Liquid-Jet Laser-Plasma Sources for Sub-5-Nm Emission

Liquid-jet laser-plasma sources for sub-13 nm emission

Hans Hertz Biomedical & X-Ray Physics Dept. of Applied Physics Royal Inst. of Technol. (KTH) Stockholm & COB: Excillum AB

Biomedical and X-Ray Physics, KTH, Stockholm Prague 2018 Present source for 13 nm EUVL

• Wavelength: =13.5 nm • Regenerative target: Sn • High-reflectivity mirror: Mo/Si

From O’Sullivan, J Phys B (2015)

Biomedical and X-Ray Physics, KTH, Stockholm Prague 2018 Why shorter wavelength?

 RESOLUTION= 푘 1 푁퐴

Key issues: • Laser-plasma source @ sub-13 nm • Power • Target • stable • regenerative

• Mirror reflectivity • Photo resist sensitivity  DOF = 푘 2 푁퐴 2

Biomedical and X-Ray Physics, KTH, Stockholm Prague 2018 What do we have? Liquid-jet/droplet laser-plasma sources

Principles 2.4 nm Liquid nitrogen + High rep.-rate operation + High-power operation 50 mm + Tailored spectral emission + Negligible debris

Rymell et al, Opt. Commun. (1993)

2-4 nm: Water-window =11-13 nm: EUV Litho Ethanol />500

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)

Biomedical and X-Ray Physics, KTH, Stockholm Prague 2018 = 2.48 nm power: 200 W, 600 ps, 2 KHz DPSS laser plasma Photon flux Spectral brightness: Lab source at early-bending-magn level!

Source size 2000 Hz

100 Hz 10 Hz

Martz et al, Opt. Lett. (2012)

Biomedical and X-Ray Physics, KTH, Stockholm Prague 2018 Sub 13 nm: Which are our options?

• moderately/highly charged ions • n=4 − n=4 transitions

Target  (nm) Mirror Sn 13.5 Mo/Si Xe Xe 11.5 Mo/Be, Ru/Be.. Gd, Tb 6-7 La/B

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

C Ka

From O’Sullivan, J Phys B (2015)

Biomedical and X-Ray Physics, KTH, Stockholm Prague 2018 Liquid-jet/droplet basics

Transition Turbulent Laminar Spray

Biomedical and X-Ray Physics, KTH, Stockholm Liquid-jet/droplet basics Stability: Laminar flow region LN2 jet

푎 8푎3 6푎 L= 푙푛 푣 + 표  

Biomedical and X-Ray Physics, KTH, Stockholm =13.5 nm: First liquid-tin-jet source

Stable jet @ >250 C Spectral match Debris:

1 h gave coating Mitigation need: ~108

CE: 2.5% into (2%BW2sr)

PRESENTLY: Sn liquid jets is the source for HVM EUV litho Jansson et al . Appl. Phys. Lett. (2004)

Biomedical and X-Ray Physics, KTH, Stockholm Prague 2018 =11.5 nm: First liquid-xenon-jet source

Exp. arrangement Jet cooling

Stability Spectrum

50 mm

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

Biomedical and X-Ray Physics, KTH, Stockholm Prague 2018 Cryogenic liquid jets:

LN2 jet laser-plasma stability High-speed jet imaging Classical liquid-jet stability 4 ns laser, 20 Hz

LN2 liquid-jet stability Freeze Burst Sinuous Spray instability CW Pulsed Illumination Fogelqvist et al, J. Appl. Phys. (2015)

Biomedical and X-Ray Physics, KTH, Stockholm Prague 2018 Avoiding evaporative effects while still keeping pressure low

Local radiative heating

No Pressure Radiative heat stabilization stabilization stabilization

Biomedical and X-Ray Physics, KTH, Stockholm Prague 2018 Long-term stability: 1h

Biomedical and X-Ray Physics, KTH, Stockholm Prague 2018 =11.5 nm: Mirrors

Chkhalo & Salashchenko, EUVL workshop 2013

Biomedical and X-Ray Physics, KTH, Stockholm Prague 2018 = 6-7 nm: Gd, Tb

La/B mirrors: theoretically R=80%

From O’Sullivan, J Phys B (2015)

Biomedical and X-Ray Physics, KTH, Stockholm Prague 2018 = 6-7 nm w/ Gd, Tb in liquid jets?

E.g., C16H28GdN5O9

MRI contrast agent 7% Gd by weight

Increase possible

,,: waterlike

Biomedical and X-Ray Physics, KTH, Stockholm Prague 2018 = 6-7 nm w/ Gd, Tb nanoparticle slurries?

(a) (b) (c) Y Zr Nb

(d) (e)

MRI contrast agent :

Gd2O3 NP:s

Uniform size distribution Potentially >10-20 % by weight ,,: waterlike Li et al, submitted (2018)

Biomedical and X-Ray Physics, KTH, Stockholm Prague 2018 = 2-4 nm?

Ethanol Methanol

Liquid nitrogen

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

Biomedical and X-Ray Physics, KTH, Stockholm Prague 2018 = 2-4 nm Power?

Ultraviolet prepulse for enhanced x-ray emission and brightness from droplet-target laser plasmas M. 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#

106 drops/sec

Berglund et al, APL (1996)

Biomedical and X-Ray Physics, KTH, Stockholm Prague 2018 = 2-4 nm Power II

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?

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

Biomedical and X-Ray Physics, KTH, Stockholm Prague 2018 Biomedical & X-Ray Physics Dept of Appl. Physics @ KTH/Stockholm

Soft X-Rays X-Ray Optics

ultrasound control

Nanochemistry Ultrasonics

Hard X-Rays Eye Optics Teaching & Technical

Biomedical and X-Ray Physics, KTH, Stockholm Which are our options?

From xxxx, SPIE ()

Biomedical and X-Ray Physics, KTH, Stockholm Prague 2018 IN PARALLELL First liquid-droplet EUV source – oxygen @ 13 nm

Ethanol target Nd:YAG 10 ns Low debris Rymell et al, Proc. XRM IV (1993)

Biomedical and X-Ray Physics, KTH, Stockholm Prague 2018 EUV sources II: Next liquid-droplet EUV source - water droplets

O VII @ 13 nm

0.5 Intensity (arb. units) (arb. Intensity 0 10 11 12 13 14 15 Wavelength (nm)

Why use liquid jet/droplet laser-plasmas for HVM EUV litho? • Thermal • Hot plasma at a distance • High average power via high rep rate Hertz et al, SPIE (1995) • Rapid target material production Malmqvist et al, EUV Litho, OSA (1996)

Biomedical and X-Ray Physics, KTH, Stockholm Prague 2018 Liquid-jet/droplet laser-plasma sources: Early history

1992 1988?

1990 First XRM slide

First spectrum

First liquid-droplet Laser-plasma slide Cf. Göttingen First crew

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