双极性阻变存储器与金属氧化物二极管集成1D1R存储技术研究

Metal-oxide-based one diode and one resistor (1D1R) structure is considered as one of the most promising applications of resistive switching random access memory (RRAM) due to its potential in good scalability, excellent compatibility with CMOS technology, without cross-talk interference in cross-bar array, and 3D high-density integration. Up to now, almost all 1D1R RRAM structures are evaluated with unipolar RRAM devices because the current flow through a conventional diode under a reverse bias condition is extremely low. However, the resistive switching characteristics of a bipolar RRAM are generally much better than that of a unipolar RRAM. Considering the more superior resistive switching characteristics of bipolar RRAM, in this project, we will focus on how to achieve the integration of bipolar RRAM with metal-oxide-based diode. We will carefully investigate the impact of material composition, valence state, lattice structure, and electrode materials on the electrical characteristics of metal-oxide-based diode. By improving pre-existing technologies, developing new technologies, optimizing material micro-structure, and choosing suitable electrodes to successfully obtain a type of metal-oxide-based diodes which can be used for integrating with bipolar RRAM. On the basis of the research results and experience, we will finish the bipolar 1D1R integration and the bipolar 1D1R cross-bar architecture. The successful implementation of this project has important innovativeness and usability, which is expected to get a lot of original research achievements with independent intellectual property rights in RRAM field. At the same time, it can provide new direction and momentum for achieving RRAM high-density storage.

基于金属氧化物的1D1R 阻变存储结构因为具有好的可缩小型、能够抑制交叉阵列中的误读现象、与CMOS工艺兼容、可实现三维高密度集成，被认为是RRAM 领域的主流技术之一。由于普通二极管的单向导通性，目前有关1D1R 的研究都集中在单极性RRAM 器件上。本项目基于阻变特性更加优越的双极性RRAM 器件，着眼于如何实现双极性RRAM 器件与氧化物二极管集成这一尚未解决的关键科学问题。理论结合实验，深入研究材料组分、成分价态、晶格结构、电极材料等对金属氧化物二极管电学特性的影响规律，通过优化材料微观结构以及选择合适的电极，制备满足与双极性RRAM集成的氧化物二极管，以此获得具有稳定双极性阻变特性的新型1D1R 存储单元及其交叉阵列。本项目的成功实施在RRAM 研究领域具有重要的源头创新意义，有望在此领域获得大量具有自主知识产权的原创性研究成果，为RRAM的高密度存储提供新的发展方向和动力。

基于金属氧化物的1D1R 阻变存储结构因为具有好的可缩小型、能够抑制交叉阵列中的误读现象、与CMOS 工艺兼容、可实现三维高密度集成，被认为是RRAM 领域的主流技术之一。由于普通二极管的单向导通性，目前有关1D1R 的研究都集中在单极性RRAM 器件上。本项目基于阻变特性更加优越的双极性RRAM 器件，针对如何实现双极性RRAM 器件与氧化物二极管集成展开研究工作。主要研究了材料组分、电极材料等对金属氧化物二极管电学特性的影响规律，阐明了影响金属氧化物二极管电学特性的主要因素，制备出了满足与双极性RRAM 集成的氧化物二极管单元。基于ZrO2和TiO2材料制备了具有Cu/ZrO2/TiO2/Ti双层结构的RRAM存储单元，该结构器件所采用的材料与CMOS工艺完全兼容，并且电阻转变特性具有很好的一致性。通过选择合适的Reset电压，该器件能够实现多值存储，并且Reset电流低于100μA。通过选择合适的限制电流，该器件具有二极管的整流特性，并且整流比能够达到106。此外，我们提出了一种由反向并联二极管作为选择器与双极性RRAM单元集成的新型结构器件，这种采用反向并联二极管作为选择器的交叉阵列的存储密度能够达到1兆。本项目的实施在阻变存储器高密度集成领域积累了大量实验数据，为阻变存储器高密度集成研究奠定了基础。