Increasing the mean grain size in copper films and features

Abstract

This thesis discusses the introduction of super grains in both sputtered and electroplated copper films and the implementation of these grains in copper interconnects, whose dimensions vary from the micrometer regime to the nanometer regime. The final chapter summarizes the major results of this research and provides some perspectives for future work. Nowadays, a clear increase in the resistivity of copper interconnect wires is observed for scaled wire geometries. This increase embodies several scattering mechanisms such as surface and grain boundary scattering which contribute to the classic electron-phonon scattering in bulk materials. Finding ways to increase the mean grain size and thereby decreasing the contribution of grain boundary scattering remains an important research topic. In this work, an extraordinary increased mean grain size was observed in both sputtered and electroplated copper blanket films, depending on the specific choice of layer thickness, deposition conditions and annealing temperature. This knowledge was further used to implement these super grains in copper features, thereby rendering us a solution to reduce the resistivity of copper nanowires and the subsequent interconnect RC delay for future technology nodes. The major results of this work are listed in the following categories.