Electromigration-induced stress distributions in 200 &mgr;m long, 10 &mgr;m wide aluminum conductor lines in 1.5 &mgr;mSiO2passivation layers have been investigated in real time using synchrotron-based white-beam x-ray microdiffraction. The results show that a steady-state linear stress gradient along the length of the line developed within the first few hours of electromigration and that the stress gradient could be manipulated by controlling the magnitude and the direction of the current flow. From the current density dependence of the steady-state stress gradient, the effective valenceZ*was determined to be 1.6 at 260 °C. From the time dependence of the transient-state stress gradient, the effective grain boundary diffusion coefficientDeffwas estimated to be8.2×10−11 cm2/sat 260 °C using Korhonen’s stress evolution model [M. A. Korhonen, P. Bo&slash;rgesen, K. N. Tu, and C.-Y. Li, J. Appl. Phys.73, 3790 (1993)]. BothZ*andDeffvalues are in good agreement with the previously reported values. ©1998 American Institute of Physics.