Controlling electromigration to selectively form thin metal wires and metal microspheres

Abstract

Guidelines for selecting the shape formed by metal discharged from a narrow Al line were developed. By controlling electromigration in the line, either relatively large microspheres, thin wires, or relatively small microspheres could be formed. Our starting point was a passivated polycrystalline Al line with a slit and small holes at the anode end of it. In the discussion, we describe how the temperature of a part of a wire, T*, at the moment when the part is completely discharged from the hole, affects the shape of the microstructural feature formed from the metal. High, intermediate, and low values of T* were found to correspond to the formation of large microspheres, thin wires, and small microspheres, respectively. The experimental results are explained in the discussion.