用于高密度、快速相变存储器的纳米复合多层相变薄膜研究

Phase change random access memory (PCRAM) has been regarded as one of the most promising candidates for the next-generation nonvolatile memory. However several problems still remain to be solved. For example, the power consumption of PCRAM needs to be reduced. Common phase change material can not offer both fast phase change speed and high thermal stability. There is also high demand to improve the storage density of PCRAM. To target the above problems, this study will introduce phase transition film in 2-2-model nanocomposite configuration, which will maintain the original characteristics of the phase-change material. With two or even more than two types of phase-change materials and dielectric materials, this composite approach can overcome the deficiency of single material properties and improve the comprehensive properties of cells, and fit requirements of the application of the PCRAM. Adopting polymorphism in multilayer phase-change films enables its memory density increment, meanwhile it keeps the high speed of phase-change property. It also increases the memory speed of phase-change. Finally, the implementation of the nanocomposite multilayer phase-change films for high-speed and high density phase-change materials into PCRAM cells will be systematically evaluated. The goal is to achieve materials with good quality and devices with high performance, which have independent intellectual property rights.

相变存储器（PCRAM）以其独有的特点，被认为是下一代最有潜力的非挥发性存储器。随着研究的不断深入，相变存储技术取得了重要进展，但仍然面临着诸多需要解决的问题。例如：目前PCRAM存储单元的功耗过高；单一相变材料难以同时具有快的相变速度和良好的热稳定性；PCRAM器件的存储密度还有进一步提升空间。本研究针对目前PCRAM存在的问题，采用在纳米尺度上相变薄膜材料2-2复合的方式，在保持原有相变特性的同时，通过两种或两种以上不同电阻率和晶化温度等的相变材料之间性能上的"取长补短"，弥补单一材料性能的不足，从而提升器件的综合性能，更加适合相变存储器的应用要求。通过在多层复合薄膜中引入独特的多态方式以增加其存储密度，同时保持复合薄膜快相变速度的特点，提高其存储密度和相变速度，经过优化组合的复合多层相变薄膜材料将被应用在PCRAM器件中进行系统性性能表征和评估，并形成具有独立知识产权的材料体系。

由于PCRAM 性能主要依赖于相变存储材料性质，开发新型高性能相变薄膜显得尤为重要和迫切。 因此，本课题设计、构建了多种纳米复合相变薄膜材料体系，对薄膜的结晶行为、相变特征、相结构、微结构、化学成键、相变机制、表面性能、纳米尺寸效应、多层界面效应等展开了较为系统的研究。同时，制备基于最优组分薄膜PCRAM器件， 并对其阈值转换等电学性能进行表征和分析。取得如下主要研究结果。. 揭示了纳米复合多层相变薄膜层和层之间的耦合机理，特别是单层与多层复合之间的关联以及多层之间的耦合作用。明确了2-2型纳米复合多层相变薄膜综合性能的优化途径，在多层复合薄膜中同时实现快速和多态存储的途径，提高器件单元的存储密度、存储速度和数据保持能力。获得了两种具有高速、高密度的纳米复合多层相变薄膜，这种多层结构在相变前后具有较好的稳定性。不但具有晶化速度快，还具有相变前后体积变化小、稳定性好特点。为高速、高密度、高可靠相变存储器件提供材料基础。