A new development algorithm to optimize scanner alignment sampling for cross-chuck overlay performance optimization

In a leading-edge high-volume manufacturing fab, lithographers focus on searching for a suitable alignment layout strategy to cover process-induced overlay variation. However, how to minimize scanner cross-chuck overlay impact also draws attention due to WPH loss from chuck dedication. In this paper we evaluate a novel algorithm to analyze lithography scanner process/metrology data and introduce a new KPI called "model accuracy" for alignment sampling layout strategy creation, which takes into account robustness index as wafer-to-wafer/chuck-to-chuck variation. Combined with simulated overlay performance, an optimal alignment layout strategy is recommended for a maximum coverage of cross-chuck overlay, which leads to maximum productivity.