Thermomechanical finite element modeling of Cu–SiO₂ direct hybrid bonding with a dishing effect on Cu surfaces

Copper direct bonding technology is considered to be one of the most promising approaches for matching the miniaturization needs in future tridimensional integrated high performance circuits (3D-IC). However, the bonding mechanism of copper surfaces with an initial dishing effect, induced by the polishing step, must be investigated in order to optimize the adhesion process and prevent further reliability issues. In this study, we present thermomechanical finite element simulations of Cu–SiO₂ hybrid bonding with account for the annealing step and various amplitudes of the initial dishing. A cohesive model that mimics nonlinear interactions between Cu/Cu and SiO₂/SiO₂ interfaces and related bonding mechanism is implemented within a nonlinear contact mechanics strategy. The bonding process along with the influence of the annealing conditions and the copper plastic response on the closure of the Cu/Cu interface are investigated.