PHOTOLITHOGRAPHY WITH OPTICAL MASKS HAVING MORE TRANSPARENT FEATURES SURROUNDED BY LESS TRANSPARENT FEATURES

摘要

In photolithographic exposure, a feature (144) of an optical mask is projected onto a dark area (160). The light intensity inside the dark area is reduced by providing a non-printable clear cutout (410) inside the feature. The optical mask has the same optical pathlength outside the feature (144) adjacent to the entire outer boundary of the feature as at the cutout, the optical pathlength being measured along the optical mask's thickness.