残余应力及界面效应对FeFET电学性能影响的相场模拟

发布时间：2018-04-04 16:00

本文选题：相场理论　切入点：FeFET　出处：《湘潭大学》2015年硕士论文

【摘要】：铁电场效应晶体管(Fe FET)以其高的读写速度,低功耗以及非破坏性读出等特点成为了新型存储器的有力竞争者之一。铁电薄膜作为FeFET的栅介质层,其性能对铁电场效应晶体管的电学特性有着重要影响。研究表明铁电薄膜中的残余应力以及界面效应对铁电薄膜的性能有很大的影响,而FeFET的结构导致其铁电层中存在着较大的残余应力以及界面效应。因此,研究残余应力以及界面效应对Fe FET电学性能的影响,将有助于提高FeFET的使用寿命。本文通过相场方法模拟了残余应力作用下铁电薄膜的极化演化,研究了残余应力及界面效应对FeFET电学性能的影响。主要有以下几方面的结果:1.采用相场理论,基于修正的时变金兹堡-朗道(TDGL)方程,模拟了残余应力作用下铁电畴的极化演化。结果表明,在平行于膜面的方向施加残余压应力,随着时间的增加,垂直于膜面的极化增强,平行于膜面的极化减弱,形成一个垂直于膜面的单畴。在平行于膜面的方向施加残余拉应力,畴壁沿垂直膜面的方向运动,平行于膜面的极化增强,垂直于膜面的极化减弱,最终形成一个平行于膜面的单畴。2.将FeFET的相场模型与标准MOSFET的基本器件方程结合,研究了残余应力对金属-铁电层-绝缘层-半导体(MFIS)结构的Fe FET的电滞回线(P-V)、C-V特性以及输出特性(I-V)等电学性能的影响。结果表明,随着残余压应力的增加,FeFET的剩余极化以及矫顽场逐渐增大;存储窗口逐渐增大,开态源漏电流和关态源漏电流逐渐增大。随着残余拉应力的增加,FeFET的剩余极化以及矫顽场逐渐减小;存储窗口逐渐减小,开态源漏电流和关态源漏电流逐渐减小。3.考虑界面效应,从界面电场和界面应变两个方面研究了界面效应对MFIS结构的FeFET的电学性能的影响。结果表明,随着界面电场的增大,FeFET正的剩余极化值逐渐减小,电滞回线发生偏移,存储窗口沿着扫描电压增大的方向发生偏移,开态源漏电流和关态源漏电流先增大后减小。当界面应变由压应变到张应变的转变过程中,FeFET的剩余极化以及矫顽场逐渐减小,存储窗口逐渐减小,开态源漏电流逐渐减小,关态源漏电流逐渐增大。
[Abstract]:Ferroelectric field effect transistor (FET) has become one of the most powerful contenders for new memory because of its high read / write speed, low power consumption and nondestructive readout.As the gate dielectric layer of FeFET, the performance of ferroelectric thin film has an important influence on the electrical properties of ferroelectric field effect transistors.The results show that the residual stress and interfacial effect in ferroelectric thin films have great influence on the properties of ferroelectric thin films, while the structure of FeFET leads to the existence of large residual stresses and interfacial effects in the ferroelectric layers.Therefore, the study of the influence of residual stress and interfacial effect on the electrical properties of Fe FET will help to improve the service life of FeFET.In this paper, the polarization evolution of ferroelectric thin films under residual stress is simulated by phase field method, and the effects of residual stress and interface effect on the electrical properties of FeFET are studied.The main results are as follows: 1.The polarization evolution of ferroelectric domains under residual stress is simulated by using phase field theory based on the modified time-varying Kingsbauer-Landau TDGL equation.The results show that when the residual compressive stress is applied in the direction parallel to the film surface, with the increase of time, the polarization perpendicular to the film surface increases, and the polarization parallel to the film surface weakens, forming a single domain perpendicular to the film surface.When the residual tensile stress is applied in the direction parallel to the film surface, the domain wall moves along the direction of the vertical film surface, and the polarization increases parallel to the film surface, and the polarization perpendicular to the film surface weakens, resulting in the formation of a single domain .2parallel to the film surface.Combining the phase field model of FeFET with the basic device equation of standard MOSFET, the effect of residual stress on the electrical properties of Fe FET with metal-ferroelectric-insulator-semiconductor structure has been studied. The electrohysteretic loop (P-V) C-V characteristics and the output characteristics (I-V) of Fe FET have been investigated.The results show that the residual polarization and coercive field of FeFET increase with the increase of residual compressive stress, and the open source drain current and the off source drain current increase gradually with the increase of storage window.With the increase of residual tensile stress, the residual polarization and coercive field of FeFET decrease gradually, and the storage window decreases, the open source drain current and the off source drain current decrease gradually.Considering the interface effect, the effect of interface effect on the electrical properties of FeFET with MFIS structure was studied from two aspects: interface electric field and interface strain.The results show that with the increase of the interface electric field, the positive residual polarization value of FeFET decreases gradually, the hysteresis loop shifts, the storage window shifts along the direction of the increasing scanning voltage, the open source leakage current and the off state source drain current first increase and then decrease.During the transition of interface strain from compressive strain to tensile strain, the residual polarization and coercive field of FeFET gradually decrease, the storage window decreases, the open source drain current decreases, and the off source drain current increases.
【学位授予单位】：湘潭大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TB34;TB383.2

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