Research Activities

Several-MeV gamma-ray generation at NewSUBARU
by laser Compton backscattering
S.Amano1, K.Horikawa1, S.Miyamoto1, T.Hayakawa2, T.Shizuma2, T.Mochizuki1
LASTI / UH1, a)JAEA2

Abstract

A new laser Compton gamma ray source in the energy range of several MeV was developed usinga CO2 laser at the NewSUBARU electron storage ring. When the electron energies were 974, 1220
and 1460 MeV, the maximum gamma ray energies were measured to be 1.72, 2.72, and 3.91 MeV.
The luminosity of the gamma rays was 7300 photon/mA/W/s and a flux of 5.8x106 photon/s wasachieved. A gamma beam divergence of 0.5 mrad and its pattern were also measured. These
performances agreed with calculations. This generation of gamma rays is in a no-loss mode for the
storage electrons, and the maximum flux was limited only by the power of the laser. A flux of up
to 1011 photon/s will be achieved using a 30 kW class CO2 laser. Several MeV gamma ray sourcesat NewSUBARU are capable of generating such high power.

Introduction
A Laser Compton gamma ray beam is avery unique light source having the positive
characteristics of tunable energy, quasimonochromaticity, tunable polarization andbeam directivity. It is generated by backward
Compton scattering with relativistic electronsand photons. The gamma rays have been
generated at several high-energy-electronaccelerating facilities around the world.
Gamma photon energies ranged from several
MeV to several GeV, depending on theelectron energy at each facility. G a m m arays in the energy range of a few tens MeV
are useful in the study of nuclear physics.
Although the peak energy of giant resonancemildly depends on the atomic mass of thetargets’ nuclei, it is around 15-25 MeV. The
NewSUBARU electron storage ring is suitablefor producing this energy gamma ray because
its electron energy condition allows for the useof a Nd-doped laser having a wavelength of
1.064 µm and such a laser has been developed
for stable and high-power operation. With
NewSUBARU operating at an electron energyof 1-1.5 GeV, laser Compton gamma rays of
17-34 MeV have been successfully generatedusing a commercial Nd:YVO4 laser withwavelengths of 1.064 µm and 0.532 µm. The
gamma ray is used in various studies: nuclear
physics, nuclear astrophysics, nuclear
transmutation and CT-imaging for industrial
applications.
Several applications, however, demand
gamma ray energies of several MeV. For
example, gamma rays of 1-4MeV are useful instudies of nuclear structures using thenuclear resonance fluorescence (NRF)
measurement technique. Using the polarized

gamma ray beam, we can determine theparity of excited states of nuclei. In addition,these gamma rays are used in studying anondestructive assay of materials hidden byheavy shields. For these applications, we have
expanded the energy range of the gamma ray
using a CO2 laser with a wavelength of 10.52µm. The CO2 laser is also capable of operating
in a high-power region. A new transportsystem transmitting the CO2 laser was added
and a focusing optic in it was designed to havea collision point different from that of the Nddoped laser. The gamma ray produced by theCO2 laser demonstrated an energy range of
1-4 MeV and flux of 5x106 photon/s in testing;this was consistent with the designed values.
The gamma ray flux can be increased easily
using a higher powered CO2 laser. It is easy togenerate a high flux gamma ray in the rangeof several to a few tens MeV because a highpowered Nd-doped laser and CO2 laser can beused with NewSUBARU operating at anelectron energy around 1 GeV.
Experiments
The NewSUBARU ring has two longstraight sections of 14 m and its whole shaperesembles a racetrack with a circumference of
119 m. Laser Compton scattering experiments
were conducted for one of the straight sections
combined with beam line 1 (BL 1). (Fig.1).
A laser was set in the experimental hall andits beam was introduced by mirrors inside ashield tunnel into a vacuum tube of the ring
through a focusing lens. The laser beam wasbent by a mirror inside the tube and collided
head-on into an electron beam. The gamma
ray was scattered only in the direction of theelectron beam and was extracted from the

ARTICLE IN PRESS

Laser beam radius (mm)Electron beam size (mm)shield tunnel into a shielding hutch. The
because the gamma beam divergence (1/γ)
extracted gamma ray beams were measured
decreased.
S. Amano et al. / Nuclear Instruments and Methods in Physics Research A ] (]]]]) ]]]–]]]
3by NaI and a Ge detector in the hutch.
If we use a 30 kW power CO2 laser at
The CO2 laser beam
NewSUBARU with a current of 500 mA, a
1.0 passing through thea was scattered by
new beam transport systemhigh flux gamma ray of ~1011 photons/s is
0.8
σx
=
0.3mm
σy = 0.18mm
relativistic electrons in NewSUBARU andachievedin several-MeV energy ranges. Even
0.6
σx For thisgamma rays were generated.
if such high flux gamma rays are generated,
σx = σy = 0.3mm
experiment, the incident
laser power andthe operation of the NewSUBARU electron
0.4
σyelectron beam current were set to 1 W and 1-2
storage ring is not affected. Because the
0.2
mA, respectively. Energy of the gamma ray A energy acceptance of B the 1 GeV stored0
was measured by a Ge detector(64 mm
φ x 60electronbeam5 is 9 MeV, which
is higher than
-10
-5
0
10
s
(m)
mm) with a high energy-resolution and the
gamma
ray energies in the several-MeV
10 a NaI scintillation
flux was measured byregions, the storage electrons are not lost inbcounter (5 inch φ x 5 inch)
the scattering process
and do not decrease the
8 with relatively highCO2absorption. Signals from6 these detectors were
beam lifetime. Thus, in principle, several-MeV
Ndprocessed by a multi-channel analyzer
andgamma ray sources at NewSUBARU,
4energy channels were calibrated absolutely
ω0 = 0.5mmcombined with the CO2 laser, do not have flux
2
using radioisotopes of Co-60,
K-40, Y-88, andl i m i t a t i o n s . B eω0c=a1.2mm
use CO2 lasers are0
Tl-208.
considered the most successful lasers at high
-10
-5
0
5
10
power generation, the gamma ray source iss (m)Results and Discussions
expected to be the highest-power light source
Fig. 2. (a) Electron beam size and (b) laser beam radius of the Nd-doped and CO lasers in the interaction zone. The zero value on the horizontal axis refers to the center ofTheenergyspectrameasuredbytheGein this energy region of the laser Compton
the long straight section.
detector at electron energies Ee of 974, 1220,
gamma ray.
and 1460 MeV are shown in Fig.3. There wastimes the diffraction
the Nd-doped
laser.
400
a being
lead tencollimatorwith a 3formm
φ hole intheTheelectron sizes sx and sy were 0.3 mm at this position. Considering
Ee=1220MeV
front
of
the
detector,
8.6
m
from
the
collision
effective hard apertures along the laser beam transport line, thepoint.
It radius
shouldbe noted
spectra tolaser spot
was determined
as 1.2 thesemm by calculations
Ee=1460MeV
Ee=974MeV
maximize thethe
luminosityof Eq. (7).
represent
convolutionof the detector
300
In this experiment, a commercial CO2 laser, Lasy-20 (Access
responsefunction with the gamma ray energy
Laser Company) [17] was used. The laser has a maximum cw
distribution.
full-energy
peaks
are ofpower of 20 W, As
beam thediameterof 2.4 mm, anddivergence
was operated
5.5 mradinwitha beamqualityof M2o1.2. The
visibleFig.1,
wedeterminedthelasermaximumin multiple longitudinal modes and measurements for four modes
energies
atofelectron
Ee of 974, 1220
200
mm were taken.
in the range
10.52–10.58energies
and The1460
MeV
bea ZnSe
1.72,
2.72,
focusing
lenstowasconvexlensandwith 3.91
a focusMeV,
length of
3.24 m. The lens
was used
as an image
optic with arespectively.
These
energies
are inrelay
agreementmagnification of 1 and the beam with a diameter of 2.4 mm at thewithlaservalues
oscillator calculated.
was relayed to position (B) successfully. At position
100
andcanthe Rayleighrange Z R ¼(B),
the flux
laser spot
size ogammaTheof theray
be obtained
0 was 1.2 mm
2m at the Nd-doped laser; Fig. 2(b)).
R ¼ 0.7
0 =l was 0.4 m (Zbypointegrating
theenergyspectrum measured
The new laser transport system was constructed having thisbylensthecounter.
Absorption
and NaIa ZnSe scintillation
window that transmitted
the CO
2 laser beam.
efficiencies in this energy range of the counter0
were
calculated to be 94-80% using XCOM
0
1
2
3
4MeV
4. Results and discussions
Gamma Energy [MeV]software. Taking account of these efficiencies,
laser beampassing throughnew beam transport
the ThefluxCO2andluminosity
weretheobtained.
The
Fig. 3. Gamma ray spectra measured by the Ge-detector at electron energies ofsystem was scattered by relativistic electrons in NewSUBARU and974, 1220 and 1460 MeV. The beam current was 1–2 mA and the laser power was
luminosity
attheelectronenergiesEe of 974,
Fig.1 Gamma ray spectra measured by the Gegamma rays were generated. For this experiment, the incident
1 W.
1220
MeV wasdetector at electron energies of 974, 1220 andlaser andpower1460
and electron
beam measured
current were tosetbe
to 7300
1 W and
1–2 mA, respectively. without
Energy of theagamma
ray was measuredby a1460 MeV. The beam current was 1-2 mA andphoton/W/mA/scollimator.
When
spectrarepresent
thewasconvolutionof the detector response
Ge detector (64 mm+ " 60 mm) with a high energy-resolution
the laser
power
1 W.
the
3mm
φ
collimatorwasinserted,
thefunction with the gamma ray energy distribution. As the fulland the flux was measured by a NaI scintillation counterluminosity
to high
480absorption.
(1.5-1.7MeV),
530
energy peaks are visible in Fig. 3, we determined the maximum(5 in.+ " 5 in.)becamewith relatively
Signals fromthese
energies at electron energies Ee of 974, 1220 and 1460 MeV to be
detectors were processedby a(3.1-3.9MeV)
multi-channel analyzer
and energy(2.3-2.7MeV)
and 890
photon/W/
Acknowledgments
1.72, 2.72, and 3.91 MeV, respectively. These energies are inchannels were calibrated absolutely using radioisotopes of 60Co,
mA/s
electronenergylevel.
Taking40
88at each
208
K, Y, andTl.
agreementwith values(1).
This work
was calculated
supportedusing
by Eq.
Grants-in
Aid ofinto The
account
the measured
attenuationof detector
photonsby
The flux of the gamma ray can be obtained by integrating theenergy spectraby the Geat electron
Scientific
Research (C) no. 19540419 in 2008
MeV are shownin Fig.laser
3. Thereenergies media
Ee of 974, 1220,
energy spectrum measured by the NaI scintillation counter.
severaland andthe1460
toleranceof thefromthe Ministry
Education,
Culture,was a lead collimator with a 3 mm+ hole in the front of theAbsorption
efficiencies ofin thisenergy rangeof the Science
counter were
beamalignment, we calculated theseandTechnology(MEXT),
Japan.
detector, 8.6 m from the collision point. It should be noted thesecalculated
to be 94–80%
using
XCOM software [18]. Taking
luminosities to be 7000 photon/W/mA/s
Please cite
article as: S. Amano,
et al., Nucl. Instr. andMeth. A (2009),
doi:10.1016/j.nima.2009.01.010
withouta thiscollimator,
500 (1.5-1.7MeV),
750
References(2.3-2.7 MeV) and 1000 (3.1-3.9 MeV) photon/[1] S.Amano et al., Nucl.Instr.and Meth. A 602
W/mA/s with the collimator. When the(2009) 337-341.
collimator was used, the luminosities
increased with increasing electron energy
Gamma Signal [cnt/W/mA/MeV/sec]

2

Measurements of Flux of Laser Compton Scattering
Gamma Ray Photons Generated in BL01
Ken Horikawa
LASTI, University of Hyogo
Abstract
Absolute measurements of flux of laser Compton scattering gamma ray photons generated in anelectron storage ring, NewSUBARU, with a Nd laser (1.064µm) beam was carried out by using a
GSO detector. The maximum normalized flux of gamma ray photons was found to be
6.0×103±5%photons/W/mA/sec at the beam hatch. The value obtained above was well reproducedby theoretical calculations.
Introduction
Until recently, radioisotopes have been used as asource of mono-energetic gamma ray, while thebremsstrahlung by high energy electrons has beenused as a source of radiation that has a continuum
energy spectrum. In 1963 Milburn, Arutynian, andTumanian proposed a gamma ray source using laser
Compton scattering. The idea came into reality in thelast decade as a practical radiation source as the electron accelerator technology and laser technology
were improved. [1], [2] The gamma ray source has
not only a semi-monochromaticity, but also a remarkable advantage that it forms a highly directional
and polarized beam. Therefore, a variety of applications are expected, especially for the gamma ray
photons of MeV. The laser Compton scattering
gamma ray sources are now regularly operated in
TERAS, HIγS and NewSUBARU. [3], [4] In NewSUBARU, studies on nuclear transformation treatment of nuclear waste and gamma ray imaging werestarted. [5]In this paper, we report the absolute measurementof the gamma ray photon flux in NewSUBARU.
Laser beam intensity distribution is also discussed for
maximizing the photon flux to be generated.

6.0×103±5%photons/W/mA/sec.

Absolute measurement of gamma ray photon flux
A gamma ray attenuation rate in the GSO detector
was evaluated to exceed 99% at the photon energies
of more than 6MeV by calculating the probability ofenergy dissipation due to photoelectric effect,
Compton scatterings and pair creations [6]. Therefore
it was concluded that the flux of gamma ray photons
could be observed with the accuracy of within 1%
without correcting the signal. A scattering angle of
the gamma ray to be observed is limited theoreticallywithin a solid angle which is determined by an absoreber (ABS) in the beam line in the case of NewSUBARU. The ABS is a shutter protecting a ductfrom radiations. An aperture size of the ABS is
30x20mm. The gamma ray beam size at the hatch
was limited within 30mm which was smaller than
36mm of the size of the GSO detector. Therefore, we
could make absolute measurements of the gamma ray
photon at the hatch by using the GSO detector.
The normalized photon flux was measured to be

Fig. 1 Dependence of theoretical normalized photon
number on laser focus position.

Calculated photon fluxes of the laser Compton
scattering gamma ray, and optimum laser focusing condition
Theoretical values of a total gamma ray photon
flux and a net gamma ray photon flux are shown as afunction of laser focus position in Fig. 1.

The total gamma ray photon flux is a theoreticalvalue of the gamma ray photon flux which is generated in the whole of the interaction region. The net
gamma ray photon flux is a theoretical value ofgamma ray photon flux which can be taken out in the
gamma ray hatch. The measured normalized gamma
ray photon flux is also shown in Fig. 1 for different
laser focus positions
In Fig. 1, the x symbol and the circular symbol
indicate the theoretical maximum values of the total
flux and the net flux available at the hatch, respectively. The bar symbols indicate measured values at
the hatch. The theoretical value of the net flux has ahump which is located at the focus position of about-1 m. This accords well with that of the measured
value. The net flux as a function of the laser focus
position is considered to have a distribution whosepeak is shifted to the negative side from the center in
the interaction region because the acceptance solid
angle for gamma ray increases at the negative side.
It is concluded that by taking into account the acceptance angle the measured net flux agrees well withthe theoretical one and the optimum laser focus position for maximizing gamma ray generation can bewell predicted by the theoretical calculation describedabove.
Conclusion
The absolute measurement photon flux of Ndlaser Compton scattering gamma rays was carried out
by using a GSO detector in which the gamma ray
attenuation rate was over 99%. The maximum normalized photon flux of the gamma ray was found to
be 6.0×103±5%photon/W/mA/sec at the hatch. Theoretical calculations of laser Compton scattering
gamma ray photon flux were done by taking into account various parameters, and the measured net flux
agreed well with the theoretical one. It is concluded
that the optimum laser focus position for maximizing
gamma ray generation can be well predicted by thetheoretical calculation obtained in this study.
Reference[1] Richard H. Milburn, Phys.Rev.Lett.10, 75 (1963).
[2] F. R. Arutyunian, V. A. Tumanian, Phys.Lett.4,
176 (1963).
[3] H. Toyokawa, H. Ohgaki, T. Mikado, K. Yamada,
Rev.Sci.Instrum.73, 3358 (2002)[4] S. Miyamoto, Y. Asano, S. Amano, D. Li, K.
Imasaki, H. Kinugasa, Y. Shoji, T. Takagi, T. Mochzuki, Radiation Measurements 41, 179 (2007)[5] D. Li, K. Imasaki, S. Miyamoto, S. Amano, T.
Mochizuki, J. Nucl. Sci. Technol., 42, 259 (2005)[6] XCOM: Photon Cross Sections Database(http://physics.nist.gov/PhysRefData/Xcom/Text/XC
OM.html)

Characteristics of EUV light and ion emissions
from a micro lithium target
Akihisa Nagano and Takayasu Mochizuki
LASTI, University of Hyogo
Abstract
Characteristics of extreme ultraviolet light and ion emissions from a micro lithium target were
investigated by using a double pulse irradiation. The EUV and ion emissions were enhanced by afactor of about 2~3 with a pre-pulse against that without the pre-pulse. Additionally, a number offast ions were reduced at the pre-pulse. These results confirm that the double pulse method isuseful to obtain a uniform plasma and optimize the plasma size.
1. Introduction
A high power 13.5 nm light source is underdevelopment for the application to extreme ultraviolet
1(EUV) lithography . Major technical issues on the
EUV source are improving an EUV conversion
efficiency (CE) and suppressing the degradation of acondenser mirror by target debris, as well as
developing a high-average-power pulsed laser. In a tin
target, the CE is intrinsically high because major
8+13+
EUV emissions from the tin ions of Sn to Sn ,2concentrate around 13.5 nm . However debris
deposition or damage on the mirror, thus cleaning of
the mirror would be the most critical issue to besolved in case of heavy metal targets such as tin
targets. Alternatively, lithium (Li) metal debris will
not deposit on the mirrors if they are maintained at ~3,4
400 ℃ and in addition a Li target has intrinsicallya high spectral efficiency because of an intense line2+
emission (1s-2p) in excited Li ions at 13.5nm. In
the case of using Li planar target, We demonstrated
an improvement of CE by a forced recombination
scheme and optimization of incidence laser
5,6
wavelength .
Figure 1 shows an example of the practical forced
recombination target. In this system, target materials
are supplied continuously as liquefied Li such asfilament jet or micro droplet. The recombination
emissions near the wall can be also utilized.
Therefore the target plasma should be uniformly
heated because it needs to generate the plasma
flowing toward the wall. In this paper, we report on
characteristics of both EUV light and ion
emissions from lithium micro targets by using a
7
double pulse method .
2. Experiments and results
Figure 2 shows an experimental set-up. The
experiments were carried out by using twocommercial Nd:YAG lasers which were aSpectra-Physics Quanta-ray Pro-230 Series (SP) and a
Quantel YG981C-10 (Quantel). The SP laser and the
Quantel laser delivered a 1064nm wavelength laser
pulse with pulse durations of 10~12 nsec and about 8
nsec, at full width at half maximum, respectively.
Laser pulses were focused on micro Li target througha focal lens which had a focal length of 500mm in a-3

vacuum chamber kept at about 4×10 Pa. Li-coatedglass micro balloons (GMB) with a diameter of about
100µm were used as the micro targets. Li layer wasformed on GMB surface with a thickness of 5~8µm
by a vacuum deposition. EUV intensities were
measured by calibrated EUV calorimeters. They were
mounted at angular positions of -15˚, -90˚, 60˚, 125˚,
and 160˚ to measure angular distributions of theemission. The emitted ions were measured by using
charge collectors mounted at angular positions of 20˚,
70˚, and -160˚ at a distance of 140mm from the target.
The EUV emission image at 13.5nm was monitoredby an EUV camera which was consisted of imaging
optics using two Mo/Si multilayered mirrors and aback-illuminated x-ray charge coupled device camera.
An emission spectrum was monitored by a grazing
incidence spectrometer mounted at angular positionof 40˚ to the laser axis.

Fig. 1 An example of practical forced
recombination target geometry.

Fig.2 Experimental set-up.
Characteristics of EUV and ion emissions were
investigated by using a double pulse irradiation. The
incident energies of pre (SP) and main (Quantel)

pulses were 0.15 and 0.5J, respectively. In thisexperiment, both laser pulses irradiated the target
coaxially from the same direction with an about
400µm focal spot diameter.
The optimum pulse separation in time was foundto be about 50 nsec. Angular distributions of EUV
and ion emissions are shown in Fig. 3. With thepre-pulse, the EUV and ion emissions were enhanced
by a factor of about 2 at the region from -60˚ to
60˚and a factor of about 3 at the rear side of the target
against laser illumination. We evaluated the kinetic
energy spectra of the Li ions from the charge collector
signals with and without the pre-pulse. The
maximum kinetic energies are ~1.5keV and ~1.7keVwith and without the pre-pulse, respectively.
Furthermore a number of fast ions were reduced at the
pre-pulse. At the energy of 1keV, they were found to
be about one third of that without the pre-pulse. EUV
emission images were obtained with and without the
pre-pulse. The image size with the pre-pulse wasabout two times larger at the delay of 50 nsec thanthat without the pre-pulse.
These results confirm that the double pulse
method is useful to obtain a uniform plasma andoptimize the plasma size.
(a)

(b)

Fig. 3 Angular distributions of EUV(a) andion(b) emissions.

References[1] EUV sources for Lithography, edited by V.

Bakshi SPIE, Washington, 1-1044, ISBN:
0-8194-5845-7 (2005)[2] P. Hayden, A. Cummings, L. Gaynor, N.
Murphy, G. O’Sullivan, P. Sheridan, E. Sokell,
J. White, and P.Dunne, Proc. of SPIE 5751, 919(2005)[3] H. Takenaka, T. Kawamura, and T. Haga, OSATOPS Extreme Ultraviolet Lithography 4, 169(2005)[4] D.W. Myers, I.V. Fomenkov, B.V.M.
Hansson, B.C. Klene, and D.C Brandt, Proc.
of SPIE 5751, 248 (2005)[5] A. Nagano, T. Inoue, P. E. Nica, S. Amano, S.
Miyamoto, and T. Mochizuki, Appl. Phys. Lett.
90, 151502 (2007)[6] A. Nagano,T. Mochizuki, S. Miyamoto, and S.
Amano, Appl. Phys. Lett. 93, 091502 (2008)[7] R. Kodama, T. Mochizuki, K.A. Tanaka, and C.
Yamanaka, Appl. Phys. Lett. 50, 720 (1987)

Mitigation effect of plasma debris from cryogenic xenon
target by argon buffer gas
T. Inoue, K. Masuda, S. Amano, T. Mochizuki
LASTI / UH
Abstract
In order to mitigate the sputtering effect on collection mirror which was caused by xenon fastdebris, mitigation effect on plasma debris from the rotating drum xenon cryogenic target by anargon buffer gas and also absorption of soft X-ray from the plasma investigated. The sputtering
caused by the fast xenon debris was reduced by 1/18 with an argon buffer gas of 8 Pa. The
damping of the X-ray by introducing the argon buffer gas was measured to be about 0.75 % /Pa fora flight pass of 190 mm on these argon pressures. These results suggest that the plasma debris arewell mitigated by an argon buffer gas without suffering from a serious loss of X-ray due to theoptical absorption by the argon buffer gas.

Introduction
X-ray source generated from laser produced
xenon plasma has a broad-band spectrum, and it
would become a compact and high power soft X-ray
source. In order to use this light source for a lot ofapplications, high average output power andreduction of condenses mirror damage by plasma
debris are required. A high average output power wasachieved by using a rotating drum xenon cryogenic
target[1] and a 100W/320pps Nd:YAG slab laser
system[2]. That was 20W into 2π for a wavelength
range of 5 nm to 17 nm. Furthermore a focusing ofsoft X-ray was accomplished by using a cylindricalruthenium mirror system under the condition of
single laser pulse radiation. By setting up the system
at a place that could collect the X-ray power, soft Xray intensity at a focal point was improved by 46times of that without the system[3]. However to use
this mirror system at the operation condition of
100W/320pps, the mirror sputtering effect must be
mitigated. Because, if we would operate the laser at
100W/320pps without debris mitigation, the mirror
would be sputtered at a high rate of about 10nm/
min[4]. To mitigate the sputtering effect, we introduce
an argon buffer gas. Argon has a spectral peak at
3.2nm[5] which deviates from xenon peak of 10.8nm.
Thus an absorption ratio of soft X-ray from xenon
plasma by argon gas was about 1/10 of a selfabsorption ratio of soft X-ray from xenon plasma by
xenon gas on the same pressure.
In this paper, we report on a mitigation effect on
plasma debris from the rotating drum xenon
cryogenic target by an argon buffer gas and also
report on the absorption of soft X-ray from theplasma by argon.

about 500µmΦ, and 10pps or single pulse operation.
A drum was operated at a rotating speed of 130rpm
and a vertical velocity of 3mm/s in 30mm width. A
thickness of xenon layer was adjusted about 500µm
and fresh surfaces were supplied in each shot. An
argon buffer gas was supplied from a top of vacuum
chamber. To evaluate a debris mitigation effect by thegas, we measured a sputtering rate in a gold film
coated on a Quartz Crystal Micro-balance (QCM)
which was mounted at 45 degree and a distance of 77
mm from a plasma source point. Soft X-ray energy
was measured by an X-ray calorimeter at -22.5deg
and a distance of 190mm from the source. The
positions of these two instruments were determined,
where a collection mirrors system should be set up.
The xenon partial pressure was kept less than 0.2Pa
during the experiment by a turbo-molecular pump
mounted on the underside of a vacuum chamber.
Laser
X-ray
calorimeter
QCM

sampleCollection
mirrors
system

Fig.1 Experimental setup
Experiments and Results
Fig.1 shows the experimental setup. A Q-switched
1.06µm Nd:YAG laser pulse was focused on arotating drum xenon cryogenic target at incident
normal. Laser pulses were irradiated with a energy of
0.3 J, a pulse duration of 8 ns, a focusing spot size of

Fig.2, 3 show the sputtering mitigation effect and
the X-ray attenuation rate as a function of the argon
partial pressure. The sputtering by the fast xenon
debris was reduced by 1/18 with an argon buffer gas

of 8 Pa. The attenuation of the X-ray by the argon
buffer gas was measured to be about 0.75 % /Pa for aflight pass of 190 mm on these argon pressures.
These results suggest that the plasma debris are well
mitigated by a argon buffer gas without sufferingfrom a serious loss of X-ray due to the opticalabsorption by ones.

Fig.3 soft X-ray attenuation rate as a functionof partial pressure.

Fig.2 mitigation effect on gold film sputtering
rate as a function of argon partial pressure.
The vacuum pressure was corrected as argon
gas.

References[1] K.Fukugaki et al , Rev. Sci. Instrum. 77, 063114(2006)[2] S.Amano et al , Rev. of Laser Engineering, Vol.
29, pp.679-682 (2001)[3] K.Masuda et al , Lasti Annual Report, vol.9,
pp40-41 (2007)[4] K.Masuda et al , The Japan Society of Applied
Physics and Related Societies, The 56th Spring
Meeting, 30p-ZR-9 (2009)[5] T.Mochizuki et al , Proc. SPIE 3886, 306 (2000)

PTFE Processing Characteristics of High-energy
X-ray and Application to a bio-microdevice
Yoshiaki Ukira and Yuichi Utsumi
Abstract
This paper reports the smoothing effect of poly-tetrafluoroethylene(PTFE) by using high-energy
X-ray. The roughness of surface was drastically decreased down to (Ra=5.6nm) form native
surface roughness (Ra=93.5). The another attempt of the application to bio-microdevices isreported. The immunoassay for poly-chlorinatedbiphenil (PCB) is demonstrated by immobilizing
1st antibody on the surface of PTFE microstructure.

Smoothing of PTFE Induced by X-ray
irradiation
It is known that SR induces the scission ofpolymer chain of polymers due to inner shell andvalence electron photo excitation [2]. The
decomposed
photochemical
products, which
generated by high-energy x-ray irradiation,
continually desorb from surface of the substrate,
which results in the ablation of PTFE, while there
induced recombination of radials in the bulk. It has
been known that CFx ions are the dominantdecomposed species of soft x-ray irradiated PTFE
from mass spectrometry (MS) investigation [3]. We
found the stoichiometry of PTFE is maintained evenafter the exposure as shown by the result of x-ray
photoelectron spectroscopy. Next notable property isthat the roughness of PTFE surface is greatly
decreased by SR irradiation at the elevatedtemperature above 100 oC as shown in Fig. 1 andFig.2. The origin of these phenomena areinvestigated in this work. We considered that themelting point of PTFE during SR irradiation becomes
lower than normal (327oC) due to continual photofragmentation in the deep PTFE bulk induced by

Ra = 93.52 nm

Ra = 39.08 nm

Without exposure

Ts = 104 oC

Ra = 5.63 nm

Ra = 21.75 nm

Ts = 149 oC

Ts = 200 oC

Figure 1 AFM images of x-ray irradiated PTFE surfaces. The
dose condition were fixed at 200 mAhr
70

Surface roughness (nm)Introduction
Poly-tetrafluoroethylene (PTFE) is very
attractive material for various fields including
micro-electro mechanical systems (MEMS),
RF-MEMS, and lab on a chip, because of its
chemically stable, thermal and electrical good
insulating, bio-convertible and low friction
properties. However, it is difficult to fabricate
PTFE microstructures with conventional
techniques such as semiconductor process or
micromachining. On the other hand we had
succeeded in the fabrication of high-aspectratio microfluidic parts of PTFE by direct invacuum photo-etching using synchrotron
radiation (SR) with high-energy of soft X-ray
ranging in 2-12keV [1]. This paper reports a
new finding of processing characteristics
brought by using relatively high-energy X-ray
irradiation on to the PTFE and application to
the immunoassay system.

60
50
40
30
20
10
0

40

60

80 100 120 140 160 180 200 220

Substrate temperature (oC)

Figure 2 Dependence of surface roughness on substratetemperature

high-energy x-ray, and this leads the liquescence ofthe solid PTFE. The liquefied PTFE flows into
porous textures of the bulk and only irradiated part ofmaterial is continuously etched specifically. It is
speculated highly decomposed photoproducts such as
CF, CF2 will be generated due to inner shell
excitation, which leads to the sustain of
stoichiometry and achievement of remarkable highaspect ratio of etching above 100, which confirmed
for the first time by using the high energy x-rays ofSR.
Application to a Bio-microdevice
In the case of conventional ELISA, polystyrene(PS) is standard material to immobilize the antibody,and it is also used for the lab on a chip as solid phaseby using PS microbeads. However, it is expected thatthe use of PTFE microstructures bring great benefit
for the application of lab on a chip to the system

with concentration of PCB suggests successful
detection of PCB.

Regents
3 mm

Anti PCB
antibody

40µm
E

PCB

E

400µm
E

Vertical
reactorE

HRP
conjugate
HaptenE

PTFE capillarybundle structure

Regents withproducts

Figure 3 Schematic illustration of antibody-bound capillarybundle structure and vertical microreactor unit

1.4
1.2

B/B0

1
0.8
0.6
0.4
0.2
0
0.1

1

10

100

1000

PCB conc. (ng/ml)
Figure 4 Calibration curve of PCB obtained by competitive
ELISA

using organic solvent, such as immunoassay of polychlorinatedbiphenyl (PCB). On the other hand we
proposed the high-sensitive immunoassay systemusing capillary bundle structure [4]. In this system
the high-aspect ratio polymethylmethachryrate(PMMA) capillary bundle structure is fabricated bydeep x-ray lithography and antibodies areimmobilized on the PMMA capillary bundle structure.
In this paper PTFE capillary bundle structure is used
for better stability in organic solvent. As shown in theFig. 3, anti-PCB antibody-bound PTFE capillarybundle structure is stacked into vertical microreactor
and competitive ELISA is carried out in the vertical
microreactor [4]. The large surface area of capillarybundle structure is effective to immobilize muchantibody than normal microchips using microbeads
or microchannels. For the competitive ELISA the
standard sample of PCB is prepared by solving into
organic solvent (dimethylsulfoxide: DMSO). The
sample is mixed with hapten (enzyme-labeled PCB
like matter) solution. Then mixture is injected into
the antibody-bound capillary bundle structure andincubated for competitive antigen-antibody reaction.
After the reaction, the substrate (tetramethylbenzidin:
TMBZ) is injected into the capillary bundle structureand enzyme catalyze the degradation of TMBZ. Afterthe incubation of enzyme reaction the reaction isaborted by 1N H2SO4 solution and amount of
product is measured in the microchip. Figure 4 shows
the obtained calibration curve, and decreasing signal

References[1] Y. Ukita, K Kanda, S. Matsui, M. Kishihara, andY. Utsumi, Jpn. J. Appl. Phys., Vol. 47, No. 1A , 337– 341, (2007).
[2] M. C. K. Tinone, K, Tanaka, J. Murayama, N.
Ueno, M. Imamura, and N. Matsubayashi, J. Chem.
Phys. 100, 5988 (1994)[3] J. K. Simons, S.P. Frigo, J.W .Tayler,
R.A .Rosenberg, J. Vac. Sci. Tachnol. A 12 681689,(1994)[4] Y. Utsumi, T. Asano, Y. Ukita, K. Matsui, M.
Takeo, and S. Negoro, J. Vac. Sci. Technol. B, 23,2903-2908 (2006)

High density cell culture using micro 3D scaffold
With capillary bundle structure
Tomoya Omukai*, Atsushi Kinoshita**, Fusao Komada** and Yuichi Utsumi**Laboratory of Advanced Science and Technology for Industry, University of Hyogo, Japan**Faculty of Pharmaceutical Sciences, Himeji Dokkyo University, Japan
Abstract
We have proposed a method for high cell culture throughput by means of a micro 3D scaffold anddensity with high surface-to-volume ratio, and have successfully demonstrated that the throughput
and density of cell culture significantly increased under a finite regime of scaffold size andfiguration. We have succeeded in obtaining high density cell culture and also found that the sizeand figuration of capillaries in the micro 3D scaffolds significantly affect cell culture and surface
adhesion.

Introduction
The conventional cell culture method for
producing monoclonal antibody and therapeuticprotein has remained the batch process, a process
which is very time consuming due to its sorting
and refinement complexity. Therefore cell culture
throughput using a flat cell culture dish is limited.
We have proposed a method for high cell culture
throughput by means of a micro 3D scaffold anddensity with high surface-to-volume ratio, andhave successfully demonstrated that thethroughput and density of cell culture
significantly increased under a finite regime ofscaffold size and figuration. The scaffold can also
be used as a bioreactor with combinatorial
systems of cells and their useful products.

Evaluation qualitatively of 3D cell culture
We qualitatively evaluated the property of celladhesion to a micro 3D scaffold of Poly Methyl
Methacrylate (PMMA) fabricated by deep X-ray
lithography as shown in Fig. 1 [1]. The scaffold
consists of capillaries with different cross sectional
sizes and figurations ― honeycomb, diamond,
pentagon, and circle. HepG2 cells transfected with
pEGFP vector encoding Enhanced Green
Fluorescent Protein (EGFP) were used to evaluate
cell culture density by laser scanning microscope.
As shown in Fig. 2 (a), (b), (c), and Fig.3,
cultivated cells adhered to the inner-surface of thecapillaries of the scaffold; however, cells did notadhered to the surface of the circle shapecapillaries (Fig. 2 (d), 4). Thus, cross sectional
figuration is shown to strongly influence celladhesion. We also found the cross sectional size ofthe scaffold affects cell cultivation and adhesion.
These findings suggest that competition between
the supply of medium culture and excretion of
metabolic products affects cell activities.

12mm

Fig.1 SEM image of PMMA 3D microstructure withcross sectional figuration of honeycomb capillarybundle.
(a)

(b)

(c)

(d)

Fig. 2 Fluorescence images of 3D-cultivated cell
adhered on scaffolds from various capillaries withcross sectional figuration of (a) honeycomb, (b)diamond, (c) pentagon, and (d) circle on day 3.

(a)increases for the smaller size cross sectional
capillaries in the scaffolds.

(b)▲: honeycomb 50 μm, △: honeycomb 100 μm■: honeycomb 150 μm, □: honeycomb 200 μm◆: honeycomb 300 μm, ●: flat PMMA

100μm

Amount of GFP (μg)

10Fig.3 Fluorescence images of 3D-cultivated cell
adhered to honeycomb capillaries by laser scanningmicroscope on day 4. (a) bottom view, (b) side
view.

(a)

8
6
4
2
0

3

12

15

18

21

Fig.5 Time course for the quantity of cell culture
with scaffolds from capillaries with honeycombcross sectional figurations. (each point represent
mean ± SD, n=3-8) The honeycomb capillary
pattern has a side length of 50 to 300

Amount of GFP (μg)

1010Evaluation quantitatively of the 3D cell culture
Based on the above results, we evaluated thequantity of 3D cell culture in the capillaries of the
micro 3D scaffolds with honeycomb and diamondcross sectional figurations over the course of
several days. By determining the amount of GFP
in cells, we measured the quantity of 3D cell
culture which we then compared with flat plate
PMMA results, as control. As shown Fig. 5, whenusing micro 3D scaffolds the cell number and theamount of GFP tend to increase, for the smaller
size honeycomb capillaries; smaller the pattern, thegreater the number of capillaries and the larger thesurface area. All patterns showed a peak GFP
amount at 10 or 12 days, suggesting the depletionof medium culture in the capillaries after the
maximum cell multiplication. Moreover, we
calculated the amount of GFP in each figuration
per surface area of capillary and found that theamount of GFP per surface area of capillary

9Time (day)(b)

Fig.4 Fluorescence images of 3D-cultivated cell
adhered to circle capillaries by laser scanningmicroscope on day 4. (a) bottom view, (b) side view.

6■: diamond 30°, ◆: diamond 45°▲: diamond 60°, ●: flat PMMA

88
66
44
22
00

33

66

99

12
12

15
15

18
18

21
21
21

Time (day)Fig.6 Time course for the quantity of cell culture
with scaffolds from capillaries with diamond crosssectional figurations. (each point represent mean
± SD, n=3-8) The diamond capillary pattern has ainner angle of 30 to 60 degree.
Conclusion
We have succeeded in obtaining high density cell
culture and also found that the size and figurationof capillaries in the micro 3D scaffolds
significantly affect cell culture and surface
adhesion. These results suggest that micro 3D
scaffolds consisting of capillaries with optimized
structure parameters are able to control cell
culture figuration and increase culture density.

References[1] Y. Ukita, T. Asano, and Y. Utsumi, Microsystem
Technology, 13, 435 (2007).

Fabrication of electrodes for multiplex nerval interface
M．kato1，Eric．Blasius 2，Y．Ukita1,3,K．Mabuchi4，Y．Utsumi1
1

Laboratory of Advanced Science and Technology for Industry, University of Hyogo
2
University Karlsruhe
3
Research Fellow (PD), Japan Society for the Promotion of Science
4
The University of Tokyo

Abstract
The “flexible regeneration type nerve electrode” is an interface device for nerves, connecting nerve fibers
to signal conducting lines on a micro structure, making it usable for “Microneurography”. Our chips
buildup is based on multiple PDMS (Polydimethylsiloxane)-layers.

1, Introduction“Microneurography”, developed by Karl-Erik
Hagbarth and Ake B. Vallbo, is a technique forreading and manipulating nerve signals by tools,
acting as “nerve signal interfaces” [1]. Today’s
applied “Microneurography” uses needle shaped
tungsten structures as electrodes measuring
nerve signals. This is achieved by penetrate anerve fiber, intending to reach the core of thenerve with the tip of these structures. Commonly
applied “Microneurography” has disadvantages
such as difficult implantation, difficult
positioning and unprecise readout of nerve
signals due to macroscopic scale. Mentioned
disadvantages render these methods unusable forpractical medical services. The “flexible
regeneration type nerve electrode” proposed by
K Mabuchi from Tokyo University is aninterface device for nerves, connecting nerve
fibers to signal conducting lines on a micro
structure,makingitusablefor“Microneurography” [2]. We rely on theregeneration ability of nerves by cutting one,
putting our chip between the nerve ends andforce it to grow together through our chip
structure. Figure.1 shows the model of nerve
reproduction electrode.

2. Design
Figure 2 shows the outline of the nerve
regeneration electrode It is difficult to integratemany electrodes by using single layer due tosmall area. Thus the electrode shape is designed
to be stacked allowing three-dimensional (3D)
crossing of multiple electrode lines. For the firstattempt, designed electrode structures have 12channels electrode on a single layer and total 24channels are realized by stacking two layers,
however the electrode lines are not crossing due
to coupling to our connector. Next, the capillary
diameter is designed. 30 µm in diameter
capillary structures were designed to allow thenerves to pass through due to minimum diameter(20 µm) of nerve fibers. Moreover, the capillary
diameter of 60 µm and 90 µm were designed,
which capable two or three nerves in a capillary.
The width of the electrode line was designed as
20µm by considering impedance and capillarydensity. Moreover, lines are spaced 20 µm to
avoid the influence of noise such as leak current.
It is also important for better detection of signals
torealizegoodinsulation
betweenthree-dimensionally stacked layers.

electro code
silicon tube

regenerating axons

proximaldistalnerve stumpnerve stumphole with recording site
Figure, 2 Outline of electrode
Figure.1 Model of nerve reproduction electrodeProcessing rate [μm/Hr]

3. Experiment
To form PDMS through hole structure pillar
pattern is formed to transfer the opposite patternon the PDMS film, by replication process. Firstof all, 40 nm thick Ti film is deposited on brass
substrate by means of spatter for chemicallystable surface and better adhesion of photoresist.
Photoresist (AZP4903: AZ Erectronic Materials
co. Ltd) is courted on the Ti layer and electrodeline pattern is formed on the layer. Next 5 µm
thick Au electrode line structure is filled in theline by means of electro plating. After removalofAZ
resist,photoresist(KMPR1010 :KAYAKU Microchem Co. Ltd)is courted on the electrode pattern with thicknessof 40 µm. Then pillar pattern (opposite capillary
pattern) is formed on the electrode pattern byaligning the photomask on the electrode pattern.
After photolithography PDMS resin isspincourted on the pillar pattern to cover 30 µm
in thickness and cured. To form through hole
structure, by removing PDMS thin film on thepillar pattern, PDMS is etched by reactive ion
etching (RIE) with CHF3 and O2 gas source.
For accurate processing depth control of PDMS,
we investigate the processing properties of
PDMS by using RIE etching. [3] Especiallyprocessing rate of the PDMS layer strongly
depends on the relaxation process time, which isinterval time between curing of PDMS andetching process. As shown in figure 3 theetching rate is exponentially decreasing withrelaxation.
35
Measured processing rate
Exponential fitting

30
25
20

than polymerized structures.
Then KMPR pillar pattern is removed byremoving process. In the removing process thesubstrate is dipped into Remover PG(KAYAKU
Microchem Co. Ltd) then dipped again into
Remover K(KAYAKU Microchem Co. Ltd).
Finally brass substrate is etched in etchant (Cu3931: Meltex .Inc) and freestand PDMS
electrode chip is fabricated.
As shown in the figure 30 µm thick through hole
structures are successfully formed on the PDMS
thin film, and optical image o the electrode isshown in the figure 4.

Figure.4 optical image on the electrode4．Conclusion
The 3D stacked type regenerated nerve
electrodes are proposed and trial fabrication isdemonstrated. The through hale structure isformed on the PDMS thin film. The dry etchingprocessing rate was strongly depends on theinterval time between the PDMS curing andetching process. We are aiming to bond multiple
electrode layers to complete the process for theapplication to the nerval interface.
Reference[1] Åke B. Vallbo, Karl-Erik Hagbarth, and B.
Gunnar
Wallin,J.
Appl.
Physiol.,“Microneurography:
howthetechniquedeveloped
0
5
10
15
20
25
and its role in the investigation of the sympathetic
Relaxation time [Hr]nervous system” ,96,1262–1269 (2004)
Figure.3 PDMS etching Graph Processing rate-Relaxation time [2] Takafumi Suzuki, Takashi Saito, Kunihiko
Mabuchi, “Development of a multi-channel nerve
This is speculated that unstable chemicalelectrode for peripheral nervous system” ,Technicalreport of IEICE, 100, 63-66 (2000)
property of PDMS is contributing on the shift of[3] Nara, Y. Sugino, H. Arakawa, T. Shirasaki,
etching properties. In the early stage ofY. Funatsu, T.
Shoji, S. , ” High Through-Put
relaxation, there is a lot of monomer, which does
Parallel
Biomolecules
Sorting Microsystem withnot cross-linking by polymerization and theThreeDimensional
PDMS
Stack”,
small monomer expected to be much volatile
10.1109/SENSOR. 257-260 (2007).
15

Cross-linked capillary micromixer for high-sensitive
immunoassay
Saki Kondo1 , Yosiaki Ukita1, Kuniyo Fujiwara1, and YuichiUtsumi1
Laboratory of Advanced Science and Technology for Industry University of Hyogo1,
3-1-2 Kouto, Kamigori, Ako-gun, Hyogo, 678-1205, JAPAN, Tel: +81-791-58-0232,

Abstract
A novel micromixer is proposed, fabricated and verified. The new concept of the micromixere is tocross-link the many capillaries in three-dimensional structure. The characteristic flow behaviors
are simulated by using computational fluid dynamics (CFD) software”FLUENT”. The results of
the CFD shows unique mixing behavior in three-dimensionally cross-linked capillaries. The
mixing performance of the micromixer is strongly influenced by controlling the three-dimensionalcrossing condition. The micromixer is fabricated by means of deep X-ray lithography with multi
step exposure. The cross-linked capillary structures are successfully fabricated with controlled
cross-link conditions. The performance of micromixer is evaluated by using a kind of enzyme
reaction. By comparing mixture, mixed with cross-linked fluid filter and fluid filter without crosslinked capillaries, we found out the speeding up of the reaction by using new micromixer.
(a)

(b)

Introduction
The micromixing is one of the mostimportant issues in the field of lab on a chip
[1,2]. The quality of mixing will be very
influential for the result of analysis; the use of
non-uniform mixture will result in nonreproducible results and the use of uniform
mixture will result in better results. This
paper shows a unique micro mixing behavior
in three-dimensional microstructure and its
application to chemical reaction.
Simulation and Result
The new concept of this paper is to crosscapillaries by controlling overlap level of crossing
capillaries. The computational fluid dynamics (CFD)
using CFD software ‘FLUENT’ is carried out toestimate the performance of the micromixer. To trace
the mixing behavior, chemical species is assumed ininitial condition. We assumed two crossing patterns
which totally overlapping (fig. 1(b’,d)) and half
overlapping (fig. 1(c’,e)) patterns and capillaries
without crossing for control (not shown). Figure 1
shows initial condition of water (Fig. 1(a)) withchemical species (the property is the same as water)and mixed waters through cross-linked capillaries(Fig.1(b,c), the close ups of the cross-linked structure
are shown in Fig.1(b’,c’)), and fig. 2 shows the time
shift of the standard deviations (SD) of mass fractionof chemical species in the mixture. The results
indicate that the crossing structure has much better
mixing performance and half overlapped structure
provides the best mixing, because it induces branchof flows around the cross (fig. 1(e)) while totallyoverlapped one does not exhibit such behavior
because it maintains the stable laminar flow (fig.
1(d)).

(b’)

(d)

(c)

(c’)

(e)

Streamline with reflecting behavior at crossStreamline with passing behavior at crossFig.1 Simulated mixing behavior using CFD. Color bar
indicates mass fraction of chemical species. (a) Chemical
species is imaginary separated from water at initialcondition. (b) Mixture obtained totally overlapped crosscapillary structure and (c) mixture obtained half
overlapped cross capillary structure. (b’)(c’) is showedenlarged view part of (b)(c) circle. (d) illustrates flow
behavior in totally overlapped cross capillary
structure ,(e) illustrates half overlapped cross capillary
structure. Half overlapped structure induce branch of
streamline due to un-overlapped part of cross.

400µmCapillary form
Full overlapped
Half overlapped
Without crossing

0.0000 0.0002 0.0004 0.0006 0.0008 0.0010

Time [ｓ]Fig.2 Time shift of standard deviation of massfraction of red species.
Fabrication and Evaluation
Typical micromachining is not suitable to fabricate
the cross-linked capillary structure, because it needs
very complex processes control the level of overlap.
To generate the cross-linked structure, deep X-ray
lithography is applied. The PMMA resist attachedwith X-ray masks are tilted up to X-ray beam for first
exposure and then tilted down for second exposed.
The level of overlap is controlled by slightly rotating
the masks around normal axis. Figure 3 shows thescanning electron microscope (SEM) image of
fabricated micromixer with half over lapped structure.
The complex 3D microstructure with twice crossing
is successfully formed on thick PMMA resist by justexposing twice and developing.
To verify the mixing effects on chemical reaction,
we applied this micromixer to enzyme reaction.
Enzyme and substrate are mixed by passing the
micromixer and the product of the enzyme reaction ismeasured by spectroscopy. Figure 4 indicates time
consumption for saturation of reaction yield. The
speed of the reaction is drastically speeded up and theerror bar is drastically decreased by using crosslinked structure, and it means that cross-linked
structure reproducibly provides uniform mixture.
Conclusion
These results indicate that the micromixter withcross-linked capillary structure has much higher
mixing performance. It is considered that thecharacteristics of this micromixer is effective not
only speed up of the reaction but also reproducibility
and sensitivity of the assay by using reproducible
mixing. And this micromixier is considered that very
useful for pre mixing module for biological reaction
such as enzyme linked immunosorbent assay(ELISA). Further more, the antibodies for
immunoassay can be immobilized onto the surface ofcross-linked capillary structure. By using the large
surface area of cross-linked capillary structures the
enzyme reaction of the ELISA will effectively
amplified and it can result in higher sensitivity [3, 4].

Fig.3 SEM images of cross-linked capillary bundle
structure (half overlapped type)Time of saturation [sec]Standard deviation

0.50
0.45
0.40
0.35
0.30
0.25
0.20
0.15
0.10
0.05
0.00

10
8
6
4
2
0

With 1 Without
cross
cross

Fig.4 The time of saturation. The error bars
indicate standard deviation. Groups are 4 and 5
for with cross and without cross, respectively.

References[1] Chien-chong Hong et al., Lab Chip,4,
pp.109(2004)[2] Robin H. Liu et al., jmemsv, 9, pp.190(2000)[3] Y. Utsumi et al., J. Vac. Technol. B, 24,
pp.2606(2006)[4] Y. Ukita et al., Sens. Actuators A, 145,
pp.499(2008)

Resolution enhancement of EUV microscope using an
EUV beam splitter
Masafumi Osugi1,3 Kazuumi Tanaka1,3 Noriyuki Sakaya2,3 Kazuhiro Hamamoto2,3
Takeo Watanabe1,3 and Hiroo Kinoshita1,3
1 LASTI/UH, 2 HOYA Corporation R&D Center, 3 CREST-JST
E-mail: kinosita@lasti.u-hyogo.ac.jp

Extreme ultraviolet lithography (EUVL) has been
proposed as a next generation lithography at the 32
nm node around 2009. In the technology, defect-freemask is one of the critical issues. Consequently, wedeveloped EUV phase-shift microscope (Figure 1) todetect such as phase-defect in multilayer mask1). And
we have developed the EUV beam splitter, which is
critical component of phase-shift inspection or
resolution enhancement. The optical system portionof an EUV microscope is shown in Figure 2. In this
optics, as NA becomes different number between
longitudinal and tangential direction, resolution
decreases in one direction. However, by installing
EUV beam splitter above Schwarzschild optics, NA
becomes uniform for all planar direction andresolution improves (Figure 3).
Figure 4 shows fabrication process of EUV beam
splitter2). In this process, stress control is important at
depositing multilayer. We controlled by changing ofRF power, DC power, and the Ar working pressure.
We could fabricate multilayer of low tensile stress bycounteracting tensile stress of molybdenum film andcompressive stress of silicon film.

Figure 5 shows the exposure results of elbow
pattern of 300 nm in size. Before installing beam
splitter, lines of vertical direction could not be
resolved(a). However, after installing beam splitter,the 300-nm L＆S elbow pattern for all planar
direction(b) has been clearly resolved. Figure 6
shows the close up of these patterns in horizontal(a)and vertical(b) directions.
We have developed an EUV microscope with abeam splitter for the first time and succeeded in thehighly precise pattern inspection.
References
1. K. Hamamoto, Y. Tanaka, S.Y.Lee, N.Hosokawa,
N.Sakaya, M.Hosoya, T,Shoki, T. Watanabe and H.
Kinoshita,J. Vac. Sci. Technol, B23(6), Nov/Dec(2005) 2852
2. Y. Mizuta, M. Osugi, J. Kishimoto, N. Sakaya, K.
Hamamoto, T. Watanabe, H. Kinoshita SPIE 6517
(2007) 113

Fig. 1. Configuration of EUV phase-shift microscope.

Figure 2. Configuration of Schwarzschild
opticsFigure 3. Configuration of
Schwarzschild optics installed EUV
beam splitter

Figure 4. Fabrication process of EUV beam splitter splitter(a)Turning mirror(b)Installed beam
splitterFigure 5 300-nm elbow pattern before(a) andafter(b) installing EUV beam splitter(a)Horizontal lines(b)Vertical lines

Figure 6 Close up of Figure 5(b)Dual grating interferometric lithography for 22-nm node
Hideaki Shiotani 1, Shota Suzuki 1, Dong Gun Lee 2, Patrick Naulleau 3,
Takeo Watanabe 1, Yasuyuki Fukushima 1, Ryuji Ohnishi 1, and Hiroo Kinoshita 1
1 LASTI/UH, 2 Photomask Team, Memory Development Business Division, Semiconductor Business,
Samsung Electronics Co., LTD, 3 Laurence Berkeley National Laboratory
E-mail:takeo@lasti.u-hyogo.ac.jp
An EUV resist with high sensitivity and low lineedge roughness (LER) is required. LER of a resist is
strongly affected by an aberration and a flare of animaging optics. The flare of less than 10% is requiredfor LER evaluation in an exposure tool. Thus, sincean EUV interference lithography has no aberrationand no flare, LER evaluation is necessity to utilize
EUV interference lithographic exposure tool.[1,2]
We propose a dual grating interferometric (DGI)
lithography which can be operate in the usage of an
incoherent EUV light source. Thus, the DGI
exposure method can combine with a stand alone
EUV source, such as laser produced plasma anddischarge produced plasma. Therefore, this exposuresystem becomes a compact one for the evaluation ofresolution and LER in a EUV resist. Figure 1 shows
the configuration of a DGI exposure setup which canuse incoherent EUV light source. In thisinterferometric optical system, two transparent-type
diffraction gratings are employed. An cherent light is
produced by 1st-grating from an incoherent lightsource. Then, an interference fringe patterns on awafer are made by 2nd-grating. A replicated pitch
width of a resist pattern is a half-pitch width of 2ndtransparent-type diffraction grating pattern. The
calculated intensity distributions on a wafer obtainedby a computer simulation (a) for an incident coherent
light and (b) for an incident incoherent light are
shown in Fig. 2. It indicates that DGI exposure
method works well even if the usage of incoherent

light instead of coherent light.
This diffraction grating using for DGI system
was fabricated through by an electron beam writing
and dry etching process. In our setup, bending
magnet of SR storage ring is employed as a lightsource, and light from a bending magnet ismonochromated to the EUV wavelength region. The
photograph of the exposure tool using DGI system isshown in Fig. 3. The exposure tool consists of a mainchamber which includes wafer stage and diffraction
gratings. And load lock chamber is attached to the
exposure chamber to exchange a wafer. It is believedthat the developed EUV interference lithographic
system is a beneficial tool to develop EUV resist
which satisfies the specification of 32 nm and below.

References[1] H. H. Solak ; J. Phys. D: Appl. Phys. 39, 171(2006).
[2] A. M. Goethals, R. Jonckheere, G. F. Lorusso, J.
Hermans, F. Van Roey, A. Myers, A. Niroomand, I.
Kim, F. Iwamoto, N. Stepanenko, and K. Ronse, J.
Photopolym. Sci. Technol. 20, 383 (2007).

+1st order

0th order

EUV light±1st order

0th order

1st-grating

2nd-grating-1st orderFig.1. Dual grating interferometric system.

(a)Coherent Monochromatic Beam(b)

Incoherent Δλ= 8nm (11 nm~ 19 nm)

Fig. 2. The calculated intensity distributions on a wafer(a) for an incident coherent light, and (b) for an incident incoherent light.

Exposure chamber
Load lock chamber

SR

Fig. 3. The DGI exposure toolPattern Replication in EUV Interference Lithography
Shota Suzuki, Yasuyuki Fukushima, Ryuji Ohnishi,
Takeo Watanabe, and Hiroo Kinoshita
LASTI/UH
EUV interference lithography (EUVIL) beamline which employed a single grating was constructedat the BL3 beamline in NewSUBARU synchrotron radiation facility. Using this system, 400-nm L&S
resist pattern by single grating interferometric lithography system which employed a bending magnet
as a light source was replicated on a wafer.
In the otherwise design of EUVIL gratings, a dual grating interferometric system which is useful fora bending magnet as a light source was designed and constructed at BL3 beamline. Dual gratinginterferometric lithography has a capability for the replication of 28 nm line and space pattern on abasis of the interference-fringes calculation in the condition of partial coherence light source such as abending magnet. In dual grating interference optical system, two transparent-type gratings were
employed.
Keyword: EUV resist, chemically amplified resist, interference lithography

1. Introduction
Extreme ultraviolet (EUV) lithography1) is themost promising technology for 32 nm node, and it isrequired for the high volume manufacturinglithographic technology around 2011. Resist
materials and process technologies are one of thethree top issues.2) High sensitive and low line edge
roughness (LER) have to be achieved
simultaneously. In a stand view of resist material
development, the exposure characteristics of resist
material itself should be studied to design andsynthesis of EUV resist which can satisfy the EUV
resist specification. From this point of view, since
LER is affected by aberration and flare of theimaging optics, aberration and flare of the exposure
tool for the EUV resist evaluation have to avoid. The
flare of less than 10% is required for LER evaluation
for an exposure tool for 32 nm node beyond3). On
the other hand, in the interference lithography (IL),since IL does not require complicated and expensive
high numerical aperture imaging optics, IL has noaberration and no flare for the imaging optics.
EUV light from an undulator as a light sourceat synchrotron radiation facilities has long beenrecognized as a possible source for interference
lithography in this regime4). A periodic pattern canbe replicated on a wafer by IL using a coherent lightsource such as an undulator. 5, 8) Lloyd’s mirror
interferometer systems 5, 6) and single gratinginterference (SGI) system7, 8) are proposed. The
Lloyd’s mirror interferometer (LMI) system is basedon a single mirror. Replicated resist resolution of
LMI is limited by temporal coherence (lc ≈ λ2 / Δλ,where λ is an exposure wavelength).9) On the other
hand, replicated resolution of SGI is limited strongly
by spatial coherence and SGI had been usually usedwith a coherent light source such as laser and an
undulator. In synchrotron radiation, a bending
magnet is more compact, more simple and cheaper
than an undulator. Thus, in this paper, we would liketo discuss an EUV interference lithography using asingle grating interference (SGI) system and a dual
grating interference (DGI) system for the usage of abending magnet as a source.
2. Single Grating System
Figure 1 shows a configuration of a final structurea fabricated transparent grating with two windows.
Figure 2(a) shows seven transparent gratings with
two windows which was fabricated on a 4-inches
wafer. And Figure 2(b) shows a photograph of 800nm-L&S Si3N4 grating pattern observed by an
optical microscope.
In the fabrication process of a transparent two
window grating, 1) a 4-inches silicon wafer which
had been coated with Si3N4 layers on the both sides
of a wafer in 300-nm thickness was prepared. 2)tantalum layer was sputtered on a Si3N4 layer. 3)
ZEP520 resist was coated with 650-nm thickness. 4)
Resist pattern was replicated by electron beamlithography. 5) The resist pattern was transferred tothe tantalum and Si3N4 layer by a dry-etching using
CF3 gas. 6) Resist was removed by dry etchingprocess using O2 gas. 7) Backside of Si3N4 of ademanded aperture was removed by a CF3-dryetching process using glass mask. 8) Aperture area
on silicon substrate was removed by a wet etchingprocess using KOHaq. During this process, Si3N4
layer acts as an etching mask. Then the transparent

Ta
Si3N4
Si wafer
Si3N4
Fig.1 Configuration of a final structure afabricated transparent grating with two windows.

Two Windows
EUV+1st order
0th order±1st order
0th order-1st orderL(a)gratingwafer

Fig.3 Principle of SGI system.

(b)
Fig.2 (a) Photograph of transparency grating and(b) photograph of 800-nm-L&S Si3N4 grating
pattern.
grating which can be used in interference
lithography was fabricated.
Fig.3 shows the principle of SGI system. 0th
order, 1st order, and -1st order are produced by atransparent grating. As shown in Fig. 3, if two
grating is used, 1st order ray produce from one
window grating interfere in -1st order ray produced
from another window of a grating, and aninterference fringes is created at the suitable
position. Then if the resist inserted at the suitable
position, periodic pattern of a resist will replicatedon a basis of an interference fringes. In principles,
capable-replicated-pattern size is limited to a half
size of the wavelength.
SR light which is produced from the bending
magnet of the electron beam storage ring is led to theglancing mirrors M1 and M2. After these mirrors,
the beam size and divergence become to be 20 mm
in diameter and divergence of ±0.75 mradrespectively. Then the SR light is led through the 4
jaw slits, shutter, a 0.15-µm-thick Zr filter and areflected by Mo/Si multilayer mirror M4 tomonochrome to the EUV wavelength. The centroid
wavelength of the reflectivity spectrum is 13.5 nm
and full width at half maximum (FWHM) is 0.7 nm.
Finally, EUV light led to SGI system. Single grating
exposure chamber maintains typically the vacuum
pressure in the order of 10-6 Pa using a turbo
molecular pump and scroll dry pump. Loadlock
system for exchanging wafer sample was attached tothe exposure chamber to change a 4-inches wafer.
The spatial coherent length, Lc, is related to its angle
distribution, σ, by the relation of Lc = λ / σ.9) Since
the light angle distribution on a single grating is 0.35
mrad, calculated coherent length is 38.6 µm. The
distance L between the two-window grating has tobe smaller than the spatial coherent length.
To replicate resist pattern caused by aninterference fringes formulated from a single grating,distance between a single grating and a wafer and tilt
position of a grating tilt have to be aligned. In order
to control the gap between grating and wafer alonglight axis, we used Z-motion stage which can be
moved by a pulse motor in vacuum pressure order of
10-6 Pa, and the stage moving resolution is 1.5 µm.
Furthermore, we installed the α and β axis stages
which can control the grating tilt position around byhorizontal and vertical directions.
Figure 4 shows a photograph of a replicated
ZEP520A resist pattern of 400-nm line and space (L/0th order±1st order

0th order

Fig.4 Replicated ZEP520A resist pattern of 400nm line and space (L/S) pattern observed by
optical microscope.

0th order±1st order

0th order+1st order

Wafer

EUV

0th order±1st order
0th order
1st grating

2nd grating-1st orderFig.6 Setup of dual grating system.

Fig.5 Replicated ZEP520A resist pattern of 400nm line and space (L/S) pattern observed by
optical microscope.
S) pattern using a 1600-nm-pitch single grating
which was observed by a scanning electron
microscope (SEM). Exposure time was around 10 swith a 0.2-um-thick Zr filter. As a result, using abending magnet as a light source, we obtainedinterference replicated pattern. However, the patterncontrast is not perfect because of low temporal
coherence of the bending magnet.
3. Dual Grating System
As a result of calculated interference fringes of
the intensity distribution on a wafer in comparison
with a coherent light and a partial coherent light,
using 200-nm L&S grating, 100-nm L&S pattern ona wafer can be replicated easily from coherent light.
However, it is difficult to replicate 100-nm L&S
pattern using single grating system with partial
coherent light. In this calculation, it is assumed thatbeam size of 20 mm in diameter and the divergenceof ±0.75 mrad for a partial coherent light in thecondition of a BL3 beamline after M1 and M2
mirrors.
To improve the resolution, it is introduced dual
grating system which can allow pattern replication of
28-nm width. The setup of dual grating system isshown in Fig 5. 1st grating has one grating window,
and 2nd grating has two grating windows to transmit
the incident EUV light. By 1st grating, an incident
light is diffracted into -1st and +1st order rays. Thenby two grating windows of 2nd grating, -1st and +1storder rays produced from 1st grating are diffracted
into -1st order ray and +1st order ray. Finally each -1storder ray and +1st diffracted from two grating
windows of 2nd grating interfere each other toproduce interference fringes on a suitable position ofa wafer. In dual grating system, using 1st grating theincident light of 2nd grating is reproduced to satisfy
special coherency.
If the incident light is a parallel ray, pattern size
replicated on a wafer can be calculated by thefollowing equation, where d1 and d2 are the pitchesof 1st grating and 2nd grating, respectively.

1) For example, if 400 nm pitch of 1st grating and
100 nm pitch of 2nd grating are used, it can be
replicated 33-nm L&S pattern on a wafer. 2) For
example, if 800 nm pitch of 1st grating and 100 nm
pitch of 2nd grating are used, it can be replicated 28
nm L&S pattern on a wafer. 3) For example, if 1000
nm pitch of 1st grating and 80 nm pitch of 2nd grating
are used, it can be replicated 22 nm L&S pattern on awafer.
Figure 7 shows the calculated interference
fringes and intensity distribution on a wafer. In thiscalculation, 800-nm pitch grating is used as a 1st
grating, and 100-nm pitch grating was used as 2nd
grating. The distance between 1st and 2nd grating is
109 mm, and distance between 2nd grating and awafer is 43 mm. Furthermore, the partial coherence
condition was used is same to that used in single
grating. The results show that good performance inboth of using coherent light source and partial
coherent light source. Therefore, 28-nm L&S pattern
can be replicated on a wafer using BL3 beamline.
SR light which is produced from the bending
magnet of the electron beam storage ring is led to theglancing mirrors M1 and M2. Then the SR light is
led through the 4 jaw slits and shutter. Finally the
EUV light leads to the dual grating system. Dualgrating exposure chamber maintain typically thevacuum pressure in the order of 10-6 Pa using a turbo
molecular pump and scroll dry pump. Loadlock
system was attached to the exposure chamber for
exchanging a 4-inches wafer sample. In order tocontrol the gap between dual grating and wafer alonglight axis, we used Z-motion stage which can be
moved by a pulse motor in a high vacuum pressure,and the stage moving resolution is 1.5 µm.

Spacer

1st Slit

2nd Slit
Opticalaxis(a)

2nd Grating
100 nm pitch

1st Grating
400 nm pitch

Fig.8 Three-demensional-setup view of dual
grating.

(b)

Fig.7 Calculated interference fringes andintensity distribution on a wafer in the DGIsystem, (a) coherent light and (b) partial
coherent light.
Furthermore, we installed the α and β axis stages
which can control the dual grating tilt position
around by horizontal and vertical directions. The
dual grating
Figure 7 shows 3-demensional-setup view of
dual grating system. Two slits and one spacer areused to align the dual grating system. Short distance
between 1st and 2nd grating is achieved to increase
the tolerance of the alignment. The thickness of two
slits and a spacer are 200 µm and 4 mm,
respectively. The thickness of the silicon substrate of
1st and 2nd grating are 500 µm, respectively. Surfaceof 1st grating sits right direction and surface of 2nd
grating sits left side on a paper sheet to maintain the
distance of 4 mm between the surfaces of 1st and 2nd
grating. Furthermore, distance between the surfaceof 2nd grating and a wafer is maintained to be 1.8mm.
Figure 9 shows a ZEP520A resist pattern on 4inches wafer. Center exposure area is an interference
region of +1 order and -1 order from two grating
window area from 2nd grating in dual grating system.
The effectiveness of using dual grating system
combined with a bending magnet as a source isconfirmed.

constructed to the BL3 beamline at NewSUBARU.
Using SGI lithography combined with a bending
magnet as a light source, 400 nm L&S pattern isreplicated. In the calculation, partial coherent light is
not suitable for SGI lithography, and DGI system
can be used for the partial coherent light source. As aresult, 28-nm L&S pattern can be replicated using
dual grating system combined with the partial
coherent light source as a bending magnet bycomputer simulation.
Furthermore, the DGI exposure method can be
combined with a stand alone EUV source, such as
laser produced plasma and discharge produced
plasma. Therefore, this exposure system will become
a compact one for the evaluation of resolution and
LER in a EUV resist.
References
1. H. Kinoshita, K. Kurihara, Y. Ishii and Y. Torii: J.
Vac. Sci. Technol. B 7 (1989) 1648.
±1st order
0th order

0th order

4. Conclusion
Transparency grating was succeeded to fabricate.
Using the transparency grating, SGI lithographysystem and DGI lithography system were

Fig. 9 Replicated ZEP520A resist pattern.

2. Three top issues in EUVL, EUVL international
symposium 2007.
3. Roel Gronheid, Alan M. Myers, Frieda Van Roey,
H.H.Solak, Yasin Ekinci, Tom Vandeweyer,
Anne-Marie Goethals: presented at 2RE05,
EUVL International Symposium 2006,
Bercelona, Spain.
4. A. Yen, M.L. Schattenburg, H.I. Smith: Appl.
Optics 31 (1992) 2972.
5. R. Tatchyn, E. Kallne, A. Toor, T. Cremer and P.
Csonka: Rev. Sci. Instrum. 60 (1989) 1579.
6. H. H. Solak, D. He, W. Li, F. Cerrina, B. H. Sohn,
X. M. Yang and P. F. Nealey: Appl. Phys. Lett. 75(1999) 2328.
7. M. Wei , D. T. Attwood and T. K. Gustafson: J.
Vac. Sci. Technol. B12 (1994) 3648.
8. H. H. Solak, C. David, J. Gobrecht , V. Golovkina,
F. Cerrina , S. O. Kim and P. F. Nealey:
Microelectron. Eng. 56 (2003) 67.
9 Pedrotti, Frank L.: Introduction to optics.
(Prentice-Hall, New Jersey, 1987) p.317.1.
T.Omote, “Polyimides”, M.Ghosh, and
K.L.Miital, Eds., Dekker, New York, 1996,
p.121.

Optimization of photo acid generator in the PAG-bonded
resistYasuyuki Fukushima1, Ryuji Ohnishi1, Takeo Watanabe1, Hideaki Shiotani1,
Shouta Suzuki1, Masamichi Hayakawa2, Yusuke Endo2, Tomotaka Yamanaka2,
Shinichi Yusa1, and Hiroo Kinoshita1
1 LASTI/UH, 2 Toyo Gosei Kogyo Co., Ltd.

E-mail: takeo@lasti.u-hyogo.ac.jp

1. Introduction
Extreme ultraviolet lithography (EUVL) is themost promising technology for the fabrication of finepatterns of less than 32 nm node around 2010.
Second issue of EUVL technology is resist
development. The most significant issue is tosimultaneously achieve high sensitivity and low lineedge roughness (LER). For the method of reducing
LER, it has to be taken account of uniform photo acidgenerator (PAG) density in a resist film. Since in theconventional chemically amplified (CA) resist, PAG
and polymer mix in the solvent, PAG density in resist
becomes non-uniform. Consequently, PAG wassynthesized to the side chain of base resin to achieve
uniform PAG density. As shown in Fig. 1, PAG
density of a PAG-bonded resist seems to achieve
higher uniformity rather than that of PAG blended
resist. We developed and evaluated the PAG-bonded
resist to satisfy the EUV specifications.

exposure. Chemical structure of the PAG-bonded
resist and the PAG-blended resist are shown in Fig.2(a) and Fig. 2 (b), respectively. We evaluated various
PAG system for the improvement of the exposure
characteristics of the PAG-bonded resist. The
chemical structure of beneficial PAG is shown in Fig.
3.
The EUV sensitivity experiment was carried out
using resist evaluation system installed at the BL3
beamline of NewSUBARU synchrotron radiation(SR) facility. E0 sensitivity of the PAG-bonded resist
and the PAG-blended resist were 5.0 mJ/cm2 and 3.5
mJ/cm2, respectively. Figure 4 and 5 show thephotograph of SEM image of 75 nm lines and spaces(L/S) pattern of the PAG-bonded resist and the PAGblended resist replicated by 30 kV EB writing tool.
LER of the PAG-bonded resist and the PAG-blended
resist were 3.5 (3σ) nm and 7.8 nm (3σ), respectively.
Furthermore, 50 nm L/S pattern of the PAG-bonded
resist could be observed. However, resist B could not
resolve. Since using 30 kV EB writing tool,
resolution of 50 nm is limited, 50 kV EB writing tool
is used for the evaluation of the resolution. Figure 6
shows the photograph of SEM image of 55 nm linesand 25 nm spaces which is replicated by the 50 kV
EB writing tool.

(a)
resin

PAG

(b)
Fig. 1. (a) PAG blended resist and (b) PAG
bonded resist.

2. Experiment
To confirm the superiority of a PAG-bonded
resist, PAG blended resist which is consists of samebase resin materials for the PAG-bonded base resin
was used to compare LER under electron beam (EB)

3. Summary
We developed and evaluated the PAG bonded
resist that is a CA resist to reduce LER for EUVL.
Under EUV exposure, E0 sensitivity of the PAGbonded resist was 5 mJ/cm2. In order to clarify
resolution and LER, EB exposure was performed,
and LER of 3.5 nm (3σ) in 75 nm L/S was achieved
by PAG bonded resist. A LER of PAG bonded resist
is smaller than that of PAG blended resist. It can beconsidered that the PAG density of PAG bonded
resist has higher uniformity than that of PAG blended
resist. In addition, resolution of 25 nm was achievedby the 50 kV EB writing tool. It is confirmed that
PAG bonded resist have characteristics of highresolution and low LER. We will discuss of the
improvement of exposure characteristics using
beneficial PAG group in the PAG-bonded resist.

(a)Fig. 4. The photograph of SEM image of
nm L/S pattern of PAG bonded resist.

75(b)
R, R’: protection group
Fig. 2. Chemical structure of (a)PAG bonded
resist.

Fig. 5. The photograph of SEM image of 75 nm
L/S pattern of PAG blended resist.

R3, R4: H, CH3

R5, R6: H, CH3, t-Bu

Fig. 3. Chemical structure of PAG and (b) PAB
blended resist.

Fig.6. The photograph of SEM image of 55nm line
and 25 nm space pattern of PAG bonded resist.

Mitigation of Low LER with PAG Bonded Resist
for EUVL
Yasuyuki Fukushima, Takeo Watanabe, Ryuji Ohnishi, Hiroo Kinoshita, Hideaki
Shiotani, Shouta Suzuki, Masamichi Hayakawa*, Yusuke Endo*
Tomotaka Yamanaka* and Shinichi Yusa**
LASTI/UH, *Toyo Gosei Kogyo Co., Ltd.
**Graduate School of Engineering/ UH,
We developed and evaluated PAG bonded resist which is chemically amplified (CA) resist to
reduce line edge roughness (LER) in extreme ultraviolet lithography (EUVL). Under electron
beam (EB) exposure, it is compared that LER and resolution of photo acid generator (PAG)
bonded resist and PAG blended resist which using same PAG and base polymer. It was found that
LER and resolution of PAG bonded resist are better than that of PAG blended resist. LER of 3.5
nm in 75 nm L/S and resolution of 25 nm space were achieved. Under EUV exposure, sensitivityof 5.0 mJ/cm2 is achieved.
Keywords: EUV resist, EB resist, line edge roughness, sensitivity

1. Introduction
Extreme ultraviolet lithography (EUVL)1) is themost promising technology for the fabrication of finepatterns of less than 32 nm node. EUVL is planned
to transfer to the production line around 2010.
Second issue of EUVL technology is resist
development. EUV resist specification2) are 1) 18
nm resolution for a gate pattern, 2) 32 nm for dense
pattern, sensitivity of less 2 mJ/cm2, 3) line edge
roughness less than 1.2 nm (3σ), 4) outgassing lessthan 1×10-6 Pa. Since LER and sensitivity are intrade off, it is very difficult to achieve LER and highsensitivity simultaneously. Required LER value is assame as molecule size of base resin. Thus molecule
size control is required in the pattern width control.
To reduce LER in chemically amplified resist3-5),
following five items have to take account such as, 1)
controlling diffusion of acid, 2) low molecularweight 3) narrow dispersion molecular weight
polymer and 4) uniform photo acid generator (PAG)
density in resist film. Items 1) to 3) have been
carried out. However it did not work well or had aproblem for EUV resist.
Therefore, as a concrete method to achieve
uniform acid density, PAG is synthesized to side
chain of base resin. Since in the conventional
chemically amplified (CA) resist, PAG and polymer
mix in the solvent, the density of PAG in resist
become heterogeneous6). As shown in Fig. 1, PAG
bonded resist seems to achieve higher uniformity
rather than that of PAG blended resist.
In the previous paper7), it is demonstrated that
PAG bonded resist has low LER and high sensitivity
under electron beam. Futhermore, PAG bonded resist
has high sensitivity under EUV exposure. However,
the resolution was limited to 100 nm. Therefore, inthis paper it is focused on to refine resolution of

PAG bonded resist under EB exposure with keeping
low LER and high sensitivity.
2. Experiment
2.1 Sample
For the method of increasing sensitivity,
protection group which has a chemical structure withhigh absorption in EUV light was designed. In
conventional protection group, de-protection
reaction of protection group is occurred by acid
which is generated during exposure from PAG.
Furthermore, in novel protection group, since photo
decomposition reaction is ocurred under EUV
exposure. Therefore, novel resist system seems tohave high sensitivity comparison to the conventional
resist system such as ESCAP type resist.

(a)

(b)

Fig.1. (a) PAG blended resist and (b) PAG
bonded resist.

(b)

(a)
R, R’: protection group

Fig. 2. Chemical structure of resists A and B.

R5, R6: H, CH3, t-Bu

R3, R4: H, CH3

Fig. 3. Chemical structure of PAG.

To confirm the superiority of PAG bonded resist,
PAG blended resist which is consists of same baseresin materials for PAG bonded base resin was used
to compare LER under EB exposure. Chemical
structure of PAG bonded resist and PAG blended
resist are shown in Fig.2 (a) and Fig. 2 (b),respectively. Copolymer of hydroxy styrene wasused as base resin, PAG which is shown in Fig. 3
w a s u s e d a s PA G , p r o p y l e n e g l y c o lmonomethylether acetate (PGMEA) was used assolvent. Molecular weight of synthesized resist was
16400 and molecular weight distribution was 1.09.
The details of composition of resist sample areshown in Table 1.
Table 1. The details of composition of resist sample.

SampleProtection
group

PAG
AmountType

Resist A 32.3 mol% 3.7 wt%

Bond

Resist B 32.1 mol% 3.7 wt%

Blend

2.2 Evaluation method
The sensitivity and outgassing experiment werecarried out using resist evaluation system8) installedat the BL3 beamline of NewSUBARU synchrotron
radiation (SR) facility.
In the resist evaluation syste, it is simulating a
six-mirror imaging optics for practical used for
EUVL. SR light was mono-chromated to 13.5 nm
wavelength by seven times reflection of concave
mirror and two plane mirrors of Mo/Si mutilayer.
Intensity of light was measured an electron current
value of a photoelectron when EUV light irradiates
to photoelectron plate. And it convert to the photon
number of EUV light. Then, intensity of light wascalculated from the photon number converted.
Furthermore, resist pattern was performed by EB
writing system to evaluated resolution and LER.
The acceleration voltages of EB writing system were
30 or 50 kV. The resist pattern image was obtainedusing scanning electron microscope (SEM) and LER
was measured with a graphic processing computer
software SuMMIT9).
2.3 Process condition
The resist film was spin-coated on Si wafer andprebake was carried out on a hot plate at thetemperature of 120 ℃ for 90 seconds to evaporate
the solvent. The resist film thickness was controlled
at 100 nm and measured by a multi-wavelengthinterference thickness measurement tool Nanospec
model 6100A manufactured by NANOmetrics Co.
Ltd. PEB was carried out on a hot plate at thetemperature of 90 ℃ for 60 seconds after exposure.
Aqueous 2.38 wt% of tetramethylammoniumhydroxide (TMAH) was used as a developer at thetemperature of 23 ℃ for 30 seconds and rinsed with
de-ionized water.
3. Results and discussion
3.1. Sensitivity and outgassing measurement
Figure 4 shows sensitivity curve of resist
samples under EUV exposure and Table 2 shows E0
sensitivity of resist A and resist B.
E0 sensitivity of resist A and B are 5.0 mJ/cm2
and 3.5 mJ/cm2, respectively.
It shows thatsensitivity of PAG blended resist is higher than thatof PAG bonded resist. Since it is thought thatpolymer agglutinates to wrap up PAG, it is consider
that acid is hard to diffuse during PEB process.
The outgassing is measured using high sensitive
quadrupole mass spectrometer. Total outgassing
displacement between after exposure and before
exposure was measured. The measured mass range
was 1 amu to 500 amu.
Table 3 shows total
outgassing pressure of resist A and resist B.
Table 2. E0 sensitivity of resist A and B

SampleResist A
Resist B

E0 sensitivity
5.0 mJ/cm2
3.5 mJ/cm2

Normalized Remain thickness

Figure 6 shows the photograph of SEM image ofresist B. 75 nm line and space pattern was observed.
A sensitivity and LER are 7.5 µC/cm2 and 7.8 nm(3σ), respectively.

Dose (mJ/cm2)
Fig. 4. Sensitivity curve of resist samples.
Fig. 6. The photograph of SEM image of resist B
Table 3. Total outgas pressure of resist sample

SampleTotal outgas pressure

Resist A

3.46×10-6 Pa

Resist B

4.33×10-6 Pa

The total ougassing pressure of resist A and B
are 3.46×10-6 Pa and 4.33×10-6 Pa, respectively.
Furthermore, a lot of molecular weight own to aprotection group was detected. As a result, it isthought that protection group is decomposed under
EUV exposure. Total outgassing of resist A have not
big difference between total outgassing of resist B
because of similar base resin chemical structure.

It was confirmed that LER of PAG bonded resist
was smaller than that of PAG blended resist. As aresult, it is sure that uniformity of PAG in PAG
bonded base resin has higher uniformity than that of
PAG blended resist. Furthermore, 50 nm L/S patternof resist A could be observed. However, resist B
could not resovle.
Figure 7, 8, 9 show the photograph of SEM
image of 90 nm line and 60 nm space, 62.5 nm line
and 37.5 nm space, and 55 nm line and 25 nm spaceof resist A, respectively. The acceleration voltage ofEB writing system was carried out at 50 kV using
ELIONIX 7500. It is conformed that resist A has acapability to resolve 25 nm.

3.2. Resolution and LER evaluation
Figure 5 shows the photograph of SEM image ofresist A replicated by EB writing system ELIONIX
3700 The acceleration voltage of EB writing system
was 30 kV. 75 nm line and space pattern wasobserved. Sensitivity and LER are 16.0 µC/cm2 and3.5 nm (3σ), respectively.

Fig. 7. The photograph of SEM image of 90 nm line
and 60 nm space of resist A
4. Conclusion

Fig.5. The photograph of SEM image of resist A

We developed and evaluated PAG bonded resist
which is chemically amplified (CA) resist to reduceline edge roughness (LER) for extreme ultraviolet
lithography (EUVL).

Fig. 8. The photograph of SEM image of
62.5 nm line and 37.5 nm space of resist A.

Fig. 9. The photograph of SEM image of 55
nm line and 25 nm space of resist A.
Under electron beam (EB) exposure, it iscompared that LER and resolution of photo acidgenerator (PAG) bonded resist and PAG blended
resist which using same PAG and base polymer. E0

sensitivity of resist A was 5.0 mJ/cm2 under EUV
exposure.
Total outgas pressure of resist A was 3.46×10-6
Pa, and a lot of molecular weight of protection group
was detected.
In order to clarify resolution and LER, EB
exposure was performed, and LER of 3.5 nm (3σ) in
75 nm L/S was achieved by PAG bonded resist. A
LER of PAG bonded resist is smaller than that of
PAG blended resist. It can be considered that the
PAG density of PAG bonded resist has higher
uniformity than that of PAG blended resist.
In addition, resolution of 55 nm line and 25 nm
space was achieved when the acceleration voltage ofEB writing system was 50 kV. It is confirmed that
PAG bonded resist have characteristics of highresolution and low LER.
In the next stage, LER and resolution of PAG
bonded resist will be evaluated using EUVinterference lithography.
References
1. H. Kinoshita, K. Kurihara, Y. Ishii and Y. Torii:
J. Vac. Sci. Technol. B7(1989) 1648.
2. W. Yueh, H. Cao, M. Chandhok, S. Lee, M.
Shumway and J. Bokor: Proc. SPIE. 5376
(2004).
3. H . I t o : J o u r n a l o f R e s e a r c h , 1 9 9 7 research.ibm.com
4. H. Ito:J. Polym. Sci., PartA, Polm. Chem. 41,3863 (2003)
5. H. Ito: Proc. SPIE. 3678 (1999)
6. Proceeding of 15th lecture Meeting of photoreactions and electric materials, the society ofpolymer and science, pp.15-18, 2006.
7. T. Watanabe, Y. Fukushima, H. Shiotani,
M.Hayakawa, S. Ogi, Y. Endo, T. Yamamoto, S.
Yusa and H. Kinoshita: J.Photopolym. Sci.
Technol. 19 (2006) 521
8. T. Watanabe, H. Kinoshita, N. Sakaya, T. Shoki,
S. Y. Lee:Jpn. J. Apply. Phys. 44 (2005) 5556
9. Developed by Patrick Naulleau, informed at
URL: http://www.euvl.com/summitSR irradiation effect of high-hydrogenated DLC thin films
in the soft X-ray region
Kazuhiro Kanda1, Masahito Niibe1, Masahito Tagawa2, Kumiko Yokota2, Hiroki Akasaka3, Hidetoshi Saitoh3 andShinji Matsui1
1 Laboratory of Advanced Science and Technology for Industry, University of Hyogo
2 Graduate School of Engineering, Kobe University
3 Department of Materials Science and Technology, Nagaoka University of Technology
abstract
The effect of irradiation of synchrotron radiation to high-hydrogenated DLC thin films was investigated.
Etching of films, department of hydrogen from films and change of local structure were founded.

Introduction
General DLC films are ablated by the
exposure to the synchrotron radiation (SR) in the soft
x-ray region under O2 atmosphere, while they are notetched by the exposure to the SR in the soft x-ray
region in the vacuum. On the other hand, theirradiation of soft x-ray in the vacuum against highhydrogenated DLC (H-DLC) films bring about the
departure of hydrogen. In the present study, thevariation of local structure of high-hydrogenated
DLC thin films by the irradiation of soft X-ray in thevacuum was investigated.
Experimental
High-hydrogenated DLC thin films were
deposited by amplitude-modulated RF plasma-CVD.
The film thickness was 200 nm. The irradiation ofsoft X-ray against DLC films was carried out at BL-6
of NewSUBARU. The SR at the BL-6 sample stage
had a continuous spectrum from IR to soft X-ray,which was lower than 1 keV. The SR dose wasrepresented by the product of the ring current withthe exposure time. The irradiation of SR was
performed at room temperature and the increase of
substrate temperature was not found.
Results and discussion
Figure 1 depicts the SR dose dependences ofthe etching depth of high-hydrogenated DLC thinfilm by the SR irradiation. The depth of etching wasmeasured with DEKTAK(ULVAC; 6M). The etching
depth increased almost linearly with SR dose in the
SR dose range of 0-150 mA·h.
The change of density of DLC film by the soft
X ray irradiation was measured using the X-ray
reflectometer. Measured angle dependences of thereflectivity of H-DLC films as deposition and after
irradiation of 3600 mA·h were depicted in Fig. 2.
Critical angle and vibrational period were varied by
the SR irradiation. The film density was found toincrease from 1.45 g/cm3 to 1.80 g/cm3.

Fig. 1The SR dose dependences of theetching depth of high-hydrogenated DLC thinfilm by the SR irradiation.
Rutherford backscattering spectrometry (RBS)
and elastic recoil detection analysis (ERDA) are

As deposition

After irradiation

angle / degree
Fig. 2 XRR spectra of H-DLC films as
deposition and after irradiation of 3600 mA·h.

As deposition

Fig. 3The SR dose dependences of thehydrogen content of high-hydrogenated DLC
thin film and low-hydrogenated DLC thinfilm.
available for evaluating quantitative determination
for all elemental composition, specially hydrogen, of
thin films with high accuracy, being unnecessary forstandard samples. In this study, the hydrogen content
of DLC film has been determined by RBS andERDA techniques using a tandem Pelletron
accelerator, 5SDH-2 in the Kobe University.
As shown in Fig. 3, the hydrogen content in
the low-hydrogenated DLC film kept constant
independent on a soft X-ray exposure dose. On theother hand, that in the high-hydrogenated DLC film
decreases exponentially with a soft X-ray exposure
dose. Thus, the departure of the hydrogen wasobserved from high-hydrogenated DLC films, while
was not observed from the low-hydrogenated DLC
film by soft X-ray irradiation.
To examine a change of the local structure ofhigh-hydrogenated DLC film by the departure ofhydrogen, Near Edge X-ray Absorption Fine
Structure (NEXAFS) spectra were measured at
NewSUBARU BL-9. Photocurrent coming from asample was detected in the total electron yield. The
NEXAFS spectrum of carbon K edge absorption wasmeasured in the range of 275-320 eV with theresolving power of 0.5 eV FWHM. In the NEXAFS
spectrum of the high-hydrogenated DLC film before
the soft X-ray irradiation, structural peaks wereobserved in the 286-310 eV. This is interpreted by theconstruction of specific structures in the DLC film,
corresponding to a large amount of hydrogen atom.
These structural peaks disappear after the soft X-ray
irradiation and spectral profiles get close to those ofgeneral DLC films well. The intensity of 285.4 eV,corresponding to sp2 structure increased with theexposure doses of the soft X ray. Therefore, the sp2
structure in the DLC film increases by the departureof the hydrogen.

After irradiation

Fig. 4 C K-edge NEXAFS spectra of H-DLC
film as deposition (upper) and that after SR
irradiation of 3600 mA·h (lower)

Structural Changes in the DLC Films Fabricatedusing Ga Focused Ion Beam Assisted Deposition
by Heat Treatment
Kazuhiro Kanda1, Makoto Okada1, Yuji Kang1, Tsuneo Suzuki2, and Shinji Matsui1
1 LASTI, Graduate School of Science, University of Hyogo

2 Extreme Energy-Density Research Institute, Nagaoka University of Technology

abstract
The annealing effect on a diamond-like carbon (DLC) thin film fabricated by focused-ion-beam chemicalvapor deposition (FIB-CVD) was investigated. Elementary analysis, using Rutherford backscattering
spectrometry and elastic recoil detection analysis were performed on the FIB-CVD DLC thin film byannealing in the various annealing condition. It was found that the Ga in the middle layer in the FIB-CVD
DLC film promptly departed and that department of hydrogen was slower than that of Ga.

Introduction
Ga Focused-ion-beam chemical-vapor
deposition (FIB-CVD) method is developed as aneffective technique for producing of threedimensional nanostructures. In this method, scanningof focused Ga ion beam under the phenanthrene gas
atmosphere leads to deposition of carbon material atarbitrary nanoscale area. It was known that thefundamental structure of carbon material formed by
FIB–CVD consists of the DLC core, which contains
Ga as an ion source, and surface layer, which wascomposed of pure diamond-like carbon (DLC). In
addition, this residual Ga in the FIB-CVD DLC film
moved to the neighboring surface and departed fromthe film surface by the annealing, from the angledependent measurement of C K-edge NEXAFS
spectrum [1]. In our previous work, Ga content in the
FIB-CVD DLC thin film decreased from 3.6 % totrace mount by the annealing for 1 hour at 1023 K,
from Rutherford backscattering spectrometry (RBS)[2]. In the present study, we measured the RBS
spectrum and elastic recoil detection analysis(ERDA) spectrum by the variation of annealing
condition of FIB-CVD DLC film. As a result, thenovel information on departure process of Ga from
FIB-CVD DLC film was acquired.
Experimental
Ga FIB-CVD DLC films were formed on a Si
substrate surface using a commercially available
F I B - C V D s y s t e m ( S I I N a n o Te c h n o l o g y,
SMI2050MS) with a Ga+ ion beam operating at 30
keV. The area and thickness of the produced FIBCVD DLC films were 10×10 mm2 and ≈200 nm,
respectively. The samples were kept in the vacuum
annealing apparatus during 32 hour. The annealing
temperature was varied from 673 K to 973 K.
The atomic fraction of Ga in the sample wasdetermined by the measurement of RBS and ERDA.
RBS and ERDA with MeV-He+ irradiation were
performed using an electrostatic accelerator (Nisshin-

High Voltage, NT-1700HS) located at the Extreme
Energy Density Research Institute, Nagaoka
University of Technology.
Results and discussion
Figure 1 shows Ga profiles in the RBS spectra.
In the FIB-CVD DLC film as deposition, the profile
of Ga shows rectangular, which means that Ga
populated equally in the core of the FIB-CVD film,
which contains Ga. After annealing, the content of
Ga decreased and the profile of Ga was split to two
peaks. This profile indicates that the Ga in the middle
layer in the FIB-CVD DLC film was almost lost, and
the Ga in the vicinity of surface and interface
remained. It was known that the residual Ga moves
easily in the FIB-CVD DLC film and forms spheres
surrounded by graphite shell on the film surface byannealing treatment [3]. The moving velocities of Ga
in the vicinity of interface and surface wereconsidered to be smaller than that in the middle DLC
layer, because the diffusion coefficients in the Si
substrate and in the graphite shell were smaller thanthat in the amorphous carbon.
Fig. 2 shows the annealing time dependence ofGa and H contents of FIB-CVD DLC film. The Ga

Fig. 1 Ga profiles in the RBS spectra.

content in the as-deposited FIB-CVD DLC film, ≈5
at %, decreased with an increase in annealing time inexponential law, while H content almost not varied.
Fig. 3 was depicted the annealing timedependence of Ga and H contents. The Ga content
slightly decreased with an increase in annealing
temperature from room temperature to 673 K andconsiderably decreased with an increase from 673 to
773 K. On the other hand, the H content decreased
with an increase in annealing temperature from 673
to 973 K, but a certain mount of H (≈7 at %) was
observed in the FIB-CVD DLC film after 32 hannealing at 973 K. As a result, the residue Ga in the

FIB-CVD DLC film almost departed from the film at
673 K, which was a lower temperature than thedesorption of H in the DLC film.

Fig. 2 Annealing time dependence ofelementary composition of FIB-CVD DLC
film at the annealing temperature of 673 K.

Fig. 3 Annealing temperature dependence ofelementary composition of FIB-CVD DLC
film after 32 h annealing.

References[1] A. Saikubo, K. Kanda, Y. Kato, J. Igaki, R.
Kometani, et. al., Jpn. J. Appl. Phys. 46 (2007) 7512.
[2] K. Kanda, J. Igaki, A. Saikubo, R. Kometani, T.
Suzuki, et. al., Jpn. J. Appl. Phys. 47 (2008) 7464.
[3] R. Kometani, S. Ishihara, K. Kanda, Y.
Haruyama, et. al., Jpn. J. Appl. Phys. 47 (2008)
5032-5035.

Atomic Movement in a-Si Filmby Soft X-ray irradiation
Akira Heya, Yasuyuki Takanashi, Kazuhiro Kanda and Naoto Matsuo
University of Hyogo
Abstract
Atomic movement in a-Si film by soft X-ray irradiation was investigated for low-temperature
crystallization. a-Si films were irradiated at storage electron energy of 1GeV, photon energy of
115eV and irradiation quantity of 50mA*hours and storage-ring current were varied from 50 to
175mA. a-Si film was crystallized above storage-ring current of 175mA. It is considered thatcrystallization temperature at this condition was low compared with conventional thermal
crystallization. It is considered that the soft X-ray irradiation enhanced atomic movement in a-Si
film.

Introduction
Flexible organic light emitting diode(OLED) display is one of the most expecteddisplays for next generation because of its
light weight and flexibility. Polycrystalline
silicon (poly-Si) films prepared below 200 °C is
necessary as material of thin film transistor (TFT)
in flexible displays. The poly-Si films preparedby crystallization of amorphous silicon (a-Si)
using excimer laser annealing (ELA) have been
investigated widely. However, it is difficult torealize low-temperature process for ELA method.
We have tried to crystallize a-Si film using
soft X-ray irradiation [1-3]. It is confirmed thata-Si film crystallized at storage-ring current of
220mA, storage electron energy of 1GeV, photon
energy of 115eV and irradiation quantity of
1000mA*hours. However, in this irradiation
condition, it is afraid that sample temperature washigh.
In this study, the sample temperature wasmeasured by an infrared thermometer and athermocouple attached on sample. In addition, aSi film was irradiated at various storage-ringcurrents (50 to 175mA).

that difference in temperature was large in spiteof small sample because soft X-ray beam size issmall and thermal conductivity of glass substrateis low.
The maximum temperature wascomparable with crystallization temperature forconventional furnace annealing. Therefore it isnecessary to decrease sample temperature forlow-temperature crystallization.
2) a-Si films irradiated at various storage-ringcurrent
a-Si/SiO2/glass substrate was irradiated atstorage electron energy of 1GeV, photon energyof 115eV and irradiation quantity of 50mA*hours.
Storage-ring current were varied from 50 to
175mA for decrease in sample temperature. The
irradiation time for the storage-ring current of 50,
75, 100, 125, 150 and 175mA were 60, 40, 30, 24,
20 and 16min, respectively.
The Raman spectra of Si film irradiated atvarious storage-ring current are shown in Fig. 2.
The peak due to amorphous phase (480cm-1) was
observed at a-Si films irradiated below 150mA.
On the other hand, a-Si film was crystallized at
5
4
3
650

2

Y position (mm)Experiments and Results
1) Sample temperature during soft X-ray
irradiation
a-Si films with 50nm thickness were
deposited by plasma enhanced chemical vapor
deposition method on SiO2/glass substrates. The
temperature of a-Si/SiO2/glass substrate wasmeasured by a thermocouple (K type) attached on
sample (10×10 mm2 in size ). The temperature
distribution was obtained by moving of sample
position. The measurement conditions were atstorage electron energy of 1GeV, storage ring
current of 220mA and photon energy of 115eV.
The temperature distribution is shown in Fig.
1. The maximum and minimum temperature
was 680℃ and 340℃, respectively. It is shown

450

1

700

600 550

650

0

600
550

-1

500

500

-2

450
400

-3

350
-4

300

-5
-5

-4

-3

-2

-1

0

1

2

3

4

5

X position (mm)Fig. 1. Sample temperature distribution duringsoft X-ray irradiation at storage electronenergy of 1GeV, storage ring current of
220mA and photon energy of 115eV.

Crystal phase

Si film

Raman intensity (arb. units.)

Amorphous phase
Storage-ringcurrent
175mA

150mA

125mA
100mA

75mA
50mA

400 420 440 460 480 500 520 540 560 580 600

Raman shift (cm-1)
Fig. 2. Raman spectra of Si film irradiated atvarious storage-ring current. a-Si films were
irradiated at storage electron energy of 1GeV,
photon energy of 115eV and irradiation
quantity of 50mA*hours.
ring current of 175mA. The sample temperature
estimated by thermo tape at 100mA were 300℃.
The collect sample temperature at storage-ringcurrent of 175mA is not clear. However, thistemperature can be estimated to 500 ℃ by
assuming that as the sample temperature
increased linearly with increasing the storage-ringcurrent. It is found that a-Si was crystallized at
low temperature compared with a conventional
furnace annealing.
The crystallization mechanism for theconventional thermal annealing and the thermal
annealing with soft X-ray irradiation are shown in
Fig. 3. Si atoms can be moved by photon
excitation during soft X-ray irradiation and Si
atoms are ordered locally. We call this region thequasi-nucleus. It is considered that the radius of
the quasi-nucleus was small compared with thecritical radius for crystallization. The quasinucleus grew to crystal grain with critical radius
for crystallization despite low-temperatureannealing. In this case, crystal grains can begrown without nucleation energy in the
crystallization process because the quasi-nucleus
was already formed. Therefore, the criticaltemperature for crystallization was decreased bysoft X-ray irradiation because of the generation ofa quasi-nucleus. It is found that soft X-ray
irradiation can be expected for low-temperature
crystallization of a-Si film.

Fig.3. Crystallization mechanism during soft
X-ray irradiation. Quasi-nuclei were formedby soft X-ray irradiation. The criticaltemperature for crystallization was decreased
by soft X-ray irradiation.
References[1] N. Matsuo, T. Mochizuki, S. Miyamoto, K.
Kanda, N. Tanaka, and N. Kawamoto: Dig.
AM-LCD, 2005, p.293.
[2] N. Matsuo, K. Uejyukkoku, A. Heya, S.
Amano, Y. Takanashi, S. Miyamoto, and T.
Mochizuki: Jpn. J. Appl. Phys. 46 (2007) 1061.
[3] A. Heya, Y. Takanashi, S. Amano, N. Matsuo,
S. Miyamoto, and T. Mochizuki: Jpn. J. Appl.
Phys. 48 (2009) 050208.

Opening of Material Analysis Beamline
at BL-5 for Industrial Enterprises
T. Hasegawa1, M. Uemura1, M. Motoyama2, and K. Kanda2
1 Synchrotron Analysis L.L.C., Hyogo-ku, Kobe, Hyogo 652-0863 Japan
2 University of Hyogo, Kamigori, Ako, Hyogo 678-1205 Japan
Abstract
An analysis beamline with high energy-resolution begins to supply at BL-5 for the industrial
enterprises’ use. BL-5 consists of two branch lines for the use in the high-energy region and lowenergy region, respectively. These two branch lines can be employed simultaneously. The wholeuseful energy range of the BL-5 is the region from 50 to 4000 eV and X-ray absorption spectrumof every atom from Li to Sn can be measured using this line. BL-5 will be managed andmaintained by the Synchrotron Analysis L.L.C. (SALLC), which is composed by the industrial
companies.
Introduction
Attendant upon the quick development of nanotechnology industry, demand for material analysis in
the soft X-ray region has increased rapidly. For
instance, the analysis of the soft X-ray region is an
important major technology in the research anddevelopment and the manufacturing enterprise of ahigh-technology material and the device. X-ray
absorption fine structure (XAFS) technique in thesoft X-ray region has attracted much attention fromanalysis industry as a powerful tool to investigate theelectronic states and geometric structures of industrial
materials. In addition, photoemission spectroscopy(PES) technique is also an effective analysis method
to research the electronic structure of material
surfaces in the ultra-soft x-ray region. Hyogo
prefecture constructed a new beamline at BL-5 of
NewSUBARU in reply to the demand of industrial
societies. In the construction of this beamline,
cooperation of University of Hyogo with private
enterprises is expected to prosper the co-researchwith University of Hyogo and advance of the analysis
technique of analysis industry in Hyogo prefecture.
Layout of BL-5
The light source of BL-5 is the bending magnet,
which can provide the photon in the region up to4000 eV. BL-5 consists of two branch lines for theuse in the wide range from 50 eV to 4000 eV. BL-5A,
which is mounted with a double crystal
monochromator, can be used in the energy range of
1300-4000 eV. On the other hand, BL-5B is mountedwith a varied line spacing grating (VLSPG)
monochromator, which is designed to cover theenergy range 50-1300 eV with three gratings. The
incident beam from the bending magnet is provided
for two branch lines through the different windows ofmask. These two branch lines can be employedsimultaneously.
Specifications of BL-5A
An optical arrangement of the BL-5A is shown in
Fig. 1. InSb crystals and Si crystals are prepared for a

double crystal monochromator. Toroidal mirrors areused as a pre-mirror and a focusing mirror of BL-5A,
for the purpose to introduce a high-photon flux to theend station. The XAFS in the total electron yield(TEY) mode and fluorescence XAFS measurement
using SSD (SII Vortex) can be performed. The
fluorescence XAFS spectra can be measured samples
at the under an atmospheric pressure by the
replacement of an end station to He using Be
window.

Radiation
ShieldBL-5A

ToroidalToroidal

M0

M1

S0

Bending
MagnetSample

DXM

0

3.65

11.0 11.65

14.65

16.65 [m]Fig.1 Optical layout of BL-5A

Specifications of BL-5B
The constant-deviation monochromator consistingof a demagnifying spherical mirror and VLSPG,
which can provide to high resolution, simple
wavelength scanning with fixed slits, was mounted
on BL-5B. An optical arrangement of the BL-5B isshown in Fig. 2.
The optical system consists of a first mirror (M0), a
second mirror (M1), an entrance slit (S1), a
pre-mirror (M2), and three kinds of plane grating (G),an exit slit (S2) and a focusing mirror (Mf). The
including angle of the monochromator is 175°. Twomeasurement chambers are prepared at the end
station of BL-5B. The XAFS spectra in the total
electron yield mode and fluorescence XAFS spectrausing SDD (EDAX) can be measurement in the highvacuum chamber. In addition, the photoelectronspectra using spherical
Radiation electron analyzer (VG
BL-5B
ShieldScienta,
Cylindrical

M0
S0

Plane VLS
grating

Cylindrical Entrance slit

M1

Bending
MagnetS1

S2

Toroidal

Mf

SH
Spherical
4.0

10.5

14.0

4WS

Hartman

M2

0

Exit slit

21.0 21.5

28.0

Sample4-jaw
aperture

30.0

32.0 [m]Fig.2 Optical layout of BL-5B
spectra using spherical electron analyzer (VG Scienta,
R3000) can be measured in the ultra high vacuum
chamber. These chambers can be replaced each otherwithin 1 hour. Each chamber can maintain 16
samples of 25 mm corner because of industrial use.
Measurement
In BL-5B, absorption spectra by means of the
TEY method were obtained for standard samples
in the soft X-ray region. The carbon K-edgenear-edge X-ray absorption fine structure (NEXAFS)
spectrum of graphite is shown in Fig.3. The spectrum
have been normalized to I0 and had a linear pre-edge
background removed. The peak at 285.4 eV [1]appears clearly, which is due to C1s→π* transition.
Additionally, the absorption spectra by means of
the TEY method were obtained for h-BN powder.
The boron and nitrogen K-edge NEXAFS spectrumof h-BN are shown in Fig.4 and Fig.5, respectively.

1s π *

280

1s

190

200
210
Photon energy (eV)
Grating=G1(100 grooves / mm)
S1=S2=100 µm, θ=45º

Fig.4 h-BN B K-edge NEXAFS spectrum

σ*

290
300
310
Photon energy (eV)
Grating=G1(100 grooves / mm)
S1=S2=100 µm, θ=90º

Fig.3 Graphite C K-edge NEXAFS spectrum

380

400
420
440
Photon energy (eV)
Grating=G2(300 grooves / mm)
S1=S2=100 µm, θ=45º

Fig.5 h-BN N K-edge NEXAFS spectrum
References[1] P. E. Batson: Phys. Rev. B 48 (1993) 2608.

Photoemission study of the Au-SrTiO3(100) surface
Yuichi Haruyama, Yoshihiro Aiura1, Hiroshi Bando1, Shinji Matsui
Graduate School of Science and LASTI, University of Hyogo
1National Institute of Advanced Industrial Science and Technology, AIST Tsukuba
Abstract
We have investigated the Au-SrTiO3(100) interface as a function of the Au evaporation using thephotoemission spectroscopy. In the valence band of SrTiO3, the broad state originating from O 2p
electrons and a state from Ti 3d electrons were observed between 3-9 eV and at 1 eV below theFermi level (EF), respectively. With increasing the Au evaporation, the decrease in intensity of thestate at 1 eV was observed. In the Ti 3p core-level, the decrease of the Ti3+ states was observed
after Au evaporation. These results indicate that the electrons transfer from the Ti3+ states of the
SrTiO3(100) surface to the evaporated Au.
Introduction
Since Haruta et al. discovered the catalytic
property of Au atoms on the transition metal oxidesurface [1], many studies on the electronic andgeometric structures of Au-transition metal oxideinterface have been performed so far [2].
Particularly, the strong catalytic property was foundin Au clusters on the transition metal oxide with thesize of less than 10 nm, and the oxidation of CO andthe epoxidation of C3H6 were observed even at low
temperature [2].
In this study, we studied theelectronic structures of the Au-SrTiO3(100) surface
as a function of the Au evaporation using thephotoemission spectroscopy.
Results and Discussion
In Fig. 1, a photoemission spectrum of the Ti
3p, O 2s, and Sr 4p core-levels before Au
evaporation is compared to that after Au evaporationof 5 Å. In each Ti 3p, O 2s, and Sr 4p core-level, theshift of the peak to lower binding energy side by 0.2
eV was observed after Au evaporation. In addition,
the intensity of the peak at ~35.5 eV decreased after
Au evaporation. In the previous photoemission
study of the Ti 3p core-level, the peaks at ~37.8 and~35.5 eV were assigned to the Ti4+ and Ti3+ states,
respectively. The Ti3+ states were produced by thetransfer of a electron to the Ti sites next to thesurface oxygen vacancies when the surface oxygen
vacancies were formed. Therefore, the decrease of
the Ti3+ states after Au evaporation means that theelectrons transfer from Ti3+ states tothe states to theFig. 1. Photoemission spectra of the Ti 3p, O
2s, and Sr 4p core-levels before Au evaporation
and after Au evaporation of 5 Å.

evaporated Au atoms. Before Au evaporation, the Sr
3d5/2 peak was located at 133.9 eV. With increasing
the Au evaporation at 5 Å, the peak at ~133.9 eV
shifted to lower binding energy side by 0.2 eV. The
shift of the peak in the Sr 4p core-level is identical tothat in the Ti 3p, O 2s, and Sr 3d core-levels. In theprevious photoemission study of the annealed
SrTiO3 surface, the band bending effect caused by
the surface Ti3+ states was observed. Therefore, theshifts of the Ti 3p, O 2s, Sr 3d, and Sr 4p core-levels
after Au evaporation are basically ascribed to theband bending effect caused by the decrease of thesurface Ti3+ states.
Figure 2 shows the photoemission spectra of
the Au 4f core-level as a function of the Au
evaporation. All spectra display Au 4f7/2 and 4f5/2
spin-orbit doublet peaks located at ~84.4 and ~88.0
eV, respectively. At 0.5 Å, the Au 4f7/2 peak was
located at 84.4 eV.
With increasing the Au
evaporation at 1 Å, the width of the peak at ~84.4
eV decreased drastically. In addition, the peak at~84.4 eV shifted to lower binding energy side by 0.4
eV. The further shift of the peak position to lower
binding energy side by 0.2 eV was observed at 5 Å.
In the top, the spectrum of the pure Au waspositioned for comparison and showed the peak at
83.8 eV, which is derived from bulk Au 4f
component. As for the peak at 83.8 eV observed on
the Au evaporated SrTiO3 surface, the binding
energy position is identical to that of the bulk Au 4f
component. Therefore, the peak at 83.8 eV isFig. 2. Photoemission spectra of the Au 4f corelevel as a function of the Au evaporation.

assigned to the bulk Au 4f component. This indicatesthat the deposited Au atoms at more than 1 Å areclose to the pure Au. In Fig. 3, the shift of the peakin the Au 4f core-level is plotted as a function of theAu evaporation. Since the shift of peak in the Au 4f
core-level is different from that in the Sr 3d corelevel, the shift of the Au 4f core-level is not ascribedto only the band bending effect (~0.2 eV).
Especially, at lower Au evaporation (0.5 Å), theelectronic structure seems to be different from that at
higher Au evaporation. The shift of the Au 4f corelevel is not a charge-up effect of the substratebecause no such effect was observed under thephotoemission measurements of the clean
SrTiO3(100) surface.
In the case of the Au
compounds, some Au 4f components on the higher
binding energy side were observed as compared tothat of the pure Au. However, the dependence of theenergy shift on the Au evaporation is not explained.
In the previous study of the Au-Si(100) surface,
Landree et al. pointed out a final state effect arisingfrom the formation of the Au cluster. According toLandree et al., the screening of the core-holeproduced by the photoemission process is weaker
when the cluster size becomes small. The positionof the Au 4f core-level shifted to higher binding
energy side. Therefore, there is a possibility that theshift to higher binding energy side is assigned to thefinal state effect caused by the formation of the Au
cluster on the Au-SrTiO 3 (100) surface The
dependence on the Au evaporation is explainable inthe case of the final state effect.
Figure 4 shows the photoemission spectra of thevalence band as a function of the Au evaporation. In
the bottom, the spectrum of the clean SrTiO3(100)surface is positioned. In the valence band region of
SrTiO3, the broad feature was observed between 3-9eV.
The broad feature between 3-9 eV ispredominantly derived from O 2p electrons [3]. At
0.5 Å, a peak at 6.4 eV appeared and the width of
the broad feature increased. With increasing the Au
evaporation at 1 Å, several peaks between 3 and 6
eV appeared.
With further increasing the Au
evaporation, the intensity of the peaks between 3 and

6 eV was dominant. For comparison, the spectrumof the pure Au was also positioned in the top andshowed two peaks at 3.0 eV and 6.0 eV and a flatfeature between EF and 2 eV. Two peaks at 3.0 eV
and 6.0 eV were predominantly derived from Au 5delectrons while the flat feature between EF and 2 eV
was predominantly derived from Au 6s electrons.
Therefore, several peaks between 3 and 6 eV are
predominantly derived from Au 5d electrons. In theinset of Fig. 4, the photoemission spectra near EF
were extended. In the spectrum of the clean SrTiO3
surface, a state at ~1 eV below EF was observed.
The state at ~1 eV below EF was derived from Ti 3delectrons [3], and was related to the Ti3+-oxygen
vacancy complexes. With increasing the Au
evaporation, the intensity of the peak at ~1 eV
decreased rapidly and the shift of the peak at lower
binding energy side was observed. With further
increasing the Au evaporation at 5 Å, the peak
disappeared with high background. The decrease inintensity of the state at ~1 eV below EF suggests thatthe electrons transfer from Ti3+ states to thedeposited Au atoms. This is consistent with theresults of the Ti 3p core-level. In Fig. 3, the positionof the state at ~1 eV below EF is also plotted with
the Au evaporation. The shift of the state at ~1 eV
below EF is different from that in the Au 4f and Sr
3d core-levels, indicating that the shift of the state at~1 eV below EF is not ascribed to only the band
bending effect. The state at ~1 eV below EF arisingfrom the Ti 3d electrons is positioned in the sameenergy to the Au 6s electrons of the deposited Au. In
addition, the electrons transfer from Ti3+ states to thedeposited Au was observed in this study. These
results suggest that the Au 6s electrons of thedeposited Au are hybridized to the Ti 3d electrons of
the substrate.

Fig. 4. Photoemission spectra of the valenceband as a function of the Au evaporation.

Fig. 3. In the left axis, the shifts of the peak in
the Au 4f and Sr 3d core-levels were plotted as afunction of the Au evaporation. The position of
the state at 1 eV below EF is also plotted in theright axis.

References[1] M. Haruta, N. Yamada, T. Kobayashi, S.
Iijima, J. Catal. 115 (1989) 301.
[2] M. Haruta, Cattech 6 (2002) 102.
[3] Y. Aiura, Y. Nishihara, Y. Haruyama, T.
Komeda, S. Kodaira, Y. Sakisaka, T. Maruyama,and H. Kato, in Advances in Superconductivity
VI, edited by T. Fujita, and Y. Shiohara ,Springer,
Tokyo, (1994) 983.

Effect of Al content on structure of native oxide films
on Zn-Al Alloys formed in atmosphere
Katsuhiro Nishihara1, Tatsuo Nagata1, Yasuhiro Masaki1, Masamitsu Matsumoto1,
Takeo Kudo1, 2, Hitoshi Uchida2,
3
Yuichi Haruyama , Kazuhiro Kanda3, Shinji Matsui3, Masahito Niibe3, Toru Mitamura3,
1 Corporate Res. and Development Lab., Sumitomo Metal Industries LTD.
1-8, Fuso-cho, Amagasaki 660-0891, Japan
2 Graduate School of Engineering, University of Hyogo
2167 Shosha, Himeji 671-2280, Japan
3 Lab. of Advance Sci. and Tech. for Industry, University of Hyogo
3-1-2 Koto, Kamigori, Ako, Hyogo 678-1205
Abstract
Structures of thin native oxide films on Zn-Al alloys, pure Zn and Al, which formed in
atmosphere, were investigated by means of photoemission spectroscopy using synchrotron
radiation (SR-PES) and Al-Kα radiation (XPS).
As a result, it is found that the surface compound of thin native oxide film on Zn-Al alloys
changes from zinc oxide to aluminum oxide with increasing Al content, and that the depth profileof the structure depends on Al content. Additionally, the ratio of Al content in native oxide film ismore than that in Zn-Al alloy.
alloys and pure zinc and aluminum for comparison.
In Zn-Al alloys, Al was added to Zn in the weightpercent of 0.1~70%.
The specimens were prepared by cutting 10 × 10
mm plate from Zn-Al alloy ingots, and then they
were mechanically polished with diamond slurry.
Finally, all specimens were exposed to atmosphere
for a week. As a result, native oxide films wereformed on polished surface of Zn-Al alloys.
SR-PES was performed at BL-7B. XPS was
carried out with XPS spectrometer (VG,
ESCALAB220i-XL) using monochromatized Al-Kα
radiation. Photoelectrons were detected at the angleof 90° to the surface in SR-PES and at the angle of
40° and 90° in XPS.
Fig. 1 shows XPS (1487 eV) and SR-PES (168eV, 252eV) spectra recorded on the native oxide film.
In native oxide films shown in Fig. 1 (b) ~ (d), Zn3p
peak around 90eV and Al2p peak around 75 eV wereobserved in XPS spectra. In the SR-PES spectra

Introduction
Zn coating is one of useful methods for protecting
steel sheets against corrosion. Recently, several ZnAl alloy coatings, which have better corrosion
resistance than zinc coating, have been invented, andthe hot-dip Zn-Al alloy coated steel sheets, where Al
is added to the Zn coating in the weight ratio of 5%,
55% and so on, are produced commercially [1].
In the previous study, the effect of Al content on
the corrosion resistance of Zn-Al alloy coated steel
sheets has been reported by many researchers [2-5].
The thin and amorphous corrosion product films,
which are formed on coating in the early stages, canbe confirmed directly by means of SR-PES [6]. In
this study, the native oxide films on Zn-Al Alloys
were investigated by means of SR-PES (168eV and
252eV) and Al-Kα radiation (1487eV).
Experiments and Results
The materials employed in this study were Zn-Al
Zn3p

Zn3p

Al2p

Zn3p

Al2p

Zn3p

Al2p

Al2p

168eV
252eV
1486eV(40°)(a) Zn1009080(b) Zn-0.2%Al
70 1009080(d) Zn-45%Al(c) Zn-15%Al

70 1009080

70 10090801486eV(90°)(e) Al70 100908070Binding energy [eV]Fig.1

SR-PES (168eV, 252eV) and XPS (1486eV) spectra of thin oxide film on Zn-Al alloys(a) Zn, (b) Zn-0.2%Al, (c) Zn-15%Al, (d) Zn-45%Al, (e) Al(168eV) of Zn-0.2%, Zn-15%Al and Zn-45%Al, Al2p
peak around 76eV was clearly detected, but Zn3p
peak was not clearly observed. In XPS spectra of Zn45%Al and Al, Al2p peaks were assigned to Al metal.
Fig. 2 shows the peak analysis to clarify the
structure of native oxide films on Zn-Al alloys. Eachpeak in photoemission spectra was divided into
Gaussian peaks with curve fitting method. The Alcontent ratio was estimated from the peak intensity
ratio of Al2p to the sum of Al2p and Zn3p. Each peakintensity of Al2p and Zn3p were corrected by thephoto-ionized cross section, which was shown in Fig.
3 [7].

film was more than that in Zn-Al alloy. Therefore, it
is found that the native oxide films on Zn-Al alloys
are composed of much Al content, that is, Al oxide.
Fig. 5 shows the peak position of Zn3p and Al2p in
XPS and SR-PES spectra. The detection depth in SRPES and XPS were estimated 1 nm or less and 4 nm
or less from the escape depth of photoelectron,
respectively [8]. Accordingly, it is concluded that thedepth profile of the structure in native oxide film isdepended on Al content in Zn-Al alloy, and that theratio of Al oxide in native oxide film increased withincreasing Al content in Zn-Al alloy.
168eV
252eV
1487eV (40 ﾟ )1487eV (90 ﾟ )

96
95
94

(a) Zn3p

93

Fig. 2 Peak analysis of Al2p and Zn3p peaks

Photo-ionizedcross section [Mb]1.0E+01

90
0.1
81
80
79

1
10
100
168eV
252eV
(b) Al2p1487eV (40 ﾟ )1487eV (90 ﾟ )

77

Zn3p

XPS

1.0E-01

76
75

SR-PES

1.0E-02

0.1

1

10

100

Al / (Zn+Al) [%] (Zn and Al)

1.0E-03
0

400

800

1200

1600

Photon energy [eV]Fig. 3 Photo-ionized cross section of Al2p and Zn3p[7]Fig. 4 shows the content ratio of Al to the sum ofZn and Al. XPS analysis measured a component of
native oxide films on Zn-Al alloys. On the other hand,chemical analysis determined a component of Zn-Al
alloys. Cleary, the ratio of Al content in native oxide
100

Al / (Zn+Al) [%.]
(Zn-Al alloy)

91

78

Al2p

1.0E+00

Binding energy [eV]92

XPS（ 40 ﾟ）
XPS（ 90 ﾟ）
Chemical analysis

80
60
40
20
0
0.1

1

10

100

Al / (Zn+Al) [%] (Zn and Al)

Fig.4 Al/(Zn+Al) for Zn-Al alloy and nativeoxide film on Zn-Al alloy

Fig. 5 Peak positions of Zn3p and Al2p peaksin XPS and SR-PES spectra

References[1] M. Sagiyama, in Research Report for
Fundamentals of Corrosion Protection and
Evaluation Methods on Zinc and Zinc alloy CoatedSteels, p.1, ISIJ, Tokyo (2005).
[2] Y. Hoboh, J. Surf. Finish. Soc. Jpn., 42, 160(1991).
[3] D. J. Blickwede, Tetsu-to-Hagané, 66, 821 (1980).
[4] Y. Uchiyama, M. Hasaka and K. Koga, Trans. Jpn.
Inst. Met., 27, 968 (1986).
[5] J. Oka, H. Asano, M. Takasugi and K. Yamamoto,Tetsu-to-Hagané, 68, A57 (1980).
[6] K. Nishihara, M. Kimoto, T. Kudo, H. Uchida, Y.
Haruyama, K. Kanda and S. Matsui, in Proc. ISIJ
Asia Steel/2006, p. 840, ISIJ, (2006).
[7] J. J. YEH and I. Lindau, Atomic Data and Nucl.
Data Table, 32, 7-8 (1985).
[8] C. R. Brundle, J. Vac. Sci. Technol., 11, 212(1974).

Surface Reduction in Silica Waveguide Films
Irradiated by Synchrotron Radiation
K. Moriwaki, Graduate School of Eng./ Kobe Univ., K.Kanda, LASTI/Univ. Hyogo.
S.Matsui, LASTI/Univ. Hyogo, and K.Watanabe, Photonics Labs/NTT
Abstract
Synchrotron radiation without a spectrometer by the NewSUBARU is used to change therefractive index in silica-based films for optical waveguide devices. Irradiated samples are shownto have a thin reduction layer on the surface as well as a deep refractive-index-change layer. This
two-layer model after the SR irradiation is confirmed by both optical absorption and reflection
measurements. The thickness of the surface reduction layer is determined to be less than 45 nm byetching the sample surface. Although the refractive index change is decreased drastically after
removing the surface reduction layer by etching, it still remains high (on the order of 10-2) enoughto apply the samples to various optical devices.
Introduction
We use synchrotron radiation (SR) for photoinduced refractive-index modifications in silicabased glasses for optical waveguide devices. Our
objectives are to induce large refractive-index
changes more effectively using SR without aspectrometer, and to investigate their origins
depending on wavelengths in the SR spectra. Our
previous results1) showed that a high refractive index
change by SR irradiation was obtained but also a thin
reduction layer was found on the sample surface
measured by XPS (X-ray photoelectron
spectroscopy). In our present experiments, the twolayer model including the surface reduction layer
after SR irradiation is characterized by opticalabsorption and reflection measurements or others todetermine their parameters such as a thickness and arefractive-index distribution.
Experiments and Results
Experimental conditions are almost the same as in
the previous experiments 1) . SR (from the
NewSUBARU BL6) was irradiated on samples
directly without a spectrometer. SR with an undulator(from the NewSUBARU BL-7A) was also used toinvestigate wavelength effects. The electron energyof the SR was 1GeV (a wavelength range of morethan about 1nm without a spectrometer). GeO2 doped
SiO2 or pure SiO2 glass films on Si substrates wereused in our experiments. Pure silica substrate without
a film was also used for an optical absorption
measurement. After the SR irradiation, refractive
indices for the samples were determined by an
optical reflection measurement for a film on a Si
substrate. XPS measurements were also used tocharacterize surface reduction states and their depth
distributions using a dry etching method.
We have measured optical absorption spectra forsamples of GeO2 doped SiO2 films on silica
substrates and silica substrates without films asshown in Fig.1. Dotted lines in Fig.1 indicate defects
of both Si E’ center (215 nm)2) and oxygen deficiency(245 nm). For silica glass in Fig.1, oxygen deficiency

defects at 245 nm are shown to be bleached and Si E’centers peak at 215 nm is generated after SR
irradiation. After etching the sample surface to adepth of 15nm, the absorbance decreases drastically,
this indicates removal of the surface reduction layer.
As the etched depth becomes deeper than the 15 nm,

Fig.1 Optical absorbance for SR irradiatedsamples of GeO2 doped SiO2 film on silica
substrate and silica substrates without films.
Optical absorbance is also shown at the bottom
for a sample of SR irradiated silica glass aftersome etching processes.

the absorbance is still decreased but is almost
saturated at etched depths of deeper than 45 nm. The
saturated absorbance after the etching is higher thanan initial one before the SR irradiation, especiallyaround a wavelength of 215 nm. It is important that
almost only the Si E’ center peak at 215 nm remains
after etching the surface to a depth of 100nm. Figure
1 shows that the Si E’ center defects may be thecause of the high refractive-index change without thesurface reduction layer in the SiO2 glass after the SR
irradiation.
In addition, we measured optical reflection
spectra from the SR-irradiated films on Si substrates.
Measured spectra were analyzed to determine therefractive indices and thicknesses by a simulation

Fig.2 Parameters characterized by opticalreflection measurements and their simulations
for samples before, after the SR irradiation andafter etching the irradiated sample, respectively.
including interference between the film surface andthe interface to the substrate. The obtained values areshown in Fig.2 for samples before irradiation, after
irradiation and after etching the irradiated one,respectively. The two-layer model was successfully
used to determine the refractive indices andthicknesses in a simulation for the optical reflection
spectra. The simulated thickness of the reduction
layer was almost the same as was obtained in theprevious XPS measurement1). Simulated refractiveindices are shown in Fig.3 for samples of before,
after SR irradiation and after etching the irradiatedone. The refractive indices in Fig.3 were obtained byfitting the measured optical reflection spectra tosimulated ones. Figure 3 shows that the refractive

index becomes high by the SR irradiation because of
the surface reduction layer, but it still remains highfor a sample after removing the reduction layer by
etching. This refractive index on the order of 10-2
without the surface reduction layer is high enough toapply it to optical devices. SR irradiation with an
undulator and the following analysis by XPS etc. is
now underway to investigate wavelength effects by
the SR irradiation.
Conclusions
For a sample irradiated by SR (BL-6) without aspectrometer, the refractive-index changes wereanalyzed successfully by a two-layer model including
a very high refractive-index layer by a reduction on
the surface and a high refractive-index layer without
the reduction. A thickness of the reduction layer wasdetermined to be less than 45nm by opticalabsorption measurements. Large refractive index
changes (10-2) were remained in a SiO2 film by the
SR irradiation after removing the reduction layer. Si
E’ center defects appeared in the film after the SR
irradiation, and their distribution was uniform in thedepth direction. Si E’ centers may be the cause of thehigh refractive-index change for a sample without the
reduction layer.

Fig.3 Refractive-index change for samples
before, after irradiation and after etching
determined by a simulation using the measured
optical reflection data.
References[1] K.Moriwaki et al., LASTI Annual Rep ort vol.
9 (2007).
[2] H.Hosono and Y. Abe, Phys. Rev. B46, 11445(1992).

Inhibition of Carbon Deposition on the Multilayer Mirror
Surface by Introducing Water Vapor
Masahito Niibe and Keigo Koida
LASTI, University of Hyogo
Abstract
In the EUV lithography tool, carbon thin film deposition on the surface of projection optics by
EUV irradiation degrades the reflectivity of the mirrors. An experiment was carried out toinvestigate carbon deposition and its mitigation on the surface of Mo/Si multilayer mirrors by
EUV irradiation with the introduction of water vapor. In the experiment of carbon deposition by
EUV irradiation in the coexistence of n-decane and water vapor, it was observed that carbon film
deposition was mitigated by controlling the water vapor pressure. However, the mitigation effecton carbon deposition was not uniform for the EUV intensity, and a large non-linear dependency on
the irradiation flux was observed.
Introduction
Contamination on the optical surface of an
extreme ultraviolet lithography (EUVL) tool is one of
the critical issues to be solved to commercialize thesystem. To develop a contamination-protection
technology for the surface of projection optics for an
EUVL system, various examinations were carried out
on Mo/Si multilayer mirrors. There are two kinds ofcontamination by EUV irradiation on projection
optics. They are carbon deposition and oxidation of
the Si layer atop of a Mo/Si multilayer. Both types ofcontamination decrease the reflectivity of multilayers
and cause a resultant decrease in the throughput of
the exposure tools. In our previous work [1], we havefound that carbon film deposition and surface
oxidation, which have been thought to occur
independently of surface degradation, are reactions
that occur competitively and antagonistically.
Therefore, it is important to balance the amount ofhydrocarbons that are the source of carbon film
deposition and that of oxidation gases, such as water
vapor. To extend this idea further and understand themechanism of the contamination, an experiment ofcarbon deposition mitigation by EUV irradiation in
the coexistence of n-decane and water vapor was
carried out.
Experiments
The details of the EUV contamination evaluation
system that we used have been reported elsewhere[2]. The sample was put in a holder fixed on x-z axial
automatic stages. The reflectivity of the sample wasmeasured by two photo-diode detectors (IRD,SXUV-100), one of which measured the direct beam
intensity when the sample was removed from theirradiation beam and another which measured thereflection beam intensity. EUV irradiation and themeasurement of the relative reflectivity change werecarried out in situ. By regulating the beam size using
a 100 μm diameter pinhole in the reflectivity
measurement, the reflectivities of 11 different
intensity points were measured in one series ofirradiation and measurement. The reflectivity map

was also obtained by using the pinhole. The sample
holder was electrically insulated from the chamber,and the electron emission current by EUV irradiation
was measured as the sample current. Using thesample current with a monochromated photon energyscan, in situ analysis and elemental mapping of theirradiated surface were carried out as soft X-ray
absorption spectrometry (XAS) with the total
electron yield mode [3].
The sample used for the EUV irradiation was a
Mo/Si multilayer mirror with a period of about 7 nm
and number of layer pairs of 50 and top of the surface
was coated by about 2 nm-thick Ru metal. The
ultimate pressure of the measurement chamber wasless than 2×10-7 Pa, and the main component ofresidual gas was water (M=18). Two lines of a gas
introduction system were equipped at themeasurement chamber, and the pressure of gas wascontrolled by a needle valve. In this experiment, oneline was used for introducing n-decane gas, andanother line was used for the introduction of water
vapor. The experimental condition of gas
introduction for the experiments is shown in Table 1.
Table I Experimental conditions.
---------------------------------------------------------------n-decane pressure(Pa)
3.0 × 10-5
Water Vapor pressure (Pa)0, 1.3 × 10-6
-5-5
1.3 × 10 , 5.0 × 10 , 3.0 × 10-4--------------------------------------------------------------Results
Figure 1 shows the sequential reflectivity change
at the irradiation center of multilayer mirrors underan atmosphere of a fixed n-decane pressure of
3.0×10-6 Pa as well as under a variable water vapor
pressure from 0 to 1.3×10-4 Pa . At a water vapor
pressure below 1.3×10-5 Pa, the relative reflectivity
increased by about 1% in the early stage of EUV
irradiation. The reflectivity then decreased gradually,
and the value became 97% at the EUV dose of 1200
J/mm2. On the other hand, at a water pressure greater

Relative reflectivity

1.01
1.00
0.99
0.98
0.97
0.96
0.95

200 400 600 800 1000 1200
Dose (J/mm2)

Fig. 1 Dose dependence of the relative reflectivity
change of Ru-capped Mo/Si multilayer mirrors by
EUV irradiation in the presence of n-decane gas
and water vapor atmosphere.
A reflectivity map of the irradiated area for the
sample of irradiation condition at an n-decanepressure of 3.0×10-6 Pa and a water vapor pressure of
5.0×10-5 Pa is shown in Fig. 2. As shown in Fig. 2,
the shape of the reflectivity drop was similar to thatof a doughnut, which means that the reflectivity dropat the irradiation center was not remarkable and thevalue was almost equal to that at the non-irradiatedarea. However, a large reflectivity drop occurred at
the periphery of irradiation center, where the EUV
intensity was rather small. The doughnut shapes of
the reflectivity distribution were observed for all
samples at water vapor pressures from 1.3×10-5 Pa to
1.3×10-4 Pa.
Figure 3 shows the distributions of the XAS
intensity of (a): C-K and (b): O-K absorption edgesof the sample, which are nearly proportional to thesurface atomic density of carbon and oxygen
elements, as reported earlier [3]. The distribution of
the carbon density was trapezoidal for the sample at a
27.0

R/R0
1.01
1.00
0.99
0.98
0.97
0.96
0.95

Z (mm)

26.5
26.0
25.5
25.0
11.0

11.5

12.0 12.5
X (mm)

13.0

Fig. 2 Reflectivity map of the EUV-irradiatedarea after irradiation in the presence of decane gas
at Pdecane= 3.6 E-6 Pa and PH2O=5.0 E-5 Pa at thedose of 1200 J/mm2.

Normalized intensity (a.u.)

PDecane=3.0E-6 Pa
Only Decane
PH2O=1.3E-6 Pa
PH2O=1.3E-5 Pa
PH2O=5.0E-5 Pa
PH2O=1.3E-4 Pa

1.02

water vapor pressure of 0 to 1.3×10-6 Pa. This
trapezoidal distribution was similar to the carbon
thickness distribution for the samples of only lower
decane gas pressures. On the other hand, for the
sample of a water vapor pressure higher than 1.3×105
Pa, the carbon concentration at the irradiation centerdecreased with increasing the water vapor pressure.
The shape of the distribution was similar to that of
the letter “M” (or two-dimensionally, doughnutshaped). The atomic concentration of oxygen at theirradiated area decreased from the non-irradiated area
for the samples at water vapor pressures below
5.0×10-5 Pa. However, the concentration of oxygen
became high at the irradiation center for the samples
at a water vapor pressure of 1.3×10-4 Pa. The
problem of the non-linear behavior to the EUV
intensity in the atmosphere into which water
vapor was introduced still needs to beresolved.
A part of this work was performed by using
the resources of NEDO.
PDecane=3.0E-6 Pa
Only Decane
PH2O=1.3E-6
PH2O=1.3E-5
PH2O=5.0E-5
PH2O=1.3E-4

5
4
3
2
1
-2

-1

0
X (mm)

1

2

PDecane=3.0E-6 Pa
Only Decane
PH2O=1.3E-6
PH2O=1.3E-5
PH2O=5.0E-5
PH2O=1.3E-4

1.15
Normalized intensity (a.u.)than 5.0×10-5 Pa, the rate of the reduction ofreflectivity was small, and the relative reflectivity
was 98.5% at the EUV dose of 1200 J/mm2.

1.10
1.05
1.00
0.95
0.90
0.85
-2

-1

0
X (mm)

1

2

Fig. 3 Normalized photo-absorption intensity
distribution of (a): C-K and (b): O-K edges at the
EUV-irradiated area after the carbon-deposition
mitigation experiment by water vapor.
References[1] M. Niibe et al., J. Vac. Sci. Technol. B26, 2230
(2008).
[2] M. Niibe et al., Jpn. J. Appl. Phys. 45, 5373-5377(2007).
[3] M. Niibe et al., J. Vac. Sci. Technol., B25, 2118
(2007).

Analysis of carbon deposition on multilayer mirrors by using
two different beamlines
Takahiro Nakayamaa, Hiroyoshi Kuboa, Akira Miyakea, Hiromitsu Takasea, Shigeru Terashimaa,
Yasuaki Fukudaa, Katsuhiko Murakamib, Shintaro Kawatab, Takashi Aokib, Shuichi Matsunarib,
Yukinobu Kakutanib, Keigo Koidab, Masahito NiibecaCanon, 23-10, Kiyohara-Kogyodanchi, Utsunomiya-shi, Tochigi-ken, 321-3298, Japanb
Nikon, 1-10-1, Asamizodai, Sagamihara-shi, Kanagawa-ken, 228-0828, Japan
cLaboratory of Advanced Science and Technology for Industry (LASTI), Univ. of Hyogo,
3-1-2, Kouto, Kamigori-cho, Ako, Hyogo 678-1205, Japan
Abstract
It is very important to mitigate oxidation of multilayer mirrors (MLMs) and carbon deposition
onto MLMs to extend the lifetime of EUV exposure tool. In order to estimate the lifetime, we haveto figure out scaling law. Previous results at EUVA have shown that carbon deposition rate on
MLMs is not proportional to every hydrocarbon partial pressure and every EUV intensity3-4. In thisstudy we focused on carbon deposition on Si-capped multilayer mirror. We made experiments of
EUV irradiation to the MLMs using two different apparatuses. One is connected to a beamline(SBL-2) of synchrotron radiation facility Super-ALIS in the NTT Atsugi research and development
center, and the other is connected to a beamline (BL9) of synchrotron radiation facility New
SUBARU in the University of Hyogo. As the result of experiments, we found that different carbon
deposition rate occurred on the different beamlines, although they have the same average EUV
intensity. We present differences of carbon deposition rate on MLMs between two different
beamlines and estimation of carbon deposition rate on EUV tool analyzing dependences of carbon
deposition rate on characteristics of EUV source.
Introduction
HVM (High Volume Machine) of EUV Scanner is needed to operate for several years
without high maintenance cost. In order to estimate a lifetime for HVM, we have to figure out
scaling law. We focus on the scaling law of contaminations on multilayer mirrors (MLMs).
Carbon deposition on MLMs causes a damage of optical performances. We have to elucidate aphotochemical reaction of EUV irradiation to the MLMs and estimate carbon deposition ratefor HVM. We found that carbon deposition rate is not proportional to average EUV intensity
and hydrocarbon partial pressure3-4. But we do not know dependences of carbon deposition
rate on characteristics of EUV source. So we need to make a comparison between different
EUV sources to understand the reaction quantitatively.
Experiments and Results
We made experiments using two different beamlines. One is a beamline (SBL-2) of synchrotron radiation
facility Super-ALIS in the NTT Atsugi research and development center. The other is a beamline (BL9) thatis a long undulator in NewSUBARU synchrotron radiation facility in the University of Hyogo. Table 1 shows
characteristics of both the EUV beamlines. Experimental data of carbon deposition rate at SBL-2 andreflectivity change at BL9 have been reported in detail in previous papers1-4. We set an irradiation time at 2 to
9 hours to acquire samples with suitable thickness of deposited carbon to analyze. Therefore the irradiation
time is different every sample. We injected decane (C10H22) that was selected because its vapor pressure ishigh enough to control its partial pressure easily in the irradiation chamber. Table 2 shows experimental
conditions of injected gases. We consider that the reason why water partial pressure is larger thanbackground pressure shown in Table 1 is to inject water with decane gas. We used X-ray photoelectron
spectroscopy (XPS) and obtained carbon deposition quantity from photoelectron intensity of C(1s). We candetect Ru(3d3/2) and C(1s) with XPS, but both binding energy are near values. So we cannot discriminate
between Ru(3d3/2) and C(1s) peaks. Therefore in this experiment, we used multilayer mirrors of [Si(4.2nm)/Mo(2.8 nm)]50 on Si-wafer, i.e. Si-capped MLMs. We converted photoelectron intensity of C(1s) into a
carbon film thickness. Furthermore, we calculated carbon deposition rate by dividing the carbon film
thickness by the total irradiation time. Average EUV intensity was calculated by dividing total EUV dose by
total irradiation time. We show dependence of carbon deposition rate on average EUV intensity in Fig. 1.
Injected decane pressures of Fig. 1(a) and Fig. 1(b) are ~1x10-6 Pa and ~2x10-7 Pa, respectively. Both results
show that the carbon deposition rate in BL9 is higher than that in SBL-2. Both carbon deposition rates are
saturating following average EUV intensity increasing. Comparing with both saturated carbon deposition rate,carbon deposition rate in BL9 is 3 to 5 times higher than that in SBL-2. The minimum average EUV intensity
to saturate carbon deposition rate in BL9 is over 4 times higher than that in SBL-2. The results show that a
carbon deposition rate depends not only on average EUV intensity, but also on other characteristics of EUV
source that can be source frequency and pulse width of EUV light.
Several models of the photochemical reaction under EUV irradiation have been reported5-9. In this study
we used NIST (National Institute of Standards and Technology) simple thick-C-growth model10 shown in Fig.
2 and we have fitted our experimental data of carbon deposition rate using the model. Surface reaction in
EUV light unirradiated is as follows:⎛ S (t) ⎞ S (t)dSM (t)= Z P ⎜⎜1 − M ⎟⎟ − M
dt
SMax ⎠
τS⎝

Photochemical reaction in EUV light irradiated is described as follows:⎛ S (t) ⎞ S (t)dS M (t)= Z P ⎜⎜1 − M ⎟⎟ − M − I EUV σ tot S M ( t )dt
S Max ⎠
τS⎝

SM(t) is coverage of adsorbed intact molecules [molecules *cm-2]. Smax is site-limited max coverage (=~1ML). ZP is impingement rate [molecules*cm-2*s-1]. τS is surface-residence time [s]. IEUV is incident EUV
intensity [photons*cm-2*s-1]. σtot is total cross section [cm2]. Carbon-growth rate, k [C atoms*cm-2*s-1], is
described as follows:k = νN C ∫0t P I peak σ tot S M ( t )dt

ν is source frequency. tp is pulse width. Ipeak is peak intensity when square wave pulse is assumed. NC is anumber of carbon atoms in a hydrocarbon molecule. Solving and using these equations, our experimental
data in SBL-2 were fitted with fitting parameters of surface-residence time and total cross section. We used
three experimental conditions at SBL-2. These partial pressures of decane are 1.2x10-6, 7.3x10-7 and 2.3x10-7
Pa. The total cross section σtot was 6x10-9 cm2. The obtained total cross section is large comparing withphoto-absorption cross section (3x10-19 cm2/atom) at EUV of “Si”. ASET has reported surface-residence timeof H2O on Si is two microseconds11. NIST has also reported surface-residence time of benzene on C/TiO2,
benzene on TiO2 and methyl methacrylate on TiO2, are 1x10-6~1x10-5 sec., 1x10-4~1x10-2 sec. and 10~1000
sec. 12, respectively. Our residence time (5x10-10 sec.) is shorter than theirs. The parameters need to beverified and modified. And calculation result does not correspond with our experimental result in higher
partial pressure 6x10-5 Pa. In EUVL symposium 2008, NIST has presented that a carbon growth has
logarithmic dependence over multiple decades of hydrocarbon pressure, which suggests adsorption model
similar to Temkin isotherm12. So we can use the equation and parameters in the limited conditions between
1.2x10-6 and 2.3x10-7 Pa. Using above parameters and equations we calculated dependences of carbon
deposition rate on average EUV intensity. The results are shown in Fig. 1 that has the same experimental
conditions as the experiments. We can see that calculation results have the same behavior of the experimental
result. So this indicates the possibility that source frequency and pulse width affect the carbon deposition. We
estimate dependences of carbon deposition rate on several source parameters. We calculate with threedifferent pulse width, 2.6x10-11, 1x10-8 and 1x10-4 seconds, and also calculate with three different source
frequency, 5x108, 5x104 and 150 Hz. We assume decane as an induced hydrocarbon molecule and partialpressure 1x10-7 Pa. Average EUV intensity is 0.1 mW/mm2. The dependences of carbon deposition rate on
source frequency and pulse width are shown in Fig. 3(a) and Fig. 3(b), respectively. The dotted circle
indicates experimental conditions. Figure 3(a) shows that carbon deposition rate is proportional to source
frequency in low source frequency. The other hand, carbon deposition rate is saturated in high source
frequency. We have considered that carbon deposition rate is limited by hydrocarbon pressure in low source
frequency and by number of photons in high source frequency. Figure 3(b) shows that carbon deposition rate
is proportional to pulse width in short pulse width and is saturated in long pulse width. These phenomena arecaused by the same reason as the dependence on source frequency.
In conclusion, we made experiments using two different beamlines and figured out the scaling law for
two beamlines. The carbon deposition rate depends not only on average EUV intensity. We used NIST
simple thick-C-growth model and fitted our experimental data of carbon deposition rate. Using the model andassuming parameters, we calculated dependences of carbon deposition rate on average EUV intensity. The
calculation results have the same behavior of the experimental data from 2.3x10-7 to 1.2x10-6 Pa of decane
partial pressure. As the calculation parameters are different from what we expected, the dependence ofcarbon deposition rate on characteristics of EUV source is not completely understood. Therefore the reaction
model needs to be verified and modified. There are also a lot of other works to be figured out in the future,which is dependence of carbon deposition rate on hydrocarbon partial pressure, on gas species and on
capping layer. Standing wave effect and quantitative data, total cross section and residence time in an eachgas species and capping layer material, also need to be figured out. Finally, It is important to make anexperiments using EUV source which has source frequency and pulse width like those for high volume
machine to figure out the scaling law.
A part of this work was performed as a research and development program of Ministry of Economy Tradeand Industry (METI) and New Energy and Industrial Technology Development Organization (NEDO) underthe management of Extreme Ultraviolet Lithography System Development Association (EUVA).
Table 1. Characteristics of the EUV beamlines.
Beamline Maximum EUV intensity
2(mW/mm )Diameter of EUV

Source frequency

Pulse width

Background pressure

irradiated area (mm)(MHz)

(psec.)

(Pa)

SBL-2

12~24

2

125

78

<5x10-7

BL9

~200

2

500

26

<5x10-7

Table 2. Experimental conditions.
Beamline

SBL-2

BL9

Decanepartial pressure (Pa)
6.0×10－5
1.2×10－6
7.3×10－7
2.3×10－7
1.2×10－6
2.5×10－7

Water
partial pressure (Pa)
2.1×10－6
4.6×10－7
3.6×10－7
3.0×10－7
3.3×10－6
3.5×10－7(b)(a)

carbon deposition rate (nm/h)

carbon deposition rate (nm/h)

1.6
1.4
1.2
1.0
calculation results
BL9
SBL-2

0.8
0.6
0.4
0.2
0.0
0

50
100
150
200
average EUV intensity (mW/mm^2)

Total pressure(Pa)
6.5×10－5
1.9×10－6
1.1×10－6
5.8×10－7
5.0×10－6
7.0×10－7

0.50
0.45
0.40
0.35
0.30
0.25
0.20
0.15
0.10
0.05
0.00

calculation results
BL9
SBL-2

0

250

Irradiation time
(hrs)
4
5
5
8
1.3
2.7

50
100
150
200
average EUV intensity (mW/mm^2)

Figure 1. Dependence of carbon deposition rate on average EUV intensity
Experimental data and calculation results at both beamlines are shown in Fig. 1(a) and Fig. 1(b).
Decane pressures are 1.2 x 10-6 Pa in BL9 and 1.2 x 10-6 Pa in SBL-2 in Fig. 1(a). Decanepressures are 2.5 x 10-7 Pa in BL9 and 2.3 x 10-7 Pa in SBL-2
BL-2 in Fig. 1(b).

ZP

1/τs

IEUV

SM(t)

Surfaceσtot

e eFigure 2. NIST simple thick-C-growth model.

250

(b)

1.E-0210 nsec.
26 psec.
78 psec.

1.E-03

1.E-04
1.E+04 1.E+06 1.E+08 1.E+10
source frequency (Hz)carbon deposition rate (nm/h)

carbon deposition rate (nm/h)(a)1.0E-02

500 MHz
125 MHz

50 kHz1.0E-03

1.0E-04
1.E-10 1.E-08 1.E-06 1.E-04
pulse width (sec.)

Figure 3. Dependence of carbon deposition rate on source frequency and on pulse width.
Dependence of carbon deposition rate on source frequency and on pulse width are shown in Fig. 3(a) and
Fig. 3(b), respectively. Dotted circle indicates experimental conditions.

REFERENCES[1] M. Niibe, “New contamination experimental equipment in the NewSUBARU and evaluation of Si-capped
multilayer mirrors using”, Proc. of SPIE Vol. 6151, 34, 2006
[2] Y. Kakutani, “Long-term durability of a Ru capping layer for EUVL projection optics by introducing
ethanol”, Proc. of SPIE Vol. 6517, 31, 2007
[3] H. Takase, “Study of Ruthenium-capped Multilayer Mirror for EUV Irradiation Durability”, Proc. of SPIE
Vol. 6151, 35, 2006
[4] T. Nakayama, “Phenomenological analysis of carbon deposition rate on the multilayer mirror”, Proc. of SPIE
Vol. 6921, 3B, 2008
[5] Ralph Kurt et al.,"Radiation－induced carbon contamination of optics", Proc. of SPIE 4688, 702－709, 2002
[6] Jeromy T. Hollenshead and Leonard E. Klebanoff, "Modeling carbon contamination of extreme ultraviolet(EUV) optics", Proc. of SPIE 5374, 675－685, 2005[7] J. Hollenshead et. al., "Modeling radiation－induced carbon contamination of extreme ultraviolet optics", J.
Vac.Sci. Technol. B 24(1), 64－82, 2006
[8] S. Matsunari et. al., "Carbon deposition on multi－layer mirrors by extreme ultra violet ray Irradiation", Proc.
of SPIE 6517, 2X, 2007
[9] S. B. Hill et. al., "Accelerated lifetime metrology of EUV multilayer mirrors in hydrocarbon environments",
Proc. of SPIE 6921,42 , 2008[10] S. B. Hill et. al., “Limits to accelerated MLM lifetime testing: TiO2 in hydrocarbons and Ru in H2O”,
IEUVI-TWG, EUVL symposium, 2007[11] I. Nishiyama, “Model of Ru surface oxidation for the lifetime scaling of EUVL projection optics mirror”,
Proc. of SPIE Vol. 6151,0G-1, 2006[12] S. B. Hill et. al., “EUV-induced contamination of TiO2 surfaces by anticipated tool-environmenthydrocarbons”, EUVL symposium, 2008

Improvement of EUV-mirror reflectance measurement
stability on Beamline 9 of NewSUBARU
Yukinobu Kakutania and Masahito NiibebabNikon, 1-10-1, Asamizodai, Sagamihara-shi, Kanagawa-ken, 228-0828, Japan

Laboratory of Advanced Science and Technology for Industry (LASTI), Univ. of Hyogo, 3-1-2,
Kouto, Kamigori-cho, Ako, Hyogo 678-1205, Japan

EUV-mirror reflectance changes during EUV irradiation (13.5nm) have been measured as lifetime
tests of multilayer mirrors (MLMs) on the beamline 9. To evaluate the mirror reflectance changes
due to EUV irradiation, the reflectance measurement error is required to be less than +/- 0.5%.
In Beamline 9 of NewSUBARU , we can measure two beam positions near a focus point of thebeam line and just in front of sample position, which were used for the beam position adjustment.
We can also measure the EUV beam intensity through a pinhole in a 100um diameter, which has
been used in a reflectance measurement.
Changes in beam intensity through a pinhole set just in front of sample position and beam
positions along horizontal and vertical axes at near a focus is shown in Fig. 1.
Comparing the beam position near the focus and the beam intensity, it was found that a part ofexperimental errors were originated from both horizontal and vertical drift of beam positions during
the reflectance measurements of 5 or 6 min. It was also found that jumps of beam position, which
may be connected to COD correction. In addition to the beam drifts, the noise of the EUV detector
output in the reflectance measurement system (the ammeter read error ) affects to experimental error.
Each experimental error was estimated to be +/-0.2% for the horizontal drift, +/- 0.25% for thevertical drift, +/- 0.35% for the beam jump, and +/- 0.2% for the read error of the ammeter. The total
experimental error, which was convoluted from each error, was about +/-0.5%. The experimental
error width was not small for mirror reflectance measurements. The system was improved asfollows:
1. The feedback system of the beam position was improved by changing amplifiers of the position
measurement to be faster, which makes the beam drift small.
2. The read error of the ammeter was improved to +/-0.1% by changing the integration time which
octuple from 166 ms to 1.33 s.
3. The measurement data at the beam jump are omitted using a revised measurement programcode easily. Using the revised code a reflectance measurement is able to be done within 1 minfrom 5-6 min.
Each experimental error improves to +/-0.15% for the vertical drift, +/- 0.1% for the read error of
the ammeter, and the errors for the horizontal drift and for the beam jump can be negligible. The
total experimental error +/-0.2% was achieved.
This error can be small enough to measure the reflectance change in recent evaluatedsamples.

㩷㪙㪼㪸㫄㩷㫀㫅㫋㪼㫅㫊㫀㫋㫐㩷㪙㪼㪸㫄㩷㫇㫆㫊㫀㫋㫀㫆㫅㩷䋨㪟㫆㫉㫀㫑㫆㫅㫋㪸㫃䋩㩷㪙㪼㪸㫄㩷㫇㫆㫊㫀㫋㫀㫆㫅㩷䋨㪭㪼㫉㫋㫀㪺㪸㫃䋩㪚㪿㪸㫅㪾㪼㩷㫀㫅㩷㪹㪼㪸㫄㩷㫀㫅㫋㪼㫅㫊㫀㫋㫐㩷㪆㩷㪹㪼㪸㫄㩷㫇㫆㫊㫀㫋㫀㫆㫅䋨䋦䋩

㪈㪅㪌

㪈㪅㪇

㪇㪅㪌

㪇㪅㪇
㪇

㪊㪇

㪍㪇

㪫㫀㫄㪼㩷䋨㫄㫀㫅䋩
Fig. 1. Changes in beam intensity through a pinhole set just in front of sample position and beam
positions along horizontal and vertical axes at near a focus in Beamline 9.

Electronic State Analysis of Minor Elements in
Ultra-fine Grained Metallic Materials
M. Terasawa, T. Mitamura, M. Niibe, LASTI, University of Hyogo
T. Yamasaki, Dept. of Materials and Chemistry, Graduate School of Engineering, University of Hyogo
H. Kurishita, Institute for Materials Research (IMR), Tohoku University
M. Kawai, Institute of Material Structure Science, High Energy Accelerator Research Organization (KEK)
Abstract
Ultra fine grained (UFG) materials of SUS316L and W were fabricated by mechanical alloying(MA) and hot isostatic pressing (HIP) treatments. It was found that addition of about 1 % TiC
powder was effective to reduce the grain size down to 100nm, and the materials exhibited superior
irradiation resistance and mechanical properties. The electronic states of the TiC in the UFG
materials were analyzed by XANES spectroscopy at NewSUBARU BL9.
Introduction
Life extension of nuclear power plants is one of
the major recent targets to be developed for
economical electric-power generation. The extension
means prolonged use of nuclear fuels and core
reactor materials in nuclear reactors. On the other
hand, in the J-PARC program, which is a large
accelerator development project in Japan to promoteuse of secondary particles, such as neutron, pi- andmyu-particles, neutrino and so on, produced by highenergy proton beam bombardment. For the neutron
source in the J-PARC facility, liquid mercury target
enveloped with metallic container is planned to be
adopted.
The metallic materials are likely to deteriorate in
the nuclear water reactors due to radiation hardening,
embrittlement, and/or stress corrosion cracking. The
environment for the materials of the neutron sourcein J-PARC is much severe. It is strongly expectedthat the materials are developed so as to show toughresistance for such phenomena.
We are developing ultra-fine grained materials of
austenitic stainless steel (316L) and W with additionof small amount of TiC powder. In this work,
electronic state analysis of TiC in the W-TiC
materials was investigated by XANES spectroscopy
in order to elucidate the effect of TiC addition.

(En>0.1 MeV). The hardness increase of the materials
after the irradiation is only 6.0 %, though muchhigher increase (73 %) is shown in the simultaneous
irradiation of the standard SUS316L specimens. The
lower void swelling of the ultra-fine grainedmaterials than standard 316L is also found in 1 MeV
electron irradiation, as shown in Fig. 1.[1,2]Experiments and Results
Fabrication of ultra-fine grained materials
Ultra-fine grained materials of austenitic stainlesssteel (SUS316L) and W were fabricated bymechanical-alloying (MA) and hot isostatic pressing(HIP) treatments. Powder of SUS316L (an average
particle size: 44 – 105μm) or pure W (4.0μm),
combined with TiC (0.57 and 40μm, respectively),
were used as the starting materials.
The SUS316L-1.0wt.% TiC materials with theaverage grain sizes of 100 nm were obtained by 80 %cold roll and annealing at the temperature of 800℃,
after MA and HIP (800℃) treatment. The fabricatedmaterials have exhibited good resistance to neutron
irradiation examined in JMTR up to 1.14 x 1024 n/m2

Electronic state analysis of TiC in UFG materials
In the fabrication of the UFG materials, small amount(about 1 wt.%) of TiC addition is found extremely
effective to control the grain size in both materials of
SUS316L and pure W, as described above. Although
it is suggested that TiC nano particles act so as to pin
the grain boundary during the fabrication process,what kind of interaction of TiC with matrix materials
is concerned, and by what mechanism the pinning isgoverned are not clear.
We tried to measure the electronic states of Ti in theW-1.1wt.% TiC consolidates, as a preliminary step toelucidate the behavior of Ti or TiC in the fabrication
process. XANES spectroscopy was performed at theend-station of the long undulator beamline BL9 in
the NewSUBARU SR facility using a high resolution

Fig.1 Void swelling of the UFG SUS316L-TiC
irradiated by 1 MeV electrons at 400℃
The ultra-fine grained (UFG) W-1.1wt.% TiCmaterials are obtained with the grain size of 50 – 100
nm, and have exhibited superior resistance to theirradiation with neutrons and helium-ions.[3,4]insulated holder
samplerear focusing mirror (M2)3

Normalized absorption [a.u]monochromator [5]. The data were collected by atotal electron yield (TEY) mode in which the sample
current was measured when the photoelectron
emitted by soft x-ray absorption. The values werenormalized with a simultaneously recorded
photoemission signal from a gold mesh, whichindicate the soft x-ray intensity incident into thesample. The measurement system is shown in Fig. 2schematically. At the present time, XANES spectra of
Ti-L and C-K absorption edge of TiC in the W1.1wt.% TiC consolidates were measured.

: W-TiC #A
: #B
: #G

2.8
2.6
2.4
2.2
2
1.8
445

450

455

460

465

470

475

480

485

Photon energy [eV]Fig.4. Ti-L2,3 edge XANES spectra of UFG W-TiC
materials

gold-meshexit slit

I0pico-ammeter

plane VLS gratingI

Fig.2. Schematic diagram of XANES measurement
in total electron yield mode
Fig. 3 shows Ti-L2,3 absorption spectra for pure Ti(99.99 %) metal and TiC powders measured forreference before the XANES study for the fabricated
W-TiC materials. A peak of Ti-L2 (2p1/2) and L3(2p3/2) was observed at 465.9 eV and 461.4 eV,
respectively, in the Ti specimen. On the other hand,each of L2 and L3 spectral line exhibits twin peakstructure with an additional line with a separation of
about 1.5 eV for the TiC powder specimen. The
spectral variation is reflected by electronic structure
due to different chemical state.
Normalized absorption [a.u.]

6

4.5

:

TiC

:

Ti

powdermetal: W-TiC(1%): TiC powder

4
3.5
3
2.5
2
1.5
1

5

280

290

300

310

320

Photon energy [eV]4

Fig.5. C-K edge XANES spectra of TiC and UFG WTiC materials

3
2
1
0
445

The XANES spectra observed show characteristic
twin peak structures for both L2 and L3, which are in
general agreement with the spectra shown in TiC
powders. Somewhat deformed profiles of the twin
peaks in the W-TiC materials may be due to theexistence of partly decomposed Ti and/or otherchemicals such as oxides or nitrides. Although we
tried to measure Ti-L2,3 electrons for the W-TiC
specimens by the XPS previously, the electrons was
hardly observable, the present XANES studies weresuccessful as described above.
Normalized absorption [a.u.]

LU light
source

450

455

460

Photon465

470

energy

475

480

485

[eV]

Fig.3. Ti-L2,3 edge XANES spectra of Ti and TiC
Fig.4 shows XANES spectra of Ti-L2,3 for the UFG
W-1.1wt.% TiC specimens. Three kinds of materials,
which fabricated by different environment
mechanical alloying in order to investigate the plastic
behavior, are examined. That is, #A; treated at
1650℃ in H2 environment, #B; treated at 1650/
1850℃ in H2 environment, #G; treated at 1650℃ inargon environment. The materials treated in H2 arefound to exhibit a large strain rate sensitivity of flow
stress, m, of 0.5 – 0.6, which is a feature ofsuperplastic materials, while the ones treated in argon
exhibit a smaller m value of approximately 0.2.[6]The XANES spectra of C-K edges for W-1.1wt.%
TiC and powder TiC are compared in Fig. 5. The
reduction of π* peak at 285 eV and enhancement of
the peak at 288 eV is prominent for the W-1.1wt.%
TiC specimens. This change may give an importantelectronic state transition information during the MA
and HIP process in the UFG material fabrication.
References[1] Y. Z. Cheng et al, Material Science Forum, 426432, pp.1065-1070 (2003).
[2] H. Matsuoka et al, Proc. ICAPP’05, Seoul, Korea(2005) paper 5687.
[3] H. Kurishita et al, Phys. Scr. T128 (2007) pp.7680.
[4] H. Kurishita et al, IWSMT-8 (2006).
[5] M. Niibe et al., AIP Conf. Proc. 705, 576 (2003).
[6] H. Kurishita et al, Mater. Sci. Eng. A (in press).

Soft X-ray Absorption Spectra of TiO2 Thin Films
Prepared by Magnetron Sputtering Technique
Masahito Niibe1, Masanori Kayahara2 and Shozo Inoue2
LASTI1 and Graduate School of Eng. 2, University of Hyogo
Abstract
Soft X-ray Absorption Spectra (XAS) of Ti-L2,3 and O-K edges were measured for the samples ofTiO2 thin films prepared by magnetron sputtering technique. The samples were deposited byreactive RF-magnetron sputtering system at incident angles of sputtered particles to substratenormal of 0° (normal) and 80° (GLAD). The samples were also annealed at 300°C. The Ti-L2,3edge spectra indicates that the prepared samples contain almost the same amount of rutile andanatase crystalline structures. It was also found from the O-K edge spectra that the absorption
intensity of the broad peak, 10 eV higher energy than the O-K edge, increased remarkably
compared to t2g and eg peaks by the annealing.

Experimentals
The TiO2 thin film samples were prepared by RFmagnetron sputtering technique. A reactive sputtering
deposition was carried out with a use of Ti metaltarget and mixture gas of Ar and O2. The substrate
was a Si wafer and the sample holder was able to tilt
from the sputtered particle beam. The incident anglesof sputtered particles to substrate normal were chosen
0° (normal deposition) and 80° (GLAD). A part ofprepared samples were annealed at 300°C for 60 min
in an air environment.

The evaluation of photocatalytic activity was
conducted by measuring the absorbance change ofmethylene blue solution, in which prepared TiO2 film
was dipped and UV light was irradiated for 1 ~ 24
hrs with the use of a black light [2].
XAS of the samples were measured by thespectrometer at the beamline 9 (BL9) in the
NewSUBARU SR facility. Total electron yield(TEY) method with sample current mode was
employed for the XAS measurement. The
measurement was carried out at the absorption edgesof Ti-L2,3 (~455 eV) and O-K (~530 eV). The
measurement was also carried out for TiO2 powder
samples with rutile and anatase structures asreferences.

Normalized absorption [a.u.]

3.5

L3

3

: Anatase: Rutile

L2

2.5
2
1.5
1
0.5

t2g eg
0
450

460

470

480

Photon energy [eV](a) Ti-L2,3 edge
3.5

Normalized absorption [a.u.]

Introduction
Titania (TiO2) is known as a material whichshows a strong oxidative power by UV irradiationand is actively studied in the wide fields of photolysis
of water, sterilization and superhydrophilic treatmentof solid surfaces etc. It is desirable for titania thinfilms used as photocatalyst that the specific surface
area of thin film is made as large as possible. We
have shown that oblique columnar structures evolvedin sputter deposited films when they were grownunder a highly oblique angle (e.g. 80°) between theflux of sputtered particles and the substrate normal[1]. This technique is called as glancing angle
deposition (GLAD) and has a potential to provide
materials with a large specific surface area. We
adopted this technique to prepare the TiO2 thin film
and compared the normally (0°) deposited one.
Titania is known to take crystalline structures ofrutile and anatase, mainly. It is also said that thephotocatalytic activity of anatase structure is muchhigher than that of rutile structure. However, in the
preparation of TiO2 thin film, it is sometimes very
difficult to identify the structure of the thin film
because the intensity of X-ray diffraction is generally
very weak. In this study, we tried to identify the
structure of prepared TiO2 thin film with the use ofsoft X-ray absorption spectra (XAS). We also
investigated to compare the difference inphotocatalytic activities between as-deposited andannealed samples as a difference of electronic
structures obtained by the XAS.

: Anatase: Rutilet2g eg

3
2.5
2
1.5
1
0.5
0

520

540

560

580

Photon energy [eV](b) O-K edge
Fig. 1 XAS of rutile and anatase powder samples.

Figure 2 shows Ti-L2,3 XAS of TiO2 thin films
prepared by (a): normal deposition and (b): GLAD.
These spectra are very similar to those of reference
powder samples. As shown in Fig. 2, the eg peak of
L3 edge split further into two peaks. These peaks arecorresponded to eg peaks of rutile and anatasestructures as mentioned in Fig. 1. The intensity of
8Normalized absorption [a.u.]: as-deposied: annealed

t2g eg7
6
5

Figure 3 shows the O-K edge spectra of normal
deposited TiO2 thin films. In the O-K edge spectral
profile, the shape of t2g and eg peaks is similar to
those of reference powder samples. However, theprofile of broad peak at higher energy is like anintermediate shape of rutile and anatase structure.
The intensity of the broad peak at the higher energy
increased remarkably compared with those of t2g andeg peaks by annealing. This intensity increase byannealing was also observed in the sample of GLAD.
4: as-deposited: annealed

t2g eg

3.5
3
2.5
2
1.5
1
0.5
0

4

520

540

560

580

Photon energy [a.u.]

3

Fig. 3 O-K edge spectra of normal deposited TiO2
thin films.

2
1
0
450

460

470

480

Photon energy [eV](a) Normal deposition
7

Normalized absorption [a.u.]both split peaks are almost the same. Therefore, we
can estimate that the prepared sample contained
almost the same amount of rutile and anatase
crystalline structures in both samples of normal and
GLAD.
As shown in Fig. 2(b), anatase/rutile ratio of TiO2
thin film deposited by GLAD was not changed byannealing with 300°C. On the other hand, as shownin Fig. 2(a) for normal deposited sample, the amountof rutile structure is a little greater than that ofanatase structure in the as-deposited sample.
However, anatase/rutile ratio increases slightly byannealing with 300°C.

Normalized absorption [a.u.]

Results
Figure 1 shows the XAS near the (a): Ti-L2,3 edgeand (b): O-K edge of rutile and anatase powder
samples. Both spectra are very similar to thosereported previously [3]. Ti-L3 and L2 resonanceabsorption peaks in both powder samples are split
into two peaks, which is resulted from the energy
split of Ti3d and O2p hybridized orbits by oxygen
tetrahedral ligand field. The peaks in lower andhigher energy is called “t2g” and “eg”, respectively.
The spectra of Ti-L2,3 edges for rutile and anatasepowder samples are very similar in each other. The
most remarkable difference in both spectra is that thepeak of eg in L3 edge is leaned to higher energy forrutile sample and to lower energy for anatase sample.
The lower energy peaks of O-K edge for both
samples are also split into two peaks, which are also
resulted from the same ligand mechanism. The peaks
are also called “t2g” and “eg”. In the O-K absorption
spectrum, there is a broad peak at about 10 eV higher
than the absorption edge at 530 eV, which isunderstood to be resulted from the O2p hybridized
orbits with Ti4s and Ti4p.

6: annealed: as-deposited

t2g eg5
4
3

According to the experiment of photocatalytic
activity evaluation, the photocatalytic activity of thefilm annealed at 300°C was observed to increase.
Therefore, there is a good correlation between theincrease in photocatalytic activity and that inabsorption intensity of broad peak at higher energy of
O-K edge by the annealing. There might be somerelation between the local structural change byannealing and change in O2p hybridized orbit with
Ti4s and Ti4p.

2
1
0
450

460

470

480

Photon energy [eV](b) GLAD
Fig. 2 Ti-L2,3 XAS of TiO2 thin films prepared bynormal deposition and GLAD.

References[1] S. Inoue et al., J. Jpn. Soc. Precision Eng., 72,
919 (2006) in Japanese.
[2] “Wet dissociation test method for photocatalyst
products” The Japanese Association of Photocatalyst
Products 2004. 05.28, in Japanese.
[3] S. O. Kucheyev et. al., Phys. Rev. B 69, 245102(2004).

Development of a Soft X-ray Emission Spectrometer
Tohru Mitamura, Masahito Niibe, Yasuji Muramatsu*, Kazuo Taniguchi**
LASTI, University of Hyogo,*Department of Engineering, University of Hyogo,** Institute of X-Ray Technologies Co., Ltd.
Abstract
Soft X-ray emission spectrometer is currently under development to the beam line, BL9a.
Outlines of the emission spectrometer are given and the progress of the development is reported.
Introduction
Soft X-ray emission spectroscopy (soft XES)
provides a means of probing the partial occupied
density of electronic states of a material. Whenenergetic beams such as synchrotron radiation or ion
beams are irradiated to target materials, inner shellelectrons of the constitution elements of the target are
excited to unoccupied levels above the Fermi level.
Spectra obtained from the X-ray absorption
spectroscopy (XAS) reflect the electron density
distribution of unoccupied energy levels.
To the radiation-induced inner shell holes,
electrons of the occupied higher energy states transit
to the holes and X-rays with excess energy are
emitted subsequently. Spectra obtained from the XES
reflect the electron density distribution of theoccupied energy levels under the Fermi level. XES iselement- and site-specific, hence it is a powerful toolfor determining detailed electronic properties or
chemical structure of materials.
As the X-ray emission is a relaxation process
following primary X-ray absorption one, the intensityof emitted X-ray is generally very weak. Accordingly,
the soft X-ray emission spectroscopy requires
intensive excitation source, in anyway we can use ion
beam or light source, so as to accomplish a highprecision experiment within a limited amount of time.
Hence light source with high luminosity from asynchrotron radiation is advantageous.
The beam line, BL-9a, with the long undulator
emission provides energy-variable intensive lightsource. To this beam line, a soft XAS system has
been applied and effectively utilized for investigationof surface structure of solids. In addition to the soft
XAS system, it is desirable to equip a soft XES
system so as to improve detecting systems for thephenomena related to soft X-rays. In the present
report, basic outline and progress situation of the soft
XES under development are reported.
Outline of the soft XES under development
The soft XES under development is a type of
the wavelength dispersive X-ray spectrometer(WDS). It has been originally designed by thegroup of one of the authors, K. Taniguchi, forobservation of photo-emission phenomena fromtarget materials irradiated by energetic-ions. In
the present development, the design of thespectrometer is modified and improved to install
to BL-9a of the New SUBARU.
Fig.1, shows the partially build-up inner partsof the spectrometer. In the figure, S, G and D are
the emitted X-ray entrance slit, the diffraction
grating and the CCD detector, respectively. The S
and G are attached to a support frame which is

F2

F1
S

G

D

Fig.1 Inner view of the X-ray emission
spectrometer (XES). S: entrance slit, G: concave
diffraction grating, D: CCD detector. F1and F2 areconflate flanges. They are connected by a welding
bellow.

fixed to the flange F1. The F1 is connected to aport of the target chamber. The detector D ismounted on a support frame which is fixed to theflange F2. The F2 is independently shifted theposition in the horizontal (X-axis) and the vertical(Y-axis) directions in order to lie the detector on acircle called the Rowland circle.. The angle of D
(θ-axis) can be adjusted so that the surface istangent to the Rowland circle. Each movement of
three axes is driven by a stepping motor. The F1and F2 are connected by a welding bellows.
The stepping motors are Oriental motor
products. The ones for X and Y axes are equippedwith magnet brakes. All of the motors are driven
and controlled by a driver and controller unit,
Mark204-MS, which is a Sigma-koki product.
This unit is equipped by a GPIB terminal throughwhich the system is controlled by a personal
computer, using the software, LabVIEW.
The grating is a type of concave diffraction
grating with 3600 lines/mm. The CCD detector is
two dimensional type with the area of 10x28 mm2.
The center of the detector is set so as to betangent to the Rowland circle, hence peripheral

aberration is processed by an image-processing
method in order to maintain the good resolution.
The CCD detector is cooled through a cold finger
attached to the cylindrical Dewar vessel which
can be seen in the Fig.1.
We have also another detector, silicon drifted
detector (SDD). This is a type of energy
dispersive X-ray spectrometer (EDS). The WDS
detector has an advantage of good resolution anda disadvantage of long measurement time. In
contrast, EDS detector has an advantage of shortmeasurement time and a disadvantage of low
resolution. According to experimental purposes,
EDS is more suitable than WDS. We have a plan
to attach the SDD to a port of the target chamber.

Fabrication of Narrow Pitch and High Aspect Ratio Microcoils
for Electromagnetic Microactuators
Daiji Noda, Yoshifumi Matsumoto, Masaru Setomoto, and Tadashi Hattori
Laboratory of Advanced Science and Technology for Industry, University of Hyogo
Abstract
The demand of micro-fabrication such as microactuators, microcoils, smart sensors is increasing.
Actuators, which held big volume and weight with a part of a product, have been required toreduce their size. However, the miniaturization of electromagnetic actuators has made little
progress since it requires three-dimensional micro-fabrication processing and new technologies.
Therefore, we have fabricated a spiral microcoil with narrow pitch and high aspect ratio coil line
structures using a deep X-ray lithography and metallization techniques. We have fabricated spiralmicrocoils at a pitch of 20 m. Thus, an aspect ratio of coil lines was achieved about 5 as coil linesof 10 m. In the case of 30 m line and space pattern, we obtained an aspect ratio of about 3. Byusing these techniques, microcoils with narrow pitch and high aspect ratio can be achieved, which
are expected to yield high performance.
Introduction
Recently, the demand of micro-fabrications suchas microactuators, microcoils, sensors, etc is very
increasing. Actuators, which hold big volume andweight with a part of a product, have been required toreduce their size. However, the miniaturization of
actuators has made little progress since it requires
three-dimensional (3D) micro-fabrication processing
and new technologies. On the other hand, LIGA
(German acronym for Lithographite Galvanoformung
and Abformung) process [1] can be fabricated nanoand micro parts for devices. This technique ispossible to make high aspect ratio structure fixed thenarrow pitch of coil line and space. In addition, the
X-ray exposure stage was carried out with theworkpiece held in a specially manufactured nineparts operation [2]. Thus, this stage makes it feasible
to do 3D deep X-ray lithography for microcoils.
Therefore, we have fabricated a spiral microcoil withhigh aspect structure for electromagnetic typemicroactuators using a 3D deep X-ray lithography
and metallization techniques.
Design of electromagnetic actuator
As the structure of the magnetic circuit, we used
the type called open frame solenoid, which is open
on the sides [3]. The material of electromagnetic core(fixed core and plunger) and shield parts (yoke) wereused Permalloy that is a nickel iron alloy, because it
has the largest permeability among soft magnetic
metals. When the electrical supply to the coil isturned on, a magnetic flux forms in the gap,
deforming the magnetic field and producing suction
force on the plunger. If the aspect ratio is increased,
the cross section area of coil lines is also increased
allowing a greater current path. Then, the magneto
motive force is proportional to the squares of current
path in the microcoil in this model. This
microactuator having the high aspect ratio of coil line
is also expected a high performance in spite ofminiature size.

Fabrication process of microcoil
X-ray lithography was carried out for deep X-ray
lithography in New SUBARU synchrotron radiation
facility of our university at the operation energy of
1.5 GeV. The surface of acrylic pipe for a screw
thread structure, this is the coil part, has made using
LIGA process.
Figure 1 shows the fabrication process of
microcoil. First, a cylindrical structure was formedon the surface of acrylic pipe by X-ray lithography.
Next, copper was thinly deposited on pipe surface by
sputtering in order to use as a seed layer in theelectroforming. And, copper was formed into narrow
pitch spiral structure by electroforming. Then, pipe
surface was completely covered with copper film.
Finally, forming Cu layer over the pipe surface wasetched until the isotropic portions of wiring were
X-ray

X-ray mask

X-ray lithography

Cu sputtering

Formation of seed layer

Electroforming of copper

Chemical etching

Fig. 1: Process flows of microcoil

exposed. We have fabricated a spiral microcoil at a
pitch of 20 m, as shown in Fig. 2. Thus, an aspectratio of coil lines was achieved about 5 as coil linesof 10 m. In the case of 30 m line and space pattern,

between plunger and fixed core was adjusted X-, Ystage. The theoretical values by simulation and actual
measurement results of suction force generated by
the microcoil were compared, as shown in Fig. 5.
These results are relatively in good agreement withtheoretical values.

Aspect ratio 5 or more

40

20 µm

Fig. 2: SEM image of coil lines with aspect ratioof 5
we obtained the aspect ratio of 3. Following the seedlayer deposition, we formed uniform copper
electroplating for the current path of microcoils. In
this result, it was able to be confirmed that plating
developed to reach the bottom surface of the grooves,
as shown in Fig. 3. Finally, Isotropic copper etching
was performed until the insulated portions of thewiring were exposed, as shown in Fig. 4.

30 μm

Fig. 3: SEM image of coil lines after copper
electroforming

Suction force (mN)

Expermental v alue
Calculated v alue

30

20

10

0

1

2
Gap (mm)3

Fig. 5: Suction force comparison between
measurement values and simulation
results
Conclusions
We have fabricated microcoils with high aspectratio using a 3D deep X-ray lithography andmetallization technique in order to produce
electromagnetic microactuators. We succeeded in
producing a threaded structure with10 m in coillines width and about 5 in the maximum aspect ratio.
On the other hand, we produced a measurement
system to measure a suction force. In thismeasurement, theoretical values by simulation results
and actual measurement of suction force werecompared. By using these techniques, microcoilswith high aspect ratio can be achieved, which are
expected to yield high performance. It is anticipatedthat high performance microcoils could also be
manufactured, in spite of their miniature size.
Acknowledgment
This research is partially supported by the Grantin-Aid for Scientific Research on Priority Area, No.
438,"Next-Generation
Actuators
Leading
Breakthroughs", from the Ministry of Education,
Culture, Sports, Science and Technology, Japan.

30 µm

Fig. 4: SEM image of coil lines by isotropic
copper etching

Measurement of suction force
We have also fabricated a measurement system tomeasure the suction force of designed electromagnetic type actuators. This system is very simple
structure and easy to exchange the coil part. The gap

References[1] E. W. Becker, W. Ehrfeld, P. Hagmann, A. Maner,and D. Munchmeyer, Microelectron. Eng., 4, pp.
35-56 (1986).
[2] H. Mekaru, S. Kusumi, N. Sato, M. Yamashita, O.
Shimada, and T. Hattori, Jpn. J. Appl. Phys., 43,
6B, pp. 4036-4040 (2004).
[3] Y. Matsumoto, M. Setomoto, D. Noda, and T.
Hattori, Microsyst. Technol., 14, 9-11, pp. 13731379 (2008).

Fabrication of X-ray Grating Using X-ray Lithography
Technique for X-ray Phase Imaging
Daiji Noda, Hiroshi Tsujii, and Tadashi Hattori
Laboratory of Advanced Science and Technology for Industry, University of Hyogo
Abstract
X-ray radiographic imaging technique is very important in medical, biological, inspection,material science, and so on. However, it is not enough to obtain clear X-ray images of samples
with low absorbance materials, such as biological soft tissues. Then, we have used an X-ray phaseimaging method of an X-ray Talbot interferometer. In this method, X-ray gratings were required tohave narrow pitch and high aspect ratio structure. Therefore, we have developed and fabricatedhigh aspect ratio X-ray gratings with a pitch of 5.3 μm, a height of 30 μm, and a large effective
area of 100 mm × 100 mm using X-ray lithography and narrow electroforming technique. In thispaper, we discuss the fabrication process of X-ray gratings and results of X-ray phase tomographyusing an X-ray Talbot interferometer with these X-ray gratings.
Introduction
X-ray radiographic imaging technique is very
important in medical, biological, inspection, materialscience, and so on. However, it is not enough toobtain clear X-ray images of samples with low
absorbance materials, such as biological soft tissues.
On the other hand, several methods for generating
radiographic contrast from the information of X-ray
phase shift have been investigated. It is improvementin the high sensitivity by about 1000 times higher
than by conventional absorption contrast.
Numerous researchers have studied a variety ofmethods of phase imaging [1,2]. X-ray Talbot
interferometer (XTI) is one of the methods of X-ray
phase imaging [1]. It offers many advantages: a) it isa very simple setup using two gratings; b) it does notneed a high mechanical stability; c) a widely area
imaging is possible; d) a detector for imaging does
not need a high resolution, and e) it functions with abroader energy band width much than in the case ofusing crystal optics. Therefore, these advantages havemade the XTI attractive for application in medical
diagnostics. In order to use 10-40 keV X-ray
irradiation, the Au thickness of absorptive materialmust be over 20 μm. But, it is not straightforward to
make this structure with high aspect ratio by
conventional techniques. Then, we have tried infabricating such X-ray gratings particularly with alarge area (100 × 100 mm2) using X-ray lithography
technique.

μm and a height of 4 μm resist pattern were
fabricated. Au was formed into resist structure ofnarrow lines by electroforming. And, we have used
SU-8 as membrane because of large effective area Xray mask. In this study, SU-8 was spin coated at 40
μm thickness. We attached a SUS frame on
membrane in order to support X-ray mask. Finally, Si
substrate and Ti seed film were removed by wet
etching with potassium hydroxide (KOH) andbuffered hydrogen fluoride (BHF) solution,
respectively. We succeeded in making X-ray maskwith pitch pattern of 5.3 μm and large effective areaof 100 × 100 mm2.

I. Seed layer deposition
V. Frame bonding

II. Resist patterning

VI. Si wafer removing

VII. Seed layer removing
III. Electroplating ofabsorptive material
Si

IV. Membrane coatingAu

Ti
membrane

resistf rameFig. 1: Fabrication process of X-ray mask
Fabrication of X-ray mask
First, we fabricated an X-ray mask for grating
patterns. For large effective area of X-ray grating, wedeveloped a large area X-ray mask structure. Figure 1
shows fabrication process of X-ray mask for X-ray
grating pattern with pitch of 5.3 μm [3]. A titanium
film was formed on Si substrate by sputtering toserve as electroforming of Au absorptive material.
Next, negative type photoresist of SU-8 was spin
coating and patterning by ultraviolet (UV)
lithography technique. In this research, a pitch of 5.3

Fabrication of X-ray grating
The X-ray lithography using synchrotron
radiation has been utilized for 2.5-dimensional
applications on flat substrate. Therefore, we took
advantage of this technology to fabricate a highaspect ratio structure required for X-ray gratings witha pitch of several micrometers. For X-ray lithography,
we used NewSUBARU beamlines 2, which is thesynchrotron radiation facility owned by ouruniversity [4]. The beamline 2 has a potential of large
area patterning across an A4-size area with a highly
uniform pattern thickness.
A target specification of the X-ray grating was 5.3
μm pitch pattern and large effective area of 100 ×
100 mm2. For the deep X-ray lithography, we used anegative photo-resist SU-8. This SU-8 was originallydesigned for UV lithography. However it could also
be used in deep X-ray lithography of high accuracy
and high aspect ratio pattern. The pattern quickly
collapses when the rinse solution is dried in thedevelopment and washing process, as shown in Fig. 2.
In order to solve this problem, we used supercriticalwashing and drying machine (product by RyuSyo
Industrial Co., Ltd.) using carbon dioxide (CO2) as
the supercritical fluid because it is safe and has a low
critical point lower than those of other fluids. Figureshown in Fig. 4. Next target of X-ray grating is
improvement of precision, smaller pitch and higher
aspect ratio structure.

Fig. 4: SEM image of X-ray grating in crosssectionFig. 2: SEM image of narrow pitch structurewith sticking

Fig. 3: SEM image of narrow pitch structure
without sticking
3 shows an image of high aspect ratio structure
without sticking. From this figure, processing depth
was obtained about 35 μm with narrow pitch of
5.3μm. Thus, an aspect ratio was achieved of about
13.
Au absorbing part for the X-ray grating wasformed by electroforming. In electroforming,
chromium was used as seed film. A non-cyanic based
solution was used for Au electroforming. From theseresults, the designed pitch of 5.3 μm and height ofabout 30 μm of X-ray grating are realized [5], as

Conclusions
We have fabricated X-ray gratings having a pitchof 5.3 μm and a large effective area of 100 × 100
mm2 for X-ray Talbot interferometer of use in X-ray
phase imaging. To make a higher aspect ratio X-ray
grating, we developed the fabrication processcomposed of X-ray lithography and microelectroforming method. In X-ray lithography,
sticking was observed because of surface tension.
Therefore, we introduced a supercritical washing anddrying machine using CO2 as the supercritical fluid.
In this result, the resist structure with high aspectratio and narrow pitch was obtained without surface
tension in large area, such as effective area of 100 ×
100 mm2. After Au electroforming, large area andnarrow pitch X-ray grating could be fabricated.
This result suggests that XTI is a novel andsimple method for phase sensitive X-ray radiography,
and promising method for many imaging applications.
Acknowledgment
This research was supported by the research
project “Development of Systems and Technology
for Advanced Measurement and Analysis” from theJapan Science and Technology Agency (JST).
References[1] A. Momose, Jpn. J. Appl. Phys., 44, 9A, pp.
6355-6367 (2005).
[2] C. David, B. Nöhammer, H. H. Solak and E.
Ziegler, Appl. Phys. Lett., 81, pp. 3287-3289(2002).
[3] D. Noda, M. Tanaka, K. Shimada, and T. Hattori,
Jpn. J. Appl. Phys., 46, 2, pp. 849- 851 (2007).
[4] Y. Utsumi, T. Kishimoto, T. Hattori, and H. Hara,
Microsyst. Technol., 13, 5-6, pp. 417-423 (2007).
[5] D. Noda, H. Tsujii, N. Takahashi, and T. Hattori, J.
Electrochem. Soc., 156, 5, pp. H299-H302 (2009).

Fabrication of Micro Capacitive Inclination Sensor by Resin
Molding
Hiroaki Miyake1, Kazufumi Nishimoto1, Satoshi Nishida2, Daiji Noda1, and Tadashi Hattori1
1
Laboratory of Advanced Science and Technology for Industry, University of Hyogo
2
Nanocreate Co., Ltd.
Abstract
In various leading-edge technology industries, there is a growing need to reduce the weight andincrease the energy saving performance of various electronics products. Less costly production
technology is now under development to enable the production of less expensive MEMS devices.
In this situation, there is a pressing need to develop micromachining technology and a production
process suitable for mass produced MEMS. The LIGA process is a technology, which isconsidered to be suited for mass production, enabling the creation of a microstructure bytransferring a pattern from this master mold to a resin. In this study, we fabricated a micro
capacitive inclination sensor by using combination of a resin forming method and a mold. If asmall inclination sensor, having a size of several millimeters, could be made using a resin forming
method, production costs could be substantially reduced compared to sensors made with theconventional MEMS process.
Introduction
In various leading-edge technology industries,
there is a growing need to reduce the weight andincrease the energy saving performance of various
electronics products. Although MEMS (Micro
Electro Mechanical Systems) technology [1] is notsuited for mass-produced sensors since silicon isbrittle and expensive and its processing iscomplicated, involving many processes. The LIGA
process is a technology, which is considered to besuited for mass production, enabling the creation of a
microstructure by transferring a pattern from thismaster mold to a resin.
In this research, we fabricated a micro capacitive
inclination sensor [2] by using combination of a resin
forming method and a mold. If a small inclination
sensor, having a size of several millimeters, can bemade using a resin forming method, production costs
can be substantially reduced compared to sensors
made with the conventional MEMS process. Since
the dimensions of its sensing region are 5 × 5 × 3
mm3, which are much smaller than the dimensions ofconventional sensors, this inclination sensor is
expected to be widely used in the field where
efficient and reliable attitude control is a primaryfactor to be considered.
Micro capacitive inclination sensor
Figure 1 shows the working principle of a micro
capacitive inclination sensor fabricated in this study.
Two semicircular opposing electrodes are set above
one circular common electrode, as shown in Figs. 1aand 1b, so that two capacitors are formed. The region
between the opposing electrodes and common
electrode is half filled with oil. The oil insidemaintains its level due to gravity when the sensor
inclines, so that the amount of oil changes in eachcapacitor, as shown in Fig. 1c. As a result, thecapacitances change, and the angle of inclination of

the sensor can be detected, based on this change inthe capacitance values. Capacitance change of thecapacitor on the one side of the electrodes C isexpressed the proportional inclination angle  [2].

Common Electrode
Distance is about 44µm
Opposing electrode A

Opposing electrode B(a) Section structure
Inclination
angle

θDiameter is
4mm or lessOil(b) Horizontal(c) Inclination

Fig. 1: Principle of micro capacitive inclination
sensorFabrication process of sensor
Figure 2 shows the fabrication process for the
micro capacitive inclination sensor. In the first step,
the spacer part of this mold was transferred to a resinby hot embossing molding [3]. The common
electrode was formed on the molding prepared.
Specifically, an electrode film was formed, only at
the recesses on the slit-structured surface having
projections and recesses. A patterning method using amask would be a viable method for forming anelectrode at a specified position. Using this method,
however, it is very difficult to bring a mask into
proper alignment with a non-flat surface; this method
also has a drawback in respect of cost. In the case of
the process that is the subject of this paper, asignificant cost reduction is possible, since anelectrode film can be formed without using a mask.

(A) Resist spreading

successfully, only in the recess in the structure, using
the proposed new process.
We successfully fabricated a micro inclination
sensor as a molded product. In future, we will carryout wiring to complete this inclination sensor, andthen conduct performance evaluations, as shown in
Fig. 4.

Forming Common
Electrode Process

Mold Fabrication Process

Resist(I) Cu spatteringCuSi(B) UV exposure

Photo Mask

(J) Resist spreading
Resist(C) Development(K) O2 ashing(D) Cu spattering
Cu(L) Cu etching(E) Ni electroformed
Ni(M) Removal of Resist(F) Removal of Si，Cu and Resist

1mm

Fig. 4: Picture of completed sensor

Packaging Process(N) Anodic bonding Opposing

Molding Processelectrode(G) Molding

Mold
Resin

(O) Oil injection

Oil(P) Sealing

Seal(H) After Molding

Fig. 2: Fabrication process for sensor using
molding
Formation of electrode on resin molding
The inclination sensor comprises two electrodes,
i.e., a common electrode and opposing electrode, toform a capacitor. Figure 3 shows images of the crosssection of a molding on which resist had been coated,using a spin/spray coating system. As shown in thisimage, resist smoothly followed the projections andrecesses in the pattern. After resist coating, theElectrode region

Junction region

100µm(a) after resist coating

Electrode region

Junction region

100µm(b) resist had been planerFig. 3: SEM image of pattern in cross section
thickness of the resist film on the electrode region
was the same at that of the film on the junction
region. Therefore, if O2 ashing were performed on amolding having a uniform thickness of resist, resist
could not remain only in the recess in the electroderegion. Therefore, we placed a resist-coated sample
in a container filled with solvent vapor so that resist,
exposed to solvent vapor, would melt and beplanarized. As is evident from Fig. 3b, the resist
coating on the junction part was very thin, comparedwith a sample, shown in Fig. 3a, which had not yet
been planar. Cu electrode was thus formed

Conclusions
Based on low cost molding techniques suited formass production, we have fabricated a micro
capacitive inclination sensor by using a resin moldedcomponent. We prepared a mold by UV lithography
and Ni electroforming. In addition, using the hot
embossing molding technique, we fabricated astructure in which our pre-designed projections andrecesses were realized. We proposed a new process
for forming electrodes, only in the recesses in afabricated resin molded component, without using amask, and successfully fabricated the common
electrode of an inclination sensor. The process
proposed and established in this study requires noalignment and makes possible a substantial cost
reduction. Although we faced a difficult task ofplanarizing resist in this process, we used solvent
vapor for planarization with satisfactory results. We
successfully fabricated a micro inclination sensor as amolded product. In future, we will carry out wiring tocomplete this inclination sensor, and then conduct
performance evaluations. The techniques using resinmolded parts have the potential to be applied to the
production of, not only inclination sensors, such as
the one fabricated in this study, but also MEMS
devices. If the techniques using resin-molded parts
are introduced to the mass-production of MEMS
devices, including sensors, at low cost, the range of
their applications will further expand to new areas oftechnology and industry.
References[1] F. Kohsaka, J. Liang, T. Matsuo, and T. Ueda,
IEEJ Trans. SM, 127, 10, pp. 431-436 (2007).
[2] H. Ueda, H. Ueno, K. Itoigawa, and T. Hattori,
IEEJ Trans. SM. 126, 12, pp. 637-642 (2006).
[3] N. Ishizawa, K. Idei, T. Kimura, D. Noda, and T.
Hattori, Microsyst. Technol., 14, 9-11, pp. 13811388, (2008).

Fabrication of Ultraviolet Range Light Guide Plate
Yuta Okayama1, Kenji Yamashita1, Yoshitaka Sawa2, Daiji Noda1, and Tadashi Hattori1
1
Laboratory of Advanced Science and Technology for Industry, University of Hyogo
2
Sawa Plating Co., Ltd.
Abstract
The light guide plate, as part of the backlight unit in a cellular phone or liquid crystal display, has
evolved to meet market demands for low power consumption, high-luminance and high-quality
displays. Along with the advance of the light guide plate, LEDs have undergone development aslight source for light guide plates. Surpassing the limitations of LED emission in the visible light
range, LEDs that emit ultraviolet light have been developed. In recent years, the ultraviolet lightare used as a source of light of the air cleaner, and it is used as a source of light to activate thetitanium oxide which is photocatalyst. Common ultraviolet light sources are either line or point
light sources. There are no surface light sources capable of providing uniform lighting. We studies
surface illuminators that incorporate diffusers in the visible light range. Applying our existing
technology, we constructed an unprecedented ultraviolet surface illuminator and measured it usinga photocatalyst.
Introduction
In recent years, liquid crystal displays (LCDs)
have come to be widely used in cellular phones andTV sets. This popularity has led to growing demand
for a higher performance light guide plate as an LCD
component. In the light guide plate, light is guided
from a light emitting diode (LED) or other point lightsource to desired locations via total internal reflection
rendered by index of refraction differential between
air and diffuser material. The light in light guide platetears a total reflection condition by reflecting in aninternal projection (dot) and irradiates the surface.
The light guide plate, converts point light source tosurface illumination. Figure 1 shows a schematic
diagram of a light guide plate. One advantage of thelight guide plate is its efficient use of light throughthe conversion of point light source to surface
illumination. Our laboratory conducts studies on thedesign of a light guide plate that achieves a highuniformity ratio [1]. To apply our technology tosurface illuminators using ultraviolet (UV) light,
which have begun to be used recently in home aircleaners, we have embarked on fabricating a lightguide plate specifically designed for UV LEDs. For
light guide plate fabrication, we used UV-LIGA
Light Guide

Reflector Sheet

LED

Dot

A cross section

Fig. 1: Schematic diagram of light guide plate

process, which enables fine pattern processing
technologies [2]. And, we proposed to termed UV
diffraction exposure in order to form a fine, threedimensional bump shape [1].
In this study, optimal bump shape and allocation
were derived for UV surface illuminators. Indeed, alight guide plate was fabricated using the molding
technology.
Design of light guide plate
In achieving uniform surface illumination with alight guide plate alone, it is very important to form
the shape and allocation of reflective bumps.
Optimization of bump shape and allocation enables
the creation of a light guide plate for uniform
illumination. A ray-tracing simulator was used toderive the optimal bump shape and allocation. First,
the optimal bump shape was obtained. The bumpshape was transformed from a cylindrical column toa truncated cone, using fixed dimensions of 30 mheight and 52 m base diameter. Simulation results
revealed that strong light was emitted near 60 to 70
degrees taper angle, as in the visible light range. In
the next step, emission angle distribution was
obtained for 60 and 70 degrees taper angle truncatedcones. As suggested by the results, high output andmaximum perpendicular emissions from the surface
are achieved from a truncated cone with a 70 degrees
taper angle.
In the next step, optimal bump allocation wasderived for the 70 degrees taper angle. In this study,
the light guide plate we fabricated had bumps in a 48
by 88 mm area on a 52 by 96 mm board 2.6 mm
thickness. The optimal bump allocation wasdetermined by thinning filled bumps, on the basis ofsimulation results. The bumps were selected
randomly. Therefore, the process was repeated toderive the optimal bump allocation for uniform
illumination. Figure 2 shows simulated analysis
results. The fully uniform placement of bumps wasobtained. Before bump allocation optimization,
output characteristics were such that the maximum
value was 6.39W/m2 and the minimum value was
1.15 W/m2. After optimization, the maximum value
was reduced to 3.23 W/m2, while the minimum value
was increased to 1.82 W/m2. The uniformity ratio,
which is an indicator of the degree of illumination
uniformity, improved from 35% to 91%.

of the fabricated light guide plate were measured toverify that the light guide plate would provide
uniform illumination. Energy values were calculated
from the spectral response characteristics of thephotodiode and the wavelength of the light emitted
by the LED. The energy distribution was obtained as
closely simulation result, as shown in Fig. 4. In thesimulation, the maximum and minimum values were
3.23 W/m2 and 1.82 W/m2, respectively, while themolded light guide plate provided maximum andminimum values of 4.25 W/m2 and 3.10 W/m2,
respectively. The maximum value increase from thesimulation results was probably due to some entry
angle deviation that occurred at LED mounting.
However, the higher minimum value suggests thatthe fabricated light guide plate was better than thesimulated one used for analysis.

(a) Uniform arrangement (b) Optimum arrangement

Fig. 2: Energy distribution of light guide plate
Fabrication of light guide plate
Since the shape was micro sized, the UV-LIGA
process was used to fabricate an ultraviolet lightguide plate, designed as above. As regards the master
pattern, a structure was created by lithography,
painting with resist that is photosensitive resin wafer.
Next, copper was sputtered onto the surfaces of thecreated master pattern. A mold was then fabricatedthrough Ni electroforming. Since the light guide plate
was to be fabricated by injection molding, it wasnecessary to set the size to accommodate a cavity for
injection molding. Consequently, the Ni thickness
was set at approximately 4 mm for electroforming.
Lastly, the light guide plate was produced throughinjection molding using the mold as a cavity. Figure
3 shows the exterior and an SEM image of theinjection molded light guide plate. The achievedbump shape was obtained at 10 m in top diameter,
52 m in base diameter, 70 degrees in taper angle
and 30 m in height.

Fig. 3: Top view and SEM image of fabricatedlight guide plate
Evaluation of light guide plate
Using a photodiode, the emission characteristics(a) Simulation result(b) Measurement result

Fig. 4: Energy distribution of light guide plate
Conclusions
We fabricated an unprecedented UV surface
illuminator and assessed its capacity as a light source
for reactivating photocatalysts. Bump shape andallocation for uniform illumination of UV light were
derived through simulation, achieving uniformity
ratio improvement from 35% to 91%. The light guideplate for ultraviolet light was fabricated throughapplication of visual-light diffuser fabrication
techniques, i.e., the UV-LIGA process and UV
diffraction exposure. The fabricated light guide plate
presented performance comparable to simulation
results, with a minimum value exceeding analysis
results, though the uniformity ratio did not reach thesimulation results.
References[1] T. Tanaka, T. Nomura, Y. Funabiki, T. Kitadani, K.
Idei, K. Yamashita, D. Noda, and T. Hattori,
Proceedings of the 2006 IEEE International
Symposium on Micro-Nano Mechatronics andHuman Science, Nagoya, Japan, pp. 480-485(2006).
[2] Y. Sawa, T. Tanaka, T. Kitadani, H. Ueno, Y.
Itoigawa, K. Yamashita, D. Noda, and T. Hattori,
Microsyst. Technol., 14, pp. 1559-1565 (2008).

Fabrication of the 3 Dimension Resist Microstructure Using

X-ray Diffraction and Applying to LIGA Process
1

Daiji Noda1, Kyo Tanabiki1, Yoshitaka Sawa2, and Tadashi Hattori1
Laboratory of Advanced Science and Technology for Industry, University of Hyogo
2
Sawa Plating Co., Ltd.

Abstract
The LIGA process consists of lithography, electroforming and molding has attracted attention in
microstructure fabrication techniques. At the molding process of LIGA process, it is difficult topull out from the mold that is assumed of especially high aspect ratio structure. However, releasefrom mold is improved by tapered structure. In this research, we proposed that the diffraction
exposure technique which makes use of diffraction phenomenon. Diffraction is caused byproviding a clearance between a resist structure and an X-ray mask. The fabricated structure was
the lines and intermediate space whose processed width was 200 m and designated the taper
angle 5 degrees as set point. The experiment parameters were done by distance of gap, dose of Xray and slit width. It is controlled that discovering the conditions for taper angle of 5 degrees andinspecting the relationship between taper angle and mold releasability by electroforming and themolding of the LIGA process. We have fabricated a mold with taper angle of 2.5 degrees byelectroforming. The Ni mold could partially copy the master pattern well.
Introduction
Today, People are surrounded by abundant
cellular phones and other information processing
equipment, including computers, liquid crystal
televisions, portable music players, automobiles, andso on. With these products, it is understandable thatthe market demands higher performance. In order tomeet such demands, the development of parts with
reduced size and increased performance is under way.
For size reduction and performance improvement,
micro-structures and micro-systems are attracting
engineers’ attention. The fabrication of microstructures has progressed technical improvements inthe fields of machining and Micro Electro
Mechanical Systems (MEMS) technology.
Sensors are fabricated through establishedsemiconductor processing technology, which uses aplanar processing technique. But, actuators ofcomplex shape require the use of micro 3D structure
processing technique. At present, the most promisingfabrication technology for micro 3D structures is the
LIGA process [1]. This process is a combination oftechnologies such as a metal mold master making thedeep X-ray lithography with the sub-micrometers
pattern formation, electroforming of nickel mold, andprecise molding that use the metal mold thatcomparatively have generality.
Removing a cast from mold in molding of LIGA
process, especially in the case of high aspect ratio
structures, requires an elaborate design. Otherwise, it
is impossible to remove the cast without breaking thestructure. The mold releasing property of a structure
improves if structure is tapered. In this paper, wehave proposed a method of achieving a tapered shape,by means of a gap provided for X-ray diffraction
between X-ray mask and resist structure for moldmaster. The structures reported in this paper featurelines and intermediate spaces. Target values were 200

m in processing width, 5 degrees in taper angle, andlarge effective area of over 40  45 mm2.
Experimental method
To fabricate for high aspect ratio 3D structures,
we have used the NewSUBARU synchrotron
radiation facility of University of Hyogo. For X-ray
lithography, beamline 2 (BL-2) has a potential oflarge area patterning across up to full-A4-size areawith a highly uniform pattern thickness. Due to its
high directivity, synchrotron radiation light iscommonly used to create 2.5-dimensional structures.
However, it is possible to cause X-ray diffraction by
providing a large gap between X-ray mask and resist
structure. Exposure using of the diffraction enables
the fabrication of a tapered 3D structure [2].
In this research, for the purpose of substratepreparation, a polymethylmethacrylate (PMMA)
sheet with 200 m in thickness, which is a positive
type photoresist, was affixed to a silicon substrate by
the bonding method, a method of forming aphotoresist. In this method, a PMMA solution, which
serves as adhesive, is fed between a PMMA sheet ofdesired thickness and a silicon wafer, or substrate;pressure is then applied to the PMMA sheet with amachine press to spread the PMMA solution to a
uniform thickness, and the PMMA sheet is bonded tothe silicon substrate by polymerization of the solution
to form a resist. Figure 1 shows an outline of the Xray diffraction method used for creating lines andintermediate spaces. For the diffraction of X-ray
exposure, two types of simple jig were made andused to enable gap adjustment by replacing the spacer.
The two jigs differed in spacer thickness for gap
adjustment. One was capable of adjusting the gap
between 40 and 80 mm, while the other was enabledadjustment from 120 to 150 mm gap.
In this paper, parameters for diffraction were usedX-raySlit width
X-ray mask

Gapphotoresist
Substrate

Fig. 1: Image diagram of tapered structure andoutline of X-ray diffraction
slit width, dose of X-ray and gap between X-ray
mask and resist structure, which were varied. These
quantities were selected as parameters, since it was
believed that slit width and gap would affectdiffraction and the dose of X-ray would exert aneffect on processing width as well as on diffraction.
The cross section of the structure was observed witha scanning electron microscopy (SEM) for evaluationof processing width. The top and bottom widths ofthe tapered groove were measured by SEM, and thetaper angle was determined by calculation.
Results and discussions
The processing width and taper angle of thetapered groove were observed with different valuesof the three parameters [3]. Figure 2 shows results of
upside and downside widths and taper angle obtained
at varying gaps as a graph. Both processing width
and taper angle increased with increasing gap. A
possible reason for the increased processing width isthat the increased gap caused greater diffraction,
resulting in X-ray exposure of some areas of theresist structure, which were not otherwise X-ray
exposed when the gap was small. If the gap is further
increased, diffracted synchrotron radiation lightbeams may interfere with one another after passage
through slits. The reason for the increases in taper
angle may also be that the increased gap contributed
Dose: 15000 mA*s/mm
Slit width: 7 µm

4

30

3
20
2
10

1

0

0
50

100

Conclusions
Removing a cast from a mold in molding of the
LIGA process, especially in the case of a high aspectratio microstructure, requires an elaborate design.
Otherwise, it is impossible to remove the cast without
breaking the micro structure. The mold releasing
property of a structure improves if the micro
structure has tapered. In this study, high aspect ratio
tapered micro structures were fabricated using the
NewSUBARU BL2 owned by our University for Xray lithography involving diffraction.
Changes in top and bottom widths and taper angleof tapered grooves were measured at varying gaps,
slit widths and dose of X-ray. At an increased dose of
X-ray, processing width increased, while nosignificant changes were observed in taper angle.
Furthermore, it was possible to achieve a taper angleof 3.7 degrees under the conditions of 150 mm gap
between X-ray mask and resist structure, 15,000mAs/mm dose of X-ray and 7 m slit width.
With the taper angle of 2.5 degrees, we havefabricated a Ni mold by electroforming. In future, we
intend to discover necessary conditions for achieving
the target taper angle of 5 degrees, and to study
relationships between tapered shapes and moldrelease property through electroforming and molding
by the LIGA process.

5

Taper angle (degrees)

Processing width (µm)

40

Up side width
Downside width
Tap er angle

to greater diffraction. These results ascertain that the
gap has an influence on diffraction. Next, upside anddownside widths and taper angle of the tapered
groove at varying dose of X-ray was changed under
the conditions of 7 m slit width and 40 mm gap.
Finally, slit widths was changed. These results
suggest that varying the gap between X-ray mask andresist structure and slit width has a substantial effecton controlling taper angle.
We fabricated Ni mold with taper angle of about
2.5 degrees using electroforming. We used a nickel
sulfamate plating bath to transfer the master moldshape by Ni electroforming because of high speed
electroforming with lower electro-deposition stressgeneration. The fabricated Ni mold was about 1 mm
in thickness and 40 mm  45 mm size. Therefore, we
could obtain Ni mold of partially copy the master
pattern.

150

Gap (mm)Fig. 2: Dependence of gap on processing widths
and taper angle

References[1] E. W. Becker, W. Ehrfeld, P. Hagmann, A. Maner
and D. Munchmeyer, Microelecron. Eng., 4, pp.
35-56 (1986).
[2] T. Tanaka, T. Nomura, Y. Funabiki, T. Kitadani, K.
Idei, K. Yamashita, D. Noda and T. Hattori,
Proceedings of the 2006 IEEE International
Symposium on Micro-Nano Mechatronics andHuman Science, Nagoya, Japan, pp. 480-485(2006).
[3] Y. Sawa, K. Tanabiki, D. Noda, and T. Hattori, J.
Solid Mech. Mater. Eng., 3, 5, pp. 721-728 (2009).