Summary of Japanese Academic Support Program for LPP · PDF fileS. Fujioka, T. Aota, K. Nagai, T. Norimatsu ( Osaka University) S. Uchida, Y. Shimada, M. Yamaura, K. Hashimoto (Institute

EUVL SYMPOSIUM OCT. 16-18, 2006, Barcelona

Yasukazu Izawa, Katsunobu Nishihara, Hiroaki Nishimura, Masahiro Nakatsuka,Takayasu Mochizuki*, Tatsuo Okada**, Shoichi Kubodera***

Noriaki Miyanaga, and Kunioki MIma

Institute of Laser Engineering, Osaka University*Laboratory of Advanced Science and Technology for Industry, University of Hyogo

** Graduate School of Information Science and Electrical Engineering, Kyushu University*** Faculty of Engineering, Miyazaki University

Summary of Japanese Academic Support Programfor LPP EUV Source

2006 International EUVL SymposiumOctober 16 - 18, 2006, Barcelona, Spain

This work was performed under the auspices of Leading Project promoted by MEXT, JAPAN.


Contributors

Theory and simulationH. Tanuma, H. Ohashi (Tokyo Metropolitan University)F. Koike (Kitasato University) K. Fujima (Yamanashi University) R. More, T. Kato (National Institute of Fusion Science)A. Sasaki (Advanced Photon Research Center, JAEA)M. Murakami, Y. -G. Kang ( Osaka University)A. Sunahara, H. Furukawa (Institute for Laser Technology)T. Kagawa (Nara Womens College)T. Nishikawa (Okayama University)

ExperimentsS. Fujioka, T. Aota, K. Nagai, T. Norimatsu ( Osaka University)S. Uchida, Y. Shimada, M. Yamaura, K. Hashimoto (Institute for Laser Technology)S. Miyamoto, S. Amano, E. Fujiwara (University of Hyogo)S. Namba (Hiroshima University)A. Takahashi (Kyushu University)T. Higashiguchi (Miyazaki University)

Laser developmentsH. Fujita, K. Tsubakimoto, H. Yoshida ( ILE, Osaka University)


MEXT project(2003 - 2007)

Objectives: EUVL system R&D

Objectives1) Understanding physics of EUV source plasma and

providing guidelines for practical EUV source design・High power and high efficiency

EUV data base (experiments and simulations)Optimization of EUV plasma (laser and target)

・Clean, debris free sourceData base on ion and neutral atom emissionSuppression of high energy ions

2) Development of new targetslow density,minimum-mass, high feed rate

3) Development of laser technology5 kW/5 kHz DPSSLcompact, high efficiency, good beam quality, long life

MEXT: Ministry of Education, Culture, Science and TechnologyMETI; Ministry of Economy, Trade and Industry

Basic research on EUV plasma is important.

METI projectEUVA

(2002 - 2007)

Collaboration

Objectives


EUV power : 300W at source @10 - 30kHz・Large size plasma: 400 ~ 700 μm・Low laser intensity: ~ 1011 W/cm2

・Low electron density: 1019 ~ 1021 cm-3

・Electron temperature: 20 ~ 40 eV

low density targetfoam, double pulse, punch-out

optically too thin

optimum density-depth product1

2

510

2

510

2010.6 μm

τL=pl

asm

a sc

ale

leng

th (

μm)

10

100

1000

1017 1018 1019 1020

ion number density (cm-3)

etenduelim

it1m

m2sr (Ω

=π)

1.06 μm0.53 μm0.25 μm

12

510

1ns2ns

5ns10ns

20ns

optically too thick

Design windows for high power EUV source

For Sn, selection of laser wavelength and pulse width is importantbecause of large opacity for EUV emission.

Sn plasma absorbs EUV emission.

1.2

1.0

0.8

0.6

0.4

0.2

0.0

Tran

smis

sion

18161412108Wavelength (nm)

Te ~ 30 eV

Te ~ 0 eV

Sn

Guidelines


Research flow to high power and efficient EUV source

Radiation hydro code

Atomic data

0 5 10 15 20

0.9x1011 W/cm2

0.9x1012 W/cm2

1x1011 W/cm2

1x1012 W/cm2

Experiment

wavelength (nm)

Simulation

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

1010 1011 1012

実験

シミュレーション

Con

vers

ion

effic

ienc

y (%

)

Laser intensity (W/cm2)

Inte

nsity

Atomic model

Design of high power and clean EUV sourceEUV experiment

Conversion efficiency

Ele

ctro

n te

mpe

ratu

re(e

V)

Ion density (/cm3)1020

10

20

30

50

80

3%

2%

4%

101910181017

レー

ザー

強度

験

3% 実

Benchmark

Laser: I, τ, λTarget: Z, ρ,

Inte

nsity

Xe10+

Xe11+

Xe9+

8 10 12 14 16 18

4d-5p

Xe10+

Xe9+

4d-4f

By CXS

By HULLAC Code

wavelength (nm)

Benchmark

1.2

1.0

0.8

0.6

0.4

0.2

0.0

Tran

smis

sion


Te ~ 30 eV

Te ~ 0 eV

Sn

Simulation

Experiment

Data base

Guidelines


Emission spectra from charge-selected Xe and Sn ions were measured.

Charge exchange spectroscopy (CXS)Xe+q + ( He, Ar, Xe) Xe+q-1 ( n, l )

Xe+q-1 ( n’, l’ ) + hν

5 10 15 20 25 30 35 40

Inte

nsity

/ ar

b. u

nits

Wavelength / nm

q = 15

14

13

6

12

11

10

9

Snq+ - Xe

8

5

q = 7

6 12 18 24

Inte

nsity

/ ar

b. u

nits

Wavelength / nm

q = 18

17

16

15

14

13

q = 8

12

11

10

9

Xeq+ - He

4d-5f

4d-5p

4d-5p

4d-4f

13.5nm

Atomic data


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Atomic codes were improved by measured spectra.

12.5 13.0 13.5 14.0 14.5

CXS: Xe11+ + HeNIST: Xe10+

EUVA(DPP)

HULLAC

Cowan

Grasp

Wavelength (nm)

Atomic code

Observed peaks and HULLAC calculations

Xe

Sn


2D radiation hydro-code was developed.

ni

Te

< Z >

78

69

10

+200

+100

0

-100

-200

0 100 200 300 400 500 600X (μm)

Y (μm)

+200

+100

0

-100

-200

Y (μm)

+200

+100

0

-100

-200

Y (μm)

Sn plane target, laser diameter: 100μm

Radiation hydro-code





Electron density distribution was reproduced well by 2D code.

Experiment

T=0ns(Laser peak)

T=4ns


Radiation hydrodynamic simulation reproduces wellthe measured spectra.

Radiation hydro-code

80

60

40

20

0

Inte

nsity

(arb

. uni

t)


40

30

20

10

0

Inte

nsity

(arb

. uni

t)


20

15

10

5

0

Inte

nsity

(arb

. uni

t)


Laser intensity 9 x 1010 W/cm2

Laser intensity3 x 1011 W/cm2

Laser intensity9 x 1011 W/cm2

80

60

40

20Inte

nsity

(arb

. uni

t)


706050403020100

Inte

nsity

(arb

. uni

t)


20

15

10

5

0

Inte

nsity

(arb

. uni

t)


Experiment

Simulation


Optimum conditions for high conversion were obtained.

For solid targetSn: short pulse laser (~ 2 ns), CE > 4%Xe: long pulse laser (> 10 ns), CE ~ 2%Li: long pulse laser (> 10 ns), CE ~ 4%

10

20

30

50

80

ion density [cm-3]1017 1018 1019 1020

Li 20 ns

1017 1018 1019 1020

ion density [cm-3]

10

20

30

50

80 Xe 15ns

10

20

30

50

80

1017 1018 1019 1020ion density [cm-3]

elec

tron

tem

pera

ture

[eV

]

Sn 2ns

For Sn, opacity effect is important. Low density target is better.

Data base by simulation


1.5x1011 W/cm2ω: 1064 nm

2ω: 532 nm4ω: 266 nm

CE

(a.u

.)

1010 1011 1012

0.2

0.4

0.6

0.8

1.0

0

532 nm252 nm

Sn


1064 nm

CE

(a

.u.)

CO2YAG1064nm

109 1010 1011

10

20

30Sn


イオ

ン電

流(a

.u.)

1.4

1.2

1.0

0.8

0.6

0.4

0.2

0.0

CE

expe

rimen

t (%

)

10102 3 4 5 6 7

10112 3 4 5 6 7

10122

Laser intensity (W/cm 2)

2.5

2.0

1.5

1.0

0.5

0.0

CE sim

ulation (%)

1.2 ns

10 ns

2 〜 3 ns

8 〜10 ns

F/30


Sn2.0

1.5

1.0

0.5

Con

vers

ion

effic

ienc

y (%

)

10102 3 4 5 6 7 8

10112 3 4 5 6 7 8

1012


1.2 ns pulse duration 2.3 ns pulse duration 5.6 ns pulse duration 8.5 ns pulse duration

Pulse width dependenceWavelength dependence

1600

1400

1200

1000

800

600

400

200

0

Ener

gy n

orm

aliz

ed in

tens

ity


τ = 1.2 nsτ = 2.3 nsτ = 5.6 nsτ = 8.5 ns

For long τ, EUV emission decreases due to

self-absorption in plasma.

Sn, 1μm

Data base by experiments: Sn

For solid Sn target, opacity effect is important.

Solid Sn target: high CE for short pulse (~ns), long λ laser

Experimental results are well reproduced by simulation.


Conversion efficiency is improved by reducing target mass-density for long pulse laser.

Nd:YAG [1064 nm, 10ns]

2 4 6 8 10 12

2.5

2.0

1.0

1.5

0.5

0

SnO 2 (23%)SnO 2 (7%)

Sn (bulk)

Laser intensity (x1010 W/cm2)

CE

(%

/2πs

r/2%

BW

)

Sn concentration: 6%wt

-200 0 200 400 6000

0.5

1

1.5

Pulse separation time (ns)

EUV

CE

(%)

single pulse

Double-pulse

Pre-pulse: 0.1 J (<1010 Wcm-2) 0.5 μmMain Pulse: 0.5 J (2 x 1011 Wcm-2) 1μm

Low-density Foam Colloidal jet containing nanoparticles(double pulse irradiation)

Double pulse irradiation is effectivefor high efficiency.

With decrease of mass-density, CE and spectral purity are improved.

Long pulse (~10ns) laser can be applicable for low density target.

Data base by experiments: Sn


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-200 0 200 400 6000

0.5

1

1.5

2

2.5

Delay time (ns)

CE

(%)

Pre-pulse: 60 mJ (<109 Wcm-2) 0.5μmMain Pulse: 500 mJ (7 x 1010 Wcm-2) 1μm

Conversion efficiency was measured for different laser and target conditions.

0.16

0.14

0.12

0.10

0.08

0.06

0.04

0.02

0.00

CE

(arb

. uni

t) (1

3.5n

m/2

%bw

)

1010 2 3 4 5 6 7 891011 2 3 4 5 6 7 89

1012 2


BA C D

ω ２ω ３ω

0.3J/

0.5J/

1.2J/ω

0.25-0.5J/ 0.25/

ω

3ω

ω

2ω

Spec

tral

Inte

nsity

(A.U

.)

1816141210864wavelength(nm)

f31962ω /0.5J

f2750ω /0.5J

f26903ω /0.25J (x2)

Solid Xe targetLaser Intensity=1.5x10 11

W/cm 2

13.5nm

CE

(a

.u.)

Solid Xe

Solid Li

Solid Li

ダブルパルス照射


Without plasma

0

0.5

1

1.5

2

2.5

3

3.5

4

0

0.05

0.1

0.15

0.2

0.25

0 1 1010 2 1010 3 1010 4 1010

EUV energyC.E.

C.E

. [%]

laser intensity [W/cmCO2

2 ]CO2 laser intensity (W/cm2)

EU

V e

nerg

y [m

J/2π

sr/2

%B

W]

Xe target: high CE by long λ laser Li target: high CE by short λ laser

Xe jet

Data base by experiments: Xe and Li

Wavelength dependence: Xe Wavelength dependence: Li


Double pulseirradiation


10-4

10-3

10-2

10-1

100

0.1 1 10

Nor

mal

ized

spe

ctru

m d

N/d

ε

Ion kinetic energy ε (keV)

Experiment

Present model

1

(α =3, ε0= 3.0 keV)

Maximum ion energy predicted by the present analytical model

103

104

105

106

Ion

num

ber

3 4 5 6 7 8 9103

2 3 4 5 6 7 8 9104

Ion energy (eV)

punch-out

slab

Sn1+ Sn2+

Sn1+

Sn2+Sn3+

Ion emission

Isothermal expansion model reproduces well ion energy distribution.

10-6

10-5

10-4

10-3

10-2

10-1

100

0.1 1 10Ion kinetic energy ε (keV)

Experiment

(α =1, ε0=1.7 keV)

Nor

mal

ized

spe

ctru

m d

N/d

ε

Present model

1

Planar target

Cylindrical target

Maximum ion energy drastically decreases for low density target.

0 1 2 3 40

2

4

6

8

10

Ion velocity (x107 cm/s)

Ion

curre

nt (a

rb. u

nits

)

Single pulse

Dual pulsesDouble pulse

irradiation


Neutral atom: Sn

LIF（Laser Induced Fluorescence）to measure neutral atomic density of Sn

1 μm 200 nm 100 nm 60 nmPlane

Laser for plasma

Laser for excitation

Plane orthin foil

Excitationλ21 = 286.33 nm

Fluorescenceλ23 = 317.50 nm

5p2 3P2g3 = 5

6s 3P1g2 = 3

5p2 3P0g1 = 1

Energy level of atomic Sn

With reducing target thickness, almost all Sn atoms in the laser irradiated region are ionized, and fluorescence on the laser axis decreases. Fluorescence in the outer region is due to Snatoms ablated from the outer region of laser irradiation.

Importance of minimum-mass target


Minimum-mass target

laser

Target: Sn coated sphereIntensity：1011W/cm2

Pulse width：2ns

With decrease of Sn thicknessemission to laser direction decreases,

Emission from Sn atoms

1.5

1.0

0.5

0.0

Con

vers

ion

effic

ienc

y (a

u)

5 6 7 810

2 3 4 5 6 7 8100

2 3 4 5 6 7 81000

Sn layer thickness (nm)

800

600

400

200

0

Emission intensity from

Sn(I) atoms

EUV emission

Emission from Sn atoms

40nm

Suppression of debris to C1 mirror

10nm50 nm

LASER

1300 nm

Sn0+ 452 nm

Sn coat shell500 μmφ

Coating thickness of 40 nm is enough to produce high power EUV emission. : minimum-mass target

Number of EUV photon required 〜number of ions: 30mJ/pulse 2 x 1015 ions

Emission from Sn neutrals linearly increases with coating thickness while

keeping constant EUV intensity.


New targets

Xe frost (low density foam) Annular jet (liquid Xe)

200µm

Li cavity orLi droplet

Recombination wall

Multi module laser

Multi module laser

Novel targets have been proposed and developed.

Low density foam (Sn)

Liquid droplet with Sn or Li Forced cooling by recombination (Li)

Punch out (tape or disc, Sn, Li)

Rotating drum (solid Xe)


Two ways for minimum-mass Sn target

Pre-pulse

Droplet target

Main Pulse

EUV

Sn droplet

Colloidal droplet containing Sn nanoparticles

Sn jet > 1 km/s

1 mmheat laser

Minimum-mass target

# Double pulse irradiation：for 10 (100) kHz repetitionEUV energy / pulse：~ 30 (3) mJ number of Sn atoms：~ 2 x 1015 (1014)

Diameter of droplet：~ 50 (20) μm

Diameter of plasma：~ 400 (150) μm

Pre-pulse to expand plasmaMain pulseIntensity: ~1011 W/cm2

Pulse width: ~10 ns

# Punch-out target

Laser for punch-out

Base plate(transparent) Sn (1~10μm)

Heating laser


2 x 4 mm Rod, 2 pass



5 W

200 W

5000 W

(Regen. Amp) Fiber Front-end

SBS PC Mirror

Deformable Mirror

to Target Chamber/SBS Pulse Compression/Higher Harmonic Gen./Control of Focus Pattern

30 W

・Front end: Fiber oscillator + Fiber amplifier・Rod amplifier: Ceramic YAG, Uniform and high density pumping・Compensate for thermal effect: Image relaying and SBS PCM・System design: Simulation code (pumping, amplifier, propagation including diffraction)

1J/ 5kHz/ 5kW laser is under development.

Laser development


Summary

・Guideline to achieve high conversion from laser to EUV radiationhas been established by the experiments and the simulation.

・For Sn plasma, opacity effect is important, and short pulse laserand low density target will be effective for high efficiency.

・High conversion efficiency was achieved.Sn: 3 % (spherical plasma), SnO2 foam: 2.5 %, Xe (solid): 1.1 %, Li: > 2%

・Minimum-mass targets were proposed.Sn droplet with double pulse irradiation and punch-out target

・5kHz/5kW laser is under development, and will be applied for high power EUV experiment.


Please visit our poster presentations.・S. Kubodera et al., Low-debris EUV source using a colloidal microjet target

containing tin dioxide nanoparticles.・T. Kagawa et al., Comparison of EUV spectra from Sn ions between theoretical

RCI simulation and experiment.・H. Nishimura et al., Laser and target optimization for the highest conversion to

13.5 nm EUV light with laser produced minimum-mass tin plasma.・A. Sasaki et al., Modeling of the atomic processes in EUVL source plasma.・T. Aota et al., Temperature and density measurement of laser-produced EUV plasmas.・A. Takahashi et al., Emission characteristics of neutral atoms and ions of laser-

produced tin plasma.・H. Tanuma et al., EUV emission spectra of charge-selected Sn ions in charge

exchange spectroscopy.・K. Tsubakimoto et al., Development of high-peak, high-average LD pumped

solid-state laser system for EUV generation.・S. Amano et al., LPP-EUV source using cryogenic Xe and lithium new scheme targets.・K. Nagai et al., Development of low-density target for highly efficient EUV generation.・K. Nishihara et al., Theoretical guidelines of LPP-EUV sources for HVM.・F. Koike et al., Systematics of atomic 4d-4f transitions of atomic ions in EUVL source

plasmas and neighboring atomic numbers.・A. Sunahara et al., Radiation hydrodynamic simulation for LPP EUV sources.

Documents

Summary of Japanese Academic Support Program for LPP · PDF fileS. Fujioka, T. Aota, K. Nagai, T. Norimatsu ( Osaka University) S. Uchida, Y. Shimada, M. Yamaura, K. Hashimoto (Institute