Holistic litho-etch development to address patterning challenges towards high NA EUV

Abstract

EUV (extreme ultraviolet) lithography has been introduced in high volume manufacturing in 2019 and continuous improvements have allowed to push the lithographic performance to the limits of 0.33 NA single exposure. However, stochastic failures, pattern roughness and local critical dimension uniformity (LCDU) are still major challenges that need to be addressed to maintain node shrinkage and improve yield. Together with pitch downscaling, photoresist thickness is decreasing to prevent pattern collapse. A lower depth of focus is also expected with high NA EUV which might even thin further down the resist layer. Being able to transfer the patterns with good fidelity is therefore getting very challenging because the resist “etch budget” is becoming too small to prevent pattern break during plasma etch transfer. A co-optimization of lithography processes, underlayers coating and etch processes is essential to further support the EUV patterning extension. In this report, recently developed hardware and process solutions to stretch the limits of EUV patterning will be presented. The latest performance for both chemically amplified resists (CAR) and metal oxide resists (MOR) will be introduced, with a focus on defect mitigation, dose reduction strategies and CD stability.