Carbide films were grown by chemical vapor deposition, using W(CO)6 and C2H4, between 250 and 450C. Pyrolysis studies indicated that W(CO)6 thermally decomposed at 150 to 200C; with or without ethylene. The C incorporation increased from 13 to about 33% when C2H4 was co-fed with W(CO)6. The W/C ratio, as established by X-ray photo-electron spectroscopy, remained at about 2:1; regardless of the C2H4 to W(CO)6 flow ratio, for temperatures of 250 to 450C. Films (50nm-thick) grown at 290C had a resistivity of 250μΩcm. Above 500C, the W/C ratio decreased to about 1:1.25 and the resistivity increased to 535μΩcm. The use of X-ray diffraction, X-ray photo-electron spectroscopy, selected-area electron diffraction and transmission electron microscopy revealed that the films were a mixture of 5 to 6nm W2C crystallites in an amorphous matrix, whose stoichiometry was about 2:1 W/C. It was found that Cu did not diffuse through 7nm-thick WC films in Cu/WC/SiO2 stacks that were annealed (400C, 8 to 9h).

Low Temperature Chemical Vapor Deposition of Tungsten Carbide for Copper Diffusion Barriers. Y.M.Sun, S.Y.Lee, A.M.Lemonds, E.R.Engbrecht, S.Veldman, J.Lozano, J.M.White, J.G.Ekerdt, I.Emesh, K.Pfeifer: Thin Solid Films, 2001, 397[1-2], 109-15