Neutron Diffraction Measurement of Electromigration-Induced Stressess in Lead-Free Alloy

Passing high electric current through an electrical interconnect causes atomic migration in the direction of electron flow, i.e. electromigration, which leads to accumulation and depletion of atoms. This generates local mechanical stresses and can result in the formation of whiskers for stress relaxation and electrical failure ofthe interconnect. The electromigration-induced stresses remain poorly investigated at both the microscale and the nanoscale even though it plays an important role in determining the performance and reliability of microelectronic devices. This project will exploit neutron diffraction to illuminate the evolution of stresses induced by electromigration. The major factor of interest is the gradient of the electromigration-induced stresses across a specimen and its dependence on electric current density. It constitutes the first step to investigate the interaction and relationship among microstructure, mechanical behavior and electromigration with the aim of identifying a parametric approach to the prediction of stresses at electrical interconnects in microelectronic devices. It provides a vehicle for the PIs to establish international collaboration and for graduate students to expand their international experience in materials research. The characterization of the electromigration-induced stresses is a challenging scientific effort, and successful completion of the project will have direct impact on the optimum design and structural analysis of electrical interconnects in microelectronic packaging technology. The results will help researchers at the University of Kentucky seek local and federal funding to establish a strong research team exploiting neutron diffraction to characterize mechanical behavior of advanced materials on the nanoscale.