Patent ID: 7739649

Claim:
A nontransitory computer readable medium for producing a computer readable definition of a photolithographic mask that define a target pattern in a layer to be formed using the photolithographic mask, the nontransitory computer readable medium comprising: a source code segment for identifying a plurality of features in the target pattern to be defined using phase shifting, each of the plurality of features comprised of a plurality of edges; a source code segment for placing a plurality of shifter shapes in the computer readable definition of the photolithographic mask, the plurality of shifter shapes placed proximate to edges of the plurality of features, wherein the plurality of features includes a first feature having a first edge and a second edge, the first edge adjoining the second edge, and wherein the plurality of shifter shapes includes a first shifter shape placed on the first edge and a second shifter shape placed on the second edge, the first shifter shape and the second shifter shape separated by a minimum distance; a source code segment for assigning phase to the plurality of shifter shapes according to phase dependencies and costs to create a plurality of phase shifters; and a source code segment for refining the plurality of phase shifters.