A model of high- and low-temperature phosphorus diffusion in silicon by a dual pair mechanism

A model of phosphorus diffusion in silicon was developed on the basis of a dual pair mechanism; according to this model, the contribution of the impur ity-vacancy (PV) and impurity-self-interstitial (PI) pairs to diffusion is accounted for directly in terms of the phosphorus diffusion coefficient. A violation of thermodynamic equilibrium in relation to native point defects occurs as a result of diffusion of the PI neutral pairs. At the high-temper ature diffusion stage, the phosphorus diffusion is described by a single di ffusion equation with the diffusion coefficient dependent on both the local and surface phosphorus concentrations; whereas at the next (occurring at l ower temperatures) stage, the phosphorus diffusion is described by two diff usion equations for the total concentrations of the components containing p hosphorus and self-interstitials. An anomalously high rate of the low-tempe rature diffusion is ensured by excess self-interstitials accumulated in the doped layer during the preceding high-temperature diffusion. The model mak es it possible to quantitatively account for the special features of the ph osphorus diffusion in a wide range of the surface concentrations at both th e high (900-1100 degreesC) and lower (500-700 degreesC) temperatures. (C) 2 001 MAIK "Nauka/Interperiodica".