【作者】 王敏锐；

【导师】 王立鼎； 王兢；

【作者基本信息】 大连理工大学 ， 机械电子工程， 2007， 博士

【摘要】 用MEMS技术探索制作的悬臂梁式ZnO薄膜压电微力传感／执行系统，具有微型化、灵敏度高，能实现传感器／执行器的功能集成以及系统智能化等诸多优点。但是，由于悬臂梁式ZnO薄膜压电微力传感／执行系统存在悬空结构，有些工艺需要在高温下进行，使压电传感器／执行器与CMOS电路的集成制备存在很大的困难。本文以与CMOS电路工艺兼容的ZnO薄膜压电微力传感器／执行器为研究对象，对ZnO压电薄膜的制备及性能改进、传感器／执行器的结构设计、与COMS电路工艺兼容的器件制备以及器件的性能测试四个方面进行了系统的研究。1．探索了溶胶—凝胶技术(Sol—Gel)制备ZnO压电薄膜的方法。深入研究了Sol—Gel法的主要工艺参数对薄膜微结构和电性能的影响规律，优化了薄膜制备工艺参数，制备了致密、无裂纹的ZnO薄膜。由于Sol—Gel法制备的纯ZnO薄膜电阻率低，无法作为压电薄膜使用。本文采用掺Mn的方法，不仅将ZnO薄膜的电阻率提高了9个数量级，使薄膜满足了作为压电薄膜使用时的高电阻性要求，而且将压电薄膜的制备温度降低为450℃。首次成功的采用Sol—Gel法制备了掺Mn的ZnO压电薄膜，并基本解决了ZnO压电薄膜与CMOS电路集成制备的温度兼容问题。2．设计了两种类型的ZnO薄膜压电微力传感器／执行器。(1)设计了一种悬臂梁结构的传统式压电微力传感器／执行器，并建立了传感器的力-电荷量转换效率优化模型，优化了压电微悬臂梁的Si层和ZnO薄膜的厚度，提高了器件的力-电荷量转换效率。(2)设计了一种新型的体声波谐振式微力传感／压电执行集成系统，建立了传感器的力-谐振频率偏移转换模型。与传统式压电微力传感器／执行器不同，此微力传感／执行集成系统，同时具备了静态微力测量和压电执行功能。而且将传感器和执行器制作在同一层压电薄膜上，避免了双压电层结构式自激励—自检测压电微力传感／执行集成系统通常存在的压电层之间复杂的场耦合问题。3．研究了基于Sol—Gel法制备ZnO压电薄膜技术的压电微悬臂梁的微加工新工艺。通过降低结构支撑层的制备温度，进一步解决了ZnO薄膜压电微悬臂梁和CMOS电路集成制备的温度兼容问题；采用剥离法制备上下电极和正反两面干法刻蚀体硅加工释放压电微悬臂梁的技术，解决了集成制备过程中的K~+污染和腐蚀兼容问题；分析并解决了ZnO压电薄膜制备过程中，剥离法制备的Ti／Pt底电极反复起泡的关键技术难题。采用本文开发的微加工工艺，成功的制备了两种压电微力传感器／执行器，为将来压电微悬臂梁和CMOS电路的集成制备打下了良好的工艺基础。4．测量了本文制作的两种压电微力传感器／执行器的基本性能。结果表明，Sol—Gel法制备的掺Mn的ZnO压电薄膜具有良好的压电性。研制的传统式微力传感器／执行器的灵敏度和执行能力分别达到28.6fC／μN和0.042μN／V，体声波谐振式微力传感器的灵敏度约为8.285kHz／μN。更多还原

【Abstract】 A ZnO thin film piezoelectric micro force Sensor/actuator system chip （SOC） has two primary benefits. First, the piezoelectric micro force sensor/actuator provides with micromation, high frequency response, wide frequency application ranges and high sensitivity. A second advantage is that the piezoelectric micro force sensor/actuator could have the capabilities of the mutli-function integration, arraying and intelligentizing owing to the integration of CMOS circuits. However, there are a host of problems when ZnO piezoelectric thin film is applied in micromaching process. The studies of ZnO thin film piezoelectric micro force sensor/actuator and the integration with CMOS electronics are still in initiate stage. In this thesis, ZnO thin film piezoelectric micro force sensor/actuators are systematically investigated in terms of the preparation, characterization and performance improvement of the films, and the design, fabrication integration with CMOS electronics and testing of the micro force sensor/actuator.The preparations of ZnO thin films by Sol-Gel method were studied. The influences of process parameters （preheating temperature and annealing temperature） of Sol-Gel technique on the microstructures and electric characteristics were investigated, and the optimal process parameters were achieved. It was found that the resistive of pure ZnO thin film prepared by Sol-Gel method was low, which limited the ZnO film to be act as piezoelectric thin film. Aiming to improve performances of ZnO thin film and realize the integrated fabrication with CMOS electronics, the Mn doping experiments were performed. The resistances of at.1% Mn-doped ZnO film （1 micro-meter thickness） increased to the level of 10¹⁰Ω, which made the ZnO films prepared by Sol-Gel satisfy the high resistive requirement as piezoelectric film. Furthermore, the doping of at.1% Mn （CH₃COO）₂ decreased the annealing temperature to form preferred c-axis orientation, which made it possible to integrated fabrication of ZnO thin films prepared by Sol-Gel with CMOS electronics.Two kinds of sensor/actuators were designed. Firstly, a conventional piezoelectric micro force sensor/actuator based micro-cantilever structure was designed. The force-charges coupling mode of device were deduced. Then, the model was as a design tool for investigating the optimal film thickness of piezoelectric multimorphs to improving the sensitivity of micro force sensors. A novel ZnO thin film piezoelectric micro force sensor based on bulk acoustic resonator with micro-cantilever structure, which was integrated with actuating functions, was proposed to measure static force and simply the fabricating process. The relationship of resonator frequrency shift and force on the device was deduced.Aiming to improve the IC-compatibility between the micromachining process of piezoelectric micro cantilever and post-CMOS integrated method, a modified micromachining procedure of piezoelectric micro device was proposed, and the key processes were studied. Two kinds of ZnO thin film piezoelectric micro force sensors/actuators were fabricated successfully. By using the silicon substrate as strcture layer of micro cantilever, using ICP to release micro cantilever and using lift-off method to prepare Ti/Pt bottom electode, the problems of K⁺ pollution, etch compatibility and temperature compatibility were solved. The bubble problem happened to bottom electrode in preparing ZnO by Sol-Gel technique was solved.The measurements of the two kinds of piezoelectric micro force sensors/actuators were carried out. The piezoelectric constant d₃₁ of ZnO piezoelectric film prepared by Sol-Gel method is 0.4366pC/N, which is measured by the first time and an original contribution. The force sensitivity and actuating force of conventional piezoelectric micro force sensors/actuators are 28.6fC/μN and 0.042μN/V, respectively. The force sensitivity of bulk acoustic resonator micro force sensor is about 8.285kHz/μN.更多还原