Design and Simulation of Capacitive Z-axis MEMS Accelerometers using SU-8, PolySi, Si3N4, and SiC-based structural materials

Abstract

A comparative study of MEMS-based micro accelerometers with four different spring mechanism and four structural materials are presented in this paper. The serpentine spring design is used for the highly sensitive topographic structure after investigating various spring topography due to its reduced spring constant. The highly sensitive serpentine structure-based spring design is simulated for MEMS accelerometers with SU-8, PolySi, Si3N4, and SiC as primary structural materials. After UV exposure, the stiffness of the SU-8 polymer is considered to be varied and measured with the Nano-indentation technique, and the spring constant is calculated with the graphical method. Comparative study of different materials is shown by simulation using COMSOL Multiphysics 5.5. SU-8 being a polymer-based MEMS accelerometer with an acceleration sensitivity of ∼357nm/g, shows high sensitivity and cost-effectiveness, suitable for industry compared to other conventional materials. SU-8 MEMS can be integrated with Si-technology for CMOS-based post-processing circuitry. The stress analysis investigates the spring and structural reliability of the designed micro accelerometers. The computational results of designed accelerometers showed a linear response up to ±50 g of acceleration's input value. The design of SU-8 highly sensitive, serpentine spring, low-cost and simplistic process technology-based Z-axis accelerometer shows the resonant frequency of 1.4 kHz, which is suitable for tactual, and navigation applications.