Novel Ozone-based Cleaning Technique for EUV Optics ... - Sematech

Novel Ozone-based Cleaning Technique for
EUV Masks and Optics Carbon Contamination
Toshihisa Anazawa, Yasushi Nishiyama † , Noriaki Takagi,
Osamu Suga, Iwao Nishiyama
MIRAI-Semiconductor Leading Edge Technologies, Inc.
Toshinori Miura
MEIDENSHA CORPORATION
† present affiliation: TOPPAN PRINTING CO.,LTD.

Contamination Contamination on on EUV EUV optics
optics
degrades degrades reflectivity
reflectivity
and and must must be be be cleaned.
cleaned.
Method
Oxygen Plasma
Hydrogen Plasma
EUV+Gas (O 2 )
UVOzone
A carbon contamination sample
on the SFET illumination mirror.
(after ~9 months of use)
H-Radical
(W-fil. cracking)
Shielded Plasma
Rate

Experimental
Experimental
Cleanability Test:
Sample: C/Si-Wafer
C-deposition: SEM with Phenanthrene (C 10 H 10 ) gas;
Area=1 m; Electron dose=6 ~ 600×10 18 e - •cm -2
Cleaning:
Ozone-based dry process with 100% pure ozone
generated by MEIDENSHA's pure ozone generator
Evaluation: AFM (Before and after processing)
Damage Test:
Reflectivity (Reflectometer)
Ru-alloy cap. ML Si cap. ML
Oxidation (XPS)
Ru-alloy cap. ML Si cap. ML
TaBN LR-TaBN TaSi LRTaSi
EUVL EUVL Symposium Symposium 2009 2009
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Merits of gas addition
No light irradiation
No kinetic damage
No thermal damage
Ethylene
Ethylene
Gas Gas Addition Addition Method
Method
MEIDENSHA's
MEIDENSHA's
MEIDENSHA's
pure pure pure ozone ozone generator
generator
•O 3 generation
Pure Pure O O3
~100 100 %
%
•O 3 condensation
•evaporation
~100 100 100 100 100 Pa
Pa
Pa
Pa
C C H
Extraordinarily Extraordinarily reactive reactive reactive agents agents are are are generated generated by by O O3
×C2H4 reaction.
+O +O +O3
But, actual agents and processes are still unknown.
primary
ozonide
Exhaust
Exhaust
via via combustion
combustion
abatement abatement system system
system
EUVL EUVL Symposium Symposium 2009 2009
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R
O O O
C C H
R
C O O O C H - +
R
・O O ?
?
unsatulated
hydrocarbon
ozone
・O H H ?
?
・H H ?
?
misc. radicals
"Novel "Novel Plasmaless Plasmaless Plasmaless Photoresist Photoresist Removal Removal Method Method in in gas gas Phase Phase at at Roo Room Roo m Temperature", Temperature", T. T. Miura Miura et et al., al., 921, 921, 215th ECS Meeting (2009).
(2009).
?
some
candidates
of reactant

Room Room Temperature Temperature (1 (1 min)
min)
Cleanability
Cleanability
Initial Initial Initial
Processed
Processed
100 100 °C C (1 (1 min)
min)
Thickness (nm)
Thickness (nm)
1000
800
600
400
200
1000
800
600
400
200
EUVL EUVL Symposium Symposium 2009 2009
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0
0
Before
After
Carbon Carbon have removed by 70~80 70~80 70~80 70~80 nm/min nm/min. nm/min
nm/min. nm/min
Initial Initial Initial
Processed
Processed
Removed
Before
After
Removed
Carbon Carbon have removed by 150~250 150~250 150~250 150~250 nm/min nm/min. nm/min
nm/min. nm/min
250
200
150
100
50
0
250
200
150
100
50
0
Removed (nm)
Removed (nm)

Before
After
10
*
0
-10
Position (mm)
65
64
63
62
61
60
Reflectivity (%)
Reflectivity
Reflectivity
Reflectivity Reflectivity Reflectivity Change Change Change after after after 1 1 min min min of of of Processing
Processing
Processing
Si Si capped capped ML
ML
Before
After
10
-10
Ru Ru-alloy Ru alloy capped capped ML
0
65
64
63
62
61
60
Position (mm)
Reflectivity (%)
Reflectivity (%)
Reflectivity (%)
70
60
50
40
30
20
10
0
70
60
50
40
30
20
10
0
* Initial Initial data was not not measured at at point 0 0 for Ru Ru-alloy Ru
alloy alloy
thus thus thus the the the average average value value of of 10 10 and and -10 10 is plotted.
Correspond to 70~80 nm of carbon film removal.
13.1 13.6 14.1
Wavelength (nm)
13.0 13.5 14.0
Wavelength (nm)
Average Average
Average
Processed
Reference
No degradation was observed.
No degradation was observed.
Processed
Reference
before
63.6 %
63.6 %
before
63.7 %
63.4 %
diff.*
-1.8 %
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-
after
64.0 %
63.7 %
after
61.9 %
~2 % of reflectivity down.
~2 % of reflectivity down.
diff.*
+0.4 %
+0.1 %
* Measurement errors and secular changes are included.
Average
Average
* Measurement errors and secular changes are included.
included.
-

Oxidation Oxidation
Oxidation
Oxidation Oxidation State State Change Change after after 1 1 and and 1+2=3 1+2=3 min min Processing
Processing
Atomic Atomic %
%
Correspond to 70~80 nm (1min) and 210~240 nm (1+2 = 3min) of carbon film removal, respectively.
Si capped ML (Si oxidation state)
60
40
20
0
Si Si Si
Si
Si
Si 4+
Si +
Si Si 2+ Si Si 3+
Oxidation Oxidation Oxidation Oxidation State State State State
Si
Si
SiO SiO SiO2
1
0
1+2 1+2 1+2 1+2
Estimated Estimated SiO
SiO2 Thickness* Thickness* (nm)
(nm)
3
2
1
0
Time Time Time Time (min) (min) (min) (min)
A A small growth
(0.4 nm ~ 2 atomic layers/3 min)
of oxide layer is observed
but it seems to tend to be saturated.
The The growth is expected to stop when the
thickness reaches the maximum thickness
of natural oxide. (usual 2~3 nm thick)
*Calculated from escape depth of the photoelectron of Si
assuming uniform SiO 2 surface layer on the bulk Si.
Si cap ML is durable against our new process.
Si cap ML is durable against our new process.
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Oxidation Oxidation
Oxidation
Oxidation Oxidation State State Change Change after after 1 1 and and 1+2=3 1+2=3 min min Processing
Processing
Correspond to 70~80 nm (1min) and 210~240 nm (1+2 = 3min) of carbon film removal, respectively.
Ru-alloy capped ML (Ru oxidation state)
Atomic Atomic %
%
60
40
20
0
Ru
Ru
4+
6+
Ru4+ Ru 6+
(min) (min) (min) (min)
1+2 1+2 1+2 1+2
1
0
Oxidation State of Ru.
Si/Ru Si/Ru Ratio Ratio
0.5
0.4
0.3
0.2
0.1
0
90 90° 90
45 45°30 45
30 30° 30
(min) (min) (min) (min)
1+2 1+2 1+2 1+2
1
0
Si/Ru Ratio by Angle-Resolved XPS.
Weighted* Weighted* Si Si Oxide
Oxide
(arb. (arb. units)
units)
90 90° 90
45 45°30 45
30 30° 30
(min) (min) (min) (min)
1+2 1+2 1+2 1+2
1
0
Weighted* Ratio of Si Oxide.
*Weight: Weight:
SiO 2 2
Si (3) 3/2
Si (2) 1
Si (1) 1/2
Ru is oxidized and oxidation proceeds with process time. (left fig.) fig.)
The ratio of Si/Ru increases with process time. (middle fig.)
Si oxide near surface increases with process time. (right fig.)
loss of Ru and/or surface segregation of Si. (Sublimation Pressure Pressure
of Ru 8+ is high.)
Ru-alloy cap is not durable against our new process.
Some process tuning or oxidation resistant capping
layer is disired (if Si cap is not suitable).
EUVL EUVL Symposium Symposium 2009 2009
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Oxidation Oxidation
Oxidation
Oxidation Oxidation Oxidation State State Change Change after after after 1 1 min min min Processing
Processing
Low Low Low-Reflection Low Reflection Layers
Normalized
Normalized
Intensity Intensity
LR LR-TaBN LR
TaBN
Ta Ta 4f
4f
0 0 min
min
1 1 min
min
34
32
30
28
26
24
22
20
18
Binding Binding Energy Energy (eV) (eV)
(eV)
Absorbers Absorbers
Ta Ta of of TaBN TaBN absorber
absorber
Atomic Atomic %
%
80
60
40
20
0
5/2
5/2
7/2
7/2
Ta, Ta Ta-B Ta
TaOx, TaOx, TaOx, TaOx, Ta Ta-N Ta
Ta 2O5 1 1 1 1 min min min min
0 0 0 0 min min min min
Normalized
Normalized
Intensity
Intensity
Atomic Atomic %
%
80
60
40
20
0
LRTaSi
LRTaSi
Ta Ta 4f
4f
5/2
5/2
0 0 min
min
1 1 min min
min
34
32
30
28
26
24
22
20
18
Binding Binding Energy Energy (eV)
(eV)
Ta Ta of of TaSi TaSi absorber
absorber
Ta, Ta Ta-Si Ta
Si Si Si
TaOx TaOx TaOx TaOx
Ta 2O5 7/2 7/2
7/2
Ta Ta Ta metal metal
metal
(if (if (if exists)
exists)
5+ Ta 5+
Ta
Ta
1 1 1 1 min min min min
0 0 0 0 min min min min
Correspond to 70~80 nm of carbon film removal.
Ta Ta metal*
metal*
(if (if exists)
exists)
Ta in LR-TaBN LR TaBN and LRTaSi
are almost fully oxidized
from the beginning
and was not affected
by the process.
Spectra Spectra for for LRTaSi LRTaSi (right (right panel) panel) seems seems broadened
broadened
because because of of the the charge charge-up charge up effect.
*Baseline Baseline rises in LRTaSi spectra but it is not the signal
signal
of of Ta Ta metal metal because because no no 4f 4f 5/2 5/2 - 7/2 structure is seen.
Ta in TaBN also showed no change.
Ta in TaSi tend to be oxidized a little.
LR-TaBN is durable against our new process.
LRTaSi needs more examinations.
EUVL EUVL Symposium Symposium 2009 2009
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Summary Summary
Summary
Cleanability
Using novel ozone based cleaning technique, emulated
carbon contamination film was removed efficiently.
The removal rate exceeds 70 nm/min at room temperature
and accelerated to 150~200 nm/min at 100 °C.
Damage
Reflectivity did not degrade for Si capped ML mirror
but ~2 % down for Ru-alloy cap. with 1 min of processing.
On mask materials, oxide-like anti-reflective layer and
TaBN seemed stable to our new process.
In conclusion, our new process could be applicable to
Si-cap. mirror and Si-cap. mask with LR-TaBN absorber;
but some tuning will be needed for Ru-alloy cap. optics.
This Work was Supported by NEDO*
(*New Energy and Industrial Technology Development Organization)
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