Limiting current-type MEMS oxygen gas sensor integrated with micro-hotplate

Bulk yttria-stabilized zirconia (YSZ) oxygen detectors are widely used in areas such as the automotive industry. However, these detectors have high power consumption, which limits their application. To overcome this issue, herein, a novel limiting current type micro-electro-mechanical system (MEMS) oxygen sensor with low power consumption is developed. The MEMS oxygen gas sensor comprised a thinfilm YSZ oxygen gas sensing layer integrated on a microhotplate. The sensor volume was about one hundred times lower than that of conventional bulk YSZ oxygen gas sensors. The YSZ layer was prepared on a porous Pt layer in which oxygen gas was diffused through a spiral Ta2O5 underlayer. The YSZ oxygen sensing layer was heated by the micro-hotplate on the diaphragm structure. Because of the extremely low heat capacitance of the oxygen sensor and heater elements, the power consumption for sensing the oxygen gas was drastically decreased to 80 mW, approximately 1/30th of that of conventional bulk YSZ oxygen gas sensors. In addition, we successfully observed the proportional increase in limiting current with oxygen concentration at a sensitivity of 0.6 mu A/%, which is high enough to monitor atmospheric oxygen concentrations.