Simulation Research On Phase Change Memory Cell

Flash memory is the undisputed market leader for commercial non-volatile memoriespresently, and it has been used widely. However, the development of Flash memory is limitedby its storage mechanism, so that Flash store isn’t an ideal memory technology for moregenerations. It’s high time that we should develop new type non-volatile memories. Amongthe many new possible non-volatile memories, phase change random access memory, whichemploys chalcogenide as memory medium, seems to be one of the most promising candidatesto replace Flash memories.This thesis carries out detailed researches on the phase change memory cell, and they arebased on a memory cell simulation system, which built base on phase change memory storagemechanism. To begin with, it builds the simulation system based on the Laplace equation, theFourier heat conduction equation, the classical nucleation/growth theory, the Thermal Spikemodel. Next, it studies the impact of the geometric parameters, the physical parameters on theperformance of the memory cell, and optimizes the design of the cell on the basic of researchresults. In the third place, it studies the impact of different energy outside particle on theperformance of the memory cell. The geometric parameters researched include the size of upand down electrodes, and the size of phase change layer in the cell. The physical parametersresearched include the resistivity of electrode material, the heat conductivity of electrodematerial, the resistivity of storage medium, the heat conductivity of storage medium and thematerial of insulating medium.The simulation results demonstrate that the size of phase change layer Z direction, theresistivity of storage medium and the material of insulating medium have more impacts on thememory cell performances. To decrease the size of phase change layer Z direction can reducethe operating voltage of the cell and increase operation speed of the cell, which is as the sameas decrease resistivity of storage medium. In the simulation range the biggest change ratio ofthe total resistance of the cell is1%and the cell that struck by the outside heavy-ion can beadopted read and write operations effectively. The cell is shown to be insensitive to heavy-ionstrike and will likely remain so for a few more generations.