Test lines of Al were deposited, to a thickness of 0.5, onto thermally oxidized Si. The electrical resistance, degraded by electromigration at low temperatures, was investigated by constant-rate sweeping to temperatures of up to 400K. A recovery (decrease) of the resistance was detected, and a first-order reaction model was used to evaluate the activation energy spectra for this recovery. The energy spectra were found to broaden up to 1.1eV. A comparison of the spectra with the activation energy for the motion of vacancies, and with the spectra for as-deposited films, indicated that the recovery involved multi-energy processes. The relaxation of mechanical stress gradients that built up during direct-current stress tests, the relief of microstructural changes by bulk diffusion that involved the cooperative motion of large groups of atoms, and the formation of vacancy-H complexes as intermediates, were considered as factors which perhaps contributed to the broad activation energy spectra of the recovery.

S.Ohfuji, M.Tsukada: Journal of Applied Physics, 1995, 78[6], 3769-75