Fabrication of Solid State Nanopore in Thin Silicon Membrane Using Low Cost Multistep Chemical Etching.

Muhammad Khan,John Williams

doi:10.3390/ma8115390

Abstract

Nanopore-based analysis is currently an area of great interest in many disciplines with the potential for exceptionally versatile applications in medicine. This work presents a novel step towards fabrication of a single solid-state nanopore (SSSN) in a thin silicon membrane. Silicon nanopores are realized using multistep processes on both sides of n-type silicon-on-insulator (SOI) <100> wafer with resistivity 1–4 Ω·cm. An electrochemical HF etch with low current density (0.47 mA/cm2) is employed to produce SSSN. Blue LED is considered to emit light in a narrow band region which facilitates the etching procedure in a unilateral direction. This helps in production of straight nanopores in n-type Si. Additionally, a variety of pore diameters are demonstrated using different HF concentrations. Atomic force microscopy is used to demonstrate the surface morphology of the fabricated pores in non-contact mode. Pore edges exhibit a pronounced rounded shape and can offer high stability to fluidic artificial lipid bilayer to study membrane proteins. Electrochemically-fabricated SSSN has excellent smoothness and potential applications in diagnostics and pharmaceutical research on transmembrane proteins and label free detection.

Highlights

Biological and solid-state nanopores represent the two major classes of nanopore technology
We report a new method to fabricate a single solid-state nanopore (SSSN) of diameter 180 ̆ 12 nm in a thin silicon membrane (n-type) with resistivity of 1–4 Ωcm
A detailed procedure and important parameters involved in fabrication of a single solid-state nanopore in a thin Si membrane are described in the experimental section

Summary

Introduction

Biological and solid-state nanopores represent the two major classes of nanopore technology. Burham et al [34] investigated the effect of the most commonly used alcohols: ethanol, methanol, and propanol mixed with HF, forming an aqueous electrolyte for electrochemical fabrication They claimed a PSi membrane with thickness less than 1 μm in n-type (0–100 Ωcm) and p-type (0–100 Ωcm) substrates with a current density of 25 mA/cm. These issues conclude that the sensing mechanism of a biological species might be unreliable in real-time measurements Such porous membranes with varying pore size are not compatible for single molecule detection schemes and a large surface area of PSi may not be an acceptable platform to study protein translocation, direct DNA sequencing, virus detection, filtration of cancer cells, and single ion channel recording at the molecular level. Atomic force microscopy is further used to demonstrate the surface topography of fabricated pores

Results and Discussion

Choice of Light and DC Biasing

Electrochemical HF Setup

Conclusions