MEMS based metal oxide semiconductor carbon dioxide gas sensor

Abstract

This paper describes the design and development of low power Micro Electro Mechanical Systems (MEMS) microheater and metal oxide semiconductor CO 2 sensor. To achieve low power, suspended plasma enhanced chemical vapour deposited SiO 2 diaphragm is used. BaTiO 3 -CuO is considered as metal oxide doped with 1% Ag and will be used as a sensing material to sense the CO 2 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 CO 2 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 CO 2 gas concentration and 70% for 1000 ppm. Comparatively capacitive based sensitivity is found to be ~54% for 400 ppm and 95% for 1000 ppm. MOS Capacitive based Gas Sensor Model • Carbon dioxide has traditionally been recognized as one of the most serious atmospheric pollutants • Industries, Agriculture, Home safety and healthcare expands the marketplace for miniaturised, inexpensive gas sensors • Low power, reliable and cost-effective metal oxide semiconductor (MOS) based CO2 sensors are desirable • Sensitivity and Selectivity parameters play a very important role in designing gas sensors • Designing a microheater geometry is of great importance to achieve a preferred temperature uniformity and overall performance of a metal oxide semiconductor sensor