Journal of large-scale research facilities, 2, A50 (2016) http://dx.doi.org/10.17815/jlsrf-2-72 Published: 23.02.2016 The At-Wavelength Metrology Facility at BESSY-II Helmholtz-Zentrum Berlin für Materialien und Energie * Instrument Scientists: - Dr. Franz Schäfers, Helmholtz-Zentrum Berlin für Materialien und Energie, phone: +49 30 8062-12946; email: franz.schaefers@helmholtz-berlin.de - Dr. Andrey Sokolov, Helmholtz-Zentrum Berlin für Materialien und Energie, phone: +49 30 8062-12986, email: andrey.sokolov@helmholtz-berlin.de Abstract: The At-Wavelength Metrology Facility at BESSY II is dedicated to short-term characteri- zation of novel UV, EUV and XUV optical elements, such as di�raction gratings, mirrors, multilayers and nano-optical devices like re�ection zone plates. It consists of an Optics Beamline PM-1 and a Re- �ectometer in a clean-room hutch as a �xed end station. The bending magnet Beamline is a Plane Grating Monochromator beamline (c-PGM) equipped with an SX700 monochromator. The beamline is specially tailored for e�cient high-order suppression and stray light reduction. The versatile 11-axes UHV-Re�ectometer can house life-sized optical elements, which are fully adjustable and of which the re�ection properties can be measured in the full incidence angular range as well as in the full azimuthal angular range to determine polarization properties. 1 Introduction The At-Wavelength Metrology Facility (Schäfers et al., 2016) consists of an Optics Beamline PM-1 (Sokolov et al., 2014) and a Re�ectometer (Eggenstein et al., 2014, 2013) as a �xed end station in a clean- room surrounding. It is dedicated to at-wavelength characterization and calibration of the in-house produced di�raction gratings and nano-optical devices as well as of mirrors and multilayer systems. It is coupled to a versatile 4-circle UHV-Re�ectometer as a permanent end station which is located in a moderate clean-room hutch and which allows to carry out Re�ectometry experiments on a very high precision level. The Plane Grating Monochromator beamline attached to a bending magnet is oper- ated in collimated light (c-PGM) (Follath, 2001). The SX700 monochromator is equipped by new blazed *Cite article as: Helmholtz-Zentrum Berlin für Materialien und Energie. (2016). The At-Wavelength Metrology Facility at BESSY-II. Journal of large-scale research facilities, 2, A50. http://dx.doi.org/10.17815/jlsrf-2-72 1 http://jlsrf.org/ http://dx.doi.org/10.17815/jlsrf-2-72 http://dx.doi.org/10.17815/jlsrf-2-72 https://creativecommons.org/licenses/by/4.0/ Journal of large-scale research facilities, 2, A50 (2016) http://dx.doi.org/10.17815/jlsrf-2-72 gratings of our own production. The beamline is matched to re�ectometry requirements: Over the large operating range from 10 to 2000 eV this bending magnet beamline has very high spectral purity achieved by (1) a four-mirror arrangement of di�erent coatings which can be inserted into the beam path at di�erent angles and (2) by absorber �lters for high order suppression. Stray light and scattered radiation is removed e�ciently by in-situ exchangeable apertures and slits. The incident beam has a low divergence and a moderate energy resolution. The main feature of the 11-axes Re�ectometer is the possibility to incorporate large samples (up to 4 kg and 360 mm in length) into the UHV-chamber. The samples are adjustable within six degrees of freedom by a novel compact UHV-tripod system. The re�ectivity can be measured in the full incidence angular range of 90° for both s- and p-polarization geometry by azimuthal rotation of the sample around the beam direction. A variety of in-situ exchangeable detectors with di�erent angular resolution and dynamic range are available. 2 Instrument Applications • At Wavelength metrology (quality control) of UV, EUV and XUV-optics: Multilayers, mirrors, gratings, zoneplates, crystals, thin �lms • Re�ectivity, e�ciency, transmission, di�raction • Scattering (specular - non specular) • Non-destructive investigation and characterisation of optical surfaces • In depth analysis of internal material structure including buried layers and interfaces • Optical constants derived from accurate re�ectivity measurements 3 Source The source is the bending magnet D1.1 with the following parameters: Electron energy [GeV] 1.7 Magnetic �eld [T] 1.3 Bending radius [m] 4.35 Power on 1st optical element (300 mA) [W] 20 Critical energy [keV] 2.5 Source horizontal size (σx) [µ m] 50 vertical size (σy) [µ m] 40 Source hor. divergence (σ ′x) [µ rad] 130 vert. divergence (σ ′y) [µ rad] 2 Table 1: BESSY II source characteristics of the dipole section DIP 1.1 4 Optics Beamline PM-1: Optical Design The optical layout of the beamline is described in in Figure 1. M1 is a toroidal mirror which colli- mates the light vertically and focusses it approximately 1:1 horizontally. The plane mirror M2 is used to vary the deviation angle at the plane grating PG (SX700 monochromator with 600 and 1200 l/mm, respectively (Schäfers et al., 2016). Vertically, the di�racted light is focused onto the exit slit by the cylindrical mirror M3. The subsequent astigmatic refocusing of horizontal and vertical focus onto the 2 http://dx.doi.org/10.17815/jlsrf-2-72 https://creativecommons.org/licenses/by/4.0/ http://dx.doi.org/10.17815/jlsrf-2-72 Journal of large-scale research facilities, 2, A50 (2016) sample position in the re�ectometer is performed by the toroidal mirror M4. Two systems for high order suppression provide a wide �exibility for light shaping upstream of the re�ectometer: 1. The high order suppression system (HiOS) is a four mirror system with di�erent coatings which can be inserted into the beam under selectable incidence angles to freely determine the high- energy cut-o�. 2. The Filter and Slit Unit (FSU) houses a set of 12 absorber �lters and slits and pinholes of di�erent sizes upstream and downstream the �lters for beam shaping and stray light reduction. Figure 1: Optical layout of beamline PM-1 with Re�ectometer end station 5 Beamline all-over Performance Data Location Section DIP 1.1 Source Dipole Monochromator (gratings) SX700 (600 l/mm, 1200 l/mm) Energy range 10 eV - 2000 eV Energy resolution E/∆E= 1000 - 10000 Flux 1010 - 1011 photons/s/100 mA Polarization horizontal-linear, elliptical Divergence horizontal 3.5 mrad Divergence vertical 0.5 mrad Focus size (hor. x vert.) 0.2 x 0.15 mm2 Fixed end station 4-circle UHV-Re�ectometer Absorption �lters Mg, Al, Be, B, C6H8, Ti, Cr, Fe, Cu HiOS mirrors coatings Si, AlF3, C Table 2: Performance data of Optics Beamline PM-1 3 http://dx.doi.org/10.17815/jlsrf-2-72 https://creativecommons.org/licenses/by/4.0/ Journal of large-scale research facilities, 2, A50 (2016) http://dx.doi.org/10.17815/jlsrf-2-72 Figure 2: Photon �ux at the sample position in the re�ectometer, normalized to 100 mA ring current (blue (600 l/mm) and red curve (1200 l/mm)), in comparison with raytrace calculation with RAY (points). Typically BESSY-II runs with 300 mA. 6 Re�ectometer The re�ectometer is coupled permanently to the Optics Beamline as a �xed end station. It is located in a moderate clean-room hutch. The UHV-optical bench comprises a four circle goniometer (two sample circles and two detector circles). The vacuum vessel has a diameter of 1 m and it can handle large samples up to 360 mm length and 4 kg weight. Smaller samples (e.g. wafers) will be mounted via a load lock system without breaking vacuum. Three circles are realized by HUBER-goniometers to set (1) the azimuthal angle Φ (s- or p-polarisation, respectively), (2) the incidence angle Θ and (3) the detector arm 2Θ. For o�-plane sample scans (-4° - +4°) another motorized stage is hooked up onto the 2Θ-goniometer to realize the 4th circle. The six axes sample adjustment and positioning system is based on a compact UHV-tripod system. It allows a two-dimensional scan of the sample surface within a range of approximately +/- 15 mm while maintaining all rotational degrees of freedom within +/- 1°. A pointing stability of this system of better than 50 µ m and 0.025° was reached. A couple of photodiode detectors with and without pinholes or apertures are available. Figure 3: The clean-room hutch at the experimental �oor of BESSY-II with the M4-mirror chamber, the Filter and Slit Unit (FSU) and the Re�ectometer inside (Light comes from the right side). 4 http://dx.doi.org/10.17815/jlsrf-2-72 https://creativecommons.org/licenses/by/4.0/ http://dx.doi.org/10.17815/jlsrf-2-72 Journal of large-scale research facilities, 2, A50 (2016) 7 Re�ectometer all-over Performance Data Monochromator Optics Beamline – PM1 Experiment in vacuum 10−9 mbar Max. sample size 360 x 60 x 60 mm3 Max. sample size for Load-lock 50 x 50 x 10 mm3 Max. sample weight 4 kg Sample surface scan 15 x 15 mm Incidence angle scan range -180° ≤ Θ ≤ 180° Azimuthal angle scan range 0° ≤ Φ ≤ 360° Detector scan range (in plane) -180° ≤ 2Θ ≤180° (o�-plane) -4° ≤ ΘD ≤ 4° Min. step size for all motors 0.001° Sample – Detector Distance 310 mm Detector GaAsP-photodiode with Keithley electrometer 6517B Detector size 4 x 4 mm2, slits or pinholes: 0.14 – 4 mm Table 3: Performance data of the re�ectometer References Eggenstein, F., Bischo�, P., Gaupp, A., Senf, F., Sokolov, A., Zeschke, T., & Schäfers, F. (2014). A re�ectometer for at-wavelength characterization of xuv-re�ection gratings. SPIE Proceedings, 9206, 920607-920607-12. http://dx.doi.org/10.1117/12.2061828 Eggenstein, F., Schäfers, F., Erko, A., Follath, R., Gaupp, A., Löchel, B., . . . Zeschke, T. (2013). A re�ectometer for at-wavelength characterisation of gratings. Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 710, 166 - 171. http://dx.doi.org/10.1016/j.nima.2012.10.132 Follath, R. (2001). The versatility of collimated plane grating monochromators. Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equip- ment, 467 - 468, Part 1, 418 - 425. http://dx.doi.org/10.1016/S0168-9002(01)00338-2 Petersen, H. (1986). The high energy plane grating monochromators at BESSY. Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equip- ment, 246, 260 - 263. http://dx.doi.org/10.1016/0168-9002(86)90086-0 Schäfers, F., Bischo�, P., Eggenstein, F., Erko, A., Gaupp, A., Künstner, S., . . . Zeschke, T. (2016). The at- wavelength metrology facility for UV- and XUV-re�ection and di�raction optics at BESSY-II. Journal of Synchrotron Radiation, 23(1), 67–77. http://dx.doi.org/10.1107/S1600577515020615 Sokolov, A. A., Eggenstein, F., Erko, A., Follath, R., Künstner, S., Mast, M., . . . Schäfers, F. (2014). An XUV optics beamline at BESSY II. SPIE Proceedings, 9206, 92060J-92060J-13. http://dx.doi.org/10.1117/12.2061778 5 http://dx.doi.org/10.17815/jlsrf-2-72 http://dx.doi.org/10.1117/12.2061828 http://dx.doi.org/10.1016/j.nima.2012.10.132 http://dx.doi.org/10.1016/S0168-9002(01)00338-2 http://dx.doi.org/10.1016/0168-9002(86)90086-0 http://dx.doi.org/10.1107/S1600577515020615 http://dx.doi.org/10.1117/12.2061778 https://creativecommons.org/licenses/by/4.0/ Introduction Instrument Applications Source Optics Beamline PM-1: Optical Design Beamline all-over Performance Data Reflectometer Reflectometer all-over Performance Data