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 - 7 . (canceled) 
     
     
         8 . One or more machine-readable storage media storing machine-executable instructions that when executed by a computer, cause the computer to perform a method, the method comprising:
 producing layout features comprising a number of edges having a first assigned edge class selected from a set of two or more different edge classes;   adding merge fill bridges between pairs of the edges assigned to the first edge class to temporarily join at least some of the layout features;   merging the layout features joined by the merge fill bridges, thereby producing merged layout features; and   assigning phases to the merged layout features, the phase assigning comprising treating each of the merged layout features as an individual target feature.   
     
     
         9 . The machine-readable storage media of  claim 8 , wherein the assigning phases comprises:
 adding phase assignment bridges between pairs of layout feature edges assigned to a second edge class; and   assigning different phases to layout features on opposite ends of the phase assignment bridged.   
     
     
         10 . The machine-readable storage media of  claim 8 , wherein the method further comprises assigning the edges the first assigned edge class because the edges are too close to add assist features in a targeted lithographic technology. 
     
     
         11 . The machine-readable storage media of  claim 9 , wherein the method further comprises adding assist features between pairs of edges assigned to the second edge class. 
     
     
         12 . The machine-readable storage media of  claim 8 , wherein the method further comprises:
 adding assist features between medium or far edges of at least one pair of the layout features, the medium or far edges not being assigned to the first edge class; and   trimming at least one of the added assist features to satisfy a manufacturing constraint.   
     
     
         13 . The machine-readable storage media of  claim 8 , further comprising generating mask data based on the layout features and the assigned phases, but the mask data not including data for the merge fill bridges or phase assignment bridges. 
     
     
         14 . A computer-implemented method of assigning phases to a plurality of layout features of a photolithographic design, the method comprising:
 by a computer,
 assigning a close edge class to edges of some of the layout features; 
 joining the close edges with one or more merge fill bridges; 
 merging layout features joined by the merge fill bridges into strips; 
 assigning phases to the layout features, the assigning comprising treating each of strips as an individual target feature. 
   
     
     
         15 . The method of  claim 14 , wherein the layout features merged into strips are contacts. 
     
     
         16 . The method of  claim 14 , wherein the close edge class is assigned to respective edges based at least in part on the layout features being included in a contact array. 
     
     
         17 . The method of  claim 14 , further comprising:
 assigning a medium edge class to at least edge of the layout feature edges not assigned to the close edge class;   inserting phase assignment bridges between medium class edges; and   assigning different phases to layout features on opposite ends of the phase assignment bridges.   
     
     
         18 . The method of  claim 17 , wherein at least one of the layout features includes a contact array, the method further comprising:
 assigning a far edge class to isolated edges around a perimeter of the contact array;   inserting assist features between isolated edges having the far edge class.   
     
     
         19 . The method of  claim 17 , further comprising inserting sub-resolution assist features into the layout features before the assigning the phases. 
     
     
         20 . The method of  claim 17 , further comprising storing data for the assigned phases in a computer-readable storage medium, the stored data not including data for the merge fill bridges. 
     
     
         21 . The method of  claim 17 , further comprising manufacturing an integrated circuit or photolithographic mask using layout data comprising the assigned phases. 
     
     
         22 . The method of  claim 17 , wherein the assigning the close edges in based on a spacing between at least two of the close edges. 
     
     
         23 . One or more machine-readable storage media storing machine-executable instructions that when executed by a computer, cause the computer to perform a method, the method comprising:
 assigning a close edge class to one or more layout feature edges for a photolithographic design, the close edge class being selected from a set of two or more different edge classes;   a step for adding merge fill bridges between pairs of close edge class edges, and;   a step for merging layout features joined by the merge fill bridges.   
     
     
         24 . The machine-readable storage media of  claim 23 , wherein the method further comprises:
 assigning a medium edge class or a far edge class to one more layout feature edges of the photolithographic design, the medium edge class edges and the far edge class edges not being assigned to the close edge class;   a step for adding bridge fill bridges between pairs of medium edge class edges; and   assigning opposite phases to layout features connected by the bridge fill bridges.   
     
     
         25 . The machine-readable storage media of  claim 24 , wherein the assigning opposite phases comprises assigning phases to both layout features for the photolithographic design and to sub-resolution assist features for the photolithographic design. 
     
     
         26 . The machine-readable storage media of  claim 24 , wherein the layout feature edges comprise edges for non-square contacts in the photolithographic design.