Electromigration transport mobility associated with pulsed direct current in fine‐grained evaporated Al‐0.5%Cu thin films

Pulsed‐current induced electromigration mass transport velocities have been measured in Al‐0.5%Cu evaporated thin films using the Blech–Kinsbron edge‐displacement technique. The objective was to clarify the dependence of electromigration on pulsed duty cycle (fraction of time that current is on). In the frequency range 0.01–105 Hz, we observe a rate of mass transport per unit of on time which is essentially constant, regardless of duty cycle, so long as the current density is not so high as to produce significant Joule heating on each pulse. Past studies, conducted using current density j at and above 4×106 A/cm2, were difficult to interpret due to the presence of thermal transients as well as the general elevation of temperature above ambient.