Electro-thermal simulations and modelling of micromachined gas sensor

Reliability of the membrane structure for micromachined-gas sensors is one of the main concerns in MEMS technology. The major source of this problem is the stress on the membrane. In this study, the use of SiO2/Si3N4/SiO2 stacked layers with optimized dimensions was found to reduce the stress on the membrane, hence improve the reliability. We have also used electro-thermal simulations with finite element analysis (FEA) to model the structural properties of the membrane in order to reduce the stress. The appropriate selection of materials and dimensions yielded maximum active area temperature of 530degreesC at the center of the membrane with a polysilicon as a heater element, less than 5V supply voltage, 40mW of power consumption, membrane edge temperature of 177degreesC and acceptable mechanical stress of 0.097GPa. Upon realizing the structure with the modeled parameters, micromachined-gas sensors could respond to many industry/environment application demands.