Synthesis of block copolymer containing fluorine random block to control flory-huggins interaction parameter and improving etching selectivity

Abstract

Directed self-assembly of block copolymer is one of the most promising candidates for sub-10 nm scale lithography due to its cost effectiveness and outstanding pattern resolution. Howev-er, further improvements of pattern resolution over 10 nm and etching selectivity of Poly(styrene-b-methyl methacrylate) (PS-b-PMMA) block copolymer remain as critical chal-lenges. Here, we suggest a newly designed block copolymer, poly[(styrene-co-pentafluorostyrene)-b-methyl methacrylate], that can form nanoscale patterns with relatively improved line edge roughness, and line width roughness and a higher etching resistance com-pared to PS-b-PMMA. The block copolymer was synthesized by reversible addition-fragmentation chain-transfer polymerization copolymerized with pentafluorostyrene, func-tionalized monomer, which has hydrophobicity. The modified block copolymer showed in-creased pattern resolution than conventional PS-b-PMMA due to two times higher Flory-Huggins interaction parameter ($\chi$). Even though it had a high $\chi$ value, the polymer could form perpendicular lamellae morphology by short thermal annealing. Also, synthesized BCPs were vertically aligned on homo-PS brush. The BCP could form a high-aspect-ratio vertical lamellae structure over 90 nm thickness.