Aqueous chemical solution deposition of ultrathin lanthanide oxide dielectric films
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Sven Van Elshocht IMEC vzw, B-3001 Heverlee, Belgium
Jan D’Haen IMEC vzw, Division IMOMEC, B-3590 Diepenbeek, Belgium; and Hasselt University, Institute for Materials Research, B-3590 Diepenbeek, Belgium
Olivier Douhe´ret IMEC vzw, Division IMOMEC, B-3590 Diepenbeek, Belgium
Stefan De Gendt IMEC vzw, B-3001 Heverlee, Belgium; and KULeuven, Department of Chemistry, B-3001 Heverlee, Belgium
Christoph Adelmann, Matty Caymax, Thierry Conard, Thomas Witters, Hugo Bender, Olivier Richard, and Marc Heyns IMEC vzw, B-3001 Heverlee, Belgium
Marc D’Olieslaeger IMEC vzw, Division IMOMEC, B-3590 Diepenbeek, Belgium, and Hasselt University, Institute for Materials Research, B-3590 Diepenbeek, Belgium
Marlies K. Van Baela) Hasselt University, Institute for Materials Research, Laboratory of Inorganic and Physical Chemistry, B-3590 Diepenbeek, Belgium; and IMEC vzw, Division IMOMEC, B-3590 Diepenbeek, Belgium
Jules Mullensb) Hasselt University, Institute for Materials Research, Laboratory of Inorganic and Physical Chemistry, B-3590 Diepenbeek, Belgium (Received 6 June 2007; accepted 4 September 2007)
Ultrathin lanthanide (Nd, Pr, Eu, Sm) oxide films with functional dielectric properties down to 3.3 nm thickness were deposited by aqueous chemical solution deposition (CSD) onto hydrophilic SiO2/Si substrates. Precursor solutions were prepared from the oxides via an intermediate, solid Ln(III)citrate. A film heat treatment scheme was derived from thermogravimetric analysis of the precursor gels, showing complete decomposition by 600 °C. Crystalline phase formation in the films depended on the lanthanide, annealing temperature, and citric acid content in the precursor. Through variation of the precursor concentration and number of deposited layers, thickness series of uniform films were obtained down to ∼3 nm. The film uniformity was demonstrated both by atomic force microscopy and cross-section transmission electron microscopy. The lanthanide oxide films possessed good dielectric properties. It was concluded that aqueous CSD allows deposition of uniform ultrathin films and may be useful for the evaluation of new high-k candidate materials.
I. INTRODUCTION
Chemical solution deposition (CSD), first used for SiO2 and TiO2 about half a century ago, has been reAddress all correspondence to these authors. a) e-mail: [email protected] b) e-mail: [email protected] DOI: 10.1557/JMR.2007.0433 3484
http://journals.cambridge.org
J. Mater. Res., Vol. 22, No. 12, Dec 2007 Downloaded: 13 Mar 2015
searched and developed for the deposition of electronic oxide films since the 1980s. Films of materials such as ferroelectrics, dielectrics, conducting oxides, superconductors, etc. have been fabricated successfully using this technique.1 Typically, CSD consists of precursor sol(ution) preparation, deposition by spin, dip, or spray coating onto an appropriate substrate, and heat treatment to transform the wet film to a gel, remove organics, and © 2007 Materials Research Society IP address: 139.80.123.42
A. Hardy et al.: Aqu
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