Multiscale Fluidic Channels via Internal Oxidation and Oxide Etching of Self-Assembled Silicon-on-Nothing Structures

Abstract

This paper reports a novel fabrication method for multiscale fluidic channels ranging from sub-20 nm to a few $\mu \text{m}$ in their hydraulic diameters, ${D} _{\mathbf {h}}$ , exhibiting height-to-width ratio [or aspect ratio (AR)] close to unity only relying on internal oxidation and oxide etching of self-assembled silicon-on-nothing (SON) structures. We find that internal oxidation occurs uniformly along the longitudinal direction of the SON microchannels and time-controlled thermal oxidation can offer nanochannels with the minimum ${D} _{\mathbf {h}}$ of ~10 nm. Third, the enlarged circular microchannels with the maximum ${D} _{\mathbf {h}}$ of ~4500 nm are achieved through wet etching of internal silicon dioxide. The smallest nanochannel demonstrated exhibits the length-to-diameter ratio of ~60 000 and the ratio of the largest microchannel cross section to the smallest nanochannel cross section is ~200 000. [2019-0118]