The transient enhanced diffusion of B in material which had been pre-doped with B isotopes was studied by using secondary ion mass spectroscopy and channelling nuclear reaction analysis. A crystal was first implanted with 11B ions to various doses, and was then annealed (1100C, 2h) so as to produce a uniform 11B dopant concentration. The 11B-doped sample and a control sample were then implanted with 40keV 10B ions. When compared to the 11B-free sample, 10B transient enhanced diffusion in the 11B-doped sample was much retarded during initial annealing (750C, 1h). Further broadening of the 10B profile occurred in 11B-doped samples after a second anneal (950C, 0.25h). The effect of 11B doping upon 10B transient enhanced diffusion was explained in terms of the trapping of Si interstitials in the 11B dopant background. The number of trapped Si interstitials, for a given 10B dose, increased with the 11B dopant concentration, but no so-called missing Si interstitials were found for a 11B doping level of 7.8 x 1017/cm3. The data showed that it was also possible to test the so-called +1 model on the basis of a knowledge of B clustering mechanisms.

Trapping of Si Interstitials in Boron Doping Background. M.B.Huang, I.V.Mitchell: Journal of Applied Physics, 1999, 85[1], 174-81