Low-temperature Cu-Cu bonding enabled by a simulated interface approach: process optimization and interfacial mechanisms of Ar plasma activation and glycine wet treatment

The oxidation of the Cu surface remains the most significant challenge of low-temperature Cu-Cu bonding technology. Schemes to achieve and maintain a high-quality Cu surface prior to bonding are therefore urgently needed. Co layer was used as a passivation layer and a simple wet treatment method using glycine was then proposed to remove surface oxides from Co metal. In this work, a novel simulated bonding methodology is proposed, which utilizes a two-step PVD Cu/Co on the PVD Co/Cu surface with a vacuum break, followed by annealing to simulate and investigate bonding mechanisms. The reliability of this methodology was first rigorously validated using Ar plasma activation as a benchmark, yielding simulated specific contact resistance results that closely align with actual bonding data. The simulation bonding methodology was employed to systematically optimize the process, after which the bonding mechanism was investigated. Consequently, chip-level bonding was successfully achieved at 230 °C, exhibiting an ultra-low specific contact resistance of 2.9 × 10 −8  Ω·cm 2 with a bonding area exceeding 99%. HRTEM and EDS analyses confirm that glycine treatment promotes direct Co-to-Co contact and uniform atomic interdiffusion. This methodology provides an efficient platform for investigating interfacial treatment processes and accelerating the development of advanced 3D integration technology.