| AVS 57th International Symposium & Exhibition | |
| Thin Film | Tuesday Sessions |
| Session TF2-TuM |
| Session: | Nonvolatile Memory |
| Presenter: | C. Vallée, Ujf - Ltm, France |
| Authors: | C. Vallée, Ujf - Ltm, France P. Gonon, Ujf - Ltm, France C. Mannequin, Ltm - Umr 5129 Cnrs, France T. Chevolleau, Ltm - Umr 5129 Cnrs, France H. Grampeix, CEA-LETI-MINATEC, France N. Rochat, CEA-LETI-MINATEC, France C. Licitra, CEA-LETI-MINATEC, France V. Jousseaume, CEA-LETI-MINATEC, France |
| Correspondent: | Click to Email |
Resistive-switching Random Access Memories (RRAM) have attracted considerable attention in recent years for future non-volatile memory applications. This resistance switching can be based on a modification of the crystalline structure of a material (PCRAM, Phase Changed RAM). One can also exploits the resistive switching properties of some oxides (OxRRAM, Oxide Resistive RAM) which display a change in resistance upon application of a bias voltage. In this case, oxides materials are deposited in a metal-insulator-metal (MIM) structure. In the last years several different oxides have been studied such as metal oxides (NiO, TiO2, ZrO2, CuxO…) and perovskites (BaTiO3, SrTiO3…) [1]. Hafnium oxide (HfO2) is among the oxides particularly desirable as far as integration and process compatibility are concerned since it has the advantage of being more mature from a technological point of view.
In this work, HfO2 RRAM with different thicknesses of HfO2 films (10 and 20 nm typically) are tested with and without plasma treatment. HfO2 films are grown at 350°C by atomic layer deposition (ALD) using alternate cycles of H2O and HfCl4 precursors (1 Torr) on Pt and TiN electrode materials. It is known that oxygen vacancies are playing a critical role for resistive switching. Different solutions have been proposed to modify the oxygen vacancies concentration in the device: integration of a TiOX/TiO2 bilayer films [2], doping a ZrO2 RRAM by metallic ions [3]. Here hydrogen-based plasma treatments are studied. Hence, several different hydrogen-based (NH3) plasma annealing treatments of the HfO2 dielectric are carried out in order to study the influence of the oxygen vacancies or defects on the subsequent switching behaviour before the deposition of the top electrode. The MIM structures are then electrically and physically characterized. I(V) curves are then recorded and switching parameters such the SET voltage are compared for MIM devices with and without plasma treatment. It is for example observed that a 1 min NH3 plasma treatment of HfO2 deposited on TiN improved the overall switching properties of the RRAM. The modifications of switching properties are correlated to chemical analysis results, mainly Angle-resolved X-ray Photoelectron Spectroscopy, Attenuated Total Reflexion (ATR) and Spectroscopic Ellipsometry (SE) up to 8 eV, with special attention devoted to metal/oxide interface investigations.
[1] A. Sawa, Materials Today 11 (6) (2008) 28
[2] J.J. Yang, et al, Nature Nanotech. 3 (2008) 429
[3] H. Zhang et al, Appl. Phys. Lett. 96 (2010) 123502