Boron Predeposition in Silicon Using BBr3

The process of boron predeposition in silicon using a source is investigated for different times, temperatures, and doping gas compositions. The experimental conditions leading to the formation on the silicon surface of the boron‐rich layer are determined. It is shown that the boron surface concentration in silicon, in equilibrium with the boron‐rich layer, is higher than the solubility value and depends on doping gas composition. Different surface concentrations corresponding to different boron‐rich layer compositions can explain the "anomalous" decrease of the amount of boron entering the silicon, which is observed in particular experimental conditions. In this evaluation both the strong concentration dependence of the boron diffusion coefficient and the translation of the BRL‐Si interface have also been taken into account. Finally the rate‐determining steps of the transfer of boron into silicon are discussed.