AIN薄膜体声波谐振器性能分析

采用体硅微细加工工艺制备了背空腔型AIN薄膜体声波谐振器。研究了压电层、上电极及支撑层厚度对谐振器性能的影响。测试结果表明，谐振器所用AIN压电薄膜具有（002）择优取向，器件频率特性良好。当上电极、压电层、底电极和支持层的厚度分别为110，2600，110，200nm时，谐振频率为1．759GHz，机电耦合系数3．75％，品质因数79．5。结合Mason等效电路模型模拟分析与实验结果，分析了各层厚度对频率特性的影响机理。     

缓冲层和外部电阻抗对薄膜体声波谐振器频率特性的影响

通过在AlN薄膜体声波谐振器上引入压电缓冲层和外部电阻抗来调节谐振器的频率特性,在考虑了缓冲层和外部电阻抗后,得到薄膜谐振器的输入电阻抗公式,并用来描述器件的机电行为。通过计算阻抗-频率谱评估了薄膜谐振器的频率特性和有效机电耦合系数k2eff,研究了缓冲层和外部电阻抗包括电阻、电感、电容对薄膜谐振器的阻抗-频率谱的影响。计算结果表明,外部电阻抗的引入可根本上改变薄膜谐振器的共振频率,且对k2eff有重要的影响。     

AlN薄膜体声波谐振器的制备与性能分析

采用直流磁控反应溅射,在Pt电极上沉积了AlN压电薄膜,并制备了以SiO2为声反射层的体声波谐振器。用X-射线衍射(XRD)、电镜扫描(SEM)、原子力显微镜(AFM)测试表明,制备出的AlN薄膜具有高c轴择优取向、良好的柱状晶结构以及平滑的表面;用网络分析仪测试体声波谐振器得到较好的频率特性,即串、并联谐振频率分别为1.22 GHz1、.254 GHz,机电耦合系数为6.68%,带宽20 MHz。     

FBAR有效机电耦合系数的影响因素分析

针对有效机电耦合系数(k2eff)的两种影响因素-薄膜体声波谐振器(FBAR)的电极/压电层厚度比与压电层薄膜的c轴取向,分别建立了厚度比可变与c轴取向可变的三层复合结构的FBAR三维仿真模型。以一个谐振频率为2.185GHz的FBAR谐振器作为分析案例,通过仿真得出,设计得到的膜层厚度比为0.206时,虽然FBAR的k2eff略有下降,但此时Mo电极厚为0.247μm,AlN压电层厚为1.119 7μm,使得FBAR电学性能较好,工艺制备复杂度及时间降低。另外,c轴倾斜角度为3°时,会使FBAR的k2eff下降,同时FBAR阻抗特性曲线产生较强的寄生谐振,这会引起FBAR横向能量泄露,恶化FBAR滤波器的带内插损。因此,在制备AlN薄膜时应该严格把握各项工艺参数。此外,通过适当放宽FBAR谐振器谐振频率增量能使k2eff具有一定冗余量来弥补工艺制备引起的k2eff下降。     

高阶兰姆波MEMS声表面波谐振器仿真研究

以有限元法为基础,对高阶兰姆波型微机电系统(MEMS)声表面波谐振器进行了仿真。研究了压电材料及其厚度、Si基底厚度对高阶兰姆波声速的影响规律,结果表明,AlN压电薄膜器件的高阶兰姆波的声速比ZnO和LiNbO3器件更大。压电材料较薄时传播兰姆波,太厚时则传播瑞利波。高阶兰姆波的声速随着硅基底厚度增加而逐渐降低,并趋于一个稳定值。在此基础上,提出了在电极上方加载一层压电薄膜来提高兰姆波声速的器件结构,仿真结果表明,通过增加一层AlN薄膜,可提高高阶兰姆波的声速,进而提高器件的谐振频率。     

基于AlN压电层的薄膜体声波谐振器

以AlN薄膜为压电层,采用体硅微细加工工艺制备了背空腔型结构薄膜体声波谐振器.材料测试结果表明,在优化溅射工艺下沉积的AlN薄膜具有(002)择优取向及良好的柱状晶结构.扫描电镜表征证实所制得的空腔背部平滑且各向异性较好.用网络分析仪测试可知,最终所制得的谐振器具有较好的频率特性:谐振频率为2.537GHz,机电耦合系数为3.75%,串、并联品质因数分别为101.8和79.7.     

基于AlN压电层的薄膜体声波谐振器

以AlN薄膜为压电层,采用体硅微细加工工艺制备了背空腔型结构薄膜体声波谐振器.材料测试结果表明,在优化溅射工艺下沉积的AlN薄膜具有(002)择优取向及良好的柱状晶结构.扫描电镜表征证实所制得的空腔背部平滑且各向异性较好.用网络分析仪测试可知,最终所制得的谐振器具有较好的频率特性:谐振频率为2.537GHz,机电耦合系数为3.75%,串、并联品质因数分别为101.8和79.7.     

薄膜体声波谐振器调频工艺研究

薄膜体声波器件具有体积小及性能高等优势,相关产品已被广泛应用于移动通信市场。薄膜体声波谐振器(FBAR)电极层和压电层等声学层的厚度、材料是影响谐振频率的主要因素。该文分析了FBAR调频的必要性、原理及扫描刻蚀的工作方式,研究了调频层薄膜在不同刻蚀功率时对器件频率的影响。通过对FBAR器件进行调频,频率均匀性提高了6.5倍,频率分散性得到显著改善。     

高性能AlN薄膜体声波谐振器的研究

报道了一种空气隙型S波段薄膜体声波谐振器,该谐振器采用一维Mason模型进行仿真,电极材料选用Mo,压电薄膜材料选用AlN,通过对AlN薄膜制备条件的优化,得到了半高宽为3.32°的AlN压电薄膜,并用于研制薄膜体声波谐振器。测试结果表明,其串联谐振频率和并联谐振频率分别为2 185 MHz和2 217 MHz,有效机电耦合系数(kt2)为3.56%,在串联谐振频率和并联谐振频率处的品质因数(Q)值分别为1 571.89和586.62,kt2Q达到了55.96。根据实测结果提取了MBVD模型的参数,并将实测结果与MBVD拟合结果进行了对比,两者吻合得很好。     

硅基氮化镓微机械谐振器研究

GaN不仅具有与硅媲美的较高声速,而且也有与氮化铝相当(AlN)的大压电系数, 所以是制作MEMS谐振器的有力备选材料.研究设计了一款硅基压电氮化镓(GaN)MEMS谐振器.利用GaN中的二维电子气(2DEG)可作为开关嵌入电极的特性,通过GaN压电材料实现由电极、压电薄膜、电极组成薄膜微机械谐振器.工作时在两个电极之...     

基于薄膜体声波谐振器的高灵敏度质量传感器

提出了一种针对于生物传感应用的薄膜体声波谐振(Thin film bulk acoustic resonator,FBAR)质量传感器。薄膜体声波谐振器谐振频率非常高(GHz数量级),同时具有很高的品质因数,因此基于这种器件的质量传感器具有非常高的质量灵敏度。提出了三对全金属Al-W层作为布拉格声学反射层的FBAR,采用AlN作为压电层,制备出了固态装配型FBAR传感器。通过淀积不同厚度Al层顶电极,对器件的质量灵敏度进行了分析,得到质量传感器串联谐振频率在2.8GHz附近,质量响应度达到5×10-4ng/Hz/cm2,可以实现分子量级的质量传感。     

FBAR用高质量AlN薄膜制备

采用直流磁控反应溅射法,在基片表面引入RF偏置,在Si(111)衬底上成功制备了(002)向AlN薄膜。使用高分辨率X射线衍射仪(XRD)来表征薄膜质量。当RF偏置从0 W变化到20 W时,XRD测试(002)摇摆曲线的半高宽有着显著的变化。当RF偏置为15 W时,AlN薄膜表现出了良好的(002)生长取向。实验结果表明,适当的RF偏置能够提高Al原子和N原子反应时的活性,促进AlN薄膜的(002)择优生长。该溅射方案应用于薄膜体声波谐振器(FBAR)谐振器工艺加工,成功制作了Q值为300,机电耦合系数为5%的FBAR样品。     

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。     

Fabrication and characterization of stacked ZnO and ZnOGa2O3 layers for the realization of bulk acoustic wave resonated membranes

ZnOGa₂O₃ alloys have been deposited by electron beam co-evaporation technique below the piezoelectric radio frequency magnetron sputtered ZnO films, with the aim of reducing the compressive stress due to the piezoelectric zinc oxide elaborated by radio frequency magnetron technique. The structural characterizations of the Ga₂O₃ thin films show an amorphous structure. Co-evaporating gallium oxide with zinc oxide has improved the optical and structural qualities of the e-beam zinc oxide films. Thus, deposing compressive rf magnetron sputtered piezoelectric ZnO on tensile thin layers of ZnOGa₂O₃, has reduced the stress and improved the structural quality of the realized bulk acoustic wave resonators. The fabrication of less stressed ZnO resonators has permitted to liberate partially our membranes by attacking the silicon substrate on which the resonator is realized. Finally, hyper frequency characterizations have been done by a network analyzer to study the influence of the silicon substrate thickness on the piezoelectric activity.     

Preparation of Oriented Aluminum Nitride Thin Films on Polyimide Films and Piezoelectric Response with High Thermal Stability and Flexibility

c‐Axis oriented aluminum nitride (AlN) thin films are successfully prepared on amorphous polyimide films by radiofrequency magnetron reactive sputtering at room temperature. Structural analysis shows that the AlN films have a wurtzite structure and consist of c‐axis oriented columnar grains about 100 nm wide. The full width at half maximum of the X‐ray diffraction rocking curves and piezoelectric coefficient d₃₃ of the AlN films are 8.3° and 0.56 pC N^–1, respectively. The AlN films exhibit a piezoelectric response over a wide temperature range, from –196 to 300 °C, and can measure pressure within a wide range, from pulse waves of hundreds of pascals to 40 MPa. Moreover, the sensitivity of the AlN films increases with the number of times it was folded, suggesting that we can control the sensitivity of the AlN films by changing the geometric form. These results were achieved by a combination of preparing the oriented AlN thin films on polyimide films, and sandwiching the AlN and polymer films between top and bottom electrodes, such as Pt/AlN/polyimide/Pt. They are thin (less than 10 μm), self powered, adaptable to complex contours, and available in a variety of configurations. Although AlN is a piezoelectric ceramic, the AlN films are flexible and excellent in mechanical shock resistance.     

The fabrication of thin-film bulk acoustic wave resonatorsemploying a ZnO/Si composite diaphragm structure using porous siliconlayer etching

Thin-film bulk acoustic wave resonators (FBARs) are used in monolithic microwave integrated circuits (MMICs) for semiconductor devices. FBARs are more attractive than surface acoustic wave resonators since they have the advantages of small size, low cost, and mass-production ability. In this letter, an FBAR with an air gap is fabricated by a surface micromachining technique which utilizes porous silicon layer (PSL) etching. This FBAR has a forward reflection coefficient of -18.912 dB when the thickness of the ZnO thin film measures 1 μm. The FBAR is composed of a piezoelectric zinc oxide (ZnO) thin film and top and bottom electrode thin films of Au(1000 Å)/Ni-Cr(50 Å). The ZnO thin film is deposited by RF magnetron sputtering. This fabrication process is compatible with conventional IC processes, thereby enabling the development of monolithic-integrated FBAR's on Si or GaAs substrates     

不锈钢表面溅射氮化铝陶瓷膜工艺参数的研究

工业生产中需要测量机械零件的润滑油膜厚度,利用超声波检测可实现无损检测的目的。利用氮化铝(AlN)陶瓷膜制成的压电换能器对超声波发射和接收。利用射频磁控溅射技术,在不锈钢表面沉积AlN薄膜。利用X线衍射仪(XRD)和原子力显微镜(AFM)等设备对AlN薄膜结构表征,并对结果进行了讨论。     

Synthesis of <Emphasis Type="Italic">c</Emphasis>-Axis Inclined AlN Films in an Off-Center System for Shear Wave Devices

AlN thin films are of continuing interest for excitation of acoustic waves in surface and bulk acoustic wave devices. We report herein on preparation and characterization of c-axis inclined AlN films by a new method of rotating the substrate holder plate to different angles in an off-center system. The microstructure of the c-axis inclined AlN films was investigated using x-ray diffraction, scanning electron microscopy, and transmission electron microscopy. The analyses showed that polycrystalline AlN films with c-axis inclination of up to 12° could be obtained using the off-center system. Solidly mounted resonators based on the deposited c-axis inclined and vertical AlN films were successfully realized. The frequency responses showed dual-mode resonance characteristics located at 1.12 GHz and 1.87 GHz, corresponding to shear and longitudinal resonant modes, respectively.     

AlN薄膜体声波梯形滤波器的制备与性能分析

用Mason一维等效电路模型模拟了不同级数的梯形体声波滤波器的传输特性.讨论了谐振器级联数对滤波器插入损耗和带外抑制的影响.以AlN薄膜为压电材料,采用微机电系统(MEMS)工艺流程制备了3级梯形结构的滤波器,用扫描电镜照片(SEM)和网络分析仪表征了器件的结构和传输响应特性,测试结果表明,所制备的滤波器结构完整,图形整齐,并得到滤波器的带宽为180 MHz,带外衰减为-10.12 dB,插入损耗为-5.15 dB.     

Advances in pulsed-laser-deposited AIN thin films for high-temperature capping, device passivation, and piezoelectric-based RF MEMS/NEMS resonator applications

In this paper we report recent advances in pulsed-laser-deposited AIN thin films for high-temperature capping of SiC, passivation of SiC-based devices, and fabrication of a piezoelectric MEMS/NEMS resonator on Pt-metallized SiO₂/Si. The AlN films grown using the reactive laser ablation technique were found to be highly stoichiometric, dense with an optical band gap of 6.2 eV, and with a surface smoothness of less than 1 nm. A low-temperature buffer-layer approach was used to reduce the lattice and thermal mismatch strains. The dependence of the quality of AlN thin films and its characteristics as a function of processing parameters are discussed. Due to high crystallinity, near-perfect stoichiometry, and high packing density, pulsed-laser-deposited AlN thin films show a tendency to withstand high temperatures up to 1600°C, and which enables it to be used as an anneal capping layer for SiC wafers for removing ion-implantation damage and dopant activation. The laser-deposited AlN thin films show conformal coverage on SiC-based devices and exhibit an electrical break-down strength of 1.66 MV/cm up to 350°C when used as an insulator in Ni/AlN/SiC metal-insulator-semiconductor (MIS) devices. Pulsed laser deposition (PLD) AlN films grown on Pt/SiO₂/Si (100) substrates for radio-frequency microelectrical and mechanical systems and nanoelectrical and mechanical systems (MEMS and NEMS) demonstrated resonators having high Q values ranging from 8,000 to 17,000 in the frequency range of 2.5–0.45 MHz. AlN thin films were characterized by x-ray diffraction, Rutherford backscattering spectrometry (in normal and oxygen resonance mode), atomic force microscopy, ultraviolet (UV)-visible spectroscopy, and scanning electron microscopy. Applications exploiting characteristics of high bandgap, high bond strength, excellent piezoelectric characteristics, extremely high chemical inertness, high electrical resistivity, high breakdown strength, and high thermal stability of the pulsed-laser-deposited thin films have been discussed in the context of emerging developments of SiC power devices, for high-temperature electronics, and for radio frequency (RF) MEMS.