Mechanical properties of polymeric nanostructures fabricated through directed self-assembly of symmetric diblock and triblock copolymers
(Color online) Cross-sectional schematics of the directed assembly of a PS-PMMA block copolymer film on a lithographically defined chemical pattern followed by the selective removal of PMMA domains. A film of MSM-198 polymer is spin coated onto a chemical pattern (a) consisting of stripes of crosslinked SG-57 adjacent to stripes of oxygenated crosslinked SG-57. The block copolymer forms ordered lamellae (b) upon annealing that are oriented perpendicularly to the silicon substrate. A blanket synchrotron x-ray exposure induces chain scission events in the PMMA domains; the domains are selectively removed by development in acetic acid. The acetic acid is replaced with an ethanol/water solution (c) and subsequently dried (d). The pattern period (LS) is lithographically defined by the aerial image during EBL patterning. The pattern height (H), average spacing (S) between adjacent PS structures, average PS BW, and AR are defined as shown.
(Color online) Top-down SEM images of PS nanostructures fabricated from assembled block copolymer films. Each image is 750 nm by 750 nm in dimension. The structures range from 105 to 148 nm in height. The AR of the structures is given in the top right corner of each image. (a) Grating structures with periods ranging from 61 nm (LS/L0 = 1.24) to 76 nm (LS/L0 = 1.57) fabricated from MSM-198 triblock copolymer, (b) grating structures fabricated from SM-130 diblock copolymer with periods of 60 nm (LS/L0 = 1.01) and 66 nm (LS/L0 = 1.11), and (c) grating structures fabricated from SM-176 diblock copolymer with a period of 75 nm (LS/L0 = 0.99).
(Color online) CARC vs LS for PS nanostructures fabricated from (▪) MSM-198 triblock copolymer, (•) SM-130 diblock copolymer, and (▲) SM-176 diblock copolymer.
(Color online) Line width roughness (LWRσ) vs LS for PS nanostructures fabricated from (▪) MSM-198 triblock copolymer, (•) SM-130 diblock copolymer, and (▲) SM-176 diblock copolymer. The aspect ratio of each structure is equal to the critical aspect ratio of collapse. The errors bars represent one standard deviation.
(Color online) Apparent elastic modulus calculated from Tanaka model vs (a) LS and (b) LS/L0 for nanostructures fabricated from (▪) MSM-198 triblock copolymer, (•) SM-130 diblock copolymer, and (▲) SM-176 diblock copolymer.
(Color online) Apparent elastic modulus vs LS for PS nanostructures fabricated from MSM-198 triblock copolymer given by Tanaka model using (▪) average S and BW dimensions as model inputs, (•) S* = S − LWRσ and BW as model inputs, (▲) S and BW* = BW − LWRσ as model inputs, and (♦) S* = S − LWRσ and BW* = BW − LWRσ as model inputs.
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