Time-dependent changes in morphology and resistance of W/TiN/Ti metal lines upon applying voltage pulses

Transient current profiles, measured while applying voltage pulses to W/TiN/Ti metal lines, showed two different stages. In the first stage, the transient current decreased due to both structural changes associated with Ti/W diffusion and the positive temperature coefficient of resistance of polycrystalline W/TiN/Ti. In the second stage, the transient current remained approximately constant due to the effect of morphological and microstructural changes counter-balanced by the thermal expansion of W near the melting temperature and the latent heat of fusion of W. Asymmetric electromigration and symmetric thermomigration fluxes resulted in the asymmetric metal line failure location near the anode.

► Transient current profiles of W/TiN/Ti metal lines showed two different stages.
► Initially, current decreased due to morphological changes by Ti/W diffusion.
► Later, current remained constant due to thermal expansion and latent heat of fusion.
► Electromigration and thermomigration fluxes resulted in the asymmetric failure.