QUANTITATIVE ANALYSIS OF NITROGEN PROFILES IN ULTRATHIN OXYNITRIDE GATE DIELECTRIC FILMS

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1. Nitrogen depth profiles in ultrathin silicon oxynitride films (〜 2.6 nm) are measured by SIMS. The results are compared with the profiles measured by high-resolution RBS (HRBS) to see if SIMS can be accurate in the topmost 1 - 2 nm region. Using a, constant RSF factor for SIMS analysis, agreement between SIMS and HRBS is not satisfactory. SIMS underestimates the nitrogen concentration at larger concentrations probably due to matrix effects. The empirical composition-dependent RSF factor is derived from the observed results. Correcting the SIMS result with the empirical RSF factor, the nitrogen depth profiles agree with the HRBS results reasonably well except for the very surface region (d < 0.3nm).2. Ultrathin silicon oxynitride films are prepared by ozone and thermal oxidation of Si(001) followed by rapid thermal nitridation. The nitrogen depth profiles in these films are mesured by high-resolution Rutherford backscattering spectroscopy. Observed nitrogen profiles are essentially the same having a peak at the SiO_2/Si interface, although the interfaces strain in the ozone oxide is much smaller than that of the thermal oxide. This indicates that the interface strain relaxation due to the nitrogen incorporation is not responsible for the nitrogen accumulation at the interface.