AVS 47th International Symposium
    Thin Films Monday Sessions
       Session TF-MoA

Invited Paper TF-MoA3
Tungsten Atomic Layer Deposition: Nucleation and Growth on Oxide Surfaces

Monday, October 2, 2000, 2:40 pm, Room 203

Session: Atomic Layer Chemical Vapor Deposition II
Presenter: S.M. George, University of Colorado
Authors: S.M. George, University of Colorado
J.W. Klaus, University of Colorado
J.W. Elam, University of Colorado
C.E. Nelson, University of Colorado
R.K. Grubbs, University of Colorado
S.J. Ferro, University of Colorado
Correspondent: Click to Email
Tungsten atomic layer deposition (ALD) can be accomplished by separating the binary reaction WF@sub6@ + Si@sub2@H@sub6@ --> W + 2SiHF@sub3@ + 2H@sub2@ into two self-limiting half-reactions.@footnote 1@ The two self-limiting half-reactions are: (A) W-SiHF@sub2@* + WF@sub6@(g) --> W-WF@sub5@*+ SiHF@sub3@(g); and (B) WF@sub5@* + Si@sub2@H@sub6@(g) --> W-SiHF@sub2@* + 2H@sub2@(g) + SiHF@sub3@(g). In situ FTIR spectroscopy studies have determined the temperatures and pressures required for these two half-reactions to reach completion. In situ spectroscopic ellipsometry studies have examined the growth of W ALD films. Successive exposure to WF@sub6@ and Si@sub2@H@sub6@ in an ABAB... reaction sequence produced W ALD at a rate of 2.5 Å per AB cycle at 425 K. The nucleation and growth during W ALD on SiO@sub2@ and Al@sub2@O@sub3@ surfaces have also been studied using Auger electron spectroscopy (AES). The AES results displayed an initial nucleation period of several AB cycles. After the deposition of one tungsten monolayer, the AES signals for W and Si oscillated dramatically versus WF@sub6@ and Si@sub2@H@sub6@ exposures. These studies indicated that W ALD displays nearly ideal layer-by-layer (Frank van der Merwe) growth after the initial nucleation period. W ALD can be used together with Al@sub2@O@sub3@ ALD@footnote 2@ to fabricate W/Al@sub2@O@sub3@/W/Al@sub2@O@sub3@ nanolaminates. Cross-sectional transmission electron microscopy (TEM) studies have examined the W/Al@sub2@O@sub3@/W/Al@sub2@O@sub3@ nanolaminates deposited on Si(100). The growth of the nanolaminates is dependent on the details of the surface chemistry during the nucleation of W ALD on Al@sub2@O@sub3@. @FootnoteText@ @footnote 1@ J.W. Klaus, S.J. Ferro and S.M. George, Thin Solid Films 360, 145 (2000). @footnote 2@ A.W. Ott, J.W. Klaus, J.M. Johnson and S.M. George, Thin Solid Films 292, 135 (1997).