During optical proximity correction (OPC), layout edges or fragments are migrated to proper positions in order to minimize edge placement error (EPE). During this fragment migration, several factors other than EPE are a part of the cost function for optimal fragment displacement. Several factors are devised in favor of OPC stability, which can accommodate room for high mask error enhancement factor (MEEF), lack of process window, catastrophic pattern failure such as pinch/bridge and improper fragmentation. As technology nodes becomes finer, there are conflicts between OPC accuracy and stability, especially for metal layers. To address this, several techniques have been introduced, including target smoothing, process window-aware OPC, model-based re-targeting, and adaptive OPC.
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