Synergistic Plasma Activation-Enabled Low-Temperature Cobalt/SiO2 Hybrid Bonding without Oxide Interfaces

Abstract

Metal passivation participating in bonding is a promising method for hybrid bonding to fabricate high-density devices and high-computing instruments, by turning Cu/SiO₂ bonding into passivation/SiO₂ bonding and evading the obstacles of Cu oxidation. However, the performance of the passivated metal bonding interface and the process compatibility for SiO₂–SiO₂ bonding are crucial for higher speed and lower power consumption but neglected. In this article, we introduce cobalt (Co) as a hybrid bonding metal and demonstrate a facile bonding method for combining Co–Co, Co–SiO₂, and SiO₂–SiO₂. This approach enables cobalt-participated hybrid bonding through synergistic NH₃/H₂O → Ar plasma treatment. Cobalt (Co) reduction and SiO₂ hydrophilization are simultaneously realized by a one-step NH₃/H₂O plasma activation from vaporized ammonia liquid for ease of metallization and dehydration bonding to be obtained, respectively. Moreover, by introducing the subsequent Ar plasma treatment, the reoxidation from the oxygen-containing process and overadsorption of H₂O are evaded without hindering the construction of the interface. Additionally, the roughness of surfaces is significantly smoothed without gas-storage microstructure topography. The well-prepared surfaces enable surface reaction and interface construction without void generation thanks to the effective activation and process tune-up. Remarkably, the atomic interconnection is facilitated for both homo- and heterogeneous bonding at temperatures as low as ∼200 °C. With the increase in yield of the bonding area, the three bonded interfaces can obtain about 1.5 times the promotion with a 25% decrease in Co–Co interfacial resistivity. The Co-passivated hybrid bonding with synergistic activation could be used for high-density integration with efficient communication due to their favorable interfacial performance and feasible process^.