Resolution enhancing technology using phase assignment bridges

Abstract

In one embodiment, a spacing is determined for each edge of a number of features in a photolithographic design. The edges have at least a partially predictable layout. Based on the spacing and the predictable layout, a bridge structure is generated. Each bridge of the bridge structure connects one of the edges to an edge of a neighboring feature. Then, the features and the bridge structure are provided for a phase assignment. The phase assignment assigns features at opposite ends of each bridge in the bridge structure to opposite phases. In another embodiment, a sub-resolution assist feature (SRAF) is introduced for an edge of a feature and a bridge is generated from the feature to the SRAF. Then, the feature and the SRAF are assigned to opposite phases based on the relationship defined by the bridge.

1 . A method comprising: 
 determining a spacing for each of a plurality of edges comprising one or more features in a photolithographic design, said plurality of edges having at least a partially predictable layout;    generating a bridge structure for the plurality of edges based on the spacings and the predictable layout, each bridge of the bridge structure to connect one of the plurality of edges to an edge of a neighboring feature; and    providing the features and the bridge structure for a phase assignment, said phase assignment to assign features at opposite ends of each of said bridges to opposite phases.    
   
   
       2 . The method of  claim 1  wherein generating the bridge structure comprises: 
 categorizing at least one pair of the plurality of edges as near edges; and    filling a space between each pair of near edges with a bridge.    
   
   
       3 . The method of  claim 1  wherein generating the bridge structure comprises: 
 categorizing at least one pair of the plurality of edges as medium edges;    inserting a sub-resolution assist feature (SRAF) between each pair of medium edges; and    filling a space between each medium edge and its corresponding SRAF with a bridge.    
   
   
       4 . The method of  claim 1  wherein generating the bridge structure comprises: 
 categorizing a set of the plurality of edges as far edges;    inserting a sub-resolution assist feature (SRAF) for each far edge; and    filling a space extending from one or more of the set of far edges with a bridge.    
   
   
       5 . The method of  claim 4  wherein filling the space comprises: 
 identifying any of the SRAFs that are within a minimum separation distance from another feature;    increasing a separation distance to at least the minimum separation distance for any identified SRAFs by resizing, merging, and/or deleting the identified SRAFs as needed;    adding a bridge between any far edge and its corresponding SRAF where the corresponding SRAF still exists or was merged; and    adding a bridge between any pair of far edges for which both corresponding SRAFs were deleted.    
   
   
       6 . The method of  claim 1  wherein generating the bridge structure comprises: 
 introducing a sub-resolution assist feature (SRAF) for one of the plurality of edges having a particular spacing; and    connecting one of the bridges of the bridge structure between the edge having the particular spacing and the SRAF.    
   
   
       7 . The method of  claim 6  wherein generating the bridge structure further comprises: 
 repeating the introducing and connecting for a plurality of additional edges having the particular spacing.    
   
   
       8 . The method of  claim 6  wherein the particular spacing is a first particular spacing, and wherein generating the bridge structure further comprises: 
 repeating the introducing and connecting for a plurality of additional edges having a second particular spacing.    
   
   
       9 . The method of  claim 1  wherein generating the bridge structure comprises: 
 introducing a plurality of sub-resolution assist features (SRAFs), wherein particular ones of the neighboring features comprise the plurality of SRAFs.    
   
   
       10 . The method of  claim 9  wherein providing the features and the bridge structure comprises: 
 merging the plurality of features and the plurality of SRAFs to a target layer for the phase assignment; and    merging the bridge structure to a bridge layer for the phase assignment.    
   
   
       11 . The method of  claim 1  wherein the photolithographic design comprises a mask design for a contact layer of an integrated circuit design.  
   
   
       12 . The method of  claim 1  wherein the one or more features comprise one of a square feature, an array of square features, a rectangular feature, and an array of rectangular features.  
   
   
       13 . The method of  claim 1  wherein the bridge structure comprises a temporary design artifact representing an additional layer in an integrated circuit design.  
   
   
       14 . The method of  claim 1  wherein determining the spacing comprises: 
 measuring each of the spacings as a projection perpendicular from each of the plurality of edges to a neighboring edge or to a maximum projection distance.    
   
   
       15 . The method of  claim 1  wherein the one or more features comprise staggered sets of features having a shorter spacing between neighboring features in neighboring staggered sets than between neighboring features within each set, and wherein generating the bridge structure comprises: 
 merging each said staggered set into a strip feature; and    filling the bridges between neighboring strip features.    
   
   
       16 . The method of  claim 1  wherein the spacing for each of the plurality of edges comprises at least one of a perpendicular distance from a given edge, a length of a given edge, a horizontal orientation of a given edge, and a vertical orientation of a given edge.  
   
   
       17 . A method comprising: 
 introducing a sub-resolution assist feature (SRAF) for an edge of a feature in a photolithographic design;    generating a bridge for the feature to the SRAF, said bridge to define a relationship between the feature and the SRAF; and    providing the feature, the SRAF, and the bridge for a phase assignment, said phase assignment to assign the feature and the SRAF to opposite phases based on the relationship defined by the bridge.    
   
   
       18 . The method of  claim 17  wherein the SRAF comprises a square SRAF.  
   
   
       19 . The method of  claim 17  wherein the SRAF comprises a rectangular SRAF, the method further comprising: 
 resizing the rectangular SRAF into a square SRAF.    
   
   
       20 . The method of  claim 19  wherein resizing the rectangular SRAF comprises: 
 trimming both ends of the rectangular SRAF an equal amount.    
   
   
       21 - 41 . (canceled)