Analysis of micromachined piezoelectric transducers operating in a flexural mode

Micromachined acoustic transducers have recently emerged in multiple application domains. Bulk acoustic resonators, for example, are extensively used as filters in the cellular handset industry. As another example, silicon capacitive microphones are rapidly replacing electret-condenser devices in consumer electronics platforms. Piezoelectric materials are commonly used in acoustic sensing applications. Combining micromaching with piezoelectric thin-films opens up possibilities of multiple new applications, in addition to the miniaturization of existing sensors. Applications may be as diverse as nondestructive test, acoustic imaging, vibration sensing, acceleration/force sensing, or electroacoustics. This paper presents analysis and measured behavior of micromachined devices constructed as a molybdenum, aluminum nitride, molybdenum trilayer and operating in a flexural mode. A theoretical analysis is derived using thin-plate bending theory. Finite-element simulation results of plate dynamics are examined, and sensitivities and linearity of manufactured devices are shown.