Rectification of extreme ultraviolet lithography patterns by directed self-assembly: a roughness and defectivity study

Single-exposure extreme ultraviolet (EUV) lithography is quickly advancing as a replacement for argon fluoride immersion (ArFi)-based multiple patterning approaches for printing the most critical features in semiconductor devices. However, the dimensional scaling of EUV lithography patterns is hampered by stochastic effects, resulting in rough patterns and increased defectivity. A promising solution to mitigate these stochastic pattern variations is complementing top–down EUV lithography with bottom–up directed self-assembly (DSA) of block copolymers (BCPs). We investigated an EUV + DSA complementary process for the rectification of pitch 28-nm line/space (L/S) patterns on high-volume manufacturing compatible processing tools. We found that several DSA material and process parameters contribute to minimize the roughness of the rectified patterns. In particular, the BCP size and film thickness are the most critical parameters. In terms of defectivity, a combination of optical inspection and e-beam review pointed out that dislocations are not a major concern for EUV + DSA patterning due to the fast assembly kinetics. Instead, bridge and cluster defects are the main defect modes and minimum defectivity can be achieved by controlling the geometry of the guide pattern. Finally, the impact of pattern density multiplication by DSA was assessed by comparing the performance of the current EUV + DSA rectification process to the ArFi + DSA technology, both for generating a pitch 28 nm L/S pattern.