The As diffusion coefficient was determined, as a function of concentration, via the Boltzmann-Matano analysis of profiles that resulted from the diffusion of the dopant out of its conjugate phase precipitates during furnace annealing (900 or 1050C). The samples had been heavily doped using ion implantation. This method ensured a constant As diffusion source, and a doping range of up to 3 x 1021/cm3. The dopant profiles were determined by using secondary neutral mass spectroscopy. It was found that the diffusivity of As increased with dopant content, and attained a maximum at a concentration which corresponded closely to the saturation value of the carrier density. This demonstrated that the carrier density represented a limit on the concentration of unclustered dopant at the diffusion temperature. A simulation model was developed which could accurately describe the evolution of the As profile during annealing by using diffusivity data and taking account of precipitation and clustering phenomena.

High-Concentration Diffusivity and Clustering of Arsenic and Phosphorus in Silicon. S.Solmi, D.Nobili: Journal of Applied Physics, 1998, 83[5], 2484-90