Design and Simulation of Electro-fabricated MEMS Microhotplate for Gas Sensor Applications

Abstract

In this paper, we present the simulation results of a new MEMS micro-hotplate design for gas sensor applications. The structure is designed to be fabricated on a glass substrate by the low cost process including physical vapor deposition, photolithography, electroplating, and photoresist-sacrificed process. The electro-thermo-mechanical behaviors of the proposed structure have been simulated by CoventorWareTM. In the simulation, the effects of thickness of the NiCr heater layer temperature, mechanical deflection, stress, and power consumption are evaluated. The 3D simulation on results show that the temperature, displacement, stress and current density are pronounced at the center of the beam as desired. At the nominal sensor temperature of ∼400 °C, the power consumption and Mises stress are greatly reduced from 126 to 7 mW and 1280 to 472 MPa as the thickness decreases from 5 to 0.25 µm. In contrast, the compressive beam deflection is not monotonically increased as thickness increases and it is maximum at the thickness of ∼0.5 µm. Therefore, the simulation results indicate that the proposed design with 0.25 m-thick NiCr heater requires very low power consumption of 7 mW with low stress suitable and acceptable membrane deflection for gas sensor applications.