Multi-exposure lithography employing differentially sensitive photoresist layers

Abstract

A stack of a second photoresist having a second photosensitivity and a first photoresist having a first photosensitivity, which is greater than second photosensitivity, is formed on a substrate. A first pattern is formed in the first photoresist by a first exposure and a first development, while the second photoresist underneath remains intact. A second pattern comprising an array of lines is formed in the second photoresist. An exposed portion of the second photoresist underneath a remaining portion of the first photoresist forms a narrow portion of a line pattern, while an exposed portion of the second photoresist outside the area of the remaining portions of the photoresist forms a wide portion of the line pattern. Each wide portion of the line pattern forms a bulge in the second pattern, which increases overlay tolerance between the second pattern and the pattern of conductive vias.

1 . A patterned structure comprising:
 at least one exposed second photoresist portion located on a substrate and laterally abutted by at least one second photoresist portion, wherein said at least one second photoresist portion comprises a second unexposed photosensitive material and said at least one exposed second photoresist portion comprises a second exposed photosensitive material, wherein said second exposed photoresist material is a material derived from said second unexposed photoresist material by lithographic exposure; and   at least one exposed first photoresist portion located directly on said at least one exposed second photoresist portion and said at least one second photoresist portion and comprising a first exposed photosensitive material.   
     
     
         2 . The patterned structure of  claim 1 , wherein said first exposed photoresist material is a material derived from a first unexposed photoresist material by lithographic exposure. 
     
     
         3 . The patterned structure of  claim 2 , wherein said first unexposed photoresist material has a first photosensitivity and said second unexposed photosensitive material has a second photosensitivity, and wherein said first photosensitivity is greater than said second photosensitivity. 
     
     
         4 . The patterned structure of  claim 3 , wherein said first unexposed photoresist material is a positive photoresist that becomes chemically less stable upon exposure. 
     
     
         5 . The patterned structure of  claim 4 , wherein said second unexposed photoresist material is another positive photoresist that becomes chemically less stable upon exposure. 
     
     
         6 . The patterned structure of  claim 1 , wherein a portion of said at least one exposed second photoresist portion does not underlie said at least one exposed first photoresist portion. 
     
     
         7 . The patterned structure of  claim 6 , wherein a portion of said at least one second photoresist portion does not underlie said at least one exposed first photoresist portion. 
     
     
         8 . The patterned structure of  claim 1 , wherein said at least one exposed second photoresist portion comprises a plurality of exposed second photoresist lines in a first one-dimensional array, and wherein said at least one second photoresist portion comprises a plurality of unexposed second photoresist lines in a second one-dimensional array. 
     
     
         9 . The patterned structure of  claim 8 , wherein each of said plurality of exposed second photoresist lines comprises:
 at least one narrow exposed second photoresist line portion having a first width and underlying said at least one second photoresist portion; and   at least one wide exposed second photoresist line portion having a second width and not underlying said at least one second photoresist portion.   
     
     
         10 . The patterned structure of  claim 9 , wherein said second width is greater than said first width. 
     
     
         11 . The patterned structure of  claim 1 , wherein said at least one exposed first photoresist portion comprises a plurality of exposed first photoresist lines in a one-dimensional array. 
     
     
         12 . The patterned structure of  claim 11 , wherein each of said plurality of exposed first photoresist lines has a constant width and a constant spacing from a neighboring exposed first photoresist line. 
     
     
         13 . The patterned structure of  claim 12 , wherein one of said at least one exposed second photoresist portion is located underneath said at least one exposed first photoresist portion and is a narrow portion of a line pattern, and another of said at least one exposed second photoresist portion is located outside an area of said at least one exposed first photoresist portion and is a wide portion of said line pattern. 
     
     
         14 . The patterned structure of  claim 13 , wherein a lengthwise direction of said plurality of exposed first photoresist lines is perpendicular to a lengthwise direction of said line pattern including said at least one exposed second photoresist portion. 
     
     
         15 . The patterned structure of  claim 1 , wherein said at least one exposed first photoresist portion comprises an exposed grey resist. 
     
     
         16 . A patterned structure comprising:
 at least one exposed second photoresist portion located on a substrate and laterally abutted by at least one second photoresist portion, wherein said at least one second photoresist portion comprises a second unexposed photosensitive material and said at least one exposed second photoresist portion comprises a second exposed photosensitive material, wherein said second exposed photoresist material is a material derived from said second unexposed photoresist material by lithographic exposure; and   at least one exposed first photoresist portion located directly on said at least one exposed second photoresist portion and said at least one second photoresist portion and comprising a first exposed photosensitive material, wherein one of said at least one exposed second photoresist portion is located underneath said at least one exposed first photoresist portion and is a narrow portion of a line pattern, and another of said at least one exposed second photoresist portion is located outside an area of said at least one exposed first photoresist portion and is a wide portion of said line pattern.   
     
     
         17 . The patterned structure of  claim 16 , wherein said first exposed photoresist material is a material derived from a first unexposed photoresist material by lithographic exposure. 
     
     
         18 . The patterned structure of  claim 16 , wherein a portion of said at least one exposed second photoresist portion does not underlie said at least one exposed first photoresist portion. 
     
     
         19 . The patterned structure of  claim 16 , wherein said at least one exposed first photoresist portion comprises a plurality of exposed first photoresist lines in a one-dimensional array. 
     
     
         20 . A patterned structure comprising:
 at least one exposed second photoresist portion located on a substrate and laterally abutted by at least one second photoresist portion, wherein said at least one second photoresist portion comprises a second unexposed photosensitive material and said at least one exposed second photoresist portion comprises a second exposed photosensitive material, wherein said second exposed photoresist material is a material derived from said second unexposed photoresist material by lithographic exposure; and   at least one exposed first photoresist portion located directly on said at least one exposed second photoresist portion and said at least one second photoresist portion and comprising a first exposed photosensitive material, wherein said first exposed photoresist material is a material derived from a first unexposed photoresist material by lithographic exposure, said at least one exposed first photoresist portion comprises a plurality of exposed first photoresist lines in a one-dimensional array, each of said plurality of exposed first photoresist lines has a constant width and a constant spacing from a neighboring exposed first photoresist line, one of said at least one exposed second photoresist portion is located underneath said at least one exposed first photoresist portion and is a narrow portion of a line pattern, and another of said at least one exposed second photoresist portion is located outside an area of said at least one exposed first photoresist portion and is a wide portion of said line pattern, and a lengthwise direction of said plurality of exposed first photoresist lines is perpendicular to a lengthwise direction of said line pattern including said at least one exposed second photoresist portion.