| Performance limits of micromachined piezoelectric microphones are examined theoretically and experimentally. The various sources of microphone noise are combined to form a model for the signal-to-noise ratio, and this model is used to generate design rules for piezoelectric microphones. The piezoelectric constitutive equations, classical plate equations, and a model of residual-stress effects are combined to describe microphone sensitivity. An acoustic model for the packaged piezoelectric microphones is also presented.;The control of residual stress in these clamped-clamped, laminated micromachined microphones by using compensating layers of compressive and tensile residual stress is investigated. In order to maximize microphone sensitivity, highly compressively stressed (;Using residual-stress compensation, an IC-processed piezoelectric microphone with on-chip, large-scale-integrated (LSI) CMOS circuits has been designed, fabricated, and tested in a joint, interactive process between a commercial CMOS foundry and a university micromachining facility. The 2500 x 2500 x 3.5 ;A micromachined piezoelectric microphone with an electrothermally tunable resonant frequency ;These piezoelectric microphone designs are compared and contrasted with concurrent micromachined-microphone research around the world in order to suggest directions for future research. |
