Computational study on transamination of alkylamides with NH3 during metalorganic chemical vapor deposition of tantalum nitride

DFT calculations were employed to investigate transamination during metalorganic chemical vapor deposition (MOCVD) of transition metal nitrides films, such as titanium nitride (TiN) and tantalum nitride (TaN). The calculated energetics and rate constants for the ligand exchange of tert-butylimidotris(dimethylamido) tantalum (TBTDMT) with NH₃ demonstrated that NH₃ addition to form the ammonia adduct, TBTDMT·NH₃, proton transfer and dissociation of dimethylamine to afford net transamination of the dimethylamido ligand are facile even at low temperature (∼300 °C). The transamination of the tert-butylimido ligand, however, was relatively slow at those temperatures but became facile at temperatures appropriate for CVD growth (∼600 °C). Rapid transamination is consistent with lower temperature for growth of TaN by MOCVD in the presence of NH₃, efficient removal of carbon-containing ligands, and incorporation of higher levels of nitrogen in the resulting films.