Micromachined piezoelectric microphones with in-plane directivity

Micromachined piezoelectric microphones with in-plane directivity are introduced. A beam rotates about center torsional pivots and is attached to piezoelectrically active end-springs. Rotation of the beam in response to sound pressure gradients produces spring deflections, which, in turn, produce an open-circuit voltage at the piezoelectric films. Prototypes are presented that contain a 20-μm-thick silicon beam and end-springs with 900-nm-thick chemical solution deposited lead zirconate titanate atop the surface of the end-springs. Acoustic directivity measurements are presented that confirm device functionality.