Two blanket films, made of PMMA homopolymer (P4078-MMA) and PS homopolymer (P1758-S) purchased from Polymer Source Inc., Dorval, Quebec, Canada were used to evaluate the etching depth of each polymer and PMMA/PS etching selectivity. Number-average molecular weights of both PMMA and PS blanket films are 11,500. The two blanket films were spin coated from toluene solution (2 wt%) at 1000 rpm on silicon substrates to thicknesses of 100 nm. Three kinds of PS-b-PMMA fingerprint patterns (P8966-SMMA, P8533-SMMA, and P5539-SMMA) purchased from Polymer Source Inc.—with target full pitches of 25.5, 41.0, and 77.0 nm—were also deposited on substrates as described below, and the patterns were etched to form PS masks. The number-average molecular weights of PS/PMMA in each PS-b-PMMA pattern were for the 25.5-nm full-pitch pattern, for the 41.0-nm full-pitch pattern, and for the 77.0-nm full-pitch pattern. Before forming the PS-b-PMMA patterns, the silicon substrates were cleaned in a 7:3 mixture of sulfuric acid and hydrogen peroxide (piranha solution) at 80°C for 10 min and rinsed with deionized water. Hydroxyl-terminated PS-r-PMMA (P6469B-SMMAranOHT), purchased from Polymer Source Inc., were spin coated on the cleaned silicon substrates with toluene solution (0.5 wt%) at 2000 rpm. Then, the hydroxyl-terminated PS-r-PMMA was grafted onto the silicon substrates by annealing in vacuum at 170°C for 72 h. After annealing, the substrates were rinsed twice with toluene to remove any unreacted polymers, and PS-r-PMMA brush was formed on the substrates. Thin films of lamellar-forming PS-b-PMMA were coated on the PS-r-PMMA brush and annealed at 230°C for 6 h. Then, PS-b-PMMA fingerprint patterns were formed on the substrates.