Effect of Electromigration on Interfacial Reaction in Cu/Sn-9Zn/Cu and Cu/Sn-9Zn/Ni Interconnects

The interfacial reaction in Cu/Sn-9Zn/Cu and Cu/Sn-9Zn/Ni interconnects during electro migration (EM) were investigated under a current density of 5.0 x 103 A/cm(2) at 150 degrees C. An obvious reverse polarity effect in Cu/Sn-9Zn/Cu and Cu/Sn9Zn/Ni interconnects during EM was demonstrated, i.e., the interfacial IMCs at the cathode grew continuously and were remarkably thicker than those at the anode. The formed IMC was always Cu5Zn8 at the cathode and anode interfaces during EM in Cu/Sn-9Zn/Ni interconnect. And a little Cu6Sn5 phase formed at the cathode interface after EM for 400h. When electrons flowed from the Cu side to the Ni side in Cu/Sn-9Zn/Ni interconnect, the (Ni, Cu)(3)(Sn, Zn)(4) replaced Ni5Zn21 at the Ni/Sn-Zn interface, while the formed IMC was always Cu5Zn8 at Cu/Sn-Zn interface. More Zn atoms diffused toward Sn-9Zn/Cu interface (cathode) in Cu/Sn-9Zn/Ni interconnect during EM and the Cu5Zn8 layer at the cathode in Cu/Sn-9Zn/Cu interconnect is obviously thicker than that in Cu/Sn-9Zn/Ni interconnect during EM for 400h.