IMPACT OF LOW-TEMPERATURE TRANSIENT-ENHANCED DIFFUSION OF DOPANTS IN SILICON

Transient-enhanced diffusion due to annealing of ion-implantation damage is analysed as a function of temperature. In particular, the considerable enhancement of diffusivity at low temperatures is underlined. A non-equilibrium point-defect model is used to investigate this phenomenon in a quantitative manner. The simulation of recent experiments of P diffusion after low-dose Si implants reveals that the diffusivity enhancement can be as large as 10(4) during the first few minutes of annealing, at temperatures around 800-degrees-C. On the other hand, for high temperatures. this factor does not exceed a value of 10, during a few seconds. The influence of such behaviour is illustrated by the doping profile of a P-N-P bipolar transistor. It is shown that the base Gummel number is strongly dependent on the annealing conditions just after the base P implant. Finally, it is clearly demonstrated that only sophisticated point-defect based diffusion models can successfully analyse such problems.