PHT铁电薄膜的制备与性能研究

发布时间：2018-03-02 11:50

  本文选题：PHT　切入点：铁电　出处：《电子科技大学》2015年硕士论文　论文类型：学位论文

【摘要】：铁电薄膜材料是具有介电、压电、热释电、铁电等性质的功能材料,被广泛应用于集成电子学、微电子学、微机电系统、光电子学等重要领域。铁电薄膜是非易失性随机存储器(NVRAM)的重要组成部分。随着现代科学技术和信息处理技术的高速发展,对NVRAM是的存储密度、稳定性及使用寿命都有了越来越高的要求。虽然传统的铁电材料(PZT、SBT等)的制备技术已很完善,但其在工业应用方面还存在一些问题,如铁电疲劳、制备温度高等。探索可用于NVRAM的新型高性能铁电材料越来越重要。钙钛矿结构Pb(HfxTi1-x)O3(PHT)铁电薄膜具剩余极化强度高、矫顽场低、介电常数大、成分可调、抗疲劳特性好等优点,可作为NVRAM的候选铁电材料。本论文以钙钛矿结构的铁电薄膜PHT为研究对象,对PHT与半导体材料(Si、GaN)的集成结构进行了系统的研究。主要开展了以下工作:探索Pt(111)/TiO2/SiO2/Si衬底上PHT薄膜的最优生长工艺;在Al2O3衬底上研究缓冲层对PHT薄膜微观结构及性能的影响,并研究不同底电极对PHT薄膜的影响;初步探索铁电薄膜PHT与半导体GaN集成结构的性能。1、首先在Pt/TiO2/SiO2/Si衬底上采用PLD法制备PHT薄膜,探索PHT的最优制备工艺。制备铁电电容结构(MIM),研究PHT薄膜的本征电学性能。研究发现,生长过程中氧分压和生长温度对PHT薄膜的择优取向、铁电极化及漏电流都有显著的影响。然后引入低温自缓冲层技术,有效改善薄膜的微观结构和电学性能。此外,本论文还对比了不同生长温度的自缓冲层对PHT薄膜的微观结构及电学性能的影响,发现插入300℃自缓冲层得到沿(111)取向的高质量外延PHT薄膜,薄膜晶粒大小均匀,且表面平整、结构致密。与600℃直接沉积的PHT薄膜相比,300℃自缓冲层下外延薄膜的漏电流密度降低了3-4个数量级,剩余极化强度提高到63μC/cm2,矫顽场强降低至190 kV/cm,抗疲劳特性也得到了显著改善。2、对比研究了Al2O3衬底上直接和用MgO缓冲沉积PHT薄膜的微观结构,发现插入MgO缓冲层可使得PHT薄膜沿(111)择优取向生长,且薄膜结晶质量良好,表面平整致密。然后对比Pt和SRO底电极对Al2O3衬底上沉积的PHT薄膜的微结构与电学性能的影响,发现由于SRO与PHT都为钙钛矿结构且具有相似的晶格常数,且SRO中的氧原子对PHT薄膜中的氧空位起到一定的补偿作用,可以减少薄膜中的缺陷,SRO下电极上沉积的PHT薄膜具有更好的绝缘特性、更高的剩余极化强度、更强的抗疲劳特性。最后选用SRO为底电极,研究了MgO缓冲层对PHT薄膜电学性能的影响。3、对GaN衬底上制备的PHT薄膜进行了研究。发现在MgO缓冲作用下实现了PHT(111)薄膜在GaN衬底上的外延生长,且延续了MgO在GaN上生长的外延关系:PHT(111)//MgO(111)//GaN(0002);PHT[1-10]//MgO[1-10]//GaN[11-20]。分别制备Au/Ni/PHT/GaN(MFS)和Au/Ni/PHT/MgO/GaN(MFIS)结构并对其电学性能进行测试。
[Abstract]:Ferroelectric thin films are functional materials with dielectric, piezoelectric, pyroelectric and ferroelectric properties. They are widely used in integrated electronics, microelectronics, micro-electromechanical systems, etc. Ferroelectric thin film is an important component of nonvolatile random access memory (NVRAM). With the rapid development of modern science and technology and information processing technology, NVRAM is the storage density. Although the preparation technology of the traditional ferroelectric material PZT / SBT is very perfect, there are still some problems in its industrial application, such as ferroelectric fatigue. The preparation temperature is high. It is more and more important to explore new high performance ferroelectric materials that can be used in NVRAM. The perovskite structure PbHfxTi1-xO3PHTs have the advantages of high remanent polarization, low coercive field, large dielectric constant, adjustable composition and good fatigue resistance, etc. In this thesis, perovskite structure ferroelectric thin film PHT is used as the research object. In this paper, the integrated structure of PHT and semiconductor material (SiGN) is systematically studied. The main work is as follows: to explore the optimal growth process of PHT films on Pt(111)/TiO2/SiO2/Si substrates, to study the effect of buffer layer on the microstructure and properties of PHT films on Al2O3 substrates, and to study the effect of buffer layer on the microstructure and properties of PHT films. The effects of different bottom electrodes on PHT thin films were studied, and the properties of the integrated structure of ferroelectric film PHT and semiconductor GaN were investigated. Firstly, PHT thin films were prepared on Pt/TiO2/SiO2/Si substrates by PLD method. The optimum preparation process of PHT was explored. The ferroelectric capacitance structure was prepared and the intrinsic electrical properties of PHT thin films were studied. It was found that oxygen partial pressure and growth temperature had preferential orientation on PHT films during the growth process. Iron electrode and leakage current have significant effects. Then, the low temperature self-buffer layer technology is introduced to effectively improve the microstructure and electrical properties of the film. The effects of self-buffer layers at different growth temperatures on the microstructure and electrical properties of PHT thin films were also compared. It was found that the high quality epitaxial PHT thin films with high quality orientation were obtained by inserting the self-buffer layers at 300 鈩，

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