Abstract
In this study, we optimized the vacuum condition for direct bonding of CMP-Cu films using the surface activated bonding (SAB) method at room temperature. The quality of bonding with the SAB method depends strongly on the cleanness of the surface activated by the Ar atom beam irradiation. Therefore, the relationship between the vacuum condition and bonded area was evaluated with the amount of exposure (Pa⋅s) as the parameter. Our results show that the critical exposure condition to obtain a full bonded area on the surface is around 0.1 Pa⋅s. The numbers of molecules colliding with the active surface conceivably determined the cleanness of the surface, and XPS observation showed that oxidation of the surface could be prevented at this level of exposure.
