Wafer-Level Cu/Sn to Cu/Sn SLID-Bonded Interconnects With Increased Strength

• Published in: IEEE transactions on components, packaging, and manufacturing technology (2011) packaging, and manufacturing technology (2011), 2011-09, Vol.1 (9), p.1350-1358
• Main Authors: He Liu, Salomonsen, G., Kaiying Wang, Aasmundtveit, K. E., Hoivik, N.
• Format: Article
• Language: English
• Subjects: Applied sciences; Bonding; Copper; Current density; Design. Technologies. Operation analysis. Testing; Electrochemical process; Electronics; Exact sciences and technology; Gold; Integrated circuits; interconnections; Microelectronic fabrication (materials and surfaces technology); Resistance; resistance measurement; Semiconductor electronics. Microelectronics. Optoelectronics. Solid state devices; Tin; wafer bonding
• ISSN: 2156-3950; 2156-3985
• DOI: 10.1109/TCPMT.2011.2156793

Wafer level Cu-Sn solid liquid interdiffusion (SLID) bonding of interconnects was achieved by bonding two-layered Cu/Sn structures to each other. The bonded interconnects were investigated by mechanical, electrical and microscopic techniques. The Cu-Sn SLID interconnects were created by wafer-level bonding at 260°C. The bonded interconnects show shear strength of 45 MPa and a resistance of the order 100 mΩ . A major advantage of the Cu/Sn to Cu/Sn bonding scenario is to avoid the dynamic wetting of molten Sn to Cu, and simply replace with a liquid to liquid integration. Furthermore, the Sn overflow problem in a Cu/Sn SLID system was successfully addressed by designing a margin of 15 μm at the Cu pads to tolerate any Sn spreading. The uniformity requirement for electroplated Cu-Sn layers, which is crucial for achieving successful wafer-level bonding, is discussed. This wafer-level Cu-Sn SLID bonding process is a promising technique for 3-D assembly and packaging.