Activation energy for electromigration in aluminum films alloyed with copper

The rate of electromigration in thin films of aluminum and aluminum alloyed with copper has been determined by measuring the changes in resistance of stripes subjected to a current density of 4 × 106 A/cm2. At temperatures in the range from 100 to 200°C the activation energy for electromigration has been found to have the same value for both the pure and the copper-alloyed samples, namely, 0.6 eV. However, the rate of migration is much smaller, by a factor as large as 100, in the copper-bearing samples. These results are discussed in terms of grain boundary diffusion and the effect of alloying additions on diffusion mechanisms.