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In this paper, an optical simulation-based lithography hotspot fix guidance generator and an automatic hotspot fix flow are proposed. We develop our aerial image simulation engine by enhancing the traditional sum of coherence system method. Subject to the shape changes, a strong correlation between the aerial image intensity difference maps of pre-optical proximity correction (OPC) and post-OPC schemes is found. We collect near a litho hotspot in a pre-OPC layout some fix actions that are local shape changes to optimize the optical intensity. Then, fix guidances will be selected from the collected fix actions by a heuristic algorithm and input to a router for fixing the hotspot. We integrate the fix guidance generation method with a commercial lithography hotspot detection tool to create an automatic post-route optical-simulation-embedded local fix (OSELF) flow and test with industry 65 nm designs. Compared with the commercial flow that uses only local fix, our method has a 1.4x-1.9x fix rate, similar run time, no new design rule check violation, and negligible circuit timing impacts. We also combine our OSELF algorithm with a rip-up and reroute engine, and test on the same designs. Compared to the commercial tool that uses a hybrid (local fix plus reroute) fix flow, our combined flow runs 1.7x-2.9x faster with 45-55% circuit timing impact. Both flows achieve a 100% hotspot fix rate.