Characterization of multilayers by Fourier analysis of x-ray reflectivity
作者:
H. J. Voorma,
E. Louis,
N. B. Koster,
F. Bijkerk,
E. Spiller,
期刊:
Journal of Applied Physics
(AIP Available online 1997)
卷期:
Volume 81,
issue 9
页码: 6112-6119
ISSN:0021-8979
年代: 1997
DOI:10.1063/1.364360
出版商: AIP
数据来源: AIP
摘要:
We discuss a new method to characterize multilayer structures with grazing-incidence reflectivity measurements using hard x-ray radiation, such asCu-K&agr;orMo-K&agr;radiation. The method is based on the analysis of the reverse Fourier transforms of the reflectivity at the Bragg peaks in q-space, the reflectivity data being obtained from an angular scan (&thgr;−2&thgr;). This method is faster than curve fitting of the reflectivity data, results in an accurate value of the density and thickness of both materials, and needs no pre-assumptions about the material composition and the parameters of the multilayer. The method makes a distinction between interface roughness and layer thickness errors, and is independent of measurement of the critical angle. A minor disadvantage is that only an average value of the layer thickness is determined, rather than the individual layer thicknesses. As an example our method is used to analyze small-angle reflectivity measurements of Mo/Si and Co/C multilayers. The parameters thus obtained are used to model a structure, which is subsequently used to predict the near-normal incidence reflectivity at soft x-ray wavelengths. The accuracy thus found corresponds to a relative error of 5&percent;. The densities of a Mo/Si multilayer are determined independently with critical angle measurements to verify the values obtained from the grazing incidence reflectivity measurements. The results of the analysis of the Co/C multilayer are compared to values obtained using a conventional method based on the kinematical theory. However, the conventional method requires additional data of soft x-ray reflectivity measurements. The new method yields the same values for the multilayer parameters but does not require the extra soft x-ray measurements. ©1997 American Institute of Physics.
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