A new model for film bulk acoustic wave resonators

Based on cavity resonance and sandwich composite plate （3D） theoretical model for frequency dispersion characterization theory, this paper presents a universal three-dimensional and displacement profile shapes of the film bulk acoustic resonator （FBARs）. This model provides results of FBAR excited thickness-extensional and flexure modes, and the result of frequency dispersion is proposed in which the thicknesses and impedance of the electrodes and the piezoelectric material are taken into consideration; its further simplification shows good agreement with the modified Butterworth-Van-Dyke （MBVD） model. The displacement profile reflects the vibration stress distribution of electrode shapes and the lateral resonance effect, which depends on the axis ratio of the electrode shapes a/b. The results are consistent with the 3D finite element method modeling and laser interferometry measurement in general.

Tunable Ba_(0.5) Sr_(0.5) TiO_3 film bulk acoustic resonators using SiO_2 /Mo Bragg reflectors

Tunable and switchable Ba 0.5 Sr 0.5 TiO 3 film bulk acoustic resonators（FBARs） based on SiO 2 /Mo Bragg reflectors are explored,which can withstand high temperature for the deposition of Ba x Sr 1 x TiO 3（BST） films at 800 C.The dc bias-dependent resonance may be attributed to the piezoelectricity of the BST film induced by an electrostrictive effect.The series resonant frequency is strongly dc bias-dependent and shifts downwards with dc bias increasing,while the parallel resonant frequency is only weakly dc bias-dependent and slightly shifts upwards at low dc bias（ 45 V） while downwards at higher dc bias.The calculated relative tunability of shifts at series resonance frequency is around 2.3% and the electromechanical coupling coefficient is up to approximately 8.09% at 60-V dc bias,which can be comparable to AlN FBARs.This suggests that a high-quality tunable BST FBAR device can be achieved through the use of molybdenum（Mo） as the high acoustic impedance layer in a Bragg reflector,which not only provides excellent acoustic isolation from the substrate,but also improves the crystallinity of BST films withstanding higher deposition temperature.

微型FBAR器件性能优化设计

利用有限元仿真软件建立了薄膜体声波谐振器模型,研究了不同谐振面积(3600~10000μm^(2))条件下,电极形状(矩形、梯形、圆形和正五边形)及变迹角(30°、36°、40°和45°)对寄生谐振的影响,得到史密斯阻抗曲线和不圆度值,讨论了阶梯负载结构对横向声波泄露的抑制作用。仿真结果表明,电极形状为非正五边形,变迹角为40°时,对寄生谐振的抑制效果最好;在谐振面积为3600μm^(2)时,其不圆度为6.45%,与谐振面积为10000μm^(2)时矩形电极相当。设计的电极阶梯负载结构提升了并联谐振点处的品质因数,当电极横向尺寸为60μm时,二阶电极负载结构的品质因数为1378,比无电极负载结构的品质因数高10.07%。

薄膜体声波谐振器FBAR技术在滤波器的应用研究及其专利数据分析

本文简单介绍了薄膜体声波谐振器FBAR的具体结构、工作原理以及FBAR技术的应用,重点介绍了FBAR技术在滤波器的应用及其工作原理,梳理了常见的几种FBAR滤波器结构,最后通过检索分析,从多个角度对FBAR技术在滤波器应用领域的专利申请进行专利分析,为后续企业在该应用领域进行专利布局提供一定的参考价值。

Manipulations of micro/nanoparticles using gigahertz acoustic streaming tweezers

Contactless acoustic manipulation of micro/nanoscale particles has attracted considerable attention owing to its near independence of the physical and chemical properties of the targets,making it universally applicable to almost all biological systems.Thin-film bulk acoustic wave(BAW)resonators operating at gigahertz(GHz)frequencies have been demonstrated to generate localized high-speed microvortices through acoustic streaming effects.Benefitting from the strong drag forces of the high-speed vortices,BAW-enabled GHz acoustic streaming tweezers(AST)have been applied to the trapping and enrichment of particles ranging in size from micrometers to less than 100 nm.However,the behavior of particles in such 3D microvortex systems is still largely unknown.In this work,the particle behavior(trapping,enrichment,and separation)in GHz AST is studied by theoretical analyses,3D simulations,and microparticle tracking experiments.It is found that the particle motion in the vortices is determined mainly by the balance between the acoustic streaming drag force and the acoustic radiation force.This work can provide basic design principles for AST-based lab-on-a-chip systems for a variety of applications.

FBAR电极和压电薄膜制备工艺研究

薄膜体声波谐振器(FBAR)制备工艺中,压电薄膜及金属电极的质量和形貌直接影响了器件的性能如品质因数、插入损耗及带宽等。研究了决定FBAR性能的关键工艺,包括Mo电极的刻蚀、AlN压电薄膜的溅射和腐蚀,从而实现高质量电极及压电薄膜结构。同步调节光刻胶掩膜侧壁角度和刻蚀选择比,得到了平缓的底电极侧壁角度,实现了有利于AlN溅射连续性的底电极形貌,通过调节溅射工艺中N_(2)流量组分和温度等参数得到高质量的AlN薄膜,对比不同质量分数和温度的腐蚀溶液对AlN腐蚀工艺的影响,对AlN腐蚀不净及钻蚀问题进行分析,得到最佳的AlN腐蚀条件。最终工艺优化后制备出的FBAR经测试具有良好的滤波器特性,该研究对FBAR制备工艺和性能的提升具有借鉴意义。

A Micro-Electro-Mechanical System-Based Bulk Acoustic Wave Piezoelectric Disk Resonator for Detecting z-axis Rotation Rate

This paper presents a bulk acoustic wave piezoelectric disk resonator based on a special pair of degenerative modes, to detect z-axis angular velocity. A single piezoelectric disk is operated in its appropriate modes in the k Hz frequency range to achieve this function. This design combines the bulk acoustic wave drive/sense mode with lead zirconate titanate resonator which improves device's performance and simplifies its structural complexity. The operation principle of piezoelectric disk resonator is given and validated by finite element method,and the scale factor of piezoelectric disk resonator is 0.977 μV/[(°) · s-1] without any amplification section.The results of impedance analysis for the prototype in the air, which is fabricated on lead zirconate titanate wafer by Micro-Electro-Mechanical System process, show that the resonant frequency of the piezoelectric disk resonator is about 190 k Hz. Moreover, the measured frequency split between drive and sense mode is about290 Hz without any tuning methods. At last, a closed-loop driving and detecting circuit system is designed and its modulation/demodulation method is studied, preliminary experiments show that this device is not sensitive to acceleration, but is sensitive to angular velocity, its performance parameters need follow-up experiments.

大于3 GHz超宽带FBAR滤波器结构设计与仿真

该文提出了一种获得相对带宽约为70.61%的基于氮化铝薄膜的超宽带薄膜体声波谐振器(FBAR)滤波器的设计方法,即在中心频率为6.5 GHz下滤波器的带宽为4.835 GHz。仿真分析表明,通过串并联电感的方式,并在电感端串并联电容,可消除因增加电感而带来的谐波谐振点干扰对带通的影响,实现了FBAR滤波器的超宽带。该工作开辟了设计和制作带宽超过3 GHz的超宽带体声波滤波器的新途径。

Portable FBAR based E-nose for cold chain real-time bananas shelf time detection

Being cheap,nondestructive,and easy to use,gas sensors play important roles in the food industry.However,most gas sensors are suitable more for laboratory-quality fast testing rather than for cold-chain continuous and cumulative testing.Also,an ideal electronic nose(E-nose)in a cold chain should be stable to its surroundings and remain highly accurate and portable.In this work,a portable film bulk acoustic resonator(FBAR)-based E-nose was built for real-time measurement of banana shelf time.The sensor chamber to contain the portable circuit of the E-nose is as small as a smartphone,and by introducing an air-tight FBAR as a reference,the E-nose can avoid most of the drift caused by surroundings.With the help of porous layer by layer(LBL)coating of the FBAR,the sensitivity of the E-nose is 5 ppm to ethylene and 0.5 ppm to isoamyl acetate and isoamyl butyrate,while the detection range is large enough to cover a relative humidity of 0.8.In this regard,the E-nose can easily discriminate between yellow bananas with green necks and entirely yellow bananas while allowing the bananas to maintain their biological activities in their normal storage state,thereby showing the possibility of real-time shelf time detection.This portable FBAR-based E-nose has a large testing scale,high sensitivity,good humidity tolerance,and low frequency drift to its surroundings,thereby meeting the needs of cold-chain usage.

High Q,high frequency,high overtone bulk acoustic resonator with ZnO films

Bulk acoustic wave resonators with piezoelectric films have been widely explored for the small size and high quality factor （Q） at GHz. This paper describes a high overtone bulk acoustic resonator （HBAR） based on AI/ZnO/AI sandwich layers and c-axis sapphire substrate. ZnO film with high quality c-axis orientation has been obtained using DC magnetron sputtering. The fabricated HBAR presents high Q at the multiple resonances from a 0.5-4.0 GHz wide band with a total size （including the contact pads） of 0.6 mm×0.3 mm×0.4 mm, The device exhibits the best acoustic coupling at around 2.4 GHz, which agrees with the simulation results based on the one-dimensional Mason equivalent circuit model. The HBAR also demonstrates Q values of 30 000, 25 000, and 6500 at 1.49, 2.43, and 3.40 GHz, respectively. It is indicated that the HBAR has potential applications for the low phase noise high frequency oscillator or microwave signal source.

基于优化布拉格结构的固态装配型谐振器

体声波谐振器的有效耦合系数和品质因数决定了体声波滤波器的整体性能。有效耦合系数依赖于叠层结构和压电材料。而品质因数高度依赖于损耗机制,主要为电学损耗和声学损耗。对于固态装配型谐振器(SMR),声学损耗主要为透过衬底的能量泄漏。为提高SMR的品质因数,改进了布拉格堆叠结构,使纵波和剪切波同时被约束在压电堆叠结构中,以减少声能对衬底的泄漏。同时,为抑制谐振腔的杂散模式,优化了布拉格结构顶层薄膜厚度,器件色散特性由Ⅱ型变为Ⅰ型。通过仿真和实验表明:基于优化布拉格结构的SMR性能得到了明显改善。

Preparation of AlN thin films for film bulk acoustic resonator application by radio frequency sputtering

Aluminum nitride （AlN） thin films with high c-axis orientation have been prepared on a glass substrate with an Al bottom electrode by radio frequency （RF） reactive magnetron sputtering. Based on the analysis of Berg＇s hysteresis model, the improved sputtering system is realized without a hysteresis effect. A new control method for rapidly depositing highly c-axis oriented AlN thin films is proposed. The N2 concentration could be controlled by observing the changes in cathode voltage, to realize the optimum processing condition where the target could be fixed stably in the transition region, and both stoichiometric film composition and a high deposition rate could be obtained. Under a 500 W RF power of a target with a 6 cm diameter, a substrate temperature of 450 ℃, a target-substrate distance of 60 mm and a N2 concentration of 25%, AlN thin film with preferential （002） orientation was deposited at 2.3 μm/h which is a much higher rate than previously achieved. Through X-ray diffraction （XRD） analysis, the full width at half maximum （FWHM） of AlN （002） was shown to be about 0.28°, which shows the good crystallinity and crystal orientation of AlN thin film. With other parameters held constant, any increase or decrease in N2 concentration results in an increase in the FWHM of AlN.

窄带FBAR带通滤波器设计

由薄膜体声波谐振器构成的滤波器,其带宽受压电材料机电耦合系数的影响,较难实现窄带滤波器设计。使用ADS射频仿真软件设计了一种通带为1.18～1.20 GHz的窄带薄膜体声波滤波器,分别通过比较增加无源电容元件、改变串并联谐振器面积比、在压电振荡堆内增加一层非压电层和采用两个中心频率不同的薄膜体声波滤波器串联这四种方法,得出窄带薄膜体声波滤波器的优化设计方案。设计得到的滤波器突破了压电材料本身机电耦合系数限定的带宽值,实现了窄带要求,并且带外抑制以及带内插损等设计指标均满足要求。

S波段网格型FBAR滤波器的研制

介绍了一种单端口,端口阻抗为50Ω的S波段宽带薄膜体声波谐振器（FBAR）滤波器,该滤波器采用网格型结构的FBAR滤波器芯片级联巴伦芯片实现。对宽带FBAR滤波器芯片的设计过程、工艺实现过程进行了说明。采用0.35μm Ga As工艺实现了3~8 GHz频率范围的巴伦芯片,在FBAR滤波器芯片的中心频率处,幅度不平衡度为0.53 d B,相位不平衡度为0.55°。制备的FBAR滤波器通带频率范围为3 100~3 400 MHz,1 d B带宽约为369 MHz,在2 660 MHz和3 840 MHz处带外抑制分别为45.6 d Bc和41.3 d Bc,尺寸仅为12 mm×7 mm×2.9 mm。将实测结果与仿真结果进行了对比,两者一致性很好。

密封空气型FBAR温度传感器

薄膜体声波谐振器(FBAR)是性能优良的压电换能器。通过在体硅刻蚀型FBAR背面密封空气的方法制作了密封空气型FBAR,研究了密封空气型FBAR用作温度传感器的可行性。实验结果表明,在20～100℃的温度范围内,密封空气型FBAR温度传感器的并联谐振频率随温度线性变化,且具有很好的稳定性与可靠性。

S波段低插损FBAR陷波器的研制

该文介绍了一种单端口、端口阻抗50Ω的S波段薄膜体声波谐振器(FBAR)陷波器,其采用了梯形拓扑结构与外围匹配电路相结合的方式。对FBAR陷波器芯片的设计过程、工艺实现进行了说明。测试制备的FBAR陷波器,其陷波频段为2399~2412 MHz,陷波抑制达35 dBc;通带频率分别为1800~2300 MHz和2500~2800 MHz,通带插损仅1 dB;3 dBc开口宽度为69 MHz。FBAR陷波器芯片尺寸为1.2 mm×1.2 mm×0.35 mm。结果表明,陷波器实测与仿真结果两者相吻合。

X波段FBAR用AlN薄膜制备研究

采用中频磁控溅射法,在硅基上制备了X波段薄膜体声波谐振器(FBAR)滤波器用AlN压电薄膜。对AlN薄膜进行了分析表征,结果表明,AlN压电薄膜具有良好的(002)面择优取向,摇摆曲线半峰宽为2.21°,膜厚均匀性优于0.5%,薄膜应力为-5.02 MPa,应力可在张应力和压应力间进行调节。将该AlN薄膜制备工艺应用于FBAR器件的制作,研制出X波段FBAR器件,谐振频率为9.09 GHz,插入损耗为-0.38 dB。

一款2.4 GHz WiFi频段FBAR带通滤波器设计

该文设计了一款2.4 GHz WiFi频段(2401~2483 MHz)薄膜体声波谐振器(FBAR)滤波器。采用一维Mason电路模型,在ADS中搭建了阶梯形滤波器电路;在HFSS中建立了封装结构和测试电路有限元电磁模型,并在ADS中完成了联合仿真设计。通过微机电系统(MEMS)工艺制备与测试,滤波器在2401~2483 MHz频段的插入损耗≤2.2 dB。在2520~2900 MHz处,带外抑制≥40 dB,滤波器体积仅1.1 mm×0.9 mm×0.65 mm。

边缘空气层薄膜体声波谐振器的设计与制备

压电薄膜存在固有的对压电效应的非线性迟滞响应,并且声波有向边缘传播的横波分量,二者都会产生声波的能量损耗。该文设计了一种具有边缘空气层结构的单晶氮化铝薄膜体声波谐振器,可以减小非线性迟滞的机电损耗并阻止横波能量泄露,提高谐振器的品质因数。使用COMSOL对设计的器件进行有限元模拟仿真,并成功制备出具有边缘空气层结构的谐振器进行测试验证。

薄膜体声波谐振器(FBAR)谐振特性的模拟分析

主要利用Mason等效电路模型对加入介质声损耗的薄膜体声波谐振器输入阻抗公式进行了推导,并利用该结果对薄膜体声波谐振器的谐振特性进行了模拟分析,分别就不同压电层材料和厚度以及不同电极材料和厚度对薄膜体声波谐振器谐振特性的影响进行了详细分析.结果表明,薄膜体声波谐振器谐振频率主要由压电材料和厚度决定但电极的影响也是很大的.在制作高频FBAR器件(5GHz以上)时,采用氮化铝作压电材料比用氧化锌作压电材料更合适.