200-nm-thick Au interconnects on a quartz substrate were tested in-situ inside a dual-beam microscope by applying direct current,alternating current and alternating current with a small direct current component.The failure behavior of the Au interconnects under three kinds of electric currents were characterized in-situ by scanning electron microscopy.It is found that the formation of voids and subsequent growth perpendicular to the interconnect direction is the fatal failure mode for all the Au interconnects under three kinds of electric currents.The failure mechanism of the ultrathin metal lines induced by the electric currents was analyzed.