Electrothermal modeling of projected mushroom-type phase-change memory cells

Abstract

The introduction of a projection segment or liner has emerged as a solution to the issue of resistance drift in phase change memory (PCM) devices by introducing a low-drift shunt path that bypasses read current around the drifting amorphous material. Recent work has explored experimental performance and theoretical design of the mushroom-type version of these devices, but gaps still exist in our understanding, including why RESET current appears unaffected by the presence of the liner and how large resistance switching ratio is achieved experimentally. We leverage electrothermal finite element modeling to better understand the physics of these devices. Simulations reveal that the addition of the projection liner can indeed alter the RESET current, but in the regime where low drift is achieved with a large switching window, the RESET current is comparable to that of unprojected devices. In addition, we show that anisotropy in the liner conductivity allows for the larger switching ratio that is observed experimentally. These results help shed light on the operation of projected PCM devices and offer insight to better engineer performance.