US Patent RE40084 Optical proximity correction

Method for utilizing halftoning structures to manipulate the relative magnitudes of diffraction orders to ultimately construct the desired projected-image. At the resolution limit of the mask maker, this is especially useful for converting strongly shifted, no-0th-diffraction-order, equal-line-and-space chromeless phase edges to weak phase-shifters that have some 0th order. Halftoning creates an imbalance in the electric field between the shifted regions, and therefore results in the introduction of the 0th diffraction order.