computer readable storage medium of  claim 14 , wherein the method includes:
 h) repeating steps a) through f) if the predetermined amount of the normalized intensity contour line is not disposed externally of or within the at least one of the inner curve or the outer curve, respectively.   
     
     
       21. A method, comprising:
 providing intensities corresponding to a plurality of locations on a pupil map representing intensity of a light from a light source on an image sensor array at the plurality of locations;   normalizing the intensity of the light at the plurality of locations;   dividing the pupil map into a plurality of segments each defined by a first boundary line and a second boundary line, wherein the boundary lines are defined based on a periodic profile of distribution of the plurality of locations having a first normalized intensity; and   defining at least one of an inner curve or an outer curve for each of the plurality of segments based upon the normalized intensity of the light at the plurality of locations, a selected one of the at least one of the inner curve or the outer curve having a radius that corresponds to a first one of the plurality of locations having the first normalized intensity that is located adjacent to a second one of the plurality of locations having a second normalized intensity, and wherein each of the at least one of the inner curve and the outer curve define an edge region;   determining an effective area of each of the plurality of segments, wherein the effective area is related to the normalized intensity of the light at each of the plurality of locations within the edge region;   applying the light source to a semiconductor wafer to form a device on the semiconductor wafer only when the effective area of a predetermined number of the plurality of segments is larger than a predetermined value.   
     
     
       22. The method of claim 21, wherein the effective area of the plurality of segments is a ratio N/T, where N is a number of the plurality of locations with the first normalized intensity within a first segment and the at least one of the inner curve or the outer curve and T is a number of the plurality of locations with the second normalized intensity and the first normalized intensity within the first segment and the at least one of the inner curve or the outer curve. 
     
     
       23. The method of claim 21, further comprising exposing the image sensor array to the light from the light source before the providing step. 
     
     
       24. The method of claim 21, wherein the plurality of segments are separated from each other by the boundary lines. 
     
     
       25. The method of claim 21, wherein each of the plurality of segments includes at least a respective one of the plurality of locations. 
     
     
       26. A method, comprising:
 providing intensities corresponding to a plurality of locations on a pupil map representing intensity of a light from a light source on an image sensor array at the plurality of locations;   normalizing the intensities at the plurality of locations;   dividing the pupil map into a plurality of segments each defined by a first boundary line and a second boundary line, wherein the boundary lines are defined based on a periodic profile of distribution of the plurality of locations having a first normalized intensity; and   applying the light source to a semiconductor wafer to form a device on the semiconductor wafer only when a predetermined number of the plurality of segments have an effective area larger than a predetermined value.   
     
     
       27. The method of claim 26, further comprising defining at least one of an inner curve or an outer curve on the pupil map based upon the normalized intensities. 
     
     
       28. The method of claim 27, wherein the effective area of the plurality of segments is a ratio N/T, where N is a number of the plurality of locations with the first normalized intensity within a first segment and the at least one of the inner curve or the outer curve and T is a number of the plurality of locations with a second normalized intensity and the first normalized intensity within the first segment and the at least one of the inner curve or the outer curve. 
     
     
       29. The method of claim 26, further comprising exposing the image sensor array to the light from the light source before the providing step. 
     
     
       30. The method of claim 26, wherein the plurality of segments are separated from each other by the boundary lines. 
     
     
       31. The method of claim 26, wherein each of the plurality of segments includes at least a respective one of the plurality of locations.