Investigation of the interface between LiNbO₃ and Si fabricated via room-temperature bonding method using activated Si nano layer

Abstract

Wafer-level bonding of LiNbO3 and Si has been difficult to achieve owing to the large mismatch in their thermal expansion coefficients, which prevents the use of bonding methods involving annealing. As a solution, we have developed a room-temperature wafer-bonding method that uses an activated Si nanolayer as an adhesive. In this study, we analyzed the bond interface between LiNbO3 and Si that formed via this room-temperature bonding method. The atomic structures of the bonding interface of LiNbO3/Si and the debonded surfaces were investigated in detail. Furthermore, it was found that the bond strength between the activated Si nanolayers and Si was as strong as that of Si/Si bonded using the standard surface-activated bonding method. These findings provide evidence for a strong bond between LiNbO3 and Si at room temperature.