Nitrogen self-diffusion in silicon nitride thin films probed with isotope heterostructures

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Abstract
The self-diffusion of nitrogen is measured with secondary ion mass spectrometry in isotopically enriched polycrystalline and amorphous Si 3 N 4 14 ∕ Si 3 N 4 15 ∕ Si 3 N 4 14 isotopeheterostructures which were produced by reactive magnetron sputtering. The N diffusivities of polycrystalline films in the temperature range between 1130 and 1700 ° C follow an Arrhenius law over four orders of magnitude with a single activation enthalpy of Δ H = 4.9 eV and a pre-exponential factor of D 0 = 1 × 10 − 6 m 2 ∕ s . The calculated entropy of diffusion of Δ S ≈ 0 k B indicates a diffusion mechanism with localized point defects, in contrast to extended point defects usually found in semiconductors, like Si , Ge , and GaAs . The diffusivities in the amorphous state between 1130 and 1180 ° C do not differ significantly from those in the polycrystalline state.