Effect of electromigration on intermetallic compound formation in Cu/Sn/Cu interconnect

The effect of electromigration on the solid state interfacial reaction of pure Sn and Cu was investigated. Two electron current densities (1.0times10⁴A/cm² and 5.0times10³A/cm²) were applied to line-type Cu/Sn/Cu interconnect at 150degC. The same types of intermetallic compound (IMC), Cu₆Sn₅ and Cu₃Sn, formed at the Sn/Cu interfaces independent of electric current. A high current density caused a polarity effect where the IMC layer at the anode grew significantly thicker than that at the cathode. The growth of IMC was enhanced by electric current at the anode, comparing with that of the samples without applying current. The growth of IMC at the anode followed a parabolic growth rule. After current stressing for 100 hours with a current density of 1.0times10⁴A/cm², microcrack formed at the interface between IMC and solder at the cathode side, while there was no crack formed even after stressing for 200 h with a current density of 5.0times10³A/cm².