Modeling of Capacitive MEMS Microphone with Square Membrane or Plate Using Integral Method

An analytical approach describing the acoustic pressure field inside a thin layer of thermo-viscous fluid trapped between the square membrane or plate and planar backing electrode of the electrostatic receiver, which involves integral formulation, is presented. The use of integral formulation enables to choose between a model of membrane and plate easily and to avoid the limitations of the classical method whereby the acoustic field is expressed as a sum of eigenmodes coupled with modal expression of the diaphragm displacement. The analytically calculated pressure sensitivity of the receiver is compared to the numerically calculated one and the discrepancies are discussed.