Structural and Electrical Properties of ALD Deposited Er-HfO2 for Gate Dielectric (Contributo in atti di convegno)

Type
Label
  • Structural and Electrical Properties of ALD Deposited Er-HfO2 for Gate Dielectric (Contributo in atti di convegno) (literal)
Anno
  • 2010-01-01T00:00:00+01:00 (literal)
Alternative label
  • Wiemer C, Lamagna L, Baldovino S, Perego M, Salicio O, Schamm-Chardon S, Coulon PE, Fanciulli M (2010)
    Structural and Electrical Properties of ALD Deposited Er-HfO2 for Gate Dielectric
    in MRS Spring Meeting: Symposium I: Materials for End-of-Roadmap Scaling of CMOS Devices, San Francisco, California, USA
    (literal)
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  • Wiemer C, Lamagna L, Baldovino S, Perego M, Salicio O, Schamm-Chardon S, Coulon PE, Fanciulli M (literal)
Http://www.cnr.it/ontology/cnr/pubblicazioni.owl#descrizioneSinteticaDelProdotto
  • Doped high dielectric constant (high-k) oxides open new scaling perspectives for logic and memory devices. Actually, the insertion of a dopant element within the metallic sub-lattice of HfO2 has been demonstrated to stabilize metastable crystallographic structures [1]. Crystallization of HfO2 in polymorphs different than the monoclinic enhances the oxide dielectric constant. In particular, doping HfO2 with a rare earth element has been calculated to stabilize the cubic phase for dopant percentages above 9.9% [1]. The case of Er-doped HfO2 is of particular interest, since Er has one of the highest electronegativities and of the lowest ionic radii of the lanthanide series, therefore presenting a reduced tendency for hydroxide formation. Er-doped HfO2 films have been deposited on Si(100) by atomic layer deposition (ALD) using (iPrCp)3Er and (MeCp)2HfMe(OMe), respectively as Er and Hf source, and O3 as oxygen source. Different chemical compositions were explored by tuning the ALD pulses ratio. The Er/Hf chemical content was measured by total reflection X-ray fluorescence, and its uniformity within the layer thickness was checked by time of flight secondary ion mass spectroscopy. The film thickness was measured by spectroscopic ellipsometry, X-ray reflectivity and transmission electron microscopy. Different crystallographic structures were obtained by varying the Er content. Selected area electron diffraction patterns and X-ray diffraction analysis revealed that, within the fluorite structure, phase stability upon annealing up to 900°C in N2 is verified on Si for Er content as low as 8%. C-V characteristics are measured on MOS structures including Er-HfO2. As a general trend, for Er percentages below 8% the k value or Er-HfO2 decreases due to the increase of the monoclinic phase content, differently, the interface state defects decreases with decreasing Er content. Dielectric constant values even higher than the one calculated for the fluorite polymorph of HfO2 [2] have been extracted, therefore confirming both the stabilization of the cubic phase and the beneficial role on the dielectric response of the Er3+ ions inserted within the metallic sub-lattice. As compared with pure HfO2 crystallized in the monoclinic phase, lower leakage currents for comparable equivalent oxide thickness (EOT) are measured for films with 15% Er content, due to the increased physical thickness of the high-k layer. On the other hand, the introduction of Er3+ results in the creation of oxygen vacancies that partially compensate the negative fixed charges present in the oxide, as deduced from the plot of the flat band voltage shifts towards EOTs. (literal)
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  • 1. MDM, CNR-IMM, Agrate Brianza, Mi, Italy; 2. Dipartimento di Scienza dei Materiali, Università degli Studi di Milano-Bicocca, Milano, Italy; 3. CEMES CNRS and Université de Toulouse, nanoMat group, Toulouse, France. (literal)
Titolo
  • Structural and Electrical Properties of ALD Deposited Er-HfO2 for Gate Dielectric (literal)
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