Chao-hong Wang¹, Yu-bin Guo¹; ¹National Chung Cheng University

Co has attracted great attention as a promising diffusion barrier material because it possesses superior electromigration resistance. In the typical electroless Co process, sodium hypophosphite is used as a reducing agent, and thus P is co-deposited in electroless Co(P) layers. During reflow soldering, the CoSn₃ was rapidly formed and the chunky CoSn₃ phase massively spalled into the molten solder. The IMC fast growth and massive spalling resulted in the fast consumption of Co barrier layer, which is severely disadvantageous for the reliability of solder joints. In this study, we developed a new electroless Co(B) process using Dimethylamine borane (DMAB) as the reducing agent. The B contents (0.5at.% ~ 5 at.% B) in the metallization greatly affects the microstructure. A series of interfacial reactions were systematically examined. The results clearly revealed that the Co(B) metallization can effectively suppress the IMC growth and avoid the IMC massive spalling.