Patent ID: 8108802

Claim:
A method for generating a desired set of diffracted waves using features of a lithographic mask for which a set of supported transmissions are chosen from a set of supported values, by the steps of: creating at a computer a representation of the mask as a set of polygonal elements, defining at least one constraint for the computer comprising a ratio of spatial frequencies in the representation takes on amplitude ratios of the desired set of diffracted waves, and using an optimization algorithm stored in a memory of the computer to adjust transmission discontinuities at edges of the polygonal elements to substantial equality with discontinuity values allowed by the set of supported transmissions while maintaining the at least one constraint, where the optimization algorithm comprises iterated steps, the iterated steps comprising: forming a 3D topographical representation from the polygonal elements, simulating the 3D topographical representation to calculate a Fourier transform of the transmission discontinuities at the edges of the polygonal elements, and calculating at the computer a compensating adjustment that cancels deviations of the Fourier transforms of the transmission discontinuities at the edges of the polygonal elements from the spatial frequency ratios, where the transmission discontinuities at the edges of the polygonal elements are adjusted based on the compensating adjustment, where the iterated steps are performed until the adjusted transmission discontinuities at the edges of the polygonal elements are substantial equal with the discontinuity values allowed by the set of supported transmissions.