Image quality is one of the most worrisome obstacles faced by next-generation lithography. Nowadays, considerable effort is devoted to enhance the contrast, as well as understanding its impact on devices. This work involves weighting different wafer data points with a weighting function dependent on the Normal Image Log Sope (NILS). Using this approach, we can filter wrong information of the process and make the OPC model more accurate. Calibre Workbench is the platform used in this study: it has been proven to have excellent performance on 0.13-um, 90-nm, and 65-nm production and development models set-up. Leveraging its automatic optical-tuning function, we practiced the best weighting approach to achieve the most efficient and convergent tuning flow.

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