Thermal Nanoimprint of a Polystyrene and Poly(4-vinylpyridine) Double-Layer Thin Film and Visualization Determination of Its Internal Structure by Transmission Electron Microscopy

Abstract

In this research, we studied the morphological transformation of a poly(4-vinylpyridine), P4VP, thin film on a polyimide substrate after thermal nanoimprint and investigated its effect on electron beam (EB) exposure by atomic force microscopy. On the basis of the results, we designed a patterned double-layer thin film consisting of polystyrene, PSt, as the outermost inactive layer and P4VP as the underlying active layer for Cu electroless deposition. We studied how to prepare and confirm the integrity of a double-layer structure on the polyimide substrate after thermal nanoimprint. A P4VP thin film of 60 nm thickness started to be transformed by thermal nanoimprint at 80 C owing to a thin-film effect lowering the glass transition temperature (T g ¼ 137 C) of its bulk state. EB exposure caused P4VP crosslinking and resulted in the P4VP layer becoming insoluble in toluene and being hardly transformed by thermal nanoimprint even at 160 C. As a result, an outermost layer of PSt exhibiting a lower T g than P4VP was successfully prepared by spin coating and was transformed only by thermal nanoimprint. The designed internal structure of the double-layer thin film patterned by thermal nanoimprint was confirmed by transmission electron microscopy (TEM) as a cross-sectional image using HAuCl 4 and RuO 4 as stain reagents for P4VP and PSt, respectively.

Depth profiles of aluminum component in sequential infiltration synthesis-treated electron beam resist films analyzed by time-of-flight secondary ion mass spectrometry

“…31) We previously reported that thin film surfaces of PS and poly(4-vinylpyridine) could be transformed by thermal nanoimprinting at 80 °C which was lower than glass transition temperatures of 92 °C for bulk PS and 137 °C for bulk poly(4-vinylpyridiene). 45) The depth of transformed film surface was increased with an increase in molding temperature under a constant applied pressure. This suggests that polymers in a region from the outermost surface to the film inside showed a lowered glass transition temperature.…”

Chlorine-based inductively coupled plasma etching of GaAs wafer using tripodal paraffinic triptycene as an etching resist mask

“…TNIL was performed at 150 °C and a pressure of 20 MPa for 5 min using a nanoimprint system (Meisho Nanoimprinter NM-400). 24,25) Then, the mold was removed at 60 °C. The residual layer was removed by O 2 plasma using a reactive ion etching (RIE) system (Samco RIE-1).…”