(92c) Chemical Vapor Deposition of WNxCy for Diffusion Barrier Application Using a Tungsten Diphenylhydrazido Complex

The tungsten diphenylhydrazido complex Cl₄(CH₃CN)W(NNPh₂) (1) was used for film growth of tungsten carbonitride (WN_xC_y) by metal-organic chemical vapor deposition (MOCVD) using H₂ carrier in the temperature range 300 to 700 °C.  The effects of deposition temperature and added NH₃ on the film microstructure, chemical composition, bonding states, surface morphology, growth rate, and electrical resistivity were studied.  The microstructure of films deposited with NH₃ was X-ray amorphous below 450 °C and polycrystalline at and above this temperature.  The chemical composition of films deposited with NH₃ exhibited increased N levels between 400 and 700 °C and decreased C levels at and between 300 and 400 °C as compared to films deposited without NH₃.  XPS measurements revealed that W is primarily bonded to N and C for films deposited between 300 and 700 °C.  An Arrhenius plot of growth rate was consistent with reaction limited growth, and the activation energy was lower for growth in the presence of NH₃. It was also observed that the surface roughness improved with added NH₃.  The measured value of the electrical resistivity fluctuated with growth temperature primarily as a result of composition and phase constitution changes.  Diffusion barrier properties were investigated from Cu/WN_xC_y/Si stacks consisting of 100 nm Cu deposited at room temperature by reactive sputtering on a 15 nm WN_xC_y film deposited at 400 °C by MOCVD.  The performance of the diffusion barrier was determined by XRD patterns, cross-sectional TEM and SEM surface images, EDS depth profiles, and four-point probe measurements.  Cu/WN_xC_y/Si stacks annealed at 500 °C for 30 min maintained their integrity at both the Cu/WN_xC_y and WN_xC_y/Si interfaces.  Samples annealed at higher temperature showed evidence of failure only when annealed at 700 °C.  These results support the conclusion that WN_xC_y thin film deposited from 1 is a viable Cu diffusion barrier material. The properties of thin films deposited with 1 and the tungsten imido complexes Cl₄(CH₃CN)W(NR) (R = Ph, ⁱPr, and allyl)¹ are compared to provide insight into the effect of hydrazido and imido ligands on film properties.

¹O. J. Bchir, K. M. Green, H. M. Ajmera, E. A. Zapp, T. J. Anderson, B. C. Brooks, L. L. Reitfort, D. H. Powell, K. A. Abboud and L. McElwee-White, J. Am. Chem. Soc. 127, 7825-7833 (2005).