Characterization of a microelectromechanical microphone using the finite element method

Recent development and advances within numerical techniques and computers now enable the modeling, design, and optimization of many transducers using virtual prototypes. Here, we present such a virtual prototype of a Knowles SiSonicTM MEMS microphone. The virtual prototype is implemented using the finite element method with COMSOL Multiphysics and includes description of the electric, mechanic, and acoustic properties of the transducer. The acoustic description includes thermal and viscous losses explicitly solving the linearized continuity, Navier-Stokes, and energy equations, that is, thermoacoustics. The mechanics of the diaphragm are also modeled including electrostatic attraction forces and acoustic loads. A sub-model approach is used to model and lump the acoustic properties of the small perforations in the microphone backplate. The model has no free fitting parameters and results in the prediction of the frequency response, in the audible and ultrasound range, as well as other relevant characteristics. The model results show good agreement with measured data.