INTERACTION OF A VOID AND A GRAIN-BOUNDARY UNDER A HIGH ELECTRIC-CURRENT STRESS EMPLOYING 3-DIMENSIONAL MOLECULAR-DYNAMICS SIMULATION

Molecular dynamics simulation of the behavior of a void in an Al inter connect with a bamboo grain boundary under a high DC current stress ha s been accomplished. It is shown that when the current density is high er than some threshold value, a void can move across the grain boundar y transversely without being trapped in it, and a disordered region is formed between a void and a grain boundary after the transverse proce ss. Annihilation and reformation of the void is also simulated when th e void comes close to the grain boundary, which was experimentally obs erved before. It should be noted that a backflow of a void is simulate d after the current is turned-off at this situation Analysis using loc al stress distribution reveals that a large compressive stress is buil t up near the grain boundary, and an enormous stress gradient is forme d between the grain boundary and the void, and it is strongly suggeste d that this stress gradient is the driving force of the backflow of th e void. The present computational work strongly suggests an existence of the backflow of a void, which has not yet been observed experimenta lly.