Atomic migration in phase change materials

During normal operation of Phase Change Memory (PCM) cells active materials undergo very high electrical and thermal stresses that cause a motion of the different atoms leading to composition variation which has a fundamental impact on performance and reliability. In order to address this issue we introduce here a comprehensive 3D physical model for mass transport in chalcogenide materials. In addition to the driving force for atom diffusion coming from concentration gradient and electric field, the model also accounts for the effect of temperature gradient and phase segregation. This new diffusion model is coupled with a calibrated electro-thermal-phase change model, thus providing a unified framework for the self-consistent simulation of both the electro-thermal and the phase/material change problems. The model is applied to the study of different types of PCM cells showing good agreement with experiments and demonstrating in particular the fundamental role played by the temperature profile.