Ultraminiature AlN diaphragm acoustic transducer

Abstract

Piezoelectric acoustic transducers consisting of a circular aluminum nitride and silicon nitride unimorph diaphragm and an encapsulated air-filled back cavity are reported. Analytical and finite element analysis models are used to design the transducer to achieve low minimum detectable pressure (MDP) within chosen size restrictions. A series of transducers with varying radii are fabricated using microelectromechanical systems (MEMS) techniques. Experimental results are reported for a transducer with a 175 lm radius on a 400 Â 500 Â 500 lm 3 die exhibiting structural resonances at 552 kHz in air and 133 kHz in water. The low-frequency (10 Hz-50 kHz) sensitivity is 1.87 lV/Pa (À114.5 dB re 1 V/Pa) in both air and water. The sensor has an MDP of 43.7 mPa/ ffiffiffiffiffiffi Hz p (67 dB SPL) at 100 Hz and 10.9 mPa/ ffiffiffiffiffiffi Hz p (55 dB SPL) at 1 kHz. This work contributes a set of design rules for MEMS piezoelectric diaphragm transducers that focuses on decreasing the MDP of the sensor through size, material properties, and residual stress considerations.

Micro-Electro-Mechanical Systems Microphones: A Brief Review Emphasizing Recent Advances in Audible Spectrum Applications

“…Piezoelectric MEMS microphones have attracted widespread attention due to the feature of passive devices (no power consumption), along with being quickly response, waterproof, and dustproof. However, the drawbacks of piezoelectric technology are apparent, where the primary issue is the compatibility with CMOS processes, and the dielectric losses of the piezoelectric material itself are considered the dominant source of noise compared to the input-referred noise of typical field-effect transistors and operational amplifiers [ 39 ]. The minimum detectable pressure is determined by the total input-referred noise integrated over a bandwidth of interest for a MEMS microphone [ 40 ], which is vital for performance in vocal applications.…”

Design, Fabrication, Characterization and Simulation of AlN PMUT for Sonar Imaging Applications

“…According to the principle of operation, micro-ultrasonic transducers can be classified into two types: capacitive micro-ultrasonic transducer (CMUT), and piezoelectric micro-ultrasonic transducer (PMUT) [3][4][5]. Compared to CMUTs, PMUTs have the advantages of a wide resonant frequency range coverage and independence on DC bias voltage [6,7]. , Yang D [8] et al proposed a piezoelectric AlN PMUT with a resonance frequency of 986 kHz, achieving an underwater receiving Disclaimer/Publisher's Note: The statements, opinions, and data contained in all publications are solely those of the individual author(s) and contributor(s) and not of MDPI and/or the editor(s).…”

Design, Fabrication, Characterization, and Simulation of AlN-Based Piezoelectric Micromachined Ultrasonic Transducer for Sonar Imaging Applications

“…According to the principle of operation, micro-ultrasonic transducers can be classified into two types: capacitive micro-ultrasonic transducers (CMUTs) and piezoelectric micro-ultrasonic transducers (PMUTs) [ 3 , 4 , 5 ]. Compared to CMUTs, PMUTs have the advantages of a wide resonant frequency range coverage and independence on DC bias voltage [ 6 , 7 ]. Yang D et al [ 8 ] proposed a piezoelectric AlN PMUT with a resonance frequency of 986 kHz, achieving an underwater receiving sensitivity of −178 dB (re: 1 V/μPa).…”