Stress relaxation and microstructural change in passivated Al(Cu) lines

Relaxation of stresses in passivated Al lines can lead to void formation. Stress relaxation behavior of passivated Al(1 wt.% Cu) lines with 3, 1, and 0.5 /spl mu/m linewidths has been studied by using a bending beam technique. Our data show that there are two distinct stress relaxation regimes: one due to dislocation glide which occurs during a short period of annealing, and the other due to stress-induced voiding during a long-term annealing. The short-term stress relaxation in Al(Cu) lines depends on both line geometry and temperature, which can be explained as a combined result of the driving force (effective shear stress) and mass transport kinetics (temperature). The long-term stress relaxation behavior can be correlated with stress-induced voiding.