Room-temperature bonding of Al₂O₃ thin films deposited using atomic layer deposition

In this study, room-temperature wafer bonding of Al₂O₃ thin films on Si thermal oxide wafers, which were deposited using atomic layer deposition (ALD), was realized using the surface-activated bonding (SAB) method. Transmission electron microscopy (TEM) observations indicated that these room-temperature-bonded Al₂O₃ thin films appeared to work well as nanoadhesives that formed strong bond between thermally oxidized Si films. The perfect dicing of the bonded wafer into dimensions of 0.5 mm × 0.5 mm was successful, and the surface energy, which is indicative of the bond strength, was estimated to be approximately 1.5 J/m². These results indicate that strong bonds can be formed, which may be sufficient for device applications. In addition, the applicability of different Al₂O₃ microstructures in the SAB method was investigated, and the effectiveness of applying ALD Al₂O₃ was experimentally verified. This successful SAB of Al₂O₃ thin films, which is a promising insulator material, opens the possibility of future room-temperature heterogenous integration and wafer-level packaging.