Room-temperature Au-Au bonding in atmospheric air using direct transferred atomically smooth Au film on electroplated patterns

We demonstrate the direct transfer of a Au thin film from the atomically smooth surface of a master wafer onto a sealing ring surface. In this process, sealing ring patterns were formed on a cap wafer. These patterns were bonded to a Au thin film on the master wafer by thermo-compression bonding at 200 degrees C. Because the adhesion between the master wafer and Au thin film was controlled to be weak, the atomically smooth Au thin film on the master wafer could be directly transferred onto the top of the existing sealing ring pattern wafer by separating the bonded cap wafer and the master wafer. These transferred Au patterns were bonded to another Au-coated Si wafer with an appropriate adhesion layer at room temperature in atmospheric air. As a result, a high bonding strength of approximately 225 MPa was obtained, a value that is almost the same as that of thermo-compression bonding at 200 degrees C. (C) 2017 Elsevier B.V. All rights reserved.