Fabrication of submicron-gap electrodes by silicon volume expansion for DNA-detection

In this paper, submicron-gap electrodes were fabricated by traditional IC technology. The principle involved is based on the silicon volume expansion in the transition from silicon (Si) to silicon dioxide (SiO ₂) during thermal oxidation. The micron-level silicon electrode gaps were first generated on the silicon wafer by the conventional photolithography followed by deep reactive ion etching process. The thermal oxidation was then conducted to induce silicon volume expansion. As a result, the gap distance can decrease from micron level to submicron or even nanometer level, which depends on the oxidation parameters. Subsequently, the electrical DNA sensor, which can detect the I-V variations during DNA hybridization, had been constructed with the interdigitated submicron-gap electrodes. The result shows that the sensitivity of as-fabricated electrodes with 600 nm gap width can reach 2.5 μA/nM. This method may enable the batch-production and low-cost DNA biosensors.