| AVS 58th Annual International Symposium and Exhibition | |
| Electronic Materials and Processing Division | Monday Sessions |
| Session EM2-MoA |
| Session: | Dielectrics for Ultra Dense Memory Devices |
| Presenter: | Marceline Bonvalot, Laboratoire des Technologies de la Microélectronique (LTM), France |
| Authors: | M. Bonvalot, Laboratoire des Technologies de la Microélectronique (LTM), France C. Mannequin, LTM-CNRS, France P. Gonon, LTM-CNRS, France C. Vallee, LTM-CNRS, France V. Jousseaume, Minatec, France H. Grampeix, Minatec, France |
| Correspondent: | Click to Email |
HfO2 is attracting interest as a high-k dielectric for several applications in microelectronics, including transistor and Flash memory gate stacks, as well as Metal-Insulator-Metal (MIM) capacitors for DRAMs and rf circuits. As such, the assessment of HfO2 reliability is of special importance.
In this work we investigate resistive switching of HfO2-based devices. The HfO2 thin films (10 and 20 nm thick) are deposited by the Atomic Layer Deposition (ALD) technique on TiN/Si or Pt/Si wafers (bottom electrode) and top Au electrodes. The MIM devices are subjected to a constant dc voltage stress (CVS) and the current is monitored as a function of time. During these experiments we observe transient leakage currents, followed by a progressive increase of conductivity. Phenomena are related to oxygen vacancy defects. Upon bias application oxygen vacancies drift (space charge limited transient currents) to form conducting filaments (leakage increase) through the HfO2 thickness. Influence of the electrode is discussed since we found oxygen vacancies in MIM devices to be strongly correlated to the metal oxygen affinity [1]. Identical results have been recently found for TiO2 RRAM devices [2].
We also proposed to modify the oxygen vacancies and study their effects on the RRAM electrical properties by applying post deposition plasma treatment. Different hydrogen-based (NH3 and H2) 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 RRAM devices are then electrically and physically characterized. I(V) curves are then recorded and switching parameters such the SET voltage are compared for devices with and without plasma treatment. 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] C. Vallée et al, Appl. Phys. Lett. 96 (2010) 233504
[2] J.J. Yang, et al, Appl. Phys. A 102 (2011) 785