The open-volume defects which were introduced into (100) crystals during F implantation were investigated by means of variable-energy positron beam depth profiling. The behavior of the implantation-induced lattice defects during high-temperature annealing, and their role in the surface-oriented diffusion of F impurities, was considered. The defects became mobile, and recovered at temperatures below 550C. This was well before the onset of F diffusion, as detected by using secondary ion mass spectroscopic profiling. This suggested that, after irradiation and annealing, the F occupied substitutional sites to which positrons were insensitive. The anomalous F diffusion which was seen in secondary ion mass spectrometry data was explained in terms of a 2-step diffusion mechanism in which the diffusion kinetics were governed by the dissociation of substitutional F into an interstitial F and a vacancy; followed by rapid diffusion of the interstitial F and of the vacancy through the crystal to the surface.

Role of Implantation-Induced Defects in Surface-Oriented Diffusion of Fluorine in Silicon. C.Szeles, B.Nielsen, P.Asoka-Kumar, K.G.Lynn, M.Anderle, T.P.Ma, G.W.Rubloff: Journal of Applied Physics, 1994, 76[6], 3403-9