Chemically Tailored PS-b-PMMA Derivatives for Scalable High-Fidelity Sub-10-nm Directed Self-Assembly Patterning

Block copolymer (BCP) lithography has emerged as a promising solution for fabricating sub-10 nm patterns in semiconductor device manufacturing. In this study, we developed chemically modified BCPs, specifically polystyrene-block-[poly(glycidyl methacrylate)-random-poly(methyl methacrylate)] (PS-b-(PGMA-r-PMMA) or PS-b-PGM), incorporating 2,2,2-trifluoroethanethiol to create high-χ derivatives (PS-b-PGFM). These derivatives exhibit Flory–Huggins interaction parameters (χ) that are 3.5 to 4.6 times higher than those of PS-b-PMMA, enabling well-defined lamellar domains with spacings of less than 20 nm. A minimum domain size of 12.3 nm was achieved, and directed self-assembly (DSA) was employed to form defect-free line patterns with a half-pitch size of 7.6 nm, demonstrating excellent reproducibility and alignment.
Sequential living anionic polymerization and the thiol–epoxy reaction were used to synthesize PS-b-PGFM block copolymers with varying PGMA content (10–33 mol%) as PS-b-PMMA derivatives. We investigated the relationship between PGMA content, BCP phase-separation behavior, and the surface affinity of the PGFM segment, optimizing the primary structure to achieve ultrafine perpendicular lamellar structures through simple thermal annealing. Bulk films analyzed by SAXS and TEM revealed well-ordered lamellae with a minimum d-spacing of 12.4 nm. Effective χ values of 0.110, 0.133, and 0.142 were determined for PS-b-PGFMs containing 10, 22, and 30 mol% PGMA, respectively, at 200 °C. These thin films formed vertical lamellar structures, confirmed by tilted SEM analysis, with PS-b-PGFM10-22 achieving the smallest L0 of 12.3 nm.
Furthermore, an appropriate polymer was selected from the obtained BCPs and evaluated through directed self-assembly (DSA) experiments, resulting in the formation of 7.6 nm half-pitch line patterns with high reproducibility and alignment. The DSA process was also tested on 300 mm silicon wafers. By optimizing chemical guides and annealing conditions, defect-free sub-10 nm half-pitch line patterns without parallel structures were achieved. These polymers exhibited remarkable reproducibility, highlighting their potential for scalable semiconductor manufacturing.