liquid-jet laser-plasma sources for sub-13 nm emission · sub 13 nm: which are our options? prague...

Biomedical and X-Ray Physics, KTH, Stockholm Prague 2018

Liquid-jet laser-plasma sources for

sub-13 nm emission

Hans HertzBiomedical & X-Ray Physics

Dept. of Applied Physics

Royal Inst. of Technol. (KTH)

Stockholm

&

COB: Excillum AB

Biomedical and X-Ray Physics, KTH, Stockholm

Present source for 13 nm EUVL

Prague 2018

• Wavelength: =13.5 nm

• Regenerative target: Sn

• High-reflectivity mirror: Mo/Si

From O’Sullivan, J Phys B (2015)


Why shorter wavelength?

Prague 2018

Key issues:

• Laser-plasma source @ sub-13 nm• Power

• Target

• stable

• regenerative

• Mirror reflectivity

• Photo resist sensitivity

RESOLUTION= 𝑘1𝑁𝐴

DOF = 𝑘2𝑁𝐴 2


What do we have?

Liquid-jet/droplet laser-plasma sources

50 mm

2-4 nm: Water-window =11-13 nm: EUV Litho

Rymell et al, Opt. Commun. (1993)

+ High rep.-rate operation

+ High-power operation

+ Tailored spectral emission

+ Negligible debris

/>500

Ethanol

Rymell et al, APL (1995); Berglund et al APL (1997);Jansson et al, RSI (2005) ;Hansson et al, MNE (2001);Takman et al APL (2004) ;Martz et al, Opt. Lett. (2012)

2.4 nm Liquid nitrogenPrinciples


Photon flux

Source size

2000 Hz

100 Hz

10 Hz

= 2.48 nm power:

200 W, 600 ps, 2 KHz DPSS laser plasma

Spectral brightness:

Lab source at early-bending-magn level!

Martz et al, Opt. Lett. (2012)


Sub 13 nm:

Which are our options?

Prague 2018

Xe

C Ka


Target (nm) Mirror

Sn 13.5 Mo/Si

Xe 11.5 Mo/Be, Ru/Be..

Gd, Tb 6-7 La/B

C, N 2-4 W/B4C, Cr/Sc

• moderately/highly charged ions

• n=4 − n=4 transitions


Liquid-jet/droplet basics

LaminarTransition Turbulent

Spray


Liquid-jet/droplet basics

Stability: Laminar flow region

L

L= 𝑙𝑛𝑎

𝑜

𝑣8𝑎3

+

6𝑎

LN2 jet


=13.5 nm:

First liquid-tin-jet source

Prague 2018

Jansson et al .

Appl. Phys. Lett. (2004)

Stable jet @ >250 C Spectral match Debris:

CE: 2.5% into (2%BW2sr)

1 h gave coating

Mitigation need: ~108

PRESENTLY:

Sn liquid jets is the source for HVM EUV litho


=11.5 nm:

First liquid-xenon-jet source

Prague 2018

Hansson et al, Microel. Engin. (2000);

Spectrum

Jet cooling

Stability

50 mm

Exp. arrangement


Cryogenic liquid jets:

LN2 jet laser-plasma stability

Prague 2018

Freeze Burst Sinuous Spray

instability

CW Pulsed

Illumination

Classical liquid-jet stabilityHigh-speed jet imaging4 ns laser, 20 Hz

Fogelqvist et al, J. Appl. Phys. (2015)

LN2 liquid-jet

stability


Avoiding evaporative effects while still keeping

pressure low

Prague 2018

Local radiative heating

No

stabilizationPressure

stabilizationRadiative heat

stabilization


Long-term stability: 1h

Prague 2018


=11.5 nm:

Mirrors

Prague 2018

Chkhalo & Salashchenko, EUVL workshop 2013


= 6-7 nm:

Gd, Tb

Prague 2018

La/B mirrors:

theoretically R=80%



= 6-7 nm w/ Gd, Tb

in liquid jets?

Prague 2018

E.g., C16H28GdN5O9

MRI contrast agent

7% Gd by weight

Increase possible

,,: waterlike


= 6-7 nm w/ Gd, Tb

nanoparticle slurries?

Prague 2018

(a) (b) (c)

(d) (e)

Y Zr Nb

Uniform size distribution

Potentially >10-20 % by weight

,,: waterlikeLi et al, submitted (2018)

MRI contrast agent :

Gd2O3 NP:s


= 2-4 nm?

Prague 2018

Ethanol

Methanol

Liquid nitrogen

Rymell et al, Opt. Commun. (1993) Berglund et al, RSI (1996)


= 2-4 nm

Power?

Prague 2018

Ultraviolet prepulse for enhanced x-ray emission and brightness

from droplet-target laser plasmasM. Berglund,a) L. Rymell, and H. M. Hertz

Department of Physics, Lund Institute of Technology, P. O. Box 118, S-221 00 Lund, Sweden

~Received 28 May 1996; accepted for publication 9 July 1996

We show that an ultraviolet prepulse significantly enhances the water-window x-ray emission and

brightness for a droplet-target laser plasma. By combining a 65 mJ, 120 ps, =532 nm main pulse

with an up to 3 mJ prepulse, the emitted x-ray photon flux may be increased more than eight times.

The resulting C VI =3.37 nm line emission is more than 3×1012 photons/sr.pulse, corresponding

to a conversion efficiency above 3%/line. The integrated spectral brightness is increased two times

and is found to reach its maximum for different prepulse parameters than those resulting in

maximum photon flux. © 1996 American Institute of Physics. @S0003-6951~96!03938-1#

Berglund et al, APL (1996)

106 drops/sec


= 2-4 nm

Power II

Prague 2018

Berglund et al, APL 1996: Target: C2H5OH (52% C by weight)

Emission: = 3.37 nm E=368 eV (C VI)

Laser: 3+65 mJ/pulse

Flux: 3×1012 photons/sr×pulse

Assume:Rep rate: 105 Hz

Laser: 100 mJ/pulse (i.e., 10 kW)

Collection: sr

Results in:Approx. 100 W @ =3.37 nm

Issues?:Jet stability?

Self absorption?


Summary

• Liquid-jet laser plasmas w/ =2-11 nm

emission are decently well understood.

• Power? – possibly

• Stability? – possibly

• Mirrors? – see upcoming talk

• Will it happen?

Prague 2018


Biomedical & X-Ray PhysicsDept of Appl. Physics @ KTH/Stockholm

Soft X-Rays

Hard X-Rays Eye Optics

X-Ray Optics

Ultrasonics

ultrasound control

Nanochemistry

Teaching & Technical


Which are our options?

Prague 2018

From xxxx, SPIE ()


IN PARALLELL

First liquid-droplet EUV source – oxygen @ 13 nm

Prague 2018

Rymell et al, Proc. XRM IV (1993)

Ethanol target

Nd:YAG 10 ns

Low debris


EUV sources II:

Next liquid-droplet EUV source - water droplets

Prague 2018

Inte

nsi

ty (

arb

. u

nit

s)1

0.5

010 11 12 13 14 15

Wavelength (nm)

Hertz et al, SPIE (1995)

Malmqvist et al, EUV Litho, OSA (1996)

Why use liquid jet/droplet laser-plasmas for HVM EUV litho?

• Thermal• Hot plasma at a distance

• High average power via high rep rate• Rapid target material production

O VII @ 13 nm


Liquid-jet/droplet laser-plasma sources:

Early history

Prague 2018

1992

First liquid-droplet

Laser-plasma slide

First spectrum

First crew

1988?

First XRM slide1990

Cf. Göttingen

liquid-jet laser-plasma sources for sub-13 nm emission · sub 13 nm: which are our options? prague...

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