【作者】 刘红梅；

【导师】 曹茂盛；

【作者基本信息】 哈尔滨工程大学 ， 材料学， 2009， 博士

【摘要】 新型、高性能MEMS器件对所用材料的结构和性能有很高要求。PZT压电薄膜以其优异的介电、铁电和压电性能,成为MEMS应用的研究热点。本文利用改进的溶胶.凝胶技术在Au/Cr/SiO₂/Si基片上制备了不同厚度的PZT压电薄膜,得到了大于4μm的PZT厚膜,并以硅基PZT厚膜采用半导体微细加工工艺制备了PZT压电方式驱动悬臂梁;系统地研究了PZT厚膜的制备工艺、微结构和介电、铁电、压电性能及它们的相关性能。论文的主要工作包括:硅基PZT压电多层薄膜的制备工艺、压电悬臂梁的优化设计以及PZT压电薄膜悬臂梁的制作工艺相关实验研究。基于改进的溶胶-凝胶法研究PZT厚膜的制备工艺,在传统Sol-Gel法基础上提出一种改进0-3复合法,即先将0维的PZT超细粉末混合到的PZT前驱液中,形成均匀、稳定的浆料,在Au/Cr/SiO₂/Si衬底上制备了PZT压电厚膜。直接利用0-3复合法所获得PZT浆料进行成膜,薄膜的表面粗糙,不利于在MEMS器件中使用,因此提出采用PZT溶胶与在PZT溶胶中加入PZT微粉形成的浆料并交替涂覆薄膜的方法,并通过添加聚乙烯吡咯烷酮（PVP）抑制薄膜开裂,所获得薄膜表面平整、无裂纹,厚度可达4μm。经多次重复后,还可以提高PZT厚膜的厚度。采用此法制备的PZT厚膜,突破了PZT厚度的限制,并且重复性好、使PZT厚膜表面质量得到改善。通过硅基PZT压电多层薄膜的制备工艺系统实验研究,得到了PZT厚膜的介电、铁电和压电性能随厚度的变化规律。采用负载法测量了PZT厚膜（4μm）的最大压电特性常数d₃₃为201pC/N;采用浮力法测量得到PZT厚膜的体积密度为4.31g/cm³;PZT厚膜的最大介电常数为808,在25V电压下,PZT厚膜的剩余极化强度Pr为60μC/cm²,矫顽场Ec为23kV/cm。测试结果表明:在Au/Cr/SiO₂/Si结构上PZT厚膜具有较好的压电、铁电、介电特性。利用压电方程,推导了硅基PZT悬臂梁弯曲位移的表达式,同时利用Intellisuite软件对硅基PZT压电悬臂梁结构进行了优化设计。分析了PZT薄膜的厚度、单晶硅的厚度、悬臂梁的长度、输入电压等因素对PZT压电悬臂梁弯曲位移影响,讨论了PZT压电悬臂梁频率特性,优化了PZT压电悬臂梁结构。模拟得到的优化结构参数为硅基PZT压电薄膜悬臂梁结构在MEMS微执行器中的应用提供了有价值的参考依据。采用氧化、光刻、刻蚀等MEMS技术和改进的Sol-Gel工艺制备了硅基PZT压电薄膜悬臂梁结构。实现了PZT薄膜的制备技术与MEMS技术的兼容问题。最后对硅基PZT压电悬臂梁进行特性测试,利用非接触光技术测量了硅基PZT压电悬臂梁的动态弯曲位移和谐振频率的关系,测量结果与模拟结果相吻合,确定了硅基PZT压电悬臂梁的谐振频率。更多还原

【Abstract】 The materials that the new and advantage performance MEMS devices constitute require high reliability with the structures and properties. That is reason why the piezoelectric PZT thin films have paid much more attentions in MEMS applications is those excellent properties for their dielectric, ferroelectric and piezoelectric. In this thesis, the piezoelectric PZT thick films with different thicknesses were prepared on Au/Cr/SiO₂/Si substrates by a sol-gel technique and the max thickness obtained is about 4μm. The silicon micro-cantilevers based on the PZT/Au/Cr/SiO₂/Si multilayer structures were fabricated through semiconductor min-machining process. The cantilevers fabricated processing and microstructures of the PZT thick films were investigated systematically, and their relationships between dielectric, ferroelectric and piezoelectric properties were confirmed. The fabrication processes of PZT films, the optimizing design for silicon-based PZT thick film and compatible processes of cantilevers with PZT thick films were investigated experimentally and theoretically.An improved method have been gained by ameliorate traditional Sol-Gel process, i.e., 0-3 mixing method, which is to prepare PZT ferroelectric membrane on Au/Ti/SiO₂/Si substrates. In this processes, zero-dimensional PZT nano-powder was firstly mixed with three-dimensional PZT precursory solution. Then the uniform and stable slurry was formed on Au/Cr/SiO₂/Si substrates by a spinning technique. If the films were fabricated by slurry directly, the surfaces will appeared roughly, and it is disadvantage to the MEMS device fabricating. So we presented a method that PZT Sol-Gel and the slurry mixed PZT powder were coated on the membrane alternately, and poly vinylpyrrolidine was simultaneously added. The thickness of the membrane was up to 4μm and no crackle was found in its surface. The thickness could be increased by the repetitious process, which overcomes the limit of membrane thickness and enhance the quality of the surface. The relationships of dielectric, ferroelectric and piezoelectric properties between the thicknesses of films were given by process studied systematically. The maximal piezoelectric constant d₃₃ of the films was 201pC/N that obtained by the cantilever beam load method, the maximal volume density was 4.31g/cm³ tested by buoyancy method, and the maximal dielectric constant was 808. The remanent polarization Pr and the coercive field Ec of PZT thick films were up to 60μC/cm² and 23kV/cm at 25V respectively. The above results demonstrate that the silicon-based PZT thick films have been provided with piezoelectric, ferroelectric and dielectric capacities property well.The expression of the resonance frequency and deflection displacement micro-cantilever were deduced systematically according piezoelectricity equation. The software Intellisuite was used to optimize the driving structure of the silicon-based PZT thick films. The factors influenced on the displacement and frequency characteristics of the cantilever, such as the thicknesses of PZT films and silicon films, length of cantilever, input voltage and so on, were also analyzed in order to determine the optimal structures of cantilever. The structure parameters of simulation provided important function on the micro-actuators fabricating.The new structure of PZT piezoelectric cantilever was fabricated by an improved Sol-Gel method and the MEMS technique including thermal oxidation, optical lithography and hydro-etching. Thus the problem of compatibility between piezoelectric thick films driving and MEMS processes was resolved.In addition, the characteristics of PZT piezoelectric cantilever were tested. The relationships between dynamic deflection displacement and resonance frequencies were measured by non-touch optical methods, and resonant frequency of PZT piezoelectric cantilever was also determined.更多还原