Patent ID: 7173688

Claim:
For use in connection with a lithography tool, a method for calculating an intensity integral, comprising: (a) dividing an illumination slot into a first grid having a plurality of first grid points, wherein each first grid point is defined by a first and second direction coordinate; (b) superimposing a plurality of pupils on the first grid, wherein each pupil has a center represented by a respective one of the first grid point; (c) defining a plurality of second grids, each second grid having a plurality of second grid points, wherein each second grid point is defined by a third and fourth direction coordinate, and wherein the plurality of pupils maps to the plurality of second grids, one pupil per second grid, and a center of each second grid is coincident with the center of the pupil mapped to that second grid; and (d) discretizing the intensity integral using the results of steps (a), (b), and (c).