Current crowding

Current crowding generates electromigration damage through the effects of Joule heating. This accelerating effect of raised temperature is observed once a void has started to form in the metallization line.

Growth of a void causes a reduction in cross-sectional area giving current crowding, i.e. an increase in current density and, therefore, an increase in local temperature. The temperature increase causes the local rate of atomic migration to increase, increasing flux divergences and accelerating the rate of electromigration damage. Accelerating void growth continues until the void is large enough to cause a significant problem within the IC, through increase of resistance, or ultimately, melting and the formation of an open circuit.