Evolution of 1/f^α 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/f^α 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 S_V(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/f^3/2 component, which starts to contribute as the electromigration process progresses. This additional component S_V(f)∼1/f^3/2 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.