Development of a soft UV-NIL step&repeat and lift-off process chain for high speed metal nanomesh fabrication

In this work, we present a fabrication procedure of metal nanomesh arrays with the newly developed nanoimprint resist mr-NIL212FC used in a bi-layer resist system for a lift-off process. We comparatively analyzed and evaluated nanomeshes fabricated with a freshly prepared h-PDMS/PDMS stamp and a stamp used 501 times. Therefore, we first performed a step&repeat imprint test run in a self-built low cost step&repeat UV-NIL setup. We inspected the imprint behavior of the stamp, the UV-transmission through the stamp as well as stamp lifetime and stamp degradation with regard to the possible changes of its surface roughness. The nanomesh fabrication process is characterized by a good lift-off performance, leading to a low defect density of <1.26 defects 100 µm^-2. Even after 501 imprints, only a negligible stamp degradation occurred without effecting the imprint performance. Likewise, the same holds true for the nanomeshes, which showed comparable low defect densities and feature sheet resistances of 3.54 ± 0.14 Ω/□ for the first and 3.48 ± 0.23 Ω/□ for the 501st nanomesh, respectively. AFM analyses further revealed that the maximum height of the roughness R_t changed over the course of the 501 imprints from 6.3 nm to 13.3 nm, representing <5% of the overall imprint height. In general, the mr-NIL212FC resist shows a good wettability and compatibility with standard h-PDMS/PDMS stamps, a fast curing behavior, a high replication fidelity, easy separation characteristics, and a very low diffusion of resist components into the stamp. The mr-NIL212FC resist allows exposure times as short as 2 s in the applied tool setup, enabling high throughput production. Moreover, all performed measurements indicate that a much higher number of imprints with one stamp seem possible.