A novel EPE measurement method for curvilinear pattern with Multigon format

In recent years, wafer process windows have become an issue in advanced node wafer lithography. Inverse lithography technology (ILT), a well-known method for obtaining the optimum process window for lithography, has not been practical due to the huge computational effort and complex pattern geometries required. However, in photomask manufacturing, curved OPC has attracted attention because the use of multibeams has made it possible to manufacture photomasks with complex curved patterns as well as conventional rectangular patterns. We believe that the best way to measure curved surface patterns is to utilise EPE (Edge Placement Error) measurement. Currently, we use Advantest measuring equipment and software to extract contours and EPE. However, our mask measurement ECO system for recipe creation, measurement and analysis does not yet fully support the Multigon format. Therefore, together with Advantest, we have developed an EPE measurement system that supports the Multigon format.