A resistometric method to characterize electromigration at the wafer level

Abstract

Electromigration resistometric measurements at the wafer level cannot be carried out with adequate precision using standard DC techniques, due to high, non-stable thermoelectric voltages arising at the pad/probe-tip interface. In this work an AC resistometric technique is proposed, which allows the detection of very small resistance changes in the early stages of electromigration process. Measurements were carried out at different temperatures and an activation energy was extracted. The validity of the Matthiessen's rule for the interpretation of electromigration data was studied. Its applicability was not proved: experimental data showed that the resistance changes can be explained in terms of geometrical variations even in the first stages of electromigration.