相变存储单元RESET多值存储过程的数值仿真研究

Numerical simulation of RESET operation for multilevel storage in phase change memory cell

使用数值仿真方法对相变随机存储器存储单元的RESET操作的多值存储过程进行了研究,建立了三维存储单元模型,用有限元法解Laplace方程及热传导方程以模拟电脉冲作用下的存储单元物性变化过程.计算出单元内相变层的相态分布及单元整体电阻,分析了单元内部尺寸变化对多值存储过程及状态的影响.结果表明,通过精确控制输入电脉冲,相变存储单元能够实现4值存储;多值存储状态受单元内相变层厚度及下电极接触尺寸变化的影响较大;存储状态在80℃的环境温度下均可保持10年以上不失效.

The REST operation for multilevel storage in phase change random access memory cell is investigated via numerical simulation. A three-dimensional memory cell model is built, and the physical property variation is calculated by solving the Laplace equation and the heat conduction equation with finite element method. The phase distribution in phase change layer and the total resistance of the cell are examined. The influences of cell structure size variation on multilevel storage process and states are analyzed. The simulation results demonstrate that multilevel storage can be achieved through accurate electrical pulse control while the variations of phase change layer thickness and bottom electrode contact size have relatively large effect on the storage state. The storage states can all keep stable for more than 10 years at 80 ℃.