MODELING OF EMISSIVITIES OF METALS AND SEMICONDUCTORS

模拟了金属和半导体（如钢板和硅片）在其表面氧化膜生长过程中的定向极化光谱发射率。在该模型中，引入了有效光学常数的概念，其中包括表面粗糙度和非均匀膜等参数的影响。结论如下：商品金属在波长大于5 μm时的光谱发射率基本符合Hagen-Rubens方程。随着波长的减小，测得的发射率与基于方程的发射率之间的差异变得很大。在试样上生长的氧化膜引起的发射率变化被视为作为电介质的氧化膜与作为导电的试样表面之间的辐射相互作用。在上述条件下的理想模型解释了除发射率随薄膜厚度的振荡外，与光谱偏振特性有关的大部分现象。实际发射率随膜厚的增加而振荡并最终收敛到一个恒定值，而模型显示发射率随膜厚的增加呈周期性变化。这意味着金属的氧化膜具有复光学常数。通过引入EMT（有效介质理论）模型的概念，建立了一个使用有效光学常数的实用模型，该模型将真实样品的表面粗糙度或非均匀膜替换为等效均匀膜。采用椭偏法测量有效光学常数。剩下的问题是研究有效光学常数的局限性，并将这个用于金属的实用模型应用到半导体晶圆上。

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.