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

In this study, room-temperature wafer bonding of AlO 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 AlO 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/m. These results indicate that strong bonds can be formed, which may be sufficient for device applications. In addition, the applicability of different AlO microstructures in the SAB method was investigated, and the effectiveness of applying ALD AlO was experimentally verified. This successful SAB of AlO thin films, which is a promising insulator material, opens the possibility of future room-temperature heterogenous integration and wafer-level packaging.