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Homogeneous Decomposition of Aryl-and Alkylimido Precursors for the Chemical Vapor Deposition of Tungsten

Summary: Homogeneous Decomposition of Aryl- and Alkylimido
Precursors for the Chemical Vapor Deposition of Tungsten
Nitride: A Combined Density Functional Theory and
Experimental Study
Yong Sun Won, Young Seok Kim, Timothy J. Anderson,,* Laurel L. Reitfort,
Ion Ghiviriga, and Lisa McElwee-White,*
Contribution from the Department of Chemical Engineering, UniVersity of Florida,
GainesVille, Florida 32611-6005, and Department of Chemistry, UniVersity of Florida,
GainesVille, Florida 32611-7200
Received March 30, 2006; Revised Manuscript Received July 18, 2006; E-mail: lmwhite@chem.ufl.edu
Abstract: MOCVD growth of tungsten nitride (WNx) and tungsten carbonitride (WNxCy) thin films has been
reported from the complexes Cl4(CH3CN)W(NR) (1: R ) Ph; 2: R ) iPr; 3: R ) C3H5). To evaluate the
role of the imido substituent in film growth, gas-phase homogeneous decomposition of precursor molecules
was investigated using density functional theory (DFT) calculations. Computational results and NMR kinetics
of acetonitrile exchange by 2 in solution verified that dissociation of the acetonitrile ligand should be facile
for 1-3 in the temperature range used for film growth (>450 C). A computational search for transition
states for cleavage of W-Cl bonds in the presence of H2 carrier gas was consistent with a -bond metathesis
pathway. Natural bonding orbital (NBO) analysis and bond energy calculations indicated that 1 has a stronger
N-C(imido) bond and a slightly weaker W-N bond than 2 and 3, suggesting a greater role for W-N bond
cleavage in depositions from 1. These results are consistent with mass spectrometric fragmentation patterns


Source: Anderson, Timothy J. - Chemical Engineering Department, University of Florida


Collections: Materials Science