Design and fabrication of high performance condenser microphone using C-slotted diaphragm

In this paper, we present a new design of MEMS condenser microphone using SOI wafer. To improve the performance of the microphone, a perforated diaphragm with C-shape slots has been designed. The aim is to achieve high sensitivity, low voltage and small size microphone with easy and low cost fabrication process. The structure has a diaphragm thickness of 5 µm, a diaphragm size of 0.38 mm × 0.38 mm. The novelty of this microphone relies on perforated diaphragm includes some C-shape slots to reduce the stiffness of diaphragm to decrease the bias voltage and increase the sensitivity. Moreover, the proposed microphone is fabricated on SOI wafer to minimize the number of masks, deposited layers and fabrication process. The new microphone can be fabricated using just one mask to pattern the proposed diaphragm. The deflection of the new diaphragm is increased 19.5 times rather than traditional clamped diaphragms under an equivalent acoustic pressure of 20 Pa. The results show that the pull-in voltage is 10.47 V, open circuit sensitivity of 3.16 mV/Pa and resonance frequency of 70 kHz. The new microphone has a better figure of merit rather than other MEMS condenser microphones.