The tungsten piperidylhydrazido complex Cl-4(CH3CN)W(N-pip) (1) was used for film growth of tungsten carbonitride (WNxCy) by metal-organic chemical vapor deposition (CVD) in the absence and presence of ammonia (NH3) in H-2 carrier. The microstructure of films deposited with NH3 was x-ray amorphous between 300 and 450 degrees C. The chemical composition of films deposited with NH3 exhibited increased N levels and decreased C levels over the entire deposition temperature range (300-700 degrees C) as compared to films deposited without NH3. As determined by x-ray photoelectron spectroscopy, W is primarily bonded to N and C for films deposited at 400 degrees C, but at lower deposition temperature the binding energy of the W-O bond becomes more evident. The growth rates of films deposited with NH3 varied from 0.6 A degrees/min at 300 degrees C to 4.2 A degrees/min at 600 degrees C. Over 600 degrees C, the growth rate decreased when using NH3 presumably due to parasitic gas phase reactions that deplete the precursor. Diffusion barrier properties were investigated using Cu/WNxCy/Si stacks consisting of 100 nm Cu deposited at room temperature by reactive sputtering on a 20 nm WNxCy film deposited at 400 degrees C by CVD. X-ray diffraction and cross-sectional transmission electron microscopy were used to determine the performance of the diffusion barrier. Cu/WNxCy/Si stacks annealed under N-2 at 500 degrees C for 30 min maintained the integrity of both Cu/WNxCy and WNxCy/Si interfaces.