2019 6th International Workshop on Low Temperature Bonding for 3D Integration (LTB-3D) | 2019
Effect of Nitride Passivation on Cu Surface for Low Temperature Cu-to-Cu Bonding
Abstract
For low temperature Cu-to-Cu bonding process, copper nitride passivation on Cu surface was studied via two-step plasma treatments using argon and nitrogen gases. The two-step plasma treatment of copper nitride passivation was processed in a DC sputtering vacuum chamber. Cu surface was activated with Ar ion bombardment in Ar plasma and immediately followed by N2 plasma treatment for surface passivation. In this study, various parameters of Ar plasma such as RF power, working pressure and treatment time were controlled to find an optimal Cu surface where nitride passivation was formed. The degree of nitridation and oxidation after the plasma treatments was characterized quantitatively using XPS analysis. Lastly Cu-to-Cu bonding was performed at 300°C and the effect of copper nitride passivation on Cu bonding quality was evaluated by SAT and SEM analysis.