Reliability analysis for encapsulated interconnect lines under dc and pulsed dc current using a continuum electromigration transport model

The origins of two types of electromigration failure models are explored starting with the basic transport differential equations including the effects of electromigration-induced mechanical stress. We compare the results of a nucleation model, in which failure is determined by the time required to build up a critical stress or a critical vacancy concentration at a site of atomic flux divergence, with a void-growth model, in which failure is linked to the growth of a void to a critical size. Two particular applications of the model are investigated, and the results are shown to be in good agreement with available experimental data. In one example, the effect of the presence of a field-free reservoir region extending beyond the current-carrying region of the line is compared to the case without such a field-free extension. In the other, the effects under pulsed de current stress are examined in comparison to de current. Possible applications of this model to design verification are also discussed. (C) 1997 American Institute of Physics.