First MEMS Microphone Based on Capacitive Transduction in Vacuum

This paper presents the first experimental results of a new MEMS microphone with in-vacuum capacitive transduction. The device is divided into a pressure-harvesting rigid piston in air, linked to a capacitive transducer enclosed in a vacuum cavity. In theory, this separation should lead to very low acoustical and mechanical noises, thereby increasing the overall microphone performance (estimated SNR>75 dB(A)). First wafer-level tests give a clear proof-of-concept of this new microphone design, with a resonance frequency of 19kHz and a measured sensitivity of $6\pm 0.5 \mathrm{fF}/\mathrm{Pa}$ .