Using of proton beam writing techniques for fabrication of micro difraction gratings
To obtain micrometric gratings with a high aspect ratio by lithographic technique, it is proposed to use a proton beam focused in a line and electromagnetic scanning in the transverse direction to irradiate the resistive material. Numerical modeling is carried out to optimize the parameters of the...
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irk-123456789-1476622019-02-16T01:23:49Z Using of proton beam writing techniques for fabrication of micro difraction gratings Ponomarev, A.G. Kolinko, S.V. Rebrov, V.A. Kolomiets, V.N. Kravchenko, S.N. Приложения и технологии To obtain micrometric gratings with a high aspect ratio by lithographic technique, it is proposed to use a proton beam focused in a line and electromagnetic scanning in the transverse direction to irradiate the resistive material. Numerical modeling is carried out to optimize the parameters of the probe forming system for this task. The calculations were confirmed during the experimental implementation of the proposed technique. A grating from the 23.4×2060 μm lines was made. Для виробництва мікродифракційних граток з великим аспектним співвідношенням методом літографії запропоновано застосувати для опромінення фоторезисту протонний пучок, сфокусований в лінію, та електромагнітне сканування в поперечному напрямку. Проведене чисельне моделювання з оптимізації параметрів ЗФС для даної задачі. Розрахунки підтверджено при експериментальній реалізації запропонованого методу, виготовлено гратку зi смугами розмірами 23,4×2060 мкм. Для получения микродифракционных решеток с высоким аспектным соотношением методом литографии предложено использовать для облучения фоторезиста протонный пучок, сфокусированный в линию, и электромагнитное сканирование в поперечном направлении. Проведено численное моделирование по оптимизации параметров ЗФС для данной задачи. Расчеты подтверждены при экспериментальной реализации предложенного метода, получена решетка из полос размерами 23,4×2060 мкм. 2018 Article Using of proton beam writing techniques for fabrication of micro difraction gratings / A.G. Ponomarev, S.V. Kolinko, V.A. Rebrov, V.N. Kolomiets, S.N. Kravchenko // Вопросы атомной науки и техники. — 2018. — № 4. — С. 285-288. — Бібліогр.: 13 назв. — англ. 1562-6016 PACS: 42.82.Cr; 85.40.Hp; 81.16.Nd http://dspace.nbuv.gov.ua/handle/123456789/147662 en Вопросы атомной науки и техники Національний науковий центр «Харківський фізико-технічний інститут» НАН України |
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Приложения и технологии Приложения и технологии |
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Приложения и технологии Приложения и технологии Ponomarev, A.G. Kolinko, S.V. Rebrov, V.A. Kolomiets, V.N. Kravchenko, S.N. Using of proton beam writing techniques for fabrication of micro difraction gratings Вопросы атомной науки и техники |
| description |
To obtain micrometric gratings with a high aspect ratio by lithographic technique, it is proposed to use a proton
beam focused in a line and electromagnetic scanning in the transverse direction to irradiate the resistive material.
Numerical modeling is carried out to optimize the parameters of the probe forming system for this task. The calculations were confirmed during the experimental implementation of the proposed technique. A grating from the
23.4×2060 μm lines was made. |
| format |
Article |
| author |
Ponomarev, A.G. Kolinko, S.V. Rebrov, V.A. Kolomiets, V.N. Kravchenko, S.N. |
| author_facet |
Ponomarev, A.G. Kolinko, S.V. Rebrov, V.A. Kolomiets, V.N. Kravchenko, S.N. |
| author_sort |
Ponomarev, A.G. |
| title |
Using of proton beam writing techniques for fabrication of micro difraction gratings |
| title_short |
Using of proton beam writing techniques for fabrication of micro difraction gratings |
| title_full |
Using of proton beam writing techniques for fabrication of micro difraction gratings |
| title_fullStr |
Using of proton beam writing techniques for fabrication of micro difraction gratings |
| title_full_unstemmed |
Using of proton beam writing techniques for fabrication of micro difraction gratings |
| title_sort |
using of proton beam writing techniques for fabrication of micro difraction gratings |
| publisher |
Національний науковий центр «Харківський фізико-технічний інститут» НАН України |
| publishDate |
2018 |
| topic_facet |
Приложения и технологии |
| url |
http://dspace.nbuv.gov.ua/handle/123456789/147662 |
| citation_txt |
Using of proton beam writing techniques for fabrication of micro difraction gratings / A.G. Ponomarev, S.V. Kolinko, V.A. Rebrov, V.N. Kolomiets, S.N. Kravchenko // Вопросы атомной науки и техники. — 2018. — № 4. — С. 285-288. — Бібліогр.: 13 назв. — англ. |
| series |
Вопросы атомной науки и техники |
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AT ponomarevag usingofprotonbeamwritingtechniquesforfabricationofmicrodifractiongratings AT kolinkosv usingofprotonbeamwritingtechniquesforfabricationofmicrodifractiongratings AT rebrovva usingofprotonbeamwritingtechniquesforfabricationofmicrodifractiongratings AT kolomietsvn usingofprotonbeamwritingtechniquesforfabricationofmicrodifractiongratings AT kravchenkosn usingofprotonbeamwritingtechniquesforfabricationofmicrodifractiongratings |
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2025-07-11T02:35:51Z |
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2025-07-11T02:35:51Z |
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1837316297196568576 |
| fulltext |
ISSN 1562-6016. ВАНТ. 2018. №4(116) 285
USING OF PROTON BEAM WRITING TECHNIQUES
FOR FABRICATION OF MICRO DIFRACTION GRATINGS
A.G. Ponomarev, S.V. Kolinko, V.A. Rebrov, V.N. Kolomiets, S.N. Kravchenko
Institute of Applied Physics, National Academy of Sciences of Ukraine, Sumy, Ukraine
E-mail: ponom56@gmail.com
To obtain micrometric gratings with a high aspect ratio by lithographic technique, it is proposed to use a proton
beam focused in a line and electromagnetic scanning in the transverse direction to irradiate the resistive material.
Numerical modeling is carried out to optimize the parameters of the probe forming system for this task. The calcula-
tions were confirmed during the experimental implementation of the proposed technique. A grating from the
23.4×2060 μm lines was made.
PACS: 42.82.Cr; 85.40.Hp; 81.16.Nd
INTRODUCTION
Micro diffraction gratings are used to obtain a phase
contrast image using interference from incoherent radia-
tion from a conventional X-ray tube [1 - 3]. Another
trend of micro gratings application is generators using
diffraction radiation from moving electrons. Such gen-
erators are promising in the submillimeter wavelength
range. One of the most complex parts of a submillimeter
diffraction radiation generator is a reflective diffraction
grating [4]. The grating period for submillimeter wave-
length diapason should be <100 μm and, as the wave-
length decreases, the grating period should also de-
crease. An important requirement in both cases is the
three-dimensional nature of grating with a high aspect
ratio, and when the ratio of the planar dimensions of the
lamellas and their height should be in a certain propor-
tion. At present, there are several methods for obtaining
micro diffraction gratings using X-ray photolithographic
methods that require precise photomasks. In this paper
an alternative method of irradiating a resistive layer
using a focused beam of protons of Megaelectronvolt
energies is used. This method of exposure is straight-
forward and does not require photomasks. The process
of focusing a proton beam accelerated by means of an
electrostatic accelerator to energy of several Megaelec-
tronvolt is carried out with precision magnetic quadru-
pole lenses (MQL). With the electromagnetic deflection
system, the beam is scanned over the surface of a ho-
mogeneous layer of resistive material in accordance
with a given digital pattern [4 - 6]. This lithographic
process is called Proton Beam Writing (PBW).
In most works on the application of PBW, the beam
is focused into a spot with similar dimensions along
transverse coordinates. This is due to the complexity of
the pattern form. In the case where the pattern consists
of parallel lines, it is most optimal to obtain a focused
beam in the form of a thin elongated line. In this case,
one spot size has micrometric dimensions, and the other
is measured in millimeters. This makes it possible to
significantly accelerate the irradiation of the resistive
material to produce micrometric gratings, which later
on, when the electroplating process is developed, is
formed into diffraction gratings. In the present work,
numerical simulation of beam focusing to a line with
given dimensions and maximum current density in the
irradiated region is considered. The experimental part
shows the beam focusing procedure, the determination
of real micrometric dimensions, and the result of pro-
ducing of a micro diffraction grating pattern.
1. SIMULATION OF PROTON BEAM
FOCUSING
Quadrupole optics is used to focus the charged parti-
cle beam into the line, which is related to the physical
principles of the quadrupole lens, which has a focusing
effect in one transverse direction to the beam and defo-
cuses the beam in the other transverse direction. How-
ever, it is not effective to use one quadrupole lens in the
process of beam formation into a line. This is due to the
fact that it is possible to obtain a specific beam size in
the micrometric direction by appropriately selecting the
collimator size in this direction at a known quadrupole
lens demagnification factor. You can also obtain a dif-
ferent size by choosing the size of the collimator that
will increase in the target plane. From these considera-
tions we can conclude that in this case we will have a
low current density in the region of irradiation of the
resistive material, which is due to the inability to control
the focusing process in the millimeter range. Therefore,
in a focusing system there must be at least two quadru-
pole lenses, with two free excitation parameters of each
lens. Usually, the focusing system is calculated from the
condition of stigmatic focusing of the beam. In this
case, it is necessary to select the power of the lenses in
such a way that the required beam size on the target is
provided in the micrometric direction, in accordance
with the stigmatization of the focusing system in this
direction. And in the millimeter direction, the lens pow-
er is selected to provide the desired beam size with the
maximum resulting beam current density.
To simulate this focusing process a probe-forming
system of a nuclear scanning microprobe of the Analyti-
cal Accelerator Complex of the Institute of Applied
Physics of the NAS of Ukraine [7] was chosen. Only
one doublet of MQL of the final focusing was used,
which is located near the target camera. The geometric
parameters of the focusing system: The length of the
system (from the object collimator to the target)
l = 3553 mm; working distance (from the output of the
effective field of the last lens to the target) g = 236 mm;
effective field lengths MQL L1= 50.67 mm, L2 =
71.41 mm; the distance between the boundaries of the
effective field of the lens is a1 = 39.4 mm. The ion-
optical characteristics of the focusing system: demagni-
fication factors Dx×Dy = (-22.3)×(-5.7); chromatic aber-
rations Cpx = 76 , Cpy=82 μm/mrad%; spherical aberra-
tions <x/x'3> = -17 μm/mrad3, <x/x'y'2> =
-11 μm/mrad3, <y/y'3> = -7 μm/mrad3, <y/x'2y'> =
ISSN 1562-6016. ВАНТ. 2018. №4(116) 286
44 μm/mrad3. During the formation of a 1 MeV proton
beam, the measured beam brightness distribution in the
plane of the object collimator [8] was used on the target,
which is the Gaussian distribution in the form
b(x,x′,y,y′)=b0bx(x,x′)by(y,y′), (1)
2 2
2 2 2
1exp 2
2(1 )
b k
kτ τ
′ ′τ ττ τ τ
′ ′τ ττ τ = − − + σ σ− σ σ
τ=(x,y);
b0=7 pA/μm2 mrad2;
σx=621 μm, σx′=0,088 mrad, kx=-0.41;
σy=667 μm, σy′=0,098 mrad, ky=-0.89.
The dimensions of the collimators were chosen from
the condition for obtaining a focused beam with dimen-
sions of 25×2000 μm. Taking into account the ion-
optical characteristics, the sizes of the object collimator
were chosen equal to 2rx = 550 μm. In the y direction,
the object collimator was completely opened 2yr =
4000 μm. The dimensions of the angular collimator in
the x direction were chosen to exclude the influence of
chromatic and spherical aberrations 2Rx = 720 μm. In
the y direction, the angular collimator was completely
opened 2Ry = 4000 μm. The process of focusing the
beam with a nonuniform distribution in the phase space
in the form (1) with allowance for its clipping by object
and angular collimators with rectangular windows was
performed using the procedure described in detail in
[9, 10]. Under the condition of stigmatic focusing, the
beam dimensions on the target at the half-height of the
current density distribution were dxFWHM × dy25% =
25×280 μm. To obtain the required dimensions, it was
necessary to change the lenses excitation to preserve the
x dimension and to reach the needed y dimension.
a
b
Fig. 1. The contours of the dependence of the beam size
change on the target on the currents in the MQL coils:
a) in the x direction at the half-height of the current
density distribution; b) in the y direction at the 25%
of the distribution maximum
In Fig. 1 shows the contours of the dependence of
the beam dimensions when the supply currents of the
exciting coils of the lenses change. In Fig. 1,b, the con-
tours of the beam size change at the half-height of the
current density distribution in the x direction dxFWHM
shown in Fig. 1,a are superimposed with the size change
contours in the direction at 25% of the maximum of this
distribution. From Fig. 1,b there are two solutions for
powering the lenses that provide focusing to a spot with
dimensions dxFWHM × dy25% = 25×2000 μm. A variant
with smaller values of the lens current was chosen for
the experiment.
2. EXPERIMENTAL PROCEDURE
The calculated values of the MQL excitation cur-
rents, which ensure the beam focusing in a line with the
specified dimensions, were determined on the basis of
the experimental dependence of the magnetic induction
on the poles of the lenses on the currents in the coils
given in [11]. Due to the hysteresis it was necessary to
carry out additional focusing on the visual image of the
beam on the quartz screen to minimize the beam size in
the x direction. In the y direction the size was deter-
mined from the visual image.
The width of the line is dxFWHM of the focused beam
was determined as a result of a standard procedure for
scanning a vertically located 75 µm diameter copper
wire and detecting the yield of secondary electron emis-
sion (SEE) during the interaction of protons with a wire.
Since the direction of the wire does not coincide with
the beam line, in order to reduce the error of determin-
ing the beam dimensions, the vertical slits of the object
and angular collimators were reduced to 200 µm. As a
result, the shape of the focused beam was about the
square. In Fig. 2,a shows a secondary electrons wire
image in a scan 500×500 μm.
a
b
Fig. 2. The secondary electrons image of a copper wire
(a) and the distribution profile of the current density (b)
ISSN 1562-6016. ВАНТ. 2018. №4(116) 287
The processing of the raster consisted of the selec-
tion of a series of linear profiles of the yield of second-
ary electrons when the beam moved horizontally. The
rectangular profile selection area is shown in Fig. 2,a.
The method for determining the beam dimensions at a
half-height of the current density distribution is given in
[12] on the basis of an analysis of the rise front of the
yield of secondary electrons. This allows us to deter-
mine the distribution profile of the current density of the
focused beam, and hence the fool width at the maximum
height of the distribution in the cross section. The pro-
cessing of a sample of the SEE output profiles from 20
series (see the region shown in Fig. 2,a) is performed. In
Fig. 2,b shows one of the profiles of the SEE output and
an adjustable curve that allows determining the line
width dxFWHM. As a result of processing a series of out-
put profiles of the SEE, the size of the focused beam in
the line dxFWHM = 22 ± 5 μm was obtained. The meas-
urement error is about 20% and is caused by instability
in time of the beam current from the electrostatic accel-
erator. The measured beam current was ≈ 8 nA. Thus,
the rate of exposure dose was ≈180 nC/mm2⋅s. Based on
the data given in [13], the required dose for the selected
PMMA resist in the production of three-dimensional
structures should be> 90 nC/mm2 for a proton beam of
MeV energies. Silicon substrates with a layer of PMMA
of thickness ≈5 μm were chosen as the samples. The
process of exposure of the resistive surface of the sam-
ple to obtain a periodic structure was carried out by the
focused beam in a line for 1 s.
a
b
Fig. 3. The secondary electrons image of the irradiated
and developed region of the resistive layer on a silicon
substrate for different magnitudes of the scanning
electron microscope magnification
In Fig. 3 shows the images of the developed samples
obtained with the help of a scanning electron micro-
scope. It can be seen from these figures that the experi-
mental result agrees satisfactorily with the results of
numerical simulation from the sizes of the focused lines,
which amounted to ≈23.4×2060 μm. However, it should
be noted that there are fillets at the ends of the lines,
which is due to the absence of a limitation of the beam
brightness distribution in the y direction.
CONCLUSIONS
To focus the proton beam of Megaelectronvolt ener-
gies in a line with given dimensions an approach is pro-
posed that allows to calculate the optimum sizes of col-
limators and excitation currents of MQL. The input pa-
rameters are the beam brightness distribution in the
phase space in the object collimator plane and the ion-
optical characteristics of the probe-forming system. The
results of the numerical simulation are confirmed exper-
imentally. The width of the line-focused beam dxFWHM =
22±5 µm is determined by the method of transverse
scanning of a 75 µm wire and mathematical processing
of the SEE output profiles. After the exposure of silicon
substrates with a layer of resistive PMMA material ap-
plied and the development, the lines sizes were
≈23.4×2060 μm2 as measured using a scanning electron
microscope.
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Article received 01.06.2018
ПРИМЕНЕНИЕ ПРОТОННО-ЛУЧЕВОЙ ЛИТОГРАФИИ ДЛЯ ФАБРИКАЦИИ
МИКРОДИФРАКЦИОННЫХ РЕШЕТОК
А.Г. Пономарев, С.В. Колинько, В.А. Ребров, В.Н. Коломиец, С.Н. Кравченко
Для получения микродифракционных решеток с высоким аспектным соотношением методом литогра-
фии предложено использовать для облучения фоторезиста протонный пучок, сфокусированный в линию, и
электромагнитное сканирование в поперечном направлении. Проведено численное моделирование по опти-
мизации параметров ЗФС для данной задачи. Расчеты подтверждены при экспериментальной реализации
предложенного метода, получена решетка из полос размерами 23,4×2060 мкм.
ВИКОРИСТАННЯ ПРОТОННО-ПРОМЕНЕВОЇ ЛІТОГРАФІЇ ДЛЯ ФАБРИКАЦІЇ
МІКРОДИФРАКЦІЙНИХ ГРАТОК
О.Г. Пономарьов, С.В. Колінько, В.А. Ребров, В.М. Коломієць, С.М. Кравченко
Для виробництва мікродифракційних граток з великим аспектним співвідношенням методом літографії
запропоновано застосувати для опромінення фоторезисту протонний пучок, сфокусований в лінію, та елект-
ромагнітне сканування в поперечному напрямку. Проведене чисельне моделювання з оптимізації параметрів
ЗФС для даної задачі. Розрахунки підтверджено при експериментальній реалізації запропонованого методу,
виготовлено гратку зi смугами розмірами 23,4×2060 мкм.
INTRODUCTION
1. SIMULATION OF PROTON BEAM FOCUSING
2. EXPERIMENTAL PROCEDURE
CONCLUSIONS
references
применение ПРОТОННО-ЛУЧЕВОЙ ЛИТОГРАФИИ для ФАБРИКАЦИи
МИКРОДИФРАКЦИОННЫХ РЕШЕТОК
використання ПРОТОНнО-ПРОМЕНЕВОЇ ЛІТОГРАФІЇ для ФАБРИКАЦІї
МІКРОДИФРАКЦІЙНИХ ГРАТОК
|