文档介绍：华中科技大学
硕士学位论文
相变随机存储器存储机理及仿真技术研究
姓名:袁成伟
申请学位级别:硕士
专业:微电子学与固体电子学
指导教师:胡作启
20090525
华中科技大学硕士学位论文

摘要
相变随机存储器是一种新兴的、被认为最有希望成为下一代主流的非易失性固
态存储技术。
基于相变随机存储器的存储原理、有限元法和经典的成核/生长理论,建立了存
储元写信息过程的仿真物理模型。提出了一种包含大六面体网格、四面体网格和精
细六面体网格且可有效用于电-热致相变过程连续仿真的多网格技术,并推导了电、
热传导偏微分方程四面体有限元单元离散公式;针对存储介质的相转变过程仿真提
出了一种晶态-固态仿真模型。编写了完整的存储元二维、三维仿真程序,对存储元
进行了电、热性能和相转变过程仿真。
对 100nm 光刻工艺、20nm 薄膜工艺下的存储元进行了二维电、热仿真和三维电、
热、相转变过程仿真。结果表明,被仿真的三种存储元都可以用于二值信息存储,
自下而上存储元非晶态数据保存时间最长(95℃下保存十年)但操作电流不易降低;
边缘接触式存储元操作电流较低、非晶态/晶态电阻比最高(×103)但热散失较
大;工字形存储元加热效率高热散失低,非晶化电流最小()但非晶态/晶态
电阻比有待提高、数据不易保存。边缘接触、电流自限制、热阻层等结构都可以用
于减小操作电流。
此外,对不同幅值、宽度脉冲以及多脉冲条件下的边缘接触式存储元进行了仿
真,结果表明:使用单脉冲操作的方式较难达到多值存储的目的,但合适的脉冲幅
值和脉冲宽度都有利于提高存储元的存储性能;采用多脉冲的操作方式存在多值存
储的可能性,其方法是使用连续有限个数的短脉冲使存储介质达到不同的晶化程度。

关键词:相变存储;仿真模型;有限元法;多网格技术;经典成核/生长理论;晶态
-固态模型
I
华中科技大学硕士学位论文

Abstract
Phase change random access memory (PCRAM) is a kind of rising semiconductor
memory. PCRAM is regarded as one of the most promising candidates for the next
generation non-volatile semiconductor memory.
In this paper, a physical simulation model was developed based on storage principle
of PCRAM, the finite element method and classical nucleation/growth theory. For the
need of electricity-heat-induced phase transition process simulation, a multi-grid system
including big hexahedral grids, tetrahedral grids and fine hexahedral grids were proposed
and the relative application technology is presented too. The multi-grid system is of higher
efficiency in the electricity-heat-induced phase change process simulation. Finite element
discrete formules for electricity and heat conduction equation in tetrahedral were derivated.
A crystalline-solid state simulation model was established for phase change transition
process simulation of phase change material. Then, two and three-dimensional simulation
programme was wrote and memory cells were simulated using the programme.
Two dimensional electricity and