High Performance Piezoelectric Microspeakers and Thin Speaker Array System

This paper reports on an improved piezoelectric microspeaker with a high sound pressure level of 90 dB, a total harmonic distortion of less than 15%, and coherence higher than 0.9. The fabricated Pb(Zr,Ti)O₃ (PZT) microspeakers have a thickness of only 1 mm including the speaker frame and an active area of 18 mm×20 mm. To achieve higher sound pressure and lower distortion, the PZT piezoelectric microspeaker has a well‐designed speaker frame and a piezoelectric diaphragm consisting of a tilted PZT membrane and silicone buffer layer. From the simulation and measurement results, we confirmed that the silicon buffer layer can lower the first resonant frequency, which enhances the microspeaker's sound pressure at a low frequency range and can also reduce useless distortion generated by the harmonics. The fabricated PZT piezoelectric microspeakers are implemented on a multichannel speaker array system for personal acoustical space generation. The output sound pressure at a 30 cm distance away from the center of the speaker line array is 15 dB higher than the sound pressure at the neighboring region 30 degrees from the vertical axis.     

基于高压应力的氮化铝MEMS压电微扬声器

基于微电子和微机械加工工艺制备了一类氮化铝AlN(Aluminum Nitride)压电微扬声器.研究了器件薄膜残余应力对器件性能的影响,采用带有高残余压应力的高c-轴取向氮化铝薄膜分别作为器件压电层和支撑层增大微扬声器的输出声压,同时利用工艺手段控制整体薄膜残余应力进一步增大器件输出声压.该微扬声器的悬膜直径仅为1.35 mm,厚度为0.95μm.在开放空间内,采用声压级检测仪对该微扬声器的输出声压级SPL(Sound Pressure Level)进行扫频测试(频率范围:0.5 kHz～20 kHz).测得单个微扬声器在距离为10 mm处,20 Vpp驱动电压下最大输出声压级约为75 dB.测试结果显示该氮化铝压电微扬声器在耳机、智能手机和可穿戴设备等方面都具有潜在的应用前景.     

MICROMACHINED PIEZOELECTRIC MICROSPEAKERS FABRICATED WITH HIGH QUALITY ALN THIN FILM

ABSTRACT

This paper describes the micromachined piezoelectric microspeakers that can produce the audible signal with 20 V peak-to-peak input voltages. The diaphragm size is 4 × 4 mm² and the thickness of diaphragm is around 1 micron meter except partially etched piezoelectric area. The maximum sound output pressure of the microspeaker is even higher than ever before with a small diaphragm in high frequency range around 10 kHz. This successful result bases upon using high quality AlN thin film. The deposited AlN thin film shows c-axis oriented columnar structure and very fine grains. The highest SPL (Sound Pressure Level) measured from 300 Hz to 12 kHz shows about 100 dB around 10 kHz in case of circular type microspeaker and about 76 dB in case of cross type, respectively.     

蠕变效应对微型扬声器小信号参数建模的影响

大部分微型扬声器在低频时存在着蠕变效应。通过电力声类比建立了微型扬声器的小信号模型,分析了微型扬声器小信号参数与普通扬声器的差异。引入支撑部分的蠕变效应,采用标准线性固态蠕变模型对支撑系统顺性进行改进,比较了传统的力顺模型和两种蠕变模型。讨论了蠕变对小信号参数建模的影响,以及特殊的结构对振动和声学特性的影响。取得的结果具有一定的实用价值。     

MICRO ACOUSTIC DEVICES USING PIEZOELECTRIC FILMS

ABSTRACT

A novel PZT based micro acoustic device with the diaphragms clamped on all four edges has been studied. It can be used both as microphone and microspeaker. Compared with other piezoelectric micro acoustic devices, PZT based device has higher sensitivity for microphone and larger output acoustic pressure for microspeaker. The microfabrication process flow of this device is simple, and the transducer has excellent performance, miniature size and high reliability. The micro acoustic devices could be widely used in various practical audio frequencies and ultrasonic systems.     

DIRECTIVITY OPTIMIZATION OF PZT BASED MICROSPEAKER ARRAY

ABSTRACT

In this paper, the directivity is optimized for a PZT based microspeaker array. The SiO₂/Pt/Pb(Zr,Ti)O₃/Pt/Ti/SiO₂ multimorph structure has been designed and fabricated to be the microspeaker cell using silicon based micro-machining process. The membrane size of the single transducer cell is 1000× 1000× 2.5 μ m³, and the main resonance frequency is located near 68 kHz (λ = 5 mm). Directivity is a very important parameter for microspeaker array. Dissimilar arrangement of the cells in transducer array could cause different directivity performance. After comparison, when achieving a good transmitting directivity, the square combined plane array has the smallest area.     

动圈微型扬声器设计与工艺技术

阐述了动圈微型扬声器的主要性能、技术指标和测试方法,提出了微型扬声器的设计程序以及关键制造工艺的解决方案。     

铁电-硅集成微麦克风和扬声器的理论设计

在现有Ｐｂ（Ｚｒ,Ｔｉ）Ｏ３（ＰＺＴ）铁电薄膜的制备工艺基础上,提出并设计了可集成在同一芯片上的基于ＰＺＴ铁电薄膜的压电型微麦克风、扬声器结构,对其灵敏度和声输出进行了理论计算,比较了基于ＰＺＴ和ＺｎＯ两种材料的微麦克风和扬声器的性能差异。     

Spectroscopy of Pure and Eu 3+ Doped ZnO

Pure and Eu 3+ doped ZnO piezoelectric ceramics and thin films were prepared via solid state chemical reaction and by sol-gel method, respectively. Strong green emission band were observed from all samples. Both broad band emission from ZnO and line emission from Eu 3+ were observed in the sample ZnO doped with Eu 2 O 3 . In contrast to the report in the literature, excitation spectrum showed that energy transfer from ZnO host to Eu ions in these samples was very weak and the transfer was through Eu 3+ absorption of the green emission of ZnO.     

AlN MEMS Microspeakers with High Compressive Stress北大核心CSCD

A piezoelectric micromachined micospeaker with highly c-axis oriented AlN(Aluminium Nitride)thin films was fabricated by a CMOS-compatible fabrication process. The effects of residual stress on device performance were investigated and two AlN thin films were deposited with heavily compress stress as the piezoelectric and supporting layer to enhance the sound pressure output of the microspeaker,the total residual stress of the diaphragm structure were controlled by a simple,robust fabrication process to give more deflection of the diaphragm. The diameter of the microspeaker is only 1.35 mm and thickness is 0.95 μm. The sound pressure level(SPL)has been measured with a variation of sinusoidal input frequency from 0.5 kHz to 20 kHz. The largest SPL of this microspeaker was about 75 dB at 20 Vpeak-to-peak,which was test at the distance of 10 mm from the microspeaker in open field. The results show its potential for the application in earphone,wearable devices and Internet of things(IoT). © 2018, The Editorial Office of Chinese Journal of Sensors and Actuators. All right reserved.