STT-MRAM信息存储机理仿真研究

发布时间：2018-03-20 04:16

本文选题：自旋传输矩磁随机存储器　切入点：存储机理　出处：《华中科技大学》2013年硕士论文　论文类型：学位论文

【摘要】：自旋传输矩磁随机存储器是一种直接利用自旋极化电流驱动纳米磁体磁矩反转、完成信息写入的新型存储器。这种存储器是一种潜在的、革命性的通用存储技术，它集成了DRAM的高存储密度、SRAM的快速读写能力、Flash的非易失性和低功耗以及高稳定性等优越性能，此外，它具有无限次使用的优势；与传统MRAM相比，有着更好的扩展性、更低的写信息电流，特别是，它与更先进的半导体工艺兼容。本文在介绍了STT-MRAM内涵的基础上，对存储单元磁隧道结MTJ自由层相关材料和结构以及自旋电子学相关理论进行了研究，分析了自由层有效场的组成、自旋输送、极化电流对自由层磁矩自旋矩作用的产生等问题，基于宏自旋模型，建立了LLGS方程；用牛顿迭代法，对模型进行了数值求解，并开发了STT-MRAM信息存储机理仿真系统；研究了自由层磁矩进动反转过程，，论证了信息“0”或“1”的写入可能性，并详细地分析了自由层厚度、饱和磁化强度、磁晶各向异性常数、阻尼系数、退磁因子等材料或结构参数对信息写入所需电流密度及时间、自由层磁矩的进动反转轨迹的影响，深入研究了STT-MRAM的信息存储机理。在参数合理取值的条件下，达到了自由层磁矩反转所需要电流密度可控制在106A/cm2数量级，所需时间在5ns内的写信息特性标准。最后根据仿真结果，本文从优化自由层材料和改进MTJ及自由层结构等方面论述了可减小自由层磁矩反转所需电流密度的一些具体措施，研究了提高STT-MRAM工作可靠性及稳定性的方法。
[Abstract]:Spin transfer moment magnetic random access memory is a new type of memory which directly uses spin polarization current to drive magnetic moment inversion of nanomagnets to complete information writing. This kind of memory is a potential and revolutionary universal storage technology. It integrates the fast reading and writing capability of DRAM with high storage density and the advantages of non-volatile, low power consumption and high stability. In addition, it has the advantage of unlimited use, and has better expansibility than traditional MRAM. Lower write message current, in particular, compatible with more advanced semiconductor processes. On the basis of introducing the connotation of STT-MRAM, the material and structure of MTJ free layer in memory cell magnetic tunnel junction and the theory of spin electronics are studied in this paper. The composition of free layer effective field and spin transport are analyzed. Based on the macro spin model, the LLGS equation is established, the model is solved numerically by Newton iteration method, and the simulation system of STT-MRAM information storage mechanism is developed. The precession process of free layer magnetic moment is studied, the possibility of writing information "0" or "1" is demonstrated, and the free layer thickness, saturation magnetization, magnetocrystalline anisotropy constant and damping coefficient are analyzed in detail. The influence of demagnetization factor and other material or structure parameters on the current density and time required for information writing and the precession inversion trajectory of free layer magnetic moment are studied. The information storage mechanism of STT-MRAM is deeply studied. The current density required for the free layer magnetic moment reversal can be controlled in the order of 106 A / cm ~ 2 and the time required is within 5 ns. Finally, based on the simulation results, some specific measures to reduce the current density required for the free layer magnetic moment reversal are discussed from the aspects of optimizing the free layer material and improving the MTJ and free layer structure. The methods to improve the reliability and stability of STT-MRAM are studied.
【学位授予单位】：华中科技大学
【学位级别】：硕士
【学位授予年份】：2013
【分类号】：TP333

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