SO-P22
2007 International EUVL Symposium, Sapporo, JAPAN
Performance of Forced Recombination
Lithium Target driven by Nd:YAG Laser
Shuji MIYAMOTO, Sho AMANO, Akihisa NAGANO
Kazuya MASUDA Tsuguhisa SEKIOKA
and Takayasu MOCHIZUKI
Laboratory of Advanced Science and Technology for Industry
University of Hyogo
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".
OUT
LINE
Laser produced lithium plasma for EUV source
High purity EUV emission from
lithium target
Study of laser produced
plasma EUV source using
lithium target.
6
8
University
of Hyogo
10
12 14 16 18
Wavelength (nm)
Aiming :
Direct emission
- Laser wavelength
dependence
- Ion debris characteristics
19.9nm(Li+,1s2-1s2p)
17.8nm(Li+,1s2-1s3p)
13.5nm(Li2+,1s-2p)
11.39nm(Li2+,1s-3p)
10.8nm(Li2+,1s-4p)
Intensity (a.u)
13.5nm：intense Lyman-α emission
20
22
Forced recombination
- CE with practical setting
direct+recombination
- Ion debris reduction
2007 International EUVL Symposium
2007.10.28-31, Sapporo, JAPAN
Ionization & kinetic energy vs EUV
radiation
Ei : the ionization energy
ηsp : the spectral efficiency
of EUV
)*+!
&##
'"#
EUV
'##
)*+&
"#
)*+'
#
#(#
University
of Hyogo
'(#
Ionization
Energy ,*-$.*/01-$234
56-*78.*6-01-$234
Ek : the plasma kinetic
energy
Ionization & Kinetic Energy
Er : the radiation energy
&"#
&(#
2007 International EUVL Symposium
2007.10.28-31, Sapporo, JAPAN
!###
Kinetic Energy
EUV
!"#$%
!##
eV
!$##
Lithium(25eV)
EL : the absorbed energy of
the incident laser
!"##
()*!#
%##
()*+
&##
()*%
"##
()*,
Ionization Energy
Ionization
Energy
( Er %
E L ! Ek ! Ei
## = "sp
CE = "sp &&
EL
' EL $
Xenon(30eV)
16Ionization & Kinetic Energy
LITHIUM
TARGET
$##
#
#'#
!'#
$'#
WAVELENGTH
EFFECT : Li
Laser wavelength dependenc of plane lithium target
Nd:YAG Laser
1ω:1064nm/10ns/0.1~0.5J
2ω:532nm/10ns/0.1~0.5J
3ω:355nm/8ns/0.15~0.25J
Flying
Circus
Faraday
cup
GI Spectrometer
60°
EUV
monitor
Vaccum ~4
×10-3Pa
University
of Hyogo
Spot size (laser intensity)
was controlled by moving
the laser focusing lens
35°
15° -10°
+ : out focus
Focusing lens position (LP)
- : in focus
EUV monitor
70°
Plane
lithium
X-ray photo diode
Ions
EUV
debris
2007 International EUVL Symposium
2007.10.28-31, Sapporo, JAPAN
magnet
magnet
Mo/Si mirrer
WAVELENGTH
EFFECT : Li
Laser wavelength dependence
2ω laser irradiation shows maximum CE
CE: 2ω > 1ω > 3ω
2.5
2ω:
~2.3%
CE [%/2! ]
Conversion Efficiency[%/2π]
3.0
1ω:
~1.7%
Qualitatively agree with
data of Cymer [1]
◇ 1ω 0.5J
◆ 1ω 0.3J
○ 2ω 0.5J
● 2ω 0.25J
△ 3ω 0.25J
3ω:
~1.6%
2.0
1.5
1.0
0.5
0.0
9
10
10
10
11
12
10
10
2 2
[W/cm ] ]
LaserIntensity
intensity[W/cm
13
10
[1] D. Myers et al. 3rd EUVL Symposium, Miyazaki (Nov. 2, 2004)
University
of Hyogo
2007 International EUVL Symposium
2007.10.28-31, Sapporo, JAPAN
WAVELENGTH Li : ION
DEBRIS
EFFECT : Li
Ion debris spectrum from lithium target
irradiated by 2ω optimized irradiation
1ω:0.5J (~4x1010W/cm2)
2ω:0.5J (~4x1010W/cm2)
3ω:0.25J (~2x1010W/cm2)
1012
LP = -4
θ = 60º
10
Xe
12
Laser: 0°/1ω/0.5J
LP=-10
FC: 11.25°~
I=6x1010W/cm2
assume Z=2
10
11
10
10
10
9
10
1011
0
5
assume Z=1
30 3
10
15
20
25 30x10
Kinetic energy [keV]
13
Detection limit
1010
Kinetic energy [eV]
Maxmum ion energy 1ω > 2ω, 3ω
maxE
Li< ~1keV → about one order of
magnitude less than Xe and Sn target
University
of Hyogo
Ion number [/eV/sr]
Ion number [/eV/sr]
Fast ion spectrum
Ion number [/eV/sr]
13
1013
10
Sn
12
Laser: 45°/1ω/0.5J
LP=-4
FC: 45°
I=4x1010W/cm2
assume Z=2
10
11
10
10
10
9
10
0
2007 International EUVL Symposium
2007.10.28-31, Sapporo, JAPAN
2
3
10
4
6
8 10x10
Kinetic energy [keV]
Li : FORCED
RECOMBINATION
CRE model
Forced recombination lithium target
Emitte
13.5nm
Li2+
Li
Wall (Electron donor)
・Plasma confinement
・Forced recombination
Time resolved
EUV image
Li3+
Laser
Li
Wall
Observation
[1]R.Kodama and T.Mochizuki, Opt. Lett. 12, 990 (1987).
[2]S.Miyamoto, S.Amano et al., 4th EUVL Symposium, San Diego, Nov(2005).
t = 10 ns
[3]P.E.Nica, S.Miyamoto, et al., Appl. Phys. Lett., 89, pp.041501-1-041501-3(2006).
[4]S.Amano, S.Miyamoto et al., 5th International EUVL Symposium, Barcerona, Spain, Oct. 15-18, (2006).
[5]T.Sekioka, A.Nagano et al., Jpn. J. Appl. Phys., Vol.46, No.11, pp.L253-L255(2007).
[6]P.E.Nica, S.Miyamoto et al., Phys. Lett. A, 370, pp.154-157 (2007).
[7]A.Nagano, T.Inoue et al., Apll. Phys. Lett., 90, pp.151502-1-151502-3 (2007).
University
of Hyogo
2007 International EUVL Symposium
2007.10.28-31, Sapporo, JAPAN
mm
Li : FORCED
RECOMBINATION
Practical irradiation system of forced
recombination lithium target
Wall
Laser
Multilayered
mirror
Collection
solid angle
~4sr
University
of Hyogo
Intermediate
focus
Recombination
emission
Laser
Lithium
droplet or jet
target
Direct
emission
2007 International EUVL Symposium
2007.10.28-31, Sapporo, JAPAN
Li : FORCED
RECOMBINATION
Time Resolved EUV Emission Images
Laser: 1J / 5×1010 W/cm2 , Exposure 2ns
With wall
Li
Wall
1.3mm
mm
mm
mm
mm
mm
mm
mm
mm
mm
Without wall
Li
t = -10 ns
University
of Hyogo
t = 0 ns
Laser peak
mm
t = 10 ns
2007 International EUVL Symposium
2007.10.28-31, Sapporo, JAPAN
t = 20 ns
t = 30 ns
With wall
Frying
Circus
EUV emission from quasi-practical setting
Laser:135°/0.5J
~1012 W/cm2
80° 100°
45°
θ
55°
20°
EUV
monitor
0°
Li :
380µm
Without wall
-60°
Wall
Laser:-45°/0.5J
~1012 W/cm2
-30°
-10°
Li :
380µm
θ
University
of Hyogo
Conversion efficiency (a.u)
Li : FORCED
RECOMBINATION
EUV emission distribution
With Wall
Without Wall
Observation angle (deg.)
Without wall
0.7 ~1%
0°
30° EUV
monitor
With wall
1.3~1.6%
1.6~2 times improvement
2007 International EUVL Symposium
2007.10.28-31, Sapporo, JAPAN
Li : FORCED
RECOMBINATION
Conceptual estimation of EUV emission from
practical forced recombination target
Assume emission
only from wall
Total emission = direct + wall
90°
Laser
LP=0
Li
Emission
area
1mmφ
0°
1mm
0.38mm
block
Wall
r=0.2mm
target
use droplet target
EUV intensity [a.u/sr]
θ
0.3
Measured data
(recombination)
1.2~1.6%
Estimated
CE (both)
2.9~3.3 %
0.2
direct
0.1
No target
Li block
r = 0.2mm target
Wall
emission
0
-90
-50
0
50
Emission distribution θ[deg.]
University
of Hyogo
2007 International EUVL Symposium
2007.10.28-31, Sapporo, JAPAN
90
Li : FORCED
RECOMBINATION
Ion spectrum from forced recombination lithium
target
With wall
Faraday cup
140mm
65°
Laser:135°
0.5J
~1012 W/cm2
θ
0°
Li : 380µm
Wall
Without wall
Laser:-45°
0.5J
~1012 W/cm2
0°
Li : 380µm
θ
University
of Hyogo
Faraday cup
140mm, 20°
Ion number (/sr/eV)
1013
1012
Li ion spectrum
with wall
1011
LP=0
Assume Z=1
without wall
1010
109
Kinetic energy (eV)
Forced recombination target
reduces ion kinetic energy
2keV → 0.3keV at 1011 (/sr/eV)
2007 International EUVL Symposium
2007.10.28-31, Sapporo, JAPAN
Experimental Setup for debris measurements
Laser
Setup for ion debris
measurement
Electrostatic
energy
analyzer
Example of ion signal
Lens
MCP
$
Li plate
/0123453-657489:;
Li : ION
DEBRIS
+
,-!*
+
)*
%
,-*
,-!*
.*
'!$$
,-47>?637@4A3274BCD0248EF(#$"G3:;
45º
'($$
%
Target chamber
TMP
!"#
#"$
,-*
%"#
&$"$
&!"#
<-938=2;
Setup for neutral
debris measurement
MCP
TMP
pinhole
Deflecting
TMP
electrodes
Permanent magnet
(optional)
University
of Hyogo
Laser
0.5J/10ns/ f0.8mm
ESA
Electro Static energy Analyzer
Comstock AC-901
E(eV)/q=2.254×V(V)
TOF flight pass
MCP to Target= 800mm
2007 International EUVL Symposium
2007.10.28-31, Sapporo, JAPAN
Summary
1.Basic data of direct emission from lithium target
-mesured wavelength dependence of CE
2ω (~ 2.3％) ＞ 1ω (~ 1.7%) ＞ 3ω (~ 1.6%)
-measured wavelength dependence of ion energy
1ω：~ 1keV ＞ 2ω, 3ω : ~ 0.7keV
-about one order of magnitude less than Xe and Sn
2.Forced recombination target
-expected CE with using both the direct and the forced
recombination emission
1ω: 1.7% + 1.6% = 3.3%
2ω: 2.3% + 1.6% = 3.9%
University
of Hyogo
2007 International EUVL Symposium
2007.10.28-31, Sapporo, JAPAN