Low-energy ion polishing of Si in W/Si soft X-ray multilayer structures

R. V. Medvedev, K. V. Nikolaev, A. A. Zameshin, D. Ijpes, I. A. Makhotkin, S. N. Yakunin, A. E. Yakshin, F. Bijkerk

Research output: Contribution to journalArticleAcademicpeer-review

Abstract

The effect of ion polishing in sputter deposited W/Si multilayer mirrors with a d-spacing of 2.5 nm was studied. 0.1 to 0.5 nm of Si were etched with 100 eV Ar+ ions. This process resulted in a pronounced reduction in diffused scattering, measured at wavelengths about 0.1 nm. However, CuKa X-ray specular reflectivity and AFM showed only a marginal reduction of the roughness amplitude in the systems. Furthermore, the soft X-ray reflectivity at 0.84 and 2.4 nm did not show any changes after the ion polishing as compared to the nonpolished structures. Grazing incidence X-ray reflectivity (GIXR) analysis revealed that there was no pure W present in the deposited multilayers, with WSi2 being formed instead. As a result, it was concluded that the initial roughness in W/Si multilayers grown by magnetron sputtering is not the major factor in the reflectivity deviation from the calculated value for an ideal system. Nevertheless, the grazing incidence small-Angle X-ray scattering (GISAXS) analysis revealed that ion polishing reduces the vertical propagation of roughness from layer to layer by a factor of two, as well as favorably affecting the lateral correlation length and Hurst parameter. These improvements explain the reduction of diffused X-ray scattering at 0.1 nm by more than an order of magnitude, which is relevant for applications like high resolution XRD analysis.

Original languageEnglish
Article number045302
JournalJournal of applied physics
Volume126
Issue number4
DOIs
Publication statusE-pub ahead of print/First online - 25 Jul 2019

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polishing
laminates
reflectance
roughness
ions
x rays
grazing incidence
scattering
energy
magnetron sputtering
spacing
atomic force microscopy
mirrors
deviation
propagation
high resolution
wavelengths

Cite this

@article{3709f4780eed4f5088020345a78adc30,
title = "Low-energy ion polishing of Si in W/Si soft X-ray multilayer structures",
abstract = "The effect of ion polishing in sputter deposited W/Si multilayer mirrors with a d-spacing of 2.5 nm was studied. 0.1 to 0.5 nm of Si were etched with 100 eV Ar+ ions. This process resulted in a pronounced reduction in diffused scattering, measured at wavelengths about 0.1 nm. However, CuKa X-ray specular reflectivity and AFM showed only a marginal reduction of the roughness amplitude in the systems. Furthermore, the soft X-ray reflectivity at 0.84 and 2.4 nm did not show any changes after the ion polishing as compared to the nonpolished structures. Grazing incidence X-ray reflectivity (GIXR) analysis revealed that there was no pure W present in the deposited multilayers, with WSi2 being formed instead. As a result, it was concluded that the initial roughness in W/Si multilayers grown by magnetron sputtering is not the major factor in the reflectivity deviation from the calculated value for an ideal system. Nevertheless, the grazing incidence small-Angle X-ray scattering (GISAXS) analysis revealed that ion polishing reduces the vertical propagation of roughness from layer to layer by a factor of two, as well as favorably affecting the lateral correlation length and Hurst parameter. These improvements explain the reduction of diffused X-ray scattering at 0.1 nm by more than an order of magnitude, which is relevant for applications like high resolution XRD analysis.",
author = "Medvedev, {R. V.} and Nikolaev, {K. V.} and Zameshin, {A. A.} and D. Ijpes and Makhotkin, {I. A.} and Yakunin, {S. N.} and Yakshin, {A. E.} and F. Bijkerk",
year = "2019",
month = "7",
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doi = "10.1063/1.5097378",
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Low-energy ion polishing of Si in W/Si soft X-ray multilayer structures. / Medvedev, R. V.; Nikolaev, K. V.; Zameshin, A. A.; Ijpes, D.; Makhotkin, I. A.; Yakunin, S. N.; Yakshin, A. E.; Bijkerk, F.

In: Journal of applied physics, Vol. 126, No. 4, 045302, 25.07.2019.

Research output: Contribution to journalArticleAcademicpeer-review

TY - JOUR

T1 - Low-energy ion polishing of Si in W/Si soft X-ray multilayer structures

AU - Medvedev, R. V.

AU - Nikolaev, K. V.

AU - Zameshin, A. A.

AU - Ijpes, D.

AU - Makhotkin, I. A.

AU - Yakunin, S. N.

AU - Yakshin, A. E.

AU - Bijkerk, F.

PY - 2019/7/25

Y1 - 2019/7/25

N2 - The effect of ion polishing in sputter deposited W/Si multilayer mirrors with a d-spacing of 2.5 nm was studied. 0.1 to 0.5 nm of Si were etched with 100 eV Ar+ ions. This process resulted in a pronounced reduction in diffused scattering, measured at wavelengths about 0.1 nm. However, CuKa X-ray specular reflectivity and AFM showed only a marginal reduction of the roughness amplitude in the systems. Furthermore, the soft X-ray reflectivity at 0.84 and 2.4 nm did not show any changes after the ion polishing as compared to the nonpolished structures. Grazing incidence X-ray reflectivity (GIXR) analysis revealed that there was no pure W present in the deposited multilayers, with WSi2 being formed instead. As a result, it was concluded that the initial roughness in W/Si multilayers grown by magnetron sputtering is not the major factor in the reflectivity deviation from the calculated value for an ideal system. Nevertheless, the grazing incidence small-Angle X-ray scattering (GISAXS) analysis revealed that ion polishing reduces the vertical propagation of roughness from layer to layer by a factor of two, as well as favorably affecting the lateral correlation length and Hurst parameter. These improvements explain the reduction of diffused X-ray scattering at 0.1 nm by more than an order of magnitude, which is relevant for applications like high resolution XRD analysis.

AB - The effect of ion polishing in sputter deposited W/Si multilayer mirrors with a d-spacing of 2.5 nm was studied. 0.1 to 0.5 nm of Si were etched with 100 eV Ar+ ions. This process resulted in a pronounced reduction in diffused scattering, measured at wavelengths about 0.1 nm. However, CuKa X-ray specular reflectivity and AFM showed only a marginal reduction of the roughness amplitude in the systems. Furthermore, the soft X-ray reflectivity at 0.84 and 2.4 nm did not show any changes after the ion polishing as compared to the nonpolished structures. Grazing incidence X-ray reflectivity (GIXR) analysis revealed that there was no pure W present in the deposited multilayers, with WSi2 being formed instead. As a result, it was concluded that the initial roughness in W/Si multilayers grown by magnetron sputtering is not the major factor in the reflectivity deviation from the calculated value for an ideal system. Nevertheless, the grazing incidence small-Angle X-ray scattering (GISAXS) analysis revealed that ion polishing reduces the vertical propagation of roughness from layer to layer by a factor of two, as well as favorably affecting the lateral correlation length and Hurst parameter. These improvements explain the reduction of diffused X-ray scattering at 0.1 nm by more than an order of magnitude, which is relevant for applications like high resolution XRD analysis.

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