Intermetallic Compound Formation Mechanisms for Cu-Sn Solid–Liquid Interdiffusion Bonding

• Published in: Journal of electronic materials 2012-09, Vol.41 (9), p.2453-2462
• Main Authors: Liu, H., Wang, K., Aasmundtveit, K.E., Hoivik, N.
• Format: Article
• Language: English
• Subjects: 3-D technology; Applied sciences; Bonding; Characterization and Evaluation of Materials; Chemistry and Materials Science; Copper; Electronics; Electronics and Microelectronics; Exact sciences and technology; Instrumentation; Interdiffusion; Intermetallic compounds; Intermetallics; Joining, thermal cutting: metallurgical aspects; Materials; Materials Science; Metals; Metals. Metallurgy; Microelectromechanical systems; Microelectronic fabrication (materials and surfaces technology); Optical and Electronic Materials; Packaging; Ramps; Semiconductor electronics. Microelectronics. Optoelectronics. Solid state devices; Solid State Physics; Three dimensional
• ISSN: 0361-5235; 1543-186X
• DOI: 10.1007/s11664-012-2060-3

Cu-Sn solid–liquid interdiffusion (SLID) bonding is an evolving technique for wafer-level packaging which features robust, fine pitch and high temperature tolerance. The mechanisms of Cu-Sn SLID bonding for wafer-level bonding and three-dimensional (3-D) packaging applications have been studied by analyzing the microstructure evolution of Cu-Sn intermetallic compounds (IMCs) at elevated temperature up to 400°C. The bonding time required to achieve a single IMC phase (Cu 3 Sn) in the final interconnects was estimated according to the parabolic growth law with consideration of defect-induced deviation. The effect of predominantly Cu metal grain size on the Cu-Sn interdiffusion rate is discussed. The temperature versus time profile (ramp rate) is critical to control the morphology of scallops in the IMC. A low temperature ramp rate before reaching the bonding temperature is believed to be favorable in a SLID wafer-level bonding process.