  To simulate the transient enhanced diffusion near the surface or interface, a
set of equations describing the impurity diffusion and quasichemical reactions
of dopant atoms and point defects in ion-implanted layers is proposed and
analyzed. The diffusion equations obtained take into account different charge
states of mobile or immobile species and drift the mobile species in the
built-in electric field and field of elastic stresses. The absorption of
self-interstitials on the surface and drift of the defects due to elastic
stresses result in the nonuniform distributions of point defects. It was shown
analytically and by means of numerical calculations that consideration of the
nonuniform defect distributions enables one to explain the phenomenon of
"uphill" impurity diffusion near the surface during annealing of ion-implanted
layers. The performed calculations of the boron concentration profile after
annealing of a shallow implanted layer agree well with the experimental data
confirming the efficiency of the proposed equations.
