The properties of Cu/W/Ta–W–N/Si film stacks were studied, and it was found that adding a thin W layer to a stable Ta–W–N diffusion barrier significantly affected the overall metallization system. The introduction of a thin W interlayer caused a significant change of the system while increasing the stability of the film. The tandem barrier was demonstrated to be stable up to 800C by the performed analytical barrier tests.

Diffusion Barrier Performance of W/Ta–W–N Double Layers for Cu Metallization. S.Song, Y.Liu, M.Li, D.Mao, C.Chang, H.Ling: Microelectronic Engineering, 2006, 83[3], 423-7