Investigation of via Bottom Barrier Integrity Impact on Electromigration

In this paper we will present results indicating a dramatic change in the electromigration failure behavior based on a clearly different root cause then the well known failures for up stream (Fischer et al., 2000) and down stream electron flow direction (Li et al., 2006) (standard failures). It is mainly evident in up stream directions and can be forced by specific tooling configuration and integration schemes. Due to a specially designed test structure, the failure type (long runner) can be detected in regular electromigration (EM) testing by differences in the resistance behavior compared to the standard failure. Due to extensive testing and failure analysis we have been able to present a clear correlation between the via-bottom-barrier integrity and the change in failure location. This yields new limiting aspects in via integration which needs to be considered for reliable products.