A new method to increase MEMS microphone sensitivity using small circular diaphragm with fixed center

摘要

This article presents a MEMS (micro-electromechanical systems) silicon condenser microphone with high sensitivity using a new method and circular diaphragm with fixed center. The proposed microphone is designed and simulated by minimizing the size and mechanical strength. In the proposed microphone in order to pass the air through the air gap, the diaphragm is designed with holes. Therefore, the sound attenuation in the microphone is reduced. The diaphragm diameter is 400 mu m which is lower than MEMS conventional condenser microphone. First, a mechanical analysis is performed on the microphone diagram to obtain the pull-in voltage. The pull-in voltage of the proposed circular microphone is 19 V and the applied bias voltage is around 60% of pull-in voltage (11 V). According to simulation results using COMSOL software, the sensitivity of new microphone is above -25 dB, in hearing range (between 20 Hz and 20 kHz) and the maximum acoustic pressure level of 100 Pa was approved. The first resonance frequency of microphone is 70 kHz that is out of hearing rage. Compared with previous works, the proposed microphone with the lower supply voltage has better frequency performance and more sensitivity to sense the sound.