Current density and thickness dependent anisotropic thermal conductivity of electroplated copper thin films

Abstract

Electroplated copper thin films are essential in microelectronics, widely used for back-end interconnects, through-silicon vias, and redistribution layers. Currently, their thermal conductivity is frequently estimated indirectly using the four-point probe method and the Wiedemann-Franz law, with limited research on their anisotropy and influencing factors. In this paper, we report the measurements on the electrical and thermal properties of electroplated copper thin films under different current densities during plating and thicknesses using the four-point probe method and frequency-domain thermoreflectance. The results indicate that current density and film thickness significantly influence the microstructure of the copper thin films, resulting in pronounced anisotropy in thermal conductivity. Scanning electron microscopy and electron backscatter diffraction analyses further reveal the microstructural features responsible for this anisotropy and explain how current density affects the internal structure of electroplated copper films, impacting their thermal conductivity. These insights provide valuable theoretical guidance for designing and optimizing electroplated copper films in electronic applications.