Electromigration path in Cu thin-film lines

Electromigration in 0.15-10 mu m wide and 0.3 mu m thick Cu lines deposited by physical vapor deposition has been investigated using both resistance and edge displacement techniques in the sample temperature range 255-405 degrees C. For wide polycrystalline lines (>1 mu m), the dominant diffusion mechanism is a mixture of grain boundary and surface diffusion, while in narrow lines (<1 mm) the dominant mechanism is surface transport. The activation energy for grain-boundary transport is approximately 0.2 eV higher than that of surface transport. (C) 1999 American Institute of Physics. [S0003-6951(99)03920-0].