The grain boundary diffusion of Al in polycrystalline films was measured by using Auger sputter profiling techniques at 350 to 425C. The Al atoms diffused through the Si grain boundaries and accumulated near to Si/SiO2 interfaces. The diffusion problem was analyzed by 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:

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

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

J.C.M.Hwang, P.S.Ho, J.E.Lewis, D.R.Campbell: Journal of Applied Physics, 1980, 51[3], 1576-81