Design and characterization of high sensitive MEMS capacitive microphone with fungous coupled diaphragm structure

Capacitive microphone is a device which can be used to transform the acoustic to electrical signal. Diaphragm is one of the most important parts of a microphone which has two main roles. First, it deflects, due to the pressure of the acoustic wave, and second, it can be considered as one of the plates of the capacitor. In this paper, a novel type of diaphragm is proposed which can increase the sensitivity. In normal diaphragms, deflection decreases the effective area of the capacitor and as a result sensitivity is also decreased. Since in the proposed fungous coupled diaphragm, the effective area is independent to the deflection, it has no negative effect on the sensitivity. The results show that the effective mechanical sensitivity of the proposed design is as much as three times bigger, in comparison to the typical diaphragms. The mechanical sensitivity in the coupled diaphragm microphone and the circular diaphragm microphone are and m/Pa, respectively. The frequency response of the proposed microphone is so high that it can be easily used in aerospace applications, which need the frequency as high as 100 kHz. The lumped element model is used to calculate the frequency response.