Direct observation of the growth and movement of electromigration voids under passivation

In situ high voltage scanning electron microscope (HVSEM) examinations of accelerated electromigration tests were performed. The samples tested were Al‐1% Si lines 3 μm wide, 1 μm high, and 300 μm long. Voiding processes were observed through passivation and the early stages of voiding were documented. Voids nucleated at the sidewall of the line at the metal‐passivation interface. The voids then grew in a wedge‐like manner. The later stages of movement and coalescence of voids, leading to eventual failure, were also imaged. A simple model of the early stages of voiding is proposed.