Low-Power-Consumption Metal Oxide NO₂ Gas Sensor Based on Micro-Heater and Screen Printing Technology

An NO₂ micro gas sensor was fabricated based on a micro-heater using tin oxide nano-powders for effective gas detection and monitoring system with low power consumption and high sensitivity. The processes of the fabrication were acceptable to the conventional CMOS processes for massproduction. Semiconducting SnO₂ nano-powders were synthesized via the co-precipitation method; and to increase the sensitivity of the NO₂ gas rare metal dopants were added. In the structure of the micro-heater, the resistances of two semi-circular Pt heaters were connected to the spreader for thermal uniformity. The resistance of each heater becomes an electrically equal Wheatstonebridge, which was divided in half by the heat spreading structure. Based on the aforementioned design, a low-power-consumption micro-heater was fabricated using the CMOS-compatible MEMS processes. A bridge-type micro-heater based on the Si substrate was fabricated via surface micromachining. The NO₂ sensing properties of a screen-printed tin oxide thick film device were measured The micro gas sensors showed substantial sensitivity down to 0.5 ppm NO₂ at a low power consumption (34.2 mW).