MLL fabrication R&D Status

1. MLL fabrication R&D Status Ray Conley EFAC Review: April 23rd, 2009

2. Collaborators • Brookhaven National Laboratory • Nathalie Bouet (deposition, equipment, multilayer sectioning) • Jimmy Biancarosa (technical) • Qun Shen, Hanfei Yan (diffraction theory) • Yong Chu (HXN beamline) • Hanfei Yan (theory and experiment) • Myron Strongin (general support) • Mary Carlucci-Dayton (deposition system mechanical design) • Vacheslaw (Slowa) Solovyov (thin-film growth) • Advanced Photon Source, Argonne National Laboratory • Albert Macrander (multilayer fabrication) • Chian Liu (multilayer fabrication) • Nima Jahedi (multilayer sectioning and SEM imaging) • Jun Qian (SEM imaging) • Swiss Light Source • Cameron Kewish (optics theory) • European Synchrotron Radiation Facility • Christian Morawe • Jean-Christophe Peffen • Center for Nanoscale Materials, Argonne National Laboratory • Jörg Maser (diffraction theory) • Brian Stephenson (x-ray measurement) • Ralu Divan (reactive ion etching, lithography) • Department of Advanced Materials Engineering, Chosun University, Republic of Korea • Hyon Chol Kang (lens preparation, x-ray measurement)

3. Multilayer Laue Lens Overview Flat Wedged Tilted Multilayer Laue lens: Many thousands of depth-graded layers according to Fresnel zone plate law Fabricate cross-sections for use in Laue geometry

4. Challenges facing 1nm Fabrication of 1nm outermost zones with minimum interfacial roughness. Maintaining proper zone placement. Wedged layer growth. Through-the-middle growth: Mitigating the changes in growth kinetics and growth rate for thick central zones. Central-zone compensation Film stress reduction. Sectioning MLLs into usable optics. Obtaining ~100mm total film growths in one coating run, without plasma perturbation events.

5. State of the Art and Current Activities • 400 bilayers of WSi2 and Si • WSi2 =7.2 Å, Si = 30.8Å • Roughness~2.5 Å • MLL achievements at APS • Reflective multilayers with sub 1nm layers grown • 5nm tilted half-structure sectioned (dicing/polishing) • RIE effort started • 40mm(!) through the middle MLL • Wedged half-structure MLL (2.5nm outmost zones) • Continue collaboration between APS/NSLS-II • Lab setup is ongoing • Film and surface metrology equipment setup • MLL deposition system design • Pursue alternative sectioning (RIE) Conley et. al., SPIE 6705, 670505 2007.

6. Through the middle growth Full Structure ~40mm total growth in 2 parts (4nm outermost zones) Inverse d-spacing (1/nm) Start of 1st deposition End of 1st deposition / Start of 2nd deposition End of 2nd deposition End of SEM data Position (mm) Current status: 5,165 layers grown 56 hour deposition per half, WSi2 central zone 40 mm total growth, 4 nm outermost zones No attempt was made for stress reduction 14 SEM images stitched together + 2 blade fixtures instead of 4 for point focus + Energy independent -Flat thru-middle MLL:Lower integrated efficiency relative to tilted or wedged

7. Wedged MLL growth Mag = 16,500 X 10kV 1mm Dr~13 nm Dr~3 nm Normalized intensity contours (isophotes) in the focus region, simulated for a single blade (f=2.6mm), 30mm thick slice of this device, using 82.1keV x-rays. Focus FWHM = 5.5nm, with an efficiency of 36.6%. Remaining 22% of the central zones of the whole MLL structure was not grown and so is not included in the simulation. Energy bandwith = 10%. Conley Et. Al.,“Wedged multilayer Laue lens,” Rev. Sci. Instrum. 79, 053104 (2008)

8. Through the middle growth patent application work in progress: Central Zone Compensation-Successful full MLL structure requirement: outermost zone placement accuracy of ~1/3 the thickness of the outermost zones. For 1nm outermost zone structure, this means the last layer must be placed within 3 Å (!) Solution: Incorporate a central zone compensation layer ~20mm • Grow 1st half of wedged MLL, and most of the central zone • 2. Grow compensation gradient 90 ° opposed to main wedge • 3. Grow 2nd half of wedged MLL Target the required central zone thickness less 30nm Gradient from 0 to 60nm over 20mm of substrate width With a 100mm horizontal acceptance, the variation is only +/-1.5 Å, satisfying the placement requirement

9. In-situ film stress measurement & mitigation Extremely thick films can accumulate an extreme amount of stress Multiple paths of failure: -Film delamination during or after growth -Micro-cracking during growth -Added difficulty dicing and thinning MLLs to 5-80 mm width -Need to explore process variation methods to mitigate stress; parameter space afforded by sputtering is extremely large -Thicker total growths may be possible with stress mitigation Grown with modified pressure Stress Buildup with original conditions (2.3 mTorr process gas pressure) Negative RoC = compressive stress Stress Mitigation Si-contributes tensile stress Change process gas pressure several times WSi2-contributes compressive stress Settle on 16 mTorr

10. Sectioning MLLs with Reactive Ion Etching Si layers 4th attempt: CF4, Cl2, O2 mixture with sample on Cryotable. Shipley PR for etch-resist. WSi2 layers 2 machines for use: CFN:ICP-RIE (plasmalab 100) 4-gas Bosch process Proposal accepted; 8 staff days allocated CNM: ICP-RIE (also a plasmalab 100) Chlorine chamber: (Cl2, SF6, BCl3, HBr, CHF3, CO, O2, Ar) Fluorine chamber: (SF6, CF2, CH4, CHF3, HCFC-124, H2, O2, Ar) Rapid-access proposal accepted, Bouet to travel to CNM as scheduling permits RIE Considerations: -100’s of runs needed -Recipe’s will be material specific +Higher aspect ratios +More stable optics +Higher yield 100mm mll 7-1 aspect ratio Early attempt at ICP-RIE etching of WSi2/Si multilayer (MLL) 500mm wafer 15mm section Photomask reticle design complete-includes OSA test patterns (Bouet) Test WSi2/Si structures needed – setup at 703 of borrowed chamber

11. NSLSII Deposition Lab Equipment High-Resolution XRR Specifications released to purchasing 8keV tube source Gobel+4-bounce Ge monochromator 100mm x 100mm or greater XY mapping Automatic 2-D scans Woollam Ellipsometer M2000 Arrived Sept. 2008 470 wavelengths measurement from 245 to 1000nm Removable focusing optics (300mm) 300mm x 300mm XY mapping capability Auto tip-tilt, height, angle of incidence, alignment cam Clean Hood Contract awarded to CleanZones, LLC. Arrives in several weeks ISO 4 (former class 10) specification 6’ stainless steel construction quick-dump-rinse basin, ultrasonics Microstitching Interferometer Takacs and Conley deliver head to Zygo 3/5/2009 Completed system arrived and commissioned 2 weeks ago! Scanning white light interferometry 300mm x 300mm XY mapping <0.1nm vertical resolution, <0.01nm measurement repeatibility Stylus Profiler Arrived Sept. 2008 150mm x 150mm Motorized XY table 150mm scan length 60+mm sample height accomodation 1nm step height repeatability 3D scan capability Multi-Beam Optical Sensor In-situ film stress measurement 10km radius of curvature sensitivity Arrives in 6 weeks

12. New NSLSII wedged MLL system Still on-track to grow first BNL multilayer Laue lens in FY09! • Chamber size: ~22’ long x ~14” dia. • Quad cryopumped with variable- throttle hivac valves • Pulsed-DC magnetron sputtering • 8 main gun ports • Local dark-space gas injection • Bipolar pulsed-DC supplies • 1 main transport system – linear motor • Liquid-cooled rail • Velocity-profile capable • Substrate biasing • Ion mill port Magnetrons

13. New NSLSII wedged MLL system Linear motor and transport system Linear motor and crossed-roller bearing rail assembly provides the best mechanical and constant-velocity performance characteristics-an essential component for high-quality multilayer deposition High-quality design from CVD includes complete differentially-pumped o-ring seals where necessary, ¼” thick chamber walls, liquid-cooled rail assembly, and granite block isolation for the rail, isolating the rail from any flexing of the chamber while under vacuum or during process Plan to test magnetic flux disruption and coupling for linear motor + magnetron scheme. If a problem is found, shielding should help

14. FY09 Work plans F=1mm at 20keV 3,835 layers 1.98nm outmost layers, 16nm innermost layers Total thickness=13.4mm Work plans ongoing: • Deposition laboratory staffing: • Jimmy Biancarosa (technician) • Nathalie Bouet (RIE sectioning) • GEM student (summer 2009) SEM stitching • M.S. student approved (control systems) • 2nm outmost-zone wedged MLL grown at APS in Oct. • SEM imaging ongoing. • Deposition system drawing approval in a couple weeks • Design of class-10 clean hood completed, award contracted. • Microstitching Interferometer arrived • Ellipsometer, stylus profiler commissioned • Multi-beam optical sensor ordered • High-resolution XRR specifications released • Work permit, PSRFs, ORE completed • Work plans scheduled • Push for completion of 703 cleanrooms • Explore RIE sectioning of periodic structures • Test structure growths ongoing (Bouet, at building 480) • CFN proposal submitted for April run • Rapid-access CNM proposal submitted • Qualify metrology equipment before arrival of deposition system • Grow first BNL multilayer Laue lens in FY09!

15. Timeline 2009 2010 2011 2012 <10nm wedged Wedged and through center Sub-10 nm optics ready for 2D focusing Find material-specific solution for sectioning with RIE

16. Conclusion and Acknowledgements • The challenges for nanofocusing wMLL are known. • We have feasible solutions for these challenges. • Fabrication of the targeted wedged MLL should be achievable on an appropriate timescale for NSLS-II with these resources. • The NSLSII Deposition Laboratory fit-out is underway

17. 1nm R&D Status (Theory & Test) Hanfei Yan, NSLS-II EFAC Review: April 23rd, 2009

18. Challenges in theory and experiment Theory Full-wave dynamical model Effects of imperfections Placement error Interdiffusion Roughness Lens characterization Focus measurement by fluorescence (direct) Phase retrieval method (indirect) Mechanical design (NSLS-II) Sub-nano stability Small working distance and many degrees of freedom • Solved • Underway • Not started

19. Theoretical models are developed for MLLs Roughness modeling Dynamical diffraction modeling Roughness factor: 1nm wMLL; half structure • No hard theoretical limit prevents hard x-rays from being focused to 1-nm by MLL method. • To achieve 1-nm focus with high efficiency, wedged MLL’s are required. Sputtering deposition techniques nowadays can achieve RMS roughness below 0.5 nm, so it is not a limiting factor in practice for achieving 1-nm. H. Yan, et al, Phys. Rev. B 76, 115438 (2007) H. Yan, Phys. Rev. B 79, 165410 (2009)

20. 2-D focusing by two crossed MLL’s Engineering challenges! For 1-nm wedged MLL at 10 keV, this distance is only 1 mm at most! ~millimeters Incoming x-rays Focus 2 translations + 1 rotation 3 translations + 2 rotations Ultimately we want to bond two aligned MLLs together to create a single monolithic lens.

21. Simple consideration for misalignment tolerance Perfectly aligned Integrate line scan In-plane angle misaligned 0  E=10 keV, dr=1 nm, r=62 µm, f=1 mm =0 =0.01 We are evaluating the alignment accuracy required.

22. 2-D MLL focusing instrument This instrumentation effort is led by Center for Nanoscale Materials [1] D. Shu, H. Yan, and J. Maser, to be published in Nucl. Instrum. and Meth. for 15th Pan-American Synchrotron Radiation Instrumentation Conference, Saskatoon, June 10-13, 2008[2] D. Shu, H. Yan, and J. Maser, U.S. Patent application in progress for ANL-IN-07-097.

23. “Proof of Principle” Experiment CCD CCD image (Log scale) Fluorescence detector Pt La,b,g Two crossed Pt nano-layers X-rays MLL Experiment conducted at sector 26, APS Fluorescence measurement • Proof of principle experiment was conducted successfully using the CNM/APS prototype. • We are exploring limitations of this device and making improvements. • CDI Effort of reconstructing the focus is on going.

24. Efforts of Nanofocus Reconstruction by Coherent Diffraction Imaging (Enju Lima) Characterization of a zone plate: dr= 50 nm, D=160 µm, f=14 mm, E=2.185 keV Measured CCD Image (log scale) Reconstruction x y z x Initial success in reconstructing 60 nm beam at 2-ID-B, APS.

25. Summary of Current Status To present all major theoretical problems have been solved. Proof of principle experiment for 2D focus by two MLLs was successfully conducted. CDI effort has been initiated and the first reconstruction has been tried. Continued effort on improving the CNM/APS 2D instrument.