Resolving lateral and vertical structures by ellipsometry using wavelength range scan

THIN SOLID FILMS

卷:571

Article; Proceedings Paper

Petrik, P.^1,2  Agocs, E.^1,2  Volk, J.¹  Lukacs, I.¹  Fodor, B.^1,3  Kozma, P.¹  Lohner, T.¹  Oh, S.^4,5  Wakayama, Y.^4,5  Nagata, T.⁴  Fried, M.^1,2 

[1] Inst Tech Phys & Mat Sci MFA, Res Ctr Nat Sci, H-1121 Budapest, Hungary

[2] Univ Pannonia, Fac Informat Technol, Doctoral Sch Mol & Nanotechnol, H-8200 Veszprem, Hungary

[3] Univ Pecs, Fac Sci, H-7624 Pecs, Hungary

[4] Natl Inst Mat Sci, Int Ctr Mat Nanoarchitecton, Tsukuba, Ibaraki 3050044, Japan

[5] Kyushu Univ, Fac Engn, Dept Chem & Biochem, Tsukuba, Ibaraki 3050044, Japan

关键词: Spectroscopic ellipsometry;    Depth profile;    Nanocrystal;   

DOI  :  10.1016/j.tsf.2014.02.008

来源: Elsevier

【 摘 要 】

For most thin film structures, by changing the wavelength range to fit ellipsometric spectra, the values of the fitted parameters also change to a certain extent. The reason is that compared with the ellipsometric sensitivity many thin films are vertically non-uniform. In absorbing films with significant dispersion in the used wavelength range, the penetration depth of probing light can show large variations depending on the wavelength. Consequently, the value of a fitted parameter for a certain wavelength range is a weighted sum of structural information over different depth ranges corresponding to the different wavelengths. By changing the wavelength range, the range of penetration depths can be adjusted, and the fitted values can be plotted as a function of the probed depth range calculated directly from the determined or tabulated extinction coefficients. We demonstrate the results on deposited polycrystalline thin films. The advantage of this approach over the parameterization of structural properties as a function of depth is that the wavelength scan approach requires no parameterized depth distribution model for the vertical dependence of a layer property. The difference of the wavelength scan method and the vertical parameterization method is similar to the difference between the point-by-point and the parameterized dielectric function methods over the used wavelength range. The lateral structures strongly influence the ellipsometric response, as well. One of the most remarkable effects is when the lateral feature sizes approach the wavelength of the probing light. In this case the effective medium method is not valid any more, since scattering and depolarization occurs. By scanning the wavelength range, the limit wavelength of the onset of scattering can be found, and used for the determination of the corresponding critical lateral period length. (C) 2014 Elsevier B.V. All rights reserved.

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