Patent ID: 8495528

Claim:
A method for generating a design for at least one mask for a lithographic process, said method comprising: a first step of selecting a set of bright evaluation points and a set of dark evaluation points in an exposure plane for a multiexposure lithographic process comprising a set of illumination sources and a set of basis components of candidate wavefronts for each source to be used in forming an image at said set of bright evaluation points and said set of dark evaluation points; a second step of generating a set of relationships between intensities of said set of bright evaluation points and said set of dark evaluation points and weightings of said set of basis components of candidate wavefronts; a third step of generating a primary objective function expressing a first merit quality for said intensities at said set of bright evaluation points and at said set of dark evaluation points and said weightings of said set of basis components, wherein constraint functions applied during said generating are functions of said weightings of said set of basis components of said candidate wavefronts; a fourth step of transforming said primary objective function and said constraint functions into a secondary objective function that does not include constraints; a fifth step of determining extrema solutions for said secondary objective function; a sixth step of expanding said extrema solutions so that bright points are covered by expanded extrema solutions without resorting to phase shift; a seventh step of generating an expression of said primary objective function by employing said extrema solutions as a new set of basis components; an eighth step of calculating an optimal wavefront by finding weights for said new set of basis components through minimizing said primary objective function; a ninth step of generating a design for at least one mask, wherein said at least one mask generates said optimal wavefront during exposure when illuminated by said illumination sources, wherein at least one step among said second, third, fourth, fifth, sixth, seventh, eighth, and ninth steps is performed employing a machine configured to run a program for performing each corresponding step.