晶粒取向和晶界对FeFET电学性能影响的相场模拟

发布时间：2018-11-13 13:40

【摘要】：铁电场效应晶体管(FeFET)存储器因其低功耗、高读写速度、非挥发性、抗辐射、高集成度和非破坏性读出等优点,被认为是最有潜力的下一代存储器之一。铁电薄膜作为FeFET存储器的核心部分,其性能决定了铁电存储器工作的可靠性。相比单晶铁电薄膜,多晶铁电薄膜要更容易制备,且多晶铁电薄膜在实验与实际应用中更为广泛。所以,对多晶铁电薄膜的模拟及其电学性能研究尤为必要。首先,晶粒取向分布和晶界厚度对多晶铁电薄膜的铁电性能具有一定的影响,进而会对多晶铁电薄膜的电学性能产生重要影响。其次,多晶铁电薄膜晶界处存在电荷聚集,将导致内建电场的产生,对多晶铁电薄膜的性能会产生影响。本文以金属/铁电/绝缘体/硅(MFIS)结构的FeFET为研究对象,运用相场方法结合金属/氧化物/半导体(MOS)场效应晶体管的基本器件方程,建立了FeFET的电学性能研究模型,主要研究了BaTiO3多晶铁电薄膜的晶粒取向和晶界对其FeFET电学性能的影响,具体研究内容和结果如下:(1)建立了多晶铁电薄膜的相场模型,研究了晶粒取向分布和晶界厚度等因素对多晶铁电薄膜铁电性能的影响。结果表明:晶粒取向的随机分布会导致BaTiO3多晶铁电薄膜的剩余极化减小,矫顽场减小;晶界会导致BaTiO3多晶铁电薄膜矫顽场的减小,随着晶界厚度的增加,BaTiO3多晶铁电薄膜的剩余极化逐渐减小。(2)利用所建立的多晶铁电薄膜的相场模型基础,考虑晶界处的电荷聚集,研究了晶界处电荷聚集对多晶铁电薄膜铁电性能的影响。结果表明:晶界处电荷聚集会在晶粒内部形成内建电场,影响BaTiO3多晶铁电薄膜的畴结构和畴变过程;随着电荷聚集强度的增大,铁电薄膜的剩余极化逐渐减小,矫顽场逐渐减小。(3)将多晶铁电薄膜的相场模型与标准MOS场效应晶体管的基本器件方程相结合,研究了晶粒取向、晶界厚度和晶界处电荷聚集等因素对FeFET电学性能的影响。结果表明:晶粒取向的随机分布会导致FeFET的剩余极化减小,存储窗口减小,开态源漏电流I_(ds)减小,关态源漏电流I_(ds)增大;随着晶界厚度的增加,FeFET的剩余极化逐渐降低,存储窗口减小,开态源漏电流I_(ds)减小,关态源漏电流I_(ds)增大;随着晶界处电荷聚集强度的增大,FeFET的剩余极化逐渐降低,存储窗口逐渐减小,开态源漏电流I_(ds)逐渐减小,关态源漏电流I_(ds)逐渐增大。
[Abstract]:Ferroelectric field effect transistor (FeFET) memory is considered to be one of the most promising next generation memory due to its advantages of low power consumption, high read / write speed, non-volatile, radiation resistant, high integration and non-destructive readout. Ferroelectric thin film is the core part of FeFET memory, and its performance determines the reliability of ferroelectric memory. Compared with single crystal ferroelectric thin film, polycrystalline ferroelectric thin film is easier to be prepared, and the polycrystalline ferroelectric thin film is widely used in experiment and practice. Therefore, it is necessary to study the simulation and electrical properties of polycrystalline ferroelectric thin films. Firstly, the distribution of grain orientation and the thickness of grain boundary have a certain influence on the ferroelectric properties of polycrystalline ferroelectric thin films, and then have an important effect on the electrical properties of polycrystalline ferroelectric thin films. Secondly, the charge accumulation at the grain boundary of the polycrystalline ferroelectric thin films will lead to the generation of the built-in electric field, which will affect the properties of the polycrystalline ferroelectric thin films. In this paper, the FeFET with metal / ferroelectric / insulator / silicon (MFIS) structure is taken as the research object, and the electrical performance model of FeFET is established by combining the basic device equation of metal / oxide / semiconductor (MOS) field effect transistor with the phase field method. The effects of grain orientation and grain boundary on the electrical properties of BaTiO3 polycrystalline ferroelectric thin films are studied. The main contents and results are as follows: (1) the phase field model of polycrystalline ferroelectric thin films is established. The effects of grain orientation distribution and grain boundary thickness on the ferroelectric properties of polycrystalline ferroelectric thin films were studied. The results show that the random distribution of grain orientation leads to the decrease of residual polarization and coercive field of BaTiO3 polycrystalline ferroelectric thin films. Grain boundary will lead to the decrease of coercive field of BaTiO3 polycrystalline ferroelectric thin films. With the increase of grain boundary thickness, the residual polarization of BaTiO3 polycrystalline ferroelectric thin films will gradually decrease. (2) based on the phase field model of polycrystalline ferroelectric thin films, The effect of charge aggregation at grain boundary on ferroelectric properties of polycrystalline ferroelectric thin films was studied. The results show that the charge accumulation at grain boundary will form an internal electric field in the grain, which will affect the domain structure and domain switching process of BaTiO3 polycrystalline ferroelectric thin films. With the increase of charge aggregation intensity, the residual polarization and coercive field of ferroelectric thin films decrease gradually. (3) the phase field model of polycrystalline ferroelectric thin films is combined with the basic device equations of standard MOS field-effect transistors. The effects of grain orientation, grain boundary thickness and charge aggregation at grain boundary on the electrical properties of FeFET were investigated. The results show that the random distribution of grain orientation results in the decrease of residual polarization of FeFET, the decrease of storage window, the decrease of open source leakage current I _ (ds), and the increase of off state source drain current I _ (ds). With the increase of grain boundary thickness, the residual polarization of FeFET decreases gradually, the storage window decreases, the open source leakage current I _ (ds) decreases, and the off-state source drain current I _ (ds) increases. With the increase of charge aggregation intensity at grain boundaries, the residual polarization of FeFET decreases, the storage window decreases, the open source drain current I _ (ds) decreases, and the off-state source drain current I _ (ds) increases.
【学位授予单位】：湘潭大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TN386;TP333;TM221

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