Patent ID: 8566757

Claim:
An apparatus for defining a computer readable definition of a photolithographic mask of a target pattern in a layer of material of an integrated circuit, the target pattern comprised of a plurality of features, the apparatus comprising: means for defining a maximum shifter area around the plurality of features in the target pattern; means for placing shifter shapes in the computer readable definition of the photolithographic mask, the shifter shapes placed within the maximum shifter area such that the shifter shapes run along edges of the plurality of features, including at least one feature having varying width, and such that space is left between adjacent shifter shapes to admit a cut, and wherein said at least one feature has a plurality of sides with no other features of the plurality of features between said plurality of sides and a nearest border of the maximum shifter area; means for assigning phase to the plurality of shifter shapes according to phase dependencies and costs; means for refining the shifter shapes; and means for outputting the computer readable definition of the photolithographic mask including the plurality of shifter shapes.