Three mechanisms were proposed for the formation of Cu diffusion channels in the Ta layer of a Cu/Ta/SiO2/Si structure. Firstly, it was suggested that stacking faults which formed during the recovery process introduced localized regions of high internal energy into the Ta layer; from which Cu channels originated. Secondly, chemical reactions occurred at 800C and formed Ta4CuO11 across the Cu/Ta interface in Cu and Ta layers; thus opening up channels for Cu diffusion. Thirdly, triple junctions at the grain boundary

of the Cu and Cu/Ta interface provided sites for the initiation of channel formation at 800C. At 950C, these channels were absent from the diffusion barrier, but the Ta was oxidized into disordered Ta2O5 that could contain pathways for Cu diffusion.

Formation of Cu Diffusion Channels in Ta Layer of a Cu/Ta/SiO2/Si Structure. S.Li, Z.L.Dong, K.M.Latt, H.S.Park, T.White: Applied Physics Letters, 2002, 80[13], 2296-8