Degree of Perfection and Pattern Uniformity in the Directed Assembly of Cylinder-Forming Block Copolymer on Chemically Patterned Surfaces

Thin films of cylinder-forming polystyrene-b-poly(methyl methacrylate) block copolymer (PS-b-PMMA) were self-assembled on two sets of surfaces homogeneously covered with random copolymer brush composed of PS and PMMA (P(S-r-MMA)), having styrene fractions, FSt, ranging from 0.57 to 1.0: one set that had been exposed to the lithographic materials and processes without having been patterned and one set that had not. The resulting self-assembled morphologies revealed that the lithographic process shifted the nonpreferential composition of the P(S-r-MMA) brush from FSt ∼ 0.70 to FSt ∼ 0.79. PS-b-PMMA films were then directed to assemble with density multiplication on chemical patterns made from P(S-r-MMA), in which the surface chemistry of the background region of the pattern after lithography ranged from weakly PMMA-preferential (WMP, FSt = 0.70) to nonpreferential (NP, FSt = 0.79) to weakly PS-preferential (WSP, FSt = 1.00). The extent of density multiplication ranged from 1:1 to 16:1. The assemblies were a...