Design, analysis, and modelling of a MEMS capacitive microphone for integration into CMOS circuits

摘要

A MEMS capacitive microphone with high mechanical sensitivity is presented. 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 results from analysis and simulation, important features of MEMS capacitive microphone such as pull-in voltage, sensitivity and resonance frequency are respectively obtained as 3.8v, −43dbv/Pa, and 74 kHz. A model for this MEMS capacitive microphone is provided by using the relationship between capacitance of microphone and exerted pressure of acoustic wave. To study the accuracy of model, it is simulated in an RC circuit. The results from the simulations show that the proposed model has similar functions as a variable capacitor structure. Simulations show that voltage signal in steady state operates according to exerted pressure and has swing around the bias point of microphone (2.3 V).