The temporal evolution of transient enhanced diffusion in crystalline material during annealing after B implantation was modelled as a system of diffusion-reaction equations for the dopant species and for Si point defects. The concept of point defect impurity pair diffusion under equilibrium conditions was used to describe the diffusion. The out-diffusion of implantation-induced Si self-interstitials, and a kick-out reaction (Bi  Bs + I) were assumed to be the leading mechanisms for B activation. In the case of low-dose B-ion implantation, the analysis began with a defect distribution of Gaussian form, with 1 interstitial per implanted B atom. At higher B doses, the areal density of this interstitial distribution was constant, but the depth position of its peak depended upon the B dose. Local equilibrium of the reactions between point defects and B species was assumed to be achieved before the onset of diffusion. The predicted B depth profiles were compared with published data. Doses of between 2 x 1014 and 5 x 1015/cm2 were analyzed, and annealing temperatures and times which ranged from 800 to 1000C and from to 10s to 8h were used. Although the approach involved only simple assumptions, important deficiencies were found only in certain cases of annealing after high-dose B implantation. It was concluded that the trapping of free interstitials by extended defects became important at low temperatures and at long annealing times. If the depth region with the maximum B concentration was close to amorphization in its as-implanted state, B over-activation which was beyond the present model was found. In all other cases, it was possible to obtain a reasonable model for transient enhanced diffusion.

H.U.Jäger: Journal of Applied Physics, 1995, 78[1], 176-86