Fabrication of ultrahigh-aspect-ratio and periodic silicon nanopillar arrays using dislocation lithography and deep reactive-ion etching

The aspect ratio of nanostructures determines the mechanical sensitivities and responses, such as hydrodynamic and oscillating flow detection. Nanopillar arrays with ultrahigh aspect ratio were fabricated using deep reactive-ion etching (DRIE) based on the optimized parameters in this study. Wafer-scale nanopatterning was achieved using dislocation lithography with normal photolithography machine instead of e-beam or EUVL. The wafer-scale Cr masks with 300, 500, and 700 nm line arrays were successfully patterned on silicon, providing etching mask for the fabrication of nanopillar arrays with a high aspect ratio. The important limitation of undercut during DRIE was solved by modifying the process parameters and using double masks composed of photoresist and Cr. Finally, the aspect ratio of the silicon nanopillar array reached 120 with smooth surface and vertical sidewalls. The methodology can provide a general approach for fabricating complex 3D periodic nanostructures that can be applied to various fields of multifunctional detection applications to increase detection probability and sensitivity. (paper)