Effective pitch reduction of self-assembled lamellae by the use of (PS-<i>b</i>-PMMA)_<i>n</i> multiblock copolymers

Abstract The current directed self-assembly (DSA) process utilizes a diblock copolymer composed of polystyrene (PS) and polymethylmethacrylate (PMMA) as standard materials. However, domain spacing of the self-assembled PS- b -PMMA is limited to ∼20–30 nm due to weak segregation strength. In this study, we explore a potential to overcome this size limitation through a multiblock approach that has previously been demonstrated with (PS- b -PI) n . Specifically, we simulate the self-assembled morphology of the linear multiblock copolymer, (PS- b -PMMA) n , using the so-called theoretically informed coarse-grained model developed for symmetric PS- b -PMMA. The simulation results demonstrate that the lamella pitch of (PS- b -PMMA) n can be reduced by ∼20%–25% compared to that of diblock copolymer. This reduction is attributed to loop and bridge conformations of the multiblock copolymer chains. These findings indicate that (PS- b -PMMA) n could be advantageous for DSA, not only by enabling the size reduction, but also by potentially enhancing the guiding effects through physically cross-linked, self-assembled domains via bridged chains.