Patent ID: 8576377

Claim:
A method for configuring an illumination source of a lithographic apparatus, the method comprising: dividing the illumination source into pixel groups, each pixel group including one or more illumination source points; selecting an initial illumination shape to expose a pattern, the initial illumination shape formed with at least one pixel group; iteratively calculating a lithographic metric for a plurality of pixel groups, each iteration in said calculating performed for a change of state of one pixel group of said plurality of pixel groups, the change of the state of the one pixel group creating a modified illumination shape, the iteratively calculating comprising adding said one pixel group to the initial illumination shape or removing said one pixel group from the initial illumination shape to create the modified illumination shape, the modified illumination shape including a) the at least one pixel group from the initial illumination shape and said one pixel group in the illumination source or b) the at least one pixel group from said initial illumination shape without said one pixel group in the illumination source, subsequent to said adding or removing, calculating the lithographic metric using the modified illumination shape to determine whether said one pixel group should be added or removed; and adjusting the illumination shape based on the iterative results of calculations.