High temperature nitrogen annealing induced interstitial oxygen (O_i) precipitation has been investigated in silicon epitaxial layers (epilayers) grown on heavily arsenic-doped Czochralski silicon wafers. Both transmission electron microscopy and secondary ion mass spectrometry data indicate a strong O_i precipitation and/or segregation in the subsurface of epilayers annealed in N_2 at 1200℃. The O_i precipitates have needlelike morphology with {111} habit planes along < 110 > directions. This precipitation is facilitated by thermal nitridation-produced vacancies or nitrogen-vacancy complexes and is sensitive to annealing conditions. Annealing in Ar or in N_2 at temperature < 1125℃ results in no epilayer subsurface O_i precipitation.
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