Aluminum Nitride Ultrasonic Air-Coupled Actuator

Abstract

A piezoelectric micromachined ultrasonic radiator was developed using aluminum nitride (AlN) for air-coupled applications. A commercially proven CMOS-compatible fabrication process was leveraged to form the devices. The transducer design consists of a radially nonuniform circular composite diaphragm with an integrated layer of AlN between two annular electrodes. Included in the overall system design is a tunable package with back cavity depth control. A multiphysics model was developed that integrates the electrical, mechanical, and acoustic energy domains of the complete system using composite plate mechanics, lumped-element modeling, and linear acoustic theory. Acoustical, mechanical, and electrical characterization of the transducers was conducted, including acoustic far field, laser vibrometry, and electrical impedance measurements. The device characterization results showed poor quantitative match with the system-level model due to large uncertainties in film stress. However, a qualitative comparison between the device behavior and the system model with varying back cavity depth showed promising results. The overall device performance is comparable to those in previous works that utilized alternate piezoelectric films.[ 2010-0313]Index Terms-Aluminum nitride (AlN), diaphragm, microelectromechanical systems (MEMS), piezoelectric, ultrasonic.

Application Status of MEMS Technology in Marine Field

“…Therefore it was also used as a transducing material [19,20,21]. The use of aluminum nitride and PMNPT relaxor ferroelectric single crystal as transducing materials has always been one of the research directions for piezoelectric MEMS underwater acoustic sensors [22,23,24].…”

The electromechanical behavior of piezoelectric thin film composite diaphragms possessing in-plane stresses

“…In the design of microfabricated piezoelectric devices, the incremental displacement of figure 2(c) due to external loads is of primary importance, for example as an input to a predictive lumped element model [9,13,15,16,23]. In this work, incremental displacement is found from…”

“…The displacement response to both voltage and pressure loading is considered. Such a model may be used directly with the lumped element modeling technique [9,15,16,23] to predict linear dynamic behavior. A comparison of model predictions with experimental measurements of a MEMS microphone diaphragm [15,16] is also given.…”

Reducing parasitic effects of actuation and sensing schemes for piezoelectric microelectromechanical resonators

“…Tilmans work [9] that laid the foundations for developing equivalent electrical circuits of electro-$+" mechanical transducers and their interconnection to the outside world, Studies [10][11][12][13] where lumped $!" element-based modeling is used to predict the behavior of multiphysics microsensors integrating $#" piezoelectric active layers have been carried out.…”