Bismuth segregation enhances intermetallic compound growth in SnBi/Cu microelectronic interconnect

There was a sudden increase of intermetallic compound (IMC) Cu6Sn5 growth rate in the eutectic Sn58wt. %Bi/Cu joint during aging process. With aging time increasing, Bi accumulated at the Cu3Sn/Cu interface and gradually induced the fracture mode of the joint to change from ductile to brittle one along this interface. Bi segregation enhanced IMC Cu6Sn5 growth by means of promoting the interfacial reaction at Cu3Sn/Cu interface, which was concluded from IMCs (Cu6Sn5 and Cu3Sn) growth behavior for pure Sn/Cu and Sn10wt. %Bi/Cu interconnects at the same temperature.

Research highlights▶ There was a sudden increase of intermetallic compound (IMC) growth rate in the eutectic Sn58wt. %Bi/Cu joint during aging process. With aging time increasing, Bi accumulated at the Cu3Sn/Cu interface and gradually induced the fracture mode of the joint to change from ductile to brittle one along this interface. Bi segregation is responsible for the enhanced IMC growth by means of promoting the interfacial reaction at Cu3Sn/Cu interface.