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. It was found that the pre-exponential factor was equal to 3.5 x 10-5m2/s and the activation energy was equal to 127kJ/mol. This value was equal to about 65% of that for Ti in bulk Cu. At temperatures 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