The comparison of various strategies of setting up an OPC repair flow with respect to process window constraints

摘要

The optical proximity correction (OPC) designs a biased mask so as to ensure the after-development-inspection (ADI) contours could be on target. Meanwhile, the lithographic manufacture process is approaching the sub 28 nm technology node, imposing a tremendous challenge on OPC engineers. Even a well-tuned OPC recipe can render many off-target simulated contours for the most up-to-date chip designs; and these off-target contours indicate highly possible on wafer weak points. We have recently developed a high-performance repair flow that can automatically correct these OPC weak points based on the retargeting procedure. It is expected that one has to take both nominal and process window (PW) conditions into account to avoid potential on wafer weak points. For the contact holes, we require the nominal CD and PW CD be at least CD_(nom) and CD_(pw), respectively. In some cases, it could be difficult to satisfy both nominal and PW CD constraints which may pose conflicts to each other. In this work, various strategies have been used to accommodate such conflicts; for instance, one can release the nominal constraint or replace the PW CD constrain by the PW area constrain. We perform a systematic study on the various specifications of these constraints, in order to select the most optimal setup for the nominal and PW constraints. These optimized specifications may allow us to perform a highly efficient repair on a contact layer.