  A model of the interstitial diffusion of ion-implanted boron during rapid
thermal annealing of silicon layers previously amorphized by implantation of
germanium has been proposed. It is supposed that the boron interstitials are
generated continuously during annealing due to dissolution or rearrangement of
the clusters of impurity atoms which are formed in the ion-implanted layers
with impurity concentration above the solubility limit. The local elastic
stresses arising due to the difference of boron atomic radius and atomic radius
of silicon also contribute to the generation of boron interstitials. On the
basis of the model proposed a simulation of redistribution of ion-implanted
boron during rapid thermal annealing with duration of 60 s at a temperature of
850 degrees Celsius has been carried out. The calculated profile of boron
distribution after thermal treatment agrees well with the experimental data
that confirms the adequacy of the model. A number of the parameters of
interstitial diffusion have been derived. In particular, the average migration
length of nonequilibrium boron interstitials is equal to 12 nanometers. It was
also obtained that approximately 1.96 % of boron atoms were converted to the
interstitial sites, participated in the fast interstitial migration, and then
became immobile again transferring into a substitutional position or forming
the electrically inactive complexes with defects of crystal lattice.
