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

Paper DI-TuM11
Novel Ultra-thin TiAlO@sub x@ Alloy Oxide for New Generation of Gate Dielectric

Tuesday, November 4, 2003, 11:40 am, Room 317

Session: High-k Dielectric Growth and Processing
Presenter: W. Fan, Northwestern University
Authors: W. Fan, Northwestern University
S. Saha, Argonne National Laboratory
B. Kabius, Argonne National Laboratory
J.M. Miller, Argonne National Laboratory
J.A. Carlisle, Argonne National Laboratory
O. Auciello, Argonne National Laboratory
S.Y. Li, Northwestern University
V.P. Dravid, Northwestern University
R.P.H. Chang, Northwestern University
C. Lopes, University of North Carolina, Chapel Hill
E.A. Irene, University of North Carolina, Chapel Hill
Correspondent: Click to Email
A novel TiAlO@sub x@ alloy oxide has been developed and studied as an alternative gate oxide material for CMOS devices (patent pending). Ultra-thin TiAl (3:1) films with physical thickness 3-20 nm were grown on n-Si (100) by sputter deposition. In-situ oxidation was then performed by using both molecular oxygen (P=1.0x10@super -3@ Torr) and atomic oxygen sources (P=1.0x10@super -4@ Torr). The formed TiAlO@sub x@ exhibits amorphous structure on Si, as revealed by XRD and TEM analyses. In-situ XPS study shows that a full oxidation of TiAl can be achieved at 500@super o@C using both oxygen sources. However, the TiAlO@sub x@ layer formed through atomic oxygen annealing presented a leakage current 150 times lower than the one with molecular oxygen annealing. Since both Ti and Al have more negative oxide formation energies than Si, the presence of Ti and Al at the interface with Si significantly reduces the formation of interfacial SiO@sub x@. It has been confirmed by XPS depth profile, ellipsometry and cross-sectional TEM, which revealed ~1 nm SiO@sub x@ layer formed at the oxide/semiconductor interface with 500@super o@C oxidation. The amorphous TiAlO@sub x@ layer with equivalent oxide thickness (EOT) of 1.7 nm and negligible hysteresis was obtained via atomic oxygen exposure at 500@super o@C, exhibiting high permittivity (~30) and low leakage current density (1.2x10@super -2@ A/cm@super 2@). After post deposition annealing with top gate electrode in place, the leakage was further improved and reached 5.4x10@super -5@ A/cm@super 2@. Furthermore, extended study shows that a full transition of TiAl to TiAlO@sub x@ can be accomplished at room temperature by exposure to atomic oxygen beam. Interfacial SiO@sub x@ formation, therefore, was completely eliminated and TiAlO@sub x@ layer with EOT less than 1 nm was achieved on Si. @FootnoteText@*This work was supported by the U.S. Department of Energy, BES-Materials Sciences, under Contract W-31-109-ENG-38.@.