Selective Surface Metallization of Single Crystal Silicon Nanowires via Stencil Lithography

Surface metallization of Silicon Nanowires (Si NWs) is a critical preparation technology for surface functionalization in biochemical sensing applications. Conventional metallization approaches rely on resist lift-off or non-selective protocols, which can lead to contamination and device damage. This work demonstrates a selective and resist-free surface metallization of suspended Si NW in a 3D device architecture via gold stencil lithography (SL). The approach involves control of the stencil-device gap via a thickness-controlled spacer, fabricated onto the stencil, to characterize and minimize geometrical blurring. The approach also prevents potential stencil-device contact-induced damage to suspended Si NW during SL. A significant improvement in spatial resolution for selective metallization onto NW is achieved compared to the state-of-the-art. Additionally, using the proposed approach with spacer thickness control, miniaturization of the stencil aperture dimensions to nanoscale raises the potential for selective metallization of Si NW down to sub-1 $\mu \mathrm{m}$ in-plane spatial resolution for highly sensitive biochemical sensor applications.