Activation process and bonding mechanism of Si/ LiNbO3 and LiNbO3/LiNbO3 at room temperature

Wafer level bonding feasibility was examined for Si/LiNbO3 and LiNbO3/LiNbO3 wafers by using a modified surface activated bonding (SAB) process at room temperature. A low energy argon ion source of 80 eV energy with 3 A amperage was used, which was capable of sputter cleaning and depositing Fe nanolayers on the surfaces. Visual inspection showed that almost the entire area of 4-inch wafers of Si/LiNbO3 was bonded. The tensile strength distribution was inhomogeneous and it was varied in the range 8-37 MPa. An amorphous layer of 5 nm thick was observed across the interface. Electron energy loss spectrometry (EELS) analysis showed cross-linking behavior of Fe atoms of bonding mates, which was responsible for high bonding strength between Si/LiNbO3 and LiNbO3́/ LiNbO3 at room temperature.