Patent ID: 6933083

Claim:
A method of designing a phase grating pattern, the method comprising: selecting an intended modified form of illumination that the phase grating is to provide in a photolithographic process; dividing an area, over which at least one portion of the phase grating pattern is to occupy, into a plurality of subcells; arbitrarily assigning one of a plurality of phase values to the subcells, whereby each of the subcells is provided with an initial one of the phase values, each of the phase values representing a respective phase shift that exposure light of the photolithographic process will undergo by being transmitted through a region of the phase pattern grating corresponding to the subcell; randomly selecting one of the subcells, and assigning one of the plurality of the phase values to the selected one of the subcells, and repeating said random selecting of respective ones of the subcells and said assigning of one of the phase values thereto such that a plurality of arrangements of phase values assigned to the subcells are produced; and evaluating each different one of the plurality of arrangements of phase values with respect to the propensity of a phase grating pattern, based on the arrangement of phase values, to produce a form of modified illumination corresponding to the intended modified form of illumination.