The migration of Ti in Cu films was studied after the films had been deposited onto a Ti substrate by means of radio-frequency magnetron sputtering. When the film was heated to temperatures of more than 630K in a vacuum, Ti diffused very rapidly through the film and concentrated at the surface. The diffusion coefficient was deduced from the time which was required for the diffusion:

D(m2/s) = 3.5 x 10-5exp[-127(kJ/mol)/RT]

This value was equal to about 65% of that for Ti in bulk Cu. Above 800K, Ti diffused rapidly to the surface of the Cu film and formed intermetallic compounds.

M.Yoshitake, K.Yoshihara: Journal of the Japan Institute of Metals, 1991, 55[7], 773-8