Nanofabrication on 2D and 3D Topography via Positive‐Tone Direct‐Write Laser Lithography

Abstract

Direct laser writing (DLW) lithography using two‐photon absorption is a powerful technique mostly used for fabrication of complex structures in micro‐ and nanoscale, by photopolymerizing a negative‐tone resist. In contrast, in this study it is demonstrated that DLW is also well suited for fabricating nano‐ to microscale metallic structures using lift‐off and a positive‐tone photoresist. It is shown first that versatile, fast and large area fabrication is possible on flat two‐dimensional insulating substrates, and an expression for how the line width varies with the scanning speed is derived, with excellent agreement with the experiments. Even more interestingly, a unique application for the DLW lift‐off process is demonstrated, by fabricating sub‐micron scale metallic wiring on uneven substrates with sloping elevation changes as high as 20 µm. Such fabrication is practically impossible with more standard lithographic techniques.