Evaluation of temperature rise due to joule heating and preliminary investigation of its effect on electromigration reliability

A demand to increase current density of ULSI interconnections with shrinkage of feature sizes inevitably brings about temperature rise due to Joule heating. We studied how temperature distribution changes with an increase in the current density and further investigated its effect on electromigration-induced failures. We evaluated a temperature rise in a single level Al-alloy interconnection by the use of IR-CCD camera and 3-D fluid dynamical finite element analysis. A build-up of a significant temperature gradient was observed with an increase in the current density. Failure analysis of electromigration accelerating tests revealed that the degradation of MTF at high current density conditions was due to occurrence of a new failure mode of “evaporation mode.” The evaporation mode is most likely caused by an annihilation of a void. Further discussions concerning the relationship between the evaporation mode and the Joule heating effect are given.