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Micromachined Thermoelectric Hydrogen Sensor of Double-Membrane Structure

We have prepared a noble micromachined gas sensor by combining two identical micro-hot plates on membranes fabricated by anisotropic wet etching of silicon substrate and a thermoelectric hydrogen sensor. The thermoelectric hydrogen sensor selectively detects the hydrogen gas working with the thermoelectric effect of SiGe thin film and the Pt-catalyzed exothermic reaction of hydrogen oxidation. The double-membrane structure thermally isolates two central and rectangular membranes from the rim of a room-temperature bulk substrate, minimizing offset voltage by keeping both membranes at the same temperature. The Pt catalyst as small as 1.5 ×1.5 mm2 builds up the temperature difference in the thermoelectric film by the oxidation of 1% hydrogen in air, producing an output voltage of 0.38 mV as a signal at an operating temperature of 100°C.