Thanks to the supports on critical processes from Dr. Hsiang-Hung Chang & Dr. Wei-Lan Chiu’s team, we have made a breakthrough on Cu-Cu/SiO2 hybrid bonding. The bonding temperature is 200C and the pressure is only 1 MPa. The diameter of the Cu joints is 8 um, and the measured specific contact resistance is as low as 1.2 E-9, which is the lowest value reported in literature for the Cu-Cu/SiO2 hybrid joints bonded below 300C

We adopted (111)-oriented Cu with high surface diffusivity to achieve low-temperature and low-pressure Cu/SiO₂ hybrid bonding. Electroplating was employed to fabricate arrays of Cu vias with 78% (111) surface grains. The bonding temperature can be lowered to 200 °C, and the pressure is as low as 1.06 MPa. The bonding process can be accomplished by a 12-inch wafer-to-wafer scheme. The measured specific contact resistance is 1.2 E-9 Ω·cm², which is the lowest value reported in related literature for Cu-Cu joints bonded below 300 °C. The joints possess excellent thermal stability up to 375 °C. The bonding mechanism is also presented to provide more understanding on hybrid bonding.