Surface-micromachined MEMS acoustic sensor with bottom electrode anchors

A capacitive MEMS acoustic sensor with two sacrificial layers based on surface micromachining on a GaAs substrate is presented. This sensor has bottom electrode anchors fabricated using an initial sacrificial layer for the formation of a back chamber. The bottom anchors serve to eliminate the back side process of the wafer for a conventional back chamber because the chamber is implemented through substrate surface etching. The proposed circular-type microphone has a diameter of 1.0 mm and a gap height of 2 mu m. It shows a pull down voltage of 8.5 V and a total capacitance of 5.5 pF. Additionally, the MEMS microphone has a sensitivity of 0.09 mV/Pa at 1 kHz at a bias of 2 V.