Directed self-assembly of ABA triblock copolymer on chemical contrast pattern for sub-10nm nanofabrication by solvent annealing

We report a room temperature solvent annealing method for directed self-assembly of symmetric ABA triblock copolymer to form perpendicularly oriented lamellae on chemical patterns.~~The phase separation of ABA triblock copolymer is analogous to the counterpart AB diblock copolymer with half molecular weight. However, a much broader neutral window for surface wetting was found for the triblock. After exposing to the solvent vapor for a certain time, thin films of a symmetric poly (2-vinylpyridine-styrene-$b$-2-vinylpyridine) (P2VP-b-PS-$b$-P2VP) triblock copolymer self assemble, while the nanostructure is retained after rapid solvent evaporation. The perpendicular lamellae with sub-10nm feature size can be assembled with density multiplication on lithographically defined chemical pre-patterns to form registered periodic arrays of striped patterns with exacting precision in continuously varying period and spacing. Using block-selective infiltration (Atomic layer deposition with sequential long soaking/purge cycles), the alumina composite with high etch resistance was specifically incorporated into the polar and hydrophilic P2VP domains. The sub-10nm scale surface pattern was stransferred into Si substrates by plasma etching.