Defects in as-grown thermal oxide were investigated by photoluminescence (PL) spectroscopy using synchrotron radiation as a light source. A PL band at 3.3 eV was observed under excitation at 5 eV for dry thermal oxide at room temperature. The PL band was also observed for forming-gas annealed oxide, in which the 3.3 eV PL was either enhanced by subsequent vacuum annealing or suppressed by hydrogen exposure. The PL measurements on oxynitride films show that effect of nitrogen incorporation on the 3.3 eV PL is less significant than that of hydrogen. Wide observability of the 3.3 eV PL band for oxide films prepared under various conditions indicates the intrinsic nature of the defects in thermal oxide introduced during thermal oxidation of silicon.
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