Patent ID: 7620930

Claim:
A computer-implemented method of generating a mask having optical proximity correction features disposed therein, said computer-implemented method comprising the steps of: (a) obtaining a desired target pattern having features to be imaged on a substrate; (b) determining a first focus setting to be utilized when imaging said mask; (c) determining a first interference map based on said target pattern and said first focus setting; (d) determining a first seeding site representing the optimal placement of an assist feature within said mask relative to a feature to be imaged on the basis of said first interference map; (e) selecting a second focus setting which represents a predefined amount of defocus relative to said first focus setting; (f) determining a second interference map based on said target pattern and said second focus setting; (g) determining a second seeding site representing the optimal placement of an assist feature within said mask relative to said feature to be imaged on the basis of said second interference map; and (h) generating an assist feature having a shape which encompasses both said first seeding site and said second seeding site, wherein steps (a)-(h) are performed using a computer system.