10 nm 이하의 리소그래피를 위한 블록공중합체 나노템플레이트의 제작 및 응용
- 10 nm 이하의 리소그래피를 위한 블록공중합체 나노템플레이트의 제작 및 응용
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- Block copolymers are composed of two or more polymer chain attached at their ends by covalent bonds and self-assemble into periodic nanoscale patterns. The domain size and shape can be easily controlled by the use of specific molecular weight and volume fraction of each block. The potential technological application of various microstructures and particularly of those formed in the case of thin films could easily attract much attention due to the ease of forming structures within nanometer scale that is beyond the limit of micropatterning prepared via conventional photolithography. In this study, nanoporous polymer thin film with diameter down to 8.1 nm was introduced by virtue of neutral surface made from self-assembled monolayers (SAMs). Additionally, patterning of various nanostructures was introduced.
Nanotemplates with arrays of nanopores were fabricated from three kinds of asymmetric diblock copolymers, polystyrene-b-poly(methyl methacrylate) (PS-b-PMMA), through the optimized thickness and annealing condition. By utilizing the neutral surface of SAMs of 3-(p-methoxyphenyl)propyltrichlorosilane (MPTS), the cylindrical microdomains of PMMA of the asymmetric PS-b-PMMA diblock copolymer were oriented perpendicular to the surface due to the balanced interfacial interactions of the blocks with the surface. Cylindrical nanohole arrays with mean diameter of 8.1 nm and standard deviation of 1.2 nm were obtained for PS-b-PMMA block copolymer with total molecular weight of 39.2 kg/mol. The current result of 8 nm hole diameter is one of the smallest diameters ever reported from microphase separation on neutralized substrates.
SAMs of MPTS on a substrate with gold surface were also fabricated and were used to fabricate nanoporous polymeric template. Hydrophilicity of gold surface was significantly enhanced after oxygen plasma treatment, which facilitates to form the SAMs of MPTS on the gold surface. The cylindrical nanotemplates with diameter down to 9 nm were obtained on the gold substrates and have good ordering and versatility comparable to template on Si-based substrates. Graphoepitaxy which is the strategy for organizing domains of block copolymer on topologically or chemically patterned substrates is performed for the control of density of cylindrical nanohole arrays. Well aligned cylindrical nanodomains were prepared in the circle, triangle, and quadrangle patterns.
Dense, ordered arrays of metal nanodots with a controllable diameter of 8 to 19 nm were fabricated by block copolymer lithography based on the metal evaporation and conventional lift-off process. The metal nanodot arrays exhibit the same degree of order as the block copolymer templates. By the virtue of metal dot arrays as an etching mask, metal capped Si nanorod arrays with aspect ratios up to 4:1 were fabricated by plasma enhanced reactive ion etching.
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