Fabrication and Electromechanical Characterization of Silicon Nanomechanical Membrane Flexure MEMS Sensor for Gas Sensing Applications

This article reports the development and characterization of a piezoresistive silicon MEMS nanomechanical membrane-flexure (NMF) sensor and its application for the detection of hydrogen gas. The electromechanical transduction of the NMF sensor is achieved with an integrated indium tin oxide (ITO) thin film piezoresistor with a high negative gauge factor of −430. The sensors are fabricated using a standard silicon-on-insulator (SOI)-based silicon MEMS process, facilitating batch production. A novel high-resolution hybrid optical-electromechanical method was used for the strain sensing study of the NMF sensor with in situ optical surface profiling for curvature measurement through white light interferometry. The optimized sensor design showed a deflection sensitivity of 2.76 ppm[nm]
$^{-{1}}$
. This work also reports the ability of the NMF sensor with signal conditioning circuit in detecting hydrogen gas in parts-per-million (ppm) concentration with good sensor response of 520 mV for 100 ppm and quick recovery using low background flow cell temperature supporting their suitability for reusable biochemical sensing applications demanding low detection limits.