Effect of Cu Microstructures on Cu/SiO2 Hybrid Bonding for 3D IC Heterogeneous Integration

This paper reviews the effect of Cu microstructures on the Cu/Si02 hybrid bonding for 3D IC heterogeneous integration. Four Cu microstructures are discussed, including regular Cu, (111)-oriented nanotwinned Cu, fine-grained Cu, and nanocrystalline Cu. The Cu microstructures affect the amount of expansion of Cu pads, as well as the surface diffusivity during the bonding process. Therefore, it is critical to select proper Cu microstructures for different applications.