Patent ID: 7440083

Claim:
A method to obtain an illumination source solution for illuminating at least one mask for printing a pattern defined by the at least one mask, comprising: supplying mask shapes and an allowable range of printed shapes; determining sample points; using a source pixelation, determining proportionalities between source intensities and sample point intensities, for individual ones of a plurality of focal planes; determining a maximum allowable intensity at dark sample points, and a minimum allowable intensity at bright sample points; constraining a first intensity parameter in each focal plane to a maximum intensity among sample points at dark boundaries of the shape range; constraining a second intensity parameter in each focal plane to a minimum intensity among sample points at bright boundaries of the shape range; constraining the first intensity parameter in each focal plane to a maximum intensity bound within a truncated focal range; constraining the second intensity parameter in each focal plane to a minimum intensity bound within the truncated focal range; and executing a focal range loop, comprising selecting an initial defocus limit; maximizing a difference between a sum of the bounded maximum intensities and a sum of the bounded minimum intensities; and iterating by increasing the defocus limit so long as the constraints are met, otherwise terminating the focal range loop and outputting a result that provides a maximum difference between the sum or the maximum intensities and the sum of the minimum intensities.