Formation of High Quality Ultrathin Oxynitride Films by Rapid Thermal Oxidation in a Nitrous Oxide Gas Ambient

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The growth kinetics of ultrathin SiOィイD22ィエD2 films on silicon in a nitrous oxide (NィイD22ィエD20) ambient has been investigated as a function of oxidation temperature and time. The results show that the overall growth follows the linear-parabolic law proposed by Deal and Grove. The chemical etching profiles of these films indicate that the chemical etching rate near the oxinitride/silicon interface is much smaller than that at bulk layer. This means that the nitrogen-rich layer is present near the oxynitride/silicon interface. The data analysis indicates that although the oxidation proceeds by surface-limited reaction in the initial stage, it rapidly changes into a diffusion-controlled reaction. This behavior is evidenced from the fact that the reaction of the NィイD22ィエD2O molecules with the silicon surface produces an interfacial nitrogen-rich layer, which acts as a barrier to oxidant passing through the SiOィイD22ィエD2/Si interface. From the Arrhenius equation for NィイD22ィエD20 oxidation, the activation energies for the linear rate constant and for the parabolic rate constant are determined to be 1.5 and 23.3 eV, respectively.