超低功耗氧化物阻变存储器的研制及其阻变机理的研究

To realize the high-density non-vilatile memory applications in CMOS integrated circuits,the low-power Resistive random access memory (RRAM) devices will be of great importance.Targeted on obtaining the low-power RRAM, this project aims to reduce the power consumption from three aspects: the electrode,the resistive switching layer as well as the post treatment.In this proposal,transparent and conductive ITO electrode will be employed to lower the operation voltage and further explore the new resistive switching behavior and the correlation with the ITO electrode; CMOS compatable HfO2-based materials will be introduced as the switching layer and the operation current is expected to be reduced by applying doping or novel structures to the switching layer. The dependence of switching characteristics and the power consumption on the switching layer with doping or novel sructures will be revealed. In the following, envionmental-friendly supercritical fluid technology with the property of low temperature will be adopted to improve the performance and reduce the power as well. The condition and reason of improving the performance by supercritical fluid technology will be disclosed.Based on the above researches, we can finally obtain RRAM device with an operation power lower than 10-6 W.Meanwhile,the relationship between the formation/rupture of conductive filament with the electrode,the resistive switching layer as well as the post treatment will be disclosed in oder to provide the experimental evidences for the research of RRAM mechanism. The smooth implementation of this project will not only propose an innovative idea to fabricate novel RRAM with low-power and excellent performance but be meaningful in science for making the theory of conductive filament more comprehensive.

获得超低功耗的阻变存储器（RRAM）对于实现CMOS集成电路中高密度非挥发性存储具有重要意义。本项目以获得"低功耗"RRAM器件为目标，从电极、阻变层和后处理工艺三方面展开研究。拟采用透明导电的氧化铟锡(ITO)作为活性电极来获得低操作电压，并探明RRAM新的阻变性能及其与ITO电极的关联；采用与CMOS工艺兼容的HfO2基材料为阻变层，通过掺杂和结构优化设计来降低操作电流，阐明阻变层掺杂和结构对RRAM阻变性能和功耗的影响规律；再辅以低温环保的 "超临界流体"技术来提升器件的存储性能和进一步降低功耗，探清该技术的最佳工艺条件和作用机理。由此，最终获得功耗低于1微瓦的氧化物RRAM原型器件；并揭示导电细丝形成及断裂与电极、阻变层和后处理工艺的内在联系，为阻变机理的研究提供实验依据。该项目的实施，不仅为构筑功耗低、存储性能优异的RRAM器件提供新思路，而且对完善细丝理论具有重要的科学意义。

21 世纪，计算机技术、互联网以及新型大众化电子产品的快速发展，对信息存储产品的需求呈现高速上升趋势，迫切需要在存储器材料和技术方面取得突破。当前公认可以取代闪存的存储器之一是阻变式随机存储器(RRAM)且获得超低功耗的RRAM对于实现CMOS 集成电路中高密度非挥发性存储具有重要意义。本项目以获得“低功耗”RRAM 器件为目标，从电极、阻变层和后处理工艺三方面展开研究。本项目系统开展了透明ITO电极、稀土Gd电极、阻变层为氧化铪、氧化锆、氧化锌等RRAM器件单元的研究。项目创新性地运用超临界处理技术，获得提升器件性能的工艺参数及优化机理，并成功地通过该技术在电极中掺入氮元素,从而降低器件功耗至120 nW。通过在氧化锆阻变层中掺氮、氧化铪层中掺铪有效提升器件阻变参数一致性和存储窗口。探索新颖的电极材料钆应用于器件，发现低阻态电流随着限流值的下降而呈上升趋势并揭示钆电极作用机理。采用第一性原理计算方法，研究Au掺杂前后阻变层材料氧化锆的氧空位的形成能和迁移势垒能等，从理论上解释阻变层掺杂效应,与实验结果一致。研究不同氛围退火对Ti掺HfO2超晶胞中氧空位的影响, 发现最佳的钛掺杂浓度为3.13%，通过模拟实验中的退火条件，发现氮气退火处理有效的降低了钛掺杂氧化铪超晶胞中氧空位的形成能和迁移势垒，使得由氧空位组成的导电细丝更加容易形成，断裂与连接。通过对该项目的实施，不仅为构筑功耗低、存储性能优异的RRAM 器件提供新思路，而且对完善细丝理论具有重要的科学意义。