Lithographic apparatus and device manufacturing method

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;
• calculating a plurality of responses for a plurality of changes in the illumination source, each of the plurality of changes effected by a change of state of a single pixel group, the calculating comprising
• adding said single pixel group to the initial illumination shape or removing said single pixel group from the initial illumination shape to create a modified illumination shape, the modified illumination shape including a) the at least one pixel group from the initial illumination shape and said single pixel group or b) the at least one pixel group from said initial illumination shape without said single pixel group,
• subsequent to said changing, calculating a response using the modified illumination shape to determine whether said single pixel group should be added or removed;
• and
• adjusting the illumination shape based on the plurality of responses.

A non-transitory computer product having machine executable instructions, the instructions being executable by a machine to perform 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 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 changing, 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.

A lithographic apparatus comprising:

• an illumination system configured to condition a beam of radiation;
• a substrate table configured to hold a substrate;
• a projection system configured to project a beam of radiation patterned by a patterning device onto a surface of the substrate;
• and
• a processor configured to perform 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 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 or b) the at least one pixel group from said initial illumination shape without said one pixel group,
• subsequent to said changing, 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.