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
$\boldsymbol{D}_{\boldsymbol{eff}}$
, charge number
$\boldsymbol{Z}^{\ast}$
and effective modulus
$\boldsymbol{B}$
. 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.