San Diego, 25.11.7-9 EUV Source Developments on Laser-Produced Plasmas using thium New Scheme Target Shuji MIYAMOTO, Sho AMANO, Takahiro INOUE Petru-Edward NICA, Atsushi SHIMOURA Kakyo KAKU, and Takayasu MOCHIZUKI Laboratory of Advanced Science and Technology for Industry,, JAPAN *miyamoto@lasti.u-hyogo.ac.jp This work was performed under the auspices of MEXT(Ministry of Education, Culture, Science and Technology, Japan) under contract subject "Leading Project for EUV lithography source development.
Abstract We propose to use lithium new scheme targets, "forced recombination" and "expansion energy re-conversion" targets. As a new deposition-free target, the use of lithium was proposed by Cymer [1]. We observed a comparable CE with tin target in a simple planer target [2]. In this paper, we report spatial and temporal characterizations of EUV emission from these new scheme lithium targets. Experimental results will be discussed comparing with theoretical analysis and numerical calculations. Laser systems used in the above experiments were a 32 Hz repetition rate Nd:YAG slab laser and a 1Hz Nd:YAG rod laser with 1J pulse energy. EUV emissions were measured by an imaging camera, a transmission and a grazing incidence spectrometers, fast EUV photo-diodes and a Flying Circus 3 for power monitor. [1] D.Myers, et al.: 3rd Int. EUVL Symposium, So3, Miyazaki, Japan, 2-4 Nov., 24. [2] Shuji Miyamoto, et al.: EUV Source Workshop, PO-9, San Jose, 27 Feb., 25.
Deposition free EUV-LPP target : Cryogenic Xe and Hot We require a deposition free EUV source for lithography. Deposition-free target : cryogenic Xe NTT-AT Deposition free mirror : hot mirror Easy evaporation target :
EUV multilayer mirror usable at high temperature* by H.Takenaka @ NTT-AT *H. Takenaka, et. al., OSA TOPS on Extreme Ultraviolet thography 1996, Vol. 4, pp.169-172.
Experimental setup of plane thium targets Double pulse laser Main Laser FCI :Flying Circus Imaging with time gated MCP camera 1ns Pre-pulse Laser Lens position grating slit EUV spectrum with spatial resolution CCD GISM:Grazing Incidence Spectrometer Time resolved EUV image 45 9 pinhole TGSM :Transmission Grating Spectrometer XRD: X-ray Photo Diode EUV angler distribution Forced recombination Tamper
Experimental setup of plane thium targets Lens position grating slit Spectrum CCD GISM x1 3 12 1 8 6 4 2 5 4 3 2 1 9.5 1. 1.5 nm 1.8nm(2+, 1s-4p) 11. 11.39nm(2+, 1s-3p) x1 3 11.5 13.5nm(2+, 1s-2p) 12 8 4 13.2 13.3 13.4 13.5 13.6 13.7 13.8 nm 17.8nm(1+, 1s2-1s3p) 2% b.w. 2% 19.9nm(1+, 1s2-1s2p) 45 9 pinhole 6 8 1 12 14 nm 16 18 2 22 TGSM Spectral Intensity (A.U.) Xe ω /.5J 2 ω /.5J Laser Intensity =1.5x1 11 W/cm 2 13.5nm 2% b.w. 3 ω /.25J (x2) 6 8 1 12 wavelength(nm) 14 16 18nm
Emission spectra from solid lithium target : Spatially integrated spectrum and estimeted T e x1 3 12 1 8 6 4 2 5 4 3 2 1 continuum 12.1eV +-.27eV 9.5 LP=- (6e9 W/cm2) 1. 1.5 nm 1.8nm(2+, 1s-4p) 11. 11.39nm(2+, 1s-3p) x1 3 11.5 12 8 4 13.5nm(2+, 1s-2p) 13.2 13.4 17.8nm(1+, 1s2-1s3p) 2% 13.6 13.8 19.9nm(1+, 1s2-1s2p) nm 6 8 1 12 14 nm 16 18 2 22
Typical angular distributions of EUV emission from target laser - 3-15 - 45-6 -75 15 3 45 6 75-9 1. 8. 6. 4. 2.2.4.6.8 1 Laser pulse = 1J/1ns Focus lens position = -15 Roughly isotropic angular distribution was observed.
Dependence of CE on laser focus position 1) Measured CE of was 1.2 %/2πsr, and it was comparable with that of Sn. 2) Optimum laser intensity for was an order of magnitude lower than that for Sn. 1.6 2 1 1 W/cm 2 8 1 1 W/cm 2 CE @ 13.5 nm [%/2πsr/2%bw] 1.4 1.2 1..8.6.4.2 (.55 J) (.27 J) Sn (.5 J) 2 1 12 W/cm 2 CE was estimated by using spectra data of XRD. -2-1 1 2 Lens position []
2+ fraction was calculated by CRE model CRE : Collisional Radiative Equibrium n e =1 2 /cc + 3+ 2+ fraction 1 2 5 1 2 5 1 electron temperature (ev)
: WP Double pulse irradiated lithium target Small increase of CE and emission size were observed EUV(13.5nm) Intensity (a.u.) 5 4 3 2 1 thium Double Pulse Irradiation LP= LP=-6 Mail laser:.5j/1ns PrePulse:.6J/2ns DoublePulse(LP=, 2e12W/cm2) Single(Main only LP=) Single(Pre only LP=) DoublePulse(LP=-6, 2e1W/cm2) Single(Main only LP=-6) LP=-6 ns LP=-6 QuickTimeý Dz TIFFÅiLZWÅj êlí ÉvÉçÉOÉâÉÄ Ç Ç±ÇÃÉsÉNÉ`ÉÉǾå ÇÈÇžÇ½Ç ÇÕïKóvÇ-ÇÅB 527 6 5 4 3 2 1. 3. 2.5 2. 1.5 1. 3. 2.5 2. LP= ns LP= 1.5 12 9 1.5 12 9 ns 2. 6 2. 6 68 ns 2.5 3 2.5 3. 3. 3 5 1 Delay time (ns) 15 2ns 46ns 532 1.5 68 ns 1. 1.5 2. 2.5 3.
: FR Forced Recombination Radiator experiment Enhanced EUV emission at wall was observed 14(lens:-6) Cu5(lens:-6) lithium target wall Cu wall laser Wall : Copper or polyethylene PE22(lens:-6) wall (CH)n Observed by EUV imaging camera
: FR EUV emissions are enhanced by recombination at electron Donor Enhance EUV EUV Intensity (a.u.) 2x1 3 15 1 5 foil with Donor without Donor Wall electron donor..5 1. 1.5 Distance from target surface () 2.
: FR EUV emission time history shows a hump at colliding time Measured by a high-speed EUV photo diode (HS-XRD) High speed EUV photo diode signal (a.u.).5v.4.3.2.1. 35ns without Donor Distance = 1 v = 1 / 35 ns = 2.8 1 4 m/s with Donor -4-2 2 4 6 8 1ns time (ns)
: FR Time evolution of the plasma: - expansion energy re-conversion 13.5 nm time-resolved image (FCI) (Lens position: -5) (Lens position: -5) (Lens position: -5) wall wall wall t=-1ns t = ns t = 1 ns (Lens position: -5) (Lens position: -5) wall wall t = 2 ns t = 3 ns
: FR Time evolution of the plasma: free expansion 13.5 nm time-resolved image (FCI) t = -1 ns t = ns t = 1 ns t = 2 ns t = 3 ns
: FR Setup of target and spectrometer Plasma Laser Without Wall 2 target Pinhall 4 Plasma Wall Laser 6 5 1 15 2nm Wavelength (nm) With Wall 2 target Pinhall 4 6 Plasma 5 1 15 2nm Wavelength (nm)
: FR Forced recombination wall re-emit the EUV and keep the emission volume small thium 2 4 6 Without wall 5 1 15 Wavelength (nm) 2nm thium 2 4 Wall 6 With wall 13.5nm 5 1 15 Wavelength (nm) 2nm
: FR Plasma electron temperature distribution estimated by continuum radiation 5pixel 2 4 6 5 1 15 Wavelength (nm) 2nm
: FR Intense EUV emission at wall caused by temperature rise laser wall 4 3 with Wall LP=-8 (1e1 W/cm2) f5119 f5112 12 1 8 ev 2 6 x1 3 1 4 2 ev 4 3 2 with Wall LP=-4 (4e1 W/cm2) f5117 f5114 12 1 8 6 x1 3 ev -.5 4 3 2..5 1. with Wall 1.5 LP=-1 (6e9 W/cm2) f512 f5111 2. 12 1 8 6 x1 3 1 4 2 1 4 2 -.5..5 1. 1.5 2. -.5..5 1. 1.5 2.
: FR Forced Recombination Radiator thium droplet with jet Gas puff Droplet plasma collide on sheet jet C cavity target Plasma-plasma collision
Conclusion Observed CE of thium plane target irradiated by ω-laser was as large as that of Tin target. Pre-pulse (double pulse) irradiation of lithium targets were tested. Small improvement of CE was observed without significant change of emission size. Forced Recombination Radiator, new scheme lithium target was demonstrated. EUV emission was enhanced at wall. Duration of EUV emission was also elongated. Plasma temperature was increased at the wall. CE improvement of 5-1% is expected.
Future work Further test of Forced Recombination Radiator target. Cavity lithium target. Demonstration of large solid angle extraction of EUV from forced recombination target