NUMERICAL-SOLUTION OF THE ELECTROMIGRATION BOUNDARY-VALUE PROBLEM UNDER PULSED DC CONDITIONS

The one-dimensional electromigration boundary value problem under puls ed de conditions is numerically investigated by utilizing the transmis sion-line matrix modeling method. A perfectly blocking boundary, where void formation and failure occur, is assumed at one end of an interco nnection line. At the other end, two physically plausible boundary con ditions are considered. From the design-rule point of view, an approac h is proposed to convert conveniently the pulsed stress into an equiva lent de stress that would produce electromigration damage at a similar rate. Based on the fundamental diffusion-drift model, we show that th e vacancy buildup behavior under a pulsed dc stress gamma(p) can be de scribed accurately by the dc stress gamma(dc) scaled according to the duty factor r of the current pulse, namely, gamma(dc) = rT gamma(p). T his study also represents a theoretical confirmation for the (jr)(-2) dependence of the pulsed electromigration failure (where j is the curr ent density), which has been observed in a number of experimental stud ies. (C) 1996 American Institute of Physics.