金属氧化物基阻变存储器中导电细丝的调控与机理研究

Resistive random access memory (RRAM) device is a promising solution for next-generation nonvolatile memory applications due to its simple device structure, high-speed operation, low power consumption, and remarkable compatibility with the CMOS process. However, It is really difficult to control the composition, density, distribution and dynamic processes of the conductive filaments (CFs) in RRAM devices. Moreover, the regulation approaches and the corresponding physics mechanisms of the CFs are still under controversial, which limit the commercial applications of the RRAM devices significantly. In this project, we try to modulate the formation and rupture processes of the CFs in metal oxide based RRAM devices by optimizing the devices stacks, controlling the fabrication techniques and utilizing proper post-deposition treatments. The detailed mechanisms of the formation/rupture processes will be clarified by combining the microstructure analysis and electronic measurements. Simultaneously, the interaction between the cell performances and the electrodes, fabrication approaches, as well as the defects stations will be thoroughly studied. Eventually, the modulating mechanisms of the CFs will be explained on the basis of the experiment results. The current investigation can promote our understanding about nucleation and growth processes of the CFs in RRAMs. The achievements will benefit not only for finding the effective strategies to promote the properties, but also for realizing the controllable fabrication of the RRAM memory devices. It can also provide scientific guidelines for commercial applications of the RRAMs.

金属氧化物基阻变存储器(RRAM)由于具有结构简单、擦写速度快、功耗低以及与CMOS技术兼容等优点被认为是下一代非易失性存储器的有力竞争者。然而，RRAM器件中导电细丝的组成、密度、形貌、分布以及动力学过程等较难控制，并且导电细丝的调控方法和物理机制仍不够清晰，这极大地限制了RRAM走向商业应用。针对这一问题，本项目以金属氧化物基RRAM为研究对象，从器件结构优化、制备工艺参数控制以及适当的后处理工艺等方面出发，调控导电细丝的形成与断裂过程，进而改进器件的阻变性能。同时结合微结构表征手段与宏观电学性能分析，深入研究阻变过程中导电细丝的形成与断裂机理，阐明RRAM性能与电极材料、制备工艺以及缺陷状态等因素之间的关系，深化对导电细丝可控成核与生长过程的认识，为寻求优化阻变性能的具体方案提供理论依据，为实现阻变性能的可控调节并最终实现RRAM的商用化奠定基础和提供知识积累。

金属氧化物基RRAM器件的性能不仅与材料有关，还和所使用的电极材料、器件结构、制备工艺以及杂质、缺陷状态等有很大的关系。本项目从器件结构优化(优选电极材料，插入层设计等)到中间制备工艺参数调控以及结合适当的后处理过程等多个方面综合考虑，探索了金属氧化物中的导电细丝与器件电学性能之间的内在关系。通过选择不同的电极材料，研究了导电细丝类型与阻变稳定性之间的关系，发现基于氧空位细丝的器件性能更为优异。通过限流调控及插入层设计等方法有效的调节了导电细丝的产生与断裂过程及其稳定性。基于金属型导电细丝的器件，发现了细丝有关的易失性与非易失性之间的转变，有望分别应用于选通器件及阻变器件。通过退火工艺的改变，研究了后处理对阻变性能影响，发现适当的后退火气氛会显著改善器件的性能。此外，通过采用原子层沉积方法制备致密超薄的Al2O3器件，从导电细丝的调控角度对金属氧化物基阻变器件的多值存储特性进行了一定的探索。最后，结合界面层的设计，研究了ZnO压电功能层对阻变器件性能的影响。本项目的研究，对进一步提高器件的性能及未来继续优化器件的稳定性与可靠性具有一定的参考意义。