Cu-to-Cu bonding has drawn a lot of attention as it not only has excellent electrical and thermal properties but also excellent electromigration resistance. It is believed to be a next-generation technology of IC packaging and it will help keep Moore’s law effective. According to previous studies, copper direct bonding using nanotwinned copper can reduce the bonding temperature to 150°C but still requires a vacuum atmosphere. This study employed an E-gun to plate a gold layer on nanotwinned copper thin films in order to prevent oxidation. With the aid of the thin gold layer, we can prevent the oxidation of Cu surfaces and reduce the surface roughness. In this way, we achieved bonding at 200°C in N2 and 250°C in ambient pressure with a low bonding pressure of 0.78 MPa.
- Direct bonding