Tuning electromigration-thermomigration coupling in Cu/W Blech structures

Abstract

Here, we study the effect of electromigration-thermomigration coupling on enhanced mass transport and anomalous backward mass transport phenomenon at the cathode and the anode, respectively, in Cu thin films, by varying different experimental parameters, such as current density, interlayer thickness, and temperature. Test samples were fabricated as per the Blech configuration on a SiO2/Si substrate with a W interlayer in between the Cu film and the substrate. To interpret the experimental results, finite element analysis was performed. Increasing current density and temperature as well as decreasing interlayer thickness enhanced the net backward mass transport at the anode, as these factors led to a significant increase in the temperature gradient in the Cu film near the anode, thereby enhancing the electromigration-thermomigration coupling. This study provides a comprehensive understanding of minimizing the coupling of the aforementioned driving forces that cause the anomalous backward mass transport phenomenon at the anode in the interconnects.