Room-temperature wafer bonding of Si to LiNbO₃, LiTaO₃ and Gd₃Ga₅O₁₂ by Ar-beam surface activation

A room-temperature wafer bonding method using surface activation by Ar-beam sputter etching were applied to the bonding between dissimilar materials. LiNbO₃, LiTaO₃ and Gd₃Ga₅O₁₂ wafers were successfully bonded to Si wafers without any heat treatment. This method is free from the various problems caused by the large thermal expansion mismatch between these materials during heat treatment in the conventional wafer bonding processes. The bond prepared by the Ar-beam treatment is so strong that fracture from inside the bulk materials is observed after the tensile test. The results of the bonding of Si wafers to both 128° Y-cut and Z-cut LiNbO₃ wafers indicate that the influence of the crystal orientation on the bonding strength is negligible in this method. This method provides a very low damage bonding process for various material combinations regardless of any thermal expansion mismatch or crystal lattice mismatch.