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Dresden 2011 – scientific programme

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DF: Fachverband Dielektrische Festkörper

DF 9: High-k and Low-k Dielectrics (Joint Session of DS, DF)

DF 9.3: Talk

Tuesday, March 15, 2011, 14:15–14:30, GER 38

Phase equilibria at Si-HfO2 and Pt-HfO2 interfaces from first principles thermodynamics — •Rampi Ramprasad1 and Hong Zhu21University of Connecticut, Storrs, USA; Fritz-Haber-Institut der MPG, Berlin, Germany — 2University of Connecticut, Storrs, USA

In this work, two types of interfaces found in the emerging technologically important high-k MOSFETs have been studied. The phase diagrams of Si-HfO2 and Pt-HfO2 interfaces as a function of temperature and oxygen pressure have been determined using first principles thermodynamics (FPT), i.e., by combining conventional density functional theory results with thermodynamics [1]. The vibrational and configurational entropic contributions to the free energies of the condensed phases are explicitly included in this treatment. We demonstrate that the predictions of the FPT approach are in quantitative agreement with experiments for the classes of interfaces considered here. In particular, under UHV conditions, we show that FPT methods predict the correct Si-HfO2 silica-like interface configurations. Likewise, we also show that an interfacial oxygen coverage of 0.5-1.0 monolayer is favored under UHV conditions at the Pt-HfO2 interface before rapid oxidation of Pt may be expected (for higher oxygen pressures). These results have important implications both for the applicability of FPT methods for the considered classes of interfaces as well as for high-k dielectrics-based electronic devices in which such interfaces are expected.

[1] H. Zhu, C. Tang and R. Ramprasad, Phys. Rev. B, in print (2010).

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