Patent ID: 7681171

Claim:
A computer-implemented method of generating complementary masks based on a target pattern having features to be imaged on a substrate, said complementary masks for use in a multiple-exposure lithographic imaging process, said method comprising the steps of defining an initial H-mask corresponding to said target pattern; defining an initial V-mask corresponding to said target pattern; identifying horizontal critical features in said H-mask, said horizontal critical features having a width which is less than a predetermined critical width; identifying vertical critical features in said V-mask, said vertical critical features having a width which is less than a predetermined critical width; assigning, by the computer, a first phase shift and a first percentage transmission to said horizontal critical features, said horizontal features to be formed in said H-mask so as to exhibit said first phase shift and said first percentage transmission; assigning, by the computer, a second phase shift and a second percentage transmission to said vertical critical features, said vertical features to be formed in said V-mask so as to exhibit said second phase shift and said second percentage transmission; determining a maximum allowable width for horizontal and vertical scattering bars using a simulation of the multiple-exposure lithographic imaging process such that no residual scattering bars appear in a final image resulting from the multiple-exposure process; applying horizontal scattering bars in said H-mask that extend parallel to edges of certain of said horizontal features; and applying vertical scattering bars in said V-mask that extend parallel to edges of certain of said vertical features.