The diffusion of P was studied, using the spreading resistance technique and radiochemical analyses of 32P, under intrinsic conditions (the dopant concentrations were not allowed to exceed the intrinsic carrier concentration at each diffusion temperature). At such low impurity concentrations (below 2 x 1019/cm3), no interference from dislocations, plastic deformation, precipitation nor compound formation were expected. The experiments were conducted in H2 or pure Ar atmospheres and the matrix was float-zone, expitaxial or oxygen-doped (111) material. Under intrinsic conditions, the profiles obtained exhibited Fick-type behavior under all surface and bulk concentration conditions. It was found that, at between 1130 and 1405C, the intrinsic diffusivities could be described by:

D(cm2/s) = 7.4 x 10-2exp[-3.30(eV)/kT]

These data corresponded to considerably smaller diffusion coefficients than those obtained in earlier studies. Moreover, at above 1130C they were independent of surface concentration (less than 3 x 1019/cm3), bulk conductivity type (n or p) and level (6 x 1013 – 8 x 1018/cm3), surface face-to-bulk concentration ratio (105 to 3.3 x 105), and O concentrations of up to 1018/cm3.

Intrinsic Diffusion of Boron and Phosphorus in Silicon Free From Surface Effects R.N.Ghoshtagore: Physical Review B, 1971, 3[2], 389-96

Table 83

Diffusivity of 32P in Intrinsic and Extrinsic Si