薄膜体声波谐振器（FBAR）技术的若干问题研究

【作者】 金浩；

【导师】 王德苗；

【作者基本信息】 浙江大学 ， 物理电子学， 2006， 博士

【摘要】 集成化、微型化是无线射频终端的发展趋势,薄膜体声波谐振器(FBAR)作为目前唯一有望集成的射频滤波器技术,正成为国内外研究的热点。与传统的介质滤波器和声表滤波器(SAW)相比,FBAR具有体积小、工作频率高、插入损耗低、带外抑制大、高Q、大功率容量、低温度系数以及良好的抗静电冲击能力和半导体工艺兼容性等优点。 AIN薄膜的制备是FBAR的核心技术,根据实验条件,主要对FBAR器件的建模与分析、AIN薄膜的制备、薄膜材料微波复介电常数的测量与评价以及FBAR器件的设计与实现等四部分内容进行了分析和研究,主要取得了以下成果: 1.提出了一种能普适多种FBAR结构的解析等效电路模型和三维电磁场模型,基于此建立了ADS仿真库,实现了HFSS对FBAR的电声协仿真。用实测数据对上述模型进行了验证,模型仿真所得的S参数曲线与实测曲线谐振频率相近、曲线形状相似,证明了其准确性。 2.在对反应溅射机理进行建模分析的基础上,提出并实现了一种以氮气流量作为控制量、阴极电压作为定位量、能使阴极靶处于金属态与中毒态之间的过渡态、无迟滞现象的高速沉积c轴择优取向AIN薄膜的工艺方法。沉积速率在500W射频功率的情况下达到2.3μm/h,这一实验结果远高于国内研究者所报道的数据,具有重要的实用价值。 3.介质薄膜的微波复介电常数的测试评价是国内外还没有解决的难题,我们发明了一种利用微扰原理对介质薄膜复介电常数进行精确测量的方法与装置,并申请了发明专利。利用该方法测量AIN薄膜的相对介电常数,误差在5%左右。 4.在上述ADS仿真库的基础上提出并设计了由多个谐振器组成的WCDMA零中频非平衡和平衡接收滤波器。仿真结果表明:非平衡滤波器具有良好的发送频带噪声抑制能力,符合WCDMA强Tx干扰信号抑制的需求;平衡滤波器具有很好的共模抑制能力,可减少零中频接收机的二次互调干扰。 5.在双面抛光的(111)硅片上设计并制作了高模FBAR的原型器件。用矢量网络分析仪测得器件的频率分布间隔为22MHz,与理论预测和ADS仿真所得的20 MHz频率问隔较为吻合。 因实验条件和研究经费的制约,未能对设计好的硅反面刻蚀型FBAR进行实际试样的制备,这是论文的缺憾。更多还原

【Abstract】 Thin film bulk acoustic resonator （FBAR） is a breakthrough technology for RF filter. It can replace conventional SAW filter because it provides several prominent advantages such as small size, high Q, high power handling capability, high operating frequency, good temperature stability, and the possibility of being integrated into RFIC （Radio Frequency Integrated Circuits）.Deposition of high-quality A1N thin film is a key to success in FBAR manufacture. Due to the constrain of research conditions, we choose four main parts to study, which include the modeling of FBAR, deposition of AIN thin film, measurement of permittivity of AIN thin film, and the design and implementation of FBAR devices. The main results of this dissertation are listed as follows:1. An equivalent circuit model which is suitable for many kinds of FBAR, such as air-gap, back etched, solid mounted, and overmode type was presented. An electromagnetic model which is suitable for commercial 3D electromagnetic soft was presented. Based on these models, we built up the simulation library of ADS and implemented the acoustic-electromagnetic co-simulation with HFSS. The models were validated by comparison with experimental data.2. Based on the reactive sputtering processes modeling, we provided a new method to get high deposition rate as well as high c-axis oriented for AIN thin film. The proposed method uses the flow of N₂ as control quantity, and the cathode voltage as location quantity. The targets work at transition region between metallic state and poisoned state, and there are no hystereses during the processes. Finally, at 500 W RF power, the deposition rate achieves 2.3 μ m per hour.3. A method and apparatus for complex permittivity measurement of dielectric thin film was proposed. It is based on cavity perturbation theory, and dielectric thin film is used as perturbation quantity. By comparison the frequencies and Q values before and after the perturbation, we can get the permittivity of dielectric thin film. The experimental data show that the precision of this method for A1N thin film is less than 5%. The method and apparatus were applied for patent.4. Designed an unbalanced and balanced Rx filter for WCDMA zero-IF receiver, respectively. The topologies of filters are composed of ladder and lattice topology. The responses of filters both have steep roll-off and deep stop band rejection, and the balanced Rx filter also has good common mode rejection.5. Designed and manufactured the prototype of overmode FBAR on double-side polished （111） silicon wafer. The frequency distribution measured by Vector Network Analyzer （VNA） is similar to that simulated by ADS.We have designed the processes flow and mask for the back-etched type FBAR, butwe did not manufacture it due to the research conditions. It is the biggest shortage of this dissertation.更多还原