Fabrication of a dense array of tall nanostructures over a large sample area with sidewallprofile and tip sharpness control

Abstract

We report a simple but efficient nanofabrication method to create a dense (nanoscale pitch)array of silicon nanostructures (post and grate) of varying height and shape over a largesample area. By coupling interference lithography with deep reactive ion etching (DRIE)in one process flow, we achieved silicon nanostructures of excellent regularity,currently with a pitch (i.e., period) of 230 nm, and uniform coverage, currently over2 × 2 cm2. The new nanofabrication practice of coupling interference lithography with DRIE notonly simplified the nanofabrication process but also produced high-aspect-ratio(higher than 10) nanostructures. By regulating etching parameters, the nanoscopicscalloping problem typical in Bosch DRIE was not only controlled but also utilized torealize sophisticated sidewall profiles, such as tips with a pointed or a re-entrantprofile. We showed the tips could be further sharpened by thermal oxidation andsubsequent removal of the oxide. Well-defined nanostructures over a large area withcontrollable sidewall profiles and tip shapes open new application possibilitiesin areas beyond nanoelectronics, such as microfluidics and tissue engineering.