Electromigration of copper in Al(0.25 at. % Cu) conductor lines

Electromigration and diffusion of Cu have been investigated for polycrystal line Al(0.25 at. % Cu) conductor lines. In situ measurements of the evoluti on of Cu concentration profiles along 200 mum long, 10 mum wide conductor l ines with 1.5 mum thick SiO2 passivation during electromigration have been obtained by synchrotron-based white x-ray microbeam fluorescence. The appar ent effective charge Z(Cu)* of Cu in Al(Cu) has been found to be -8.6 +/-1. 0. The evolution of Cu concentration profiles can be manipulated by control ling the direction and magnitude of the current flow at different temperatu res. The effective grain boundary diffusivity D-Cu(eff) has been determined by fitting the time dependent experimental Cu concentration profiles. The results show Arrhenius behavior of D-Cu(eff) = D-0 exp(-Q/kT) for T = 275-3 25 degreesC with D-0 = 10(-(2.3 +/-1.6)) cm(2)/s and Q = 0.76 +/-0.19 eV. ( C) 2001 American Institute of Physics.