
Providing
Light Source
Solutions
Dense Plasma Focus as a
Light Source for Production
EUV Lithography
I.V. Fomenkov, W.N. Partlo, R.M. Ness,
R.I. Oliver S.T. Melnychuk, J.E. Rauch
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Outline
! Research areas and personnel
! Intermediate and Ultimate Specifications
! 4th Generation DPF System Description
! Measured 13.5nm In-band Absolute Emission with Xenon
! Measured Out-of-band Emission with Xenon
! Pinhole Camera EUV Source Images
! Grazing Incidence Collector update
! Initial results with foil trap debris mitigation
! Conclusions
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Cymer EUV Program Personnel Resources
Overall and Metrology:
Igor Fomenkov,
~ 9 years
Pulse power:
Richard Ness,
~ 5 years
Plasma initiation:
Steve Melnychuk,
~ 1 year
Thermal engineering:
Roger Oliver,
~ 4 years
Collector development:
John Rauch,
~ 1 year
Debris mitigation :
Oleh Khodykin,
~ 1/2 year
European scientific liaison:
Norbert Bowering,
~ 1/4 year
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Intermediate and Ultimate Specifications
Dem onstrated
collectable EUV
power in a 2%
bandwidth
Available
collection solid
angle
Source em ission
volum e
dim ensions
Dem onstrated
m axim um
repetition rate
Dem onstrated
steady-state
repetition rate
Dissipated total
power at steadystate repetition
rate
Now
In 1 year
In 2 years
Ultim ate
0.23 W @ 50Hz
(CW )
2.3 W @ 500Hz
(CW )
9 W @ 2000Hz
(CW )
60W @ 5000Hz
(CW )
4.5 W @ 1000Hz
(burst)
2π str
(1.8 str planned)
9 W @ 2000Hz
(burst)
2π str
(1.8 str planned)
18 W @ 4000Hz
(burst)
2π str
(1.8 str planned)
2π str
(1.8 str planned)
0.25m m X
1.7m m
0.25m m X
1.7m m
0.10m m X
?? m m
0.10m m X
?? m m
2500Hz
2500Hz
4000Hz
5000Hz
50Hz
500Hz
2000Hz
5000Hz
500W
5000W
20,000W
50,000W
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Com m erc
ial tool
Requirem ents
50-150W
≥5000Hz
Intermediate and Ultimate Specifications
Source-facing
condenser
lifetime (pulses
to 10%
reflectance loss)
Pulse-to-pulse
spatial stability
Pulse-to-pulse
energy stability
Pulse-to-pulse
angular stability
Pulse-to-pulse
pointing
stability
Key risk areas
0.6M
>>60M
Unknown
Unknown
> 100%
>100%
<100%
<100%
3σ=27%
3σ=27%
3σ=5%
3σ=2%
isotropic
isotropic
isotropic
isotropic
isotropic
isotropic
isotropic
isotropic
Debris &
Thermal
Debris &
Thermal
Debris &
Thermal
Debris &
Thermal
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1 year or
160B
pulses
≤2%
Schematic of 4th Generation DPF System
Pinch
Buffer Gas (He)
Anode
Cathode
Initial Plasma Sheath
Insulator
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Source Gas (Xe)
HV
Principle of Operation
!
The higher forces near the central
axis form a cone shaped plasma
sheath.
!
Once plasma reaches end of the
anode, inward forces cause
compression.
F
t3 > t2 > t1
J
F
t3
t2
t1
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F
J
J
J
F
F
J
J
Waveshapes for 4th Generation DPF
1.2
6
12.8J Input
1.0
4
0.8
3
0.6
2
0.4
1
0.2
0
0.0
-1
-2
-3
-100
BLACK: C2 Voltage
RED: Anode Voltage
BLUE: EUV Emission
-0.2
-0.4
2.7J Recovered
-0.6
-50
0
50
100
150
Time (ns)
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200
250
300
350
EUV Emission (Normalized)
Voltage (kV)
5
Experimental Setup
He Gas
Feed
Xe Gas
Feed
Mass
Flow
Controller
Solid
State
Pulsed
Power
Pi
Ca nho
m le
er
a
Pressure
Monitor
Spectrometer
Anode
Pre-ionization
Electrodes
6”TurboPump
Pump
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oot e
h
P iod oil
d eF
B
w/
! Vessel kept at constant pressure
! Xe controlled through MFC
! Measurement region differentially
pumped
Experimental Setup
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Measured EUV Spectrum of Xenon
1.0
2.5
Spectrometer EMT Signal (V)
2.0
Xe IX
0.8
Xe XI Lines
Xe X Lines
1.5
0.6
1.0
0.4
0.5
0.2
0.0
0.0
11
12
13
14
W avelength (nm)
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15
16
17
Published Reflectivity of Mo/Si Mirror
Ionization Energy for Xe X = 202eV
13.5 nm In-band Energy Measurement
Xe Gas
Feed
He Feed
ML dielectric
mirror. Radius of
curvature= 1m
IRD un-coated
photodoide
Assumed Ref=67%
Mass
Flow
Controller
5 cm
P=6.0 mTorr
P=1.4
Torr
6” TurboPump
5 mm Diameter
Aperture
Aperture
1 µm Be Foil on linear
motion feedthru
Pump
T(calc)=17.4%
T(meas)=25.1%
92 cm
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In-band Emission Efficiency vs. Input Energy
30
0.30
Emission into 2π Str, 2% Bandwidth (20 Hz operation)
20
0.20
15
0.15
Maximum Input Energy
of 3rd Generation DPF
10
0.10
5
0.05
0
0.00
4
5
6
7
8
Input Energy (J)
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0.25
BLACK: Energy
RED: Efficiency
9
10
11
Efficiency (%)
Measured Energy (mj)
25
Emission Stability at 20Hz
140
Energy at 13.5 nm (a.u)
120
100
80
60
Standard Deviation = 9.5 %
40
20
0
0
20
40
60
Pulse number
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80
100
In-Band Emission at 1KHz
140
EUV Energy (Norm).
120
100
80
60
Burst Power = 25 Watt
40
20
Emission into 2π Str, 2% Bandwidth
0
0
50
100
150
Pulse Number
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200
250
Setup to Measure Out of Band Emission
! Emission into all Wavelengths: 211mJ (2.0%)
Xe Gas
Feed
He Feed
! Emission into 11nm - 20nm band: 110mJ (1.0%)
! Emission into 130nm - 1300nm band: 0.8mJ
1.6 mm2
Aperture
UV + VIS Emission is only 0.4 % of all radiation
Mass
Flow
Controller
1 µm Be Foil
CaF2
Open
2” TurboPump
6” TurboPump
Pump
208 cm
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1 cm2 IRD
un-coated
photodoide
Setup to Measure Out of Band Emission
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Pinhole Imaging Setup
CCD Detector
Variable angle
between 0 and 30°
Pixel size = 24 µm
Scale = 8 µm / pixel
Be Filter, Thickness = 2.0 µm
DPF
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Pinhole Diameter = 50 µm
Magnification = 3.0
EUV Source Images with Xenon
10 deg.
Angle = 0 deg.
20 deg.
0
0
0
50
50
50
50
100
100
100
100
150
150
150
150
200
200
200
200
250
250
250
250
300
60 100 150 200
FWHM = 0.26 mm
50
100 150 190
0.29 mm
55 100
150 195
0.29 mm
FWHM along the axis = 1.7 mm
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30 deg.
60 100
150 200
0.25 mm
Grazing Incidence Collector Design
!
!
!
!
!
!
!
Collector Output: Imaging (Elliptical Shells)
Source to Image Distance = 400 mm
Focal Length = 200 mm
Distance to Entrance = 50 mm
Number of Reflections = 1
Mirror Coating Material: Ruthenium
Grazing Angle (Outer Shell): 19.6° - 26.8°
(Inner Shell): 7.4° - 11.0°
! Collector Length = 150 mm
! Geometrical Collection = 28.6% of 2π (two shells)
! Overall Collection Efficiency = 18.6% of 2π (two shells)
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Ellipsoid Collector Tests (Visible Light)
Measured 9 mm from focal point
Measured at focal point
305
305
500
500
300
300
450
450
295
295
400
400
290
290
350
350
285
285
300
300
280
250
250
275
200
200
150
150
4
100
100
280
275
270
270
265
4
4
265
260
260
255
0
20000 30000 255
215 220
30000
2
0
0
215 220
FWHM
(mm)
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50
0
230
240
250
260 265
0
20000 35000
00
0
100
200
300
100
-2
200
0
2300
2
400
500
400
500
35000
-2
-2
20000
10000
2
50
20000
-4
-4
0
230 -4
-4 240 -2
X
0.074
-0.12
250
0
Y
0.081
260
2 265 4
0 -4
-4
-2
0
4
4
Debris Mitigation Foil Trap Concept
Foil Trap
Xenon
Supply
Grazing Incidence Collector
Helium Supply
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Pump
Foil Trap Concept
Light rays pass through foil trap
Debris sticks to walls of a foil trap
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First Foil Trap Exposure Experiment
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Example of foil Trap Geometry
PHILIPS research
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Initial Results of foil Trap Efficiency
- Ru samples supplied almost perfect
- Source as is: after 0.5 M shots W coating
(~> 5nm ) due to electrode erosion
- after 2 M shots, no W
deposition behind trap,
no reflection loss
- Ru coating on electrode may help as well.
- Higher rep rate needed to demonstrate
realistic lifetime (~1000M shots, i.e. 250 h
at 1 kHz)
PHILIPS research
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Differential Pumping Across Foil Trap
Inside: channel array
Gas flow controller
- diff pump over array of 80x 80
channels: 0.5 mm diam., 2 cm length
Turbo pump
- using effectively 500 l/s turbo pump
speed we achieve 0.013 mbar N2 behind
foil with 1.4 mbar N2 in front of foil
(pressure needed for DPF)
- prediction and measurement agree:
100x pressure reduction
- Therefore, ~0.002 mbar Xe and 0.01
mbar He behind array, near first collector
seems reachable.
Roughening pump
PHILIPS research
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Results of Differential Pumping Across Foil Trap
Operating
range
- results indicate that at
lower pressure in front of
array, even lower pressures
behind array can be realised.
PHILIPS research
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Preferred Foil Trap Configuration
Foil Trap
Xenon
Supply
Grazing Incidence Collector
Pump
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Helium Supply
13.5nm Transmission Through 400 mm of He
1.0
0.9
Operating
Range
0.8
Transmission
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0.0
0.00
0.25
0.50
0.75
1.00
1.25
Pressure (Torr)
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1.50
1.75
2.00
Cooling Concepts Under Evaluation
Cooling Concept
Direct water cooling
Direct helium cooling
Water heat pipe
Advantages
High heat flux removal
Low cost cooling system
Compact design
High heat flux removal
Safe and inert
Lithium compatible
Passive design
Minimizes contamination
Lithium evaporation cooling
Simple, compact anode design
Radiation-cooled
lithium heat pipe
Passive design
Minimizes contamination risk
Simplifies electrical isolation
Simple, compact anode design
Passive design
Minimizes contamination risk
Compact design
Direct liquid lithium cooling
Lithium heat pipe with
integral heat exchanger
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Disadvantages
Safety issue with lithium
Thermal shock issue
De-ionized water required
Helium loop required
Limited to <1kW heat load
Pressure containment issue
at high temperatures
Removal of excess lithium
Removal of heat still needed
Not compact [large condenser
surface required]
Lithium pumped loop required
Helium loop required
Heat Transfer Modeling
Temperature Distribution
Highest Temperature
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Direct Water Cooling
Tungsten, Molybdenum
Free Machining Copper
Cooling
Water
Cooling
Water
304L Stainless Steel
Welds
Cooling Water
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13.5 nm EUV Power with Cymer’s Collector
! Conversion Efficiency with Xenon = 0.25 %
" Electrical Energy Input per Pulse: 10J
" In-band Emission into 2π per Pulse: 25 mJ
! Collection Efficiency with Grazing Incidence Collector = 18 %
" Fraction of 2π Subtended by Collector: 28.5% (1.8 str)
" Average Grazing Incidence Reflectivity of Ru: 65%
! Maximum collectable, in-band (2% BW), 13.5nm emission power
with Xenon source gas in burst mode: 4.5 W
! Maximum collectable, in-band (2% BW), 13.5nm emission power
with Xenon source gas in continuous mode: 11 W
" Maximum Expected Thermal Extraction Capability = 25 kW
" Limit is based on exposed surface area and use of heat pipe technology.
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Conclusions
! Conversion efficiency with Xenon comparable to other direct plasma
sources has been demonstrated, CE = 0.25 %.
! Out-of-band UV/Vis emission is very low.
" Eliminate 50% throughput hit
" Avoid SPF heating issues
! Foil trap experiments show effectiveness:
" Debris mitigation
" Differential pumping
! Current output energy stability of ~ 10% still needs improvement.
! Due to present thermal limits, ultimate in-band (2% BW) collectable
13.5nm optical power with Xenon as a source gas is approximately 11 W.
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