Fabrication of Complex 3D Nanoimprint Mold by Using Acceleration Voltage Electron Beam Lithography

In this study, we focused on the fabrication of biomimetic structures using nanoimprint lithography (NIL). Biomimetic structures are an attractive approach to create functional products. Among the various biomimetic structures, we focused on rose petals for superhydrophobicity characteristics with high contact angles and the surface properties of the water droplets and shark skin for the reduction of fluid resistance. These bio-inspired molds were fabricated by electron beam lithography (EBL). Many of the biomimetic structures are micro- and nano-sized 3D structures; rose petals and shark skin also have fine-grained 3D structures. Dose modulated EBL is commonly used for the fabrication of 3D structures. On the other hand, our previous study revealed that precise depth control is possible by changing the acceleration voltage. Therefore, the 3D nanoimprint mold was fabricated using a combination of conventional dose modulated and acceleration voltage modulated EBL. As a result, bio-inspired 3D molds (rose petals and shark skin) were obtained. The depths of these molds could be controlled by the characteristics of the electron penetration depth. Using these molds, convex biomimetic structures were obtained by UV-NIL. In this study, the fabricated structures had steps. We believe that a smooth shape can be fabricated by using a various acceleration voltage. And we believe that this process, using acceleration voltage modulation EBL, can fabricate precise and complex nano-scale 3D mold structures.