Optical properties of Jet-Vapor-Deposited TiAlO and HfAlO Determined by Vacuum Utraviolet Spectroscopic Elliposmetry

Published: September 30, 2003


Nhan V. Nguyen, Jin-Ping Han, Yong Jai Cho, Wenjuan Zhu, Zhijiong Luo, T P. Ma


In this report, we use vacuum ultraviolet spectroscopic ellipsometry (VUV-SE) to determine the optical as well as structural properties of high-k metal oxides, in particular, of Hafnium Aluminates and Titanium Aluminates. Two sets of samples consisting of five samples of HfAlO films and 3 samples of TiAlO films were grown by Jet-Vapor-deposition (JVD) at room temperature on Si substrates. The Al atom percentages in the five HfAlO films are 0 % , 13.2 %, 45.5 % , 77.9 % and 100% concentrations. The three TiAlO2 samples have 15%, 30% and 50% of Al. VUV spectroscopic ellipsometry measurements were performed on a commercial ellipsometer with the spectral range covering from 1.0 eV (1240 nm) to 8.7 eV (143 nm). The Generalized Tauc-Lorentz (GTL) dispersion was used to determine the dielectric functions of these films. An ellipsometric model consisting of two layers of different film densities was found to be in excellent agreement with the experimental data. For the TiAlO films, only one film was needed in the model to fit the data. The experimentally determined dielectric function of HfAlO samples with less than 77.9 % clearly displays two distinct characteristics of a broader peak at ~7.0 eV and a shoulder peak at ~ 5.7 eV. The optical bandgaps determined by Tauc-plots are seen to increase, meanwhile the relative film densities decrease, with the increasing of Al in the films. In addition, the optical dielectric functions shift to the higher energy and decrease in their magnitudes as the films become more insulating. As a result, the Al appears to be mixed at the atomic level instead of forming a phase separation between HfO2 and Al2O3. For TiAlO, we observed similar results except that the fundamental optical bandgap was not strongly affected by the amount of Al incorporated in the films
Proceedings Title: Characterization and Metrology for ULSI Technology: 2003
Conference Dates: March 24-28, 2003
Conference Location: Austin, TX
Conference Title: International Conference on Characterization and Metrology for ULSI Technology
Pub Type: Conferences

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high-k dielectric, spectroscopic ellipsometry, thin films
Created September 30, 2003, Updated February 19, 2017