Electromigration in Cu/W Structure

Abstract

Mass transport by electromigration in sputtered Cu line segments on a continuous W line has been measured using the drift velocity technique at temperatures from 166 to 396 °C. The Ta/Cu/Ta line segments are patterned by dry etching techniques. Cu mass depletion (voids) at the cathode end and accumulation (hillocks) at the anode were measured as a function of time from scanning electron microscope micrographs. The edge displacement of Cu was found to increase linearly with time. The activation energy for Cu electromigration drift velocity, which relates to the product of effective charge number and diffusivity, Z*D, is found to be 0.6 eV.