Mitigation of Carbon Contamination
Takahiro Nakayama1, Hiroyoshi Kubo1, Akira Miyake1, Hiromitsu Takase1, Ichiro Tanaka1, Shigeru Terashima1,
Takashi Sudo1, Shintaro Kawata2, Takashi Aoki2, Shuichi Matsunari2, Hiroo Kinoshita3, Takeo Watanabe3, Masahito Niibe3
CANON INC.1
NIKON CORPORATION2
University of Hyogo3
Cleaning
Strategy
O
capping
O
O
z Carbon deposition
Oxidation
Si
z
Estimating optics lifetime by the scaling law
z
Developing mitigating method and cleaning method
Mo
Experimental methodology
C coated mirror
TMP
TMP
Photo diode
orifice
(φ4 mm)
Q-MS
Long undulator
TMP
Sample
Pinhole
(φ100 mm and φ2 mm)
2.0
250
1.5
200
150
1.0
100
0.5
50
0.0
0
HxCy gas
-1.0
oxidizing gas
-0.5
0.0
0.5
average EUV
intensity(mW/mm2)
(incident angle=80 deg.)
Carbon thickness and
EUV intensity in NewSUBARU
carbon thickness(nm)
Experimental apparatus in NewSUBARU
1.0
distance from irradiation center(mm)
Experimental conditions
decane:1x10-6 Pa
Irradiation time: 3hr.
Scaling law
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0.0
Decane
partial pressure
5E-6 Pa
1E-6 Pa
3E-7 Pa
0
50
100
150
200
D
Dependence
d
on decane
d
partial
ti l pressure
carbon deposition rate
(nm/hr.)
carbon deposition rate
(nm/hr.)
D
Dependence
d
on EUV intensity
i t
it
4.0
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0.0
EUV intensity
180 mW/mm2
70 mW/mm2
1E-7
average EUV intensity(mW/mm2)
1E-6
1E-5
3.0
2.0
1.5
1.0
0.5
0.0
-0.5
0
50
100
150
average EUV intensity(mW/mm2)
0.4
New SUBARU
Supre-ALIS
0.3
0.2
Estimation of the carbon deposition
on a HVM Tool
Exp. conditions
HVM Tool conditions
0.1
Injected decane
2~3 x 10-7 Pa
0.0
0
50
100
average EUV intensity (mW/mm2)
Beamline
EUV peak intensity (mW/mm2)
Super-ALIS
NewSUBARU
12~24
~200
carbon deposition rate (nm/hr.)
carbon deposition rate
(nm/hr.)
Comparison between
NewSUBARU and Super
Super--ALIS
1E-2
Pulse width
10 nsec.
26 psec.
78 psec.
1E-3
1E 4
1E-4
1E+4 1E+6 1E+8
source frequency (Hz)
Calculation conditions
Pulse width (psec.)
78
26
decane partial pressure : 1x10-7 Pa
Frequency (MHz)
125
500
average EUV intensity : 1 mW/mm2
* T. Nakayama, Proc. of SPIE Vol. 7271, 72713P, 2009
z Carbon deposition rate is not proportional to HC pressure, nor to EUV
intensity. Carbon deposition rate depends on EUV source parameters.
z The carbon deposition rate was estimated by an experimental formula*.
it is ~1E-3 nm/hr.. A HVM Tool has to have a carbon removal system.
50
100
150
200
average EUV intensity(mW/mm2)
250
EUV source: NewSUBARU BL9
Sample:C(~3nm)/ [Si(4.2nm)/ Mo(2.8nm) ]50
Injected gas pressure : 0.01 Pa
Sample preparation
Carbon was deposited by 1hr. EUV irradiation
injecting decane (1E-5 Pa)
1.0
56
55
54
53
52
51
50
49
48
0.4
0.3
0.2
0.1
0.0
0
50
100
150
200
250
average EUV intensity(mW/mm2)
1E-3 Pa
0.6
1E-2 Pa
0.4
Average EUV intensity
20mW/mm2
0.2
0.0
200
0E+0
1E-4
2E-4
3E-4
4E-4
ozone partial pressure(Pa)
Ozone partial pressure is estimated by the following equation**
C : ozone concentration
I 48
C × I 48
=
I 32 C × I 32(O3) + (1 − C) × I 32(O2) I : Q-MS intensity
Evaluation of damage by ozone
0.5
Total pressure
0.8
decane(~E-6 Pa)+O2(1E-2 Pa)
**Y. Sato et. al., J. Vac. Soc. Jpn., Vol. 48, No. 6, 2005
this sample was analyzed
carbon thickness
SiOx/(SiOx+Si)
* SiOx/(SiOx+Si) at unirradiated region is ~40%.
Experimental conditions
EUV source: NewSUBARU BL9
Sample: [Si(4.2nm)/ Mo(2.8nm) ]50
Irradiation time: 3 hr.
Injected gas: Decane(~E
Decane(~E-6
6 Pa) + [O2+O3](1E
](1E-2
2 Pa)
z O2+O3 is the most effective mitigation gas among our candidates( H2O, O2 or
O2+O3) in the region of a HVM EUV intensity. Carbon deposition rate seems to
be mitigated with increasing ozone partial pressure.
z O2+O3 makes MLM oxidized. Anti-oxidation MLM is needed to use O2+O3 as a
mitigation gas.
„ Scaling
g law
Injected
j
gas:
g
Decane(C
( 10H22)
Background pressure: 2E-7 Pa
0
Experimental conditions
decane(~E-6 Pa)+ H2O(1E-2 Pa)
decane(~E-6 Pa)+ [O2+O3](1E-2 Pa)
1E-4
Experimental conditions
O2
O2+O3(2%)
Dependence on ozone partial pressure
HVM Tool
EUV intensity
2.5
decane partial pressure(Pa)
EUV source: NewSUBARU BL9
Sample: [Si(4.2nm)/ Mo(2.8nm) ]50
Injected gas
H2O
HVM Tool
EUV intensity
Mitigation
Mitigation effect
SiOx/(SiOx+Si) (%)
z As an EUV light source we have used two different beamlines, NewSUBARU in the
university of Hyogo and Super-ALIS in the NTT atsugi research and development
center.
z The EUV lights has a gaussian-like distribution. The beam diameter is about 2 mm.
We used X-ray photoelectron spectroscopy (XPS) and obtained carbon deposition
quantity from photoelectron intensity of C(1s).
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0.0
-0.5
z Feasibility study of “EUV + oxidizing gas” cleaning has been done. O2+O3 is the most
effective cleaning gas among our candidates( H2O, O2 or O2+O3) in the region of a
HVM EUV intensity.
z The Carbon removal rate of O2+O3 cleaning would not be enough for a HVM Tool.
carbon deposition rate(nm/hr.)
Developing anti-oxidation MLM
z
Carbon
deposition
Carbon removal rate depends on average EUV
intensity. Therefore, deposited carbon can not be
removed uniformly. Carbon removal rate decreases
with decreasing average EUV intensity. It takes so
long cleaning time at a low EUV intensity.
It indicates that long cleaning time may oxidize
MLMs at a high EUV intensity.
z Oxidation
carbon deposition rate(nm/hr.)
EUV irradiation
Organic gases
Dependence of carbon removal rate
on EUV intensity
i t
it
EUV + oxidizing gas
UV + oxidizing gas
Atomic hydrogen
Carbon thickness(nm)
Background
Candidates for cleaning methods
Carbon removal rate(nm/hr.)
Abstract
Carbon deposition on multilayer mirrors (MLMs) of EUVL exposure tool optics under EUV irradiation degrades throughput
and imaging quality of the exposure tool.
tool It is very important to mitigate carbon deposition on MLMs to reduce the
cleaning frequency of EUV optics. We have been developing cleaning and mitigation method of carbon contamination. In
this paper, we focused on mitigation method for carbon deposition using an oxidizing gas environment. We performed
experiments of carbon deposition on Si-capped multilayer mirror under EUV irradiation inducing an oxidizing gas and a
hydrocarbon gas. An undulator beamline (BL9) of synchrotron radiation facility NewSUBARU in the University of Hyogo was
used as EUV source. Decane (C10H22) was used as the hydrocarbon gas. Water, oxygen or ozone-containing oxygen was
used as the oxidizing gas. As the result of the experiments, we found that the mitigation effect depends on gas
composition, gas pressure, and EUV intensity and ozone-containing oxygen is the most effective as the mitigation gas..
Summary
z Carbon deposition rate is not proportional to hydrocarbon pressure, nor to EUV
intensity. Carbon deposition rate depends on EUV source parameters.
z The reaction model needs to be created.
Parameters: gas species, capping layer, standing wave effect, etc
„ Cleaning method
z O2+O3 is the most effective cleaning gas among our candidates. However, it would
not be enough to remove carbon.
z Developing other method for a HVM Tool is needed.
„ Mitigating method
z O2+O3 is the most effective mitigation gas among our candidates in the region of
HVM Tool EUV intensity. Anti-oxidation MLM is needed to use O2+O3 as a mitigation
gas.
Acknowledgement
A part of this work was performed under the management of EUVA
as a research and development program of NEDO/METI, Japan.
The authors express their gratitude to NTT for the collaboration work with Super-ALIS.