Electrical properties of ultrathin Al 2 O 3 films grown by metalorganic chemical vapor deposition for advanced complemen
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Evgeni P. Gusev IBM T.J. Watson Research Center, Yorktown Heights, New York 10598 (Received 7 November 2004; accepted 18 March 2005)
The electrical properties of ultrathin amorphous Al2O3 films, grown by low temperature metal-organic chemical vapor deposition from aluminum(III) 2,4-pentanedionate and water as co-reactants, were examined for potential applications as gate dielectrics in emerging complementary metal-oxide semiconductor technologies. High-frequency capacitance–voltage and current–voltage techniques were used to evaluate Al2O3 films deposited on silicon oxynitride on n-type silicon (100) substrates, with thickness ranging from 2.5 to 6.5 nm, as a function of postdeposition annealing regimes. Dielectric constant values ranging from 11.0 to 11.5 were obtained, depending on the annealing method used. Metal-insulatorsemiconductor devices were demonstrated with net equivalent oxide thickness values of 1.3 nm. Significant charge traps were detected in the as-deposited films and were mostly passivated by the subsequent annealing treatment. The main charge injection mechanism in the dielectric layer was found to follow a Poole–Frenkel behavior, with post-annealed films exhibiting leakage current an order of magnitude lower than that of equivalent silicon oxide films.
I. INTRODUCTION
The downscaling of silicon-based complementary metal-oxide semiconductor (CMOS) devices below 100 nm requires the use of silicon dioxide (SiO2) gate oxide layers with a thickness at or below 1 nm for highperformance logic devices.1 At these thickness values, direct quantum mechanical electron tunneling results in intolerably high leakage current density, which causes device instability and ultimately failure, creates thermal dissipation issues, and prohibits efficient battery usage in portable electronics systems.1,2 For these reasons, high-dielectric constant (high-k) materials are currently being evaluated as potential candidates to replace SiO2 in emerging nanoscale device generations. These materials have the potential to achieve the same capacitance values with a larger physical thickness than their equivalent SiO2 layers, thus a)
Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/JMR.2005.0196 1536
http://journals.cambridge.org
J. Mater. Res., Vol. 20, No. 6, Jun 2005 Downloaded: 16 Mar 2015
minimizing leakage currents.3,4 Currently, high-k materials under investigation for this application include metal oxides such as aluminum, hafnium, zirconium. and yttrium oxides (Al2O3, HfO2, ZrO2, Y2O3); metal silicates such as Zr, Hf, Y, and lanthanum (La) silicates and aluminates; and binary metal oxides such as LaAl3O4 and BaZrO3.1,3,5,6 Acceptable high-k amorphous materials must possess several essential characteristics, including a thermally stable amorphous phase, chemical inertness, good adhesion to common semiconductor surfaces, large energy band gap, very low permeability to alkali ions and other impurities, and high breakdown voltage and must be compatible with prevailing integrat
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