Compact Storage Ring FEL: a kW- scale EUV lithography source

TM

…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

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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


https://www-ssrl.slac.stanford.edu/content/about-ssrl/about-stanford-synchrotron-radiation-lightsource

Stanford Synchrotron Radiation Lightsource

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Compact EUV Source Architecture


• 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

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Compact EUV Source: Animation


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


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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®


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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


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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


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Undulator Optics (new idea!)


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

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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


100m

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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


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Regen Amplifier efficiency – one ring

Sync. Rad.

EUVBeam


Undulator Power P0

Gain g

Optics efficiency e

Recyclefraction r



• 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


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Better Way – Double Storage Ring / One Regen

Sync. Rad.

EUVBeam


Undulator Power P0

Gain « gOptics eff. e

Recycle r



• 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


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How Does The “New” kW-scale Source Look Like?


• 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


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

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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


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


TM

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… and wafers !


Compact Storage Ring FEL: a kW- scale EUV lithography source

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