AVS 53rd International Symposium
    Electronic Materials and Processing Thursday Sessions
       Session EM2-ThA

Paper EM2-ThA4
Spectroscopic Detection of Electronically Active Defects in Nanocrystalline Ti/Zr/Hf Elemental Oxides

Thursday, November 16, 2006, 3:00 pm, Room 2003

Session: Electronic Properties of High-k Dielectrics, Ferroelectrics, and Their Interfaces
Presenter: H. Seo, NC State University
Authors: G. Lucovsky, NC State University
L.B. Fleming, NC State University
M.D. Ulrich, NC State University
H. Seo, NC State University
N.A. Stoute, NC State University
J. Luning, Stanford Synchrotron Radiation Lab
Correspondent: Click to Email
The performance and reliability of advanced Si field effect transistors (FETs) with high-k transition metal gate dielectrics are limited by intrinsic bonding defects within the nanocrystalline oxides, and at internal device interfaces with i) Si/other semiconductor substrates, and ii) gate metals. This paper employs (a) several spectroscopic approaches: i) near-edge soft-x-ray absorption spectroscopy (NESXAS), ii) soft x-ray photoelectron spectroscopy (SXPS), iii) ultra-violet photoelectron spectroscopy (UPS), and iv) visible and vacuum ultra-violet spectroscopic ellipsometry (VUV SE), and (b) ab initio molecular orbital (MO) theory to study band edge defects. Occupied O-vacancy defect states have been identified at Ti/Zr/HfO@sub 2@ valence band edges by SXPS and UPS. These states have different crystal field splittings for Ti, and Zr and Hf oxides, as expected from the respective 6-fold, and 8-fold coordinations to O. Additionally, occupied defect states display Jahn-Teller term-splittings that remove their respective d-state degeneracies. Transitions from the J-T split ground states to empty defect states below the respective conduction band edges have been identified in O K@sub 1@ NESXAS spectra, epsilon 2 spectra obtained from analysis of VUV SE response functions, and in photoconductivity. Defect densities are ~1-3x10@super -13@ cm@super -2@, consistent with vacancies being clustered along grain boundaries of nanocrystalline oxides. In contrast, these types of defects are not observed spectroscopically in non-crystalline Zr/Hf Si oxynitride alloys, or in ultra thin HfO@sub 2@ dielectrics that have been exposed to post deposition anneals (PDAs) in different nitrogen ambients.