The self-diffusion of N was measured, using secondary ion mass spectrometry, in isotopically enriched polycrystalline and amorphous 14Si3N4/15Si3N4/14Si3N4 isotopic heterostructures which had been produced by reactive magnetron sputtering. The N diffusivities of polycrystalline films between 1130 and 1700C obeyed the Arrhenius law:

D (m2/s) = 1 x 10-6 exp[-4.9(eV)/kT]

over 4 orders of magnitude. The calculated entropy of diffusion of about 0k indicated a diffusion mechanism with localized point defects, in contrast to the extended point defects usually found in semiconductors such as Si, Ge and GaAs. The diffusivities in the amorphous state between 1130 and 1180C did not differ significantly from those in the polycrystalline state (figure 34).

Nitrogen Self-Diffusion in Silicon Nitride Thin Films Probed with Isotope Heterostructures. H.Schmidt, G.Borchardt, M.Rudolphi, H.Baumann, M.Bruns: Applied Physics Letters, 2004, 85[4], 582-4

Figure 34

Diffusivity of 15N in Si3N4