The diffusion of ion-implanted F was studied by using secondary ion mass spectroscopic and thermal desorption spectroscopic techniques. Within the sub-amorphization dose range which was used, the F exhibited an anomalous out-diffusion behavior which was characterized by the depletion of F in Si substrates at temperatures above 550C. There was a complete suppression of diffusion deeper into the bulk. The F species which migrated to the surface reacted with the native oxide, and Si, to form the volatile oxyfluoride or fluoride, which then evaporated from the surface. There was clear evidence that the formation of the oxyfluoride was closely related to the thermally activated anomalous migration of F. Although the driving force for anomalous F migration was not identified, it appeared that the electric field was not a principal cause.

S.P.Jeng, T.P.Ma, R.Canteri, M.Anderle, G.W.Rubloff: Applied Physics Letters, 1992, 61[11], 1310-2