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-TuA4
Ta d-state Derived Electron Traps in non-Crystalline Al@sub 2@O@sub 3@-Ta@sub 2@O@sub 5@ Alloys Prepared by Remote PECVD

Tuesday, October 30, 2001, 3:00 pm, Room 130

Session: High K Dielectrics III
Presenter: R.S. Johnson, North Carolina State University
Authors: R.S. Johnson, North Carolina State University
J.G. Hong, North Carolina State University
G. Lucovsky, North Carolina State University
Correspondent: Click to Email
The bonding coordination of Al and Ta in Al@sub 2@O@sub 3@ and Ta@sub 2@O@sub 5@ is known, respectively, from Al27 nuclear magnetic resonance, NMR,@footnote 1@ and X-ray diffraction, XRD.@footnote 2@ There are 4- and 6-fold coordinated Al-atoms in non-crystalline Al@sub 2@O@sub 3@ and these are bonded to 3-fold coordinated O-atoms. XRD of high temperature crystalline Ta@sub 2@O@sub 6@ indicates a mix 6- and 8-fold coordinated Ta, with 2- and 3-fold coordinated O-atom neighbors. FTIR and Raman studies confirm similar bonding arrangements in non-crystalline Ta@sub 2@O@sub 5@. Non-crystalline Al@sub 2@O@sub 3@-Ta@sub 2@O@sub 5@alloys have been prepared by remote PECVD. Robertson@footnote 3@ has shown that the anti-bonding Ta d-state energy levels are significantly below the p-states of Al and Si and cause a reduced conduction band offset with Si of ~0.36 eV. Miyazaki@footnote 4@ has measured band offsets by photoemission and has found good agreement with theory. The temperature dependence of C-V and J-V traces for capacitors with Al@sub 2@O@sub 3@-Ta@sub 2@O@sub 5@ dielectrics indicate trapping and trap release that is consistent with the trapping states being associated with anti-bond d-states of Ta. In particular, hysteresis in the C-V traces is consistent with electron trapping, and is significantly increased by addition of Ta@sub 2@O@sub 5@ into Al@sub 2@O@sub 3@. The temperature dependence of J-V traces, combined with the C-V traces is consistent with different activation energies for electron trapping, and trap release. The energies obtained from analysis of the data are in agreement with conduction band offset energies determined from the photoemission studies of Miyazaki.@footnote 4@ The activation for electron injection into Ta trapping states is 0.30±0.05 eV, consistent with the energy of empty Ta-atom d-states relative to the Si conduction band. The activation energy for trap release is 1.5±0.1 eV, in agreement with the energy difference between these Ta d-states and the Al@sub 2@O@sub 3@ conduction band position as determined from band offset energy measurements.@footnote 4@ Supported by the Office of Naval Research and the SEMATECH/SRC Front End Processing Center @FootnoteText@ @footnote 1@ D. Muller, W. Gessner, H.J. Behrens, and G. Scheller, Chem. Phys. Lett. 59, 79 (1981). @footnote 2@ N.C. Stephenson and R.S. Roth, J. Solid State Chem. 3, 145 (1971). @footnote 3@ J. Robertson, J. Vac. Sci. Technol. B 18, 1785 (2000). @footnote 4@ S. Miyazaki, presented at PCSI 28, Lake Buena Vista, FL, 7-11 January 2001, submitted to J. Vac. Sci. Tech. B (2001).