AVS 46th International Symposium
    Surface Science Division Monday Sessions
       Session SS1+EM-MoA

Paper SS1+EM-MoA10
Nucleation and Growth of Tungsten on SiO@sub 2@ During Atomic Layer Deposition Using Sequential Surface Reactions

Monday, October 25, 1999, 5:00 pm, Room 606

Session: Metals on Oxides
Presenter: J.W. Elam, University of Colorado, Boulder
Authors: J.W. Elam, University of Colorado, Boulder
C.E. Nelson, University of Colorado, Boulder
R.K. Grubbs, University of Colorado, Boulder
S.M. George, University of Colorado, Boulder
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The atomic layer deposition of tungsten (W) can be achieved by separating the binary reaction WF@sub 6@ + Si@sub 2@H@sub 6@ --> W + 2SiHF@sub 3@+ 2H@sub 2@ into two half-reactions. Successive application of the WF@sub 6@ and Si@sub 2@H@sub 6@ half-reactions in an ABAB... sequence produces W atomic layer controlled growth. The nucleation and growth of W on SiO@sub 2@ was examined during alternating exposures to Si@sub 2@H@sub 6@ and WF@sub 6@. Auger electron spectroscopy studies at 573 K revealed an initial nucleation phase that was followed by a layer-by-layer W growth regime. Nucleation occurred during the first 10 sequential Si@sub 2@H@sub 6@ and WF@sub 6@ surface reactions. Layer-by-layer W deposition then proceeded at a growth rate of 2.5 Å per AB reaction cycle. This W growth rate is consistent with one W monolayer per AB reaction cycle. The Auger data was fit well assuming Frank-van der Merwe layer-by-layer growth. These studies reveal that the sequential surface reactions can facilitate metal wetting of oxide surfaces and conformal layer-by-layer metal growth. Additional Auger experiments yielded the adsorption kinetics for both Si@sub 2@H@sub 6@ and WF@sub 6@ during W atomic layer deposition. The WF@sub 6@ half-reaction had an activation energy E=7 kcal/mol and required WF@sub 6@ exposures of 30 L for the WF@sub 6@ half-reaction to reach completion. The Si@sub 2@H@sub 6@ had virtually no temperature dependence and the Si@sub 2@H@sub 6@ half-reaction saturated following 200 L Si@sub 2@H@sub 6@ exposures at 573 K.