基于高压应力的氮化铝MEMS压电微扬声器
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摘要
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:0.5kHz～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。
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 0.95μm.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).
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 0.95μm.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).
引文
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[2]Huang S,Yang Y,Liu S,et al.A Large-Diaphragm Piezoelectric Panel Loudspeaker and Its Acoustic Frequency Response Simulation Method[J].Applied Acoustics,2017,125:176-183.
[3]Roberts R C,Du J,Ong A O,et al.Electrostatically Driven TouchMode Poly-Si C Microspeaker[C]//Sensors.IEEE,2007:284-287.
[4]Murarka A,Wang A,Jean J,et al.Printed MEMS Membrane Electrostatic Microspeakers[C]//Tech.Digest of Solid-State Sensors,Actuators and Microsystems Workshop.2014:311-314.
[5]Cho K W,Yi S H,Son Y H,et al.Characteristics of Piezoelectric Micro-Speaker Fabricated with Zn O Thin Film[J].Integrated Ferroelectrics,2007,89(1):141-149.
[6]Cho I J,Jang S,Nam H J.A Piezoelectrically Actuated Mems Speaker with Polyimide Membrane and Thin Film pb(zr,ti)o3(pzt)Actuator[J].Integrated Ferroelectrics,2009,105(1):27-36.
[7]Przybyla R,Izyumin I,Kline M,et al.An Ultrasonic Rangefinder Based on an Al N Piezoelectric Micromachined Ultrasound Transducer[C]//Sensors.IEEE,2010:2417-2421.
[8]Wygant I O,Kupnik M,Yaralioglu G,et al.6F-4 50-k Hz Capacitive Micromachined Ultrasonic Transducers for Generating Highly Directional Sound with Parametric Arrays[C]//Ultrasonics Symposium.IEEE,2007:519-522.
[9]Yi S H,Kim E S.Micromachined Piezoelectric Microspeaker[J].Japanese Journal of Applied Physics,2005,44:3836-3841.
[10]Ur S C,Kim E S,Yi S H.The Effects of Residual Stresses in the Composite Diaphragm on the Performance of Piezoelectric Microspeakers[J].Electronic Materials Letters,2013,9(1):119-123.
[11]Yi S H,Yoon M S,Ur S C.Piezoelectric Microspeakers with High Compressive Zn O Film and Floating Electrode[J].Journal of Electroceramics,2009,23(2-4):295-300.
[12]Yong Y J,Kang Y S,Lee P S,et al.Fabrication of c-Axis Oriented Zn O/Al N Thin Films Prepared by Radio Frequency Reactive Sputtering And Development of Zn O/Al N Layered Structure Surface Acoustic Wave Devices[J].Journal of Vacuum Science and Technology B,2002,20(1):42-46.
[13]Heechul Lee,Jaeyeong Park,Kyunghak Lee,et al.Silicon Bulk Micromachined High Q Film Bulk Acoustic Resonator Devices with Mo/Al N/Mo Structures[J].Integrated Ferroelectrics,2005,69(1):323-332.
[14]陳建人.微機電系統技術與應用.臺灣:行政院國家科學委員會精密儀器發展中心,2003.
[15]Horsley D A,Rozen O,Lu Y,et al.Piezoelectric Micromachined Ultrasonic Transducers for Human-Machine Interfaces And Biometric Sensing[C]//Sensors.IEEE,2016:1-4.
[16]Muralt P,Baborowski J.Micromachined Ultrasonic Transducers and Acoustic Sensors Based on Piezoelectric Thin Films[J].Journal of Electroceramics,2004,12(1-2):101-108.
[17]Lu Y,Heidari A,Horsley D A.A High Fill-Factor Annular Array of High Frequency Piezoelectric Micromachined Ultrasonic Transducers[J].Journal of Microelectromechanical Systems,2015,24(4):904-913.
[18]Muralt P,Ledermann N,Baborowski J,et al.Piezoelectric Micromachined Ultrasonic Transducers Based on PZT Thin Films[J].IEEE Trans Ultrason Ferroelectr Freq Control,2005,52(12):2276-2288.
[19]Shelton S,Chan M L,Park H,et al.CMOS-Compatible Al N Piezoelectric Micromachined Ultrasonic Transducers[C]//Ultrasonics Symposium.IEEE,2009:402-405.
[20]Yamashita K,Nishimoto H,Okuyama M.Diaphragm Deflection Control of Piezoelectric Ultrasonic Microsensors for Sensitivity Improvement[J].Sensors and Actuators A:Physical,2007,139(1):118-123.
[21]Sammoura F,Smyth K,Bathurst S,et al.An Analytical Analysis of the Sensitivity of Circular Piezoelectric Micromachined Ultrasonic Transducers to Residual Stress[C]//Ultrasonics Symposium.IEEE,2013:580-583.
[22]何凯旋,黄斌,段宝明,等.MEMS悬浮结构深反应离子刻蚀保护方法对比研究[J].传感技术学报,2016,29(2):202-207.