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In this paper we present the key enhancements incorporated in the new NXT platform and also share future development steps enabled by the platform. These innovations build on driving the system productivity while in parallel improving the overlay performance and at the same time minimizing the scanner grid differences between NXT-based ArF/ArFi/KrF and NXE-based EUV scanners. Both hardware as well as software improvements play an important role in improving cross-matching overlay performance. On the hardware side, changes have been introduced to key modules such as the projection lens and the reticle stage to better match to EUV layers. Furthermore, the new NXT platform introduces a more powerful wafer stage to support better overlay accuracy as well as improved productivity. Complementary software-based corrections are developed to further correct for grid imperfections. For instance to reduce the impact of DUV pellicle distortions, onscanner real-time corrections have been added to the scanner metrology control architecture. ‘Maximizing the number of good-wafers-per-day’ has been the guiding principle for the development of the new NXT platform. Apart from driving the scanner productivity along the traditional wafer-per-hour metric, advancements have been implemented to improve the operational efficiency of the scanner on production use-cases while also minimizing the time spent on required system maintenance. This all to maximize the effective scanner output under HVM conditions. The new NXT platform is currently being rolled out for the most advanced immersion and ArF scanners – the NXT:2050i and the NXT:1470. Going forward, it will support further productivity steps and improved overlay accuracy and EUV matching developments. The platform is also prepared to support KrF scanners in the near future, where especially the productivity will be stretched for this wavelength. Longer term this platform will serve as the stepping stone towards significantly higher wafers-per-day productivity levels and sub-nm overlay accuracy.
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