Fully CMOS-Compatible Wafer Bonding Based on Press Marking Using Thick Electroplated Aluminum

Aluminum has a great potential as a wafer bonding material due to its inherent compatibility with the complimentary metal oxide semiconductor (CMOS) processes. In this study, a novel wafer bonding technique for heterogeneous integration using electroplated Al bonding frame is demonstrated for the first time. The Al frames were deposited by electroplating from a chloroaluminate ionic liquid. The electroplated Al bonding frames were mechanically deformed by the groove structures on the counter wafer, i.e. press marking. Such a large mechanical deformation enabled the wafer bonding at a temperature of as low as 250°C, which is the lowest value that has ever been reported for the Al bonding. The influence of the bonding temperature to the quality of the bonded substrates were evaluated. The bonding shear strength of 8–100 MPa was obtained, which is in par with the other established techniques.