The diffusion of B was studied by using the spreading resistance technique under intrinsic conditions. That is, the dopant concentrations were not allowed to exceed the intrinsic carrier concentration in Si at each diffusion temperature. At such low impurity concentrations (below 2 x 1019/cm3), no interference from dislocations, plastic deformation, precipitation or compound formation upon the resultant concentration profiles was expected. The experiments were conducted in H2 or pure Ar atmospheres and the matrix was float-zone expitaxial and oxygen-doped (111) material. Under intrinsic conditions, the concentration profiles obtained showed Fickian behavior under all surface and bulk concentration conditions. Between 1130 and 1405C, the intrinsic diffusivity could be described by:

D(cm2/s) = 2.1 x 10-3exp[-2.85(eV)/kT]

These data corresponded to considerably smaller diffusion coefficients than those obtained in earlier studies. Also, at above 1130C, they were independent of the 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 21

Diffusion of B in Single Crystals