Low temperature Cu/SiO2 hybrid bonding via < 1 1 1 >-oriented nanotwinned Cu with Ar plasma surface modification

Argon (Ar) plasma surface modification and highly (1 1 1)-oriented nanotwinned copper (nt-Cu) were combined to lower the bonding temperature of Cu/SiO2 hybrid joints. The contact angle of water on SiO2 could be reduced from 22.6 degrees to 3.3 degrees after the plasma treatment. Benefiting from the high surface diffusivity of nt-Cu and great hydrophilicity of the plasma-assisted SiO2, the bonding temperature could be reduced to 150 degrees C. However, such a plasma treatment caused the serious oxidation of the activated Cu in the ambient. To balance the activation and oxidation of the Cu films, Ar plasma power was tuned. X-ray photoelectron spectroscopy (XPS) was used to analyze the SiO2 surfaces. We found an increase (13.6% to 28.3%) in Si-OH and decreases in Si-O and C-O intensities after the plasma activation. Such decreases in Si-O and C-O intensities could be attributed to the removal of organic compounds. Shear tests were also conducted to characterize the bonding strength of the joints. An excellent bonding strength > 35 MPa was achieved after the post annealing and plasma treatment.

Automated summary

Argon (Ar) plasma surface modification and highly (1 1 1)-oriented nanotwinned copper (nt-Cu) were combined to lower the bonding temperature of Cu/SiO2 hybrid joints. The contact angle of water on SiO2 could be reduced from 22.6 degrees to 3.3 degrees after the plasma treatment. X-ray photoelectron spectroscopy (XPS) was used to analyze the SiO2 surfaces and the bonding strength of the joints was characterized through shear tests, achieving an excellent bonding strength > 35 MPa.