Holistic patterning technology for DRAM 29nm pitch contact hole and pillar patterning

Abstract

Advanced lithography is transitioning to the high-NA EUV era with highly valuable technological advancements. We explored the limits of hexagonal contact hole and pillar patterning for memory device by utilizing holistic patterning technology of materials and process optimization, pattern rectification by directed self-assembly of block copolymer, and phase shift mask with low-n that can maximize patterning resolution in 29nm pitch design, which is the inflection point of high-NA EUV patterning. Focusing on pattern transfer, we were able to secure contact hole patterning, contact hole DSA rectification and pillar patterning in the 0.33NA process. It was also confirmed that phase shift mask can improve local CD uniformity by more than 23% compared to binary mask. In addition, we demonstrated dose and local CD uniformity in 0.55NA EUV resulting from changes in stochastic impact following the imaging contrast improvement of 0.55NA. This paper presents our latest patterning experience for 29nm pitch hexagonal contact hole and pillar array patterning and outlook for the future transition to the high-NA EUV process.