US Patent 11704471 Three-dimensional mask simulations based on feature images

A layout geometry of a lithographic mask is received. The layout geometry is partitioned into feature images, for example as selected from a library. The library contains predefined feature images and their corresponding precalculated mask 3D (M3D) filters. The M3D filter for a feature image represents the electromagnetic scattering effect of that feature image for a given source illumination. The mask function contribution from each of the feature images is calculated by convolving the feature image with its corresponding M3D filter. The mask function contributions are combined to determine a mask function for the lithographic mask illuminated by the source illumination.