Investigation of hafnium-aluminate alloys in view of integration as interpoly dielectrics of future Flash memories |
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Authors: | Gabriel Molas Marc Bocquet Julien Buckley Helen Grampeix Marc Gly Jean-Philippe Colonna Christophe Licitra Nvine Rochat Thomas Veyront Xavier Garros Franois Martin Pierre Brianceau Vincent Vidal Cosimo Bongiorno Salvatore Lombardo Barbara De Salvo Simon Deleonibus |
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Institution: | aCEA-LETI Minatec, 17 rue des Martyrs, 38054 Grenoble Cedex 9, France;bCNR-IMM Catania, stradale Primosale 50, 95121 Catania, Italy |
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Abstract: | In this paper, we evaluate the potentialities of hafnium-aluminates (HfAlO) materials as possible candidates for the interpoly dielectrics of future Flash memory devices. HfAlO layers of different thicknesses and compositions are integrated in single-layers and in Oxide/HfAlO/Oxide (OHO) triple-layer stacks, and analyzed in terms of coupling and insulating capabilities. We demonstrate that increasing the Hf content allows reducing the leakage current at high voltages but it results in a stronger leakage current at low voltages. We also show that once normalized in electric fields, the leakage current characteristics are independent of the high-k thickness. The electron conduction modes in these materials, at different temperatures, are also investigated. The activation energy increases with the Hf concentration in the HfAlO alloy, resulting in a higher leakage current at elevated temperatures. Finally, it is demonstrated that the conduction in triple-layer stacks is limited by a Poole–Frenkel conduction in the high-k layers, while the trap contribution in the case of single-layers becomes dominant when the HfAlO layer is thicker than 8 nm. |
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Keywords: | Non-volatile memories High-k Interpoly dielectrics Hafnium-aluminate HfAlO Poole– Frenkel |
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