Atomic-scale quantification of interdiffusion and dopant localization in GeSbTe-based memory devices

• Published in: Applied physics letters Vol. 109; no. 11
• Main Authors: Chae, B.-G., Seol, J.-B., Song, J.-H., Jung, W.-Y, Hwang, H., Park, C.-G.
• Format: Journal Article
• Language: English
• Published: Melville American Institute of Physics 12-09-2016
• Subjects: Annealing; Applied physics; Computer memory; Diffusion layers; Dopants; Interdiffusion; Localization; Memory devices; Phase change; Phase transitions; Polycrystals; Transition layers; Transmission electron microscopy
• ISSN: 0003-6951; 1077-3118
• DOI: 10.1063/1.4962807

Fabrication of phase-change memory devices at modest or ambient temperatures leads to nanoscale compositional variations in phase-transition layers, where amorphous-polycrystalline phase change takes place via electrical switching, and can alter the device's performances. Here, by transmission electron microscopy and atom probe tomography, we address that thermal annealing at 400 °C for 20 min induces an elemental interdiffusion in the devices consisting of TiN (top electrode), carbon-doped GeSbTe (phase-transition layer), and TiSiN (bottom heater). With respect to the employed annealing process, the Ge atoms of GeSbTe layer have diffused into TiSiN layer at a given sample volume, while the Ti atoms of TiSiN layer into GeSbTe layer. Furthermore, non-random nature of dopant distribution in the GeSbTe materials leads to a Ti-localization including dopants at the GeSbTe/TiSiN interfaces. Our findings have two important implications: First, the annealing-driven interdiffusion of Ge and Ti is a predominant mechanism responsible for nanoscale compositional variations in GeSbTe layer; second, such an interdiffusion and the resultant dopant localization play a crucial role on the driving force for amorphous-polycrystalline transition of GeSbTe-based memory devices.