Electromigration in isolated aluminum vias probed by resistance changes and 1/f noise

1/f noise and high-resolution resistance measurements have been performed in isolated aluminum via interconnects under electromigration stress. The test structures had a volume of roughly 1 mu m(3) and a resistance of 0.1 Omega with an internal TiN diffusion barrier. The 1/f resistance noise of the vias was found to be larger than the 1/f noise in the connecting aluminum runners due to the high intrinsic noise, high resistivity TiN layer within the structure. The direct currents induced reversible increases and decreases in the resistance of the via due to electromigration damage but had no effect on the 1/f noise. The magnitude and polarity dependence of the dc current induced resistance changes are most consistent with the initial electromigration of copper. Above 200 degrees C the resistance changes became dominated by abrupt jumps in the resistance. Possible mechanisms for the abrupt resistance changes are reviewed. (C) 1996 American Institute of Physics.