MEMS based metal oxide semiconductor carbon dioxide gas sensor

This paper describes the design and development of low power Micro Electro Mechanical Systems (MEMS) microheater and metal oxide semiconductor CO2 sensor. To achieve low power, suspended plasma enhanced chemical vapour deposited SiO2 diaphragm is used. BaTiO3-CuO is considered as metal oxide doped with 1% Ag and will be used as a sensing material to sense the CO2 gas. To get the required temperature for the sensing film, three different metals namely, Platinum (Pt), Titanium (Ti) and Tungsten (W) are simulated by using COMSOL Multiphysics 5.6. The proposed microheater structure is shown to have a good temperature consistency throughout the heater's active region while consuming low power. The microheater geometry of 100 μm × 100 μm with its electro-thermal temperature results is presented here. For an applied voltage, we report a maximum average temperature of Pt i.e. ∼99.51%, Ti ∼ 97.12% and W ∼ 89.78% for 300 °C respectively. Fabrication of CO2 sensor along with MEMS microheater had been designed and demonstrated. Energy consumed by the proposed platinum microheater geometry is 4.8 mW at 250 °C and 5.8 mW at 300 °C. The sensitivity characteristic is based on resistance sensing which has been found to be 21% for 400 ppm CO2 gas concentration and 70% for 1000 ppm. Comparatively capacitive based sensitivity is found to be ~54% for 400 ppm and 95% for 1000 ppm.