New insights on the metastable cubic GexSbyTez phase

Materialia, vol. 48, pp. 102836

Abstract

Ge-rich Ge-Sb-Te (GGST) alloys are of high interest for industrial production of complementary metal-oxide-semiconductor integrated phase change random access memories (PCRAM) of high performance. BEOL-integrated GGST-based PCRAM constitute a relevant solution for low-power on-chip non-volatile memory production and in-memory computing, addressing new challenges of automotive and artificial intelligence applications for example. During cycling, in the low-resistive SET state, the crystallized GGST alloy is mainly made of nano-grains of two phases: diamond Ge and a ternary rock-salt (RS) Ge-Sb-Te (GST) phase. The RS-GST phase is metastable and generally assumed to exhibit the stoichiometry Ge 2 Sb 2 Te 5 corresponding to the stable hexagonal Ge 2 Sb 2 Te 5 compound. However, recent works suggest that this metastable RS-GST phase is not stoichiometric and can accept higher Ge contents, meaning that the Ge content of RS-GST could vary depending on the Ge excess level in the GGST alloy compared to the Ge 2 Sb 2 Te 5 reference stoichiometry. Consequently, the performance of GGST-based PCRAMs could vary with Ge composition of GGST alloy, suggesting the existence of an ideal GGST alloy composition showing a good compromise between crystallization temperature, programming current density, resistance, threshold voltage drift… In the present work, the structure and composition of crystallized GGST films elaborated through Ge, Sb, and Te co-sputtering were studied by X-ray diffraction, high resolution transmission electron microscopy, and atom probe tomography. The metastable RS-GST phase crystallized in GGST films exhibiting a Ge excess between 23% and 42% is found to be able to incorporate a large amount of Ge, of about 50 at% and sometimes beyond.

Authors 13

1. Jacques Perrin Toinin

   Centre National de la Recherche Scientifique · Aix-Marseille Université · Institut des Matériaux, de Microélectronique et des Nanosciences de Provence

   Affiliation as printed

   Aix-Marseille Univ., CNRS, IM2NP UMR7334, Campus Scientifique de St Jérôme, 13397 Marseille cedex 20, France

2. A. Portavoce corresponding

   Centre National de la Recherche Scientifique · Aix-Marseille Université · Institut des Matériaux, de Microélectronique et des Nanosciences de Provence

   Affiliation as printed

   Aix-Marseille Univ., CNRS, IM2NP UMR7334, Campus Scientifique de St Jérôme, 13397 Marseille cedex 20, France

3. Jacopo Remondina

   Centre National de la Recherche Scientifique · Aix-Marseille Université · Institut des Matériaux, de Microélectronique et des Nanosciences de Provence

   Affiliation as printed

   Aix-Marseille Univ., CNRS, IM2NP UMR7334, Campus Scientifique de St Jérôme, 13397 Marseille cedex 20, France

4. Hamza Khelidj

   Centre National de la Recherche Scientifique · Aix-Marseille Université · Institut des Matériaux, de Microélectronique et des Nanosciences de Provence

   Affiliation as printed

   Aix-Marseille Univ., CNRS, IM2NP UMR7334, Campus Scientifique de St Jérôme, 13397 Marseille cedex 20, France

5. Martiane Cabié

   Centre National de la Recherche Scientifique · Aix-Marseille Université · Centrale Méditerranée

   Affiliation as printed

   Aix Marseille Univ, CNRS, Centrale Med, FSCM, CP2M, Marseille, France

6. Thomas Neisius

   Centre National de la Recherche Scientifique · Aix-Marseille Université · Centrale Méditerranée

   Affiliation as printed

   Aix Marseille Univ, CNRS, Centrale Med, FSCM, CP2M, Marseille, France

7. Guillaume Roland

   Centre National de la Recherche Scientifique · Aix-Marseille Université · STMicroelectronics (France) · Institut des Matériaux, de Microélectronique et des Nanosciences de Provence

   Affiliation as printed

   Aix-Marseille Univ., CNRS, IM2NP UMR7334, Campus Scientifique de St Jérôme, 13397 Marseille cedex 20, France

   STMicroelectronics, 850 rue Jean Monnet, 38920 Crolles, France

8. Yuan Yu Aachen Physikalisches Institut

   RWTH Aachen University

   Affiliation as printed

   Physikalisches Institut, RWTH Aachen University, 52056, Aachen, Germany

9. M. Bertoglio

   Centre National de la Recherche Scientifique · Aix-Marseille Université · Institut des Matériaux, de Microélectronique et des Nanosciences de Provence

   Affiliation as printed

   Aix-Marseille Univ., CNRS, IM2NP UMR7334, Campus Scientifique de St Jérôme, 13397 Marseille cedex 20, France

10. Marion Descoins

    Centre National de la Recherche Scientifique · Aix-Marseille Université · Institut des Matériaux, de Microélectronique et des Nanosciences de Provence

    Affiliation as printed

    Aix-Marseille Univ., CNRS, IM2NP UMR7334, Campus Scientifique de St Jérôme, 13397 Marseille cedex 20, France

11. Matthias Wuttig Aachen Physikalisches Institut

    RWTH Aachen University

    Affiliation as printed

    Physikalisches Institut, RWTH Aachen University, 52056, Aachen, Germany

12. F. Lorut

    STMicroelectronics (France)

    Affiliation as printed

    STMicroelectronics, 850 rue Jean Monnet, 38920 Crolles, France

13. Elisa Petroni

    STMicroelectronics (Italy)

    Affiliation as printed

    Smart Power Technology R&D, STMicroelectronics, Agrate Brianza, Italy