Homogeneous phase W–Ge–Te material with improved overall phase-change properties for future nonvolatile memory

Abstract

Homogeneous phase W–Ge–Te material has been proposed and investigated for phase-change memory (PCM) applications. The crystallization temperature of GeTe is markedly improved by introducing W atoms. In the W–Ge–Te material, W atoms bonding to Ge and Te atoms serve as substitutional impurities. During the crystallization process, the diffusion of Ge and Te atoms is restricted by W atoms that have larger atomic mass, which further leads to more uniform crystallization of the material. W atoms serve as nucleation centers and attract the surrounding Ge and Te atoms, quickly building crystal grains. W0.1(GeTe)0.9 film has a 10-year data retention temperature of 225°C and an ultrafast crystallization time of 3ns. Specifically, W0.1(GeTe)0.9 film can withstand the Pb-free solder reflow temperature (260°C) for 4.6×104s. A voltage pulse of as little of 10ns long can realize reversible operations for W0.1(GeTe)0.9-based PCM devices. In addition, good endurance (5×105 cycles) has also been obtained for the cell.