{"created":"2023-06-20T13:21:08.857255+00:00","id":1255,"links":{},"metadata":{"_buckets":{"deposit":"41e2c824-f74d-498c-ad54-f3aa02af2f90"},"_deposit":{"created_by":1,"id":"1255","owners":[1],"pid":{"revision_id":0,"type":"depid","value":"1255"},"status":"published"},"_oai":{"id":"oai:ir.soken.ac.jp:00001255","sets":["2:431:24"]},"author_link":["0","0","0"],"item_1_creator_2":{"attribute_name":"著者名","attribute_type":"creator","attribute_value_mlt":[{"creatorNames":[{"creatorName":"田中, 桃子"}],"nameIdentifiers":[{}]}]},"item_1_creator_3":{"attribute_name":"フリガナ","attribute_type":"creator","attribute_value_mlt":[{"creatorNames":[{"creatorName":"タナカ, モモコ"}],"nameIdentifiers":[{}]}]},"item_1_date_granted_11":{"attribute_name":"学位授与年月日","attribute_value_mlt":[{"subitem_dategranted":"2008-03-19"}]},"item_1_degree_grantor_5":{"attribute_name":"学位授与機関","attribute_value_mlt":[{"subitem_degreegrantor":[{"subitem_degreegrantor_name":"総合研究大学院大学"}]}]},"item_1_degree_name_6":{"attribute_name":"学位名","attribute_value_mlt":[{"subitem_degreename":"博士（工学）"}]},"item_1_description_12":{"attribute_name":"要旨","attribute_value_mlt":[{"subitem_description":"Owing to the recent progress in laser technology, highly intense extreme ultraviolet
(EUV) sources based on laser-produced plasma have been receiving strong interest for
various applications, such as the processing technique of next generation semiconductor
based on EUV lithography, and spatially and temporally highly resolved imaging of
living cells.. Due to the variation of the applications, improvement of EUV sources to
suit each use has been intensively studied. Among these laser plasma EUV sources, an
x-ray laser is a characteristic source with short pulse duration of several pico-seconds,
narrow spectral width of less than 10-4for Δλ/λ, and possibility of high coherence. The
high spatial coherence is especially an important factor because the x-ray beam can be
focused to a spot diameter of the wavelength order if the focusing system has sufficient
precision. With pulse duration of several pico-seconds, the small focal-size realizes the
imaging of high-speed phenomenon in the micro domain. Furthermore, x-ray lasers are
expected as a source of interference measurements for evaluating EUV optical system
and surface accuracy of optics in the field of EUV lithography. For the present
measurement, synchrotron radiation is used by inserting a monochromator and pinholes
in the undulator line. This can also be done in a laboratory scale by using an x-ray laser
as EUV source. .
At the Advanced Photon Research Center, the x-ray lasers generated with
transient gain collisional excitation (TCE) method have been studied and have achieved
the saturation amplification of a nickel-like silver x-ray laser at the wavelength of 13.9
nm. The TCE scheme have several advantages, such as short pulse duration less than
ten pico-seconds, and a high gain generation with low excitation energy of several tens
of Joules. In particular, EUV with the wavelength of around 13 nm is useful for
lithography, imaging, and interference measurement because the multilayer mirror with
high reflectance is commercially prepared. However, the beam divergence of the x-ray
laser generated with TCE method is as large as 10 mrad and spatial coherence is not
sufficient. In this study, the beam divergence and spatial coherence of the TCE x-ray
laser was improved and applied to measurement of time resolved emission
spectroscopy.
As an application of the x-ray laser, the scintillation properties of a zinc oxide ,
(ZnO) single crystal are evaluated for EUV using a 13.9 nm x-ray laser. For
next-generation lithography applications, various efforts have been made not only for
demonstration of efficient EUV sources, but also for the development of functional
optical components in the EUV region. In particular, the development of efficient and
fast imaging scintillator devices with sufiicient size is a key element for lithographic
applications. in these aspects, hydrothermal method grown ZnO is a prominent
candidate. Currently, its growth characteristics have been greatly improved in the aspect
of crystalline quality and size of up to 3-inch-diameter. ZnO has been intensively
studied for the past ten years as a light-emitting diode material and as nano-structured
material to improve the optical properties including response time. The advantage of
bulk ZnO is the availability of large sized homogeneous crystal with a reasonable
fabrication cost. For the evaluation of hydrothermal method grown ZnO, a nickel-like
silver x-ray laser operating at 13.9 nm is the ideal light source; having large pulse
energy up to about micro-joules level and a sufiiciently short pulse duration down to
several picoseconds.
The improvement of the nickel-like silver x-ray laser at the wavelength of 13.9
nm is described in chapter 2. To decrease the beam divergence of the x-ray laser, we
have used the double target configuration. On this technique, a part of the x-ray laser
generated in the first medium is used as the seed x-ray laser, and it is injected into the
successive second medium, which is used as an amplifier with calm density gradient.
The gain medium plasmas are generated with a chirped pulse amplification Nd:glass
laser system with two beam lines. Each beam consisted of two pulses; a pre-pulse with a
pulse duration of 300 ps and a picosecond heating pulse with a temporal delay of 600 ps
from the pm-pulse. The pulse duration of the heating pulse for the first target is 4 ps
with the quasi-travelling wave arrangement and that for the second target is 12 ps
without the travelling wave. The total pumping energy is set to be 14 J for the first
target and 11 J for the second target The energy ratio of the pre-pulse and the heating
pulse is 1:8. The laser pulses are focused with a line shape of 6.5 mm × 20μm on flat.
silver targets with an irradiance of the heating pulse of ～1015W/cm2. The distance
between the two targets is 20 cm. The far field patterns of the x-ray laser are measured
for several seed timing by changing the optical delay of the pumping laser of the first
target. At the timing of -15 ps, only the seed x-ray laser from the first target is observed.
The beam divergence of the seed x-ray laser is approximately 6 mrad in full width at
half maximum (FWHM). The total energy of the seed x-ray laser is 270 nJ. For the
seed timing of 0 ps and +15 ps, the intense beams amplified in the second medium was
observed. When the timing is adjusted to be 0 ps, an intense x-ray laser beam with little
divergence of 0.5 mrad in direction parallel to the target surface is observed outside the
shadow of the second plasma. The beam is spread in the direction perpendicular for 2.5
mrad. This means that the seed x-ray is amplified in the high gain region, where the
refraction is dominant Delaying the pumping time of the seed x-ray from the timing of
0 ps, the spreading x-ray laser becomes weaker, and an intense and narrow spot appears
inside the shadow of the plasma At the timing of -15 ps, only the narrow spot is
observed, which can be fit well with a Gaussian profile. The beam divergence is
obtained to be a much-reduced value of 0.20 mrad (FWHM) for the directions
perpendicular and parallel to the target surface The diffraction limited beam divergence
for a coherent Gaussian beam with a source size of 50 μm is analytically calculated to
be 0.11 mrad. The observed divergence is only 1.8 items greater than this value. This
implies that the obtained x-ray beam is quite close to the diffraction-limited condition.
The gain coefficient of the amplifier plasma at the timing of +15ps is estimated to be
7.9 cm-1 with exponential fitting to the data. This value is smaller than the gain
coefficient of the single target, which is observed to be 35 cm-1 in a previous study. This
small gain coefficient and small beam divergence suggest that the gain region of this
highly directed beam is located in a low density area, where the influence of refraction
is negligible.
In order to characterize the spatial coherence of the x-ray laser beam, we carried
out a Young's double slit experiment. A pair of slits with width Of 16μm-and separation
of 150-350 μm is placed 2.3 m away from the second target where the beam diameter is
460 μm. Even the 350 μm separated double slit, the interference pattern with high
contrast was observed for both parallel and perpendicular direction Assuming the
Gaussian shell model for the x-ray laser source, the spatial coherence length can be
determined by the visibility of the fringe patterns. For both the parallel and
perpendicular direction, the spatial coherent length is estimated to be about 600μm,
which is longer than the beam diameter at the position of the double slit. It means that
this narrow beam is spatially fully coherent
The evaluation of the scintillation properties of ZnO single crystal for EUV
lithography is described in chapter 3. The x-ray laser operated at 13.9 nm was employed
as the excitation source. The lasing scheme is the 4p4d transition of the nickel-like
silver ion pumped with TCE method. The typical energy of the x-ray laser
emission was 0.5 μJ and the duration was 7 ps. This value is sufficiently short for this
experiment The single( crystal ZnO sample is grown by hydrothermal ｍethod combined
with a platinum inner container. High-purity and transparent ZnO single crystal with a
large size of 50×50×15mm3 was sliced with a (0001) surface orientation. The x-ray
laser was focused on the sample using a molybdenum/silicon multilayer spherical
mirror suitable for 13.9 nm. In spite of the huge photon energy compared with the
bandgap, no visible co1or center was observed after about 50 shots irradiation. To
eliminate continuous emission from the plasma., a 0.2 μm-thick zirconium foil was
placed before the EUV mirror. The fluorescence spectrum and the fluorescence lifetime
of the ZnO sample were measured using the 25 cm-focal-length spectrograph coupled
with a streak camera with the temporal resolution of 100 ps in the fastest scanning range.
The trigger pulse of the streak camera was provided by a pulse generator, which also
served as the master clock of the x-ray laser. For comparison, the scintillation properties
were also evaluated using the 351 nm third harmonics from the 10S3 nm chirped
pumping source for the x-ray laser. The ZnO was excited at energy slightly above the
bandgap. The pulse duration of the 351 nm excitation is measured to be 110ps.
One shot of x-ray laser was enough to obtain an image of the time-resolved
fluorescence spectrum. To reduce the noise level, three frames were integrated to obtain
a clear streak image. The time profile at the peak of the spectrum can be expressed by a
double exponential decay with time constants of 1 ns and 3 ns. The two decay constants
have been measured in several works for UV excited ZnO single crystals. The fast
decay is the lifetime of free exciton and the slower decay is assigned to be trapped
carriers. The corresponding fluorescence spectrum and the time profile of UV excitation
is also measured. In both the excitation conditions, a prominent fluorescence peak of the
ZnO exciton transition was observed at around 380 nm. This wavelength is still
convenient for high resolution imaging devices, since even BK7 glass is transparent at
this wavelength. Moreover, the two decay lifetimes observed in both cases were almost
similar regardless of the huge difference in the excitation photon energy. The
fluorescence lifetime is sufficiently short for the characterization of the laser plasma
EUV source with nanoseconds duration for lithographic applications. Furthermore, a
large-sized and homogeneous material is potentially attractive for EUV imaging
applications including lithography.
","subitem_description_type":"Other"}]},"item_1_description_7":{"attribute_name":"学位記番号","attribute_value_mlt":[{"subitem_description":"総研大甲第1181号","subitem_description_type":"Other"}]},"item_1_select_14":{"attribute_name":"所蔵","attribute_value_mlt":[{"subitem_select_item":"有"}]},"item_1_select_8":{"attribute_name":"研究科","attribute_value_mlt":[{"subitem_select_item":"先導科学研究科"}]},"item_1_select_9":{"attribute_name":"専攻","attribute_value_mlt":[{"subitem_select_item":"22 光科学専攻"}]},"item_1_text_10":{"attribute_name":"学位授与年度","attribute_value_mlt":[{"subitem_text_value":"2007"}]},"item_creator":{"attribute_name":"著者","attribute_type":"creator","attribute_value_mlt":[{"creatorNames":[{"creatorName":"TANAKA, Momoko","creatorNameLang":"en"}],"nameIdentifiers":[{}]}]},"item_files":{"attribute_name":"ファイル情報","attribute_type":"file","attribute_value_mlt":[{"accessrole":"open_date","date":[{"dateType":"Available","dateValue":"2016-02-17"}],"displaytype":"simple","filename":"甲1181_要旨.pdf","filesize":[{"value":"445.2 kB"}],"format":"application/pdf","licensetype":"license_11","mimetype":"application/pdf","url":{"label":"要旨・審査要旨","url":"https://ir.soken.ac.jp/record/1255/files/甲1181_要旨.pdf"},"version_id":"378102be-62c5-4ea0-9eef-06279fc3215e"}]},"item_language":{"attribute_name":"言語","attribute_value_mlt":[{"subitem_language":"jpn"}]},"item_resource_type":{"attribute_name":"資源タイプ","attribute_value_mlt":[{"resourcetype":"thesis","resourceuri":"http://purl.org/coar/resource_type/c_46ec"}]},"item_title":"Ｘ線レーザーを用いた固体の時間分解分光の研究","item_titles":{"attribute_name":"タイトル","attribute_value_mlt":[{"subitem_title":"Ｘ線レーザーを用いた固体の時間分解分光の研究"},{"subitem_title":"Time-resolved spectroscopy of solid-state materials using an x-ray laser","subitem_title_language":"en"}]},"item_type_id":"1","owner":"1","path":["24"],"pubdate":{"attribute_name":"公開日","attribute_value":"2010-02-22"},"publish_date":"2010-02-22","publish_status":"0","recid":"1255","relation_version_is_last":true,"title":["Ｘ線レーザーを用いた固体の時間分解分光の研究"],"weko_creator_id":"1","weko_shared_id":-1},"updated":"2023-06-20T16:06:42.407953+00:00"}