Research Activities

Observation of Smith-Purcell radiation in Terahertz
regime at electron linear accelerator LEENA
S.Hashimoto, S. Chin, K. Kawata, Y. Minagawa#, Y. Takemura#, D. Li*, S. Amano, S. Miyamoto
LASTI, University of Hyogo
#
JASRI
*
Institute for Laser Technology
Abstract
Terahertz radiation by the Smith-Purcell effect was successfully observed using 15 MeV electron
beams of the linear accelerator LEENA. The radiation properties such as the angular dependenceof peak wavelength were measured. Wavelength spectrum measured by the Martin-Puplettinterferometer is very clear and the peak wavelength well corresponds to the calculated one.
Introduction
In order to develop high peak power, wide range (0.1-10 THz) and tunable terahertz radiation sources
using relativistic electron beams, we have been upgrading the compact electron linear accelerator LEENA[1-5]. The electron beams with bunch length shorter than the wavelength of emitted light can generate highpower radiation by coherent radiation. The main parameters of LEENA are shown in Table. I. In addition
to the synchrotron radiation from a bending magnet, the Smith-Purcell radiation from a metal grating platenear an electron orbit was successfully observed. The spectrum of Smith-Purcell radiation was measured
with the Martin-Puplett interferometer. In this paper we report the present status of the Smith-Purcell
radiation in a terahertz regime.
Table I

Fig.1 Observation of Terahertz radiation using
LEENA electron beams; synchrotron radiation andSmith-Purcell radiation.

Main parameters of LEENA.

Beam energy
Macropulse current
Macropulse width
Repetition frequency
Gun
CathodeBunch length

6-15 [MeV]
100 [mA]
5 [us]
10 [Hz]RF gunLaB6 (thermal)~30 [ps]

Experimental results of Smith-Purcell radiation
The copper plate with grating period of 10 mm is equipped in a vacuum chamber of the LEENA. Using
three mirrors located in the chamber, terahertz radiation can be extracted into the air through a quartz
viewport. The Smith-Purcell radiation in a terahertz regime was measured with a Zero Bias Detector.
Measured radiation power is about ten micro Watt. Because present bunch length is longer than terahertz
wavelength, the measured radiation is incoherent.
The emitted wavelength of Smith-Purcell
radiation has an angular dependence, i.e., shorter
wavelength light is radiated in the forward direction
and longer wavelength in the backward direction.
The mirrors in the chamber can rotate according to
the desired angle for measurement. Fig. 2 shows
the angular dependence of radiation power
measured by the two detectors with different
measurement ranges.
The calculated emission
angle for the light of 0.075-0.11 THz is about 40
Fig.2 Observation of angular distribution ofdegrees and for 0.11-0.17 about THz 50 degrees.
Smith-Purcell radiation power.
Two detectors
Experimental results show a good agreement to thewith different measurement ranges are used:
calculation.
0.11-0.17 THz (upper) and 0.075-0.11 THz (lower).

Smith-Purcell radiation spectrum measured by Martin-Puplett interferometer
In a terahertz regime, the wire grid reflects theradiation component whose direction of thepolarization plane is parallel to the wire andtransmits the perpendicular component.
The
Martin-Puplett interferometer uses wire grids as adivider of terahertz light as shown in Fig. 3. Theinterferogram made from a path length difference
between two lights by moving a mirror wasmeasured with a ZBD. By the Fourier transformof this interferogram data, the wavelength
spectrum of Smith-Purcell light is obtained asshown in Fig.4. Measured peak wavelength ofSmith-Purcell light is 3.4 mm and is wellcorresponding to the calculations.

Fig.3 Martin-Puplett InterferometerFig.4 Interferogram of Smith-Purcell radiation measured with Martin-Puplett interferometer (left)
and its FFT result (right).

Summary and Future plan
The Smith-Purcell light was successfully observed at LEENA accelerator. The observed terahertz
radiation is incoherent, that is the electron bunch length is longer than the light wavelength. If the bunch
length becomes shorter than the light wavelength, coherent radiation occurs and radiation intensity becomesseveral orders higher. To make electron bunch shorter using an alpha magnet effectively, new solenoid coilis under construction just after the electron gun to suppress beam divergence. The emission angle ofcoherent Smith-Purcell (CSP) radiation depends on the electron bunch length. Thus CSP is not only apowerful terahertz light source but also a useful beam monitor for electron bunch length in linear
accelerators.
And the construction of new terahertz beam-line for user experiments will be started in the summer of2013.
References[1] S.Hashimoto et al., Lasti Annual Report, 12, pp.13-14 (2010).
[2] S.Hashimoto et al., Lasti Annual Report, 13, pp.11-12 (2011).
[3] S.Hashimoto et al., The 8th Annual Meeting of Particle Accelerator Society in Japan (2011).
[4] S.Hashimoto et al., The 9th Annual Meeting of Particle Accelerator Society in Japan (2012).
[5] S.Chin et al., The 9th Annual Meeting of Particle Accelerator Society in Japan (2012).

Energy calibration of electron beams by laser Comptonscattering γ-rays at BL01
H. Utsunomiya1, T. Shima2, K. Takahisa2, D.-M. Filipescu3, O. Tesileanu3, I. Gheorghe3, H.-T. Nyhus4,
T. Renstrøm4, Y.-W. Lui5, Y. Kitagawa6, S. Amano6, S. Miyamoto6
1Konan Univ., 2Osaka Univ., 3IFIN-HH Romania, 4Univ. Oslo, 5Texas A&M Univ., 6LASTI-UH
Abstract
We have calibrated electron beam energies in a nominal energy range 550 - 974 MeV using laserCompton scattering γ-ray beams at the synchrotron radiation facility NewSUBARU. The γ-ray
beams were produced at energies from 562 keV to 1727 keV and detected with a high-purity
germanium detector. The electron beam energies were determined by reproducing the full energy
peaks of the γ-ray beams by Monte Carlo simulations with a precision of 0.068% in 1σ.

III.
A.

RESULTS AND DISCUSSIONS

Energy calibration of electron beams

Figure 1 shows results of the energy calibration for(1)
where εL is the energy of a laser photon, mc2 is therest-mass energy of an electron, θ is the scattering
angle of the laser photon with respect to the electron
beam, and γ is the Lorentz factor of the relativistic
electron which is defined by γ =Ee/mc2 with the total
electron energy Ee. For simplicity, the collision

2

3000
2500
2000
1500

γ

Experiments
and Results
B. Linearity in the response of a LaBr3 (Ce)Low-energy
LCS toγ-raydetector
LCSbeams
rays were produced
below 2 MeV with a grating-fixed CO2 laser (wavelength λ=10.59 µm). Electrons were injected from a
LCS
beams werewith a Nd:YVO
linear-ray
accelerator
intoproduced
the NewSUBARU
storage4 laser
ring( =1064
in collisionsof thelaser
photons on
at thenm)
nominalenergy 974
MeV,
decelerated
to elec950
trons
at nominal
714toandandMeV,
and sub- energies
sequently753,
down
550 677
MeVMeVin steps
measured
with
a
LaBr
(Ce)
detector(3.5”
indiameter⇥3of 50 MeV. The LCS γ-ray beams were measured
4.0” in length, BrilLanCe380 89S102/3.5, Saint-Gobain)
with a coaxial (64 mm in diameter × 60 mm inat the count-rate less than 10 Kcps with a bias voltage
length ) high-purity germanium detector (HPGe). The
of +400 V and a shaping time 0.5 µs of a NIM amplienergy of γ-ray spectra was calibrated with thefier module. The -ray energy was determined by Montestandard γ-ray sources, 60Co including the sum peak,
Carlo simulations with the calibrated energy of the elec133Ba, 137Cs, and 152Eu and a natural radioactivity
tron beam as discussed in Sec. IIIB. The linearity in the
40K. The energy calibration was carried out before
response of the LaBr3 (Ce) detector to low-energy rays
and after the measurement of LCSγ-rays. From thewas investigated with the standard -ray sources, 60 Co,
γ-ray spectra, we determined absolute
133 calibrated
Ba, 137 Cs, and 152 Eu and an Am-Be neutron source
values of the electron beam energies by means of
as a 4.4 MeV -ray emitter.
Monte Carlo simulations in a nominal energy (Een)range 550 – 974 MeV.

Figure 1 shows results of the energy calibration
for the HPGe detector carried out before themeasurement of LCS γ-ray beam. The best linear fit
to the data gives a relation between the γ-ray energy
Eγ in keV and the channel number X by Eγ =0.3624X-0.8022. The data taken after the LCS γ-ray
measurement gives the same slope coefficient and anintercept -0.7458. The uncertainty of the energy
calibration is 0.08% in 1σ in the energy range 120
keV – 2.5 MeV. The electron beam energy wasdetermined by Monte Carlo simulations that best
reproduce the experimental γ-ray spectra measured
with the HPGe detector. The simulation code
incorporates the production process of γ rays in the
inverse Compton scattering into the EGS4 code [4]which simulates interactions of photons with thedetector material.
The energy of the LCS γ rays is given byE [keV]

Introduction
In the NewSUBARU, electrons are injected froma linear accelerator into a storage ring and undergo a
top-up operation at the nominal energy 974 MeV. The
storage electrons can be either accelerated up to 1.5
GeV or decelerated down to 0.5 GeV. Recently, a
new γ-ray experimental hutch, GACKO (Gamma
Collaboration Hutch of Konan University), was built
at NewSUBARU-BL01 and has become fully
operational. Quasi-monochromatic γ-ray beams canbe produced in the energy range 1 - 76 MeV by thelaser Compton scattering. The capability of tuning
the electron beam energy between 0.5 GeV and 1.5
GeV is important to nuclear physicists who use thelaser Compton scattering (LCS) γ-ray beams [1, 2].
However, the nominal energy of electrons isdetermined only with 1% uncertainty based on the
beam optics of the storage ring [3].
We calibrated the electron beam energy by
producing low-energy LCS γ-ray beams with a CO2
laser, where γ-ray energies are in the range of thestandard γ-ray sources. This report presents theenergy calibration for electron beams stored in astorage ring NewSUBARU at nominal energies
between 550 MeV and 974 MeV. The absolutecalibration of the electron beam offers an opportunity
to calibrate the energy of LCS γ-ray beams.

1000
500
0

0

1000 2000 3000 4000 5000 6000 7000 8000
Channel Number

FIG. 1. Energy calibration of the HPGe detector withthe standard γ-ray sources. The solid line is the best

FIG. 1. (Color online) Energy calibration of the HPGe delinear fit to the data.
tector with the standard -ray sources. The solid line is thebest linear fit to the data.

that emits rays inside a solid angle subtended by a 2
mm (in diameter) collimator made of 10 cm thick Pb.
We introduce an e↵ective source size in circular shape.

3

400

CountsCountsCountsCountsΔ
Δ

CountsCountsCountsCountsΔ

Countsbetween laser photons and electrons is assumed to
14
take place at a point where the (a)electron beam forms a
300
narrow waist in the beam optics. The collision point
12with a maximum collision efficiency is located at a200distance of 887cm for the CO2 laser (λ=10.59 µm)
10photons from a collimator and at 1847 cm for the
100Nd:YVO4 laser (λ=1064 nm) photons [2]. The
8electron beam size, which is smaller than the photon
0beam size at the collision point, determines the size
1600
1650
1700
1750
of a light sourcethat emits
γ rays inside
a solid angle
6
E [keV]
500
600
700
800
900
1000
subtended by a 2γ mm (in diameter) collimator made500
NominalEnergy[MeV]of 10 cm thick Pb. We introduce an effective source
electron beam spot is
FIG. 3. The difference ∆E of the real energy Eer from400size in circular shape. The (b)circular at the collision point for 10.59 µm photons of
the nominal energy Een of the electron beams: ∆E = EerFIG. 3. (Color
online) The di↵erence E of the real energy
Een. The solid line is the 4th-orderpolynomial fit to the300the CO2 laser but is elliptic for 1064 nm photons of r
Ee fromthenominalenergy Een of the electron beams: E
data.
See
text
for
details.
the Nd:YVO4 laser [2].
= Eer - Een . The solid line is the 4th-order polynomial fit to200
Monte Carlo simulations were carried out to the data.
Seeassociatedtext for details.
energywith the simulation was 0.1%.
reproducetheexperimental
γ-ray
spectrawith
two
Together
with
the
0.08%
uncertainty arising from the100
fitting parameters, the effective source size (ζ) andenergy calibration, the γ-ray energy was determined
gives 0.128% uncertainty, which corresponds to0the electron beam energy. It is to be noted that the data with
1200
1250
1300
1350
energy resolutionof the
HPGe detector
was taken
0.064%
uncertainty in electron beam energy.
E [keV]
into account as anγ energy spread of the electron beam
Figure 3 shows ∆E= Ener 4– Een, the difference
of
10
n 3
8000in the Monte Carlo simulations. The energy
r
E
=
4.695
⇥
10
(E
) +
1.302 ⇥beams
10 6 (Ethe real energy Ee of etheelectronthuse)3
n from theresolutionofthe HPGe detector
determined
simulation
12.5
1.360by⇥ the
10 Monte(Een )2Carlo+ 0.6385(E103.94. (2)(c) was 6.7 keV (0.5%)e)
6000in full width at half maximum (FWHM) for 1332
nominal energy Een as a function of Een. The 4thpolynomial
to the in
data
gives
keV γ rays (60Co). Following the relation (∆Eγ/Eγ) ≈ Here order
E and
Een arefitgiven
MeV.
40002(∆Ee/Ee) based on Eq. (1), the detector resolution An attempt was made of experimentally detecting then 3∆E threshold= −4.695 × for
10−10(Eenlocated)4 + 1.302
10−6(EMeVe )was incorporated into the simulation as (∆Ee /Ee ) ≈ neutronAu
at× 8.072[5]. A−3(E n)2 + 0.6385(E n) − 103.94−1.360×10(2)ee
20000.1% in the standard deviation of Gaussian function. disk of 2mm-thick Au was irradiated with the LCS -ray
Examples of the best fits to the spectra are shown in beams
produced
the Nd:YVO4 laser at the nominalnHere∆E and Ewith
e are given in MeV.
energies
fromof677
to 661 in stepsof 32 MeV.
0Fig. 2. The full energy peaks were well reproduced electron-beam
An attempt was madeexperimentally
detecting
3540
550 Carlo simulations
560
570 the effective By changing the electron-beam energy by 2 MeV,by the Montewiththe neutron threshold for Au located at 8.072 MeV weE[keV]
source size ζ=0.9γ – 1.1 mm. The uncertainty in γ-ray changed
thedisk-ray
energy by Au
⇠ 50
keV.
Neutrons[5]. Aof 2mm-thickwasirradiatedwithwere
the detectedwitha 4⇡beams
triple-ringneutrondetector[6].4 laser
StatistiLCS
γ-ray
producedwiththe
Nd:YVO
400
400
14
14 events
the nominal
electron-beamenergiesfromto folcally atsignificant
were observed
above
667677
MeV
FIG. 2. (Color online) 300(a) Monte Carlo simulation(dotted
(a)
661
in
steps
of 2 MeV.
Bythreechanging
theenergies,
electron- 665,
(a)
lowed
by
no
net
countsatthelowestr300line) with an electron beam energy Ee =982.2 MeV for LCS
12
12 byIn
beam661
energy2 MeV,
wethe
changedthe γ-rayenergy-rays
663, andMeV.
view offact that
the LCS-ray spectra produced with
a
CO
laser
in
comparison
with
2
200
by
∼
50
keV.
Neutrons
weredetected
witha4π
200 line) taken at the nominal energy
at the thresholdenergy for Au are produced tripleby 676.52
the experimental data (solid
10
10
ring
neutrondetector[6].energy
StatisticallysignificantnMeVelectrons,
thenominal
of
667
(665)
MeV is,
Ee =974 MeV. (b) The same
as
(a),
but
for
a
simulation
with100
eventslarger
were observed
above
667
MeVMeV.
followedby it
100
in reality,(smaller)
than
676.52
Namely,Eer =860.7 MeV in comparison
with the data at Een =850 MeV.
8nonet
countsatthethreelowestenergies,
665,
663,
8
r
(c) The same as (a), but for
turned out that the di↵erence between the real and nom0 a simulation with Ee =559.6 MeV
0
and 661 MeV. In view of the fact that the LCS γ-rays
n1650
1600
1700The result
1750 ofin comparison with the data
=550 MeV.
inal energies
is6 larger energy(smaller)than
9.52produced(11.52) MeV
1600 at Ee 1650
1700
1750
at the thresholdfor
Au 900areby at
E [keV]
6500
600
700 (665)
800 MeV.
1000 present cali[keV]
a reproducibility test is also shown byEγtheopen circles afterthenominalenergy
of
667
The
500
600
700
800
900
1000
γ
676.52 MeV electrons,
the nominal
Nominal Energy[MeV] energy of 667
multiplied by a factor of500
12.5. See text for details.
500
NominalEnergy[MeV]
brationgives
thedi↵erenceof 10.44
MeV (10.43
MeV) at
(665)
MeV
is,
in
reality,larger(smaller)
than 676.52
(b)
400
(b)
the nominal
energy667of(665)
MeV. Thus, detection
the result of
400
MeV. Thus,
the ofresultthe experimental(Coloronline)The di↵erenceof the realthresholdenergythe for
theFIG.
experimental
detectionofAutheisEEneutron
of 3.
the
neutronthresholdfor
consistentFIG.
3. (Color
online)The di↵erenceof the real withenergy300
Eerr from the nominal energy Eenn of the electron beams: E
300
E
from
the
nominalenergyEoftheelectronbeams:
E
In this measurement, use was made of a Pb collimatorcalibration.
Au=isepresent
consistentwith
thepresent
energycalibration.
ern energy
Eer - Een. The solid line is the 4th-order polynomial fit to
200
=
E
E
.
The
solid
line
is
the
4th-order
polynomial
fit
to
e
e
200
of 3 mm diameter insteadof 2 mm and a di↵erent gain
the data. See text for details.
the data. See text for details.
Referencesof 0.8485 keV/channel.100
As
shown
by
the
open
circlesin100[1] S.
et al., Nucl.
Meth.
A 602, 337 (2009).
B.AmanoLinearityof Instr.
a LaBrFig. 2(c), it turned out 0that the high-energy edge of the
3 (Ce) detectordata[2] gives
K. Horikawa, S. Miyamoto, S. Amano, and T.
data
gives
0
1200
1350
full energy peak (therefore,
the1250
electron1300
beam energy)
1200
1250
1300
1350
Mochizuki, Nucl. Instr. Meth. A 618, 209(2010).
E [keV]is reproduced with excellent precision
although the peakEγ [keV]Using
realelectronbeamenergies
determinedby[3] A.theAndoet al.,
J. SynchrotronRad.
5, 342 (1998).
γ
10
n 4
6
n 3
8000
E
=
4.695
⇥
10
+
1.302
⇥
10
10(Een) 4and
6(E
en))3
became broaderFIG.
due2.tothelargercollimator.
[4]
W.R.
Nelson,H.
Hirayama
W.O.
Roger,
”The
8000
the
formula
given
in
Eq.
(2),
we
performed
Monte
Carlo
E
=
4.695
⇥
10
(E
)
+
1.302
⇥
10
(E
e
(a) Monte Carlo simulation (dotted line) with
3n 2en
 12.5n
EGS41.360
Code
Systems”,
SLAC-Report-265⇥)) (1985).
103.94.
(c) for3(Een-rayr di↵erence
for
the
LCS
spectraeenproducedwith theFigure 3 shows
E6000= beamEer –energy
E12.5
the
of LCSthe γ- simulations
an electron
MeV
1.360
⇥ 10
10
(Ee ))2 ++ 0.6385(E0.6385(E103.94. (2)(2)
e =982.2(c)e, E[5] G. Audi, A.H. Wapstra and C. Thibault, Nucl. Phys. A
6000produced with a CO2 laser in comparison
spectraNd:YVOlaser
andmeasured
with
the
LaBr
(Ce)
detecreal energy Eer rayof theelectronbeams thus determined byn
4E and3
Here 729,
337 E(2003).
E andEeen areare givengiven inin MeV.
MeV.
withthe experimental
datanominal(solid line)
taken Eat nthe tor.Here
The
energyresolution
of
the
LaBr
(Ce)
detectorwasthe Monte Carlosimulationfromtheenergy4000
Anattempt
was
madeofexperimentally
detectingthe
3 Rev. C 79,[6]Makinaga,
Utsunomiya
et al., Phys.
4000
AnA.
attempt
was H.
madeof experimentally
detecting thenominalenergy Een=974 MeV. (b) The same as (a),ebut
neutronthresholdfor
Au
located
at
8.072
MeV
[5].
A
incorporatedinthesimulationasanenergyspreadoftheas a function offor
Eena .simulation
The 4th-orderpolynomial
fit
to
the
025801(2009).
neutron threshold for Au located at 8.072 MeV [5]. A
with Eer =860.7 MeV in comparison
2000
with the 2000
data at Een =850 MeV.
0
0540
540

550
550

E [keV]Eγ [keV]

560
560

570
570

γ

FIG. 2. (Color online) (a) Monte Carlo simulation (dotted
FIG. 2. (Color online) (a) Monte Carlo simulation (dottedline) with an electron beam energy Eerr=982.2 MeV for LCS

disk
disk ofof 2mm-thick
2mm-thick Au
Au waswas irradiatedirradiated with
with thethe LCS
LCS -ray-ray
beams
producedwiththe
Nd:YVO
laser
at
the
4
beams produced with the Nd:YVO4 laser at the nominal
nominalelectron-beamenergies
from
677
to
661
in
steps
of
2
MeV.
electron-beam energies from 677 to 661 in steps of 2 MeV.
By
By changing
changing thethe electron-beamelectron-beam energy
energy by
by 22 MeV,
MeV, we
wechangedthe-rayenergyby⇠
50
keV.
Neutronschanged the -ray energy by ⇠ 50 keV. Neutrons were
were dedetected
tected with
with aa 4⇡4⇡ triple-ring
triple-ring neutron
neutron detector
detector [6].
[6]. StatistiStatisticallysignificant
eventswere
observed
above
667
cally significant events were observed above 667 MeV
MeV folfollowed
lowed byby nono netnet counts
counts at
at thethe three
three lowest
lowest energies,
energies, 665,
665,

NEXAFS Study on Hyperthermal Atomic Oxygen Beam
Irradiation Effect on the Ti-containing DLC Film
Kazuhiro KANDA1, Kengo KIDENA1, Kazuhiro FUKUDA1, Ryo IMAI1, Masahito NIIBE1,
Synya FUJIMOTO2, Kumiko YOKOTA2, Masahito TAGAWA2
1
Laboratory of Advanced Science and Technology for Industry, University of Hyogo, Japan,
2
Faculty of Engineering, Kobe University, Japan
Abstract
Surface structural changes of Ti-doped diamond-like carbon (Ti-DLC) film exposed to a hyperthermal atomic
oxygen beam were investigated using near-edge X-ray absorption fine structure (NEXAFS) spectroscopy usingsynchrotron radiation. The spectral shape of the C K NEXAFS spectrum of as-deposited Ti-DLC film resembled
that of DLC film. After exposure to atomic oxygen, the spectrum resembled that of TiC powder. On the other
hand, the spectral shape in the Ti L NEXAFS spectrum of as-deposited Ti-DLC film resembled that of TiC
powder and became similar to that of TiO2 powder after exposure to atomic oxygen. These changes are
ascribable to the desorption of C atoms as CO and/or CO2 from Ti-DLC film due to the irradiation of atomic
oxygen beam.
Introduction
Diamond-like carbon (DLC) films were expected to be used as lubrication materials in space, where oil
cannot be used, because they exhibit excellent friction properties both in a vacuum and in air. One of the mostimportant concerns is the reliability of DLC films as a lubricating material in an extreme space environment(temperature, soft X-ray, radiation of atomic oxygen, and their synergistic conditions). The most important factor
in causing deterioration of the material in low Earth orbit (LEO), where artificial satellites and spacecraft are
positioned, is atomic oxygen exposure. In this orbit, artificial satellites and spacecraft are exposed to atomic
oxygen with a translation energy of 5 eV. In our previous study, we investigated the effects of atomic oxygen
exposure with an impinging energy of 5 eV on the surface chemistry and structure of DLC film surfaces by using
an atomic oxygen beam source [1]. A departure of hydrogen from DLC films and structural change of carbon
atom in the surface layer of a hydrogenated DLC film were verified during hyperthermal atomic oxygen
exposure.
Recently, the development of functional DLC films advanced due to the incorporation of other elements,
such as N, Si, F, and metal content, into DLC films to enhance their electrical, optical, and mechanical properties.
In particular, Ti-doped DLC films have been widely investigated due to their thermal stability. In the present
study, we investigated the effect of atomic oxygen exposure with an impinging energy of 5 eV on the surface
chemistry and structure of Ti-DLC films by measuring the near-edge X-ray absorption fine structure (NEXAFS)
spectra.
Experimental methods
The Ti-containing hydrogenated DLC (Ti-DLC) films used in this study are commercially available. The
films were deposited at 200 nm thickness on Si wafers by using an amplitude modulated RF plasma-enhanced
chemical vapor deposition (CVD) method. The hydrogen content of these films were estimated to be greater than
40 at.% using the combination of Rutherford backscattering spectrometry (RBS) and elastic recoil detection
analysis (ERDA) of DLC films by using the same synthesis method.
The exposure of an atomic oxygen beam into the Ti-DLC films was done using a laser detonation-type
beam apparatus located at the Kobe Univ. The translational energy of atomic oxygen was estimated to be 5.46
eV by using a time-of-flight (TOF) measurement system consisting of a quadrupole mass spectrometer with ascintillation detector and a multichannel scalar. The typical atomic oxygen flux at the sample position (46 cm
from the nozzle) was estimated to be 3.51×1015 atoms cmí2 sí1 by using a Ag-coated quartz crystal microbalance(QCM). In the present study, four sheets of Ti-DLC film were exposed to an atomic oxygen beam corresponding
to the fluences of 2.74×1019, 5.47×1019, 8.3×1019, and 1.85×1020 atoms cmí2, respectively. All exposure
experiments were carried out at room temperature.
The NEXAFS measurements were carried out on beamline 09A (BL09A). Undulator light dispersed by ainvalid spacing planer-grating monochromator was irradiated on the sample film at 54.7° (magic angle) withrespect to the surface normal of the samples. The NEXAFS spectra were measured in the total electron yieldmode. The measured energy range of the C K edge absorption and Ti L edge absorption were 275330 eV and
450500 eV, respectively.

Results and Discussion
Figure 1 shows the C K-edge NEXAFS spectra of a Ti-DLC film exposed to by an atomic oxygen beam withthat of a Ti-DLC film before exposure. The spectral features of the C K NEXAFS spectrum of the Ti-DLC film
before exposure resembled that of the DLC film. By the exposure to an atomic oxygen beam, the spectralfeatures of the C K NEXAFS spectrum of the Ti-DLC film noticeably changed. 1) A sharp peak was observed at
289 eV due to the increase in intensity at which a peak was observed as a small shoulder peak in the spectrum of
the Ti-DLC film before exposure. 2) The intensity of the peak at 285.4 eV decreased. This decrease indicates thatthe sp2 component decreased in the Ti-DLC film. The spectral features of the Ti-DLC film after exposure toatomic oxygen beam resembled that of TiC powder. In addition, the peak at 289 eV was assignable to the 1sĺı*transition originating from the C atoms neighboring the Ti atoms.
Figure 2 shows the Ti L-edge NEXAFS spectra of the Ti-DLC exposed to an atomic oxygen beam with that of
the Ti-DLC film before exposure. The spectral features of the Ti L NEXAFS spectrum of the Ti-DLC film before
exposure resembled that of TiC powder. After exposure to an atomic oxygen beam, the spectral features of the
Ti-DLC films changed and became similar to those of TiO2 powder.
From these results, the changes in the local structure of the Ti-DLC film due to exposure to an atomic oxygen
beam are summarized as follows: 1) In the as-deposited Ti-DLC films, almost all the C atoms were bonded toeach other with single bonding and double bonding at a certain ratio. Most of the Ti atoms bonded to the C atoms.
2) After exposure to an atomic oxygen beam, most of the C atoms bonded to Ti atoms and most of the Ti atoms
bonded to the O atoms. These changes are ascribable to the desorption of C atoms from Ti-DLC films due to theirradiation of the atomic oxygen beam. The C atoms were desorbed from the films as gas species (CO and/or
CO2). On the other hand, oxidized Ti (TiOx) was not desorbed from the Ti-DLC films as a gas species. Therefore,
the Ti/C ratio on the surface of the Ti-DLC films increased due to the irradiation of the atomic oxygen beam. As
the result, residual C atoms bonded to the Ti atoms. The sp2/(sp2+sp3) ratio of C atoms in the Ti-DLC films
exponentially decreased because the C-Ti bonding could not form double bonding. The discrepancy a theprevious work on DLC film [1] is ascribable to Ti-DLC films containing Ti atoms, which were not desorbed
from the film even if they were oxidized due to the irradiation of an atomic oxygen beam.

ǻ*TiC
1.851020

atoms/cm

8.310 19 atoms/cm 25.4710

19

TiO2

2

atoms/cm 22.741019 atoms/cm 20 atoms/cm 21918.510 atoms/cm

Normalized absorption [a.u.]

Normalized absorption [a.u.]

Ǹ*

2

19

8.310 atoms/cm 25.471019atoms/cm 2192.7410 atoms/cm

20 atoms/cm 2

DLC

TiC
270 280 290 300 310 320 330 340
Photon energy [eV]Fig.1 C K-edge NEXAFS spectra of commercial
DLC film and Ti-DLC films before and after
exposure to atomic oxygen beam and TiC powder

450

460

470
480
490
Photon energy [eV]500

Fig.2 Ti L-edge NEXAFS spectra of TiC powder,
Ti-DLC films before and after exposure to atomic
oxygen, and TiO2 powder.

References
1) K. Yokota, M. Tagawa, A. Kitamura, K. Matsumoto, A. Yoshigoe, Y. Teraoka, Appl. Surf. Sci. 255 (2009)6710.
2) M. Tagawa, K. Yokota, A. Kitamura, K. Matsumoto, A. Yoshigoe, Y. Teraoka, K. Kanda, M. Niibe, Applied
Surface Science 256 (2010) 7678-7683.

Soft X-ray Irradiation Effect on Highly HydrogenatedDiamond-like Carbon Films
1

Ryo IMAI1, Makoto OKADA1, Shinji MATSUI1, Tsuneo SUZUKI2, Kazuhiro KANDA1
Laboratory of Advanced Science and Technology for Industry, University of Hyogo, Japan,
2
Enegy-Density Research Institute, Nagaoka University of Technology, Japan

Abstract
Surface and bulk properties’   changes   of   a   hydrogenated   Diamond-like carbon (H-DLC) film
exposed to synchrotron radiation (SR) in the soft X-ray region were investigated by an atomic
force microscope (AFM) and a combination of Rutherford Backscattering Spectroscopy (RBS) andElastic Recoil Detection Analysis (ERDA) techniques. The surface of H-DLC films became flatand the hydrogen content of H-DLC films decreased with increasing SR dose.
Introduction
Diamond-like carbon (DLC) films have excellent properties including high hardness, a low friction
coefficient, high abrasion quality, a gas barrier, chemical inertness, and surface lubrication and are therefore
being utilized as coating materials on automobile parts, hard disks, artificial blood vessels, edged tools, andfood containers. Film-forming methods affect the properties of DLC films differently, and thus a wide varietyof DLC films have been developed. DLC films are expected to be used in outer space as a lubrication
substitution for oil, which cannot be used in space because it disappears in vacuums [1-2].
DLC films are generally known to be durable against X-ray exposure [3]. However, it has recently beenreported that soft X-ray exposure on highly hydrogenated DLC (H-DLC) films leads to desorption ofhydrogen and an increase in film density and refractive index [4-5]. A theoretical calculation has suggested
that this hydrogen desorption could be associated with a structural change of DLC films [6]. Clarification of
the effect of soft X-ray exposure on DLC films is necessary to ensure that DLC films can be used in outerspace safely.
In this study, we investigated the modification processes by soft X-ray exposure on H-DLC films.
Specifically the SR dose dependence of surface roughness (Ra), and hydrogen content was investigated. The
elementary composition analysis was performed using a combination of Rutherford Backscattering
Spectroscopy (RBS) and Elastic Recoil Detection Analysis (ERDA) techniques. The surface roughness wasmeasured using an atomic force microscope (AFM).
Experiments
200-nm-thick H-DLC films were deposited on Si wafers by using an amplitude-modulated RF
plasma-enhanced CVD method. This method enables the deposition of DLC films containing a lot ofhydrogen. The SR irradiation of the H-DLC films was carried out at BL06 of the NewSUBARU synchrotron
facility at the University of Hyogo, Japan. The SR at the BL06 sample stage had a continuous spectrum fromIR to soft X-rays, lower than 1 keV. This includes 300 eV, which is the ionization energy of a carbon K edge.
As a result, the K-shell electrons of the C atoms could be excited by the SR at BL06. During this experiment,
the electron energy of the NewSUBARU ring was 1.0 GeV. The BL06 sample stage was room temperatureand the pressure in the chamber was the order of 10-5 Pa. An SR dose [mA･h] is derived from the product of
the ring current [mA] and exposure time [h]. The exposure on the H-DLC films was carried out over SR
doses ranging from 0 to 3000 mA･h.
Results and discussion
The hydrogen content of H-DLC films was quantitatively determined by RBS/ERDA. The measurements
were performed using an electrostatic accelerator (Nissin High Voltage, NT-1700HS) located at the Extreme
Energy-Density Research Institute, Nagaoka University of Technology, Japan. He + ions accelerated to 2.5
MeV using a tandem Pelletron accelerator were used as the incident beam, whose angle with respect to thesurface normal was 72q. The measurement error of this apparatus is 1%.
Figure 1 shows the SR dose dependence of the hydrogen content of H-DLC films. The hydrogen content
of the unirradiated H-DLC films was |50 %. After SR exposure, the hydrogen content drastically decreasedin the range of 0200 mA･h, eventually becoming |30 % at 200 mA･h. Above |200 mA･h, the hydrogencontent slowly decreased and consequently became |20 %. This result shows that the SR exposure on
H-DLC films leads to hydrogen desorption. However, hydrogen of |20% in H-DLC films had no influence
due to SR exposure. This indicates that hydrogen atoms exist at different chemical environments in H-DLC
films: where hydrogen emitted or not emitted from films by the exposure to soft X-rays. It has previously
been found that the structure of H-DLC films varied to that of typical DLC films whose hydrogen content is2030 % by the exposure to soft X-rays [5].
The surface roughness of the H-DLC films were measured by using a tapping method with AFM
apparatus (SII nanotechnology E-sweep/nanoNavi Station); the determining area was 1000 × 1000 nm. SR
dose dependence of Ra estimated by the measurements of AFM, are shown in Fig. 2. The Ra of theunirradiated H-DLC films was 0.29 nm, which was the largest. The Ra of H-DLC films with even smallest
SR dose (10 mA・h) rapidly decreased compared to the unirradiated one. In addition, Ra remained
approximately constant at |0.18 nm in regions above |100 mA･h. These results show that SR exposure on
H-DLC films led to a decrease of Ra, and it also flattened the surface of the H-DLC films. In terms of thehydrogen content, the change was observed in |0200 mA･h. In contrast, the process of flattening decreased
at a lower SR dose. Therefore, the process of surface flattening differs from that of hydrogen desorption.
The modification of H-DLC films by the SR exposure includes hydrogen desorption and surface
flattening. Immediately after the SR exposure, the surface becomes flat due to desorption from the salient. Up
to |200 mA･h, the hydrogen content of the H-DLC films was |30 %.

0.5
0.4

40
Ra [nm]H/(C+H) [%]

50

30
20

0.2
0.1

10
0

0.3

0

0

1000
2000
SR dose [mA・h]

3000

Fig. 1. SR dose dependence of hydrogencontent of H-DLC films.
◯ and ● represent unirradiated andirradiated, respectively.

0

1000
2000
SR dose [mA・h]

3000

Fig. 2. SR dose dependence of surface
roughness of H-DLC films.
◯ and ● represent unirradiated andirradiated, respectively.

Conclusions
Soft X-ray irradiation effect on the surface and material properties of highly hydrogenated Diamond-likecarbon thin films was investigated using an atomic force microscope (AFM) and a combination of Rutherford
Backscattering Spectroscopy (RBS) and Elastic Recoil Detection Analysis (ERDA) techniques. The
hydrogen content of H-DLC films decreased from |50 % to |20 % by the SR exposure on films. Hydrogen
desorption was not observed at higher doses. In the range of |0200 mA･h, hydrogen content decreased. In
contrast, the surface roughness (Ra) of the H-DLC films decreased at lower SR doses compared withhydrogen content, and the surface of the H-DLC films became flat. We found that the modification processesof H-DLC films by SR exposure include hydrogen desorption and flattening on the surface.

References[1] C. Donnet et al., Tribology of Diamond-like Carbon, Springer (2008).
[2] C. Donnet et al., Surf. Coat. Technol. 68-69 (1994) 626.
[3] H. Kyuragi et al., Appl. Phys. Lett. 50 (1987) 1254.
[4] K. Kanda et al., Jpn. J. Appl. Phys. 50 (2011) 055801.
[5] H. Matsuura et al., SEI Tech. Rev. 171 (2007) 36 [in Japanese][6] Y. Miura et al., J. Appl. Phys. 93 (2003) 3395.

Low-Temperature Activation of Boron in Si wafer
by Soft X-ray Irradiation
Akira Heya1, Takuto Fukuoka1, Naoto Matsuo1, Kazuhiro Kanda2, and Takashi Noguchi3
1

University of Hyogo, 2167 Shosha, Himeji, Hyogo 671-2280, Japan
Phone: +81-79-267-4909 E-mail: heya@eng.u-hyogo.ac.jp
2
LASTI, University of Hyogo, 3-1-2 Koto, Kamigori, Hyogo 678-1205, Japan
3
University of the Ryukyus 1, Senbaru, Nishihara, Okinawa, 903-0213, Japan
Abstract
Novel activation method of B dopant using a soft X-ray undulator was investigated. The activationenergy of B activation by soft X-ray irradiation was lower than that of B activation by anannealing. As the irradiated photon energy closed with the core level of Si 2p, the activation ratio
increased. This related to the enhancement of electron excitation as a base on Felmi golden rule. At
low temperature, the B activation occurred by the atomic migration of Si atoms due to Coulomb
force via the electron excitation.
Introduction
Fabrication method of an ultra-shallow junction lower than 10 nm is required. We proposed a novel
activation method of B dopant at low temperature by using a soft X-ray undulator [1]. The photon energy
dependence of sheet resistance was investigated. In addition, the mechanism of soft X-ray activation was
discussed in comparison with a conventional thermal activation.
Exprimental
B ions were implanted to Si (100) wafer (n-type, 8-12  Ωcm)  with  an  energy  of  5  keV  and  a  dose  quantity  of  2×1015 cm-2. The irradiation of soft X-ray was carried out at BL07A of NewSUBARU[1]. The photon energy
was changed from 50 to 250 eV, with the dose quantity of 50 mA h. In addition, to reduce the sample
temperature, the storage-ring current decreased from 250 to 50 mA. The gas pressure during irradiation was
6×10-5 Pa. The surface temperature of Si substrate during soft X-ray irradiation was measured by thermocouple
and via a ZnSe window by a thermo-viewer. For the comparison, the annealing in N2 atmosphere was carried out
in the range of 100 to 1000qC.
The sheet resistance was measured by a four-point probe method at room temperature. The activation ratio
is given by Irvin curve and dopant dose quantity. Activation energy of B activation (Ea) was estimated by
Arrhenius plot of activation ratio.
Results and discussion
The sheet resistance and the temperature of Si wafer as a function of photon energy are shown in Fig. 1. The
temperature at the photon energy of 100 eV, which corresponds to the energy level of Si 2p core-electron (99.8eV), shows the highest value. The Si 2p core-electrons of Si atom are excited by soft X-ray irradiation and theyrelax resulting in a temperature increase of Si wafer. The activation was enhanced at 100 eV. According toFelumi golden role, the electron excitation is enhanced by closing to energy of core level. It is found that the
sheet resistance after soft X-ray irradiation strongly depended on the irradiated photon energy.
As the storage ring current decreased, the sample temperature decreased to 110qC and the sheet resistance
was increased to 3.1 kΩ/□  (Fig.  2).  The  sheet  resistance  of  annealed sample at 100qC  was  8.0  kΩ/□.  It  shows  that  the activation was enhanced by the electron excitation during the soft X-ray irradiation.
The relationship between the activation ratio and the reciprocal absolute temperature are shown in Fig. 3. The
sheet resistance of soft X-ray irradiated Si was lower than that of annealed Si below 400qC. The Ea for the soft
X-ray activation was smaller than that for the annealing. The discrepancy of E a between the soft X-ray
irradiation and annealing indicates that the soft X-ray activation occurred by not only the thermal effect but also
the excitation of the core electrons followed by the atomic migration.
The activation mechanism of B by soft X-ray irradiation is considered as follows (Fig. 4). The activation byannealing generally occurs by movement of dopant atoms to lattice sites of Si. This process corresponds to the
Arrhenius plot for thermal annealing in high temperature range. The soft X-ray irradiation enhances the atomic

migration via excitation of Si2p core-electrons of Si. During the recovery of crystallinity in amorphizated Si
surface by atomic migration via electron excitation, B atom can shift to the lattice site of Si atom. Because thesize of B atoms is smaller than that of Si atom, the B activation is influenced by atomic migration of Si such as“knock-on”  effect.
Conclusions
1) The activation of B dopant occurs at 110qC, although the activation ratio shows small value of
6.2×10-3. The B activation ratio of Si wafer subjected to photon with an energy of Si2p and B1s were
1.8×10-2 and 5.7×10-3, respectively. Because the size of B atoms is smaller than that of Si atom, theenhancement of Si migration by soft X-ray irradiation triggers the movement of B atoms.
2) The B activation energy for the soft X-ray irradiation was smaller than that for the annealing. The soft
X-ray activation occurred by not only the thermal effect but also the excitation of the core electrons followedby the atomic migration.
References[1] A. Heya, K. Kanda, K. Toko, T. Sadoh, S. Amano, N. Matsuo, S. Miyamoto, M. Miyao, and T. Mochizuki: Thin Solid
Films 534 (2013) 334.

Fig. 1. Sheet resistance (closed symbol) and temperature of
Si wafer (open symbol) as a function of photon energy ofsoft X-ray. The insert shows the sheet resistance of Si wafer
for the photon energy from 90 to 115eV.

Fig. 2. Sheet resistance and sample temperature as afunction of photon flux density (storage-ring current) at
photon energy of 115 eV. The B activation occurs at 110qC,
although the activation ratio shows small value of 6.2×10-3.

Fig. 3. Relationship between the activation ratio andreciprocal absolute temperature. Activation energy of
B dopant activation was estimated from the slope. The
Ea for the soft X-ray activation (0.06 and 0.09 eV) was
smaller than that for the annealing (0.16 eV).

Fig. 4. Schematic diagram of mechanism of
low-temperature activation by soft X-ray irradiation.
The soft X-ray irradiation enhances the atomic
migration via excitation of Si2p core-electron. During
the recovery of crystallinity in amorphizated Si surface
by the atomic migration via the electron excitation, B
atom can shift to the lattice site of Si atom.

Surface Modification in Silica-Based Films
by Undurator Radiation
K. Moriwaki, S.Takezawa, Graduate School of Eng./ Kobe Univ.,
K.Kanda, and S.Matsui, LASTI/Univ. Hyogo
Abstract
Undulator radiation (UR) by the NewSUBARU is used to modify the surface in pure silica andGeO2-doped silica films for optical waveguide devices. Irradiated films are found to show
reduction for both SiO2 and GeO2 bonds by analyzing XPS (X-ray Photoelectron Spectroscopy)
results. The surface reduction results generating Si-Si bonds show a clear peak-energy-dependenceof UR, in which there is a threshold energy near the L3 absorption-edge for Si. The surface
reduction layer for Si-Si bonds is found to be very thin less than 1.5nm, while that for Ge-Ge
bonds is less than 40nm.
Introduction
We use synchrotron radiation (SR) and undulator radiation (UR) for photo-induced refractive-index
modifications in silica-based glasses for optical waveguide devices1,2). Our main objectives are to induce
large refractive-index changes more effectively using SR or UR without a spectrometer, and to investigate
their origins depending on wavelengths of SR or UR spectra. Especially, UR would be a very useful tool forthe materials modifications, because it can select a useful wavelength and it has very high intensity. For thosereasons we mainly use UR for the materials modifications. In this report, we investigated themodification effects on the surface of SiO2 films or GeO2 doped SiO2 films irradiated with UR.
XPS was mainly used for the characterizations.

Intensity(arb.unit)

Experiments and Results
Experimental conditions are almost the same as in the previous experiments1,2). UR (from the
NewSUBARU BL-7A) was mainly used to investigate irradiation-wavelength effects. SR (from the
NewSUBARU BL6) was also irradiated on samples directly without a spectrometer. The electron energy of
the SR was 1GeV. The UR peak energy in the first order was controlled from 20 to 120 eV. The samples were
thermally grown SiO2 films (0.5 or 1 Pm thickness) on Si substrates and GeO2-doped SiO2 films (2 Pmthickness) fabricated by the FHD (Flame Hydrolysis Deposition) technique on Si substrates in thisexperiments. Relative refractive index difference for the GeO2-doped SiO2 films was 1.9%. XPS
measurements and the following RIE (Reactive Ion Etching) were used to investigate the surface reduction
effects and depth profiles for the modification.
It was shown in Fig.1 that Si-Si bonds weregenerated on the surface of thermally grown SiO2
Si4+
films, after irradiating UR with peak energy values
UR:20eV 1000mAh
UR:60eV 1000mAh
of 20, 60, and 80eV by measuring Si2P peaks in the
UR:80eV 1000mAh
XPS. On the other hand, after irradiating UR with
UR:100eV 1000mAh
UR:120eV 1000mAh
peak energy values of 100 and 120eV, Si-Si bonds
before irradiation
were not generated as shown in Fig.1. It may
suggest that the Si-Si bonds generations are
Si0
influenced by the L absorption at 99.2eV for Si.
The modified layer was very shallow, because thegenerated Si-Si bonds on the surface weredisappeared after etching the sample up to a depthof 1.5 nm as shown in Fig.2. The etched sample in
108 106 104 102 100 98
96
94
92
Fig.2 shows the same SiO2 bond peak without a
Binding
Energy(eV)
Si-Si bond peak as in the original ones. In GeO2
doped SiO2 films irradiated by UR, almost the same
FIG.1. Si2p peaks in the XPS spectra, before andtendency were found for the Si-Si bonds generation.
after irradiating UR with peak energy from 50 to
The depth profile was also the same as that in the
120 eV in pure SiO2 films. Si-Si bonds are
Fig.2
generated for the sample for peak energies less
As for the Ge3d peaks in GeO2 doped SiO2 films
after irradiating UR, the reduction layer with Ge-Ge
than 100eV. The UR dose was 1000mAh.
bonds was also found to be generated especially forIntensity(arb.unit)

Ge4+
O2s
Ge0

40

35

30

25

Intensity(arb.unit)

UR:60eV 1000mAh
UR 1.5nm etching
before irradiation

108

106

104

102

100

98

96

94

92

Binding Energy(eV)FIG.2. Si2p peaks in the XPS spectra, before,
after irradiating UR with a peak energy of 60 eV
and after etching up to a depth of 1.5nm in SiO2
films. The generated Si-Si bonds are
disappeared after the etching as in the
non-irradiated sample. The UR dose was
1000mAh.

UR:50eV 1000mAh
UR:60eV 1000mAh
UR:80eV 1000mAh
UR:100eV 1000mAh
UR:120eV 1000mAh
before irradiation

20

Binding Energy(eV)FIG.3. Ge3d peaks in the XPS spectra, before
and after irradiating UR with a peak energy
from 50 to 120 eV in GeO2 doped SiO2 films.
Ge-Ge bonds are generated for the sample forpeak energies of 50 and 60eV. The peakintensity for the Ge-Ge bonds (Ge0) is gradually
decreased for peak energy from 80 to 120 eV,
The UR dose was 1000mAh.

UR:60eV 1000mAh
UR 10nm etching
UR 20nm etching
UR 30nm etching
UR 40nm etching
before irradiation

Intensity(arb.unit)

low peal-energy such as 50 or 60 eV as shown in
Fig.3. The Ge-Ge peak decreases gradually byincreasing the peak energy of UR. For a sample
irradiated with peak energy of 100 or 120eV, peaks
for Ge-Ge bonds are not seen in Fig.3, but this might
be caused by a weak intensity for the Ge3d peak ascompared to that for Si2p. The threshold energy is notclear for the Ge-Ge bonds generation comparing tothat for the Si-Si bonds, which may be caused by theabsence of clear absorption-edge for Ge around theirradiation energy range. After etching the sample, thereduction layer with Ge-Ge bonds was removed by 40
nm-deep etching. The Ge-Ge bonds layer is generated
deeper than that for the Si-Si bonds layer of 1.5nm,
which may be a cause of a penetration-depth
difference for the effective irradiation wavelength.
The surface reduction effects appeared in Fig.1 waschanged by other samples with different film
thickness. A sample with thinner film with the same
irradiation condition showed more intense peaks for
Si-Si bonds in the XPS. Sample temperature might be
the origin for the thickness dependence, because thesample temperature might be more than a few
hundreds of degrees during the irradiation.

40

35

30

25

20

Binding Energy(eV)FIG.4. Ge3d peaks in the XPS spectra, before,
after irradiating UR with a peak energy of 60 eV
and after etching up to a depth of 40nm in GeO2
doped SiO2 films. The generated Ge0 peaks are
disappeared gradually by increasing the etching
depth. After 40nm etching, Ge0 and Ge4+ peaks
are almost the same as that in the non-irradiatedone. The UR dose was 1000mAh.

Conclusions
UR irradiation effects are investigated for an application of silica-based materials to optical waveguidedevices. Although large refractive-index changes were obtained by SR and UR irradiation in silica-based
films in our previous report1), other modification effects such as the surface reduction shown here are also
important in the applications as an utilization tool and an obstacle for other applications. In our results, it isshown that the surface modification effects for Si and Ge bonds could be controlled by changing the peakenergy of UR. From those results, UR is expected to be a useful irradiation source for modifying materials
effectively and also controlling the modification effects as a desired way.
References[1] K.Moriwaki et al., LASTI Annual Report vol.10 (2008).
[2] K.Moriwaki et al., LASTI Annual Report vol.13 (2011).

Characterization BN Thin Film Deposited on Cemented
Carbide using Soft X-ray Absorption Spectroscopy
Masahito Niibe1, Takuya Kotaka1, Satoshi Jinguji2, Satoko Hori2, and Shozo Inoue2
LASTI 1 & Graduate School of Eng., 2 University of Hyogo
Abstract
Crystalline structure of BN thin film deposited on cemented carbide substrate by magnetron
sputtering technique was characterized using soft X-ray absorption spectroscopy (XAS). Boronand nitrogen K near edge X-ray absorption fine structures (NEXAFS) of the BN thin films were
measured with total electron yield (TEY) method and total fluorescence yield (TFY) method. The
film structure changed dramatically from t-BN phase to c-BN phase when film thickness increased
from 6.5 nm to 20 nm. The crystalline structure of the film deposited on the WC substrate with abias voltage of -90 V was still t-BN type. However, the structure changed to c-BN phase when thebias voltage increased to -130 V.
Introduction
As similar to carbon allotropic forms, boron nitride presents a polymorphism of hexagonal structure (h-BN)
having a hexagonal plane network; such as graphite, and cubic structure (c-BN) having a steric structure; such as
diamond. It is well known that h-BN is a relatively soft material. However, c-BN is known to be the second
hardest material after diamond. The preparation of c-BN thin film for a coating material onto cutting tools is
extensively studied. In cases of BN thin film fabrication by sputtering or ion plating depositions, h-BN structure
is preferentially formed because it is a stable phase at normal pressures. Stably-forming technology for c-BN
structured thin film was not confirmed as affairs.
Characterization of crystalline structure of BN thin film is indispensable to confirm the fabrication
technology. Near edge X-ray absorption fine structure (XANES) spectroscopy is an appropriate technique toidentify the crystal structure of BN thin film because the spectra of c-BN and h-BN are quite distinct and thebonding state on sp2 and sp3 can be observed in isolation. In this study, NEXAFS measurement at B-K and N-Kedge was carried out for the characterization of crystalline structure of BN thin film deposited on cemented
carbide (WC) as well as Si wafer by an RF magnetron sputtering technique.
Experiments
BN thin films were prepared on Si (100) and WC substrates by the RF magnetron sputtering system. The
substrate holder was electrically floated for applying a bias voltage and could be heated up to 600°C,
simultaneously. Ar+N2 mixed gas was used as working gas, and its pressure was 0.4 Pa. The DC bias waschanged from -80 to -130 V in this study. Atomic composition of the prepared sample was determined by an
Auger electron spectroscopy (AES).
B-K and N-K NEXAFS spectra of prepared samples were measured in the analyzing station of the beamline
BL9a at the NewSUBARU SR facility. The beamline monochromator was mounted with a plane varied-spacegrating with central groove density of 1200 l/mm, the energy resolution of which was about 0.2 eV near thephoton energy of 400 eV. The measurement was conducted with a total electron yield (TEY) method with sample
current mode and with a total fluorescence yield (TFY) method with measuring the amount of fluorescence by aphotodiode [1] for the same sample at the same position. It is well known that the TEY method can yield
information in a shallow region from the sample surface because of the small escape length of photo-generated
electrons of less than about 5nm [1, 2]. Meanwhile, the TFY method can yield information in a deeper region(bulk) of the sample of more than 100 nm [1] because of the much longer penetration depth of soft X-ray
photons.
Results and discussion
In order to clarify the growth process of BN films containing the c-BN phase, the films were deposited for 1,
2, 3, 5, and 30 min at 600°C and applied bias voltage of -90 V. Figures 1 and 2 show the B-K and N-K
absorption spectra of a prepared films, respectively. The thicknesses of those films were estimated to 6.5, 13, 20,
33, and 200 nm using the deposition rate. For the 6.5-nm-thick film, both B-K edge and N-K edge spectra have alarge ʌ* resonance peaks at 192 eV for B-K and at 401 eV for N-K edges, respectively, which are caused fromsp2 bonding states like a graphite. As the thickness increases to 20 nm, the ʌ* peak at 401 eV in N-K edge
spectra becomes a shoulder. The B-K edge spectrum for the 20-nm-thick film also shows that film has anc-BN-dominant strucrure in spite of the presence of the small ʌ* peak. The NEXAFS spectra for the films withthe thicknesses of 33 nm and above are almost the same as the spectraum of the 20-nm-thick film. This meansthat the t-BN (or h-BN with sp2 bonding) underlayer thickness of the film deposited at 600°C was less than 20

nm and that the c-BN-dominant layer grew from an early stage of the deposition. It was also found from themeasurement of incident angle dependency that the t-BN underlayer had a preferential orientation of the c-axis
parallel to the film surface. The results also correspond well to the results of infrared absorption spectra
measured with FT-IR spectrometer [3].

Fig. 1 B-K NEXAFS spectra of BN thin films with various
film thicknesses prepared on Si wafer at 600͠.

Fig. 2 N-K XANES spectra of BN thin films withvarious film thicknesses prepared on Si wafer at 600͠.

After the structural investigation on the Si substrate, we deposited BN films onto the Si wafer and thecemented carbide (WC) substrates at the same time with substrate temperature of 600°C. At the negative bias
voltage of -90 V, the crystalline structure of the film deposited on the WC substrate was still t-BN phase as
shown in Fig. 3, though the structure of film simultaneously deposited on the Si wafer was c-BN phase. N-K
NEXAFS spectra at different angles of incidence of 90° and 45° for the prepared BN film are shown in Fig. 3 for
TEY and TFY methods. Although, the ʌ* resonance peak measured by TFY method (bulk) shows a small
dependency of incident angle, the angular dependency is very large for the spectra obtained by TEY method(srrface). When the negative bias voltage increased to -130 V, the NEXAFS spectrum on WC substrate changed
dramatically to c-BN phase as shown in Fig. 4.
It is difficult to evaluate the crystalline structure of BN film deposited on WC substrate by transmission type
FT-IR spectroscopy. Therefore, the results obtained in this study suggests the effectiveness of X-ray absorption(NEXAFS) spectroscopy for evaluation of crystalline structure of BN thin films deposited on WC substrates.
BN film on hard metal_N-K TEY, TFY584

TFY 45°

6

TFY 90°4
TEY 45°2

TEY 90°Absorption intensity [a.u.]

Absorption intensity [a.u.]

BN#34 on WC_N-K TEY,TFY103

TFY 90°

2

1
TEY 90°

0
390

400

410

420

430

Photon energy [eV]Fig. 3 N-K NEXAFSS spectra of the BN thin film
prepared on WC substrate with a bias voltage of -90 V.

0
390

400

410

420

430

Photon energy [eV]Fig. 4 N-K NEXAFS spectra of the BN thin film preparedon WC substrate with a bias voltage of -130 V.

References[1] M.Niibe T. Kotaka, T. Mitamura: J. Phys. Conf. Ser., 425, 132008, (2013).
[2] J. Stohr, “NEXAFS Spectroscopy” Springer, Berlin (2003).
[3] S. Hori, M. Niibe, T. Kotaka, S. Inoue et al., Jpn. J. Appl. Phys., 52, 045602 (2013).

Spectral Recovery of Etching Damage by Soft X-ray
Irradiation Observed in XAS spectra of TiO2 Thin Film
Keiji Sano1, Masahito Niibe1, Takuya Kotaka1,
Retsuo Kawakami2, Kikuo Tominaga2, Yoshitaka Nakano3(Univ. Hyogo 1, Univ. Tokushima 2, Chubu Univ. 3)
Abstract
We analyzed TiO2 thin films etched with capacitively coupled plasma etching apparatus by nearedge X-ray absorption fine structure㧔NEXAFS㧕method. As a result, spectral change due todisordering of the crystalline structure was observed by TFY method in the sample treated withhigher gas pressure. We also found that Ti-L spectra of etched sample was recovered to as-grownlike by irradiation with soft X-rays (496 eV) for 10 min. This recovery occurred not only on theirradiation point of soft X-rays but also on the point 2 mm or more away. Furthermore, it was
found that the spectral recovery can also be observed for the surface irradiated with ultraviolet(UV) light instead of soft X-rays.
Introduction
TiO2 is expected to apply as MOS gate oxide film because of its high dielectric constant. To use TiO2 as
MOS gate film, it has to be processed by etching. However, there are few reports about the effect of etchingdamage to TiO2 thin films by etching process. Therefore, we analyzed the effect of etching damage to TiO2
samples by NEXAFS method. As it happens, we found the phenomenon in the analyzing process that disordered
NEXAFS spectra of the etched film recovered to as-grown like by irradiation with soft X-rays.
The purpose of this study is the elucidation of the phenomenon that NEXAFS spectra of etched TiO2 thinfilm were recovered by soft X-ray irradiation. We investigated the condition of the etching damage to recover.
For example, recovery of the spectra is studied for irradiation condition, light source, and irradiation position.
Experiments
TiO2 thin films were deposited on a glass substrate㧔Corning 1737㧕by facing cathodes DC magnetron
sputtering system. We used capacitively coupled plasma (CCP) etching apparatus (Tokushima Univ.) to etch thesamples. The etching gas was N2 and its pressure and etching time were varied from 10 to 100 mTorr and 5 to
200 minutes, respectively. These samples were analyzed by NEXAFS method conducted at BL09A in the
NewSUBARU synchrotron radiation facility[1]. The measurements were carried out with total fluorescence yield(TFY) method (bulk sensitive) and total electron yield (TEY) method (surface sensitive) at the Ti-L2,3 edges (443
~ 496 eV)[2]. NEXAFS method can obtain the information of chemical state or local structure around the element
selectively by measuring an absorption edge of any element in the sample in non-destructive.
Results
As shown in Fig.1 (a), the spectra measured by TFY method was changed that the peak near 467 eV became
lower with increasing the etching gas pressure. However, as shown in Fig.1 (b), there was little change due toincrease of the gas pressure in the spectra by TEY method. Therefore, we got a very strange result that theetching damage of the sample surface was small but the damage at the sample inside was larger.
Continuing the measurement in order to investigate the cause, we found that the spectra of the etched sample
were recovered to as-grown like by soft X-ray irradiation. Fig.2 shows the recovery process of the NEXAFS
spectra by soft X-ray irradiation measured with TFY method. The etching gas pressure of the sample was 100
mTorr, and the etching time was 60 minutes. The spectrum of etched sample became as-grown like by soft X-ray
irradiation (496 eV, tens of mW/cm2) for 30 minutes. After the irradiation, the spectra of recovered samples werereturned to disordered shape by exposure to air, and then measured again after 21 days later. After returning todisordered shape by air exposure, the sample spectrum changed to as-grown like again by re-irradiation with soft
X-rays for 10 minutes.
The bonding orbital around the Ti atoms should be disturbed by generation of oxygen vacancies. The spectra
should be disturbed by disarray of crystalline structure. Therefore, it was considered that the spectra wererecovered by supplement of the defective part. Since the spectral recovery by soft X-ray irradiation returned tothat of after etching by exposure to the air, we considered that the spectrum recovered apparently by electrons
which are from the electron-hole pairs generated by light irradiation and are trapped at the oxygen vacancies.
Etched Sample was irradiated with soft X-rays for 25 minutes at the center position of the sample in order tofind out whether NEXAFS spectrum was recovered as spatially distributed. After irradiation, the sample wasmeasured at the position separated from 2 mm above and below the irradiation center. soft X-rays were notirradiated at the position separated 2 mm from the center because the beam size of irradiated soft X-rays inBL09A is 0.8 mmH × 0.3 mmV. However, the spectrum was recovered as-grown like not only at the center
position of the sample but also the position separated 2 mm above and below from the center. We consider thatrecovery of spectrum was observed at the position outside of the irradiation due to the diffusion of generated
excitons to the periphery of the irradiation position as free excitons.
If the fact of spectral recovery is caused by excitons generated by soft X-ray irradiation, it is considered thatthe spectra should be recovered by UV irradiation instead of the soft X-rays, the energy of which is above theband gap energy of anatase TiO2 (3.2 eV). Therefore, we tried to irradiate UV light (3.4 eV, 49 mW/cm2) to theetched sample (CCP-N2, 100 mTorr , 60 min) in vacuum. Fig.3 shows the recovery process of the NEXAFS
spectra by UV irradiation measured with TFY method. The spectrum of etched sample was recovered toas-grown like by UV irradiation. From the results above, it was considered that the spectral recovery of theetched sample should be apparent recovery due to the electrons generated by soft X-ray irradiation and trappedin the oxygen vacancies.
3.0

3.0

CCP N 2 60min

Absorption Intensity [a.u.]

2.5

100 mTorr

2.0
1.5

50 mTorr

1.0

10 mTorr

0.5

CCP N 2 60min

TEY
2.5

Absorption Intensity [a.u.]

TFY

100 mTorr
2.0
1.5

50 mTorr

1.0

10 mTorr

0.5

as-grown

as-grown

0.0

0.0
450

460

470

480

490

450

Photon Energy [eV]

460

470

480

490

Photon Energy [eV]Fig.1 Ti-L2,3 NEXAFS spectra of etched TiO2 thin films(a): TFY method and (b): TEY method.

2.5

CCP N 2
100mTorr 60min

TFY

Absorption Intensity [a.u.]

3.5

Re-irradiation for 10 min

3
2.5

After 21 days

2

irradiation for 30 min(496 eV)

1.5
After etching

1

CCP N 2
100mTorr 60min

TFY
Absorption Intensity [a.u.]

4

2

UV irradiation for 10 min
in vacuum
1.5
After etching1

0.5
as-grown

0.5
as-grown

0

0
450

460

470

480

490

450

Photon Energy [eV]Fig.2

Recovery of Etching Damage
by Soft X-ray Irradiation.

460

470

480

490

Photon Energy [eV]Fig.3

References[1] M.Niibe et al.: AIP Conf. Proc. No.705 (AIP, New York, 2004), p.576[2] T.Kotaka and M.Niibe: Adv. X-ray Chem. Analysis, 43 (2012) 175.

Recovery of Etching Damage
by UV Irradiation.

Modification of Electronic States of Multi-layer Graphenes by
Ion Irradiation
S. Honda1,7, A. Tsukagoshi1,7, R. Osugi1,7, M. Niibe2, and M. Terasawa2,71
Univ. of Hyogo, 2LASTI Univ. of Hyogo
R. Hirase3, H. Yoshioka3, and H. Izumi3
3
Hyogo Pref. Inst. of Tech.
K.-Y. Lee4
4
National Taiwan Univ. of Sci. and Tech.
K. Niwase55
Hyogo Univ. of Teacher Education
E. Taguchi6
6
Research Center for Ultra-High Voltage Electron Microscopy, Osaka Univ.
M. Oura7
7
RIKEN SPring-8 Center
Abstract
Low energy Ar ions (0.5 - 2 keV) were irradiated to multi-layer graphene films and the local electronic states
were investigated by x-ray absorption spectroscopy (XAS). XAS analysis indicated that the number of
sp2-hybridized carbon (sp2-C) atoms decreased after ion irradiation. At the same time, sp3-hybridized carbon(sp3-C) atoms were suggested to be formed in the multi-layer graphenes.
Experiments and Results
Multi-layer graphene films were synthesized
by thermal catalytic chemical vapor deposition.
Figure 1(a) shows a transmission electron
(a)

5 nm
(b)
2D
Intensity (a.u.)

Introduction
Graphenes [1] have been attracting
tremendous attention as new semiconductors
because of their intriguing properties, such as theextraordinarily high room-temperature carrier
mobility, high thermal conductivity and highYoung's modulus. These properties of graphenes
can be employed in numerous potential
applications such as transparent conductors andquantum devices. On the other hand, the controlof electrical and optical properties is essential torealize graphene devices. Irradiation of graphenes
with energetic particles is thought to enable us tocontrol their properties and structure [2,3]. It has
been reported that the doping level of graphenes
can be also controlled by ion irradiation [4].
Several analytical techniques can be used tocharacterize irradiated graphenes. For example,
Raman spectroscopy [5–9], transmission electron
microscopy (TEM) [10], scanning tunnelingmicroscopy (STM) [11], and X-ray photoelectron
spectroscopy (XPS) [3] have been employed to
study the properties and structure of irradiatedgraphenes. Soft X-ray absorption spectroscopy(XAS), on the other hand, is a powerful tool since
it provides information on not only the local
electronic structure surrounding excited carbon
atoms, but also the orientation of the carbon S
bonds [12]. In this study, to modify the electronic
states of the multi-layer graphenes by theirradiation, we irradiated multi-layer graphenes
with low-energy Ar ions (0.5–2 keV), andinvestigated the local electronic states by XAS.

2600

2650
2700
2750
Raman Shift (cm-1)

2800

Fig. 1. (a) Cross-sectional TEM image ofas-prepared multi-layer graphene films. (b) 2D
peak of Raman spectrum of as-prepared graphenefilms.

+

1 keV Ar

1u1015 ions/cm2

Intensity (a.u.)

microscopy (TEM) image of as-preparedmulti-layer graphene films. The number and thetotal thickness of graphene layers were 6 andabout 2 nm, respectively. We employed a
Kaufman ion source (ULVAC-PHI MOD
04-370B) to irradiate the multi-layer graphenefilms at room temperature (RT) with Ar ions. The
incident energy ranged from 0.5 to 2 keV and thedose varied between 1u1013 and 1u1015 cm-2.
Micro-Raman spectra were taken with Ar ion
laser (514.5 nm) using a Raman spectroscope(JASCO, NRS-2100). Fig. 1(b) shows the 2D
peak of the Raman spectrum of the graphenefilms. It has been reported that the 2D peakchanges in shape, width, and position withincreasing number of graphene layers [13]. On thebasis of the previous assignment, the number ofgraphene layers is estimated to be 3–5. This result
is consistent with the results of TEM. The carbon
K-edge XAS measurement was performed using
BL09 of the 1.5 GeV synchrotron radiation source
NewSUBARU at the University of Hyogo [14].
The total electron yield method was used for themeasurement.
In order to explore local electronic states ofthe multi-layer graphene films, XAS was utilized
for the multi-layer graphene films irradiated under
different conditions. The spectra were measured
at different angles of incident soft X-rays to thesubstrate surface (D) and normalized to theirintensity at a320 eV. Fig. 2 is the XAS spectra ofgraphene films irradiated at an energy of 1 keV,taken at D=55q. The S peak of 285 eV and V
peak of 292 eV were clearly observed. The sp2-C
atom generally exhibits both S and V peaks,
whereas the sp3-C atom exhibits only the V peak[15]. It was found that the intensity of the peakdecreased with increasing ion fluence. This
indicates decreasing number of sp2-C atoms after
the ion irradiation. At the same time, an additional
shoulder at a289 eV is also recognized after theion irradiation, as shown by arrow in Fig. 2. Theenergy at the shoulder is close to that at the C-K
absorption edge for single-crystal diamond, andmay be related to the formation of sp3-C atoms inthe multi-layer graphene films [16]. With
increasing ion fluence, an additional peak at a287
eV was recognized in the XAS spectra, as shownby arrow in the Fig. 2. Additional peaks at a289
eV and a287 eV, which appeared similarly in theprevious study for the study for the damaging
stages of multiwalled carbon nanotube films [17],have been respectively assigned to relate to theformation of sp3-C and dislocation dipoles. The
dislocation dipoles possess fivefold and sevenfold
rings, thereby inducing the buckling and therotation of the hexagonal networks [18–20].

1u1014 ions/cm2

S*

280

V*

as-prepared

290

300
310
Energy (eV)320

Fig. 2. XAS spectra of multi-layer graphenefilms irradiated by 1 keV Ar ions at different
fluences.
References[1] K. S. Novoselov et al., Science 306, 666 (2004).
[2] A. V. Krasheninnikov and K. Nordlund, J. Appl.
Phys. 107 (2010) 071301.
[3] F. Banhart et al., ACS Nano 5 (2011) 26.
[4] H.-G. Jee et al., Phys. Rev. B 84 (2011) 075457.
[5] G. Compagnini et al., Carbon 47 (2009) 3201.
[6] J.-H. Chen et al., Phys. Rev. Lett. 102 (2009)
236805.
[7] Y.-B. Zhou et al., J. Chem. Phys. 133 (2010)
234703.
[8] J. J. Lopez et al., Appl. Phys. Lett. 107 (2010)
104326.
[9] S. Mathew et al., J. Appl. Phys. 110 (2011)084309.
[10] J. C. Meyer et al., Nano Lett. 8 (2008) 3582.
[11] L. Tapasztó et al., Phys. Rev. B 78 (2008)
233407.
[12] T. Hemraj-Benny et al., Small 2 (2006) 26.
[13] A. C. Ferrari et al., Phys. Rev. Lett. 97 (2006)
187401.
[14] M. Niibe et al., AIP Conf. Proc. 705 (2004) 576.
[15] J. Stöhr, NEXAFS Spectroscopy (Springer,
Heidelberg, 1992).
[16] F. L. Coffman et al., Appl. Phys. Lett. 69(1996) 568.
[17] S. Honda et al., Jpn. J. Appl. Phys. 51 (2012)
110202.
[18] K. Niwase, Philos. Mag. Lett. 82 (2002) 401.
[19] K. Niwase, Mater. Sci. Eng. A 400–401(2005) 101.
[20] K. Niwase, Int. J. Spectrosc. 2012 (2012) 1.

Fabrication of amino acid analysis chipusing SR direct dry etching of PTFE
H. Kido a, I. Okada b, H. Mita c, A. Yamaguchi a, and Y. Utsumi a
University of Hyogo, 3-1-2 Kouto, Kamigori, Ako, Hyogo, 678-1205, Japanb
Nagoya University, Furo-cho, Chikusa-ku, Nagoya, 464-8601, Japanc
Fukuoka Institute of Technology, 3-30-1 Wajiro-Higashi, Higashi-ku, Fkuoka, 811-0295, Japana

Abstract
Polytetrafluoroethylene (PTFE) is very attractive material for various fields, because of its
chemical resistance and heat resistance, etc. But, micro fabrication of PTFE is very difficult fromits high stability. Therefore, PTFE has never been applied to micro fluidic device. However, it is
known that synchrotron radiation (SR) induces scission of polymer chain of PTFE. We have everbeen succeeded in the fabrication of PTFE micro fluidic chip using SR dry etching and thermal
compression bonding. As a next step, we have been engaged in the fabrication of PTFE micro
fluidic chip for amino acid derivatization process. PTFE is an ideal material for performing thederivatization process. Because, this process using some strong acid, and some processes such as
extraction and hydrolysis require high temperature heating operation. There is no precedent of theapplication of such complex micro structure made of PTFE to the device for chemical analysis.
Introduction
In Solar system bodies, Amino acids, which are biologically important organic compounds, have played a
key role in the chemistry that led to the origin of life on Earth. Precise analysis of the amino acid contained in
extraterrestrial samples is very important in the study of the origin of life. We recently have opportunities foranalyzing fresh extraterrestrial samples by collection of cosmic dust and sample return from asteroids, etc [1].
However, the amounts of the samples which can be used for analysis are limited because the samples are smallin amount. Therefore, amino acid analyses for the samples using a micro fluidic chip are required. In this study,
we develop the micro fluidic chip which can realize fluorescent derivatization required for optical isomer ratio
analysis of the amino acid included in the samples.
Experiments and Results
The sequence of analysis operations for the amino acid in the extraterrestrial samples includes extraction,
filtration, hydrolysis, and evaporative drying. Therefore, high chemical resistance and heat resistance are
required for the material of the chip. For this reason, we chose polytetrafluoroethylene (PTFE) as a chip material.
PTFE has very excellent chemical stability, and its heat resistance is far higher than those of plastic materials.
Although the PTFE has the high chemical stability, micro fabrication of PTFE is difficult because the small
modulus of elasticity is not suitable for normal mechanical processing. Up to now, micro fluidic device made ofPTFE has never been reported. It is known that synchrotron radiation (SR) induces scission of polymer chain of
PTFE [2 3]. Figure 1 shows the etching mechanism of SR direct dry etching of PTFE. We have been fabricated
PTFE microstructures by direct dry etching using SR [4]. The combination of PTFE microstructure using SR
dry etching process and compression bonding enables us to PTFE micro fluidic chemical analyzer. In previous
study, we fabricated simple micro fluidic chip which had only one micro channel.
In this study, we developed a novel micro fluidic device which had multiple micro channels and incorporated
a filter structure for filtration. Figure 2 shows the schematic diagram of fabricated amino acid analysis device.
This device consists of two chips, and the function of valve is performed by sliding of the upper chip. The microchannels are incorporated into the lower chip. The lower chip has four reservoirs for reagent such asderivatization reagent, and each reservoir can hold 10Pl. In addition, we disposed two reaction reservoirs for
extraction and derivatization into the lower chip. Extraction reservoir has micro filter for filtration of protein
contained in the sample on the downstream side of reservoir. We set the filter dimension to 50Pm squarebecause the size of extraterrestrial sample is assumed to be 100–200Pm in diameter. Derivatization reservoir
operates the hydrolysis of protein to amino acid and fluorescent derivatization. Heating operation in thederivatization reservoir is required in both sealed and open states. We realize both heating states in a single
reservoir by opening and closing the upper part of the reservoir using the slide mechanism. In addition, the filter
structure is incorporated in the derivatization reservoir for prevention of liquid leakage. For the function of thecapillary valve, we set the filter dimension to 50Pm square.
There is no precedent of the application of such complex micro structure made of PTFE to the device forchemical analysis. This study is very important for progress of science, technology and space development
because our device has the potential to perform the chemical analysis with laboratory level on the spot where
we are difficult to visit.

Figure 1. Etching mechanism of SR direct dry etching of PTFE: (a)drastic bond break in near surface, (b) bond break deep inside of thesubstrate and vaporizing from surface, (c) melting point shift andvaporizing from deep inside of the substrate, (d) penetrationof mask pattern.

Upperchip

Valvechannel
Reagentreservoir
Compressedairinlet
Sampleoutlet

Filtrationfilter
Sampleinlet

Extractionreservoir
Derivatization reservoir Lowerchip

Microfilter(50Pmsquare)

Figure 2. Schematic diagram of amino acid analysis device.
References[1] D. E. Brownlee, P. Tsou, J. D. Anderson, M. S. Hanner, R. L. Newburn, Z. Sekanina, B. C. Clark, F.
Horz, M. E. Zolensky, J. Kissel, J. A. M. McDonnell, S. A. Sandford, A. J. Tuzzolino, JGR Planets, 108 (E10)(2003) 8111-8126.
[2] Y.Zhang, T.Katoh, M.Washio, H.Yamada, S.Hamada, Appl.Phys.Lett.67 (1995) 872-874.
[3] Yuichi Utsumi, Takefumi Kishimoto, Tadashi Hattori, Hirotsugu Hara, Jpn. J. Appl. Phys., 44,7B (2005)
5500-5504[4] Yoshiaki Ukita, Kazuhiro Kanda, Shinji Matsui, Mitsuyoshi Kishihara, Yuichi Utsumi, Microsyst
Technol 14 (2008) 1567-1572.

Powder Transport Direction Control Method by Using
Drive Frequency of Surface Acoustic Wave
Yasuto Arisue1, Yuya Matsui1, Tsunemasa Saiki2, Kazusuke Maenaka3, Akinobu Yamaguchi1
and ,Yuichi Utsumi1
1
Laboratory of Advanced Science and Technology for Industry, University of Hyogo,
3-1-2 Koto, Kamigori, Ako-gun, Hyogo, 678-1205, JAPAN
Phone: +81-791-58-0232, Fax: +81-791-58-0232,
2

Hyogo Prefectural Institute of Technology, Kobe, 654-0037, JAPANE-mail: pippikki@lasti.u-hyogo.ac.jpPleaseabstract
We propose a novel method for controlling the powder transport direction by drive frequency,
and demonstrate the validity of this method by experiments. In our experiments we could observe
several powder transports by specific combinations of inclination angles and drive frequencies.
Introduction
To integrate a lab-on-a-chip has been extensively studied. The surface acoustic wave (SAW) is particularlyinteresting because of its ability to add a novel liquid actuation method which makes to simplify the designing oflab-on-a-chips. Up to now, we succeeded in developing (SAW) actuators for transporting continuous liquid and ahigh-efficiency liquid mixing chip using SAW actuators [1]. Meanwhile, the displacement of solid by the SAWs
had been reported [2]. If powder can be transported, we can establish a ontrolling process consisting of powder
movement, powder injection into liquid, and themselves mixing operated only by the SAWs on one-chip.
However, unlike continuously flowing liquid in a channel, spatially controlling powder transport by using theSAWs is difficult, because the powder transport direction must be aligned with an axis direction of an interdigitaltransducer (IDT) that generates the SAWs. Therefore, we changed the method for controlling the powdertransport direction by using reflected SAWs from a micro groove and succeeded in moving the powder by thereflected SAW [3]. Moreover, if the powder can be transported in not only the upstream direction but also
downstream direction of the SAWs, the flexibility of powder transportation will be enlarged in its applications.
In this paper, we propose a novel method for controlling the powder transport direction by drive frequency, anddemonstrate the validity of this method by experiments.
Figure 1(a) shows a photograph of our fabricated SAW actuator for powder transport. The SAW actuator was
fabricated by IDT (1-μm   thick   Al   layer)   patterning   on   a   piezoelectric   substrate   (127.8   degree   y-rotatedx-propagating LiNbO3) using photolithography. We fabricated four SAW actuators on a 4-inch wafer. Figure 1(b)shows a schematic diagram shown relationship between IDT and orientation flat of the wafer. The IDTs of the
SAW  actuators  were  located  at  inclination  angles  θ  of  0,  30,  60,  and  90-deg. against perpendicular direction of
the wafer orientation flat. Here,  we  chose  a  proven  IDT  shape  of  a  200μm  stripline  pitch,  a  5mm  aperture,  and  20  stripline pairs.
Experiments and Results
Figure 1(a) shows a photograph of our fabricated SAW actuator for powder transport. The SAW actuator was
fabricated by IDT (1-μm   thick Al layer) patterning on a piezoelectric substrate (127.8 degree y-rotatedx-propagating LiNbO3) using photolithography. We fabricated four SAW actuators on a 4-inch wafer. Figure 1(b)shows a schematic diagram shown relationship between IDT and orientation flat of the wafer. The IDTs of the
SAW  actuators  were  located  at  inclination  angles  θ  of  0,  30,  60,  and  90-deg. against perpendicular direction ofthe  wafer  orientation  flat.  Here,  we  chose  a  proven  IDT  shape  of  a  200μm  stripline  pitch,  a  5mm  aperture, and 20
stripline pairs.
Figure 2 shows frequency characteristic of return loss (RL) of our fabricated SAW actuator. The RL is thelogarithmic ratio of the incident electric power PI to the reflected electric power PR and increases as the applied
power ratio to the IDT increases. At the SAW actuator with 0-deg. inclination angle, one RL peak was observed
at 19.1MHz, and then multiple peaks were observed. The 19.1MHz is the conventional drive frequency of the
SAW actuator, and corresponds approximately to the value of propagation velocity of a Rayleigh-wave(3690m/s)  divided  by  IDT’s  pitch  size  (200μm).  On  the  other  hand,  because  there  existed  the  multiple  peaks,  it  is  considered that the SAW actuator had potential to generate SAWs at their peak frequencies. In the same way as
the SAW actuator with 0-deg inclination angle, there exist lots of RL peaks in the other SAW actuators withdifferent inclination angles.
Next, we investigated powder transport behaviors by the SAW actuators applied at the RL peak frequencies asdrive frequencies. Figure 3 shows experimental setup for powder transport. Before starting the experiments, thepowder was uniformly spread on the wafer by a sifter. Here, for the powder we used tungstic anhydride (average
particle size of 22.3µm) in consideration of visibility and insulation. In the experiment, a function generator
created 1-kHz burst waveforms consisting of 2000 cycles of fD MHz sine waves, where, it, corresponded to theobtained RL peak frequencies. If SAWs were generated by applying the boosted voltage, the powder might betransported by the propagated SAWs. At this time, the powder transport behavior was recorded with ahigh-definition video camera.
In our experiments we could observe several powder transports by specific combinations of inclination angles
and drive frequencies. The most notable ones are that the SAW actuator with 90-deg. inclination angle could
transport the powder forward and backward with high transport efficiencies in comparison with the other SAW
actuators. The investigation powder transport characteristics with different inclination angles can be very usefulin the designomg a chip consisting of the SAW actuators for powder transport control
.
(a)
(b)

Figure 1 (a) Photograph of SAW actuator for powder transport.
(b) Location relationship between IDT and orientation flat.

Figure 2 Frequency characteristic of return loss of SAW actuator.

Figure 3 Experimental setup for observing the powder transport driven by SAW actuators.
[1] T.  Saiki,  K.  Okada  and  Y.  Utsumi,  “High  Efficiency  Mixing  and  Pumping  of  Continuous  Liquid  Flow  using  Surface-Acoustic-Wave”,  13th International Conference on Miniaturized Systems for Chemistry and Life Sciences (µTAS2009), 58 (2009).
[2] M.   Kurosawa,   M.   Takahashi   and   T.   Higuchi,   “Ultrasonic   Linear   Motor   Using   Surface   Acoustic   Waves”,   IEEE   Transactions   on  Ultrasonics, Ferroelectronics, and Frequency Control, 43, 901 (1996).
[3] T.  Saiki,  H.  Tomita,  H.  Shizuka,  K.  Okuda,  K.  Maenaka,  Y.  Utsumi,  “Reflected  Surface  Acoustic  Wave  Actuator  Using  Micro  Groove”,  37th International Conference on Micro and Nano Engineering (MNE2011), 490 (2011).

Fabrication of SERS Active Three-dimensional
Silver Nanostructure
R.Hara*,R.Takahashi*, T.Fukuoka* , A.Yamaguchi* , Y.Utsumi**Laboratory of Advanced Science and Technology for Industry, University of Hyogo
3-1-2 Koto, Kamigori, Hyogo, 678-1205 JAPANE-mail: hara099@lasti.u-hyogo.ac.jp
Phone/Fax: +81-791-58-0232
Introduction
Recently, surface enhanced Raman scattering (SERS) is attracting attention as a high sensitive analysis system.
SERS is the detection method using Raman spectroscopy and localized surface plasmon resonance (LSPR). To
enabling strong LSPR, the noble metal nanostructure like gold or silver is essential. In previous report, gold
nanoparticles were used to fabricate nanostructure. In this study, by using convective self-assembly [1] ofparticles, we developed the three-dimensional silver nanostructure (Ag3D) because low cost silver is moredesirable material for SERS active nanostructure than gold. In addition, silver is thought to be suitable for the
SERS measurement of various compounds.
Fabrication of Ag3D
We pasted silicone sheet with 6 mm throughhole on the UV-cleaned slide glass, and made a well. 5µl of themixed solution of the silver nanoparticle (AgNP) and polystyrene latex beads (PS) was dropped into the well anddried at 75 % relative humidity for about 1 day. The PS colloidal crystal was fabricated by convective
self-assembly, where AgNP were simultaneously accumulated in the gaps of the PS. The structure was soaked indichloromethane to remove PS. Thus, Ag3D was successfully obtained (Fig.1).
SERS measurements
As shown in Fig.2, unique honey-comb structure of Ag3D was fabricated at a part of the well. We
demonstrated in situ SERS measurement of 4,4’-Bipyridine (4bpy) as the Raman active molecule, using theAg3D. First, silicone sheet with 6mm throughhole was pasted to the Ag3D on the glass to make a measurement
well. Second, 35 µl of 4bpy aqueous solution was dropped into a well on the Ag3D. A cover glass was put on toprevent drying of 4bpy solution and changing of 4bpy concentration. Ag3D was set to Raman spectrometer, and
1 s irradiation of 785 nm (50 mW) laser focused on the Ag3D was started.
We observed the characteristic enhanced Raman spectrum of 4bpy (1000 cm⁻1, 1250 cm⁻1, 1580 cm-1) within 1
min after dropping 4bpy (Fig.3). SERS spectrum was only observed in the part of Ag3D, while no SERS wasobserved in the part without Ag3D. Raman spectra were enhanced about 10⁵ times, compared with the casewithout Ag3D. Although the peak of 1 nM 4bpy solution was weak, it was detectable. The case with Ag3D andthe case with Ag colloid aggregation were compared in the 4bpy peak height of 1580 cm -1 (Fig.4). SERS
measurement using Ag3D was stable even after time passed, while peak intensity drastically dropped withinminutes in the case with Ag colloid. one reason for this was that SERS active structure of Ag colloid was broken
by aggregation process over time. In addition, we succeeded in observing the chloride activation which increased
to 2-3 times in Raman intensity of 4bpy by the addition of NaCl to Ag3D (Fig.5). As a result, we have achieved
a high sensitivity SERS measurement using Ag3D. SERS activity of Ag was generally higher than Au in thecolloidal system, although obtained SERS using Ag3D [2] was still weak compared to the case using Au3D
which was consisted gold nanoparticles. There is a possibility of enabling strong SERS if Ag3D fabrication is
optimized.

.

PS
AgNP

Fig.1: (a) A schematic diagram of self-assembled
structure. (b) Ag3D after drying and remove PS

Fig.4: 4,4’-Bipyridine peak intensity with

Intensity

Ag3D and Ag colloid aggregation.

Fig.2: Microscopic image of three-dimensional
silver nanostructure.

8000
7000
6000
5000
4000
3000
2000
1000
0
800

blank
100uM
100uM_Cl

1200 1600 -12000
Raman Shift / cm

2400

Fig.5: Chloride activation of 4,4’-Bipyridine

3000

↓

Intensity

2500
2000
1500

100 nM
1 nM
blank

↓

1000

↓

500
0
800

1200 1600 2000 2400
-1
Raman Shift / cm

Fig.3: SERS spectra of 4,4’-Bipyridine.

References:[1] Y. Mori, N. Shinohara, and T. Fukuoka, International Workshop on Nanomechanical Cantilever
Sensors 2008, P48, 2008.
[2] T. Fukuoka, and Y, Utsumi: Rev. Laser Eng. 40 (2012) 930 [in Japanese].

Blood separation chip
for automated biological analysis
T.Kunisada1, H.Nose1,M.Ishizawa1, K.Kuroda1, I.Okada2 A.Yamaguchi1 and Y.Utsumi1
1

Laboratory of Advanced Science and Technology for Industry, University of Hyogo,
3-1-2 Kouto, Kamigori, Ako-gun, Hyogo 678-1205, Japan
2

Nagoya University Synchrotron Radiation Center, Japan

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

Phone/Fax: +81-791-58-0232

Abstract
We present a chip for the blood separation using centrifugal force and capillary force. We expect that this chipcan perfome overall assay with high-efficiency and significantly shorten the analysis time by integrate our
proposed 3D lab-on-a-CD. The material of the chip which is fabricated by using X-ray lithography is SU-8 and
Si. Blood separation is done using centrifugal force by spinning the chip at a frequency of 40Hz and transport tocollection reservoir from separation reservoir using capillary force. It is necessary for capillary force to treat
surface condition. We succeed in liquid transportaion by only control spin speed.
Introduction
The lab-on-a-CD is promising for the automation of multiple microreactor systems. Recently,
high-performance immunoassay based on lab-on-a-CD has been proposed [1]. The extraction of plasma fromwhole blood is the first preparative step in many assay protocols and major importance in medical diagnosis [2].
We present a chip for the extraction of blood plasma from whole blood using centrifugal force of spin andcapillary force. We expect that this chip can be overall assay with high-efficiency and significantly shorten theanalysis time by integrate our proposed 3D lab-on-a-CD [3].
We present a chip for the blood separation using centrifugal force and capillary force. We expect that this chipcan perfome overall assay with high-efficiency and significantly shorten the analysis time by integrate our
proposed 3D lab-on-a-CD. The material of the chip which is fabricated by using X-ray lithography is SU-8 and
Si. Blood separation is done using centrifugal force by spinning the chip at a frequency of 40Hz and transport tocollection chamber from separation chamber using capillary force. It is necessary for capillary force to treat
surface condition. We succeed in liquid transportaion by only control spin speed.
Experiments and Results
We designed chip as shown in Fig.1. We formed a CHF3 plasma chemical vapor deposition (CVD) film on thecapillary valve just before the experiment. The plasma chemical vapor deposition (CVD) film with fluorine has acontact angle of over 100° [4]. By coating valve, liquid can be held until the higher rotation.
Process of blood separation is described in Fig.2. First of all, we injected whole blood into the separation
reservoir (Fig.2a). In spinning the chip blood separation was performed by centrifugal force(Fig.2b,e①).
Rotational speed is accelerated up to frequency of 25Hz(Fig.2e②). It was less than the burst frequency of thecapillary valve. Phase separation was caused in a centrifugal field by a difference in mass density (Fig.2c).
During blood separation, the capillary valve is used to control the flow sequence and hold liquid by surface
tension. After finishing the separation, rotating speed was accelerated above the burst frequency. Then, thecapillary valve was burst by the stronger centrifugal force (Fig.2d,e③). Next, liquid transportation was started
and rotating speed should be decelerated to avoid disturbing rise by centrifugal force(Fig.2e④). Liquid rose in
the capillary to the same height as the surface of liquid in the separation reservoir and reached the hydrophilic
area. As soon as liquid reached the hydrophilic area, liquid is extracted by capillary force toward the collection
reservoir. When liquid passed through the top of the capillary, rotating speed was accelerated again andextraction to the collection reservoir quickly(Fig.2e⑤). Blood cells remained at the bottom of the separation
reservoir.
In this way, it is possible to control the flow sequence only controlling the rotation speed of the chip. We
expect that the proposed chip will be able to extract only plasma from whole blood automatically.

Capillary valve
Hydrophilic
area

30μm

Inlet

CapillaryHydrophobicareaCollection reservoir

5mm

Separation reservoir

Fig.1: Schematic of microchannel.

eFig.2: (a)-(d) Optical micrograph of each process of blood separation. (e)Protocol diagram.
References[1] S. Lai, S. Wang, J. Luo, L. J. Lee, S. T. Yang, and M. J. Madou, Analytical Chemistry, 76, 1832 ,(2004)[2] Stefan Haebelre, Thilo Brenner, Roland Zengerle, and Jens Ducree, lab chip, 6, 776-781, (2006)[3] Saki Kondo, Tsukasa Azeta, Yoshiaki kita, Yuichi Utsumi, Microsyst Technol, 16, 1577-1580, (2010)[4] M.Okada, K.Nakamatsu, Y.Kang, K.Kanda, Y,Haruyama, and S.Matsui,Applied Physics, 48, 06FH15, (2009)

Optimization of Surface Enhanced Raman Scattering
Active Three- Dimensional Gold Nanostructure
R. Takahashi*, T. Fukuoka*, Y. Utsumi*, A. Yamaguchi**Laboratory of Advanced Science and Technology for Industry, University of Hyogo, 3-1-2 Koto,
Kamigori, Hyogo 678-1205, JAPANE-mail: jo-ji@lasti.u-hyogo.ac.jp, Phone/Fax: +81-791-58-0232
Abstract: Recently, Surface Enhanced Raman Scattering (SERS) attracts attention as a high sensitive
analysis system. Taking into account that one dimensional linearly connected gold nanoparticles (AuNP)[1] and two dimensional array of elongated AuNP [2] showed longitudinal localized plasmon resonanceand excellent SERS performance, three dimensional layer stacks of chain-like assembles of AuNP withnumerous particle junctions are desirable. To accomplish thick stacks, we have focused on the three
dimensional gold nanostructure (Au3D) using a casting method of convective self-assembly (CSA) of
AuNP and polystyrene latex beads (PS) [3]. In this report, Au3D with thicker stacks was developed by
optimization of AuNP and PS component in CSA and SERS measurements were demonstrated.
Fabrication of Au3D and SERS measurement: A PDMS sheet with a 6 mm through hole was attachedon the uv-cleaned slide glass, where hydrophobic PDMS wall of the 6 mm well was made acircumference  of  “coffee-ring”  so  as  to  pin  a  drop  of the AuNP (8.4×1014 particles/l) and PSL (2.3×1016
particles/l) mix dispersion with various composition which were dropped into the well. Since thehydrophobic surface of PDMS also made a convex meniscus of the drop around which surface/volume
ratio was larger than other part of the drop, evaporation of water was accelerated around thecircumference. As a result, the thickly stacked self-assembles  on  the  edge  of  “coffee-ring”  was  formed.  
After soaking with dichloromethane to remove PSL, sterically-bulky Au3D with enough thickness was
obtained as shown in Fig. 1.
In situ SERS measurement was performed using Au3D  and  4,4’-bipyridine (4bpy) as the Raman active
molecule. 4bpy aqueous solution (30 µl) was dropped into the measurement well, and covered with acover glass in order to prevent drying or concentration. The collection time of each SERS measurement
was 1 second (average 10 times at 0.1 second) using Raman spectrometer (RAM-100S, Lambda VisionInc., Yokohama Japan) with 785 nm laser (100 mW). As results, we succeeded in 100 nM 4bpy detection.
Optimization of Au3D: In order to obtain further SERS active structure, we performed optimization of
Au3D fabrication concerning dropping volume of mixed dispersion (3, 5, 7, 10, 15, 20 µl), the particle
number ratio (AuNP:PS = 100:1, 300:1, 1000:1, 3000:1), Au diameter (16, 22 nm) and PS diameter (100,600, 1400 nm). SERS active of the Au3D were evaluated by measuring 4bpy. As results, optimum
conditions of dropping volume, the number ratio, Au diameter and PS diameter respectively were 5 µl,
1000:1, 16 nm and 600 nm as shown in Fig. 2-4. By using Au3D of optimum conditions, we achieved
high sensitive measurement of 1 nM 4bpy as shown in Fig. 5. This enhancement reached over 107
compared with the normal Raman spectroscopy without Au3D.
In addition, we found that Au3D’s width in radial direction depended on Au particle number.. Then, thewidth of Au3D was controlled as shown in Fig. 6. By using this broad Au3D, the background from theslide glass was reduced even inexpensive Raman spectrometer without confocal system. Further highsensitive detection is expected by using broad Au3D. Furthermore, we also succeeded in the detection of
10 μM  histamine  and 50 μM melamine. Au3D is to be applied to the field of bioassay and food safety.

a

700

b

600

3 µm
Fig. 1. (a) SEM image of Au3D. The diameter ofthe holes is about 600 nm. (b) Enlarged SEM
image of honeycomb network of granularassembled gold nanoparticles.

Peak Height at 1600 cm

-1

700
Blank
Au:PS=300:1
Au:PS=1000:1
Au:PS=3000:1
Au:PS=5000:1

600
500
400

Intensity

500

1 µm

400

100 nM
10 nM
1 nM
Blank

300
200
100
0
800

1000 1200 1400 1600 1800
-1
Raman Shift / cm
Fig. 5. Characteristic enhanced Raman spectraof 4bpy with different concentration (100 nM,
10 nM, 1 nM, Blank) by using optimum Au3D.

a

300

b

200
100
0

1nM

10nM

50nM

4,4'-Bipyridine concentration

Fig. 2. Optimization of Au3D for SERS activity.
Effect of particle number ratio (AuNP:PS).

Peak Height at 1600 cm

-1

700

c

d

Blank
16 nm
22nm

600
500
400
300

10 µm

200
100
0

1nM

10nM

50nM

4,4'-Bipyridine concentration

Fig. 3. Optimization of Au3D for SERS activity.
Effect of Au diameter.

-1

Blank
600 nm
1400 nm

400
300
200
100
0

1nM

10 µm

Fig. 6. Changes in Au3D width in radial
direction depending on the particle number. (a)14
0.5×8.4×10
particles/l 14 (b) 8.4×1014

particles/l14(c) 2.5×8.4×10
5×8.4×10 particles/l.

particles/l (d)References:[1] T. Fukuoka, J. Jpn. Inst. Electron.
Packaging (Electronics Jisso Gakkai Shi),
13(3), 168-176(2010) (in Japanese).
[2] M. Suzuki, K. Nakajima, K. Kimura, T.
Fukuoka, and Y. Mori, Anal. Sci., 23(7),829-833(2007).
[3] Y. Mori, N. Shinohara, and T. Fukuoka,
International Workshop on Nanomechanical
Cantilever Sensors 2008, P48, 2008.

500

Peak Height at 1600 cm

10 µm

10 µm

10nM

50nM

4,4'-Bipyridine concentration

Fig. 4. Optimization of Au3D for SERS activity.
Effect of PS diameter.

Fabrication and characterization of three-dimensional
type micro magneto-impedance sensor
1

T. Yamamoto1, Y. Yoritama1, T. Uchiyama2, Y. Utsumi1 and A. Yamaguchi1
Laboratory of Advanced Science and Technology for Industry, University of Hyogo, Koto, Kamigori-gun, 6781205, Japan.
2
Graduate School of Engineering, Nagoya University, Chikusa, Nagoya, 464-8603, Japan.
Abstract
Fabrication and evaluation of a three-dimensional micro-scale magneto-impedance (MI) sensor
have been carried out. We present the detail of the fabrication process of the device and themeasurement result of the impedance of the sensor head. The measured characteristics indicatethat we succeeded the fabrication of the three-dimensional micro-scale MI sensor.

Introduction
In recent years, the people's concern about their health is increasing under the influence of aging society inadvanced nations. Physical changes caused by external factor will be offset by the action of the autonomic nerve
system. This indicates that the human health state depends on the autonomic nervous system. An un-invasive
healthy monitoring system is required for the estimation and control of each of health status. The system consistsof near-infrared spectroscopic devices for detecting the amount of substance inside blood and integrated
magnetometric sensors to  measure  the  dynamic  characteristics  of  human’s  circulatory  organ  system  as  one  of  the  function of the autonomic nervous system at the same time.The circulatory system response from themeasurement results enable us to create the mathematical model which relates the response with exogenous
stimulus. Therefore, health-maintenance medicine will be achieved by this model applied to the signal obtained
from the sensor.
We need the high sensitive sensor in order to achieve the model. The change in the high frequency
impedance of very soft ferromagnetic materials upon the action of external static fields, known as magnetoimpedance (MI) effect, has been intensively studied for magnetic sensor applications.[1, 2] The high sensitive
MI effect occurs when high frequency current is applied to the amorphous metal in which spin is arranged
circumferentially. The MI sensors using MI effect has been recently attracting attention for improved theresolution of up to 10-12 T [1], which can measure bio-magnetic field in range from 10-10 to 10-15 T. The
significant change in impedance is basically derived from the skin effect. The estimation of the high sensitivityof magnetic field is of great importance for the sensor application. The development of the general estimation
method for the only inductance component of impedance also provides an insight to understanding the physicalmechanism with respect to the relationship between the skin effect and micro- or nano-scale magnetization
structure.
Experiments and Results
In this study, integrated coil, made of gold Au, is fabricated using UV lithography and succeeding packaging
method to improve productivity. The Fe21.5Ni78.5 (Permalloy: Py) wire with thickness of 60 nm is prepared in thecoil. The devices were fabricated by building up SU-8 layers as shown in Fig. 1. The fabrication process is also
schematically illustrated in Fig. 1. Finally, one side of the device is covered with Kapton film for electricalinsulation. Its size is 1.5 mm in length, 1 mm in width, and the thickness is 35 Pm. The optical image of thedevice is shown in Fig. 2. In our device, the inductance component of impedance can be detected by not only thePy wire itself but also a pickup coil formed around the Py wire.
To evaluate the impedance of the device, we measured the impedance of the device as a function of thefrequency (from 100 Hz to 100 MHz) by using a MI sensor electrical circuit device. As shown in Fig. 3, theimpedance was rapidly increased with a frequency up to a 10 % when the frequency exceeded at about 20 MHz.
The change in the impedance is attributable to not the ferromagnetic resonance but the normal skin effectbecause the ferromagnetic resonance frequency is far higher than the measured frequency region.
Although further systematic investigation is necessary in order to perfectly understand the physicalmechanism and evaluate the MI effect, we have succeeded in fabricating a novel integrated MI sensor by means
of UV lithography fabrication technique. The implementation of high sensitive MI sensors can provide
biomedical monitoring system, car sensors and so on.

Fe-Ni Sensor headFig. 1 Schematic of fabrication process and device.

(a)

(b)

Fig. 2 Optical images of (a) the fabricated MI Sensor and (b) magnified coil region.

Fig. 3 The frequency dependence of the impedance of the fabricated MI sensor.
References[1] T. Uchiyama, A. Yamaguchi, Y. Utsumi., J. Magn. Soc. Jpn., 34(Japan, 2010).
[2] K. Mori., Magnetic Sensors (Tokyo, Japan, 1998).

Micro-Mirror Array Device for floating image
manufactured by Synchrotron radiation
T.Yamanea, S.Maekawab, I.Okadaa,c ,Y.Utsumia and A.Yamaguchia
Laboratory of Advanced Science and Technology for Industry, University of Hyogo, 3-1-2 Koto, Kamigori,
Hyogo 678-1205, Japanb
National Institute of Information and Communications Technology,3-5 Hikaridai, Seika, Soraku, Kyoto, Japanc
Nagoya University Synchrotron radiation Research center, Furocho ,Nagoya Chikusa-ku, Aichi 464-8603, Japana

Abstract
We propose a new imaging optics called the Dihedral Corner Reflector Array (DCRA) which is designed tomake the floating image. DCRA consists of numerous micro-mirrors placed perpendicular to the surface of
substrate. The micro-mirror array is implemented by the inner walls of minute square holes or the side ofminute square pillar. We can choose two types of the structure. The primordial is based on two reflections
by a pair of adjacent mutually perpendicular mirrors, i.e., a dihedral corner reflector. (S.Maekawa 2006.)
Although the principal of operation is based on reflection by mirrors, the device is also transmissive anddeflects light. Primordial of DCRA is not so complicated. However, it is too difficult to fabricate the DCRA
by usual machining because of high aspect ratio micromachining. Therefore, in this manuscript, wefabricated the device by deep X-ray lithography due to synchrotron radiation. The characteristics of thefabricated DCRA are evaluated by the optical transmission and reflection measurements.
Introduction
There are some basic imaging optics which can form areal image, such as convex lens, a concave mirror, anddiffraction optics (a Fresnel lens). For example, there aresystems which are based on the lens array of the GradedIndex Lens (GRIN) (H.Kita et al 1971), Roof Mirror Lens
Array (RMLA) (M.Kawazu et al 1985), and the stackingof various micro-lens arrays (R.Volkel et al 1996). These
have an optical axis and a specific focal length. Moving
an object closer to the optics, the real image forms farther
from it and is magnified. In contrast, imaging optics canform three-dimensional (3D) images without distortion.
An example of this is a plane mirror. However, as a plane
mirror can only form virtual images, the world in the
mirror is treated as fantasy.
The authors of this paper propose a new imaging optics
forming a real mirror image with the use of micro-mirrors.
We called this imaging optics as the Dihedral Corner
Reflector Array (DCRA).

(a)(b)
Figure 1 Operation mode of (a) two-dimensional- and (b)three-dimensional-dihedral corner reflectors.
The primordial of DCRA
The primordial of DCRA is based on mirror reflection.
Figure 1 describes the operation of dihedral cornerreflector. The reflection mode of DCRA is limited,

because incident light is reflected twice when passing
through a dihedral corner reflector. In the case of
two-dimension structure, an incident light from a lightsource “A” is reflected in the direction “B” parallel to thelight source “A” as shown in Fig. 1(a). Next, let us
consider that the incident light from “A” into a dihedral
corner reflector reflects two times at the mirrors anddeflects toward the point “B” in 3D structure as shown in
Fig. 1(b). Then, if the micro-mirrors are extremely small,the incident light passes through the substrate plane
toward the symmetric point for the light source. When we
prepare many dihedral corner reflectors on the substrate,
all the light from a light source is converged onto thereflection-symmetric point of the source. As a result, thearray of numerous dihedral corner reflectors, namely
DCRA, can realize the floating image. (S.Maekawa 2006)
Image-formation and precision of DCRA
Here, we postulate that the transmittance of DCRA is thepercentageofincident
light
throughthereflection-symmetric point. The transmittance is given by
where I is the ideal transmittance, R is reflectance of
micro-mirror, and T is the losses, which is defined as theattenuation of intensity of the incident light after passing
through the DCRA.
Reflectance of micro-mirrors is the most importantfactor in imaging by DCRA. In this study, we expect that
it is as close as possible to 100%. However, in the device,
the micro-mirrors placed perpendicular to the surface of
substrate. Therefore, no one can be polished after
manufactured.
Accordingly,
reflectanceofmicro-mirrors is determined during the creation of the
DCRA.
The perpendicularity of dihedral corner reflector plays
an important role on the resolution of the imaging, and itcauses the distortion of the image. The dependence of theperpendicularity of the wall of DCRA can be estimatedby using the simulation. This simulation enables us tocalculate that the ray trace through position of lightreflected by a line of plane mirrors from point light. Then,
we can choose the value of the number of the plane
mirrors, the distance of point light to the head mirror andthe taper of mirrors. If the planes of mirrors in the DCRA
are exactly perpendicular, all the reflected light by eachmirrors pass through the same position of the head mirror.
The floating image produced by the DCRA can be
estimated to be distorted up to 10 µm when the plane
mirrors have 1 minute taper.
Image resolution is determined by the dimension of thedihedral corner reflector. The higher resolution image canbe obtained, the smaller dihedral corner reflectors in the
DCRA are fabricated. However, the image produced by
the smaller DCRA will darken because the diffractive
component of the light increases.

Figure 2 Schematic of the DCRA device designed inthis study.
Table 1 Dimension of DCRA
Length of square side [µm]150
Pillar height [µm]300
Pitch [µm]25
Ideal transmittance [%]100
Aperture ratio [%]64.9
Perpendicularity [deg]90
Roughness [nm]10

radiation (SR). The fabrication process using the SR
enables us to fabricate the DCRA structure within thelimit of accuracy of about 1 nm. Figure 2 shows
schematic of dimensions of our DCRA device. As shownin Fig. 2, a dihedral corner reflector is made by a pillar
with square section.
The incident light through inside of pillars made ofPMMA in pillar patterned DCRA. Considering thePMMA refractive index, we design the aspect ratio(height/width) of our device is two in order to achievethat the theoretical value of light transmittance of ourdevice is expected to be 100%. The aperture ratio, namely
the portion of the opening, is determined by the pitch
between the reflectors. We estimate the effective fraction
transmitted of our device is 64.9% considering thecontribution of the aperture ratio. Expressed in anotherway, the brightness of the floating image is expected to be
64.9% with the respect to that of an object. The
dimension and desired values of DCRA are summarizedin Table.1.

Figure 3 Schematic of transmission-reflection ratio
measurement system.
is an angle between theperpendicular direction of the incident light axis andsample horizontal plane.
is an angle between theperpendicular direction of the light axis and detector.

(a)

(b)

Fabrication of DCRA
Polishing the micro-mirrors is easy if they are parallel tothe device surface. However, because micro-mirrors areperpendicular to the device surface in the DCRA, it is
impossible to polish them in pre- or post- processes.
Therefore, the micro-fabrication of high precision isrequired for the fabrication of DCRA. In this manuscript,
we fabricated the pillar patterned DCRA made of
Poly-methyl methacrylate (PMMA) by using synchrotron

Figure 4

Optical microscope image of (a) top view and(b) cross section of the pillars in our DCRA.

Length of square side [ȝP@(x) 150.92(y) 151.42

Pitch [ȝP@25.87

Pillar height [ȝP@326.78Perpendicularity[minute]

5.8

Results and discussion
Up to now, the criteria and evaluation method for theproperties such as the resolution and brightness of theimage produced by the DCRA have not yet been
established. In this study, we evaluate the characteristicsof the fabricated DCRA by measuring the dimension,
perpendicularity of the reflector, fractional transmitted
and reflection. The attenuation of brightness andreflection ratio are measured by transmission-reflection
ratio measurement system as shown in Fig.3.
Figures 4(a) and 4(b) show a typical optical
microscope image of top view and cross section of the
micro-pillars in the fabricated DCRA, respectively. The
measured average dimensions of the DCRA aresummarized in Table 2. The measured dimensions except
the perpendicularity are almost in good agreement withthe design dimensions. The perpendicularity of thefabricated pillars have about 6 minute taper. The
evaluation using the simulation indicates the taper
structure causes the distortion of 65 ȝP ZLWK UHVSHFW WR
the distance of light source. This distortion is serious forthe observation of a floating image formed by DCRA.
Next, the attenuation of brightness is evaluated by thetransmission-reflection ratio measurement system shownin Fig. 5. The measured fraction transmitted was about
40%, being in acceptable range of the design. As shownin Fig. 5, we can see a broad change from 400 nm to 600
nm in wavelength. The change corresponds to theabsorption derived from the discoloration of PMMA bySR.
Finally, the reflection ratio was evaluated by using thesame measurement system. Here, the coordinate system isdefined as shown in Fig. 3. In order to evaluate theangle dependence of the single reflection of the DCRA
at 700 nm in wavelength, we fixed the DCRA at theangle. The measured angle
dependence ofthe reflection is shown in Fig. 6. As shown in Fig. 6, tworeflection peaks are observed. The peak with the larger
amplitude (at about) corresponds to therefractive incident light. The other is the single reflectionof the light by the DCRA. If the ideal DCRA was
fabricated, we would obtain the single reflection peakatin this experimental setup. However, wefound the single reflection was extended in therange
betweenandbecause the reflected light was
spread by the distortion due to the taper. The actual
fraction transmitted is estimated to be 5.4% by
substituting the measured value into Equation (1). This
indicates that a dark floating image is formed by the
fabricated DCRA. However, we succeeded in forming thefloating image by the fabricated DCRA as shown in Fig.
7.
The improvement of fabrication process and evaluationof the DCRA will open the door to the novel imaging
devices.

100
80

absorption[%]

Dimension of the fabricated DCRA

60
40
20
0
400 500 600 700 800 900 1000

wavelength[nm]Figure 5

Absorption as a function of wavelength.

70
60
50

reflection[%]Table 2

40
30
20
10
0

0

18

36

54

72

angle[deg]Figure 6
DCRA.

The angle

dependence of the fabricated90Figure 7 A typical floating image is imaged by the
fabricated DCRA.
Conclusion
We proposed novel imaging optics with micro-dihedral
corner reflector arrays (DCRA) which can form areflection-symmetric image as a real image in the air. It
was fabricated by synchrotron radiation. We evaluatedthe fraction transmitted and single reflection of thefabricated DCRA by the optical measurement system.
Although the performance of the DCRA was not good,
the fabricated DCRA enables us to observe a floating
image. By comparing the simulation result with theexperimental evaluation, we can understand what worsen
the performance of the DCRA.
Our main work to improve imaging in the future is toincrease transmittance and establish the quantitative
measurement method of resolution and reflection ratio.
Reference[1] S.Maekawa. “Transmissive Optical Imagin Device
with micromirror Array” The international society for
Optical Engineering, Vol. 6392, 63920E-1, 2006.
[2]
H.Kita, I.Kitano, T.Uchida, and M.Furukawa,“Light-focusing glass fibers and rods,” Journal of theAmerican Ceramic Society 54, pp. 321-326, 1971.
[3] M.Kawazu and T.Inokuchi, “Imaging Device using
a roof micro lens array,” Applied Optics 24(24),pp.4300-4306, 1985.
[4] R.Volkel, H.Herzig, P.Nussbaum, and R.Dandliker,“Microlens array imaging system for photolithography,”
Optical Engineering 35(11), pp.3323-3330,1996.
[5] M.Ishikawa, “A proposal to create the impression ofa miniature garden, and the development of a glasses-freesmall 3d display”, Pioneer R&D 12(3), pp.47-58, 2003.
In Japanese.

Broadband noise spectroscopy of a magnetic wire
A. Yamaguchi1, K. Motoi2, H. Miyajima2 and Y. Utsumi1
1

Laboratory of Advanced Science and Technology for Industry, University of Hyogo, Koto, Kamigori, Ako,

Hyogo 678-1205, JAPAN
2

Department of Physics, Keio University, Hiyoshi, Yokohama, Kanagawa 223-8522, JAPANE-mail: yamaguti@lasti.u-hyogo.ac.jp
Tel: +81-791-0041

Abstract
We measured broadband magnetic noise spectrum induced in a single layered Ni 81 Fe 19 nano-scale
wire biased with a dc-current in a frequency range from 500 MHz to 8 GHz. The magnetic noise
spectra are recorded as a function of external magnetic field and dc-current. Experimental
measurement results and analytical calculations reveal that the noise generation is caused by thethermal magnetization fluctuation due to ambient temperature and Joule heating.

Introduction

The spin dynamics in a nano-scale magnet with a confined structure has gained increasing attention
over the last decades due to the scientific and technological interest. [1] To understand the mechanismof the spin dynamics from a microscopic perspective, the special instrumentality and measurement
system, such as magneto-optic Kerr effect, Brillouin light scattering and ferromagnetic resonance, arerequired until now. [1] Several electrical measurements that are suitable for investigating the spin
dynamics in nano-scale magnets and are extremely sensitive have been proposed recently. One of themis the homodyne detection of the resistance change induced by the spin-transfer torque and magnetic
fields. The magnetic noise measurement of a nano-scale magnet, in particular for giant
magnetoresistive (GMR) devices and tunneling magnetoresistive (TMR) devices, can be used as othertools. [2, 3] The GMR or TMR noise tests are nondestructive and can be applied to the read heads forthe magnetic hard disk drive. For diagnostic testing, we interested in the noise induced by the
spin-transfer torque, magnetic fields and thermal excitation. [2-4]This paper reports our investigation of broadband noise spectroscopy in a single layered Ni 81 Fe 19(Permmalloy: Py) wire.

Experiments and Results

The soft-ferromagnetic Py nano-scale wire is fabricated onto a polished MgO (100) substrate bymeans of high-resolution electron beam lithography with a standard lift-off technique. The thickness,
width and length of the prepared Py wire are 20 nm, 2.2 Pm and 100 Pm, respectively. The wire isplaced between the center strip-line of the coplanar waveguide (CPW) comprising Au conductive strip
with thickness of 100 nm. The optical micrograph image and schematic circuit diagram for broadband
noise measurement are shown in Fig. 1.
Figure 2 shows the homodyne detection spectrum (black solid line) [5] and the lock-in detection
noise spectrum (red solid line). It should be noted that the resonance frequency around 3.8 GHz of themagnetization fluctuation signal almost matches that of the homodyne detection spectrum, indicatingthat the origin of the noise signal induced by dc-current is the same as that of the homodyne detection
signal. We also measured the magnetic field dependence of the broadband noise spectra. As a result,
the resonance frequency correlates well with the ferromagnetic resonance frequency, and theamplitude of the noise signal at the resonance frequency decreases with increasing the static field.
These experimental results suggested that the measured noise signal is derived from themagnetization precession induced by the thermal fluctuation. The present experimental results are ingood agreement with the analytical solutions. [2-4] We believe this study provides not only theimportant physics on the fundamental limitation in the possibility of the scale-down size but also theimprovement in the read heads and in the radio-frequency devices.

Fig.1 Optical micrograph image of the Py wire and schematic diagram of the broadband noise measurement
circuit.

Fig. 2 Homodyne signal spectrum and broadband noise spectrum in magnetic field of 100 G at Ʌ = 45°.

References[1] B. Hillebrands and K. E. Ounadjela, Spin Dynamics in Confined Magnetic Structures (Springer, Berlin,2003), Vols. 1 - 3.
[2] N. Smith and P. Arnett, Appl. Phys. Lett. 78, 1448 (2001).
[3] K. B. Klaassen, J. C. L. van Peppen and X. Xing, IEEE Trans. Magn. 93, 8573 (2003).
[4] V. Safonov and N. Bertram, Phys. Rev. B 65, 172417 (2002).
[5] A. Yamaguchi, K. Motoi, A. Hirohata, H. Miyajima, Y. Miyashita, and Y. Sanada, Phys. Rev. B 78,
104401 (2008).

Defect Characterization of an EUV Mask using a Coherent
EUV Scatterometry Microscope
Tetsuo Harada1,2, Masato Nakasuji1,2, Akifumi Tokimasa1,2, Yutaka Nagata2,3, Takeo Watanabe1,2, and Hiroo
Kinoshita1,2
1 Center for EUV Lithography, Laboratory of Advanced Science and Technology for Industry, University of
Hyogo, Kamigori, Hyogo 678-1205, Japan
2 Core Research for Evolutional Science and Technology, Japan Science and Technology Agency, Kawaguchi,
Saitama 332-0012, Japan
3 Laser Technology Laboratory, RIKEN, Wako, Saitama 351-0198, Japan
Abstract
On extreme-ultraviolet (EUV) masks, phase structures such as bumps or pits on the substrate orparticles buried in the multilayers can form printable defects at EUV exposure tool. Property ofthese defects is required for mask repair by defect hiding and compensation methods using theabsorber pattern. We have developed a coherent EUV scatterometry microscope (CSM) to observe
EUV masks, which uses a simple lensless system to record a diffraction image from mask patterns.
We introduce preliminary observation results for programmed phase defects. We evaluated thedefect width and height from the diffraction images, and the detection limit of the CSM systemreached a width of 220 nm. To characterize small defects, we proposed a micro-CSM system that
focused to the illumination onto the defect with a 100 nm diameter. The diffraction image recordedby the micro-CSM system provides raw defect data, which is essential for defect compensation.
Introduction
In extreme-ultraviolet (EUV) lithography,
defect-free mask production is one of the criticalissues for high-volume manufacturing. A mask is amaster pattern for a semiconductor device, andthere must be no defects on this mask. In EUV
lithography, the EUV mask is a reflective typemask, unlike the transparent-type mask used forconventional 193 nm lithography. The EUV mask
is coated with a Mo/Si multilayer, and an absorberlayer, in which patterns are printed to form adevice pattern. However, phase structures such as
bumps or pits on the substrate or particles in themultilayers can form printable defects. For
example, a shallow structure of 1 nm on thesurface of a mask substrate causes a large
reflection phase shift of 53° at EUV wavelength.
As a result, this buried defect is printable.1-6)
Buried defects can be detected efficiently at themask blank stage of manufacture, which is justbefore the deposition of the absorber layer. The
Selete and EIDEC groups have developed an
actinic blank inspection (ABI) tool to detect phase
defects.7-10) The ABI tool is a dark-field EUV
microscope
composedofadischarge-produced-plasma
sourceand
Schwarzschild optics, which collects scattered
EUV light from buried defects to form a dark-field
image on a charge-coupled-device (CCD) camera.
Because the defect signal is integrated in a
dark-field, the ABI tool has a good signal-to-noise(S/N) ratio for the detection of defects.
Current EUV masks do not satisfy defectdensity requirements.11,12) As a result, defect hiding
and defect compensation methods have also been
proposed,13,14) which work by modifying theabsorber pattern to compensate the aerial image.
Detailed defect information, such as defectposition on the mask, defect size, and phase
distribution, is necessary for the compensation
process. However, the ABI tool is specificallyintended for defect detection, for which themagnification requirement is not high. The spatial
resolution is determined by the CCD pixel size,
where one pixel integrates the scattering signal
from a 500×500 nm2 region on the mask. It is thus
difficult to use the ABI tool to characterize thephase defect information. In this study, weobserved the phase defects using a coherent EUV
scatterometry microscope (CSM), which is alensless type of microscope.15-19) The CSM records
the diffraction from the mask directly using a CCD
camera. We discuss the requirements for a defectcharacterization tool based on the preliminary
observation results for programmed defects. We
also propose a micro-CSM system for defectcharacterization, which focuses the illumination
onto the defect with a 100 nm diameter.
Experiment
We observed the phase defects using the CSM
system shown in Figs. 1 and 2. The CSM system
was installed at the BL-3 beamline of the
NewSUBARU synchrotron radiation facility,20)
which uses a bending magnet as a light source.
Two toroidal mirrors collimate the white light into
the CSM system. Figures 1 and 2 show aphotograph and a schematic view of the CSM
system, respectively. A pinhole with a 5 Pm
diameter is exposed with the collimated EUV
beam and the beam diameter is then reduced to
improve the spatial coherence. A concave sphericalmirror and a plane turning mirror are then used toreflect the beam onto the EUV mask, and thus thepinhole image is relayed to the mask. The radius ofcurvature of the concave mirror is 200 mm, andthe distance from the pinhole to the concave mirror
is 200 mm, which is the same as the distance fromthe concave mirror to the mask. The mirrors arecoated with 40 pairs of Mo/Si multilayers.
Diffraction from the mask is recorded using a
back-illuminated CCD camera. The CCD surface
is placed parallel to the mask surface. The imaging
area is 27.6×27.6 mm2, and contains 2048×2048
arrays of imaging pixels with an area of 13.5×13.5
Pm2. The angle of incidence from normal is 6° on
the EUV mask, which matches the angle used incurrent EUV lithography scanners. The distancefrom the mask to the CCD camera isapproximately 100 mm, which is equivalent to anumerical aperture (NA) of 0.14. The estimatedspatial resolution is 59 nm.
A phase defect scatters EUV light illumination,
where the signal depends on the phase distribution.
When using conventional imaging optics, thisphase distribution is recorded as a small dark spot
on the detector caused by destructive interference.
High magnification is required to characterize thedefect. In contrast, the CSM can record thescattering signal directly, including the complex
amplitude information of the defect. We havesuccessfully reconstructed edge structure ofline-and-space pattern from these scattering signals
using a coherent diffraction imaging method.21-27)
We have also succeeded in reconstructing both anintensity image and a phase image.19)
The sample mask was a blank EUV mask,
which contained programmed bump structures ona glass substrate. The bumps were located with a
10 Pm pitch. The bump height was 7 nm, and thebump width was varied, ranging from 70 to 420
nm, with a square shape.

Fig. 1 Photograph of the CSM system. The arrows
show the light path of the synchrotron radiation.
The CCD camera records diffraction from the
EUV mask pattern.

Fig. 2 Schematic view of the CSM system.
Results
Figure 3 shows a diffraction image with aphase defect recorded using the CSM. The
exposure time was 1,000 s. The intensity is shownin log scale. The defect was 420 nm wide and 7 nm
high, as measured by atomic force microscopy(AFM). This defect had a truncated-pyramid shapewith slope width of about 70 nm. The strong
diffraction signal around the defect center wasfrom the illumination. The Fraunhofer diffraction
from the 5-Pm-diameter entrance pinhole wasrecorded at the center position, as shown in Fig. 3.
The illumination profile was asymmetric, because
the small turning mirror limited the illumination
pupil size. The center illumination signal was
saturated because of the long exposure time, andthe intensity was estimated to be 8.8×105 counts
from other data with shorter exposure times.
Because the cross-shaped diffraction signal aroundthe illumination came from the defect, the defectshape was determined to be a square. The
diffraction signal intensity was about 30 counts,
which was 10-4 times weaker than the intensity at
the illumination center. The defect width wasestimated to be about 430 nm from the diffraction
width of the crossed line, which corresponded wellwith the AFM value. The defect height wasestimated to be 6.5 or 7.0 nm from the diffraction
intensity ratio of the center to the crossed parts.
The reflection phase change of the height was
equal to 13.0 or 14.0 nm, which was a differenceof 0.5 nm (0.23 rad) from the 13.5 nm EUV
wavelength. Thus, the estimated height also
corresponded well with the AFM value. We
therefore successfully evaluated the defect widthand height precisely using the CSM system.
Figure 4 shows diffraction images of defects
with widths of (a) 420, (b) 220, and (c) 130 nm,
and image (d) without a defect. The intensity was
shown on a linear scale. All the defect heights
were about 7 nm. The defect of 220 nm width also
had a truncated-pyramid shape. Thus, the slope
widths of (a) and (b) were about 70 nm at bothsides, which was measured by AFM. That of the
130 nm-wide defect had a Gaussian shape. At thedefect width of 420 nm shown in Fig. 4(a), thediffraction shape was easily recognized as a cross.
However, because the diffraction spread to allFig. 3. Diffraction image with a programmed phase
defect with 420 nm width and 7 nm height. The
intensity is shown in log scale.

Fig. 4. Diffraction images of programmed phase
defects of (a) 420, (b) 220, and (c) 130 nm width, and(d) an image without a defect. The intensity is shown
on a linear scale.
35
Defect Width
420 nm
220 nm
130 nmNo Defect30
Signal (counts)

areas of the image of the 220 nm defect shown in
Fig. 4(b), the defect shape could not be recognizedwith certainty. For the 130 nm defect, thediffraction intensity was almost the same as that of
the sample without the defect. This signal was
found to be speckle diffraction from the substrateroughness, which overlapped and hid the defectsignal in the background. Figure 5 shows thediffraction signal profile of the indicated area
shown in Fig. 4(a) as a white square. The centersignal of the diffraction profile included the
speckle noise signal of the fringed shape. The
outside impulse signals were caused by the CCD
camera noise. The profile of the 130 nm defect(dark-gray solid line) was similar to that of theimage with no defect (dotted line), because thesignal from such a small defect was hidden by the
speckle noise.
The speckle noise was observed in the blankarea with this mask. However, speckle noise was
not observed in the other mask shown in Fig. 6.
The exposed region was also a blank region
without defects, where no speckle noise wasrecorded. The speckle signal was thus strongly
dependent on the surface roughness, and would
therefore degrade the detection limit size andprecision of the defect characterization of the CSM
system. George et al. reported that this speckle
noise affects the line edge roughness.28) As a result,the surface should be smooth not only for
multilayer reflectivity, but also for the aerial image
quality. From the point of view of roughness
evaluation, the CSM system was able to evaluate
the actinic surface roughness of mask blanks
precisely because it recorded the substrate speckle
clearly. In comparison with another method using aphotodiode detector29,30), the CSM can record thetwo-dimensional speckle profile with a better S/Nratio, and evaluate the effect of speckle on theaerial image.

25
20
15
10
5
0
0

200

400
600
Position (pixel)

800

1000

Fig. 5. Intensity profile of the diffraction signals forthe defects. The horizontal axis indicates the image
position shown in Fig. 4(a).

Fig. 6. Diffraction image of a mask blank without
defects. There is no speckle noise signal.
Discussion
4.1 Concept of micro-CSM system
The CSM system can evaluate defect properties

without any influence from the imaging optics.
The CSM measured the defect width and heightfrom the diffraction signals. However, small defectsignals were hidden by the speckle noise because
the defect signal was weak relative to the strong
speckle noise from the surface roughness. Also, theillumination signal was 104 times stronger than thedefect signal, making bright-field observationdifficult. To minimize the noise and maximize thedefect signal intensity, the illumination size should
be as small as the defect size, which improves thedefect-to-illumination size ratio. Thus, we propose
the micro-CSM system shown in Fig. 7. The
micro-CSM system has almost the same optics as
the CSM system. The specific additional
component in the micro-CSM is a Fresnel zone
plate (FZP) that focuses the illumination onto asmall phase defect. The FZP has an off-axis zone
aperture, as shown in Fig. 7. Also, the diffraction
from the defect transmits a rectangular aperture to
the FZP membrane, which is recorded with a CCD
camera directly. The target defect size of the
micro-CSM system is 20 nm in width and 1 nm inheight.

Fig. 7. Schematic view of micro-CSM system.
Monochromatized EUV light is focused onto a defectby an off-axis Fresnel zone plate.
4.2 Simulation of diffraction intensity profile
We simulated the diffraction signal from thedefect with various illumination sizes to optimize
the micro-CSM system. This simulation was basedon scalar diffraction theory. The simulation
conditions are as follows. The working wavelength
was 13.5 nm. The illumination was focused using
optics with an NA of 0.17. The angle of incidence
was normal. The reflection from the multilayers on
the substrate was assumed to be a reflection from asingle layer for simplicity. The phase defect had asymmetrical circular shape, and a top-hat phase
distribution. For speckle noise calculations, thereflection layer had a surface roughness of 0.15 nm(rms).
Figure 8 shows diffraction images from a phase
defect with a diameter of 50 nm and a height of 1
nm. The illumination sizes were varied, withdiameters of (a) 1 Pm and (b) 100 nm. The
intensity is shown in log scale. The maximum NA
position of the image was 0.5. The strong signal at
the center originated from the illumination. The
weak signal of the outside ring was a diffraction
signal that came from the defect. For the
1-Pm-diameter case, the speckle noise overlaps thedefect signal. For the 100 nm case, there was nospeckle noise, and the defect signal was recorded
clearly. The intensity profiles of these images areshown in Fig. 9. The horizontal axis indicates the
NA position at the detector, and the vertical axis
indicates the signal intensity. The NA position
corresponds to the diffraction angle. The intensitiesof the 1-Pm- and 100-nm-diameter cases werenormalized for the same illumination intensity. In
the 1 Pm case, the illumination peak signal was
two orders stronger than that in the 100 nm case,while the defect signal was two orders weaker. The
signal range spanned seven orders of magnitude,from 10-5 to 102. Because a typical CCD camera
has a dynamic range of 4 orders of magnitude, it isdifficult to record the defect signal using a CCD
camera. Also, the speckle signal overlapped thedefect signal, which was the same as that shown in
Fig. 5. In the 100-nm-diameter case, theillumination and diffraction signal were recordable
within three orders of magnitude, and no speckle
signal was recorded. We thus chose theillumination size of 100 nm for the micro-CSM
system, allowing the characterization of the defectusing the CCD image.
We also simulated the diffraction signal profile
from various sizes of defects with the
100-nm-diameter illumination. Figure 10(a) shows
the diffraction signals from a defect with various
heights ranging from 0 to 3 nm, while the width
was fixed at a diameter of 50 nm. Figure 10(b)shows the diffraction for various diameters,
ranging from 0 to 60 nm, while the height was
fixed at 1 nm. The horizontal axis indicates NA
positions at the detector same as Fig. 9. The
illumination was assumed to have a top-hat
intensity distribution for simplicity. Because theillumination size and the defect size werecomparable for these conditions, the center signal
decreases over 10% by destructive interferencewith the shallow 1-nm-height defect. Under these
conditions, the defect position was detectable fromthe intensity change of the illumination signal.
This was very useful for location of the defectposition. Because the ABI tool has a low spatial
resolution of 500 nm, scanning of the illumination
using the micro-CSM system is necessary tocharacterize defects that are detected by the ABI
tool. The diffraction profile for a tiny defect with awidth of 20 nm was clearly different to the
no-defect case. Thus, the detection limit of a defectsignal using the micro-CSM is better than a defectwith 20 nm width and 1 nm height, if the mask has

a low surface roughness of 0.15 nm (rms) and thesensor noise is negligible. Because the diffraction
signals are very sensitive to the defect height andwidth, the micro-CSM can characterize the defectproperties precisely.

Fig. 8. Calculated diffraction images with illumination
diameters of (a) 1 Pm and (b) 100 nm. The defect has
50 nm diameter and 1 nm height. The substrate has
0.14 nm (rms) surface roughness.
103

Intensity (arb. unit)

102
101
100

Focus size
I100 nm
I1 Pm

10-1
10-2
10-3
10-4
10-5
10-6
-0.5 -0.4 -0.3 -0.2 -0.1 0.0 0.1 0.2 0.3 0.4 0.5
Numerical Aperture

Fig. 9. Intensity profiles of the calculated diffraction
images shown in Fig. 8.

Fig. 10. Diffraction intensity profile with defects withvarious (a) widths and (b) heights.
Conclusions
Programmed phase defects on EUV mask
blanks were observed using the CSM system. The
CSM successfully detected phase defects down toa width of 220 nm, and we evaluated the defectwidth and height precisely for the 420 nm defect.
This defect property information is important for
repair using defect hiding and compensation
methods with absorber pattern modulation.
However, because the illumination diameter was aslarge as 5 Pm, the defect signal was too weak. Also,
the speckle noise signals from the substrates hid
the defect signals for defect sizes smaller than 200
nm. We therefore proposed the micro-CSM system,
which focuses the illumination onto the defect witha 100 nm diameter. Simulation results show thatthe micro-CSM system can record the diffraction
signal clearly from a defect with a diameter of 20
nm and a height of 1 nm. As a result, themicro-CSM can characterize the defect properties.
In a future work, we will construct the micro-CSM,
and collect diffraction images from various
programmed defects and actinic defects. The
database relations between the ABI signals and themicro-CSM signals will help to enhance the ABI
performance. The diffraction images recorded
using the micro-CSM provides raw defect data,
which is essential for defect compensation.
Acknowledgements
This work is a part of re-contracted researchfrom the EUVL Infrastructure Development Center(EIDEC). EIDEC programs are supported by the
New Energy and Industrial Technology
Development Organization (NEDO).

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[26] P. Thibault, M. Dierolf, A. Menzel, O. Bunk, C. David, and F. Pfeiffer: Science 321 (2008) 379.
[27] Y. Takahashi, A. Suzuki, N. Zettsu, Y. Kohmura, Y. Senba, H. Ohashi, K. Yamauchi, and T. Ishikawa:Phys. Rev. B 83 (2011) 214109.
[28] S. A. George, P. P. Naulleau, I. Mochi, F. Salmassi, E. M. Gullikson, K. A. Goldberg, and E. H.
Anderson: J. Vac. Sci. Technol. B 28 (2010) C6E23.
[29] N. Kandaka and K. Murakami: PF News 26 (2008) 22 [in Japanese].
[30] M. Hosoya, N. Sakaya, O. Nozawa, Y. Shiota, S. Shimojima, T. Shoki, T. Watanabe, and H. Kinoshita:
Jpn. J. Appl. Phys. 46 (2007) 6128.

Chemical Reaction Analysis of EUV CA Resist using SR
Absorption Spectroscopy
Takeo Watanabe, Yuichi Haruyama, Daiju Shiono*, Kazuya Emura,
Takuro Urayama, Testuo Harada, and Hiroo Kinoshita
Center for EUVL, Laboratory of Advanced Science and Technology for Industry,
University of Hyogo
3-1-2 Kouto, Kamigori, Ako-gun, Hyogo 678-1205, Japan* Tokyo Ohka Kogyo Co., Ltd.
1590 Tabata, Samukawa, Koza, Kanagawa, 253-0114, Japan

It had been reported that tri-phenysulfonium cyclo(1,3-perfluoropropanedisulfone) imidate(TPS-IMIDATE) as a photo acid generator has approximately four times faster sensitive rather
than tri-phenysulfonium perfluorobutanesulfonate (TPS-PFBS) under the EUV exposure. In thispaper, we discussed the differences of the sensitivity and the chemical reaction between
TPS-IMIDATE and TPS-PFBS, on the basis of the EUV-induced analysis of the SR absorption
spectroscopy. From the analysis of the SR absorption spectroscopy, F and C atoms in the anion of
TPS-IMIDATE decomposed rather than that of TPS-PFBS. The sensitivity advantage of
TPS-IMIDATE might own to the anion decomposition reaction. The anion decomposition reaction
might be originated to the photo-excitation of the photoacid generator. The anion of
TPS-IMIDATE decomposed to smaller molecule and the sensitivity becomes higher.
Keyword: EUVL, chemically
amplified resist, photoacid generator,
decomposition of anion of PAG, SR absorption spectroscopy

1. Introduction
Extreme ultraviolet lithography (EUVL) [1] is apromising lithographic technology which should
begin to transfer to the production line forsemiconductor electronics from the 25-nm nodearound 2013. The first top issue of EUVL is toachieve the EUV source power of 180 W at theintermediate focus position, when the resist
sensitivity is assumed to be 10 mJ/cm2. If the muchhigher sensitive resist can be performed, the EUV
source power could be relaxed. In addition, thethird issue of EUVL is to develop the EUV resist
which has the sensitivity of 10 mJ/cm2 and the line
width roughness (LWR) of smaller than 2 nm (3V)
because of the trade of relationship between the
resolution, the LWR, and the sensitivity, so called“RLS” trade off. The photon number which
requires for the patterning in EUV isapproximately one order smaller than those in KrF

and ArF lithography. Thus, in order to achieve low
LWR, the yield of the acid should increase. In
addition, to achieve the high sensitivity and the
low LWR, the acid production yield from thephotoacid generators in the chemically amplifies
resist [2-4] should increases.
In focusing, the production acid yield, thechemical reaction analysis on the basis of EUV
photo irradiation should be performed in the basic
study.[5-9]In the previous report, for resist A, the peak at
the absorbance at 1156 cm-1 in the fouriertransform infrared (FT-IR) spectra increased after
EUV exposure.[7-9] However, there was nochange in the FT-IR spectra of resist B before andafter EUV exposure. As a results of the electron
orbital calculation using perturbation theory by thesoftware code Gaussion03 [10], the peak at
approximately 1156 cm-1 in FT-IR spetra of resist
A corresponds to C-F bonding of the anion of

TPS-IMIDATE.
As a result, the outgassing
measurements
and
the
FT-IR
spectrameasurements indicated that the EUV-induced
reaction of TPS-IMIDATE occurred more
efficiently than that of TPS-PFBS. To clarify thedifference of the anion decomposition, the analysis
using SR spectroscopy is performed. This paper
focused on the chemical reaction analysis of themodel chemically amplified resists by the SR
absorption spectroscopy.

Table 1. Model resist material
SampleResist A
Resist B
Resin
n

m

O
O

OH

PAG
O2S
S+ -N
O2S

CF2
CF2

S+ C4F9SO3-

CF2

2.Experimental
Solvent

2.1. Materials

PGMEA

2.3. SR Absorption Experiment

The model resists which were employed inthis study are shown in Table 1. The resists A
and B is employed poly (hydroxystyreneco-t-butylacrylate) as the base polymer, andpropyleneglycol
monomethyletheracetate(PGMEA) as a solvent. Resists A and B
employed triphenylsulfonium cyclo(1,3- perfluoro
propanedisulfone) imidate (TPS-IMIDATE) andtriphenylsulfonium
perfluorobutanesulfonate(TPS-PFBS) as the photoacid generator,
respectively.
The PAG content isapproximately 30 wt% of the base polymer toincrease the detection S/N ratio of the anion
decomposition species from the PAG in the
SR spectroscopy measurement before andafter EUV exposure. The resist solution was
spin coated on a 4-inches silicon wafer to be a
50-nm-thickness. The film thickness wasmeasuredbyNanometrics
6100A(NANOmetrics). The prebake conditions was
carried out on a hot plate at the temperature of
130ºC in the time period of 90 s.

TheSR
absorption
spectroscopy
measurements were performed at the end
station of the BL07B beamline at the
NewSUBARU synchrotron radiation facility.
The short undulator was employed as a lightsource of this beamline. The configuration
setup of the BL07B is shown in Fig.1. The
beamline consists of three glancing mirrossuch as M0, M1 and M2, the monochromater(G), the entrance (S1) and exit (S2) slits andthe end station exposure and analyzing
chambers. The loadlock chamber was adapted
to these chambers to exchange the sample.
The photography of the BL07B beamline andthe end station are shown in Figs.2(a) and 2(b).
The variable line spacing plane gratings(VLSPG) were employed as monochromator.
Three density types such as 600, 1200, and2400 lines/mm were installed in the
monochromator vacuum chamber. The photon
energy region is from 80 eV and 800 eV in theFig. 1 System configuration of the BL07B beamline.

SR spectroscopy. The exit slit size is 20
Pm(H)×20 Pm(V) and the SR light spot sizeon a sample is 1 mm(H)×1 mm (V). Theenergy resolution E/ ' E is approximately 1000.
The photon flux of the photon energy of 91.8
eV (O=13.5 nm) is approximately 3.0×10 11
photons/s/100mA.
The absorption signal was obtained from theratio of the photocurrent from the sample to thephotocurrent from the gold mesh. The total energy
resolution was ᨺ0.5 eV. The photocurrent wasmeasured by the electrometer (6514, Keithley).
For the absorption measurement of F 1s
core level, the measured energy region is685-735 eV and 2400 lines/mm VLSPG was
employed with the undulator gap of 52.0 mm.
For the absorption measurement of C 1s corelevel, the measured energy region is 280-330
eV and 1200 lines/mm VLSPG was employedwith the undulator gap of 48.0 mm. For theabsorption measurement of N 1s core level,
the measured energy region is 390㨪440 eV
and 2400 lines/mm VLSG was employed withthe undulator gap of 51.0 mm. The electron
current generated on the sample is measured
in the SR absorption experiment during theSR light exposure.

3. Results and Discussions
3.1. SR Absorption Spectra
SR absorption spectra of F 1s core level at thephoton-energy ranges of 685-735 eV of resists
A and B are shown in Figs. 3 (a) and 3(b),respectively. For resist A, the absorption at
the photon energy of 697 eV decreased when
the EUV exposure dose increased and theabsorption disappeared at the EUV dose of
104 mJ/cm 2 . For resist B, the absorption at thephoton energy of 697 eV decreased when the
EUV exposure dose increased. However, theabsorption signal remained at the EUV
exposure dose of 104 mJ/cm2 . The EUV
exposure dose dependency of the absorptionof F atoms at the photon energy of 697 eV isshown in Fig. 4. The decomposition of F
atoms in the anion of the TPS-IMIDATE haseasier to decompose than that of TPS- PFBS.
As the results, F atoms decomposition
speed of the TPS-IMIDATE is faster than thatof the TP- PFBS.

a)

a)

b)

Fig. 2 Photographs of (a) BL07B beamline and (b) end
station.

b)

Fig. 3 Absorption spectra of F 1s core level in theanions of (a) TPS-IMIDATE and (b) TPS- PFBS.

much higher than that of resist B.
Resist A

Intensity (arb. unit)

Resist B

S-bondinga)V-bonding050

Dose (mJ/cm2)

100

Fig. 4 EUV exposure dose dependency of theabsorption of F 1s core level at the photon energyof 697 eV.

Absorption spectra of C 1s core level at thephoton-energy ranges of 280-330 eV of resists
A and B are shown in Figs. 5 (a) and 5(b),respectively.
For resist A, the absorption at the photon
energy of 287 eV had no change. Thus, itmeans that the S-bonding of the benzyl groupof the base polymer has no change. However,
the absorption at the photon energy of 290 eV
decreased after the EUV exposure. It meansthat the anion of the V-bonding of the anion of
TPS-IMIDATE decomposed under the EUV
exposure.
For resist B, the absorption at the photon
energy of 290 eV had no change before andafter the EUV exposure. It means that theanion of the V-bonding of the anion of
TPS-IMIDATE decomposed under the EUV
exposure.
Absorption spectra of N 1s core level at thephoton-energy ranges of 390-440 eV of resist
A is shown in Fig.6. the absorption at thephoton energy of 405 eV decreased under the
EUV exposure. And the photo-energy of 403
eV increased under EUV exposure and thechemical shift was observed. It means that N
atoms in the anion of TPS-IMIDATE
decomposed and reconstructed under the EUV
exposure.
As the results of the SR spectroscopy, theV-bonding of the anion of TPS-IMIDATE
decomposed to the small molecule size andthe acid diffusion length might become large.
Thus the sensitivity of resist A might become

S-bondingb)

V-bondingFig. 5 Absorption spectra of C 1s core level of theanions of (a) TPS-IMIDATE and (b) TPS- PFBS.

Fig. 6 Absorption spectra of N 1s core level in the
TPS-IMIDATE anion.

4. Conclusion
As the analysis results of the SR
spectroscopy measurement, it was confirmedthat the decomposition reaction begin to occur
by the absorption by the EUV photons at F

atoms in the anion of TPS-IMIADTE and theanion molecular size becomes smaller than theoriginal one. However, for resist B, only F
atoms in the anion of TPS-PFBS decomposed
and the molecular size of the anion did not
dramatically change. Since the anion size of
TPS-IMIDATE might be much smaller thanthat of TPS-PFBS, the acid diffusion length inresist A might become larger than that in resist
B.
To achieve the low LWR, it had introduced
generally that the diffusion length of PAG
should decreased by increasing the molecularsize of the anion of PAG. However, for theanion PAG which include F atoms, from theresults of the SR spectroscopy, F atoms might
decompose under EUV exposure. Therefore,
since the anion of the PAG which includes F
atoms should be analyzed carefully if thedecomposition reaction of the anion of PAG
would occur or not.
The SR absorption spectroscopy might be a
powerful analysis method to analyze thedecomposition reaction of the anion of PAG.
To satisfy the specification of the EUV resist
which require for high volume manufacturing,
all the chemical reaction should be taken inaccount.

References
1. H. Kinoshita, K. Kurihara, Y. Ishii and Y.
Torii, J. Vac. Sci. & Technol., B7 (1989) 1648.
2. H. Ito, C. G. Willson, and J. M. J. Frechet,
Digest of Tech. Papers 1982 Symp. VLSI Tech.,(1982) 86.
3. H. Ito and C. G. Willson, Polym. Eng. Sci., 23(1983) 1012.
4. H. Ito, G. Breyta, D. Hofer, R.
Sooriyakumaran, K. Petrillo, and D. Seeger, J.
Photopolym. Sci. Technol., 7 (1994) 433.
5. T. Watanabe, K. Hamamoto, H. Kinoshita, H.
Hada and H. Komano, Jpn. J. Appl. Phys. 43(2004) 3713.
6. H. Hada, T. Watanabe, H. Kinoshita and H.
Komano,”Outgassing Analysis in EUV Resist”
J. Photopolym. Sci. Technol., 18 (2005)
475.
7. T. Watanabe, H. Hada, S. Y. Lee, H. Kinoshita,
K. Hamamoto and H. Komano, Jpn. J. Appl.
Phys., 44 (2005) 5866.
8. Takeo Watanabe, Hideo Hideo, Hiroo
Kinoshita, Yuzuru Tanaka, Hideaki Shiotani,
Yasuyuki Fukushima and Hiroshi Komano,
Proc. SPIE, 6153 (2006) 615343-1.
9. Takeo Watanabe, Hideo Hada, Yasuyuki
Fukushima, Hideaki Shiotani, Hiroo Kinoshita
and Hiroshi Komano, Synchrotron Radiation
Instrumetation: Ninth International Conference,
AIP 879 (2007) 1470.
10. Gaussian03 electron orbital calculation
softwareisinformedin
URL:http://www.gaussian.com/home.htm.

Plasma-Debris Sputter Resistant X-ray Mirror
S. Amano, T.Inoue, T.Harada
LASTI/UH
Abstract
A diamond-like carbon (DLC) mirror, used as a grazing incident mirror in a plasma X-ray source,
exhibits a high resistance to plasma debris sputtering. The erosion rate due to plasma debris
sputtered at the incident debris angle of 20° was measured using a laser-produced Xe plasma
source developed by the authors. The results indicate that the DLC film has a 5- and 15-fold higher
sputtering resistance compared to films made of the traditional mirror materials Ru and Au,
respectively. Because the DLC mirror retains a high sputtering resistance to Sn ions, it may beeffective in Sn plasma source applications. We conclude that a grazing incident X-ray mirror
coated with DLC can be of use as a plasma debris sputtering resistant mirror.
Plasma X-ray sources, which produce radiationfrom laser-produced plasmas (LPP) or dischargeproduced plasmas (DPP), find use in various
industrial applications. However, along with Xrays, the plasmas in these sources emit debris
consisting of ions, neutral atoms, various
fragments, vapor and so forth. Such debris
damages mirrors located near the plasma, quickly
degrading their reflectivity. Because the amountof plasma debris increases in proportion to the Xray generating power, the debris problem is a
critical issue in high-power plasma sources forindustrial applications. We propose a new
approach to mitigate debris effects in plasma Xray sources, namely the use of debris resistantmirrors that suffer reduced debris damage ascompared with traditional mirrors.
In our lab, we developed a laser-produced plasma
X-ray source (LPX), which employs a solid Xetarget. This device has demonstrated continuous
X-ray generation at 5–17 nm with an average
power of 20 W. A diamond-like carbon (DLC)
coating, also developed in our laboratory, wasdeemed a good candidate for the mirror material,owing to its high hardness. In this work, wemeasured the erosion rate due to debris sputteringin the plasma source. The results were comparedwith similar experiments with mirrors coated with
Ru and Au films, which are typically used as
mirror coating materials.
The LPX consists of a system that supplies a solid
Xe-target and a drive laser. The target supply
system comprises a cylindrical drum filled withliquid nitrogen, so its copper surface is at liquid
nitrogen temperature. Xe gas blown onto thissurface condenses to form a solid Xe layer. The
solid Xe layer-coated drum rotates about thevertical axis, simultaneously moving up anddown vertically during rotation. The resultant
spiral motion ensures that a fresh target surface iscontinuously supplied for every laser shot. The
drive laser is a slab laser with an average powerof 100 W and a pulse repetition rate of 320 Hz.
The laser pulses (λ = 1064 nm) with a pulse widthof 20 ns are focused on the solid Xe-target,
continuously producing plasma.
We used a quartz crystal microbalance (QCM) tomeasure the erosion rate of the DLC films after
sputtering with Xe plasma debris from the LPX.
As such debris bombards a test film that is coatedonto the QCM, atoms are ejected from the surfaceof the film, changing the resonant frequency of
the QCM. Mass loss in the film can be deduced
from this frequency change, and erosion rates ofthe film can be calculated directly. The
experimental setup is shown in Fig.1.

Figure 1. Experimental setup.
The drum target system and the QCM were
installed in a vacuum chamber (pressure of 0.2Pa),
while drive laser pulses coming through awindow were focused perpendicularly onto thetarget by a lens. The coated QCM was placed 73
mm from the plasma at a 45° angle with respect
to the incident laser beam. Its sensor surface wastilted at a 20° angle with respect to the incident
debris axis, thus forming a grazing incidence
mirror. Test films coated on the quartz sensors
consisted of DLC, Ru and Au, with a coating
thickness of 500, 100, and 100 nm, respectively.
After laser irradiation of the films for 2–10 min at
320 Hz, we used the QCM to monitor total
erosion rates during extended multi-shot plasma
operation.

The measured erosion rates of the DLC, Ru andAu films at an incident debris angle of 20° areshown in Fig. 2. We see a decreased erosion ratewith increasing binding energy, and the erosion
rate ratio is DLC : Ru : Au = 1 : 5 : 15. We also
performed an erosion calculation using the SRIM
software. SRIM can calculate a sputtering yield
Ysputt for normal carbon, Ru and Au. For a given
sputtering yield Ysputt (atoms / ion) and an ion flux
Fion (ions), the erosion rate of a mirror film ΔT(cm / shot) can be written as:m
ΔT = Y sputt ⋅ Fion ⋅ρ,where m is the mirror mass (g) and ρ is themirror density (g/cm2).
The plasma debris emitted from the LPX was€studied in detail previously, with the results
indicating the debris predominantly consists offast ions. The time of flight (TOF) Xe ion signal
as detected by a Faraday-cup indicated the ion
energy is less than 6 keV, and the ion flux at the
QCM was calculated to be about 6 × 1011 /shot.
Using this result as the ion flux Fion and thecalculated sputtering yield Ysputt in the eq., we canpredict the erosion rates ΔT for the three films.
The ratios of these calculated values are C : Ru :Au = 2 : 6 : 16 , which are close to theexperimental results of 1 : 5 : 15. Compared withthe calculated erosion rate for C, the measured
value for the DLC is slightly smaller. Thisdifference may be due to the different types ofcarbon involved: high hardness DLC in theexperiment vs. normal carbon (graphite) in thecalculation.

Sn DPP X-ray sources are currently used as
extreme ultraviolet lithography (EUVL) sourcesin the industrial mass production ofsemiconductors. These sources emit X-rays at awavelength of 13.5nm, and employ grazing
incidence Ru mirrors. As shown in Fig.3, the
DLC sputtering yield by Sn ions is similar to theone by Xe ions, as calculated by the SRIM code.
Therefore, a DLC mirror may also be resistant toSn sputtering. Of course, because the Sn plasma
debris includes both “deposition“ and “sputter”
types of particles, additional debris mitigation
techniques are necessary. However, we predictthat a DLC mirror will enjoy a longer lifetime in a
Sn plasma source.

Figure 3. DLC sputtering yield by Xe and Sn ions,calculated with the SRIM code.

References[1] S.Amano et al., Appl. Opt., 52, pp.3845(2013).

Figure 2. Erosion rate of the DLC, Ru, and Au
films as measured by QCM with a debris
incidence angle of 20°.

Electronic Structure of the Fluorinated Self-Assemble
Monolayer by Photoemission and Absorption Spectroscopy
Yuichi Haruyama, Makoto Okada, and Shinji Matsui
Laboratory of Advanced Science and Technology for Industry, University of Hyogo
Abstract
The electronic structure of F-SAMs (fluorinated self-assembled monolayer) thin films withdifferent chain length was investigated by the photoelectron and absorption spectroscopy. The
photoelectron spectra in the wide region and in the C 1s core-level region were measured and thechemical compositions and components of the photoelectron spectra F-SAMs thin films withdifferent chain length were clarified. In addition, the C K-edge absorption spectra of F-SAMs
thin films were measured and the several spectral features in absorption spectra of the F-SAMs
thin films were assigned. Based on the results of the photoelectron and absorption spectroscopy
measurements of four kinds of F-SAMs with different chain length, the electronic structure of the
F-SAMs thin films is discussed.
Introduction
The study of nanoimprint lithography (NIL) [1-2] has attracted much attention for many industrial field
because it is a promising method to fabricate various nanostructures with a low cost and a high throughput. In
the process of NIL, the mold is usually coated with an antisticking layer to avoid resist adhesion. As anantisticking layer of nanoimprint mold, the fluorinated self-assemble monolayer (F-SAM) is used, forexample. The evaluation of the F-SAM with different chain length is one of the critical issues in NIL [3]. In
this study, four kinds of F-SAMs with different chain length were evaluated using the photoemission and theabsorption spectroscopy.

Figure 1. Four kinds of F-SAM thin films withdifferent chain length.
F 1s
FAS17

Intensity (arb. units)Experiments
Four kinds of F-SAMs were prepared from aprecursor [CF3(CF2)n(CH2)2Si(OCH3)3; n=0, 3, 5,
and 7] as denoted FAS-3, 9, 13, and 17,
respectively. All photoelectron and absorption
measurements were performed on a BL7B end
station at the NewSUBARU facility, University of
Hyogo. The photoelectron spectra were measured
in an analysis chamber mounted with ahemispherical electrostatic spectrometer (VSW
Ltd, CL150). The synchrotron radiation and the
Mg KD line were used as the excitation source
and were incident at 45° with respect to thesurface normal. The total energy resolutions wereabout 0.7 eV for the C 1s core-level regions. Goldfilms evaporated on copper sample holders and
F-SAMs were used for the Fermi levelmeasurements and the total energy resolution
reference. Absorption spectra were measured by
the total electron yield method. The total energy
resolution was about 0.5 eV. The photocurrents
from the sample and from a gold mesh wererecorded simultaneously. The absorption signal
was obtained from the ratio of the photocurrent
from the sample to the photocurrent from the gold
mesh.

C 1s

Si 2p
Si 2s

FAS13
FAS9
FAS3
Si
C(KLL)
1000

Results
Figure 2 shows the photoelectron spectra infour kinds of F-SAMs with different chain length.
The photoelectron spectrum of Si substrate is alsoplotted for comparison. Several peaks wereobserved at ~688, ~532, ~290, ~100eV, which

F(KLL)
O 1s

800

400
600
Binding energy (eV)200

0Figure 2. Wide scan of the photoelectron spectra of
the four kinds of F-SAMs thin films with different
chain length. The photoelectron spectra in thisfigure were normalized by the C 1s peak intensity.

were originated from the F 1s, O 1s, C 1s, and Si 2p electrons, respectively. With increasing the chain length,
the intensity of the peak at ~688eV increased while intensity of the peaks at ~532 and ~100eV decreased. On
the other hand, the intensity of the peaks at ~ 290 eV did not change with increasing the chain length. These
indicate that the intensity of the Si substrate decreased due to the increase of thickness of F-SAM withincreasing the chain length. In Figure 3, the photoelectron spectra of the C 1s core-level region in four kindsof F-SAMs with different chain length are plotted. In the photoelectron spectra of the C 1s core-level, threepeaks at ~293, ~286, and ~284.5 eV were observed in the FAS-3 although four peaks at ~293, ~291, ~286,
and ~284.5 eV were observed in the FAS-9, 13, and 17. The intensity of the peak at 291 eV increased withincreasing the chain length. On the other hand, the intensity of the peaks at ~293, ~286 eV did not changewith increasing the chain length. From the chemical compositions of four kinds of F-SAMs with different
chain length, these peaks at ~293, ~291, ~286, and ~284.5 eV were assigned to the CF3, CF2, CH, and C-C
components, respectively. Figure 4 shows the absorption spectra in four kinds of F-SAMs with different
chain length. Several peaks were observed at 285, 292, 295, 296-300eV. The intensity of the peak at 292eV
increased with increasing the chain length. On the other hand, the intensity of the peaks at 285, 295,
296-300eV did not change with increasing the chain length. The peaks at 292 eV were assigned to theV*(C-F) and V(CF2) componetns. On the other hand, these peaks at 285, 295, and 296-300 eV were assigned
to the S*(C-C) and V*(C-H), V*(C-F) and S(CF3), and V*(C-F),V(CF2, CF3), V*(C-C) components,
respectively [4]. When the incident angle of the synchrotron radiation to the sample surface was changed, noclear change of the absorption spectra was not observed in four kinds of F-SAMs with different chain length.
This indicates that each molecular with different chain length on the Si surface seems to be oriented
randomly.
C 1s

90

C K-edge

FAS-17

Intensity (arb. units)

Intensity (arb. units)

FAS17
FAS13
FAS9
FAS3

o

FAS-13
FAS-9
FAS-3

Si
295

290
285
Binding energy (eV)280

Figure 3. Photoelectron spectra of the C 1s
core-level region in four kinds of F-SAMs thinfilms with different chain length.

280

290

300
310
Photon energy (eV)320

Figure 4. C K-edge absorption spectra in fourkinds of F-SAMs with different chain length.

References[1] S. Y. Chou, P. R. Krauss, P. J. Renstrom, Appl. Phys. Letters 67, 3114-3116 (1995).
[2] K. Nakamatsu, K. Watanabe, K. Tone, H. Namatsu, and S. Matsui, J. Vac. Sci. Techmol. B 23, 507-512(2005).
[3] Y. Nakai, S. Omoto, M. Okada, K. Kanda, Y. Haruyama, and S. Matsui, J. Photopolymer Sci. and Tech.,23, 55-58 (2010).
[4] I. Ishii, R. McLaren, A. P. Hitchcock, K. D. Jordan, Y. Choi, M. B. Robin, CAN. J. Chem., 66, pp. 2104
(1988).

Orientation evaluation of 3D-photoreactive liquid
crystalline polymer structure fabricatedby thermal nanoimprinting
Makoto Okada1, Emi Nishioka2, Risa Hosoda2, Mizuho Kondo2, Yuichi Haruyama1,
Tomoyuki Sasaki3, Hiroshi Ono3, Nobuhiro Kawatsuki2 and Shinji Matsui1
1

Laboratory of Advanced Science and Technology for Industry, University of Hyogo, Japan
Department of Materials Science and Chemistry, Graduate School of Engineering, Univ. of Hyogo,3
Department of Electrical Engineering, Nagaoka University of Technology

2

Abstract
Photoreactive liquid crystalline polymer is able to be control by linearly polarized ultra violet(LPUV) irradiation and heat treatment. We found that P6CAM, which is one of the photoreactive
liquid crystalline polymers, was reoriented by thermal nanoimprinting. It is confirmed that theP6CAM molecules were reoriented parallel to the imprinted line. To examine whether the twomolecular orientation directions are induced on the P6CAM film, we carried out thermal
nanoimprinting using a mold with 3D structure pattern. As the results, the P6CAM 3D structure
has two molecular orientation directions.
mold was coated with an antisticking layer. We
used a thin polydimethylsiloxane (PDMS) layer
as the antisticking layer [5]. We carried out
thermal nanoimprinting using this mold.

Introduction.
The photo-induced orientation of polymericfilms has received much attention due to its
potential use in many kinds of optical andphotonics applications. P6CAM, which is a one ofthe photoreactive liquid crystalline polymers,
exhibits a large photoinduced molecularreorientation with a high photoreactivity toward
linearly polarized UV (LPUV) light and heat
treatment [1, 2]. We found that P6CAM wasaligned by thermal nanoimprinting[3] using line
and space (L&S) pattern mold [4]. We confirmedthat the P6CAM molecules were reoriented
parallel to the imprinted line on the imprinted
P6CAM film in the case of using a normal L&S
pattern mold. If a mold with bidirectional L&S
pattern is used for the thermal nanoimprint on the
P6CAM, two reorientation directions of themolecules according to the bidirectional moldpattern may be induced. To confirm that, wefabricated the bidirectional line pattern mold byelectron beam (EB) lithography and reactive ion
etching (RIE) and then carried out thermal
nanoimprinting using this mold on the P6CAM
film on a glass substrate, subsequently evaluatedthe molecular orientation by measuring thediffraction efficiency.

Fig. 1 Illustration of bidirectional line pattern.
The P6CAM was spin-coated on the glass
substrate. The mold and P6CAM substrate were
heated by 165 qC during thermal nanoimprinting.
The imprinting pressure and pressing time were
15 MPa and 4 min, respectively. After thermal
nanoimprinting, we observed the fabricated
P6CAM structure by POM under crossed-nicols
and atomic force microscopy (AFM), as shown in
Fig. 2. The POM image showed the patterncontrast which means the molecular orientation
related the pattern configuration. In addition, the3D structure was successfully imprinted on
P6CAM, as shown in Fig. 2(b).

Fabrication of bidirectional line pattern on
P6CAM
Figure 1 shows the illustration of bidirectionalline pattern. The linewidth was 2 Pm. The line
heights were 200 and 100 nm. The two line
patterns crossed each other at right angles. The

(a)

(b)

Fig. 2 (a) POM and (b) AFM images of fabricated
3D-P6CAM structure.

1

The measured erosion rates of the DLC, Ru andAu films at an incident debris angle of 20° areshown in Fig. 2. We see a decreased erosion ratewith increasing binding energy, and the erosion
rate ratio is DLC : Ru : Au = 1 : 5 : 15. We also
performed an erosion calculation using the SRIM
software. SRIM can calculate a sputtering yield
Ysputt for normal carbon, Ru and Au. For a given
sputtering yield Ysputt (atoms / ion) and an ion flux
Fion (ions), the erosion rate of a mirror film ΔT(cm / shot) can be written as:m
ΔT = Y sputt ⋅ Fion ⋅ρ,where m is the mirror mass (g) and ρ is themirror density (g/cm2).
The plasma debris emitted from the LPX was€studied in detail previously, with the results
indicating the debris predominantly consists offast ions. The time of flight (TOF) Xe ion signal
as detected by a Faraday-cup indicated the ion
energy is less than 6 keV, and the ion flux at the
QCM was calculated to be about 6 × 1011 /shot.
Using this result as the ion flux Fion and thecalculated sputtering yield Ysputt in the eq., we canpredict the erosion rates ΔT for the three films.
The ratios of these calculated values are C : Ru :Au = 2 : 6 : 16 , which are close to theexperimental results of 1 : 5 : 15. Compared withthe calculated erosion rate for C, the measured
value for the DLC is slightly smaller. Thisdifference may be due to the different types ofcarbon involved: high hardness DLC in theexperiment vs. normal carbon (graphite) in thecalculation.

Sn DPP X-ray sources are currently used as
extreme ultraviolet lithography (EUVL) sourcesin the industrial mass production ofsemiconductors. These sources emit X-rays at awavelength of 13.5nm, and employ grazing
incidence Ru mirrors. As shown in Fig.3, the
DLC sputtering yield by Sn ions is similar to theone by Xe ions, as calculated by the SRIM code.
Therefore, a DLC mirror may also be resistant toSn sputtering. Of course, because the Sn plasma
debris includes both “deposition“ and “sputter”
types of particles, additional debris mitigation
techniques are necessary. However, we predictthat a DLC mirror will enjoy a longer lifetime in a
Sn plasma source.

Figure 3. DLC sputtering yield by Xe and Sn ions,calculated with the SRIM code.

References[1] S.Amano et al., Appl. Opt., 52, pp.3845(2013).

Figure 2. Erosion rate of the DLC, Ru, and Au
films as measured by QCM with a debris
incidence angle of 20°.