El. Crane et al., Kinetic and mechanistic studies of the chemical vapor deposition of tungsten nitride from bis(tertbutylimido)bis(tertbutylamido)tungsten, J PHYS CH B, 105(17), 2001, pp. 3549-3556
The chemical vapor deposition (CVD) of tungsten nitride from a single sourc
e reagent, bis(tertbutylimido)-bis(tertbutylamido)tungsten ((t-BuN)(2)W(NKB
ut)(2)), is examined with particular focus placed on the mechanisms and ene
rgetics involved in the activation and thermal decomposition of this CVD pr
ecursor. The main reactions that take place are (1) activated adsorption of
the precursor, (2) hydrogen addition/exchange, leading to the evolution of
tert-butylamine, (3) ligand activation via both gamma -hydride activation
and B-methyl elimination processes, and (4) Ligand decomposition via C-N bo
nd rupture. The activation energies fbr each of these processes were examin
ed and found to be similar to 30 kcal/mol for the process(es) leading to th
e evolution of tert-butylamine and similar to 40 kcal/mol for the various r
eactions which lead to the fragmentation of the precursor ligands (pathways
which appear to involve both C-H and C-C bond activation as well as the ru
pture of the ligand C-N bonds). The growth surface of the deposited film co
ntained extensive quantities of carbon in addition to tungsten and nitrogen
. The data also suggest that the growth in UHV does not yield a stable bulk
nitride phase. Rather, it was found that the nitrogen appears to be presen
t at levels consistent with the formation of a solid solution and that anne
aling to 700 K results in the loss of the nitrogen from the bulk film (as N
-2).