Mechanisms of copper direct bonding observed by in-situ and quantitative transmission electron microscopy

Abstract In order to understand the mechanisms involved in Cu–Cu interface reconstruction, the microstructure of copper bonding at room temperature and after annealing at 100, 200, 300 and 400 °C was examined by classical and in-situ transmission electron microscopy. We show that the reconstruction of a strongly bonded Cu–Cu interface starts with the formation of thermal diffusion wedges along grain boundaries. These observations were completed by an automatic crystalline orientation mapping system that allows us to quantify the extension of these wedges into the opposite interface and to follow the resulting changes in texture.