基于LN/LT POI多层结构的SAW器件发展

绝缘体上压电单晶薄膜结构材料(POI)为研制高性能、可集成的声表面波(SAW)器件提供了新的解决途径和方案,可满足射频(RF)前端在集成化、小型化发展趋势下对新一代压电声学器件的需求。该文介绍了POI的制备工艺技术。总结了基于铌酸锂/钽酸锂 POI(LN/LT POI)多层结构的高性能SAW器件的最新研究成果,并展望了其未来的发展。     

集成铌酸锂光子器件技术的研究进展

铌酸锂单晶薄膜(LNOI)具有透光光谱宽,折射率高,二阶非线性高及压电响应大等优点,是一种重要的集成光子学基础材料。LNOI材料具有亚波长尺度的光约束和光电器件的高密度集成能力,能够实现具有更高性能、更低成本的全新器件及应用,给光通信和微波光子学带来革命性的变革。该文重点综述了LNOI的制备技术、LNOI电光调制器、LNOI声光调制器和LNOI电光频率梳的最新研究进展,简要讨论了铌酸锂光子器件在制作工艺和系统实现中面临的挑战。     

单晶LNBAW谐振器有限元仿真研究

利用离子注入剥离法(CIS)制备的铌酸锂(LN)压电薄膜可用于制备体声波(BAW)器件,近年来备受关注.滤波器的指标与谐振器的性能密切相关,但基于LN单晶薄膜的BAW谐振器,对其结构的仿真优化还未有较深入的报道.该文以LN单晶薄膜为核心压电层材料,构建了固态反射型(SMR)单晶薄膜谐振器有限元仿真模型,对其压电层厚度和...     

42°Y钽酸锂晶体生长及性能研究

钽酸锂晶体具有优异的压电性能,是声表面波(SAW)滤波器广泛使用的衬底材料。该文采用自主研制的提拉单晶炉,成功生长出4英寸、42°Y方向、外观完整的钽酸锂晶体。经可见及近红外分光光度计测试,晶体透过率接近80%;经X线摇摆测试,其半高全峰宽(FWHM)为28.4″,单晶性较好;采用差热分析仪对生长的晶体头尾进行居里温度测试,居里温度偏差为4.4 ℃。声表面波性能测试结果表明,钽酸锂晶体的声表面波速度、机电耦合系数和频率温度系数等指标均满足SAW滤波器的使用要求。     

超宽带声表面波滤波器的设计

该文精确模拟了基于弛豫铁电单晶的声表面波(SAW)梯形滤波器的性能。首先介绍了由谐振器构成的梯形SAW滤波器的工作原理,利用QUCS软件建立了七阶梯形滤波器的仿真模型。结果表明,该单晶能实现高达620 MHz的超宽带SAW滤波器(中心频率1GHz),比传统压电材料的滤波器带宽高3倍;通过优化各支路谐振器的静态电容及传统梯型滤波器的结构,牺牲了一定的带宽,但获得了较高的带外抑制和过渡带的陡峭度;讨论了不同品质因数对滤波器带内插损的影响。     

压电MEMS兰姆波器件技术的最新进展与展望

兰姆波谐振器(LWR)作为一种新兴的压电微机电系统(MEMS)声学器件,同时具有高工作频率、高机电耦合系数、高品质因数值及低功耗等特点,其制造工艺与集成电路工艺兼容,可在单片晶圆上实现多频率器件。基于LWR的声学滤波器是实现高性能射频前端组件的有效解决方案之一,能够满足未来通信设备多频率及集成化的发展要求,其相关研究已成为微声器件领域的热点。该文简要介绍了兰姆波的基本原理,综述了近年来基于氮化铝(AlN)薄膜和铌酸锂薄膜(LNOI)的压电MEMS兰姆波器件研究取得的最新成果,并讨论了压电MEMS兰姆波器件的发展趋势。     

高频高性能声表面波器件

声表面波(SAW)器件是VHF-UHF频段中信息和传输系统的高性能关键器件.SAW器件用基片材料,包括压电常数和声速大的在蓝宝石上外延生长的ZnO单晶薄膜、温度稳定性好的石英和控制元件分散性实现高精度的SiO_2薄膜等.由于采用了三个换能器结构、抽指加权和假电极指等设计法,获得了高Q、低损耗、高稳定和高精度的SAW器件.这些器件和电路元件混合集成,可制成小型的滤波器、振荡器和FM解调器并应用于CATV、卫星广播、汽车电话和TV调谐器等方面.     

金刚石SAW滤波器的设计和制作

通信系统向高频的发展趋势使声表面波(SAW)滤波器技术面临着越来越多的挑战。利用传统材料制作SAW滤波器的中心频率很难达到GHz频段,因此探索在高声速材料基础上制作SAW滤波器成为一种必然趋势。基于高声速材料金刚石设计了IDT/ZnO/金刚石结构的薄膜SAW滤波器,设计了镜像阻抗连接IDT的结构参数,并采用ADS软件对该结构进行了建模仿真。然后,通过ZnO薄膜制备工艺和IDT电极制备工艺,获得了金刚石SAW滤波器样品。最后,采用RF探针台对所制得的样品进行了性能测试和数据分析。测试结果表明,在金刚石厚膜衬底上获得了频率超过1 GHz的SAW滤波器样品。     

ZnO/IDT/金刚石结构SAW滤波器的设计和制作

传统材料制备的声表面波(SAW)滤波器的中心频率f大多位于较低的频段(f<500 MHz),但是无线通信频段逐渐向着高频化的方向发展,因此在SAW器件领域中引入高声速材料如金刚石以提高中心频率成为一种必然趋势。基于金刚石材料、采用ZnO/IDT/金刚石新型结构,设计了交错叉指结构和镜像阻抗连接结构的叉指换能器(IDT)参数。通过优化的工艺制备流程,获得了金刚石SAW滤波器样品。最后采用RF探针台对样品进行了性能测试和数据分析。测试结果表明制备的SAW滤波器样品的测试结果与理论值比较符合,交错叉指结构滤波器获得了很低的插损,镜像阻抗连接结构滤波器有效地提高了带外抑制度。样品IDT指宽2μm,SAW滤波器中心频率可达0.775 GHz。     

基于COMSOL Multiphysics压电铌酸锂晶片仿真

压电换能器是声光可调谐滤波器(AOTF)的基础元件,而换能器的核心部件是压电铌酸锂晶片,其性能直接影响AOTF的性能。该文利用COMSOL Multiphysics多物理场耦合软件对压电铌酸锂晶片进行有限元仿真分析,基于COMSOL Multiphysics的压电模块,对超声换能器的压电铌酸锂晶片进行了瞬态分析。通过瞬态分析得到了压电铌酸锂晶片随时间变化的位移图。     

Epitaxially grown GaN thin-film SAW filter with high velocity andlow insertion loss

This study proposes GaN thin film as a piezoelectric material for SAW (surface acoustic wave) filters. Highly piezoelectric GaN film with a good surface morphology (RMS roughness =0.7 nm) was obtained on a 2-in (0001)-oriented sapphire substrate by MOCVD growth. The fabricated GaN SAW filter exhibited a very high velocity of 5803 m/s and relatively low insertion loss of -7.7 dB, The attenuation of the center frequency was about 22 dB smaller than those at the tops of the first sidelobes. When the wavelength of the IDT electrode was 60 μm (λ/4=15 μm), the center frequency was measured at 96.6 MHz, thereby facilitating a ~GHz operation when the IDT geometry is designed on a 1 μm scale. The calculated electromechanical coupling factor (K²) was about 4.3±0.3% which is larger than those obtained from other thin film piezoelectric materials and allows the realization of wider filter fractional bandwidths. TCF (temperature coefficient of frequency) was measured as low as -18.3 ppm/°C in the range from -25 to 50°C. These superior characteristics demonstrate that epitaxially grown GaN thin film can be successfully used for high performance SAW filters     

以PZT薄膜为驱动和传感的微型陀螺研制

利用压电陶瓷PZT的正反压电位效应,将PZT薄膜同时作为驱动及传感材料,设计并制造了两种新颖的以IC兼容技术制作在硅片上的压电薄膜微型陀螺。高质量的PZT薄膜是在Pt/Ti/SiO2/Si基底上以溶胶－凝胶技术铺设的。基于反压电效应,微型陀螺在其谐振频率上被输入的交流信号驱动,由其正压电效应,可检测到与转动角速度成正比的输出信号。文章分别介绍了两种微型陀螺的设计原理,详述了制作方法,并对制出的压电微型陀螺进行了检测,得到了的结果与预测结果相符。     

声表面波滤波器理论研究进展

为使声表面波(SAW)滤波器技术向更高的频段发展,对SAW滤波器的基础理论进行了分析：展示了压电材料压电效应(逆压电效应)的产生机理,并通过例子对比说明压电材料的晶体结构属性。介绍了重要的物理量机电耦合系数以及SAW传播的物理机理;重点推导了SAW在压电介质中的传播性质,并同非压电介质的传播特性进行了对比。得出SAW在压电介质中是非色散波,存在3个方向的质点位移分量;压电薄膜中SAW是色散波,且压电薄膜使得声表面波速度发生变化。     

Determination of the minority carrier lifetime in crystalline silicon thin‐film material

The effective minority carrier lifetimes on epitaxial silicon thin‐film material have been measured successfully using two independent microwave‐detected photoconductivity decay setups. Both measurement setups are found to be equally suited to determine the minority carrier lifetime of crystalline silicon thin‐film (cSiTF) material. The different measurement conditions to which the sample under investigation is exposed are critically analyzed by both simulations and measurements on a large number of lifetime samples. No systematic deviation between the lifetime results from different measurement setups could be observed, underlining the accuracy of the determined lifetime value. Subsequently, a method to separate the epitaxial bulk lifetime and the total recombination velocity, consisting of front surface and interface recombination between the epitaxial layer and the substrate, is presented. The method, based on different thicknesses of the epitaxial layer, is applied to all batches of this investigation. Each batch consists of samples with the same material quality but different epitaxial layer thicknesses whereas different batches differ in their material quality. In addition, the same method is also successfully applied on individual cSiTF samples. From the results, it can be concluded that the limiting factor of the effective minority carrier lifetime for the investigated solar‐grade cSiTF material is the elevated recombination velocity at the interface between epitaxial layer and the substrate compared with microelectronic‐grade material. In contrast, the samples cannot be classified into different material qualities by their epitaxial bulk lifetimes. Even on multicrystalline substrate, solar‐grade material can exhibit high epitaxial bulk lifetimes comparable to microelectronic‐grade material. Copyright © 2012 John Wiley & Sons, Ltd.     

Polar heterostructure for multifunction devices: theoretical studies

We examine the potential of devices based on heterostructures made from highly polar materials and semiconductors. Our calculations show that such functional devices have superior sensor properties and transistor properties. The basis device examined is based on the use of a thin oxide with high piezoelectric coefficients or pyroelectric coefficients under the gate region. Channel charge and current are controlled by gate voltage, temperature, or stress. We examine the performance of three classes of heterostructures that form the basis of important semiconductor technologies: 1) Si-SiO/sub 2/-BaTiO/sub 3/ heterostructure junctions that would be an important breakthrough for silicon sensor technology; 2) GaN-AlN-BaTiO/sub 3/ heterostructure junctions that would be important especially in high temperature sensor application; and 3) GaAs-AlGaAs-BaTiO/sub 3/ heterostructure field effect transistors. The calculations show that with a very thin polar material layer we can have a highly sensitive sensor and transistor. For optimum performance, the polar material (piezoelectric or pyroelectric) layer thickness should be /spl sim/30 /spl Aring/.     

System-in-a-package integration of SAW RF Rx filter stacked on a transceiver chip

Demands for mobile phones with smaller form factor and lower cost have driven enhanced integration of electronics components. However, surface acoustic wave (SAW) filters must be fabricated on piezoelectric substrates, and so they are difficult to monolithically integrate on semiconductor chips. This paper reports on a compact wafer-scale packaged SAW filter stacked over a transceiver chip in a quad flat-pack no-lead (QFN) package. An integrated passive device (IPD) provided redistribution and matching between the SAW filter output and the transceiver input. Both extended global system for mobile communications (EGSM) and DCS filters were evaluated. Results demonstrated that conventional packaging techniques could be used to successfully assemble stacked SAW on transceiver modules without damage. SAW compact models based on the coupling of modes model were developed to facilitate system design. Electromagnetic simulations of coupling between SAW filters and inductors integrated on the transceiver suggested that design care is needed to avoid interactions, especially if an IPD is not used as a spacer. With appropriate design, stacked SAW filter on transceiver offers viable module integration.     

Piezoelectric zinc oxide by electrostatic spray pyrolysis

Zinc oxide (ZnO) possesses many interesting properties, such as a wide energy band gap, large photoconductivity, and high excitonic binding energy. Piezoelectric (ZnO) film has a high electro-mechanical coupling coefficient, which makes it a promising material for high frequency and low surface acoustic wave (SAW), bulk acoustic wave, and microelectromechanical system devices. In this work, we present the first results obtained for piezoelectric ZnO thin films prepared on corning 7059 glass substrate by electrostatic spray pyrolysis (ESP), a simple, cheap and efficient technique not widely used for ZnO deposition, using zinc nitrate in a mixture of deionised water and isopropyl alcohol. The structural morphologic and optical properties of the films have been studied and the effect of the preparation conditions, such as substrate temperature and substrate-nozzle distance, discussed. Highly c-axis preferred orientation, which is critical for piezoelectric applications (ultrasonic oscillators and transducers devices), ZnO thin films are obtained at 350 °C growth temperature and at 4.5 cm substrate-nozzle distance.     

声表面波滤波放大器研究进展

基于声电放大效应的声表面波滤波器具有高集成度、非互异性等优势，在国防及商业领域有着广泛的应用前景。同时，新型材料和结构的研究也为未来高集成度的声表面波滤波放大器的制备提供了新思路和新方向。该文介绍了声表面波声电放大机理，分析了器件常用结构，并总结了部分器件性能指标，这对声表面波滤波放大器的应用与推广具有一定的借鉴意义。     

六方氮化硼薄膜制备及其压电响应的研究

采用射频(RF)磁控溅射的方法,通过改变工艺参数在n型Si(100)片上制备六方氮化硼(h-BN)薄膜。通过傅立叶红外(FTIR)光谱仪,X射线衍射(XRD)仪进行结构表征,原子力显微镜(AFM)进行表面形貌和压电性能表征。测试结果表明,在射频功率为300 W、衬底温度为500℃、工作压强在0.8Pa、N2与Ar流量比为4∶20和衬底偏压在-200V时制备的六方BN薄膜具有高纯度、高c-轴择优取向,颗粒均匀致密,粗糙度为2.26nm,具有压电性并且压电响应均匀,符合高频声表面波器件基片高声速、优压电性要求。薄膜压电性测试研究表明,AFM的PFM测试方法适用于纳米结构半导体薄膜的压电性及其压电响应分布特性的表征。