Hybrid Soft Replica Molds for Residual Layer-Free Patterning

In this study, we fabricated hybrid soft replica molds, excluding vacuum processes, to achieve residual-layer-free patterning. A proposed technique for enabling residual-layer-free patterning involves the use of molds with a UV-blocking metal layer over the top of the protrusion. However, the fabrication of this layer is time-consuming because of processes such as evaporation and etching. To address this issue, we propose a technique for the metallization of mold surfaces using UV nanoimprint lithography (NIL). This method involves sintering Ag ink onto a master mold and transferring it to a flexible film using a UV-transparent resin. Although traditional methods require controlled environments, our approach eliminates the need for vacuum processing; thus, rapid fabrication is possible. Furthermore, the flexibility of the soft replica molds allows for conformal contact with uneven substrates. We investigated the relationship between the Ag properties and the initial resist thickness and characterized it for residual-layer-free patterning. Consequently, patterns ranging from 100 to 2 µm in line/space and pillar dimensions were achieved with high dimensional accuracy. The hybrid soft replica molds, fabricated through a straightforward process, enabled a high throughput with residual layer-free patterning on hard substrates.