Electromigration in indium thin films

Abstract

Neutron activation and tracer scanning technique is employed to estimate the electromigration shift in indium thin films. The electromigration effective charge number Z* is determined as a function of current density at 399 K and it was noticed that 1.40×104 A/cm2 is the threshold current density at this temperature. The variation of Z* with temperature is studied in the temperature range 352–418 K. The value of Z* is negative in the entire temperature range studied. The magnitude of Z* decreases initially, goes to a minimum at 384 K and increases rapidly above this temperature. Autoradiographs of some of the samples are also given which show the electromigration shift very clearly. The initial decrease in the magnitude of Z* is due to the increase of lattice scattering of electrons and the increase close to the melting point is attributed to the grain boundary melting of the material.