Room temperature wafer scale bonding of electroplated Au patterns processed by surface planarization

We demonstrate a newly-developed replication process of a surface shape from an atomically smooth master substrate onto electroplated Au patterns by a lift-off process using a thin sacrificial layer. An atomically smooth Au surface with a root mean square surface roughness of 0.8 nm could be replicated from the master substrate by this process. Then we examined its applicability to room-temperature Au-Au bonding in atmosphere. A high bonding strength of about 250 MPa was obtained. Fracture from the bulk of the Si substrates was observed after tensile tests, which was also the case for the thermocompression bonding at 200 °C.