Directed self-assembly (DSA) was investigated on self-assembled monolayers (SAMs) of 6-(4-nitrophenoxy) hexane-1-thiol (NPHT), which were chemically modified by electron beam (EB) irradiation. By irradiating a responsive interfacial surface, the orientation and selective patterning of block copolymer domains could be achieved. We demonstrated that spatially-selective lamellar orientation of polystyrene-block-poly(methyl methacrylate) (PS-b-PMMA) could be induced via modification of an underlying SAM; for instance the conversion of an NO2 group to an NH2 group, induced by EB. The lamellar orientation of PS-b-PMMA was controlled by the change in the polarity of different regions of the SAM using EB lithography. The reductive treatment of SAM substrates plays a crucial role in the orientation of block copolymer. This method might greatly simplify block copolymer DSA processes as compared to the conventional multi-step chemo-epitaxy DSA process. By examining the lamellae orientation by EB, we found that the vertical orientation persists only for appropriate an irradiation dose and annealing temperature.
Hiroki Yamamoto, Guy Dawson, Takahiro Kozawa, and Alex P. G. Robinson, "Lamellar orientation of block copolymer using polarity switch of nitrophenyl self-assembled monolayer induced by electron beam," Proc. SPIE 10146, Advances in Patterning Materials and Processes XXXIV, 1014613 (Presented at SPIE Advanced Lithography: March 02, 2017; Published: 27 March 2017); https://doi.org/10.1117/12.2257953.
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