Abstract: A correction for photolithography masks used in semiconductor and micro electromechanical systems is described. The correction is based on process windows. In one example, the invention includes evaluating a segment of an idealized photolithography mask at a plurality of different possible process variable values to estimate a corresponding plurality of different photoresist edge positions, comparing the estimated edge positions to a minimum critical dimension, and moving the segment on the idealized photolithography mask if the estimated edge positions do not satisfy the minimum critical dimension.