R&D: Phase-Change Memory, Continuous Multilevel Compact Model of Subthreshold Conduction and Threshold Switching

Japanese Journal of Applied Physics, Volume 57, Number 4S has published an article written by Corentin Pigot, STMicroelectronics, 38926 Crolles, France, CEA Leti, MINATEC Campus, F-38054 Grenoble, France, and IM2NP, Aix-Marseille Université, 13453 Marseille, France, Fabien Gilibert, STMicroelectronics, 38926 Crolles, France, Marina Reyboz, CEA Leti, MINATEC Campus, F-38054 Grenoble, France, Marc Bocquet, IM2NP, Aix-Marseille Université, 13453 Marseille, France, Paola Zuliani, STMicroelectronics, 20041 Agrate Brianza, Italy, and and Jean-Michel Portal, IM2NP, Aix-Marseille Université, 13453 Marseille, France.

Abstract :  “Phase-change memory (PCM) compact modeling of the threshold switching based on a thermal runaway in Poole–Frenkel conduction is proposed. Although this approach is often used in physical models, this is the first time it is implemented in a compact model. The model accuracy is validated by a good correlation between simulations and experimental data collected on a PCM cell embedded in a 90nm technology. A wide range of intermediate states is measured and accurately modeled with a single set of parameters, allowing multilevel programing. A good convergence is exhibited even in snapback simulation owing to this fully continuous approach. Moreover, threshold properties extraction indicates a thermally enhanced switching, which validates the basic hypothesis of the model. Finally, it is shown that this model is compliant with a new drift-resilient cell-state metric. Once enriched with a phase transition module, this compact model is ready to be implemented in circuit simulators.“