Modelling of high intensity EUV light sources based on

laser- & discharge- produced plasmas

Sergey V. Zakharov +, Peter Choi, Vasily S. Zakharov

NANO‐UV sasEPPRA sas

+ also with RRC Kurchatov Institute, Moscow, Russia

COPYRIGHT 2010 NANO‐UV

2010 International

Workshop on EUV

Lithography June 21-25

Maui, Hawaii, USA

OUTLINE

High energy density plasma in EUVL

ZETA→Z*→Z*BME RMHD codes

Non-equilibrium plasma radiation kineticsplasma radiance limithighly charged Xe ion EUV emission

LPP & Combined Nd:YAG-CO2 laser pulse

Nano-UV source modelling for EUV andsoft X-ray source

Modelling tool development in FIRE-project

COPYRIGHT 2010 NANO‐UV

2010 International

Workshop on EUV

Lithography June 21-25

Maui, Hawaii, USA

High energy densitylaser or magnetically driven heavy ion plasmas

Z-pinch

Z –machine 20MA W, Xe … plasma

Current density 108-109 A/cm2

Ion density 1019-1020cm-3

Electron temperature 300-600eVEmission energy 2MJRadiance 1TW/mm2sr

(200MW/mm2sr in 2% band at 13.5nm WL)

Hohlraum target

Laser energy 1.8MJ Au,U … plasma

Power density 3·1014 W/cm2

Ion density 1021cm-3

Electron temperature 250-300eVRadiance 0.5 TW/mm2sr

(160MW/mm2sr in 2% band at 13.5nm WL)

COPYRIGHT 2010 NANO‐UV

2010 International

Workshop on EUV

Lithography June 21-25

Maui, Hawaii, USA

EUV (13.5nm wavelength) lithographychosen for nano features microchip production

HP

EUV source for HVM & actinic mask inspection- a key challenge facing the industry

NOWEUV for 

22 nm HVM

COPYRIGHT 2010 NANO‐UV

2010 International

Workshop on EUV

Lithography June 21-25

Maui, Hawaii, USA

EUV Light Source• Sn, Xe, Li … high energy density plasma (Te=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

‐ kW (source) ⇒W (IF) is the source of the problem -

combined NdYAG +CO2

• For HVM - 200-500 W of in-band power @ IF with etendue < 3mm2sr • For mask inspections ABI→AIMS→APMI – 10 →100 →1000

W/mm2·sr of time-average at-wavelength radiance @ IF (up to 1-2 MW/mm2·sr of peak value at source)

DPP

Z * MHD code modeling

LPPmicro plasmaDPP

I = 1011 W/cm2

Te = 40eVNe =1019-1021 cm-3

j = 1 - 10 MA/cm2

Te = 20-30eVNe =1015-1017 cm-3

COPYRIGHT 2010 NANO‐UV

2010 International

Workshop on EUV

Lithography June 21-25

Maui, Hawaii, USA

ZETA → Z* RMHD Code → Z* BMEcomplete physical model

DPPsimulation

in real geometry

LPP

Data output:r,z,v,Te,i ,ρ,E,B,Z,Uω, etc;visualization

RMHD (r,z+φ) with: • spectral multigroup radiation transport in nonLTE;

• nonstationary, nonLTE ionization; • sublimation – condensation;• energy supply (electric power, laser)• etc

TABLESnonLTE atomic &

spectral data(Te,ρ,U)

EMHD or 3D PIC with:ionization of weekly

ionized plasma

Spectral postprocessin

g

Heat flux postprocessing

COPYRIGHT 2010 NANO‐UV

2010 International

Workshop on EUV

Lithography June 21-25

Maui, Hawaii, USA

No energy balance!

Numerical

diffusion!

Adaptive grid

Detailed grid?

Adaptive grid

?

Lagrange variables

Gridcrossing

!

RMHD LAGRANGE-EULER

VARIABLES

COMPLETELY CONSERVATIVE,

IMPLICIT SCHEME

Small time step! (→zero for plasma in magnetic field)

Euler variables Explicit scheme is stable conditionally

Non-conservative scheme

PHYSICALSOLUTION

ZETA → Z* RMHD Code → Z* BMEeffective numerical algorithms & schemes

COPYRIGHT 2010 NANO‐UV

2010 International

Workshop on EUV

Lithography June 21-25

Maui, Hawaii, USA

10-5

10-4

10-3

10-2

10-1

100

101

102

10-18 10-16 10-14 10-12 10-10 10-8 10-6 10-4 10-2

R=0.04mmR=0.08mmR=0.16mmR=0.31mmR=0.625mmR=1.25mmR=2.5mmR=5mm

EUV

Rad

ianc

e, M

W/m

m2

sr

Effective Depth (rho2*r), g2/cm3

tin

tin

EUV Brightness Limit of a Source

.- the Conversion Efficiency of a single source decreases if the in-band EUV output increases

(at the same operation frequency)

Z* Scan

g2/cm5

g2/cm5

• The intensity upper Planckian limit of a single spherical optically thick plasma source in Δλ/λ=2% band around λ=13.5nm

• 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/mm2 sr)·τ(ns)·f(kHz)• For τ =20÷50ns L = 20÷50 (W/mm2 sr)/kHz.

• 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.

)/(72/2 2

)(924

2

11srmmMWhcI

ee eVTThc

−≈

−

Δ=

λ

λλλ

COPYRIGHT 2010 NANO‐UV

2010 International

Workshop on EUV

Lithography June 21-25

Maui, Hawaii, USA

EUV IF Power Limitation: prediction vs. observation

• Low temperature Xenon plasma EUV emission

Experimental observation of limitation of the in-band EUV power at IF from xenon DPP source[M. Yoshioka et al. Alternative Litho. Tech. Proc. of SPIE, vol. 7271 727109-1 (2009)]

Xenon plasma parameter scan with Z*-code showing the in-band radiance limitation from XeI-XeXI ions

xenon

COPYRIGHT 2010 NANO‐UV

2010 International

Workshop on EUV

Lithography June 21-25

Maui, Hawaii, USA

T Kato et al. J. Phys. B: At. Mol. Opt. Phys. 41 (2008)

LT

xenon

HT

Z* Scan

• XeXXII - XeXXXproduce bright 4f-4d*, 4d-4p*, 5p-4d* [White, O’Sulivan] (3dn4f1 + 3dn4p1 →3dn4d1) satellites in EUV range near 13.5nm

• XeXXII has ionization potential 619eV

Bright EUV Emission from highly charged xenon ions

Tokamak experimental data • 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

COPYRIGHT 2010 NANO‐UV

2010 International

Workshop on EUV

Lithography June 21-25

Maui, Hawaii, USA

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 densityNe=1017 cm-3

Rel

ativ

e io

nic

frac

tion

High Degree Xenon Ionization- in plasma with fast electrons

COPYRIGHT 2010 NANO‐UV

2010 International

Workshop on EUV

Lithography June 21-25

Maui, Hawaii, USA

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 plasma with fast electrons

Te=30eV2%

Te=80eV

COPYRIGHT 2010 NANO‐UV

2010 International

Workshop on EUV

Lithography June 21-25

Maui, Hawaii, USA

EUV Emission of Highly Charged Xe Ions- from e-beam triggered discharge plasma

EUV MeasurementCapillary 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

COPYRIGHT 2010 NANO‐UV

2010 International

Workshop on EUV

Lithography June 21-25

Maui, Hawaii, USAR(cm)

Z(cm

)-0.02 -0.01 0 0.01 0.02

0.1

0.11

0.12

0.13Geuv(MW/ccm)

1.9E+071.8E+071.7E+071.6E+071.6E+071.5E+071.4E+071.3E+071.3E+071.2E+071.1E+071.0E+079.7E+068.9E+068.2E+067.5E+066.7E+066.0E+065.2E+064.5E+063.7E+063.0E+062.2E+061.5E+067.5E+05

t= 18.65 ns

Frame 001 ⏐ 02 May 2007 ⏐ ZSTAR - code output, cell values

Z* benchmarking of LPP source solid tin target at UCD

UTA v.s. Experiment R(cm)

Z(cm

)

-0.1 -0.05 0 0.05 0.1

0.1

0.15

0.2

0.25Te(eV)

51.049.046.944.942.840.838.836.734.732.630.628.526.524.522.420.418.316.314.312.210.28.16.14.02.0

t= 18.65 ns

Frame 001 ⏐ 02 May 2007 ⏐ ZSTAR - code output, cell values

R(cm)Z(

cm)

-0.1 -0.05 0 0.05 0.1

0.1

0.15

0.2

0.25Te(eV)

45.043.241.439.637.836.034.332.530.728.927.125.323.521.719.918.116.314.512.811.09.27.45.63.82.0

t= 18.20 ns

Frame 001 ⏐ 02 May 2007 ⏐ ZSTAR - code output, cell values

Simulations of LPP at different laser

intensities1.6×1011W/cm2 (CE=2%)

1.9×1011W/cm2 (CE=2.2%)

Instability of the critical layer

is observed

Max.Te= 45eV

Max.Te= 51eV Snap-shot of EUV emitter

(zoomed)

COPYRIGHT 2010 NANO‐UV

2010 International

Workshop on EUV

Lithography June 21-25

Maui, Hawaii, USA

ns-order CO2 laser(main pulse)

sub-ns Nd:YAG laser(pre-pulse)

Target Chamber

Beam splitter

Collector Mirror

Sn Droplet Target

EUV / 13.5nm

Combined Nd:YAG - CO2 Laser System

COPYRIGHT 2010 NANO‐UV

2010 International

Workshop on EUV

Lithography June 21-25

Maui, Hawaii, USA

LPP Dynamics & EUV Emissionduring pre- and main laser pulse

20μm diameter tindroplet.

2.5mJ YAG laser pre-pulse energy.

Main laser pulse: CO2,50mJ, 15ns, 100 μmFWHM spot size.

The delay timebetween laser pulsesis 75ns.

Sn

COPYRIGHT 2010 NANO‐UV

2010 International

Workshop on EUV

Lithography June 21-25

Maui, Hawaii, USA

Target: 20μm diameter Sn dropletPre-pulse laser: Nd:YAG, 10ns fwhm, 20μm spot size, pulse energy 2.5 & 5mJMain pulse: CO2-laser, 15, 37 and 60ns fwhm, 100μm spot size

Conversion Efficiency vs. pre-pulse to pulse delay time

2%

CE

(in2%

)

EUV brightness up to 10 W/mm2 sr kHz

•200mJ, 50ns

100mJ, 15ns

100mJ 37ns

• 200mJ, 50ns

COPYRIGHT 2010 NANO‐UV

2010 International

Workshop on EUV

Lithography June 21-25

Maui, Hawaii, USA

Pre-ionization in capillary discharge (ion density ni ):- axial beam of run-away electrons,

- ionization of the gas by beam and secondary electrons,- the ionization wave forces out the electric field

Ionization cross-section of argon atoms

Capillary Discharge EUV Sourceelectron beam and ionization wave

COPYRIGHT 2010 NANO‐UV

2010 International

Workshop on EUV

Lithography June 21-25

Maui, Hawaii, USA

At EUV emission maximumρ =5⋅10-7g/cm3, Те=18eV.

Without taking into account of fast electrons the plasma ionization degree is <Z>=7.3;EUV yield is 6μJ.

WITH 0.1% of fast electrons <Z>=8.8;

EUV yield is 30μJ (26 μJin experiment).

Capillary Discharge EUV Sourceincreasing ionization degree effect

3D volumetric compressionPlasma density dynamics

COPYRIGHT 2010 NANO‐UV

2010 International

Workshop on EUV

Lithography June 21-25

Maui, Hawaii, USA

19kV charge, 1.2 nF capacitor >19kV charge energy scanEEUV =56μJ/shotP =56mW/kHz

0

50

100

150

200

250

0 100 200 300 400 500

In-b

and

EUV

ener

gy p

er s

hot,

mJ

Stored energy, mJ

in-b

and

EUV

ener

gy p

er s

hot, μ

J

Gen II EUV Source- characteristics from Z* modelling

0,20 0,22 0,24 0,26 0,28 0,300,0

0,5

1,0

1,5

2,0

2,5 peak irradiance linear fit of data

Irrad

ianc

e at

pea

k si

gnal

(x

1017

ph/

cm2 /s

)

Stored energy (J)

Energy scan calculated

(in 2% band)

Experimental energy scan(20% band)

COPYRIGHT 2010 NANO‐UV

2010 International

Workshop on EUV

Lithography June 21-25

Maui, Hawaii, USA

plasma dynamicsspectral radiation transportnon-equilibrium atomic kinetics with fast electronstransport of fast ions/electrons

condensation, nucleation and transport nanosize particles.

• Modelling can be the key factor to scientific and technological solutions in EUVLsource optimization with fast particles and debris to solve current EUVL sourceproblems as well as extending their application to 22nm and beyond.

• The research and transfer of knowledge is focused on two major modelingapplications;

EUV source optimization for lithography andnanoparticle production for nanotechnology.

• Theoretical modelling will be benchmarked by LPP and DPP experiments

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

COPYRIGHT 2010 NANO‐UV

2010 International

Workshop on EUV

Lithography June 21-25

Maui, Hawaii, USA

• 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.

Acknowledgement