Electromigration-Induced Interfacial Reactions in Cu/Sn/Electroless Ni-P Solder Interconnects

• Published in: Journal of electronic materials 2012-04, Vol.41 (4), p.730-740
• Main Authors: Huang, M. L., Zhou, S. M., Chen, L. D.
• Format: Article
• Language: English
• Subjects: Anodes; Applied sciences; Brazing. Soldering; Characterization and Evaluation of Materials; Chemical reactions; Chemistry and Materials Science; Condensed matter: structure, mechanical and thermal properties; Copper; Diffusion; Diffusion in solids; Dissolution; Electromigration; Electronics; Electronics and Microelectronics; Exact sciences and technology; Instrumentation; Interconnect; Interface reactions; Interfacial bonding; Joining, thermal cutting: metallurgical aspects; Materials; Materials Science; Metals. Metallurgy; Nickel; Optical and Electronic Materials; Physics; Soldering; Solders; Solid State Physics; Tin; Transport properties of condensed matter (nonelectronic)
• ISSN: 0361-5235; 1543-186X
• DOI: 10.1007/s11664-012-1952-6

The effect of electromigration (EM) on the interfacial reaction in a line-type Cu/Sn/Ni-P/Al/Ni-P/Sn/Cu interconnect was investigated at 150°C under 5.0 × 10 3  A/cm 2 . When Cu atoms were under downwind diffusion, EM enhanced the cross-solder diffusion of Cu atoms to the opposite Ni-P/Sn (anode) interface compared with the aging case, resulting in the transformation of interfacial intermetallic compound (IMC) from Ni 3 Sn 4 into (Cu,Ni) 6 Sn 5 . However, at the Sn/Cu (cathode) interface, the interfacial IMCs remained as Cu 6 Sn 5 (containing less than 0.2 wt.% Ni) and Cu 3 Sn. When Ni atoms were under downwind diffusion, only a very small quantity of Ni atoms diffused to the opposite Cu/Sn (anode) interface and the interfacial IMCs remained as Cu 6 Sn 5 (containing less than 0.6 wt.% Ni) and Cu 3 Sn. EM significantly accelerated the dissolution of Ni atoms from the Ni-P and the interfacial Ni 3 Sn 4 compared with the aging case, resulting in fast growth of Ni 3 P and Ni 2 SnP, disappearance of interfacial Ni 3 Sn 4 , and congregation of large (Ni,Cu) 3 Sn 4 particles in the Sn solder matrix. The growth kinetics of Ni 3 P and Ni 2 SnP were significantly accelerated after the interfacial Ni 3 Sn 4 IMC completely dissolved into the solder, but still followed the t 1/2 law.