Evolution of 1∕fα noise during electromigration stressing of metal film: Spectral signature of electromigration process

Abstract

In this paper we report a systematic study of low-frequency 1∕fα resistance fluctuation in a metal film at different stages of electromigration. The resistance fluctuation (noise) measurement was carried out in presence of a dc electromigration stressing current. We observe that in addition to the increase in the spectral power SV(f), the frequency dependence of the spectral power changes as the electromigration process progresses and the exponent α starts to change from 1 to higher value closer to 1.5. We interpret this change in α as arising due to an additional contribution to the spectral power with a 1∕f3∕2 component, which starts to contribute as the electromigration process progresses. This additional component SV(f)∼1∕f3∕2 has been suggested to originate from long range diffusion that would accompany any electromigration process. The experimental observation finds support in a model simulation, where we also find that the enhancement of noise during electromigration stressing is accompanied by a change in spectral power frequency dependence.