Microcosmic mechanisms of Cu to Cu bonding by molecular dynamic simulation

Cu to Cu bonding technology of IC package has the potential to replace solder joint in Future trends. The Cu to Cu bonding technology compared with other joint methods for IC package, it can solve the reliability problems such as electromigration, brittle intermetallic compound or other issues. At present, Cu to Cu bonding methods have been wide developed, but the microcosmic mechanisms of Cu to Cu bonding is unknown, so using the molecular dynamics simulation method to observe microcosmic mechanisms of Cu to Cu bonding. In this paper, the bonding behavior simulation of Cu to Cu by molecular dynamics. Build up the polycrystalline model of copper to simulate bonding process, and bonding condition is different bonding temperature and Cu surface roughness. The bonding location can clearly obtained the grain growth behavior and microcosmic mechanisms in this simulation process. The simulation results can observe bonding behavior include interface formation, grain grow and interconnect in bonding process, and diffusion mode is vacancy mechanism. In the temperature effect, the grain percentage of bonding location have obviously increase about 4.4% under high temperature than other temperature. In the roughness effect, the grain percentage of bonding location have increase about 2.3% under high roughness than low roughness. The principal conclusions can obtained that the appropriate roughness and high temperature can promote interconnect of Cu to Cu bonding.