Hydrophilic Bonding of SiO2/SiO2 and Cu/Cu using Sequential Plasma Activation

Hybrid bonding is an indispensable technique for the 3D integration of electronic systems. Cu-to-Cu interconnections and SiO 2 -to-SiO 2 dielectric layers should be bonded simultaneously in the wafer-to-wafer bonding process. In this study, sequential plasma activation (SPA) including O 2 plasma, N 2 plasma, and N radical is investigated for low-temperature bonding of Cu and TEOS SiO 2 at 200°C. The SPA bonding improves the bond strength to more than 1 J/m 2 compared to the conventional single gas plasma activation bonding. The surface analysis indicates that SPA forms oxynitrides on TEOS SiO 2 surface and Cu oxide with adsorbed water on the Cu surface, facilitating the bonding interface formation. The presented technique will contribute to the hybrid bonding applications at lower temperatures.