Characterization of contact and via failure under short duration high pulsed current stress

Contact and via failure under short-duration, high current pulses has been characterized for the first time. It is shown that the critical current is strongly dependent on the pulse width, and contact/via cross section area. It is also found that for contact structures the critical current depends on the thermal conductivity of the underlying diffusion region and is independent of the electrical properties such as sheet resistance. Further, it is shown that single Al contacts can sink similar currents as compared to W contacts, and multiple W/Al contact structures will fail under smaller current density as a result of lower heat dissipation capacity. The effect gets stronger with thicker contact liner metal. Critical current density is also found to be decreasing with increasing number of vias due to lower heat dissipating capacity of multiple vias. Furthermore, the contact/via failure thresholds were found to be independent of the direction of electron flow. Contact breakdown mechanism has been shown to be related to the TiN/TiSi2 interface reaction which causes a sudden increase in contact resistance. The via failure mechanism has been shown to be due to thermal runaway resulting in a complete destruction of the structures.