Predictive Modeling of Diffusive Failure in Copper Wirebonded Packages

摘要

The desire for lower-cost packages has led to the consideration of copper wire as an alternative to the widespread use of increasingly costly gold wire in semiconductor packages. However, as has been discussed in the literature, copper has a tendency towards electromigration under applied voltages. Therefore, the possibility of wire shorts is a significant concern related to copper wire. This paper assesses the likelihood of encountering diffusive failure in stacked chip-scale packages with copper wire. rnThe paper begins with a review of prior work in the literature on electromigration in general, and copperrelated diffusion in particular. In addition to the many studies in the literature focused on copper diffusion from the metal layers of the die, we leverage understanding of contaminant-induced diffusion in packages to develop a semi-empirical model for predicting failure if copper wire were to be used in place of gold wire. Factors considered include the susceptibility of the package to moisture from the ambient, the presence and nature of contaminants in the package, the voltage bias across the wires, the volume of copper (as dictated by the wire diameter and length), temperature range to which the package is exposed, spacing between copper wires, as well as any defects in the metallic structure of the copper wire. The paper concludes by assessing the viability of the model for predicting diffusion-driven failure in copperwirebonded packages through a comparison with experimental data.