Polycrystalline Al-0.25at%Cu lines were investigated by means of in situ synchrotron-based white X-ray micro-beam fluorescence measurements of the evolution of Cu concentration profiles along 200µm-long 10µm-wide conductor lines, with 1.5µm-thick SiO2 passivation. The evolution of Cu concentration profiles could be manipulated by controlling the direction and magnitude of the current flow at various temperatures. The effective grain boundary diffusivity

was determined by fitting the time-dependent experimental Cu concentration profiles. The results for 275 to 325C could be described by:

D (cm2/s) = 5.0 x 10-3 exp[-0.76(eV)/kT]

H.K.Kao, G.S.Cargill, C.K.Hu: Journal of Applied Physics, 2001, 89[5], 2588-97