4D Characterization of Damage in Interconnects: Experiment and Simulation

Arizona State University, Scottsdale AZ

Investigators

Abstract

With a continuous downscaling of very large-scale integrated circuits, metallic conductors or interconnects are subject to increasingly high current densities. However, a sufficiently large electric current density can trigger atomic diffusion, known as electromigration (EM), leading to the generation of small defects, ultimately causing circuit failure. Current safety measures adopted in the electronics industry to mitigate EM-induced damage are unreliable, as they are typically based on limited insights provided by two-dimensional imaging of the microstructural degradation process. For complete understanding of the process, a full three-dimensional image of the interconnects is needed, combined with the fourth dimension of time, to understand the degradation process as it proceeds. To achieve this "four-dimensional" (4D) imaging, advanced x-ray tomography is combined with computational simulations of the degradation process. This award supports research to apply this unique 4D imaging to determine the fundamental mechanisms of EM-mediated damage mechanisms in Pb-free interconnects and solder materials used in integrated circuits where high current densities are prevalent. New knowledge gained from this study will guide future strategies aimed at mitigating the EM-induced failure of miniaturized circuits used in advanced microprocessors. The new knowledge has broad application in the microelectronics industry, with substantial economic implications. Research in this project will enhance materials education via the creation of material-microstructure simulation and visualization software, and create public awareness through the launch of a new website to expose the complexity of 3D microstructures. The aim of this research project is to devise an integrated experimental and computational approach to achieve a fundamental understanding of the underlying mechanisms that accompany microstructural degradation in Sn- and In-based, Pb-free interconnects and solders. The investigators will utilize real-time 4D X-ray imaging, diffraction contrast tomography, and phase-field modeling to predict the onset and growth of EM-mediated defect patterns in multiphase, multicomponent electronic materials. The following challenges will be addressed: (1) Accelerated failure testing and 4D (3 spatial dimensions and time) in-situ characterization of microdefect evolution under EM conditions (2) Formulating phase-field models for large-scale 3D simulations of defect pattern formation in BCT Sn-crystals that exhibit anisotropic diffusion and incorporating the multiphysics of Joule heating, back-stress, and thermomigration, and (3) Validating the phase-field model using the in-situ 4D datasets obtained from accelerated EM-failure tests by starting from the same initial state. The new knowledge to be gained from this work will enhance current capabilities to predict the onset of EM damage and at the same time enable new strategies for controlling EM-mediated failure of solders and interconnects, efficiently. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.