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 infrared 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°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.