It was noted that the changes in electrical resistance, which were caused by electromigration in short (3 to 100) pure Al lines, exhibited a well-defined behavior. An applied direct current could cause an increase or decrease in the resistance. At current densities which were below a critical value, the resistance change saturated with time and the resistance recovered fully when the current ceased. The length and temperature dependences of the resistance changes indicated that the observed time dependence was determined by grain boundary diffusion along the entire line length. At currents which were above the critical current density, the resistance changes did not fully recover. Within experimental accuracy, the product of the critical current density and the line length was equal to a constant. The value of this product was in good agreement with the values of the product of threshold current density and line length which were found in the case of drift velocity experiments.

J.R.Kraayeveld, A.H.Verbruggen, A.W.J.Willemsen, S.Radelaar: Applied Physics Letters, 1995, 67[9], 1226-8