Operation fundamentals in 12Mb Phase Change Memory based on innovative Ge-rich GST materials featuring high reliability performance

For the first time, we present a Phase Change Memory (PCM) device with an optimized Ge-rich GeSbTe (GST) alloy integrated on a 12Mb test vehicle. We confirm that PCM can guarantee high data retention in extended temperature range and we provide the understanding of the high thermal stability of the two programmed states. We show how the elemental distribution reaches an equilibrium at the core of the storage element after the electrical activation of the cell, which relates to the strong opposition against crystallization of the RESET state. We also highlight the low number of grain boundaries along the conductive path of the optimized SET state, thus explaining the low drift of the resistance. Simulation results account for the experimental observations, showing how the segregation phenomena and the localization of the electronic switching impact the elemental distribution and the formation of the crystalline structure during programming.