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…and wafers
Compact Storage Ring FEL: a kW-scale EUV lithography source5th EUV-FEL Workshop – 22 Jan 2021Dr. Rod Loewen
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Lyncean Technologies, Inc.
Our Mission: Provide industry and academia with accelerator-based compact photon sources and customer solutions to meet their most demanding application needs
Lyncean Confidential
Founded in 2002 as a spin-off of SLAC by Prof. Ron Ruth, Dr. Rod Loewen and Jeff Rifkin
3
Best Road to kW-scale EUV – LPP or FEL?
Lyncean believes an accelerator-based source is the best road to kW-scale • No contaminant generated• Reliable
• No moving parts, no consumables• Synchrotron facilities achieve >95% uptime
• Polarized EUV• Linear, able to manipulate
• High efficiency• Better wall plug power efficiency than LPP
• Narrower bandwidth• Optically more efficient
Lyncean Confidential
https://www-ssrl.slac.stanford.edu/content/about-ssrl/about-stanford-synchrotron-radiation-lightsource
Stanford Synchrotron Radiation Lightsource
4
Compact EUV Source Architecture
Lyncean Confidential
• EUV Generation• Via coherent emission as
electrons pass through the undulator
• Regenerative Amplification• A portion of the EUV beam
is returned to the undulator (self-seeding)
• Increases gain in a short undulator
• Remainder of EUV beam exits source• Transport optics conditions
beam and transports it to the scanner
Undulator Segments
Regenerative amplifier
13.5nm EUV BeamTo transport optics
Folded LINAC
Transport
Electron Gun
Damping wigglers
RF structures
5
Compact EUV Source: Animation
Lyncean Confidential
Electron bunchNo interactionCoherent emissionCoolingEnergy replenished
One electron bunch shown for illustration, multiple bunches in full implementation
EUV beam EUV to transport optics
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EUV FEL inside Storage Ring? Idea is catching on
Pohang’s “demonstration” design is way too big
… but LTI knows how to do it in a space efficient way
Lyncean Confidential
7
Single page derivation of FEL in a storage ring
• The FEL induces an additional energy spread in the electron beam• 𝛥(𝜎!
")#$% ≈" &!"#c
'!"#'$"%&
where c = 1 (1D case) but in general < 1 (3D cases)
• This is a diffusion term, or heating, that is offset by radiation damping• ()'
(
(*= − ")'
(
+'+ ")')
(
+'+
,()'()!"#
/*"+; first term is cooling, second is quantum excitation
• The energy spread will increase and saturate at (solve previous eq)• 𝜎!
" = 𝜎!0" + +'
"/*"+𝛥(𝜎!
")#$% ≅+'
"/*"+𝛥(𝜎!
")#$% where second term dominates
• Using the relationship for FEL power vs energy spread increase:• 𝑃#$%= 𝜎!
" c" &!"#
𝑃1$23"/*"++'
or 𝑃#$% = 𝜎!" c&!"#
𝑃45
Synchrotron Radiation Power®
Lyncean Confidential
8
𝑃!"# = 𝜎$% c𝜌!"#
𝑃&'
FEL Physics terms Pohang CES
(Energy spread)2 𝜎$% (0.20%)2 (0.50%)2
Pierce parameter 𝜌!"# 1.5e-3 1.5e-3
Efficiency of energy extraction (ideal=1)
c ~0.75 0.50-0.55
FEL component𝜎$% c𝜌!"#
2.0e-3 8.7e-3
Synch. Rad. Pohang (kW) CES (kW)
Arc bends 𝑃( 137* 94
Undulator 𝑃) 383 10
Damping Wigglers
𝑃* 0 171
Synchrotron Power (sum)
𝑃&' 520 275
*bends 343kV*400mA = 137 kW
Pohang ® 2.0e-3*520kW = 1.0 kW Lyncean ® 8.7e-3*275kW = 2.4 kW but some is recycled for seeding
𝜎$% c𝜌!"#
𝑃&'Synchrotron Radiation
Storage Ring FEL Physics & Engineering
Lyncean Confidential
9
Lyncean’s Key Differentiators / Innovations
1. Undulator with optics maintain gain & power with large energy spread• Normally FELs designed with constraint sd< rfel (~1.5e-3 for EUV/X-ray) for gain• Large energy spread dramatically increases the “physics term” in storage ring FEL• Then “engineering term” or synchrotron power is manageable
2. A short undulator as a regenerative amplifier to make it compact• Self seeding requires many gain lengths• Linear accelerators unwrap laser into single path – space inefficient• Multi-pass resonant amplifier uses previous seed power until equilibrium
Lyncean Confidential
10
Undulator Optics (new idea!)
Lyncean Confidential
Focusing
Energy dependentpath length (slippage) Insertion cell tests
0.45% dE/E
GenesisUse Genesis to optimize gain for large energy spread
Then find optical implementations (MAD)
maintainsbunchingif near 0
Electron beam optics+ EUV GI mirrors
Peak Power and Gain
11
Lyncean’s Key Differentiators / Innovations
1. Undulator with optics maintain gain & power with large energy spread• Normally FELs designed with constraint sd< rfel (~1.5e-3 for EUV/X-ray) for gain• Large energy spread dramatically increases the “physics term” in storage ring FEL• Then “engineering term” or synchrotron power is manageable
2. A short undulator as a regenerative amplifier to make it compact• Self seeding requires many gain lengths• Linear accelerators unwrap laser into single path – space inefficient• Multi-pass resonant amplifier uses previous seed power until equilibrium
Lyncean Confidential
100m
12
Regenerative Amplifier efficiency
Sync. Rad.
EUVBeam
delivery To scanner P0(1-r) h
Undulator Power P0
Gain g
Optics efficiency e
Recyclefraction r
Output power P0(1-r)
Delivery efficiency h
Condition for steady-stateP0 = (rP0 )(e)(g) or (r)(e)(g)=1 ® r = 1/[(e)(g)]
Seed Power
• We design for P0
• We budget for h• We find r from steady-state
FEL gain
EUV optics
Lyncean Confidential
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Regen Amplifier efficiency – one ring
Sync. Rad.
EUVBeam
delivery To scanner P0(1-r) h
Undulator Power P0
Gain g
Optics efficiency e
Recyclefraction r
Output power P0(1-r)
Delivery efficiency h
• P0 = 4.0 kW• h = 0.50• e = 0.10 ¬ 360 deg of optic losses• g = 20• r = 1/[(e)(g)] = 0.50
To scanner P0(1-r) h = 1.0 kWEngineerable solution in principle, but• 450 kW of synchrotron radiation required• Larger than what we target
Lyncean Confidential
14
Better Way – Double Storage Ring / One Regen
Sync. Rad.
EUVBeam
delivery To scanner P0(1-r) h
Undulator Power P0
Gain « gOptics eff. e
Recycle r
Output power P0(1-r)
Delivery efficiency h
• P0 = 2.4 kW• h = 0.50• e = 0.30 ¬ Only 180 deg!• g = 20• r = 1/[(e)(g)] = 0.17
To scanner P0(1-r) h = 1.0 kWSync. Rad.
EUV
Undulator Power P0
r
e
Precedence exists: SLAC PEP-II two independent storage rings
Approach: Keep size the same, but use two rings working together to get two 2kW Output Power EUV beams
Lyncean Confidential
15
How Does The “New” kW-scale Source Look Like?
Lyncean Confidential
• Two sources work together• Regen for each source is 180˚ bend • Efficiency is improved to 30%
• Two 2.0 kW EUV beams are produced• Improved cost efficiency
• Two sources share the same injector and regen• Two sources share the same enclosure
• Improved footprint efficiency• Two sources and injector can be stacked
2.0 kW to transport
optics
Single pass regen efficiency – 30%
Single pass regen efficiency – 30%
2.0 kW to transport
optics
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Beam delivery concept
Lyncean Confidential
CES 34m x 3.5m
Scanner 13.3m x 3mScanner 13.3m x 3m
6m
6mMLML
SGI SGI
DefocusingK-B mirrors0.5 deg incidence
Polarization Control3 GI mirrors
45 deg arc usingsegmented GI arrayRu-coated Si
Double SourceHigh NA Scanner ASML/Zeiss know how to do beam delivery
17
EUV Source Product Development Status
Subsystem Physics Engineering Prototype Parts / Test
Status
Electron Gun and Accelerator
Electron gun built & tested (gamma-ray project)Accelerator components built; assembly Q1 & Q2 (gamma-ray project)
Multi-bend AchromatElectron Storage Ring
Engineering completedComponents being built (gamma-ray project)
EUV Light Regenerative Amplifier Optical System
ZEISS prototype GI mirrors met specsCooling system engineering & prototype needs to be completed
Undulator / Undulator Optics Concept & modeling completedFundraising to complete engineering and begin construction of a prototype
Lyncean Confidential
Brazed accelerator structure
Regen GI mirror surface error < 0.5 nm RMS
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Summary
• A compact storage ring FEL design was presented that generates kW-scale EUV power• The power generated by the FEL is a function of the energy spread,
undulator efficiency and the storage ring radiation damping• Undulator optics allow the required gain to be achieved with large energy
spread• A regenerative amplifier was incorporated to keep the undulator compact• A 2-beam source was presented that reduces cost/kW and makes more
efficient use of space• Polarization control can be incorporated in the beam delivery system
Lyncean Confidential
TM
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… and wafers !
Lyncean Confidential