Piezoelectric microspeakers with high compressive ZnO film and floating electrode

Abstract

This paper describes micromachined piezoelectric microspeakers that can produce an audible signal supplied from an MP3 player through the use of 5V peak-to-peak signal amplification circuit modules. The Sound Pressure Level (SPL) of the fabricated microspeakers is higher than that of previous results even though the input voltage is reduced. The success of this technology is based upon two distinct features; one is the use of a high quality compressive ZnO thin film, the other is the implementation of a floating electrode beneath the piezoelectric ZnO film in order to induce more strain in the diaphragm of the microspeaker when two top electrodes are biased with different polarities. A high quality piezoelectric ZnO film is achieved using an Ar/O 2 gas ratio of 4:1, an R.F. power of 1,500W, a substrate temperature of 150°C, and a chamber pressure of 23mTorr. In this condition, the deposited ZnO film shows a compressive residual stress of −1.3GPa. The fabricated piezoelectric microspeakers were tested over a frequency range of 400Hz to 12kHz with a 5V peak-to-peak input signal, the maximum SPL of the fabricated microspeakers was shown to be more than 97.2dB at 7.1kHz with a distance of 3mm between the fabricated microspeakers and the reference microphone (B&K type 2,669 and 4,192L).

Piezoelectric Ceramics with High d33 Constants and Their Application to Film Speakers

“…In this regard, several complex electronic components have been replaced with piezoelectric materials. The development of acoustic components, which are essential parts of electronic products such as communication and information broadcasting equipment, is particularly gaining in attention [ 3 , 4 ]. Currently, commercialized dynamic speakers use magnetic diaphragms and coils, which limits their miniaturization; moreover, these current-driven systems consume significant amounts of power.…”

Magnetostrictive microelectromechanical loudspeaker

“…Active materials showing the piezoelectric effect have been utilized as MEMS-loudspeakers. [5][6][7][8][9] These materials (mostly PZT, ZnO, or AlN) are deposited and structured upon a passive membrane. An applied electric voltage leads to a geometric deformation which excites a movement of the membrane.…”

“…It is as straightforward as for piezoelectric membranes. [5][6][7][8][9] Furthermore, a simulation model is derived from the physical interrelationships. It combines the methods of lumped elements and finite elements.…”

Characterization and Modelling of Circular Piezoelectric Micro Speakers for Audio Acoustic Actuation

“…A different approach to micro speaker development is the piezoelectric type, as reported amongst others in [8][9][10][11][12]. Driven not only by applications in the audio field but most importantly by biomedical and underwater ultrasound applications and requirements, the piezoelectric micro ultrasonic transducer (pMUT) has been widely described in [13][14][15][16][17].…”