Atomistic simulation of void nucleation in aluminium lines

Abstract

The formation of voids in aluminium interconnects in integrated circuits was studied atomistically with emphasis on nucleation. Input computational cells included different levels of concentrations of vacancies and stresses together with the typically observed structural defects (grain boundaries and dislocations) in metal lines. The input cells were relaxed using Monte Carlo (atom transpose) and static energy minimization (strain relaxation) techniques concurrently. Besides agglomeration of vacancies in unstrained crystals, the formation of vacancies in crystals under tension was found to be a main contributor to void nucleation. Climb and glide of dislocations were observed atomistically during the formation of voids. Compressive stresses in the metal lines, on the other hand, prevented the formation of voids.