AVS 46th International Symposium
    Thin Films Division Tuesday Sessions
       Session TF-TuM

Paper TF-TuM7
Relating Phase Content to Deposition Kinetics in Ultra-Thin Sputtered Tantalum Films

Tuesday, October 26, 1999, 10:20 am, Room 615

Session: Advanced Thin Film Formation Chemistry
Presenter: J.F. Whitacre, University of Michigan
Authors: J.F. Whitacre, University of Michigan
Z.U. Rek, Stanford Synchrotron Radiation Laboratory
S.M. Yalisove, University of Michigan
J.C. Bilello, University of Michigan
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How phase and stress formation relate to adatom kinetics in extremely thin sputtered Ta films was examined. This was accomplished by controlling the adatom kinetic energy distribution at the substrate during growth. If low sputter gas (Ar) pressures are used (less than 5 mTorr), arriving adatoms have kinetic energies on the order of 10 eV as they impinge upon the substrate. At pressures above 15 mTorr, the energy distribution shifts to the thermal regime, where all atoms have energies less than 1 eV. For this experiment, Ta films 25 to 500 Å in thickness were DC magnetron sputter deposited using Ar pressures ranging from 2 to 20 mTorr. The films were analyzed using a synchrotron x-ray source (SSRL beamline 7-2) in conjunction with a four-circle diffractometer aligned in the grazing incidence x-ray scattering (GIXS) geometry. The stress in these films was calculated using double crystal diffraction topography (DCDT, a wafer curvature method) data. Film nanostructure was examined using TEM analysis. Phase content was determined by modeling ideal polycrystalline x-ray diffraction patterns and comparing them with corrected (for air scattering) diffraction data. It was found that films grown at progressively higher pressures displayed a systematic increase in amorphous content. Film grown using 20 mTorr of Ar were 100% amorphous to thicknesses as great as ~150Å. Residual stress analysis showed that all films less than 100 Å thick had compressive stresses on the order of -2 GPa. These results are discussed in context of a model that relates adatom kinetics, surface diffusion, and grain development during the early stages of film growth. Work supported by ARPA under contract No. DAAH-04-95-1-0120. Work done (partially) at SSRL, which is operated by the Department of Energy, Office of Basic Energy Sciences.