Patent ID: 7735052

Claim:
A computer-implemented method of identifying an extreme interaction pitch region when designing a mask pattern for transferring a lithographic pattern onto a substrate by use of a lithographic apparatus, said method comprising the steps of: (a) determining a first pitch between certain features in said mask pattern and a first illumination map of an illumination source of said lithographic apparatus, (b) determining an illumination intensity at an image plane of said lithographic apparatus corresponding to said first pitch of said certain features and said first illumination map, (c) repeating steps (a) and (b) after varying one or more of said first pitch and said first illumination map; (d) identifying one or more extreme interaction pitch regions based on a plurality of determined illumination intensities from step (c); and (e) adjusting the mask pattern based on the identified one or more extreme interaction pitch regions, wherein steps (a) to (e) are implemented by the computer.