Design, Modeling and Simulation of MEMS Resonator for Humidity Sensor Application

Humidity sensor plays an important role in our daily life as well as industries. In order to have a compatible device for applications of relative humidity measurement, the humidity sensors must be made in small size, low power consumption, low cost, and high performance. Microelectromechanical systems (MEMS) humidity sensors are well developed and have high efficiency. However, it has problems such as high damping coefficient and low sensitivity. Thus, this research will focus on design, analytical modeling and simulation of the MEMS resonator sensor for humidity detection. Mathematical equations that model the behavior of the device and optimize it through finite element analysis (FEA) simulation to investigate device characteristics such as spring constant, resonant frequency, air damping, quality factor and mass sensitivity. The device will be designed based on standard PolyMUMPs process technology. Electrothermal actuation method will be used to actuate the device and capacitive sensing technique to measure the output voltage. The effect of changes in length and width of the beam on spring constant and resonance frequency are investigated. The spring constant is found to be decreasing when the length of the beam increases and increasing when the width of the beam increases. On the other hand, resonance frequency is found to be decreasing when the length increases and increasing when the width of the beam increases. The effect of air damping also has been studied. It is found that the damping coefficient decreases where the number of holes and radii of holes increases. Analytical and simulation results of frequencies showed good agreement within percentage difference of 0.04 -1.23%.