Nanowire Hydrogen Gas Sensor Employing CMOS Micro-hotplate

In this paper we present a novel hydrogen gas sensor comprising a high temperature SOI-MOS micro-hotplate and employing zinc oxide nanowires as the sensing material. The micro-hotplates were fabricated at a commercial SOI foundry followed by a backside deep reactive ion etch (DRIE) at a commercial MEMS foundry. Particular care was taken in designing the heater shape using a systematic parametric approach to achieve excellent temperature uniformity (within 1-2%) as shown by both simulations and experimental infra-red imaging results. Zinc oxide nanowires were grown on these devices and show promising responses to hydrogen with a response (R-a/R-h) of 50 at 100 ppm in argon. The devices possess a low D.C. power consumption of only 16 mW at 300 degrees C and, being CMOS compatible, offer low unit cost in high volumes and full circuit integration. We believe that these devices have potential for application as a sub-$1 hydrogen sensor with sub-1mW (pulsed mode) power consumption.