High sensitivity and high S/N microphone achieved by PZT film with central-circle electrode design

Abstract

This study based on piezo-electric sensing principle to develop a high S/N ratio MEMS microphone. The patterned PZT and electrodes designed implemented above the clamped diaphragm to generate high stress concentration on PZT and Si bimorph diaphragm. The proposed central-circle electrode design can induce more charge than the edge-surrounded electrode design (served as the reference design). The proposed design also provides a smooth stress distribution across electrode to tolerate more process variation such as offset from double-side alignment and boundary change by DRIE undercut. The measured results demonstrate the S/N is about 64dB (reference design: 53dB) for the piezo-electric microphone.