Elasticity and resistivity study on the electromigration effects observed in aluminum–silicon–copper alloy thin films

The early electromigration (EM) processes in the Al–Si(Cu) thin films several tens of nanometers thick deposited on Si reed substrates were investigated by means of the simultaneous anelasticity and electrical resistivity measurements below 360 K. The grain growth, the shortening of a⊥ and the probable lengthening of a∥ take place during the EM tests at the current density of 108 A/m2, where a⊥ and a∥ denote the atomic plane spacing normal to and the one parallel to the film surface, respectively. The activation energy, EGB, for the grain growth is found to be as low as 0.32 eV, possibly suggesting that EGB in very thin nanometer-thick films is much lower than that found in thin micrometer-thick films. The increase in the Young’s modulus of the Al–Si(Cu) thin films takes place during the EM tests, suggesting that the grain growth is responsible for it. The decrease in Q−1 observed at 330 and 360 K may be explained by a decrease in the grain boundary regions too. The increase in Q−1 found during the EM tests at 300 K is possibly associated with an increase in a certain anelastic process in the grain boundary regions.