R&D: Phase-Field Modeling of Non-Congruent Crystallization of Ternary Ge–Sb–Te Alloy for Phase-Change Memory Applications

Journal of Applied Physics has published an article written by R. Bayle, CEA-LETI Université Grenoble Alpes, 38000 Grenoble, France, STMicroelectronics, 850 rue Jean Monnet, 38926 Crolles, France, and Laboratoire de Physique de la matière condensée, Ecole Polytechnique, CNRS, IP Paris, 91128 Palaiseau, France, O. Cueto, CEA-LETI Université Grenoble Alpes, 38000 Grenoble, France, S. Blonkowski, CEA-LETI Université Grenoble Alpes, 38000 Grenoble, France, and STMicroelectronics, 850 rue Jean Monnet, 38926 Crolles, France, T. Philippe, H. Henry, and M. Plapp, Laboratoire de Physique de la matière condensée, Ecole Polytechnique, CNRS, IP Paris, 91128 Palaiseau, France.

Abstract: “The ternary alloy of germanium, antimony, and tellurium (GST) is widely used as a material for phase-change memories. In particular, the stoichiometric compound Ge2Sb2Te5 exhibits a rapid congruent crystallization. To increase the temperature at which spontaneous crystallization erases the stored information, alloys that are enriched in germanium have been investigated. Their crystallization is accompanied by segregation and eventually the nucleation of a new, germanium-rich phase. In order to model the redistribution of alloy components and the time evolution of the microstructure during device operations, we develop a multi-phase-field model for the crystallization of GST that includes segregation and couple it with orientation fields that describe the grain structure. We demonstrate that this model is capable to capture both the emergence of a two-phase polycrystalline structure starting from an initially amorphous material, and the melting and recrystallization during the SET and RESET operations in a memory cell of the ‘wall’ type.“