Smoothing of interfaces in ultrathin Mo/Si multilayers by ion bombardment

Kloidt, A.; Stock, Hans-Jürgen; Kleineberg, Ulf; Döhring, Thorsten; Pröpper, M.; Schmiedeskamp, B.; Heinzmann, Ulrich

doi:10.1016/0040-6090(93)90586-e

Cited by 19 publications

(6 citation statements)

References 12 publications

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“…Later, the first direct evidence of ion beam induced surface smoothing was found by Spiller, who used low energy ion bombardment at grazing ion incidence angles to smooth interfaces in the process of deposition of multilayer x-ray mirrors [34]. This technique is now well established for the compensation of growing film roughness during the deposition of multilayers for x-ray optics where the interface roughness is very crucial for the reflectivity of the mirror [35][36][37][38][39]. In the meantime, the benefits of ion beam smoothing have been demonstrated for a lot of further applications such as the reduction of Néel 'orange peel' coupling in magnetic tunnel junctions by smoothing of NiFe films [40] or the conductivity enhancement of ultrathin metal films [41].…”

Section: Introductionmentioning

confidence: 99%

Large area smoothing of surfaces by ion bombardment: fundamentals and applications

Frost¹,

Fechner²,

Ziberi³

et al. 2009

J. Phys.: Condens. Matter

121

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Ion beam erosion can be used as a process for achieving surface smoothing at microscopic length scales and for the preparation of ultrasmooth surfaces, as an alternative to nanostructuring of various surfaces via self-organization. This requires that in the evolution of the surface topography different relaxation mechanisms dominate over the roughening, and smoothing of initially rough surfaces can occur. This contribution focuses on the basic mechanisms as well as potential applications of surface smoothing using low energy ion beams. In the first part, the fundamentals for the smoothing of III/V semiconductors, Si and quartz glass surfaces using low energy ion beams (ion energy: ≤2000 eV) are reviewed using examples. The topography evolution of these surfaces with respect to different process parameters (ion energy, ion incidence angle, erosion time, sample rotation) has been investigated. On the basis of the time evolution of different roughness parameters, the relevant surface relaxation mechanisms responsible for surface smoothing are discussed. In this context, physical constraints as regards the effectiveness of surface smoothing by direct ion bombardment will also be addressed and furthermore ion beam assisted smoothing techniques are introduced. In the second application-orientated part, recent technological developments related to ion beam assisted smoothing of optically relevant surfaces are summarized. It will be demonstrated that smoothing by direct ion bombardment in combination with the use of sacrificial smoothing layers and the utilization of appropriate broad beam ion sources enables the polishing of various technologically important surfaces down to 0.1 nm root mean square roughness level, showing great promise for large area surface processing. Specific examples are given for ion beam smoothing of different optical surfaces, especially for substrates used for advanced optical applications (e.g., in x-ray optics and components for extreme ultraviolet lithography).

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Section: Introductionmentioning

confidence: 99%

Large area smoothing of surfaces by ion bombardment: fundamentals and applications

Frost¹,

Fechner²,

Ziberi³

et al. 2009

J. Phys.: Condens. Matter

121

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“…This results in a transition from conformal film growth to activated film growth with surface diffusion of the particles arriving at the surface as illustrated in Figure 5. The experimental implementation can be made in different ways: 1) applying a BIAS voltage at the substrate surface connected with an acceleration of ions from the plasma to the film surface [16] or 2) using additional ion sources for the direct bombardment during or after the film growth [17,18]. In both cases the kinetic energies have to be tuned very carefully since any volume diffusion resulting in intermixing of the materials has to be avoided.…”

Section: Multilayer Coatingmentioning

confidence: 99%

Specific aspects of roughness and interface diffusion in non-periodic Mo/Si multilayers

et al. 2014

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Most of the currently used reflective coatings for EUV and X-ray mirrors are periodic nanometer multilayers. Depending on the number of periods and the absorption in the multilayer stack a certain band width of the incoming radiation can be reflected. In order to increase the integral reflectance or to accept larger ranges of incidence angles, non-periodic multilayers are needed. With the transition from periodic to non-periodic multilayers new challenges arise for the deposition process. Since the reflectance spectra are sensitive to every single layer thickness a precise coating control and an exact knowledge of the interface reactions are required. Furthermore substrate roughness influences the reflectance spectra. With an advanced coating process using additional ion bombardment during thin film growth the integrated reflectance of broadband mirrors can be conserved even for an initial substrate roughness of about 0.7 nm rms

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“…New integrated circuits featuring complex patterns, with sizes smaller than 100 nm, are nowadays printed by means of extreme-ultraviolet (EUV) lithography [42,43]. In this process, the low normal-incidence reflectivity exhibited in the soft X-ray wavelength region by standard optical materials, can be enhanced by surface coating with multilayers, owing to constructive interference occurring in this stack.…”

Section: Multilayered Materialsmentioning

confidence: 99%

“…Multiple Mo/Si bilayers, with "elemental" thickness in the range of ~3 to ~20 nm, have proven to be a suitable technological option to build such optical devices. Moreover, further improvement of the reflectivity of these multilayers, mainly limited by interface roughness, may be achieved by ion-implantation (e.g., argon or oxygen) [42,44] which tends to smooth the layer boundaries.…”

Section: Multilayered Materialsmentioning

confidence: 99%

Positron depth profiling in solid surface layers

Grynszpan¹,

Anwand²,

Bräuer³

et al. 2007

Ann. Chim. Sci. Mat.

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-We briefly review the principles of the Doppler Broadening of the positron annihilation radiation line, the most common technique used in defect depth profiling of solids relevant to dcbeams. We focus on some specific examples of Slow Positron Implantation Spectroscopy (SPIS) investigations related to technological issues such as, for instance, i) phase transitions in metal coatings possibly induced by internal stresses, ii) substrate pre-treatment or annealing dependence of defect profiles at metal/polymer interfaces or in the deposited layers, and. iii) near-surface structural modification by ion implantation in ceramics and multilayers. In each case we elaborate on the possibility of using SPIS results and possible depth profile features as criteria for on-or off-line quality control in industrial processes. We finally conclude with an overall picture of the operating characteristics of positron annihilation techniques.Résumé -Profils d'implantation des positons dans des couches de surface des solides. Nous passons brièvement en revue les principes de la méthode de l'élargissement Doppler de la raie d'annihilation des positons, technique la plus fréquemment utilisée en analyse de surface des solides par faisceau à courant continu. Nous considérons quelques d'applications technologiques de la caractérisation par spectroscopie d'implantation des positrons lents (SPIS), telles que, par exemple, i) les transitions de phases éventuellement induites par contraintes internes dans les dépôts métalliques, ii) l'influence de prétraitements du substrat ou de recuits sur le profil des défauts aux interfaces métal/polymère ou dans des couches déposées, et iii) la modification structurale par implantation ionique en proche surface de céramiques et de multicouches. Dans tous les cas nous envisageons l'éventualité d'utiliser la technique SPIS et les particularités des profils de défauts comme critères dans des contrôles de qualité en ligne ou en post-production industrielle. Enfin, nous concluons par un panorama des caractéristiques de mise en oeuvre des techniques de spectroscopie d'annihilation des positrons.

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Smoothing of interfaces in ultrathin Mo/Si multilayers by ion bombardment

Cited by 19 publications

References 12 publications

Large area smoothing of surfaces by ion bombardment: fundamentals and applications

Large area smoothing of surfaces by ion bombardment: fundamentals and applications

Specific aspects of roughness and interface diffusion in non-periodic Mo/Si multilayers

Positron depth profiling in solid surface layers

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