Analysis of Temperature Stability and Change of Resonant Frequency of a Capacitive MEMS Accelerometer

Temperature stability is a very important factor that determines the performance and reliability of the MEMS accelerometer. A change in the temperature of the accelerometer will cause complicated coupled effects, in particular changes in the material properties, deformation, and thermo-mechanical stress, resulting in changes in the resonant frequency of the accelerometer. In this study, we investigate the effects of temperature changes on the resonant frequency of an accelerometer. The effects of material properties and deformation with temperature changes on the resonant frequency of the accelerometer were investigated by the simulation and experimental analysis. As the temperature was increased from 25 to 75 °C, the silicon structure and the accelerometer chip were deformed in a concave shape, and the amounts of warpage of the silicon structure and the accelerometer chip were 0.018 and 0.178 µm, respectively. The warpage was mainly caused by the thermal expansion mismatch of the materials. The suspension beam and moving comb structures were also deformed very slightly. As the temperature was increased from − 40 to 75 °C, the resonant frequency of the accelerometer decreased linearly from 1269 to 1193 Hz, indicating that the temperature drift of the resonant frequency is − 0.66 Hz/°C. In order to investigate the effects of deformation of the silicon structure on the resonant frequency, the numerical analysis of an accelerometer with identical top and bottom glass thicknesses was conducted. This accelerometer model showed almost zero warpage regardless of changes in the temperature. However, temperature drift of the resonant frequency of − 0.52 Hz/°C continued to occur. Therefore, the changes of Young’s modulus of the silicon with the temperature could be the main cause of the change in the resonant frequency. This study will present a design guideline and optimal parameters for the development of a robust MEMS accelerometer to minimize the effects of temperature changes.