Study of high defect density copper-to-copper direct bonding by electrodeposition

Abstract

Electrodeposited copper films produced by conditions of high current density undergo grain growth at room temperature which is called self-annealing. Self-annealing causes simultaneous changes in electrical properties, mechanical properties, internal stress state and impurity distribution. This change of properties during self-annealing have known to be affected by various sources of the driving forces such as grain boundary energy, surface (interface) energy related to thickness, dislocation and stacking fault density. In this study, electroplated Cu films at additive-free and high current density conditions were prepared to investigate nanoscale defect evolution with respect to the transition of electrical and mechanical properties during self-annealing. The microstructural analysis indicates that the reduction in grain boundary energy by eliminating grain boundaries during the grain growth could be the main driving force of the self-annealing.