Sub 100 nm Grain Size Electroplated Copper for Low Temperature Bonding Applications

In this study, we successfully electroplated nanocrystalline copper (NC-Cu) films with grain sizes below 100 nm, demonstrating excellent thermal stability after annealing at 200°C for 1 h. Further post-annealing at 280°C resulted in a slight increase in grain size to 113.5 nm, indicating good stability. Additionally, shear tests were conducted on NC-Cu joints, revealing a shear strength exceeding 30 MPa, with failure occurring in the silicon die. This confirms that the bonding strength surpassed that of the silicon itself. These results highlight the potential of the electroplated NC-Cu films for low-temperature 3D IC advanced packaging applications.