Development of scalable planar MEMS technology for low power operated ethanol sensor

Metal oxide-based gas sensors are known for operating at high temperatures, which results in high power consumption. This drawback limits their application in battery-operated devices as well as system on chip (SoC) applications. In this paper, the design, simulation, integrated circuit (IC)-compatible fabrication, and testing of an integrated microelectromechanical system (MEMS) micro-heater with a sensor platform using planar MEMS technology are presented. The micro-heater is integrated with titanium dioxide (TiO₂) and a nano-silicon (Si) heterostructure using a simple fabrication process. This heterostructure is tested in the presence of different analytes like ethanol, acetone, iso-propyl alcohol, xylene, and benzene. The sensor shows an optimum sensing response at 100 °C with a maximum response to ethanol vapors. In comparison to the crystalline Si, the power consumption of the nano-Si-based platform is almost half. The formation of the heterostructure, highest sensitivity to ethanol, and repeatable ppm level of ethanol sensing at a comparatively low operating temperature are reported. The results show the TiO₂/nano-Si integration with the MEMS micro-heater, and demonstrate the reduced power consumption of 18 mW by nano-Si, which is very small in comparison to what is consumed by crystalline Si. The temperature profiling carried out using an IR-camera ensures the uniform temperature of 100 °C over the suspended sensing structure. (paper)