IUVSTA 15th International Vacuum Congress (IVC-15), AVS 48th International Symposium (AVS-48), 11th International Conference on Solid Surfaces (ICSS-11)
    Dielectrics Tuesday Sessions
       Session DI-TuA

Paper DI-TuA10
Spectroscopic Ellipsometry Characterization of High-k Dielectric Thin Films

Tuesday, October 30, 2001, 5:00 pm, Room 130

Session: High K Dielectrics III
Presenter: N.V. Nguyen, National Institute of Standards and Technology
Authors: N.V. Nguyen, National Institute of Standards and Technology
Y.J. Cho, National Institute of Standards and Technology
R.A. Richter, National Institute of Standards and Technology
J.R. Ehrstein, National Institute of Standards and Technology
Correspondent: Click to Email
Spectroscopic ellipsometry (SE) characterization of high-k gate dielectric thin films will be presented in this paper. The materials investigated include HfO2, ZrO2, TiO2, and Ta2O5 films on silicon substrates. These films are candidates to replace traditional SiO2 gate dielectrics. Unlike SiO2, the dielectric functions for these high-k films are not yet established and are strongly dependent on deposition process and conditions. Therefore, the objective of this study is to assess and validate optical models that can reasonably represent the dielectric functions of these materials. The films used in this study were fabricated by different techniques including chemical vapor deposition, jet vapor deposition, and sputtering, and were post-deposition annealed at various high temperatures. To model the SE experimental data, single and multiple Tauc-Lorentz (TL) dispersion function(s) were employed for the dielectric functions of the films. It is found that a simple single TL can generally reproduce the dielectric function below and near the absorption edge. Above the edge, a summation of two or more TL dispersions is needed to improve data fitting. For samples annealed at high temperatures, additional new optical features due to structural changes in the films were seen in their dielectric functions, which require even more than two TL dispersions to fit the data. In addition, the effect of a possible oxide layer at the interface between the substrate and the films was examined in the relation with their determined dielectric functions. We also describe and evaluate the use of other optical dispersions such as harmonic oscillator approximations for high-k thin films and compare the results with those of TL dispersion. A brief discussion for using extended spectral range into vacuum ultraviolet region to characterize these and other high-k dielectric thin films will be presented.