The role which was played by extended defect evolution in anomalous B diffusion during rapid thermal annealing was studied by means of secondary ion mass spectroscopy and transmission electron microscopy. Pre-damaged wafers with low-dose Si implantation, pre-amorphized wafers with high-dose Si implantation, and monocrystalline wafers with no previous implantation were used. It was found that low-dose Si pre-implantation significantly reduced the channelled tail during subsequent B implantation, and resulted in more anomalous B diffusion and more rapid annealing of extended defects during rapid thermal annealing, as compared with crystalline Si samples. The diffusion of B which had been implanted into pre-amorphized Si was found to be anomalous in nature and its magnitude depended upon the rapid thermal annealing temperature. The temperature dependence was found to be due to the difference in the density of dislocation loops which formed during rapid thermal annealing at the original amorphous/crystalline interface. These loops determined the effectiveness of the trapping Si interstitials which diffused, from the crystalline side of the original amorphous/crystalline interface, to the epitaxially re-grown region. The anomalous B diffusion in the crystalline Si samples was found to be a sensitive function of the implant dose. The diffusion displacement increased, and the anomalous diffusion effect lasted longer, with increasing implant dose. An enhanced diffusion after longer periods of time, in samples with higher implant doses, was related to the formation and annealing of extended defects. At very high doses (greater than 2 x 1015/cm2), where the peak B concentration was above the solid solubility, excess diffusion in the high B concentration region was observed. The excess diffusion was explained in terms of B segregation into interstitial dislocation loops in the early stages of rapid thermal annealing, and to the subsequent annealing of these dislocation loops after the initially large anomalous tail diffusion.

Y.M.Kim, G.Q.Lo, H.Kinoshita, D.L.Kwong, H.H.Tseng, R.Hance: Journal of the Electrochemical Society, 1991, 138[4], 1122-30