contamination control in euv exposure tools · nikon corporation contamination control in euv...
Post on 17-May-2020
3 Views
Preview:
TRANSCRIPT
June 12, 2013
Katsuhiko Murakami Noriaki Kandaka, Takashi Yamaguchi, Atsushi Yamazaki,
Tsuneyuki Hagiwara, Tetsuya Oshino, Jiro Inoue and Kazuya Ota
Nikon Corporation
Contamination control in EUV
exposure tools
2013 EUVL Workshop Katsuhiko Murakami
Contamination control in EUV exposure tools
June 12, 2013 2 2013 EUVL Workshop Katsuhiko Murakami
EUV-induced contamination
• Carbon contamination
• Surface oxidation
Particles in vacuum
Contamination control in EUV exposure tools
June 12, 2013 3 2013 EUVL Workshop Katsuhiko Murakami
EUV-induced contamination
• Carbon contamination
• Surface oxidation
Particles in vacuum
EUV + O2 mitigation
On-body UV dry cleaning
Contamination study using a synchrotron facility
June 12, 2013 4 2013 EUVL Workshop Katsuhiko Murakami
Branch chamber
Exposure chamber
Folding mirror
Gate valve with Zr filter
Neutral density filter
Neutral density filter
Rotational photo diode
Sample stage
Load rock chamber
Transfer rod Gas inlet
Synchrotron radiation
0.8
0.85
0.9
0.95
1
0 200 400 600Cumulative dose [J/mm
2]
Re
lative
re
fle
cta
nce
0.88
0.9
0.92
0.94
0.96
0.98
1
0 2 4 6 8 10
Cumulative dose [J/mm2]
Re
lative
re
fle
cta
nce
8W/cm21W/cm2
0.1W/cm2
8W/cm2
1W/cm2
0.1W/cm2
0.01W/cm2
0.002W/cm2
0.8
0.85
0.9
0.95
1
0 200 400 600Cumulative dose [J/mm
2]
Re
lative
re
fle
cta
nce
0.88
0.9
0.92
0.94
0.96
0.98
1
0 2 4 6 8 10
Cumulative dose [J/mm2]
Re
lative
re
fle
cta
nce
8W/cm21W/cm2
0.1W/cm2
8W/cm2
1W/cm2
0.1W/cm2
0.01W/cm2
0.002W/cm2
Contamination growth with perfluorohexane (C6F14)
BL 18 at SAGA LS SR facility
EUV + O2 mitigation of carbon contamination
June 12, 2013 5 2013 EUVL Workshop Katsuhiko Murakami
1E-5
1E-4
1E-3
1E-2
1E-1
1 10 100 1000 10000
E , irradiance [mW/cm2]
V , c
on
tam
ina
ting/c
lean
ing r
ate
[n
m/s
]
C6F14 (5E-5Pa) O2 cleaning (2E-2Pa)
7 8 9 10 11 12 13 14 15 16
Number of pulses irradiated to IU [billion pulses]IU
tra
nsm
itta
nce
[a
rb. u
nit
]
Modeled
Actual
Oxygen flow optimized
History of IU transmittance of EUV1 Contamination growth rate
and O2 cleaning rate
O2 cleaning rate exceeds carbon contamination growth rate in appropriate condition.
Degradation of IU (Illumination Unit) transmittance of EUV1 was stopped after
optimization of O2 flow rate.
EUV + O2 mitigation is very effective to carbon contamination.
Position on mirror
Reflectivity
UV dry cleaning of carbon contamination
June 12, 2013 6 2013 EUVL Workshop Katsuhiko Murakami
Before cleaning After cleaning
● Before cleaning, ■ After cleaning UV dry cleaner using a low pressure mercury lamp
Carbon contamination on a illumination optics of EUV1 can be removed
with UV dry cleaning. Initial reflectivity was recovered.
UV dry cleaning in depressurized atmosphere
June 12, 2013 7 2013 EUVL Workshop Katsuhiko Murakami
1 atm1 atm1/100 atm1/100 atm
◆ measured
--- calculation
Cleaning rate of carbon contamination with UV dry cleaning increases
with reduced pressure.
UV dry cleaning was applied to an on-body cleaning method in EUV1.
低圧水銀ランプ
洗浄サンプル
Low pressure mercury lamp
Sample
真空チェンバー
低圧水銀ランプ
Vacuum chamber
Low pressure mercury lamp
On-body UV dry cleaning for IU of EUV1
June 12, 2013 8 2013 EUVL Workshop Katsuhiko Murakami
FE1
FE2
Con1
Con2
Low pressure mercury lamps placed near each mirror
enabled on-body cleaning of illumination optics.
FM
Contamination control in EUV exposure tools
June 12, 2013 9 2013 EUVL Workshop Katsuhiko Murakami
EUV-induced contamination
• Carbon contamination
• Surface oxidation
Particles in vacuum
EUV + O2 mitigation
On-body UV dry cleaning
Metal-oxide capping layer
0.8
0.85
0.9
0.95
1
0.0E+0 5.0E+4 1.0E+5 1.5E+5 2.0E+5
Dose [J/cm2]
Si
MoOx
NbOx
Ru
Metal oxide capping layer
June 12, 2013 10 2013 EUVL Workshop Katsuhiko Murakami
Si
Si
Si
Mo
Mo
Si
Si
Si
Mo
Mo
Metal oxide capping layer
Reflectivity change of Mo/Si multilayers with several different capping layer materials
during EUV exposure in water vapor was measured.
H2O: 1x10-3 Pa, 8 W/cm2
Rela
tive c
hange o
f re
flectivity
Metal oxide capping layers have much higher oxidation durability
compared with conventional Ru capping layer.
Contamination control in EUV exposure tools
June 12, 2013 11 2013 EUVL Workshop Katsuhiko Murakami
EUV-induced contamination
• Carbon contamination
• Surface oxidation
Particles in vacuum
EUV + O2 mitigation
On-body UV dry cleaning
Metal-oxide capping layer
Particle capture using silica aerogel
Particles in vacuum: Materials
June 12, 2013 12 2013 EUVL Workshop Katsuhiko Murakami
• Potential particle generating events
– Physical contact
• Collisions: wafer/reticle transfer, pod open/close,
valve o/c, grounding pin contact, …
• Rubbing: bearings, ultrasonic motors, …
– Physical reaction
• Sputtering: corona ionizers, EUV sources, …
• Evaporation and condensation: pumping down in load lock
– Electrical discharge/spark
• EUV sources
• Discharge between reticle and pod during a transitional region in load lock
• Micro-discharge between wafer/reticle backsides and e-chucks.
• Potential materials
– Metal/metalloid: Na, Al, Si, K, Ca, Ti, Cr, Fe, Ni, Mo, Ru, Sn, Ta, …
– Inorganic: SiO2, …
– Organic: CxHyOz
+V -V
HEAVY! > 7 g/cm3
cf. PSL~1 g/cm3
Particle in vacuum: Velocities
June 12, 2013 13
• Interaction with surfaces “bounce or stick” depends on the
relationship between the particle impact velocity Vi and the
critical velocity Vc.
– Vi < Vc: stick
– Vi > Vc: bounce
– Vi >> Vc: split and stick/bounce
S. Wall, et al., Aerosol Science and Technology, Volume 12, Issue 4, 1990, Pages 926 – 946
Critical velocity vs. particle diameter
96 m/s 76 m/s
457 m/s
• Vc is determined by the surface
material, the particle material,
the particle size, etc.
• Particles that have lower
velocities than the critical
velocity cannot continue to fly.
100 nm
FAST! Typical Vc :
100 m/s for 100-nm particles
2,000 m/s for 10-nm particles
2013 EUVL Workshop Katsuhiko Murakami
Particles in vacuum: Flying range
June 12, 2013 14 2013 EUVL Workshop Katsuhiko Murakami
• Forces acting on particles in vacuum
– Gravity: r 3, dominant force but not decelerating force
– Drag force: r 2, weak, depends on the gas pressure
– Coulomb force: weak, depends on E and amount of electric charge
– Thermophoretic force: very weak, depends on the thermal gradient
Flying range vs. Initial velocity
Mo particles in 0.01-Pa O2 gas 1
10
100
1,000
10,000
100,000
1,000,000
10 100 1,000 10,000
Fly
ing
ra
ng
e (
m)
Initial velocity (m/s)
10 nm 100 nm 1,000 nmParticle diameter
below Vc
LONG!
> 100 m
Particle reduction system
June 12, 2013 15 2013 EUVL Workshop Katsuhiko Murakami
To simplify the models, gravity is neglected and the same coefficient of restitution (COR) is used for both the vertical
component and the parallel component to the wall.
Particle source at the top.
Shield between the particle source and the
mask.
Performance of shield is insufficient.
Particle source at the top.
Particle catcher on the shield.
Particle catcher can drastically reduce
the number of flying particles.
Mask
Shield
Mask
Particle shield Particle catcher
Particle catcher
Silica aerogel as particle catcher
June 12, 2013 16 2013 EUVL Workshop Katsuhiko Murakami
STARDUST : NASA’s comet sample return mission, 1999 - 2011
Comet particles
Velocity: ~ 6.5 km/s
Diameter: 40 - 300 µm
Dust Collector with aerogel February 7, 1999
Stardust Launch
Aerogel In Hand
Particle Tracks in Aerogel
(experiment)
Comet Ejecta in Aerogel Photos from jpl.nasa.gov
Vacuum tool particles
Velocity: 10 m/s - 1 km/s
Diameter: 1 µm - 10 nm
Kinetic
energy
10 –13 - –15
1
Thinner sheet is enough
for EUV tools.
Structure of silica aerogels
June 12, 2013 17 2013 EUVL Workshop Katsuhiko Murakami
SiO2
Pore size micro pores: < 2 nm
mesopores: 2-50 nm
macro pores: > 50 nm
Silica particle diameter
2-5 nm
Apparent density: 0.003-0.35 g/cm3
Pore network
Density of air: 0.0012 g/cm3 at 20 °C
Experimental setup of particle catcher
June 12, 2013 18 2013 EUVL Workshop Katsuhiko Murakami
MPE Tool
Particle generator installed
in ESC chamber
High voltage
feedthroughs
Induction coil
Lead wire: +V Particles were generated by discharging
(Air pressure ~5E-3 Pa) Lead wire: V
Photos of aerogel tested:
bare (left) and covered by a foil (right)
Size: 100 mm (W), 100 mm (D), 15 mm (H)
Density: 0.012 g/cm3
Aerogel in ESC chamber
Metal Plate having a through hole
A quarts substrate for particle adhesion
evaluation (not shown in the photo)
Cover plate
Aerogel Aerogel holding plate
10-20% of particles can
go out through the gap
Experimental conditions of particle catcher
June 12, 2013 19 2013 EUVL Workshop Katsuhiko Murakami
#2: Bare aerogel sheet
• The foil was removed.
• Discharging was continuously and the total time was
about 8 seconds.
#1: Aerogel sheet covered with a foil
• An aerogel sheet covered by a foil on the holding plate
was put between the quarts substrate and the particle
generator.
• Discharging was continuously and the total time was
about 8 seconds. Particles are not captured.
Particles are captured.
Experimental results #1: Covered with foil
June 12, 2013 20 2013 EUVL Workshop Katsuhiko Murakami
157
20,431
83,262
53,683
79,865
22,982
3,839
13,137
14,289
Total = 291,645
Pixel Histogram
41 ...
… 40
… 20
… 10
… 7
… 5
… 3
… 2
… 1
117
13,266
59,354
49,915
90,868
29,952
4,452
16,635
19,063
Total = 283,622
Pixel Histogram
41 ...
… 40
… 20
… 10
… 7
… 5
… 3
… 2
… 1
Almost
the same
density
Particle density: 1,331 particles/cm2 Particle density: 1,368 particles/cm2
Up Down
26- >=300 nm
22-25 200 nm
17-21 100 nm
14-16 80 nm
11-13 70 nm
7-10 60 nm
1-6 pix =< 50 nm
Experimental results #2: Bare aerogel
June 12, 2013 21 2013 EUVL Workshop Katsuhiko Murakami
74
519
3,730
4,288
8,317
2,856
412
1,663
1,812
Total = 23,671
Pixel Histogram
41 ...
… 40
… 20
… 10
… 7
… 5
… 3
… 2
… 1
8
184
1,456
2,285
5,546
2,119
274
1,201
1,414
Total = 14,487
Pixel Histogram
41 ...
… 40
… 20
… 10
… 7
… 5
… 3
… 2
… 1
Particle density: 68 particles/cm2 Particle density: 111 particles/cm2
#1 1/20 #1 1/12
Up Down
The aerogel sheet caught almost all particles that impacted it !!
26- >=300 nm
22-25 200 nm
17-21 100 nm
14-16 80 nm
11-13 70 nm
7-10 60 nm
1-6 pix =< 50 nm
Summary
June 12, 2013 22 2013 EUVL Workshop Katsuhiko Murakami
Oxygen introduction during EUV exposure effectively mitigates
carbon contamination growth on optical elements in EUV exposure
tools.
Carbon contamination on optical elements can be removed by UV
dry cleaning. It can be applied to an on-body cleaning method in
EUV exposure tools.
Surface oxidation of multilayer mirrors during EUV exposure can be
prevented by using metal-oxide capping layer.
Particles in a vacuum chamber fly very long distance. Silica aerogel
is suitable material to capture such flying particles in EUV exposure
tools.
Acknowledgements
June 12, 2013 23 2013 EUVL Workshop Katsuhiko Murakami
• EUVA
• NEDO
• METI
• Selete & EIDEC
• SAGA Light Source
• Chiba University
• Panasonic Corp.
top related