Reservoir effect on electromigration mechanisms in dual-damascene Cu interconnect structures

Reservoir effect in dual-damascene Cu interconnect structures caused by electromigration was studied by in situ secondary electron microscopy (SEM). Electromigration-induced void nucleation and apparent void movement in opposite direction to electron flow along the Cu/SiNx interface was found to be responsible for the observed reservoir effect. The observed void evolutions seem to be contrary to current understanding of reservoir effect based on maximum tensile stress developed at the cathode via and on current gradient induced vacancy flux. The influence of the observed reservoir effect on electromigration mechanisms is discussed in detail.