Optical Characterization of Compound Refractive Lenses

Transcription

1 Optical Characterization of Compound Refractive Lenses ARNDT LAST, INSTITUTE OF MICROSTRUCTURE TECHNOLOGY (IMT) CRL Layout 1357_00_A0 KIT University of the State of Baden-Wuerttemberg and National Research Center of the Helmholtz Association

2 Overview Types of Compound Refractive X-ray Lenses (CRLs) at KIT/IMT Characterization of CRLs at KIT with visible light with X-rays Outlook 2 Arndt Last,

3 Types of CRLs Made by deep X-ray lithography at KIT/IMT/ANKA Lens material: SU-8 / mr-l Apertures up to: 1.5 mm Best energy range: monochromatic, >9 kev Resolution achieved in full field microscopy: 180 nm/(line & space) Focal length in the cm range possible a) HH-type b) HHVV-type c) HVHV-type d) hvhvh-type a) line focus; b) point focus, astigmatic; c) point focus, less astigmatic; d) point focus, scarcely astigmatic 3 Arndt Last,

4 CRLs exposed under 45 detail HHVV-CRL layout Customized 16 CRL plate 4 Arndt Last,

5 CRLs exposed under 45 Exposure with a bent mask (bent 50 µm over 70 mm mask length, 2 µm thick Ti!): Under 45 : curved row reduced aperture and FoV Under 90 : straight row full aperture, easy to align 5 Arndt Last,

6 CRLs mounted under 90 Strictly linearly arranged elements Scarcely astigmatic Mouldable sawing separating SEM: mounted 6 Arndt Last,

7 CRLs exposed and mounted under 90 Comparing alignment: 45 -CRL 90 -CRL 7 Arndt Last,

8 CRLs: Objective lenses Constant aperture 8 Arndt Last, Variable aperture Simulated image intensity

9 Characterizing CRLs SEM Visible light X-rays X-ray absorber masks Resist height Linear arrangement of lens elements Severe deformations of parabola Refractive index of lens material X-ray optical lens properties 9 Arndt Last,

10 Characterizing CRLs in visible light microscope Measuring linearity of lens arrangement in a row: useful to judge the accessible aperture of the CRL bending of rows is less important for variable aperture CRLs Linearity deviations 10 Arndt Last,

11 Characterizing CRLs in visible light microscope Measuring the parabolic shape of the refracting surfaces: useful to check for strong deviations from the parabolic shape not useable to control focal length: microscopes tolerance in the 0.5 µm range has to be multiplied with many surfaces! Microscope image of a CRL element 11 Arndt Last,

12 Refractive index decrement of mr-l Measuring beam deflection after a row of mr-l-prisms at ANKA-TOTO 100 µm slit 138 prisms along 18 mm D detector Calculating the refractive index decrement δ from D Measured at photon energies: 10, 13, 15, 17, 21, 25, 30, 40 kev D Detector image: direct beam at top 12 Arndt Last,

13 Refractive index decrement of mr-l Refractive index decrement [ ] Fitted curve (tolerance <2%): Photon energy [kev] 0, : Arndt Last,

14 Investigation of side wall angle Shadow projection of a 10 µm-period grating, illuminated by a line focus source: Detector 10 µm-grating Assumed position of line focus Line focus-crl 14 Arndt Last,

15 Investigation of side wall angle Shadow projection of a 10 µm-period grating, illuminated by a line focus source: Grating near source: lines fan-shaped Grating far from source: lines nearly parallel 15 Arndt Last,

16 Investigation of side wall angle Shadow projection of a 10 µm-period grating, illuminated by a line focus source: Result: LIGA-side walls show 1.2 µm ± 0.3 µm offset over 400 µm resist height (wider at substrate side) detector 10 µm-grating Real position of line focus Line focus CRL 16 Arndt Last,

17 CRLs mounted under 90 Consequences: Focal length shorter close to substrate Astigmatism diagonal over the aperture Half lenses have to be aligned symmetrically Simulations show astigmatism-limited focal spot size of about 60 to 80 nm Disadvantageous arrangement of the half lenses More appropriate arrangement of the half lenses 17 Arndt Last,

18 Outlook Characterization of CRLs requires beam time at synchrotron sources Technical improvement by understanding CRL s shortcomings Is there a need for disposal CRLs at XFELs? Test our lenses! Apply via Start a scientific cooperation Or just order one Acknowledgements: These results have been made possible with the support of KNMF, ANKA-TOTO, VI-NXMM and staff of KIT/IMT and KIT/IPS. 18 Arndt Last,