基于柔性基薄膜体声波谐振器的研究

发布时间：2018-05-10 11:03

本文选题：薄膜体声波谐振器 + 柔性基底　；参考：《电子科技大学》2017年硕士论文

【摘要】：近年来随着无线通讯技术的不断发展,薄膜体声波器件在射频前端应用中的优势越来越明显,其中薄膜体声波谐振器是体声波器件的基本组成部分。该类型谐振器是一种基于压电技术的元器件,其尺寸极小,比单纯以电磁波为传播信号的元器件尺寸小4~5个数量级;插损小,Q值高(可达1000以上);工作频率高,可承受的功率容量比声表面波器件更大;并且可以与CMOS工艺兼容。鉴于以上优点薄膜体声波谐振器技术迅速占领了射频通信市场。同时,在传感器领域如生化检测等方面也有着广阔的应用前景。按照限制声波方式的不同,体声波谐振器分为空气隙型(FBAR)、固态装配型(SMR)和硅背刻蚀型谐振器。传统体声波谐振器的制备工艺复杂、成本高。为了降低体声波谐振器的工艺门槛,使其得到更广泛的研究与应用,本论文研究了基于柔性基底的体声波谐振器。采用声阻抗很小的柔性材料作为基底,这种基底可以高效的反射声波,所以该类型谐振器无需制备工艺复杂的空腔结构或布拉格反射层结构,这大大降低了体声波谐振器的工艺难度与复杂度,同时拓宽了其应用领域。本文首先从理论上分析了基于柔性基底体声波谐振器的工作原理,完善了其理论基础。提出了基于柔性基体声波谐振器的三种实现形式:成品PI基底器件、匀胶固化式器件和凹槽填充式器件。并利用Comsol Multiphysics有限元仿真软件对器件进行了建模仿真,从器件的电学性能和热力学性能两大方面对器件进行了仿真分析。发现采用声阻抗极小的PI衬底在理论上也可以得到性能良好的器件,仿真发现直接以PI为衬底的器件Q值可以达到1300。在对匀胶固化式器件的仿真分析中得出结论:PI厚度过小时存在大量的反射波造成的寄生谐振模式,当PI厚度达到10μm以上时寄生模量才能被有效抑制。随着PI厚度的增加器件的有效机电耦合系数不断增大,器件Q值有下降趋势;在热力学性能的分析中,发现对于匀胶固化式器件,PI层每增加2μm器件的最高稳态温度上升33K;凹槽填充式器件极大的优化了器件的热力学性能,同样在PI厚度为10μm的条件下,比匀胶固化式器件的最高稳态温度降低142.44K。在理论分析的基础上,对基于柔性基底的体声波谐振器进行了实验制备。首先对基于柔性基底上Mo电极层和AlN压电层材料的最优制备条件进行了探索,对于Mo膜分别研究了溅射功率、压强、气体流量和基底温度对薄膜性能的影响;对于AlN膜分别研究了溅射功率、基底温度和氮气含量对薄膜性能的影响;发现了在水冷条件下制备的薄膜性能要优于加热条件下制备的薄膜性能这一特殊规律,得出了制备薄膜的最优条件。最后基于该条件利用MEMS工艺对三种结构的谐振器进行了制备,最终成功制备出以成品PI为衬底的谐振器与匀胶固化式谐振器,并进行了测试。
[Abstract]:In recent years, with the development of wireless communication technology, the advantages of thin film bulk acoustic devices in RF front-end applications are becoming more and more obvious, in which thin film bulk acoustic resonators are the basic components of bulk acoustic devices. This type of resonator is a kind of component based on piezoelectric technology. It has a very small size, which is 4 ~ 5 orders of magnitude smaller than that of a simple electromagnetic wave propagating signal, and has a high Q value (up to 1000 or more) and a high operating frequency. The acceptable power capacity is larger than the saw device, and is compatible with the CMOS process. In view of the above advantages, thin film bulk acoustic resonator technology has rapidly occupied the radio frequency communication market. At the same time, it also has a broad application prospect in the field of sensors such as biochemical detection. According to the different ways of limiting acoustic waves, bulk acoustic resonators are divided into air gap type (FBARA), solid-state assembly type (SMR) and silicon back etching type (SMR). The traditional bulk acoustic resonator has complex preparation process and high cost. In order to reduce the technological threshold of bulk acoustic resonator and make it more widely studied and applied, this paper studies the bulk acoustic resonator based on flexible substrate. A flexible material with a small acoustic impedance is used as the substrate, which can reflect sound waves efficiently, so the type of resonator does not need to prepare a complex cavity structure or a Bragg reflector structure. This greatly reduces the process difficulty and complexity of bulk acoustic resonator and widens its application field. In this paper, the working principle of acoustic resonator based on flexible substrate is analyzed theoretically, and the theoretical basis is improved. Three types of acoustic resonator based on flexible substrate are proposed: Pi substrate device, uniform curing device and groove-filled device. The Comsol Multiphysics finite element simulation software is used to model and simulate the device. The electrical and thermodynamic properties of the device are simulated and analyzed. It is found that the Pi substrate with minimal acoustic impedance can also be used to obtain the devices with good performance in theory. The simulation results show that the Q value of the device with Pi substrate directly can reach 1 300. In the simulation analysis of the homogenized solidified device, it is concluded that there exists a large number of parasitic resonance modes caused by a large number of reflected waves when the thickness of the Pi is too small, and the parasitic modulus can be effectively suppressed when the Pi thickness is more than 10 渭 m. With the increase of Pi thickness, the effective electromechanical coupling coefficient of the device increases, and the Q value of the device tends to decrease. It is found that the maximum steady-state temperature of the device increases 33K for every increase of 2 渭 m in the Pi layer, and the thermodynamics of the device is greatly optimized under the condition of Pi thickness of 10 渭 m, and the maximum steady-state temperature of the device is increased by 33K, and the thermodynamics of the device is greatly optimized when the Pi thickness is 10 渭 m. The maximum steady-state temperature is decreased by 142.44K. On the basis of theoretical analysis, the bulk acoustic resonator based on flexible substrate is fabricated experimentally. Firstly, the optimal preparation conditions of Mo electrode layer and AlN piezoelectric layer based on flexible substrate were investigated. The effects of sputtering power, pressure, gas flow rate and substrate temperature on the properties of Mo film were studied. The effects of sputtering power, substrate temperature and nitrogen content on the properties of AlN films were studied. The optimal conditions for the preparation of thin films were obtained. Finally, based on this condition, three kinds of resonators were fabricated by MEMS process. Finally, the resonators based on the finished Pi substrate and the homogenized cured resonators were successfully fabricated and tested.
【学位授予单位】：电子科技大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TN65

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