Modelling of high intensity EUV light sources based on laser- & discharge- produced plasmas Sergey V. Zakharov +, Peter Choi, Vasily S. Zakharov NANO UV sas EPPRA sas + also with RRC Kurchatov Institute, Moscow, Russia
OUTLINE High energy density plasma in EUVL ZETA Z* Z*BME RMHD codes Non-equilibrium plasma radiation kinetics plasma radiance limit highly charged Xe i emission LPP & Combined Nd:YAG-CO 2 laser pulse Nano-UV source modelling for EUV and soft X-ray source Modelling tool development in FIRE-project
High energy density laser or magnetically driven heavy ion plasmas Z-pinch Z machine 20MA W, Xe plasma Current density 10 8-10 9 A/cm 2 Ion density 10 19-10 20 cm -3 Electron temperature 300-600eV Emission energy 2MJ Radiance 1TW/mm 2 sr (200MW/mm 2 sr in 2% band at 13.5nm WL) Hohlraum target Laser energy 1.8MJ Au,U plasma Power density 3 10 14 W/cm 2 Ion density 10 21 cm -3 Electron temperature 250-300eV Radiance 0.5 TW/mm 2 sr (160MW/mm 2 sr in 2% band at 13.5nm WL)
EUV (13.5nm wavelength) lithography chosen for nano features microchip production HP NOW EUV for 22 nm HVM EUV source for HVM & actinic mask inspection - a key challenge facing the industry
EUV Light Source Sn, Xe, Li high energy density plasma (T e =20-40eV) - EUV light source in narrow 2% band around 13.5nm wavelength LPP & DPP - methods to produce the the right conditions for HED plasma LPP combined NdYAG +CO 2 I = 10 11 W/cm 2 T e = 40eV N e =10 19-10 21 cm -3 DPP DPP micro plasma j = 1-10 MA/cm 2 T e = 20-30eV N e =10 15-10 17 cm -3 For HVM - 200-500 W of in-band power @ IF with etendue < 3mm 2 sr For mask inspections ABI AIMS APMI 10 100 1000 W/mm 2 sr of time-average at-wavelength radiance @ IF (up to 1-2 MW/mm 2 sr of peak value at source) kw (source) W (IF) is the source of the problem - Z * MHD code modeling
ZETA Z * RMHD Code Z * BME complete physical model TABLES nonlte atomic & spectral data (Te,ρ,U) Spectral postprocessin g RMHD (r,z+φ) with: spectral multigroup radiation transport in nonlte; nonstationary, nonlte ionization; sublimation condensation; energy supply (electric power, laser) etc DPP simulation in real geometry LPP Data output: r,z,v,t e,i,ρ,e,b,z,u ω, etc; visualization EMHD or 3D PIC with: ionization of weekly ionized plasma Heat flux postprocessing
ZETA Z * RMHD Code Z * BME effective numerical algorithms & schemes Numeric al diffusion! Adaptive grid? Detailed grid Euler variables Small time step! ( zero for plasma in magnetic field) Explicit scheme is stable conditionally RMHD LAGRANGE- EULER VARIABLES COMPLETELY CONSERVATIVE, IMPLICIT SCHEME PHYSICAL SOLUTION Grid crossing! Lagrange variables Adaptive grid? Non-conservative scheme No energy balance!
EUV Brightness Limit of a Source The intensity upper Planckian limit of a single spherical optically thick plasma source in Δλ/λ=2% band around λ=13.5nm I 2 2hc Δλ / λ 72 2 = ( MW / mm sr) 4 hc 92 λ λt T ( ev ) e 1 e Source with pulse duration τ and repetition rate f yields the time-average radiance L =I (τ f) At T 22eV L 1.1(W/mm 2 sr) τ(ns) f(khz) For τ =20 50ns L = 20 50 (W/mm 2 sr)/khz. 1 EUV Radiance, MW/mm2 sr 10 2 10 1 10 0 10-1 10-2 10-3 10-4 10-5 tin Z* Scan 10-18 10-16 10-14 10-12 10-10 10-8 10-6 10-4 10-2 Effective Depth (rho2*r), gg2/cm3 2 5 R=0.04mm R=0.08mm R=0.16mm R=0.31mm R=0.625mm R=1.25mm R=2.5mm R=5mm Plasma self-absorption defines the limiting brightness of a single EUV source and required radiance The plasma parameters where EUV radiance is a maximum are not the same as that when the spectral efficiency is a maximum. - the Conversion Efficiency of a single. source decreases if the in-band EUV output increases (at the same operation frequency) tin g 2 /cm 5
EUV IF Power Limitation: prediction vs. observation Low temperature Xenon plasma EUV emission xenon Xenon plasma parameter scan with Z*-code showing the inband radiance limitation from XeI-XeXI ions Experimental observation of limitation of the inband EUV power at IF from xenon DPP source [M. Yoshioka et al. Alternative Litho. Tech. Proc. of SPIE, vol. 7271 727109-1 (2009)]
Bright EUV Emission from highly charged xenon ions Tokamak experimental data T Kato et al. J. Phys. B: At. Mol. Opt. Phys. 41 (2008) There are two regimes in transparent plasma of xenon: Low - Temperature (LT) with XeXI and High - Temperature (HT) with XeXVII-XeXXX ions contributing into 2% bandwidth at 13.5nm. For small size xenon plasma, the maximum EUV radiance in the HT can exceed the tin plasma emission xenon XeXXII - XeXXX produce bright 4f-4d*, 4d-4p*, 5p-4d* [White, O Sulivan] (3d n 4f 1 + 3d n 4p 1 3d n 4d 1 ) satellites in EUV range near 13.5nm XeXXII has ionization potential 619eV HT LT Z* Scan
High Degree Xenon Ionization - in plasma with fast electrons Relative ionic fraction Ion charge Calculated ionic fractions without and with fast electrons of 5keV energy and various fraction (0.5%-2%) Plasma temperature T = 40 ev Electron density N e =10 17 cm -3
EUV Emission of Highly Charged Xe Ions - from plasma with fast electrons T e =30eV 2% T e =80eV To produce the maximum EUV light power the double condition is required: + fast electrons have the energy of few kev to produce the highly charged ions + plasma has the temperature sufficient for the excitation of required transitions
EUV Emission of Highly Charged Xe Ions - from e-beam triggered discharge plasma EUV Measurement Capillary discharge. VUV spectrograph data Bright EUV emission in 2% band at 13.5 nm can be achieved from highly charged xenon ions in plasma with small percentage of fast electrons
Z* benchmarking of LPP source solid tin target at UCD Frame 001 02 May 2007 ZSTAR - code output, cell values Z(cm) t= 18.20 ns 0.25 0.2 Max.T e = 45eV 0.15 0.1-0.1-0.05 0 0.05 0.1 R(cm) Te(eV) 45.0 43.2 41.4 39.6 37.8 36.0 34.3 32.5 30.7 28.9 27.1 25.3 23.5 21.7 19.9 18.1 16.3 14.5 12.8 11.0 9.2 7.4 5.6 3.8 2.0 Simulations of LPP at different laser intensities 1.6 10 11 W/cm 2 (CE=2%) 1.9 10 11 W/cm 2 (CE=2.2%) Instability of the critical layer is observed Frame 001 02 May 2007 ZSTAR - code output, cell values Frame 001 02 May 2007 ZSTAR - code output, cell values UTA v.s. Experiment Z(cm) t= 18.65 ns 0.25 0.2 Max.T e = 51eV 0.15 0.1-0.1-0.05 0 0.05 0.1 R(cm) Te(eV) 51.0 49.0 46.9 44.9 42.8 40.8 38.8 36.7 34.7 32.6 30.6 28.5 26.5 24.5 22.4 20.4 18.3 16.3 14.3 12.2 10.2 8.1 6.1 4.0 2.0 Z(cm) 0.13 0.12 0.11 0.1 t= 18.65 ns Snap-shot of EUV emitter (zoomed) -0.02-0.01 0 0.01 0.02 R(cm) Geuv(MW/ccm) 1.9E+07 1.8E+07 1.7E+07 1.6E+07 1.6E+07 1.5E+07 1.4E+07 1.3E+07 1.3E+07 1.2E+07 1.1E+07 1.0E+07 9.7E+06 8.9E+06 8.2E+06 7.5E+06 6.7E+06 6.0E+06 5.2E+06 4.5E+06 3.7E+06 3.0E+06 2.2E+06 1.5E+06 7.5E+05
Combined Nd:YAG - CO 2 Laser System Collector Mirror Target Chamber sub-ns Nd:YAG laser (pre-pulse) Beam splitter EUV / 13.5nm ns-order CO 2 laser (main pulse) Sn Droplet Target
LPP Dynamics & EUV Emission Sn 20μm diameter tin droplet. 2.5mJ YAG laser prepulse energy. Main laser pulse: CO 2, 50mJ, 15ns, 100 μm FWHM spot size. during pre- and main laser pulse The delay time between laser pulses is 75ns.
Conversion Efficiency vs. pre-pulse to pulse delay time Target: 20μm diameter Sn droplet Pre-pulse laser: Nd:YAG, 10ns fwhm, 20μm spot size, pulse energy 2.5 & 5mJ Main pulse: CO 2 -laser, 15, 37 and 60ns fwhm, 100μm spot size 2% 100mJ, 15ns EUV brightness up to 10 W/mm 2 sr khz CE (in 2%) 200mJ, 50ns 200mJ, 50ns 100mJ 37ns
Capillary Discharge EUV Source electron beam and ionization wave Ionization cross-section of argon atoms Pre-ionization in capillary discharge (ion density n i ): - axial beam of run-away electrons, - ionization of the gas by beam and secondary electrons, - the ionization wave forces out the electric field
Capillary Discharge EUV Source increasing ionization degree effect At EUV emission maximum ρ =5 10-7 g/cm 3, Т е =18eV. Without taking into account of fast electrons the plasma ionization degree is <Z>=7.3; EUV yield is 6μJ. Plasma density dynamics 3D volumetric compression WITH 0.1% of fast electrons <Z>=8.8; EUV yield is 30μJ (26 μj in experiment).
Gen II EUV Source - characteristics from Z* modelling 19kV charge, 1.2 nf capacitor >19kV charge energy scan E EUV =56μJ/shot P =56mW/kHz in-band In-band EUV EUV energy energy per per shot, shot, μ J mj 250 200 150 100 50 Energy scan calculated (in 2% band) Irradiance at peak signal (x 10 17 ph/cm 2 /s) 0 0 100 200 300 400 500 Stored energy, mj 2,5 2,0 1,5 1,0 0,5 peak irradiance linear fit of data 0,0 0,20 0,22 0,24 0,26 0,28 0,30 Stored energy (J) Experimental energy scan (20% band)
Next Generation Modelling Tools - FP7 IAPP project FIRE Theoretical models and robust modeling tools are developed under international collaboration in the frames of European FP7 IAPP project FIRE The FIRE project aims to substantially redevelop the Z* code to include improved atomic physics models and full 3- D plasma simulation of plasma dynamics spectral radiation transport non-equilibrium atomic kinetics with fast electrons transport of fast ions/electrons condensation, nucleation and transport nanosize particles. Modelling can be the key factor to scientific and technological solutions in EUVL source optimization with fast particles and debris to solve current EUVL source problems as well as extending their application to 22nm and beyond. The research and transfer of knowledge is focused on two major modeling applications; EUV source optimization for lithography and nanoparticle production for nanotechnology. Theoretical modelling will be benchmarked by LPP and DPP experiments
Acknowledgement R&D team & collaborators R&D team of EPPRA and Nano UV Pontificia Universidad Catolica de Chile RRC Kurchatov Institute, Moscow, Russia Keldysh Institute of Applied Mathematics RAS, Moscow, Russia University College Dublin King s College London EUVA, Manda Hiratsuka, Japan Sponsors - EU & French Government ANR EUVIL FP7 IAPP OSEO ANVAR RAKIA EUV LITHO, Inc.