Fabrication of Nano-Gap Electrodes by Using Electrochemical And Chemical Etching Technique for a Nano-Pore DNA/RNA Sequencer

Several experiment results on electronic transport at the single molecular were reported. In these experiments, one vital technique is to achieve an interface between individual molecules and macroscopic electrodes. At present, one of the main methods used for such investigations is based on scanning probe microscopy. Although this method has provided many important results, the sample does not represent real conditions, i.e. high vacuum. An alternative approach to study the electrical properties of single molecule is to use nano-gap electrodes, namely a pair of electrodes with a nanometer gap. By using this approach, single molecular samples are measured under conditions similar to those of real devices.

However, there are few reliable methods for fabricating metallic electrodes with a molecular-sized. A single molecule (nucleotide) of DNA is approximately 2 nm in size. It is beyond the resolution of conventional electron beam lithography. All of the techniques reported so far requires the usage of expensive equipments (e.g. EBL (Electron Beam Lithography) and TEB (Transmission electron Beam)) and requires a complex and evolved sample preparation.

In this paper we report a simple and controllable method to fabricate nano-gap electrodes by electrochemical and chemical etching techniques. A line of metal is initially patterned by using ordinary microlithography process at the width of 2 µm. The line is continuously etched until the line is discontinued at the desirable gap. We have been successfully fabricated < 10 nm gap of Au electrodes by using electrochemical etching. Meanwhile for the Cr electrode, we produced a controllable gap of < 5 nm has been achieve by the used of chemical etching. These nano-gap electrodes will be a part of the whole system called nanopore gene-sequencer. This system will introduce sensitive, selective, and rapid genes (DNA and RNA) sequencing device that can be integrated with CMOS devices.