ISSN:
1089-7550
Source:
AIP Digital Archive
Topics:
Physics
Notes:
The mechanism of plasma afterglow oxidation of silicon by atomic oxygen is discussed in terms of a physical model that includes recombination of the oxidant atoms during their diffusion through the SiO2 layer. Inclusion of a first-order O loss term in the continuity equation that governs the unbound O atoms leads to a biexponential concentration profile in the oxide. The corresponding time-dependent O flux across the SiO2/Si interface results in an oxide growth equation that is a more general form of the classical Deal–Grove model. Confrontation with available experimental data shows that the general expression can be abbreviated for oxide widths w≥0.1 nm as t= (A2/B)[exp(w/A)+exp(−w/A)−exp(wi/A)−exp(−wi/A)], where wi is the native oxide width. The two model parameters are A≡(square root of)D/k and B≡2HD[O]g/nb, with D being the diffusivity and k the first-order loss rate constant of unbound O atoms in SiO2, H the SiO2/gas Henry equilibrium ratio of free O atoms, [O]g=the gas-phase O atom concentration, and nb=the bound-O number density in SiO2. The two-parameter model provides excellent fits (σ(approximately-equal-to)2% of final w) to the available data on both n- and p-type Si, strikingly better than fits obtained by the Deal–Grove equation in particular for p-type Si. The values deduced for the model parameters A and B provide proof for the controlling importance of the O-atom recombination process, especially for p-type Si. The model parameters also allow values to be derived for other pertaining physical constants; e.g., the product HD is deduced to be 2.4×10−9 cm2 s−1 at T(approximately-equal-to)850 K, in close agreement with the known HD value for neon atoms in SiO2, equal to 5.2×10−9 cm2 s−1.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1063/1.353107
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