Experimental characterization and modeling of the reliability of interconnect trees

Abstract

Interaction of the segments of interconnect trees during electromigration experiments has been studied using several simple tree structures. It is demonstrated that the reliability of a segment can not be predicted without knowledge of the conditions for stress migration and electromigration in connecting segments. Simulations of stress evolution during electromigration in interconnect trees have also been developed, and have been shown to predict behavior consistent with experimental results. Based on experiments and simulations, an analytic model for estimating the reliability of interconnect trees is developed. This analysis is based on calculations of the lifetimes of individual nodes within a tree, by estimating the times for void nucleation, void growth to failure, and formation of extrusions, using current density information for all of the segments connecting at a node. Models, simulations and experimental results on the reliability of interconnect trees are shown to yield mutually consistent results. Accurate circuit-level reliability analyses can not be based on segment-level models, but require instead, tree-based models such as the one developed here.