Doping and damage dose dependence of implant induced transient enhanced diffusion below the amorphization threshold

Abstract
Special test structures were used to isolate the dependence of transient enhanced diffusion on damage dose and on doping concentration. The structures consisted of 200 nm boron-doped layers with an undoped silicon capping layer 300 nm thick. The boron concentrations varied from 5×1016 to 5×1018/cm3. Damage was introduced by 75 keV, Si implants with doses ranging from 1×1012 to 5×1013/cm2. Annealing at 750 °C for 120 min produced a large enhancement in the boron diffusivity. The enhancement increased with increasing Si dose, but in a sublinear manner. The enhancement decreased with increasing boron doping concentration, even for doping concentrations below the intrinsic electron concentration. A phenomenological defect-doping reaction model is described which predicts both of these essential features of damage enhanced diffusion. We conclude that it will be necessary to treat the full coupling between defects and dopant atoms in order to model damage enhanced diffusion effects.