High sensitivity and low power consumption gas sensor using MEMS technology and thick sensing film

Thick films based on tin oxide are fabricated on Si substrate and their gas response characteristics for test gas are examined. Sensing materials are added Al ₂O ₃ based on SnO ₂. In general, sensing materials are deposited on alumina substrate because of easy process but this type of sensor has high power consumption. Two heater types using a micromechanical system (MEMS) are designed to reduce the power consumption and are simulated. The sensor consists of one heater, two temperature electrodes and one sensing electrode. Sensor dimensions are 8 mm × 8 mm × 0.5 mm, and sensing-film dimensions are 2.7 mm × 2.7 mm. Test gas is dimethylmethyl phosphonate (DMMP) gas that is the simulant gas of nerve agent, one of the chemical warfare agents. Sensitivities are measured with different amounts of Al ₂O ₃, with different operating temperatures and with different concentrations. High sensitivity is acquired by using thick sensing film, and low power consumption, 130 mW at 300 °C, is achieved by using the MEMS technology.