Effect of Evaporated and Sputtered Au Nanolayers on Cu Surface for Low-Temperature Cu-to-Cu Bonding

In line with the rapid development of IT technology over time, semiconductor devices require faster speed and high performance while reducing the size of transistors. Accordingly, 3D packaging research is being actively conducted, and Cu-dielectric hybrid bonding is key technology. In this study, we aimed for low-temperature Cu bonding using Au passivation. Au was deposited on Cu at the nano-level thickness with an e-beam evaporator and sputter, respectively. Diffusion activation energy was calculated to compare the diffusion between Au and Cu, and for Au deposited with an evaporator was 6369.52 J/mol when Au diffused to Cu. For Au deposited with sputter, it was 7373.69 J/mol when Au diffused to Cu. Wafer bonding was carried out and bonding interface was analyzed and compared with SAT, SEM, and TEM. Finally, the average shear strength value of the bonding wafer using Au deposited bye-beam evaporator was 5.39 MPa.