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MLL fabrication R&D Status. Ray Conley EFAC Review: April 23 rd , 2009. Collaborators. Brookhaven National Laboratory Nathalie Bouet (deposition, equipment, multilayer sectioning) Jimmy Biancarosa (technical) Qun Shen, Hanfei Yan (diffraction theory) Yong Chu (HXN beamline) - PowerPoint PPT Presentation
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1 BROOKHAVEN SCIENCE ASSOCIATES
MLL fabrication R&D Status
Ray ConleyEFAC Review: April 23rd, 2009
2 BROOKHAVEN SCIENCE ASSOCIATES
• 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)
Collaborators
3 BROOKHAVEN SCIENCE ASSOCIATES
Multilayer Laue lens:
Many thousands of depth-graded layers according to Fresnel zone plate law
Fabricate cross-sections for use in Laue geometry
4)(
22
02 n
zfnrn
Multilayer Laue Lens Overview
Flat Wedged Tilted
4 BROOKHAVEN SCIENCE ASSOCIATES
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 ~100m total film growths in one coating run, without plasma
perturbation events.
5 BROOKHAVEN SCIENCE ASSOCIATES
State of the Art and Current Activities
• MLL achievements at APS• Reflective multilayers with sub 1nm layers grown• 5nm tilted half-structure sectioned (dicing/polishing)• RIE effort started• 40m(!) 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)
Meas. data
10-7
10-6
10-5
10-4
10-3
10-2
10-1
100
-0.1000 4.9000 9.9000 14.9000 19.9000
REFLECTIVITY PROFILE
2theta angle (deg.)
Refle
ctiv
ity (
a.u
.)
•400 bilayers of WSi2 and Si•WSi2 =7.2 Å, Si = 30.8Å•Roughness~2.5 Å
Conley et. al., SPIE 6705, 670505 2007.
6 BROOKHAVEN SCIENCE ASSOCIATES
0
0.05
0.1
0.15
-20 -15 -10 -5 0 5 10 15 20
Full Structure ~40m total growth in 2 parts (4nm outermost zones)
Start of 1st deposition
End of 2nd deposition
End of 1st deposition / Start of 2nd deposition
Inve
rse
d-s
pa
cin
g
(1/n
m)
Position (m)
End of SEM data
Through the middle growth
Current status:5,165 layers grown56 hour deposition per half, WSi2 central zone40 m total growth, 4 nm outermost zonesNo attempt was made for stress reduction14 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 BROOKHAVEN SCIENCE ASSOCIATES
Wedged MLL growthZP6-2 line profile
4/5/07
0.04
0.06
0.08
0.1
0.12
0.14
1 2 3 4 5Layer Position (microns)
Inve
rse
d-sp
acin
g (1
/nm
)
r~13 nm r~3 nm
Mag = 16,500 X10kV1m
Normalized intensity contours (isophotes) in the focus region, simulated for a single blade (f=2.6mm), 30m 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 BROOKHAVEN SCIENCE ASSOCIATES
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
1. Grow 1st half of wedged MLL, and most of the central zone
2. 2. Grow compensation gradient 90 ° opposed to main wedge
3. 3. Grow 2nd half of wedged MLL
~20mm Target the required central zone thickness less 30nm
Gradient from 0 to 60nm over 20mm of substrate width
With a 100m horizontal acceptance, the variation is only +/-1.5 Å, satisfying the placement requirement
9 BROOKHAVEN SCIENCE ASSOCIATES
Structure Stress (MPa)
10nm, 12.4m tilted/partial -742.8
5nm, 12.35m tilted/partial -917.6
4nm, 40m flat/full -651.2
3nm, 7m wedged/full -20.8
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 m 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
In-situ film stress measurement & mitigation
-0.20
-0.16
-0.12
-0.08
-0.04
0.00
0 20 40 60 80 100 120
Stress Buildup with original conditions (2.3 mTorr process gas pressure)
-0.20
-0.16
-0.12
-0.08
-0.04
0.00
0 100 200 300 400 500
WSi2-contributes compressive stress
Si-contributes tensile stressChange process
gas pressure several times Settle on 16 mTorr
Stress Mitigation
Negative RoC = compressive stress
10 BROOKHAVEN SCIENCE ASSOCIATES
2 machines for use:CFN:ICP-RIE (plasmalab 100)4-gas Bosch processProposal 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
Early attempt at ICP-RIE etching of WSi2/Si multilayer (MLL)
4th attempt: CF4, Cl2, O2 mixture with sample on Cryotable. Shipley PR for etch-resist.
WSi2 layers
Si layers
Sectioning MLLs with Reactive Ion Etching
Photomask reticle design complete-includes OSA test patterns (Bouet)
Test WSi2/Si structures needed – setup at 703 of borrowed chamber
7-1 aspect ratio
500m wafer
100m mll
15m section
11 BROOKHAVEN SCIENCE ASSOCIATES
NSLSII Deposition Lab Equipment
Woollam Ellipsometer M2000Arrived Sept. 2008470 wavelengths measurement from 245 to 1000nmRemovable focusing optics (300mm)300mm x 300mm XY mapping capabilityAuto tip-tilt, height, angle of incidence, alignment cam
Stylus ProfilerArrived Sept. 2008150mm x 150mm Motorized XY table150mm scan length60+mm sample height accomodation1nm step height repeatability3D scan capability
Clean HoodContract awarded to CleanZones, LLC.Arrives in several weeksISO 4 (former class 10) specification6’ stainless steel constructionquick-dump-rinse basin, ultrasonics
High-Resolution XRRSpecifications released to purchasing8keV tube sourceGobel+4-bounce Ge monochromator100mm x 100mm or greater XY mapping Automatic 2-D scans
Microstitching InterferometerTakacs and Conley deliver head to Zygo 3/5/2009Completed system arrived and commissioned 2 weeks ago!Scanning white light interferometry300mm x 300mm XY mapping<0.1nm vertical resolution, <0.01nm measurement repeatibility
Multi-Beam Optical SensorIn-situ film stress measurement10km radius of curvature sensitivityArrives in 6 weeks
12 BROOKHAVEN SCIENCE ASSOCIATES
• 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
New NSLSII wedged MLL system
Still on-track to grow first BNL multilayer Laue lens in FY09!
13 BROOKHAVEN SCIENCE ASSOCIATES
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
New NSLSII wedged MLL systemLinear motor and transport system
Plan to test magnetic flux disruption and coupling for linear motor + magnetron scheme.
If a problem is found, shielding should help
14 BROOKHAVEN SCIENCE ASSOCIATES
FY09 Work plans
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!
F=1mm at 20keV3,835 layers1.98nm outmost layers, 16nm innermost layersTotal thickness=13.4m
15 BROOKHAVEN SCIENCE ASSOCIATES
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 BROOKHAVEN SCIENCE ASSOCIATES
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 BROOKHAVEN SCIENCE ASSOCIATES
1nm R&D Status (Theory & Test)
Hanfei Yan, NSLS-II EFAC Review: April 23rd, 2009
18 BROOKHAVEN SCIENCE ASSOCIATES
Challenges in theory and experiment
TheoryFull-wave dynamical model Effects of imperfections
Placement error Interdiffusion Roughness
Lens characterization Focus measurement by fluorescence (direct) Phase retrieval method (indirect)
o Mechanical design (NSLS-II)oSub-nano stability oSmall working distance and many degrees of
freedom
Solved Underwayo Not started
19 BROOKHAVEN SCIENCE ASSOCIATES
Roughness modeling
Theoretical models are developed for MLLs
Roughness factor:
H. Yan, Phys. Rev. B 79, 165410 (2009)
)exp()exp( uρhiM h
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.
Dynamical diffraction modeling
• 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.
H. Yan, et al, Phys. Rev. B 76, 115438 (2007)
1nm wMLL; half structure
20 BROOKHAVEN SCIENCE ASSOCIATES
2-D focusing by two crossed MLL’s
2 translations + 1 rotation 3 translations + 2 rotations
~millimeters
Engineering challenges!
Incoming x-rays
Focus
Ultimately we want to bond two aligned MLLs together to create a single monolithic lens.
For 1-nm wedged MLL at 10 keV, this distance is only 1 mm at most!
21 BROOKHAVEN SCIENCE ASSOCIATES
Simple consideration for misalignment tolerance
0
Perfectly aligned In-plane angle misaligned
E=10 keV, dr=1 nm, r=62 µm, f=1 mm
=0 =0.01
Integrate line scan
We are evaluating the alignment accuracy required.
-30 -20 -10 0 10 20 300.0
0.5
1.0
1.5
2.0
2.5
Inte
nsity
(ar
b. u
nits
)
x (nm)
=0 =0.005 =0.01
22 BROOKHAVEN SCIENCE ASSOCIATES
2-D MLL focusing instrument
[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.
This instrumentation effort is led by Center for Nanoscale Materials
23 BROOKHAVEN SCIENCE ASSOCIATES
“Proof of Principle” Experiment
Two crossed Pt nano-layers
Pt L,,
MLL
Fluorescence detector
X-rays
CCD
45.0 45.5 46.0 46.5 47.0 47.5 48.0
0
500
1000
1500
2000
56 58 60 62 64 66
0
500
1000
1500
2000
2500
Flu
ore
scence
x (m)
x-scan
y-scan
Flu
ore
scence
y (m)
Fluorescence measurement
CCD image (Log scale)
Experiment conducted at sector 26, APS
1. Proof of principle experiment was conducted successfully using the CNM/APS prototype.
2. We are exploring limitations of this device and making improvements.
3. CDI Effort of reconstructing the focus is on going.
24 BROOKHAVEN SCIENCE ASSOCIATES
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
Initial success in reconstructing 60 nm beam at 2-ID-B, APS.
Measured CCD Image (log scale)
y
x
x
z
Reconstruction
25 BROOKHAVEN SCIENCE ASSOCIATES
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.