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WOx resistive memory elements for scaled Flash memories

Published online by Cambridge University Press:  29 June 2011

S. Gorji Ghalamestani ,
L. Goux ,
D.E. Díaz-Droguett ,
D. Wouters  and
J. G. Lisoni
S. Gorji Ghalamestani
Affiliation:
IMEC, Leuven, Belgium
L. Goux
Affiliation:
IMEC, Leuven, Belgium
D.E. Díaz-Droguett
Affiliation:
Materials Science Labs, Faculty of Physics, Pontificia Universidad Católica de Chile, Chile
D. Wouters
Affiliation:
IMEC, Leuven, Belgium Electrical Engineering Dept. (ESAT), Katholieke Universiteit Leuven
J. G. Lisoni
Affiliation:
IMEC, Leuven, Belgium Physics Dept., FCFM, Universidad de Chile, Santiago, Chile
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Abstract

We investigated the resistive switching behavior of WOx films. WOx was obtained from the thermal oxidation of W thin layers. The parameters under investigation were the influence of the temperature (450-500 °C) and time (30-220 s) used to obtain the WOx on the resistive switching characteristics of Si\W\WOx\Metal_electrode ReRAM cells. The metal top electrodes (TE) tested were Pt, Ni, Cu and Au. The elemental composition and microstructure of the samples were characterized by means of elastic recoil detection analysis (ERD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), X-ray diffraction (XRD) and X-ray reflectivity (XRR).

Electrical measurement of the WOx-based memory elements revealed bipolar and unipolar switching and this depended upon the oxidation conditions and TE selected. Indeed, switching events were observed in WOx samples obtained either at 450 °C or 500 °C in time windows of 180-200 s and 30-60 s, respectively. Pt and Au TE promoted bipolar switching while unipolar behavior was observed with Ni TE only; no switching events were observed with Cu TE. Good switching characteristics seems not related to the overall thickness, crystallinity and composition of the oxide, but on the W6+/W5+ ratio present on the WOx surface, surface in contact with the TE material. Interestingly, W6+/W5+ ratio can be tuned through the oxidation conditions, showing a path for optimizing the properties of the WOx-based ReRAM cells.

Keywords

Woxidationmemory
Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 1337: Symposium Q – New Functional Materials and Emerging Device Architectures for Nonvolatile Memories , 2011 , mrss11-1337-q08-10
Copyright
Copyright © Materials Research Society 2011

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References

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