基于三维限制生长C-SbTe纳米晶的薄膜与器件及其快速阈值转变与高可靠机理

Three-dimensional and highly reliable phase-change memory is one of the research hotspots in the new storage field at present. The traditional Ge2Sb2Te5 has the problems of slow speed, poor thermal stability and data retention, large changes in density before and after the phase change process, which seriously affect the speed and reliability of the device. This project proposed a three-dimensional constrained crystallization of C-SbTe (CST) discrete nanocrystalline thin film that is compatible with the process, with the advantages of high speed, high thermal stability, small changes in density and excellent radiation resistance. And it is suitable for three-dimensional high reliability memory applications. This project systematically studied the crystallization and electrical properties of CST, microstructure, carrier transport properties, developed a prototype device based on radiation resistance SOI substrate and CST to obtain the properties of phase change, storage, radiation resistance and data retention of the devices. Data retention: 10 years @ 125 oC, speed: 5 ns, storage window: 100 times, density change rate: 3%, radiation resistant: 5Mrad (Si). We use First-Principles Theory and Molecular Dynamics Simulation, combined with the high-resolution analysis of the formation and distribution of the bonds of CST, to clarify the effect of C doping on crystallization, transport properties and device performance and to reveal the mechanism of rapid phase change, threshold transition and high thermal stability.

三维高可靠相变存储是当前新型存储领域的研究热点之一，然而传统的Ge2Sb2Te5晶化速度慢、热稳定性和数据保持力差、相变前后密度变化大，严重影响器件速度与可靠性。本项目提出一种工艺兼容的基于三维限制生长的C-SbTe（CST）纳米晶的薄膜与器件，具有高速、高热稳定、低密度变化与抗辐射的优异性能，适于三维高可靠存储器应用。本项目系统研究CST的结晶与电学特性、微结构、载流子输运特性等，研制出基于抗辐射SOI衬底和CST的原型器件，获得器件的可逆相变、存储特性与抗辐射性能；数据保持力：10 years@125 oC，速度：5 ns，存储窗口：100倍，密度变化率：2%，抗辐射：5 Mrad (Si)；利用第一性原理计算和分子动力学模拟，结合高分辨分析手段研究CST的成键特性与C的分布特征，阐明C对CST的结晶、输运特性和器件性能的影响规律；揭示CST的快速阈值转变、低密度变化与高热稳定机理。

三维相变存储器（3D PCM）是新型存储器的重要研究方向之一，然而传统的Ge2Sb2Te5材料相变速度慢、数据保持力差、体积变化和阻值漂移大。本项目系统研究了C元素掺杂Sb-Te相变材料以及C掺杂富Sb-GeSbTe相变材料，利用半导体工艺在Si和SOI衬底上成功研制出基于C掺杂相变薄膜的原型器件。作为对比，还研究了超硬Re元素、AlSc等过渡金属掺杂对Sb-Te基相变材料性能的影响；此外，针对高密度三维相变存储器，提出一种基于Ge-Te的具有大开启电流特性的新型选通器件。基于原位加热高分辨透射电镜、三维原子探针、XPS、XRD和XRR等研究了C掺杂相变薄膜的结晶特性、微结构、体积变化、成键特性与元素分布情况，分析了C掺杂对相变薄膜的结晶、输运特性和器件性能的影响，结合第一性原理计算与微结构测试，研究了C掺杂相变材料的快速相变、低密度变化与高热稳定机理。C元素掺杂Sb-Te（CST）相变材料的数据保持力高达10 years@153 oC，CST相变材料的厚度变化率仅为0.89%；基于CST相变材料器件的存储窗口最高达1000倍；阻值漂移系数约0.015, 远低于通常的GST(0.1010)和SbTe(0.055) 相变材料；CST器件擦写速度达5ns，在5ns时存储窗口仍达100倍，且器件具有超低功耗（0.57 pJ）。CST相变材料的优异特性使得其在高速、高温、低功耗与高可靠相变存储器领域具有很好的应用潜力。