Grain boundary diffusion of Al in polycrystalline films was measured using Auger sputter profiling techniques between 350 and 425C. The Al atoms were observed to diffuse through Si grain boundaries and to accumulate near to Si/SiO2 interfaces. The diffusion problem was analyzed using a simple model in which a steady-state flux of Al through Si grain boundaries was taken up by an effectively infinite sink at the Si/SiO2 interface. Auger measurements yielded quantitative information regarding the concentration gradient in the center of the polycrystalline Si layer and the amount of accumulation near to the Si/SiO2 interface. From this information, the grain boundary diffusion coefficient was determined. This was fitted to an Arrhenius relationship:

D(cm2/s) = 1.3 x 107exp[-2.64(eV)/kT]

The measured activation energy was consistent with that for grain boundary diffusion of P and B as well as with the pipe diffusion of As in Si.

Grain Boundary Diffusion of Aluminum in Polycrystalline Silicon Films. J.C.M.Hwang, P.S.Ho, J.E.Lewis, D.R.Campbell: Journal of Applied Physics, 1980, 51[3], 1576-81