Highly flexible membrane systems for micromachined microphones - modeling and simulation

This paper presents a mechanical modeling of membrane systems applicable to micromachined microphones requiring a low stiffness constant. We have recently developed a single-chip electrodynamic microphone in a CMOS MEMS technology. The microphone consists of a suspended square membrane of 1.4mm side, 3µm thick and 10µg, and two concentric inductors. This suspended moving membrane is fixed to the substrate with 4 attachments arms. In order to achieve a desired flat frequency response characteristic, covering the entire acoustic band, several attachment designs are presented, studied and compared. These designs include crab-leg, meander, U-spring and serpentine forms. We have found that for comparable dimensions, the U-spring form presents the highest compliance and the meander type is the stiffest.