  A theoretical investigation of the microscopic mechanisms provided the
transient enhanced diffusion of boron atoms during rapid thermal annealing of
silicon substrates doped by high fluence ion implantation was carried out. To
compare the mechanisms a model of the transient enhanced diffusion due to
migration of the pairs "boron atom - silicon interstitial" was developed. It is
supposed that during annealing dissolution of the clusters incorporated boron
atoms occurs. During cluster dissolution, a fraction of boron atoms occupies a
substitutional position, whereas other atoms become interstitial. It was shown
from the comparison of the shape of calculated boron concentration profile
after annealing with the experimental data that at a temperature of 850 Celcius
degrees and below the nonequilibrium boron interstitials are responsible for
the transient enhanced diffusion. On the other hand, at a temperature of 850
Celcius degrees and above a major contribution to the transient enhanced
diffusion is provided by the pairs "boron atom - silicon interstitial".
