Cl4(PhCN)W(NPh) as a single-source MOCVD precursor for deposition of tungsten nitride (WNx) thin films

The tungsten phenylimido complex Cl4(PhCN)W(NPh) (2b) was tested as a single-source precursor for growth of tungsten nitride (WNx) thin films, and results were compared to films previously deposited from the isopropylimido complexes Cl4(RCN)W(NiPr) (1a, R=CH3; 1b, R=Ph). Films deposited from 2b exhibited growth rates ranging from 2 to 21 Å min−1 over a temperature range of 475–750 °C, and the apparent activation energy for film growth in the kinetically controlled regime was 1.41±0.58 eV. Amorphous β-WNx films were deposited below 500 °C, with minimum film resistivity and sheet resistance of 225 μΩ-cm and 75 Ω/□, respectively, observed for deposition at 475 °C. In contrast, films deposited from the isopropylimido complexes 1a,b exhibited higher growth rates and higher nitrogen content over a similar temperature range. These differences are attributed to the higher dissociation energy of the imido NC bond in phenylimido complex 2b. Mass spectrometry fragmentation patterns are consistent with this behavior.