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 L 푎 8푎3 6푎 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%BW2sr) 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 1 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.