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EUV lithography has already introduced in high volume manufacturing and continuous improvements has allowed to resolve pitch 24nm line and space (L/S), pitch 32nm contact hole and pillar pattern with single exposure at even numerical aperture (NA) 0.33. However, pattern roughness, local critical dimension uniformity (LCDU) and process related defects are still major challenges with decreasing critical dimensions (CD). Pitch downscaling also require the use of thinner photoresist mask to prevent pattern collapse from high aspect ratios. Thinner photoresist mask is challenging for pattern transfer because the resist "etch budget" is becoming too small to prevent pattern break during plasma etch transfer. It is required to investigate a co-optimization of lithography processes, underlayers and etch processes to further EUV patterning extension. In this paper, our latest developed process solutions to extend the limits of EUV patterning will be reported. The advanced performance for metal oxide resists (MOR) will be introduced, with a focus on defect mitigation, dose reduction strategies and CD stability.
Okada et al. (Fri,) studied this question.