characterization and optimization of tin particle …...confidential spie advanced lithography 2011...
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Confidential
SPIE Advanced Lithography 2011
Tatsuya Yanagida, Hitoshi Naganoa, Yasunori Wada, Takayuki Yabu, Shinji Nagai,Georg Soumagne, Tsukasa Hori, Kouji Kakizakia, Akira Sumitani, Junichi Fujimotob,Hakaru Mizoguchib and Akira Endoc
EUVA, JapanaKOMATSU Ltd., JapanbGigaphoton Inc., JapancWaseda University, Japan
Characterization and optimization of tin particle mitigation and EUV conversion efficiency in a laser produced plasma EUV light source
[7969-100]
Copyright 2011 GIGAPHOTON INC. all rights reserved. 2 Mar. 2011 SPIE Advanced Lithography, [7969-100] 2
Outline
1. Introduction
2. Concept of Sn particle mitigation
3. Experimental setup
4. Experimental results
4-1. Sn fragment Imaging
4-2. LIF measurement of Sn neutrals
4-3. EUV CE measurements
5. Summary
Copyright 2011 GIGAPHOTON INC. all rights reserved. 2 Mar. 2011 SPIE Advanced Lithography, [7969-100] 3
SOR,HHGX-LaserLPP/DPP
Laser Produced Plasma (LPP)Discharge Produced Plasma(DPP)
Mo/Si Mo/Si multilayer mirror multilayer mirror (R=70%)(R=70%)IF (Intermediate focus)IF (Intermediate focus)
EUVL based on High vacuum environment, Multilayer coated reflective opticsEUV Lithography system
Copyright 2011 GIGAPHOTON INC. all rights reserved. 2 Mar. 2011 SPIE Advanced Lithography, [7969-100] 4
CO2 laser + Sn target+ Magnetic field plasma guiding
High power pulsed CO2 Laser
LPP EUV Light Source
High EUV powerLong collector mirror lifetimeEUV StabilityLow CoG / CoOReliability,・・・
Requirements for HVM EUV source
Sn target supply
Magnetic field plasma guiding
IF(Intermediate Focus)
EUVA LPP concept
Copyright 2011 GIGAPHOTON INC. all rights reserved. 2 Mar. 2011 SPIE Advanced Lithography, [7969-100] 5
Outline
1. Introduction
2. Concept of Sn particle mitigation
3. Experimental setup
4. Experimental results
4-1. Sn fragment Imaging
4-2. LIF measurement of Sn neutrals
4-3. EUV CE measurements
5. Summary
Copyright 2011 GIGAPHOTON INC. all rights reserved. 2 Mar. 2011 SPIE Advanced Lithography, [7969-100] 6
Characteristics of produced Sn particles (debris)
Fragments
Neutral atoms Ions
Velocity distribution
Ions Neutral atoms Fragments
Direction of expansion
Towards the laser incident direction All direction Same direction as
laser pulse
Velocity 10 - 100 km/s 5 - 40 km/s 0.01 - 0.5 km/s
Kinetic energy 60 - 6000 eV 15 - 980 eV -
Sn particles are classified into fragments, neutral atoms, ions
Copyright 2011 GIGAPHOTON INC. all rights reserved. 2 Mar. 2011 SPIE Advanced Lithography, [7969-100] 7
Concept of Sn particle mitigationIn our LPP system, Sn particles are reduced to practical levelby the following method,
Mass limited Sn supplyFragments are vaporized and ionized by the main pulse laser.Ions are trapped by the magnetic field and collected.Residual Sn particles are cleaned.
Masslimitedtarget
Pre-pulse laser
Fragments
Main pulse laser
Neutral atoms
Ions
Vaporized
Ionized
Mag
netic
shi
ed
Cle
anin
g
Col
lect
or m
irror
Res
idua
lpar
ticle
s
Copyright 2011 GIGAPHOTON INC. all rights reserved. 2 Mar. 2011 SPIE Advanced Lithography, [7969-100] 8
Subject of this workWe investigated behavior of Sn particles, and studied the optimization ofparticle mitigation condition with a compact EUV experimental system.
Fragments observation with a shadowgraph imaging (20 μm droplet target)
Neutral atoms imaging in a strong magnetic field by a laser induced fluorescence (LIF) method. (Planar target)
EUV Conversion Efficiency (CE) with smaller droplets are also optimized.
Copyright 2011 GIGAPHOTON INC. all rights reserved. 2 Mar. 2011 SPIE Advanced Lithography, [7969-100] 9
Outline
1. Introduction
2. Concept of Sn particle mitigation
3. Experimental setup
4. Experimental results
4-1. Sn fragment Imaging
4-2. LIF measurement of Sn neutrals
4-3. EUV CE measurements
5. Summary
Copyright 2011 GIGAPHOTON INC. all rights reserved. 2 Mar. 2011 SPIE Advanced Lithography, [7969-100] 10
Experimental setup of a compact EUV systemIt can simulate a same condition as our high-power EUV light source except for apulse repetition rate.
・System configurationDroplet generator, Pre-pulse laser, Main CO2 pulse laser, Magnetic fieldPulse repetition rate : 10Hz
・Measurement toolsShadowgraph for fragmentsLIF for neutral atomsEUV sensor(power, image, …)
Back
illuminator
CCD
cameraEUV
sensor
Drive laser
Sn dropletLIFcamera
EUV/DebrisMeasurementport
Corrector mirror
Intermediate focus
EUV/DebrisMeasurementport
Copyright 2011 GIGAPHOTON INC. all rights reserved. 2 Mar. 2011 SPIE Advanced Lithography, [7969-100] 11
Outlook of the EUV system
Upper view
Drive laser
Droplet
Intermediate focus direction
LIFmeasurementEUV sensor
Size : 2 m X 3 m X 2 m
Copyright 2011 GIGAPHOTON INC. all rights reserved. 2 Mar. 2011 SPIE Advanced Lithography, [7969-100] 12
Outline
1. Introduction
2. Concept of Sn particle mitigation
3. Experimental setup
4. Experimental results
4-1. Sn fragment Imaging
4-2. LIF measurement of Sn neutrals
4-3. EUV CE measurements
5. Summary
Copyright 2011 GIGAPHOTON INC. all rights reserved. 2 Mar. 2011 SPIE Advanced Lithography, [7969-100] 13
Shadowgraph imaging for Sn fragment measurementTime resolution ~ 40 nsSpatial resolution ~ 6 μm60 degree observation angle to laser axis
Pre-pulse
Main pulse60°
Camera + Lens
Flash illuminator
100 μm
Example of shadowgraph image( 20μm droplet)
Copyright 2011 GIGAPHOTON INC. all rights reserved. 2 Mar. 2011 SPIE Advanced Lithography, [7969-100] 14
a) without main-pulse laser
Pre-pulse irradiation Time
Main pulse laser/ EUV emission After EUV emission
b) with main-pulse laser
Sn fragments after laser irradiation
20 μm droplet, pre-pulse + main-pulse lasersFragments generated after pre-pulse irradiation.Quite a few fragments still remain without vaporization after EUV emission.
Wrong laser condition
Copyright 2011 GIGAPHOTON INC. all rights reserved. 2 Mar. 2011 SPIE Advanced Lithography, [7969-100] 15
Sn fragments after laser irradiation
Fragments are vanished after EUV emission.We believe almost all of the fragments are vaporized, then probably ionized.
Appropriate laser condition
a) without main-pulse laser
Pre-pulse irradiation Time
Main pulse laser/ EUV emission After EUV emission
b) with main-pulse laser
Fragments are vanished
LASER
Copyright 2011 GIGAPHOTON INC. all rights reserved. 2 Mar. 2011 SPIE Advanced Lithography, [7969-100] 16
Outline
1. Introduction
2. Concept of Sn particle mitigation
3. Experimental setup
4. Experimental results
4-1. Sn fragment Imaging
4-2. LIF measurement of Sn neutrals
4-3. EUV CE measurements
5. Summary
Copyright 2011 GIGAPHOTON INC. all rights reserved. 2 Mar. 2011 SPIE Advanced Lithography, [7969-100] 17
Laser induced fluorescence (LIF) imaging for Sn atoms
λfluorescence
0 cm-1
λabsorption
5p6s3Po1
5p2 3P0
5p2 3P1
286.3 nm 317.5 nm
Energy level of Sn atom
Advantages
Spectrally selective pumping and observation
High sensitivity
Cross sectional imaging with a sheet laser beam
Copyright 2011 GIGAPHOTON INC. all rights reserved. 2 Mar. 2011 SPIE Advanced Lithography, [7969-100] 18
laser
Surface of a Sn plate
a) Without the magnetic field b) With the magnetic field
B-field
Isotropic expansion Sn atoms strongly converge on the direction of the magnetic field.
2D LIF image of Sn atom distribution at 1 μs after laser irradiation
Sn neutral distribution under strong magnetic fieldPlanar target + pre-pulse laser with / without magnetic fieldMagnetic field helps guiding the Sn particles of not only the charged particle
but also the neutral atom.
Copyright 2011 GIGAPHOTON INC. all rights reserved. 2 Mar. 2011 SPIE Advanced Lithography, [7969-100] 19
Outline
1. Introduction
2. Concept of Sn particle mitigation
3. Experimental setup
4. Experimental results
4-1. Sn fragment Imaging
4-2. LIF measurement of Sn neutrals
4-3. EUV CE measurements
5. Summary
Copyright 2011 GIGAPHOTON INC. all rights reserved. 2 Mar. 2011 SPIE Advanced Lithography, [7969-100] 20
Droplet size vs. EUV CE
Pre-pulse laser irradiation is a key parameter for a higher EUV CE.
EUV CE reached to 3.4% for a 20 μm droplet by optimizing the pre-pulse laser conditions.
0
0.5
1
1.5
2
2.5
3
3.5
4
10 15 20 25 30 35 40 45 50
EUV
CE
(%)
Droplet diameter (μm)
Without a pre-pulse irradiation
With a pre-pulse irradiation
With a Improved pre-pulse irradiation
Copyright 2011 GIGAPHOTON INC. all rights reserved. 2 Mar. 2011 SPIE Advanced Lithography, [7969-100] 21
0
0.2
0.4
0.6
0.8
1
1.2
0 20 40 60 80 100 120 140
EUV
cle
an p
ulse
ene
rgy
(mJ)
CO2 pulse energy (mJ)
100
120
80
60
40
20
0EUV
cle
an p
ower
ass
umin
g a
100k
Hz
oper
atio
n (W
)
EUV CE doesn’t saturate at leastup to 134mJ CO2 laser input.
Clean EUV power of 100 W isexpected for our developing system with a pulse repletion rate of 100kHz.
CO2 laser pulse energy vs. EUV pulse energy
Copyright 2011 GIGAPHOTON INC. all rights reserved. 2 Mar. 2011 SPIE Advanced Lithography, [7969-100] 22
SummaryThe optimization of tin debris mitigation and EUV CE with the compact EUV generation system is presented.
1. Sn fragments generated from the 20 μm diameter droplet was vaporized almost entirely by the laser optimization.
2. Sn neutrals generated after the pre-pulse irradiation converge to themagnetic field. (planar target)The magnetic field is beneficial to the Sn particles guiding of not only the ions but also the neutrals.
3. No EUV CE degradation even for 20 μm diameter dropletMaximum EUV CE of 3.4% for 20 μm diameter dropletClean EUV power of 100 W is expected for our developing system.
Copyright 2011 GIGAPHOTON INC. all rights reserved. 2 Mar. 2011 SPIE Advanced Lithography, [7969-100] 23
Acknowledgement
A part of this work was supported by the New Energy andIndustrial Technology Development Organization (NEDO),Japan.