A new technique to characterize the early stages of electromigration-induced resistance changes at low current densities
One of the promising tools to study electromigration (EM) in metal lines is the high resolution resistance measuring (HRRM) technique. Since the resistance is sensitive both to structural and geometrical changes in a metal line, this technique is very useful to study the early stages of EM-induced damage. However, with a conventional HRRM-technique it is impossible to separate resistivity from geometrical variations. Here, a new analyzing technique is presented which is able to separate these two contributions during EM-expeniments at low current densities. It is found that only during the very first stage of EM resistance variations are due to resistivity variations. On the contrary, resistance variations /spl Delta/R/R>2000ppm are mainly caused by a decrease in the cross section of the metal line.