Electromigration saturation in a simple interconnect tree

Abstract

Electromigration-saturation experiments have been carried out on passivated “L”-shaped interconnects which had three contacts through W-filled vias at the ends and at the corners of the L’s. Currents of different magnitudes and directions were independently applied in the two limbs of the L’s. Variations in the steady-state electrical resistances were observed, and attributed to a variation in the location of the voids along the lines. Variations in the rate of approach to the steady state were also observed, and are attributed to variations in void shapes. The effects of electromigration in L-shaped interconnects were simulated using an electromigration simulator based on the one-dimensional Korhonen et al. [J. Appl. Phys. 73, 3790 (1993)] model for electromigration, modified to include the effects of junctions. It is shown that, using a single set of input parameters and information about void shapes, the simulation can be used to make accurate worst-case predictions of the evolving and the steady state values of electromigration-induced resistance changes in these simple L-shaped interconnect trees.