MODELING OF EMISSIVITIES OF METALS AND SEMICONDUCTORS

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Modeling of directional polarized spectral emissivities of metals and semiconductors such as steel sheets and Si wafers during the growth of oxide film on their surfaces has been achieved. In this model, a concept of an effective optical constant is introduced, which includes the effect of some parameters such as surface roughness and inhomogeneous film and so on. The concluding remarks are as follows,Spectral emissivities of commercial metals correspond mostly to Hagen-Rubens equation at wavelengths of more than 5 μm. With decreasing wavelength, the difference between a measured emissivity and one based on the equation becomes large. The emissivity change caused by oxide film grown on a specimen is treated as the interaction of radiation between the oxide film to be a dielectric and the surface of the specimen to be a conductive.An idealistic model under the above condition explains most of the phenomena concerning to directional polarized properties of spectral emissivities except the emissivity oscillation with the film thickness. Real emissivities oscillate and converge finally to a constant value with increasing film thickness, while the model shows a periodical change of emissivities with increasing film thickness. This means an oxide film of a metal has a complex optical constant.A practical model which uses an effective optical constant has been developed by introducing a concept of EMT (Effective Medium Theory) model which replaces surface roughness or an inhomogeneous film of a real specimen to an equivalent homogeneous film. An ellipsometric method is used to measure an effective optical constant.The remaining problems are to investigate the limitation of effective optical constants and also to apply this practical model used for metals to semiconductor wafers.