Electromigration is a type of failure that occurs in metals used both in the semiconductor industry and in new technologies such as wearable and flexible electronics. In this type of failure, small metallic lines used to conduct electricity (so-called interconnects) develop microscopic voids and ultimately break due to a large amount of electrical current, leading to the overall failure of the electronic device. It is known that electromigration is controlled by the structure of the metallic material, in particular how its atoms are arranged. In typical metals, certain regions (called grain boundaries) display large levels of disorder in the atomic arrangement, and this is known to facilitate failure by electromigration. In this project, new kinds of nanoscale metallic materials with well-ordered atomic structures (so-called twin boundaries), and thus a high potential to prevent electromigration, will be studied. Electromigration is a barrier for the progress of the electronic industry, hampering further miniaturization and greater reliability. In the case of the new wearable and flexible electronic technologies, it limits broader mass-market applications. The understanding of electromigration in metals with twin boundaries emerging from this research will contribute to remove these difficulties, and enable new directions in the design of interconnects. Furthermore, mentoring and research opportunities for graduate, undergraduate and high school students will be enabled by this grant. The graduate students will engage in mentoring of undergraduates participating in the project, and of high-school students hosted in the PI lab through the Nanoexplorers program at UTD. By doing meaningful research related to this project, the high school students will be inspired to pursue careers in STEM.

Technical Abstract

Electromigration is a diffusion process where electrons travelling in a conductor in a high-current-density scenario- promote the diffusion of atoms in the metallic lattice, leading to voids and eventually failure. Diffusion depends on the microstructure; in fact, grain boundaries are known to facilitate electromigration due to their loosely-packed structure. Twin boundaries, on the other hand, promise to slow diffusion by several orders of magnitude due to their ordered atomic structure. The proposed research aims to investigate the potentially-beneficial role of materials with well-defined and repeatable twin boundaries, as interconnects with increased resistance to electromigration. The proposed research program is experimental in nature, and aims to gain insights into the electromigration behavior of twinned interconnects by conducting tests where high current densities and controlled temperatures will cause failure. A combination of high-throughput ex-situ electrical tests for statistically-significant quantification of failure, and in-situ transmission electron microscopy (TEM) tests to understand the evolution of the twinned microstructure during electromigration, will be conducted. The objectives of the research are: i) To quantify the electromigration parameters in twinned interconnects; ii) To characterize in-situ TEM the electromigration behavior to obtain structure-property relations; and iii) to compare the electromigration performance of twinned interconnects with respect to published data from interconnects currently used in the electronic industry.

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.

National Science Foundation (NSF)
Division of Materials Research (DMR)
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Judith Yang
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University of Texas at Dallas
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