A synchrotron radiation real-time in situ imaging study on the reverse polarity effect in Cu/Sn–9Zn/Cu interconnect during liquid–solid electromigration

Synchrotron radiation real-time in situ imaging technology was used to study the interfacial reaction in Cu/Sn–9Zn/Cu interconnect during liquid–solid electromigration. The reverse polarity effect, evidenced by the IMC layer at the cathode growing continuously while that at the anode was restrained, resulted from the directional migration of Zn atoms toward the cathode under electron current stressing, which is induced by the positive effective charge number of Zn atoms but not by the back-stress. The severe dissolution of Cu anode was explained theoretically.