The surface diffusion coefficient of Cu on Ta substrates was determined via Ostwald ripening. It was shown that impurities such as O strongly influenced the kinetics of de-wetting of Cu films on Ta substrates. Two interfaces with Cu were investigated: Cu/β-Ta and Cu/α-Ta. For Cu surface diffusion on the β-Ta surface, a surface diffusion coefficient of 2.6 x 10-11cm2/s was measured at 550C. The temperature dependence of surface diffusion was investigated between 400 and 550C, indicating a relationship of the form:

D (cm2/s) = 2.8 x 10-6 exp[-0.83(eV)/kT]

A diffusion coefficient of 2.0 x 10-12cm2/s was measured at 550C for Cu surface diffusion on the α-Ta surface.

F.Fillot, Z.Tőkei, G.P.Beyer: Surface Science, 2007, 601[4], 986-93