2012 International Workshop on EUV and Soft X-Ray Sources

October 11th, 2012, UCD, Dublin, Ireland

Takeshi Higashiguchi1

1Utsunomiya University 2Nagaoka University of Technology 3HiLASE Project, Institute of Physics AS, Czech Republic 4University College Dublin (UCD)

Takamitsu Otsuka1, Weihua Jiang2, Akira Endo3, Thomas Cummins4,

Colm O’Gorman4, Bowen Li4, Deirdre Kilbane4, Padraig Dunne4, and

Gerry O'Sullivan4

Session 11, S11

Plasma-based UTA Emission in BEUV

& Water Window Spectral Regions

XUV & EUV sources

- Compact discharge 40-nm source

- 13.5-nm high brightness sources

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BEUV & WW-SXR sources

- BEUV sources at 6.X nm

- Water window SXR sources

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Figure 2: Takeshi Higashiguchi et al.

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Experimental result700 eV

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From Banine presentation shows as follows:

(1) extensive (beyond 8 nm@~2017)

(2) 6.X nm choice: Best transmission & Easier Manufacturing

(3) Source: New fuel is needed (Gd and/or Tb, other???)

(4) R ~ 80% (cal), R ~ 40% (exp)@La/B4C MLM

(5) Optical throughput for 6.7 nm & 13.5 nm is comparable!!!

Why 6.X nm EUV source? Beyond EUV (BEUV) source

Another material plasmas UTA emission from high-Z plasma

Various target emissions

Introduction…

from previous presentation

S. S. Churilov et al., Phys. Scr. 80, 045303 (2009).

6.7 nm: Gd, Tb plasmas Mo/B4C mirror

gf spectra & ionic population We confirm the UTA resonant lines around 6.7 nm

6.0 6.5 7.0 7.5 8.00

70

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70Gd

12+

Gd13+

Gd14+

Gd15+

Gd16+

Gd17+

Gd18+

Wavelength (nm)

gf

6.0 6.5 7.0 7.5 8.00

35

35

35

35

35

35

35Gd

19+

Gd20+

Gd21+

Gd22+

Gd23+

Gd24+

Gd25+

Wavelength (nm)

T. Otsuka et al., Appl. Phys. Lett. 97, 111503 (2010).

B. Li et al. Appl. Phys. Lett. 99, 231502 (2010).

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Wavelength (nm)

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Wavelength (nm)

Gd

Tb

Gd and/or Tb plasmas for 6.X nm

Feasibility study for 6.X-nm sources

Feasibility study for 6.X-nm sources

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Wavelength (nm)

Gd

Tb

Which wavelengths at 6.X nm?

Tb Gd

6.67 nm@LaN/B MLM

B. Li et al. Appl. Phys. Lett. 101, 013112 (2012).

Complex target (proposal, preliminary)

• Max MLM reflectivity peak lies between the peaks of Gd and Tb

- Bowen et al., APL 101, 013112 (2012)

• Gd – 6.76 nm LaNB4C – 6.66 nm

• Tb – 6.5 nm LaNB – 6.63 nm

• Gd/Tb mix plasma could yield higher in band emission

• Wavelength “Tuning” may be possible

• Atomic calculations coupled with CR code

O’ Gorman et al. – in preparation

1064 nm,

150ps

•T =150 ps

•Spectral profile shows higher in band

emission

•Dual laser plasma

•Higher temperature and more absorption

•Emission has higher spectral purity than Gd & Tb

Solid complex target

Low-density complex target

1064 nm,

150ps

1064 nm,

10 ns Gd/Tb

Gd/Tb Gd/Tb

Form Gd/Tb Target with 30% initial density

Similar results with reduced absorption

Other plasma: Phosphorus

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• Phosphorus spectra observed using 10 ns Nd:YAG laser, φ = 7x1011 W/cm2

• Line emission observed in 6.5-6.8 nm region due to 2p5 – 2p43d transitions of P6+ and 2p4 – 2p33s transitions of P7+ ions

• Wavelength of line emission appears better matched to in-band of MLM than Gd and Tb UTA

6.2 6.4 6.6 6.8 7 7.2 7.40

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P spectrum

Gd spectrum

MLM in-band 6.656 nm

T. Cummins et al. (In preparation)

* Gd spectrum taken from C. O’Gorman et al Appl. Phys. Lett. 100, 141108 (2012)

* Tb spectrum taken from S. S. Churilov et al Phys. Scr. 80 (2009)

6.2 6.4 6.6 6.8 7 7.2 7.40

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P spectrum

Tb spectrum

MLM in-band 6.63 nm

Line emission from Phosphorus plasma

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Electron temperature (eV)

Ion

po

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• FLYCHK code calculates ion population states and average ionization as a function of electron temperature

• Optimum electron temperature to achieve P6+-P7+ is around 30 eV, comparable to existing requirement for Sn, and lower than > 140 eV for Gd and Tb

• Normalised in-band measurements show peak emission at around 7x1011 W/cm2

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CE for 6.63 nm MLM

CE for 6.656 nm MLM

T. Cummins et al. (In preparation)

Line emission from Phosphorus plasma

Optimum electron temperature: 110 eV

CO2 laser intensity:

2.4 × 1011 W/cm2

B. Li et al. Appl. Phys. Lett. 99, 231502 (2010).

Development of hybrid laser

CO2 laser-produced plasma behavior? - Low density, high temperature plasma

Etendue - Expanding plasma size depends on temperature

- Incident angle to 0.6%BW MLM at 6.X nm

- etc…

Low density & 100-eV plasmas

CO2 laser-produced Sn plasma

Y. Ueno et al. Appl. Phys. Lett. 91, 231501 (2007).

CE is expected to be 1.5% at the bandwidth of 0.6% for 6.X-nm BEUV.

2011 EUV Sources Workshop Nov 7-10 Dublin 7

Experiments on LPP with CO2 laser C

E, %

EUV (hole)

EUV (flat target)

CO2 laser

EUV (large hole) In

ten

sity,

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3 shots 4 shots 5 shots 7 shots

View of holes in 80 Gd foil after

defined number of laser shots

Target – Gd foil 80 thick

Laser energy 600 mJ

Laser spot dia. 300

Pulse duration 100 ns

Pow. density ~1010 W/cm2

CO2 laser-produced Gd plasma at ISAN

CEs are comparable under 2%BW Gd and Tb have the similar property due to Dn = 0 UTA emission

EUV CEs

(in 2% BW)

1064 nm: 1.1%

532 nm: 0.7%

355 nm: 0.5%

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Wavelength (nm)

1064 nm532 nm355 nm

Spot diameter: 50 um (FWHM)

Laser energy: 320 mJ

Laser intensity: 1.6 x 1012 W/cm2

T. Otsuka et al., APL 97, 111503 (2010).

T. Otsuka et al., APL 97, 231503 (2010).

Next step: short CO2 laser installation sub-ns 10-Hz hybrid 10.6-um laser development

Palitra Optical Parametric Amplifier Tuning Curves

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Typical Efficiencies with Quantronix Amplifier System, Pulse Duration 70-200 fsCO2 laser

20 uJ (160 uJ)

Expected:

160 mJ

Summary fro 6.x-nm BEUV

We have demonstrated the efficient EUV sources

- Numerical evaluation of Gd and Tb (by Li, Kilbane & O’Sullivan)

- Proposal of mixing target for MLM (by O’Gorman & Otsuka)

- P plasma for low-temp plasma (by Cummins & Otsuka)

- Hybrid laser system (by Otsuka, Sakaue, Miura & Endo)

Our objective is a demonstration of high-brightness, high energy EUV/soft x-

ray source in water window (3.2 nm) for the first time in the world!!!

Multilayer

mirror

Laser

Plasma light source

Soft X-ray CCD

Biological sample

EUV

Pinhole

Schwarzchild

Optics

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Experiment

Calculation

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EUV & BEUV source study

Wavelength: 13.5 & 6.x nm

Lithography Life Innovation Compact source development for Bio.

Wavelength: 2-4 nm

Proposal (APL x 1)

In vivo cell observation Original micro source

Single shot, flash biological imaging

Si / SiO

Sn: 10 - 15 um φ

Laser 2

Shorter wavelength

APL x 7 (2010-2012)

New concept flash WW-SXR source

Moseley's law?

Z scaling: quasi-Moseley's law by Prof. O’Sullivan and Prof. Endo

UTA Z = 55: Cs

Z = 60: Nd

Z = 64: Gd

Z = 65: Tb

Z = 71: Lu

Numerical simulation

l (nm)

l (nm)

2 4

2 4

(a) Line spectrum

(b) UTA

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Figure 2: Takeshi Higashiguchi et al.

Unresolved transition array (UTA)

T. Higashiguchi et al., Appl. Phys. Lett. 100, 014103 (2012).

New concept flash source

Bi plasma condition

T. Higashiguchi et al., Appl. Phys. Lett. 100, 014103 (2012).

Bi plasma spectral analysis

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Experimental result700 eV

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1: 4f-5g, < Bi35+

2,3: 4p-4d, 4d-4f,

Bi36+-Bi45+

4: 4d-4f

Appl. Phys. Lett. 100, 014103 (2012).

Dual laser pulse Bi plasma

Dual laser pulse Bi plasma

Observation of Leydig cell in culture solution

Sample: Cultured on SiN membrane and fixed by formalin solution.

Beam line: Spring-8 BL27SU,

• Photon energy: 260～600 eV (2.1 ～ 4.8 nm ),

• Exposure time: 0.8 180 sec,

• Spatial resolution: 1.1mm,

• Wavelength resolution: l/Dl = 2000

Image comparison:

536eV – 529eV VI diff. int. img. ROI

Prof. Ejima@Tohoku University

Absorption in a biological sample

透過率像 2.38nm

試料

水

Prof. Ejima@Tohoku University

Proposal of two-color WW-SXR source

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Experimental result700 eV

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(a)

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Figure 2: Takeshi Higashiguchi et al.

T. Higashiguchi et al., Appl. Phys. Lett. 100, 014103 (2012).

Challenging: 1-keV WW-SXR

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Figure 2: Takeshi Higashiguchi et al.T. Higashiguchi et al., Appl. Phys. Lett. 100, 014103 (2012).

Low density & 100-eV plasmas

ne µ1/ lL2

Te µ (ILlL2 )1/2 µ lL / t L

Development of sub-ns CO2 (10.6 um) laser

Next step: short CO2 laser installation sub-ns 10-Hz hybrid 10.6-um laser development

Palitra Optical Parametric Amplifier Tuning Curves

Wavelength (nm)1000 10000

Co

nve

rsio

n E

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ien

cy

(%

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0.1

1

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UV3

UV2

UV1

VIS3

VIS2

VIS1

Sign

alId

ler

IR1

IR2

IR3

Typical Efficiencies with Quantronix Amplifier System, Pulse Duration 70-200 fsCO2 laser

20 uJ (160 uJ)

Expected:

160 mJ

Future for more HW: collaboration

Summary

Thanks a million!!!