Design and Simulation of a Micro Hotplate Using COMSOL Multiphysics for MEMS Based Gas Sensor

Micro Hotplate (MHP) is one of the main components in micro-sensors, especially in gas sensors. A MHP should have low power consumption, low thermal mass and better temperature uniformity. The metal oxide gas sensors utilize the properties of surface adsorption to detect changes in resistance as a function of varying concentration of different gases. In order to detect to detect the resistive changes, the temperature must be in the requisite temperature range over the heater area. The sensitivity and response time of the sensor are dependent on the operating temperature of the MHP. Making proper design is of critical importance. In this paper, the geometric optimization of the heater structure to achieve high temperature uniformity by performing analysis using COMSOL Multiphysics 5.0, a Finite Element Analysis (FEA) package is done. Electro-Thermo-Mechanical(ETM) analysis is done to review the temperature and stress distribution over the MHP. Two dimensional structure of five different patterns of MHP, namely single Meander, double Meander, fan shape, rectangle shape, and porous structure are designed and simulations are done. Their temperature profiles are compared and porous structure is found to have low power consumption and better temperature uniformity. Three dimensional design and simulation of Meander and porous structures are also done and their temperature and displacement profiles are compared. The effect of various materials and thickness of heating element on the temperature, displacement, and power consumption of the MHP is evaluated. The porous structure is found to be best suitable for designing a gas sensor with high sensitivity and low power consumption. Then a gas sensor with high sensitivity is designed using this porous structure of MHP and ETM simulation is done.