Short-timescale thermal mapping of interconnects

The failure of metal interconnects subjected to brief electrical-current pulses is a reliability concern for the integrated circuits industry, especially in connection with electrostatic discharge (ESD). Since the magnitude and spatial distribution of the temperature rise during pulsing events strongly influence these failures, the development of suitable thermometry techniques is needed to understand the failure. This work develops a scanning laser-reflectance thermometry technique with a novel calibration procedure for interconnects, which captures transient temperature distributions along interconnects subjected to sub-microsecond current pulses of density exceeding 10⁷ A cm^-2. The temperature distribution, which is affected by corners in the interconnects and by the pulse duration, is qualitatively shown to influence the onset location for failure. The failures of the unpassivated interconnects studied here are observed to occur in three stages, which involve the debonding of the interconnect structures from polymer passivation layers and the melting of aluminum