MEMS Capacitive Microphone with Dual-Anchored Membrane

In this paper, we proposed a MEMS capacitive microphone with a dual-anchored membrane. The proposed dual anchor could minimize the deviation of operating characteristics of the membrane according to the fabrication process variation. The membrane is connected and fixed to the back plate insulating silicon nitride structures instead to the sacrificial bottom insulating oxide layer so that its effective size and boundary conditions are not changed according to the process variation. The proposed dual-anchored MEMS microphone is fabricated by the conventional fabrication process without no additional process and mask. It has a sensing membrane of 500 μm diameter, an air gap of 2.0 μm and 12 dual anchors of 15 μm diameter. The resonant frequency and the pull-in voltage of the fabricated device is 36.3 ± 1.3 kHz and 6.55 ± 0.20 V, respectively.