Thermal simulation of micro hotplate for multiple MEMS gas sensors

Abstract

With the development of MEMS technologies, research on MEMS gas sensor has emerged recently, and micro hotplate (MHP) is designed to provide suitable temperature for MEMS gas sensor. Heat properties of MHP profoundly influence the sensing properties of MEMS gas sensor. With the tendency of down-sizing in MEMS gas sensors, traditional temperature measurements such as contact measure and infrared temperature detection are no longer available due to relatively low resolution. In this work we used finite element analysis (FEA) to realize cost- and time-saving heat property evaluations for MEMS gas sensor with different MHP structures, and two indexes were introduced to describe heat properties of MHPs, such as area factor Q to describe area of isotherm and roundness of isotherm % R to evaluate isotherm shape. It is found that silicon oxide and silicon nitride suspension structures have different tendency in heat properties. The size of working area has important impacts on the heat properties of the MHP, and MHP with different working area may be applied in different applications. For instance, larger MHP with 1643 μm 2 /K area factor Q is suitable for noble metal catalytic gas sensing application, which requires uniform temperature distribution, and smaller MHP, which could reach 609 °C peak temperature at 30 mW power-consumption, is applied to IoT applications with battery power supply. Furthermore, some special characteristics of the heat distribution of MHP are found with adjusting the width of suspension beams. This work provides guidance on how to design proper sensing material shapes to utilize the performance of MHP and reduce heat loss.