BORON PREDEPOSITION IN Si USING BBr, 613into the silicon and the rate-determining step is the diffusion of B203 through the boron glass (5). Reproducibility and uniformity of the process depend largely on the oxygen and boron tribromide concentrations in the furnace.(ii) BRL present.--Q is limited by the diffusivity of boron in silicon and by its surface concentration. This concentration, which is not the solubility one, changes with the composition of the BRL. However the process is repeatable since the changes of Cs with doping gas composition are small. The different values of Q obtained by predeposition carried out with the same time and temperature can be quantitatively explained by the change in Cs, if the large concentration dependence of the boron diffusion coefficient and the translation of the BRL-Si interface are considered.