Percolative approach for failure time prediction of thin film interconnects under high current stress

The present study deals with the use of a rapid and non-destructive technique based on percolation theory to predict failure times during the reliability analysis of thin film interconnects under high current stress. Al-Cu test structures were used for this purpose. Small populations of these structures of similar geometry were subjected to extremely high current density conditions (30.6 and 46.6 MA/cm2) and their corresponding failure times were noted. The critical exponent (μB) for the Al-Cu structures stressed at both the current densities was calculated to be 0.16. The value of the μB showed that the structures undergo biased percolation and have similar failure mechanisms (due to Joule heating) at both current densities. The calculated value of μB was used to predict the failure times of the fuses under each of the current stresses. The discrepancy between the experimental failure time and the predicted failure time was significantly low (<12%) in both cases thus expressing the strength of this prediction technique.