A MEMS Capacitive Microphone Modelling for Integrated Circuits

In this paper, a model for MEMS capacitive microphone is presented for integrated circuits. The microphone has a diaphragm thickness of 1 μm, 0.5 × 0.5 mm2 dimension, and an air gap of 1.0 μm. Using the analytical and simulation results, the important features of MEMS capacitive microphone such as pull-in voltage and sensitivity are obtained 3.8V and 6.916 mV/Pa, respectively while there is no pressure on the diaphragm. The microphone also has a capacitance of 2.3 pF. Using the relation between the capacitance and pressure signal, a 3 ports model for the MEMS microphone is proposed. To bias the microphone, a 2.3 V DC and a 1 GΩ resistor is used. The voltage and current signal of the microphone is proportional to the applied pressure of the acoustic wave. A RC filter is added to circuit to eliminate the low band frequency (≤ 20 Hz) noises. The microphone shows good response to amplitude and frequency changes versus applied pressure signal.