STUDY OF THE INFLUENCE OF THE NONEQUILIBRIUM POINT-DEFECT CONCENTRATION GRADIENT ON THE DOPANT FLUX DURING ION-IMPLANTATION IN SILICON AT HIGH-TEMPERATURES

A relationship in a closed form for a dopant flux in silicon in the pr esence of the nonequilibrium point-defect concentration and its gradie nt is derived from the first principles on the basis of solving a simp lified boundary value problem. The experimental dopant atom distributi ons (profiles) obtained after ion implantation of B and P into Si at h igh temperatures are treated with the help of this relationship. The c alculation results show that the exponential dependence of a dopant di ffusivity at a distance from the surface can be attributed to the supe rposition of two effects: the presence of an exponentially decreasing excess of the point-defect concentration versus depth and the influenc e of the point-defect concentration gradient on the total dopant flux. Omission of the flux component attributed to the nonequilibrium point -defect concentration gradient can result in an overestimation of the point-defect density by more than one order. The conceptual model of t he radiation-induced dopant redistribution formulated in terms of a ge neralised (complete) boundary value problem is reduced to a simplified one by using the assumptions: (i) the dominant interaction of dopant atoms with only one kind of the point defects; (ii) the quasi-equilibr ium between the subsystems of the dominant point defects and the compl ex defects (dopant atom + point defect); (iii) the adiabaticapproximat ion for the nonequilibrium dilute solutions of dopant atoms and point defects in solids.