Vacuum-Insulated Self-Aligned Nanowire Phase-Change Memory Devices

Abstract

Phase-change memory (PCM) is an emerging technology for faster nonvolatile memory where a small volume of phase-change material is switched between amorphous and crystalline states to provide distinct logic levels. A major difficulty with these devices is the high-power requirement for set and reset operations. In this brief, we computationally analyze a vacuum-insulated self-aligned Ge <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> Sb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> Te <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">5</sub> nanowire (NW) PCM device and propose a way to control the placement and orientation of the NWs. The analysis is performed using 2-D rotationally symmetric finite-element simulations with temperature-dependent material parameters and accounting for thermoelectric effects. Simulation results predict a ~10× reduction in current required for reset operation and minimal thermal crosstalk when compared with a similarly sized conventional mushroom cell due to effective suppression of lateral heat loss. The operation of the vacuum-insulated NW devices is also almost independent of current polarity (unlike that of the mushroom cell), which can be advantageous for more flexible array programming schemes. These devices can be used to build densely packed PCM with lower power consumption and less thermal crosstalk.