Boron Redistribution in Sintered α‐SiC During Thermal Oxidation

The redistribution of the boron impurity in sintered α‐SiC during thermal oxidation was investigated over the temperature range 1200· to 1400,°C using sputter‐induced photon spectrometry (SIPS). The process was modeled with the Stanford University Processing Engineering Models Program (SUPREM) which permitted the estimation of diffusivities of boron in the growing oxide and the substrate. The process is characterized by segregation of the boron in the oxide near the interface and a corresponding depletion of boron in the substrate. The apparent diffusivities in the oxide were about three orders of magnitude higher than the published values for boron in pure SiO 2 , presumably because the film is much less pure than pure SiO 2 . The apparent diffusivities of the boron in the polycrystalline silicon carbide were almost five orders of magnitude higher than the published values for boron in single‐crystal silicon carbide. The diffusivities in the silicon carbide represent boron transport via the grain boundaries which were partially oxidized during the thermal treatment.