Low temperature characterization of AlSi diffusion kinetics

Abstract

The diffusion kinetics of the aluminum-silicon system at low temperatures has been characterized by a novel technique. This technique employs samples consisting of thin films comprised of alternately deposited ultrathin layers of Al and Si. This approach permits the characterization of the diffusion kinetics at the AlSi interface through the cumulative effects of several hundred interfaces while minimizing the effects of bulk material. The resistivity of these films was monitored by the “four-point probe” technique during isothermal annealing at temperatures in the range of 75C to 150C. The resistivity was observed to increase initially and later decrease, eventually stabilizing at a value lower than the starting resistivity. The increase in resistivity is attributed to an increase in disorder caused by Si diffusing into the Al layers and the decrease in resistivity to stress relief in the film. Analysis of the data has allowed the calculation of diffusion coefficients, thermal activation energy of diffusion and the gradient energy coefficient.