Asymmetric halftone biasing for sub-grid pattern adjustment

Abstract

A technique is described, based on concepts of halftone printing, for controlling feature dimensions in a printed image at increments smaller than the smallest addressable unit of the template used to produce that image. Accordingly, photomasks may be fabricated to yield images with sizes differing from a nominal width by increments which are small fractions of the minimum template size or pixel size. A template fabricated according to this technique includes a feature having one or more edges, and a first array and a second array of shapes (protrusions or indentations) disposed on the edges. The first and second arrays have respective segmentation periods; the first and second segmentation periods are different. Each array is formed of a plurality of identical shapes repeating at every corresponding segmentation period, each shape having a predetermined length and a predetermined width. The shapes (protrusions or indentations) in the first array and the second array may have different lengths, in addition to the two arrays having different segmentation periods; a line feature on a template will thus appear asymmetric with respect to both the length and period of the shapes along the edges of the feature.