Intrinsic data retention in nanoscaled phase-change memories - Part I: Monte Carlo model for crystallization and percolation

The amorphous phase of chalcogenide material in phase-change memories (PCMs) is subjected to spontaneous and thermal-activated crystallization. This represents a critical reliability issue and has to be carefully investigated and modeled for physically based projection of retention failure up to ten years. A new three-dimensional percolation model describing the statistical crystallization behavior in an intrinsic PCM cell for the amorphous state is developed. With this physical model, the authors were able to calculate the resistance evolution with time in the cell and the statistical distribution of retention failure times in a cell array. From the impact of geometrical parameters on the cell retention performance, PCM design guidelines to minimize data-loss effects can be obtained. The model allows the evaluation of nucleation and growth parameters and statistical extrapolations of intrinsic retention failure, which will be shown in Part 2.