DETECTION OF CURRENT-INDUCED VACANCIES IN THIN ALUMINUM-COPPER LINES USING POSITRONS

In situ depth-resolved positron annihilation spectroscopy (PAS) is use d to show dynamic formation of vacancies in 1 mu m x 1 mu m Al-0.5 wt% Cu lines under current flow. We show that the number of vacancies in these lines increases when a de current (8 x 10(4) A/cm(2)) is applied . This increase in vacancy concentration is substantially greater than that due to thermal vacancy generation alone (4 x 10(18) cm(-3) versu s 3 x 10(17) cm(-3)). Isothermal measurements (with no current flow) y ield a vacancy formation energy of 0.60+/-0.02 eV. These results show that PAS can be used to examine the initial stages of interconnect dam age due to electromigration. (C) 1996 American Institute of Physics.