Patent ID: 6918105

Claim:
A computer-implemented method for assigning phases to a plurality of light shifter polygons of a photolithographic mask through which light is to be transmitted to photolithographically pattern an area on a substrate, wherein the mask has a plurality of locations corresponding to a plurality of target features which are located between the shifter polygons, the method comprising: (A) selecting at least one shifter polygon from a pool P 1 formed by said plurality of light shifter polygons and forming a set SP 1 of all selected polygons; (B) removing from said pool P 1 all selected polygons that are added to said set SP 1 ; (C) adding at least one polygon from said set SP 1 to a group of polygons to be associated with a phase; (D) identifying a set TF 1 comprising at least one target feature of said plurality of target features that form a pool P 2 such that each target feature in said set TF 1 has a portion having an edge adjacent one of said at least one shifter polygon in said set SP 1 ; (E) determining a set SP 2 comprising at least one shifter polygon in said pool P 1 , such that for each shifter polygon in said set SP 2 at least one predetermined condition is satisfied; (F) removing from said pool P 1 all polygons that are determined to be in said set SP 2 ; and (G) adding all polygons in said set SP 2 to a group of polygons to be associated with a phase other than the phase used in a previous act of adding.