Effects of high current pulses on integrated circuit metallization reliability

Transient heat flow analysis using two-dimensional finite-element method has been used to calculate the temperature rise of aluminum lines on passivated and unpassivated silicon substrates. The results are used to predict the effect of self-heating on the electromigration lifetime of aluminum interconnects under pulse current stressing. A model has been developed to incorporate damage relaxation and self-heating effects on electromigration. It is shown that self-heating is expected to produce less than 20% error in typical accelerated testing conditions provided the peak current density (J_p) is less than 4×10⁶ A/cm². Design rules based on keeping the average current density (J_av) constant are acceptable provided that duty factor is larger than 1% for all frequencies above 1 MHz