Effects of Surface Contaminants on Bonding Strength for Direct Cu-Cu Bonding With Passivation Layer

Cu bonding with an addition of an interfacial layer has been gaining attention for providing low-temperature bonding solutions for direct Cu bonding in advanced packaging. In this paper, Cu surfaces with an Au passivation layer were exposed to various dry surface treatments and analyzed by XPS to understand the effects of carbon contaminants on bonding strength. We have shown that VUV N2 treated samples improved the bonding strength and yield significantly compared to the bare samples as various carboxyl and carbonyl groups were removed from the bonding interface.