Stabilizing the ferroelectric phase in doped hafnium oxide

Journal Article · Fri Aug 21 00:00:00 EDT 2015 · Journal of Applied Physics

DOI:https://doi.org/10.1063/1.4927805· OSTI ID:22494746

Hoffmann, M.; Schroeder, U.; Schenk, T. ^[1]; Shimizu, T. ^[2]; Funakubo, H. ^[2]; Sakata, O. ^[2]; Pohl, D. ^[3]; Drescher, M. ^[4]; Adelmann, C. ^[5]; Materlik, R.; Kersch, A. ^[6]; Mikolajick, T. ^[1]

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1. NaMLab gGmbH, Noethnitzer Str. 64, D-01187 Dresden (Germany)
2. Materials Research Center for Element Strategy, Tokyo Institute of Technology, Yokohama 226-8503 (Japan)
3. Leibniz IFW Dresden, Helmholtzstr.20, D-01171 Dresden (Germany)
4. Fraunhofer IPMS-CNT, Koenigsbruecker Str. 180, D-01099 Dresden (Germany)
5. Imec, Kapeldreef 75, B-3001 Leuven (Belgium)
6. Munich University of Applied Sciences, Loth Str. 34, D-80335 Munich (Germany)

The ferroelectric properties and crystal structure of doped HfO{sub 2} thin films were investigated for different thicknesses, electrode materials, and annealing conditions. Metal-ferroelectric-metal capacitors containing Gd:HfO{sub 2} showed no reduction of the polarization within the studied thickness range, in contrast to hafnia films with other dopants. A qualitative model describing the influence of basic process parameters on the crystal structure of HfO{sub 2} was proposed. The influence of different structural parameters on the field cycling behavior was examined. This revealed the wake-up effect in doped HfO{sub 2} to be dominated by interface induced effects, rather than a field induced phase transition. TaN electrodes were shown to considerably enhance the stabilization of the ferroelectric phase in HfO{sub 2} compared to TiN electrodes, yielding a P{sub r} of up to 35 μC/cm{sup 2}. This effect was attributed to the interface oxidation of the electrodes during annealing, resulting in a different density of oxygen vacancies in the Gd:HfO{sub 2} films. Ab initio simulations confirmed the influence of oxygen vacancies on the phase stability of ferroelectric HfO{sub 2}.

• OSTI ID: 22494746
• Journal Information: Journal of Applied Physics, Vol. 118, Issue 7; Other Information: (c) 2015 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA); ISSN 0021-8979
• Country of Publication: United States
• Language: English

Related Subjects

71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
ANNEALING
CAPACITORS
DOPED MATERIALS
ELECTRODES
FERROELECTRIC MATERIALS
HAFNIUM OXIDES
OXIDATION
OXYGEN
PHASE STABILITY
PHASE TRANSFORMATIONS
POLARIZATION
SIMULATION
STABILIZATION
TANTALUM NITRIDES
THIN FILMS
TITANIUM NITRIDES
VACANCIES