mll fabrication r&d status

1 BROOKHAVEN SCIENCE ASSOCIATES

MLL fabrication R&D Status

Ray ConleyEFAC Review: April 23rd, 2009


• 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


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


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.


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.


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


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)


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


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


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


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


• 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!


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


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


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


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


1nm R&D Status (Theory & Test)

Hanfei Yan, NSLS-II EFAC Review: April 23rd, 2009


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


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


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!


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


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


“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.


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


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.

mll fabrication r&d status

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