Surface diffusion induced shape evolution of multiple circular voids under high current density

To understand better the failure mechanism of interconnects under high current density, surface diffusion induced multi-voids shape evolution is investigated. The electric current field is solved analytically for a plate containing two circular voids. Based on the mass diffusion theory, the electromigration induced multi-voids shape evolution is predicted. For the isolated void case, the shape is generally preserved and moves steadily in the conductor. For the multi-voids case, a theoretical model is developed to describe the general behavior of voids shape evolution. It is noted that the steady shape of the initial circular void is broken, and bifurcation could occur due to asymmetry of the current distribution around the voids surface. By considering the multi-voids interaction effect, how the void collapses to a crack, coalesces with each other, or splits into smaller voids is clarified.