Removal of residual layer by liquid transfer imprint lithography using roll-to-roll UV-NIL

Abstract

Nanoimprint lithography (NIL) is a very useful tool for the fabrication of nanoscale pattern devices. In particular, roll-to-roll (RtR) ultraviolet (UV) NIL offers a high-throughput transfer of nanoscale structures. However, RtR UV-NIL is a film based process, and so the residual layer tends to be thick. To control the residual layer thickness, we have attempted to implement RtR liquid transfer imprint lithography (LTIL). LTIL can remove excess resin by splitting the mold and substrate in the liquid phase. In this case, excess resin remains on the substrate, and the mold with a thinner resin is transferred to another target substrate and cured. This LTIL process is also possible during RtR motion by controlling the nip pressure and UV exposure timing. That is, the excess resin is split off from the feed film during one rotation, and UV exposure to cure the resin is carried out in the next rotation. We prepared a roll mold with adhered replica molds for this process, and we show that the residual thickness with LTIL is thinner than that without LTIL. In addition, heating and two rounds of LTIL are effective for obtaining a thin residual layer. A roll mold temperature of 70°C, feed speed of 1.8m/min, and two rounds of LTIL produced no-residual-layer transfer of nanoscale structures onto the film. RtR LTIL will contribute to the continuous, high-speed transfer of nanoscale patterns that have a thin residual layer.