Monolithic fabrication of vertical silicon nanowire gas sensor with a top porous copper electrode using glancing angle deposition

Abstract

Vertical Si nanowire (SiNW) gas sensor with a top porous electrode (TPE) has been reported as a highly sensitive, small footprint, and mass-producible gas sensor platform. In this article, a monolithic fabrication process for a vertical SiNW gas sensor using glancing angle deposition (GLAD) was proposed as a simple, low-cost, and large-area fabrication method, and the performance of the fabricated vertical SiNW gas sensor was evaluated via relative humidity measurement. The 1,000 nm length vertical SiNWs were uniformly fabricated on a 4-inch silicon wafer via GLAD at an oblique angle of 85° and a substrate rotation speed of 5 rpm. A Cu TPE was also fabricated via sequential GLAD without substrate rotation to realize the wafer-level vertical gas sensor from which multiple 2 × 2 cm2 vertical SiNW gas sensors were obtained by dicing. To optimize the Cu TPE fabrication process, the effects of oblique angle and deposition thickness on the conductivity and porosity of the TPE were examined; subsequently, an oblique angle of 65° and a thickness of 100 nm were selected as the optimum conditions when considering humidity measurement sensitivity.