Resist Properties of Thin Poly(methyl methacrylate) and Polystyrene Films Patterned by Thermal Nanoimprint Lithography for Au Electrodeposition

Abstract

Gold (Au) line patterns of 0.5 and 1 µm widths were fabricated on a silicon substrate covered with a Au thin film by thermal nanoimprint lithography with poly(methyl methacrylate) (PMMA) and polystyrene (PS), followed by Au electrodeposition with their thin films as resist masks. We described the differences in the fidelity of the deposited Au patterns for linewidth and linewidth roughness and differences in undesired Au deposition in the masked regions between thin PMMA and PS films. The linewidths of the convex deposited Au pattern were larger than those of the concave nanoimprinted polymer pattern, and the deviation from the polymer concave pattern in the case of PS was significantly smaller than that in the case of PMMA. The linewidth roughness of the Au lines deposited with a PMMA mask was markedly high owing to particle-like Au deposition in comparison with that deposited with a PS mask. Undesired Au deposition occurred even on electrode surfaces masked with the thin PMMA and PS films. It was considered from these results that the difference in the size accuracy of Au electrodeposition between PMMA and PS was responsible for the resistance in the oxygen dry-etching step of a residual layer during thermal nanoimprint lithography in addition to polymer water absorbability in Au electrodeposition.