Roughness improvements with new high-chi block copolymers for EUV rectification directed self-assembly

The roughness control in extreme ultra-violet (EUV) lithography is a key factor for device performance, critical to smaller size line and space (L/S) patterning. The stochastic effects arising from broadly distributed resist molecules and inhomogeneous photon conversion in EUV lithography can be resolved using directed self-assembly (DSA) of higher Chi diblock copolymers. In this paper, we describe newly developed High-Chi block copolymers that can form equilibrium domain spacing (L0) as small as 12 nm. They are classified as carbon and silicon rich BCPs which show good DSA at 18 nm (5x multiplication), 24 nm (1:1) rectification, and 21, 22 nm (2x multiplication) using thermal annealing under appropriate underlayer patterns. An optimum etch condition produced a complete removal of polar block without line collapse. We demonstrate rectification of the EUV line & space (L/S) patterns to smoothen the patterned lines to 0.85 ± 0.01 nm and 1.06 ± 0.01 nm of line-width roughness (LWR) and line-edge roughness (LER), respectively. A comparison of 24 nm EUV rectification DSA of PS-b-PMMA and the new High-Chi BCP was performed, and the results are discussed.