The out-diffusion profiles of N from float-zone material were measured by using secondary ion mass spectrometry. The diffusion coefficient was determined at temperatures ranging from 800 to 1200C. The total amount of N out-diffusion agreed with the change in infra-red absorption by heat treatment. The diffusivity data (table 71) could be described by:

D(cm2/s) = 2.7 x 103exp[-2.9(eV)/kT]

These values were 5 orders of magnitude larger than previously reported ones. It was suggested that the former results applied to N-N pair-like molecules, while the latter applied to substitutional N atoms. It was concluded that the recognition of the existence of the 2 types of N would permit a clarification of the effects of N upon the strengthening of crystals and upon the suppression of swirls and D-defect generation.

Diffusion Coefficient of a Pair of Nitrogen Atoms in Float-Zone Silicon. T.Itoh, T.Abe: Applied Physics Letters, 1988, 53[1], 39-41

Table 71

Diffusivity of Paired N in Si