存储器用多晶铁电薄膜晶界与畴变耦合机理的有限元研究

Ferroelectric random access memories (FeRAMs) are widely used in the area of information technology and national defense security due to their outstanding features. Actually, polycrystalline ferroelectric thin films are the most used thin films in the FeRAM because of their comparatively easier preparation processes and lower cost. However, the grain boundaries play important roles in the property of the polycrystalline ferroelectric thin films. In addition, domain switching results in nonlinear ferroelectricity of ferroelectric materials and reflects the macroscopic responses of ferroelectric thin films to the external field. Moreover, the grain boundaries and the domain switching have electromechanical coupling effects. So far, their coupling mechanisms have rarely been studied. The project will focus on the coupling between the grain boundary and domain switching, and the coupling effects on the properties of FeRAM. On the one hand, a finite element method will be developed to study the domain switching properties under the grain boundary of polycrystalline ferroelectric thin films. A finite element model will be established to analyze domain switching in the polycrystalline ferroelectric thin films. And then, it is expected that the intrinsic mechanism of the coupling between the grain boundary and domain switching is revealed. On the other hand, combined the theory of semiconductor device, a relationship of the coupling and the properties of the polycrystalline ferroelectric thin film will be established. Then, the grain boundary is understood and controlled the domain switching to optimize the properties of the polycrystalline ferroelectric thin film. It is desirable to obtain the high properties of the polycrystalline ferroelectric film in favor of the performance of ferroelectric thin film and memory.

铁电存储器由于其突出的性能，在我国的信息技术领域和国防领域有广阔的应用前景。多晶铁电薄膜具有制备工艺简单、生产成本低廉等特点而广泛的应用于铁电存储器中。而多晶铁电薄膜的晶界是影响其性能的关键。畴变是多晶铁电薄膜非线性本构行为的微观物理机制，主宰了铁电存储器的性能。晶界与畴变存在耦合效应，本质是力-电耦合问题，而目前晶界与畴变耦合机理尚不明确。本项目以存储器用多晶铁电薄膜为研究对象，从理论上研究晶界与畴变的耦合机理及其对存储器性能的影响。一方面，建立存储器用多晶铁电薄膜畴变模拟的有限元模型，使用有限元方法研究其畴变行为，掌握存储器用多晶铁电薄膜晶界与畴变的耦合机理；另一方面，结合半导体器件理论，研究晶界与畴变耦合对存储器用多晶铁电薄膜性能的影响，理论上掌握利用晶界与畴变的耦合来优化存储器用多晶铁电薄膜性能的方法，为制备性能优异的存储器用多晶铁电薄膜提供理论指导。

铁电存储器由于其突出的性能，在我国的信息技术领域和国防领域有广阔的应用前景。铁电薄膜作为铁电存储器的核心，其性能决定了铁电存储器的可靠性。和单晶铁电薄膜相比，多晶铁电薄膜具有制备工艺简单、生产成本低廉等特点而广泛的应用于铁电存储器。晶界作为多晶铁电薄膜的重要组成部分，对存储器的性能有较大的影响，畴变是多晶铁电薄膜本构行为的微观物理机制，主宰了铁电存储器的性能。晶界与畴变耦合机理的研究对存储器用多晶铁电薄膜性能的优化具有重要的指导意义。基于此，首先，建立了存储器用多晶铁电薄膜畴变模拟的有限元模型，掌握了晶粒取向、晶界厚度等因素对多晶铁电薄膜畴结构及其在外场下的演变；其次，考虑了多晶铁电薄膜晶界处的电荷聚集，掌握了晶界电荷聚集对多晶铁电薄膜性能影响的规律；最后，将多晶铁电薄膜畴变模拟的模型与标准场效应晶体管器件方程相结合，研究了晶粒取向、晶界厚度和晶界电荷聚集等对铁电场效应晶体管电学性能和存储特性的影响。通过对晶界与畴变耦合机理的研究，掌握了晶界与畴变耦合对多晶铁电薄膜性能影响的规律，以及利用晶界与畴变耦合来调控存储器用多晶铁电薄膜性能的方法，为铁电存储器的研制和开发提供理论指导。