A novel low power phase change memory using inter-granular switching

We propose and demonstrate a new low power phase change memory using a novel 3D network of crystallites with phase change confined to only at grain intersections. Contrary to conventional phase change memories, for which an entire volume of chalcogenide glass is amorphized or crystallized for high or low resistance, we propose a multi-grained structure where we only induce phase change in the inter-grain regions. This not only drastically reduces the phase change volume but also improves the thermal efficiency of the cell. 3D simulation is used to understand the local heating effect. To create the multi-grained structure we have carefully studied the Ge/Sb/Te composition, the doping material and concentration and PVD deposition conditions. Consequently, the switching current can be reduced to 20uA. Furthermore, localizing the heating also reduces thermal disturbance to neighboring cells thus provides excellent pitch scalability.