AVS 50th International Symposium
    High-k Gate Dielectrics and Devices Topical Conference Monday Sessions
       Session DI-MoM

Paper DI-MoM6
X-ray Photoelectron Spectroscopy (XPS) and Spectroscopic Ellipsometry (SE) Study of Hafnium Silicate Alloys Prepared by Remote Plasma Assisted Chemical Vapor Deposition: Comparisons between Conduction Band Offset Energies and Optical Band Gaps

Monday, November 3, 2003, 10:00 am, Room 317

Session: Electronic Properties of High-k Dielectrics and their Interfaces
Presenter: J.G. Hong, North Carolina State University
Authors: J.G. Hong, North Carolina State University
N.A. Stoute, North Carolina State University
G. Lucovsky, North Carolina State University
D.E. Aspnes, North Carolina State University
Correspondent: Click to Email
Thin films of hafnium silicate alloys, (HfO@sub 2@)@sub x@(SiO@sub 2@)@sub 1-x@, were prepared by remote plasma enhanced chemical vapor deposition (RPECVD) using down-stream injected Hf t-butoxide as the Hf source gas and silane as the Si source gas; chemically-active species from a remotely excited O@sub 2@/He plasma were used to drive the CVD reaction. Alloy compositions were determined by Rutherford backscattering (RBS), and were used to calibrate Hf-to-O spectral ratios obtained by on-line Auger electron spectroscopy (AES). XPS spectra were then obtained for the O 1s, Si 2p, Hf 4d and Hf 4f core levels, and the core level binding energies of these features were analyzed as a function of the alloy composition x. All core binding energy levels decreased (i.e., became more positive) as the Hf fraction x increased, paralleling the behaviors previously reported for O 1s, Si 3p, and Zr 3d core level energy shifts in zirconium silicate alloys. The Hf silicate alloy shifts are consistent with the charge transfer expected on the basis of the relative electronegativities of Hf, Si and O. As in case of Zr silicates, the total shift of the O 1s core level in Hf silicates, ~3.1 eV, is larger than the average shift of the Hf 4d and Si 2p core levels, ~ 2 eV. Finally, the XPS results will be compared with on-line AES, X-ray absorption spectroscopy (XAS), and vacuum ultra-violet spectroscopic ellipsometry (SE) results to determine the compositional variations of the conduction and valence band offset energies with respect to Si, and to compare theses with the compositional variation of the optical band gap.