Kinetics of Phosphorus Predeposition in Silicon Using POCl3

Phosphorus predeposition in silicon using a source and oxidizing conditions has been studied over a wide range of temperature (850°–1200°C) and doping gas compositions, by determining the total and electrically active dopant and the thickness of the surface oxide. The dependence of the fraction of electrically inactive phosphorus on temperature, time, and doping gas composition was studied; and it is reported that phosphide precipitation takes place in the course of the predeposition. These observations lead to the conclusion that the flux of phosphorus is not limited by the solubility of this element in silicon, and this is confirmed by the results of the study of the kinetics, which are reported. They show that the rate‐determining process of phosphorus predeposition and the associated oxide growth is the diffusion across the oxide layer. The amount of dopant predeposited in an isothermal process increases with a parabolic time law and a similar behavior is observed for the oxide thickness It is shown that and are constants in a wide range of experimental conditions, and the dependence of and on gas composition is reported. A method, based on surface resistivity measurements after drive‐in, which provides quantitative determinations of the predeposited phosphorus in satisfactory agreement with activation analysis, is reported in the Appendix.