Utilization of Au Passivation Nanolayer for Low-Temperature Cu-to-Cu Bonding

The performance and functionality of semiconductor devices have so far continued to require higher levels as IT technologies progressively develop. Accordingly, the importance of back-end process of semiconductor process is increasing, and in particular, packaging technologies are being studies in various ways. Cu(copper)/dielectric hybrid bonding is one of the important technologies for heterogeneous integration in 3D packaging, and many studies for low-temperatures hybrid bonding have been conducted. In this study, low-temperature Cu bonding using Au(gold) passivation nanolayer was analyzed. The diffusion rate between Cu and Au deposited by an e-beam evaporator and sputter showed the opposite trends. W2W(wafer-to-wafer) and C2C(chip-to-chip) bonding and annealing were carried out at 180°C and 200 °C, respectively. A comparison of the bonding interface results was made based on the deposition methods of Au, as well as the differences in Au thickness. Bonding interface was analyzed using transmission electron microscopy (TEM). Shear strength and resistance measurements were carried out to evaluate the bonding strength and electrical characteristics.