A Novel Method for the Determination of Electromigration-Induced Void Nucleation Stresses

The experimental determination of electromigration-induced critical stresses leading to void nucleation has been a complex endeavor across the past several decades. In this study, we propose a combination of single link electromigration testing, augmented by large scale statistical evaluations using Wheatstone Bridges, as well as detailed physics-based simulations to arrive at the extraction of the critical stresses which lead to void nucleation and further growth. The calibration efforts lead to well-matched values in terms of basic physical parameters such as effective diffusivity D-eff, charge number Z* and effective modulus B. Furthermore, the statistical distribution of single link Kelvin structure and Wheatstone Bridge failure times is reproduced very well, ruling out an early nucleation mechanism close to the 4-sigma level. The calibration of the complex simulation model, based on a large experimental database, opens up the path to a much-improved chip-level reliability assessment process.