Reduction of interlayer thickness by low-temperature deposition of Mo/Si multilayer mirrors for X-ray reflection

Rooij-Lohmann, V.I.T.A. de; Yakshin, Andrey; Zoethout, E.; Verhoeven, J.; Bijkerk, Frederik

doi:10.1016/j.apsusc.2011.02.054

Cited by 19 publications

(12 citation statements)

References 17 publications

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“…48,49 For instance, as deposited magnetron sputtered amorphous NbSi thin films exhibited about 11.5% of Si surface segregation when comparing surface (or near-surface) Si concentration to bulk Si concentration. 48 The surface segregation effect for the Ru-on-Si system could be explained by simple thermodynamics when considering the difference in standard surface free energy γ o between Si and Ru surfaces (γ 50 .…”

Section: Surface Coverages Closed Layer Determination and In-deptmentioning

confidence: 99%

In vacuo growth studies of Ru thin films on Si, SiN, and SiO2 by high-sensitivity low energy ion scattering

Ribera

Kruijs

Sturm

et al. 2016

Journal of Applied Physics

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In vacuo high-sensitivity low energy ion scattering (HS-LEIS) has been used to investigate the initial growth stages of DC sputtered Ru on top of Si, SiN and SiO2. The high surface sensitivity of this technique allowed an accurate determination of surface coverages and thicknesses required for closing the Ru layer on all three substrates. The Ru layer closes (100% Ru surface signal) at about 2.0, 3.2 and 4.7 nm on top of SiO2, SiN and Si, respectively. In-depth Ru concentration profiles can be reconstructed from the Ru surface coverages when considering an error function like model. The large intermixing (4.7 nm) for the Ru-on-Si system is compared to the reverse system (Si-on-Ru), where only 0.9 nm intermixing occurs. The difference is predominantly explained by the strong Si surface segregation that is observed for Ru-on-Si. This surface segregation effect is also observed for Ru-on-SiN, but is absent for Ruon-SiO2. For this last system, in vacuo HS-LEIS analysis revealed surface oxygen directly after deposition, which suggests an oxygen surface segregation effect for Ru-on-SiO2. In vacuo XPS measurements confirmed this hypothesis based on the reaction of Ru with oxygen from the SiO2, followed by oxygen surface segregation.

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Section: Surface Coverages Closed Layer Determination and In-deptmentioning

confidence: 99%

In vacuo growth studies of Ru thin films on Si, SiN, and SiO2 by high-sensitivity low energy ion scattering

Ribera

Kruijs

Sturm

et al. 2016

Journal of Applied Physics

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“…Low-temperature deposition was found to reduce intermixing of Mo and Si layers, but resulted in very rough interfaces [10]. Control of adatom mobility by variation of sputtering gas pressure [9,11], which affects the energy of deposited particles, seems the most promising route to kinetic control.…”

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confidence: 99%

Ultra-high efficiency multilayer blazed gratings through deposition kinetic control

et al. 2012

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Diffraction efficiency of multilayer coated blazed gratings (MBG) strongly depends on the perfection of the saw-toothshaped layers in the overall composite structure. Growth of multilayers on saw-tooth substrates should be carefully optimized in order to reduce groove profile distortion and at the same time to avoid significant roughening of multilayer interfaces. In this work we report on a new way to optimize growth of sputter-deposited Mo/Si multilayers on saw-tooth substrates through variation of the sputtering gas pressure. A new record for diffraction efficiency of 44% was achieved for a optimized MBG with groove density of 5250 lines/mm at the wavelength of 13.1 nm. © 2010 Optical Society of America OSIS codes: 050.1950, 120.6660, 340.7480, 230.4170, 310.1860 High efficiency diffraction gratings with high groove density are of great importance for a wide range of extreme ultraviolet (EUV) and soft x-ray applications including EUV lithography [1], astrophysics and solar science [2], and high-resolution Resonance Inelastic X-ray Scattering [3]. Multilayer-coated Blazed Gratings (MBG) can offer vastly improved performance over conventional single layer-coated gratings provided that the grating fabrication process can ensure coherent addition of each layer in the multilayer stack. The main technological challenges are fabrication of nano-period saw-tooth substrates with a perfect groove profile and an atomically smooth surface of blazed facets, and deposition of a multilayer (ML) on the highly corrugated surface of the substrates. Recent progress in fabrication of saw-tooth gratings with anisotropic etching of silicon single crystals [4,5] provided the necessary quality of the substrates [6]. The main remaining problem however is coherent replication of this structure from the substrate throughout the whole multilayer stack.Simulation of the diffraction efficiency shows that smoothening of the saw-tooth substrate by a ML deposited on it is a main limiting factor for MBG performance. Traditional deposition techniques optimized for growth of the MLs on flat substrates aim to provide interfaces of a ML stack as smooth as possible via promotion of surface relaxation processes. However, this approach does not work well for the highly corrugated surface of saw-tooth substrates, because a triangular shaped groove suffers greatly from excessive diffusion mobility of deposited atoms, caused in particular by bombardment of growing surface with energetic particles. The mobility provides effective smoothening of random roughness of interfaces, but in the same manner affects the high-frequency harmonics of a Fourier spectrum of a saw-tooth surface, causing degradation of the initial groove profile in the course the ML deposition [7,8]. As a result of this, a MBG loses its blazing ability and diffraction efficiency can be substantially reduced compared to the theoretical maximum.To avoid groove degradation one should reduce the adatom mobility. However, too low a surface mobility would result in rough interfaces and incre...

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“…The peak reflectivity of a multilayer mirror is critically dependent on the quality of each layer and interface in the stack [5][6][7]. Formation of continuous and smooth layers is important for achieving good optical performance of multilayer optics.…”

Section: Introductionmentioning

confidence: 99%

Evolution of interfacial structure of Co-based periodic multilayers upon annealing

Yuan

Guen

Mény

et al. 2018

Surface and Coatings Technology

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Reduction of interlayer thickness by low-temperature deposition of Mo/Si multilayer mirrors for X-ray reflection

Cited by 19 publications

References 17 publications

In vacuo growth studies of Ru thin films on Si, SiN, and SiO2 by high-sensitivity low energy ion scattering

In vacuo growth studies of Ru thin films on Si, SiN, and SiO2 by high-sensitivity low energy ion scattering

Ultra-high efficiency multilayer blazed gratings through deposition kinetic control

Evolution of interfacial structure of Co-based periodic multilayers upon annealing

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