Failure mechanisms of pure silver, pure aluminum and silver–aluminum alloy under high current stress

This study investigates the suitability of pure silver (Ag), pure aluminum (Al) and silver (3 at.%-aluminum) alloy (Ag(Al)) metallizations for potential application in programmable fuse links in field-programmable gate arrays. Single-line test-structures of the metallizations, of varying line widths (2.5–10 μm) on titanium nitride (TiN) and SiO 2 , have been investigated by subjecting them to extremely high current-density conditions. With increase in applied current densities, the lines experienced catastrophic failure. The microstructure and topography of the failed sites was examined using scanning electron microscopy and correlated with failure times. The failure mechanism for all three metallizations was dominated by Joule heating produced by the high currents flowing through the lines. For Ag and Ag(Al) structures on SiO 2 , failure occurs by Joule-heating-induced vaporization of metallization. In the case of Ag and Al metallizations on TiN, failure is due to vaporization of metallization followed by mechanical cracking of the barrier thin film due to thermal stresses that act on the layers.