Affiliation:
1. Department of Materials Science and Engineering, National Yang Ming Chiao Tung University, Hsinchu 30010, Taiwan
Abstract
Cu–Cu joints have been adopted for ultra-high-density packaging for high-end devices. However, the atomic diffusion rate is notably low at the preferred processing temperature, resulting in clear and distinct weak bonding interfaces, which, in turn, lead to reliability issues. In this study, a new method for eliminating the bonding interfaces using two types of Cu films in Cu–Cu bonding is proposed. The difference in grain size was utilized as the primary driving force for the migration of bonding interfaces/interfacial grain boundaries. Additionally, the columnar nanotwinned Cu structure acted as a secondary driving force, making the migration more significant. When bonded at 300 °C, the grains from one side grew and extended to the bottom, eliminating the bonding interfaces. A mechanism for the evolution of the Cu bonding interfaces/interfacial grain boundaries is proposed.
Funder
National Science and Technology Council, Taiwan
Ministry of Education (MOE) in Taiwan
Semiconductor Research Institute
Nanoscience Technology Center
National Chiao Tung University