Design and fabrication of very small MEMS microphone with silicon diaphragm supported by Z-shape arms using SOI wafer

This paper will focus on design, fabrication and characterization of a new MEMS capacitive microphone with the perforated diaphragm supported by Z-shape arms using SOI wafer. The aim is to fabricate a new microphone with the smallest size, simple and low cost. The novelty is making Z-shape arms around of diaphragm on SOI wafer using only a mask to decrease diaphragm stiffness and air damping and thus improve microphone performances. The fabricated structure has a diaphragm thickness of 5 mu m, a diaphragm size of 0.3 mm x 0.3 mm, and an air gap of 1 mu m. The results show that the pull-in voltage is 10.3 V, open circuit sensitivity of 2.46 mV/Pa, and resonance frequency of 60 kHz. The fabrication process uses minimal number of layers and masks due to using SOI wafer to reduce fabrication time and cost. The specific geometry of the proposed diaphragm causes the new fabricated microphone has low bias voltage, good sensitivity and smallest size compared with previous works.