Mass transport phenomena in copper nanowires at high current density

Yu-Ting Huang, Chun-Wei Huang , Jui- Yuan Chen , Yi-Hsin Ting , Shao-Liang Cheng , Chien-Neng Liao , and Wen-Wei Wu, 2016

Image courtesy of Nano Res.

Abstract

Electromigration in Cu has been extensively investigated as the root cause of typical breakdown failure in Cu interconnects. In this study, Cu nanowires connected to Au electrodes are fabricated and observed using in situ transmission electron microscopy to investigate the electro- and thermo-migration processes that are induced by direct current sweeps. We observe the dynamic evolution of different mass transport mechanisms. A current density on the order of 106 A/cm2 and a temperature of approximately 400 °C are sufficient to induce electro- and thermo-migration, respectively. Observations of the migration processes activated by increasing temperatures indicate that the migration direction of Cu atoms is dependent on the net force from the electric field and electron wind. This work is expected to support future design efforts to improve the robustness of Cu interconnects.

Impact Statement

Electro- and thermo-migration processes, induced by direct current sweep, were investigated in Cu nanowires using in situ TEM techniques. High current density of 10^6 A/cm2 and temperatures up to 400 C were applied to the sample to observe and characterize the migration processes.