AVS 49th International Symposium
    Thin Films Wednesday Sessions
       Session TF-WeA

Paper TF-WeA1
Influence of Film Roughness on the Electrical Properties of W / Al@sub 2@O@sub 3@ Films Grown on Si(100) by Atomic Layer Deposition

Wednesday, November 6, 2002, 2:00 pm, Room C-101

Session: Atomic Layer Deposition - Applications of ALD
Presenter: F.H. Fabreguette, University of Colorado
Authors: F.H. Fabreguette, University of Colorado
M.D. Groner, University of Colorado
Z.A. Sechrist, University of Colorado
S.M. George, University of Colorado
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The SiO@sub 2@ interfacial layer seriously impacts the electrical behavior of alumina high k dielectrics on silicon substrate, and produces a reduction of the overall dielectric constant with decreasing thickness of the high k dielectrics. To avoid the SiO@sub 2@ interfacial layer and probe the electrical properties of ultrathin dielectrics, Al@sub 2@O@sub 3@ layers were grown on tungsten on Si(100) using Atomic layer Deposition (ALD) technique. Si/W/Al@sub 2@O@sub 3@ structures are expected to exhibit a dielectric constant independent of the Al@sub 2@O@sub 3@ film thickness, because the tungsten layer should act as an equipotential electrode. These Si/W/Al@sub 2@O@sub 3@ structures were grown in a viscous flow ALD reactor using Al(CH@sub 3@)@sub 3@ and H@sub 2@O for the Al@sub 2@O@sub 3@ ALD, and WF@sub 6@ and Si@sub 2@H@sub 6@ for W ALD. The W thickness was kept constant while the Al@sub 2@O@sub 3@ thickness was varied. Ellipsometry was used to measure the Al@sub 2@O@sub 3@ ALD film thickness. Surface roughness was measured using Atomic Force Microscopy. The dielectric constant calculated from C-V curves was apparently reduced for the smaller Al@sub 2@O@sub 3@ thicknesses, even though impedance spectroscopy did not exhibit any interfacial oxide. By comparing this apparent dielectric constant reduction and the film roughness, the apparent reduction was discovered to be linked with the film roughness. The film roughness was then minimized using a Hadamard matrix optimization approach to adjust the various ALD parameters. With the surface roughness minimized, Si/W/Al@sub 2@O@sub 3@ structures were fabricated where the Al@sub 2@O@sub 3@ dielectric constant was almost independent of the Al@sub 2@O@sub 3@ layer thickness.