Electromigration in a Blech pattern as well as in a modified Blech pattern (i.e. a Blech pattern with a no current carrying reservoir) has been studied by means of resistance measurements using multiple voltage probes. When the current density J is higher than the critical value Jc, the present method turned out to be very effective to measure the edge drift velocity. Experiments on the modified Blech pattern show two types of voids: one is formed at low current densities at the end of the reservoir (type A) and the other is formed at the intersection of the current stressed area and the reservoir at rather high current densities (type B). The measurements indicate that both type A and B voids are already formed at a very early stage in the experiment. Although the exact mechanism is not clear yet, the appearance of type B voids is related to strong inhomogeneous Joule heating. When the current density is close to Jc the resistance of most Al interconnect segments reaches saturation in a relatively short time. However, the resistance of segments at the pattern edge does not saturate within the time of the experiments. The experiments strongly suggest that plastic processes that saturate on a rather short time scale take place in the inner segments.

This content is only available via PDF.
You do not currently have access to this content.