INTERDIFFUSION OF CU SUBSTRATE ELECTRODEPOSITS FOR CU/CO, CU/CO-W, CU/CO/NI AND CU/CO-W/NI SYSTEMS/

The interdiffusion of electrodeposited Ni, Co and Co-W with Cu substra te were studied, at temperature ranging from 400 to 800 degrees C, usi ng energy dispersive X-ray spectroscopy (EDS). Chemical interdiffusion coefficients were calculated using the Boltzmann-Matano analysis. Int ermetallic phase formation was studied by X-ray diffraction (XRD) and microstructures were observed with a scanning electron microscopy (SEM ). No remarkable interdiffusion was observed in the Cu/Co and Cu/Co-W systems up to 800 degrees C. However, after annealing at 400-800 degre es C for the Cu/Co/Ni system, accumulation of Cu atoms was found at th e Co/Ni interface in which Cu had further diffused into the Ni electro deposit. It is suggested that Cu diffuses through the Co layer by the grain-boundary diffusion mechanism. Interdiffusion of Cu through elect roplated Co coating to Ni was compared with electroplated alloy coatin g of 65 wt.% co-35 wt.% W. The structure of the Co-W coating has chang ed from a mixture of Go-like hcp and fee structures to a solely fee st ructure upon annealing at 1100 degrees C for 90 min. The diffusion bar rier properties of Co and Co-W were compared with those of Ni. The res ults show that Co is a more effective barrier than Ni for Cu diffusion up to 219 h at 400 degrees C. A Co-W alloy coating, of 36 wt.% W, is a more effective barrier for Cu diffusion than Ni heated up to 72 h at 500 degrees C. However, interpenetration of Cu through Co is more pro nounced than diffusion of Cu through Ni for temperatures ranging from 500 to 800 degrees C. Interdiffusion of Cu through the Co-36 wt.% W co ating is more pronounced than diffusion of Cu through Ni for temperatu res ranging from 600 to 800 degrees C whereas Co-W is a more effective barrier than Co for Cu diffusion. (C) 1998 Elsevier Science S.A.