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Investigation of Piezoelectric Ultrasonic Technology Based on MEMS

Author: SunHongMing
Tutor: GuoHang
School: Xiamen University
Course: Measuring Technology and Instruments
Keywords: Ultrasonic testing Supersonic flow ZnO
CLC: TB55
Type: Master's thesis
Year: 2009
Downloads: 280
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Abstract

This paper studies based on MEMS piezoelectric ultrasonic technology, including ultrasonic testing, ultrasonic microfluidic drive technology and ZnO piezoelectric thin film materials and devices research topic belongs to the current micro-electromechanical systems, more cutting-edge and innovative disciplines, as described below nineties of the last century, developed a method to characterize the material properties: ultrasonic resonance spectrum technology (Resonant Ultrasound Spectrum, RUS), the method has become more commonly used technical means of modern ultrasonic testing, measurement range wide range, can be used for the detection of micro devices in the MEMS field. In the the RUS measurement process, the specimen sample is usually sandwiched between two piezoelectric transducer, a piezoelectric transducer may be used PZT or other piezoelectric ceramic or crystal. However, because the surface of the piezoelectric sheet is smooth, and the specimen is difficult to accurately caught in the middle of the two piezoelectric sheets, and to ensure that each measurement of the clamping position, thus reducing the measurement accuracy, particularly when the specimen is very small, which kinds of impact is even more significant. For this problem, and designed a new type of ultrasonic detection transducer structure, and analyze it. Separate PZT-4 transducer structure analysis and comparison, PZT / Si composite structure static displacement deviation is very small, about 2% of its order resonance frequency of the individual PZT-4 or less, these analyzes show that the the design of the PZT / Si composite piezoelectric transducer sensitivity affected small, which can be used for ultrasonic measurement of the resonance spectrum. Finally, the use of MEMS technology to create the initial structure of the composite transducer devices. 2, microfluidic technology is the rapid development of the field of MEMS discipline, and its wide range of applications, such as DNA and biomolecules test applications, environmental monitoring, inkjet printing, and LED, \cooling system. In within microfluidic disciplines, the use of ultrasound technology driven manipulation microfluidic become a hot topic in recent years, compared to other microfluidic technology has great value and potential. Acoustic streaming is more common phenomenon in ultrasound applications, the spread of the acoustic waves in a fluid medium due to fluid viscosity and decay of a non-directional flow, supersonic flow as the propagation of the high frequency acoustic waves in a fluid that can drive the fluid motion. Makes ultrasonic flow ultrasound technology applications continues to expand the application of research is more and more widely, with the continuous development of MEMS technology, the manufacture of micro-devices are getting smaller, acoustic streaming in microchannels movement is different from the traditional pipes, a large number of experimental studies on the application of acoustic streaming, but the lack of analysis of for micro size pipes within acoustic streaming system theory, it is necessary to carry out micro-channels within the study of acoustic streaming. Acoustic streaming microchannels in the design of MEMS microfluidic devices, systems research, namely the use of the PZT piezoelectric chip incentives MEMS microfluidic device, making the propagation of sound waves in the pipe, caused by the driving force within the micro channel acoustic streaming sports . Application of basic fluid dynamics theory, the driving force of the sound field of acoustic wave propagation in the pipeline internal harmony flow motion analysis. The analysis can get the amplitude of 10nm, sonic frequency 200KHz ~ 1MHz, the flow rate can be reached in 1 ~~ 9mm / s. Based on these analyzes, we can take advantage of the ultrasonic method for drive control of the MEMS microfluidic device in order to apply in terms of particle delivery and micro-channel cooling. 3, ZnO as the piezoelectric thin film with a lower dielectric constant and high electromechanical coupling coefficient can be used for MEMS microphones, micro-acceleration sensor and bulk acoustic resonance devices, such as micro-sensing and execution devices have a wide range of applications in the field of MEMS . Therefore, in order to meet the demand of ultrasonic piezoelectric ultrasonic technology incentive research in different material substrates by magnetron sputtering growth of high quality ZnO as a piezoelectric film, micro-fabrication and IC process in order to achieve the ZnO thin film devices compatible, consider Al material for the process of the lower electrode of the piezoelectric device on the basis of this article is still experimental. Magnetron sputtering growth of 1 ~ 2μm thick ZnO films on different substrates used in the experiment experimental samples, XRD and SEM, to study the process of magnetron sputtering process parameters, substrate and annealing process The impact on the ZnO film quality, thereby obtaining the preparation of high-quality thin film technology in order to meet the performance requirements of the piezoelectric. The results show that the surface deposition the silicon sputtering Al film of the surface area of ??the ZnO thin film silicon Si_xN_y C-axis preferred orientation growth characteristics, select the appropriate annealing process has improved the quality of the crystal can be. On this basis, in order to be able to be compatible with the CMOS process, the development is still using Al as the bottom electrode but isolated from the thin film and a ZnO layer with a layer Si_xN_y MEMS micro-fabrication process of the piezoelectric devices.

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