Polarity effect of electromigration in Ni2Si contacts on Si.

Abstract

The electromigration of contacts in shallow junction devices is a reliability issue for the future very large scale integration technology. The stability of silicide contacts against a high current density is unknown. We have observed a strong polarity effect of the electromigration-induced failure at both $\mathrm{Ni}/{\mathrm{Ni}}_{2}\mathrm{Si}{/n}^{+}\ensuremath{-}\mathrm{Si}$ and $\mathrm{Ni}/{\mathrm{Ni}}_{2}\mathrm{Si}{/p}^{+}\ensuremath{-}\mathrm{Si}$ contact pairs. They were found to fail preferentially at the cathode. The unreacted $\mathrm{Ni}{/n}^{+}\ensuremath{-}\mathrm{Si}$ and $\mathrm{Ni}{/p}^{+}\ensuremath{-}\mathrm{Si}$ contact pairs have also been studied. The latter fails at the cathode while the former fails at the anode. Failure mechanisms are proposed to explain the polarity effects.