Thin-layer Au-Sn solder bonding process for wafer-level packaging, electrical interconnections and MEMS applications

The developed bonding process utilizes AuSn solder and provides liquid-proof sealing and multiple reliable electrical connections between the bonded wafers. The bond can withstand 300degC and features a thin bond line (2-3 mum), high bond strength, excellent bond gap control, and low stress due to small amount of bonding material. A Nb/Au seed layer was shown to be an optimal adhesion and barrier film.