TaN deposited by magnetron sputtering had application in semiconductor interconnect structures as a diffusion barrier and adhesion layer. TaN used in these applications had a hexagonal or cubic structure consistent with roughly 1:1 Ta:N levels, with a bulk resistivity of 300 to 500µΩcm and a diffusion barrier failure temperature, for 5nm films, of about 650C. The diffusion barrier failure temperature (for Si/TaN-barrier/Cu samples) was a strong function of N concentration in the TaN; at the highest N levels (equivalent to nearly Ta3N5), the failure temperature exceeded 900C. At intermediate compositions, the failure temperature was found to exceed 700C even for films as thin as 0.4nm. This suggested an interfacial contribution to diffusion barrier effectiveness, in addition to conventional grain boundary or bulk interdiffusion resistance, which may dominate conventional grain boundary diffusion.

Diffusion Barrier Properties of Very Thin TaN with High Nitrogen Concentration. S.M.Rossnagel, H.Kim: Journal of Vacuum Science & Technology B, 2003, 21[6], 2550-4