A MEMS AlN transducer array for use as a cochlear implant

A piezoelectric cantilever array was fabricated, for use as a cochlear implant. An array of 4.2μm thick aluminum nitride (AlN) bimorph cantilevers, laminated with platinum and mounted on a silicon backbone, are designed to transduce incident sound pressure waves into electrical current when submerged in ionic cochlear fluid. The ability to prescribe the desired geometry and to deposit high quality piezoelectric films are two key aspects crucial to the success of this design concept. A 3cm parylene - gold - parylene ribbon cable extends from the probe to an electrode bay, for external measurements of the transducer array response. The AlN film is measured to have a rocking curve of 0.94° full width half maximum (FWHM), a d₃₁ of 2.1 pm/V, and a dissipation factor of 0.002. The actuated response of a single cantilever element in air shows good agreement with model predictions.