Multiphysics Analysis of Bonding Interface Contact Resistance Effects on Electromigration Evolution in Cu-Cu Bonding Interconnect for 3-D Heterogeneous Integrated Circuits

The effects of contact resistance induced by bonding interface roughness and bonding pressure on electromigration (EM) evolution in Cu–Cu bonding interconnects are investigated through Multiphysics simulation. The EM is simulated by solving current continuity equation, heat conduction equation, solid mechanics equilibrium equation, and vacancy diffusion equation by the finite element method (FEM), where the void nucleation process induced by vacancy diffusion is simulated based on atomic flux divergence (AFD) calculated from vacancy diffusion equation. The effects of contact resistance on the electro-thermal-mechanical Multiphysics evolution, void nucleation process, and lifetime of bonding interconnects are studied. Simulation results show that contact resistance can change the driving force of vacancy diffusion by changing the electro-thermal-mechanical multifield distribution in interconnect, and further induce the variation of the vacancy concentration distribution, thus leading to the variation of AFD at bonding interface. Moreover, the increased contact resistance drives the void nucleation position from the top corner of the copper pillar to the bonding interface and reduces the lifetime of bonding interconnects, due to the variation of AFD at bonding interface.