bluuebunny/crossref_metadata_2025 huggingface dataset:
Preparation and Characterization of V2O3 Powder and Film
Authors: Piao Jinshun , Takahashi Seiji , Kohiki Shigemi
Published: October 2002

V2O3 powder and film were prepared by the reduction of sol–gel-synthesized V2O5.
The V2O3 single phase was synthesized by reduction above 500°C for 2 h in
hydrogen atmosphere. X-ray diffraction measurements revealed that the films
were distorted by the substrate and that the antiferromagnetic insulator-metal
(AFI-M) transition observed in resistivity temperature curves of the films was
broader than those of powders. It was concluded that the broader transition was
caused by film strain.
Deposition of Heteroepitaxial In2O3 Thin Films by Molecular Beam Epitaxy
Authors: Taga Naoaki , Maekawa Mikako , Shigesato Yuzo , Yasui Itaru , Kamei Masayuki , Haynes T. E.
Published: October 2002

Highly oriented thin film In2O3 was heteroepitaxially grown on an optically polished (001)
plane of single crystalline yttria stabilized zirconia (YSZ) substrate using molecular beam
epitaxy (MBE). The full-width at half maximum (FWHM) of the X-ray rocking curve was
0.08° for 200-nm-thick In2O3 layers indicating excellent uniformity of the crystallographic
orientation compared with the heteroepitaxially-grown In2O3 deposited by a conventional
method such as electron-beam (e-beam) evaporation. The minimum yield (χmin
) of the MBE
grown In2O3 film obtained from Rutherford backscattering (RBS) spectra was also extremely
small with a value of 3.1% implying high crystallinity with very low lattice defect density.
Theoretical Study of the Exchange Interaction and the Exchange Force between Fe Films: Feasibility of Exchange Force Microscopy
Authors: Kohji Nakamura Kohji Nakamura , Tamio Oguchi Tamio Oguchi , Hideo Hasegawa Hideo Hasegawa , Kazuhisa Sueoka Kazuhisa Sueoka , Kazunobu Hayakawa Kazunobu Hayakawa , Koichi Mukasa Koichi Mukasa
Published: October 2002

A theoretical study of the exchange interaction and the exchange force between two magnetic Fe(001) films based on a first-principles calculation is reported. Our calculations are carried out by varying the separation between the surface of two films from 1.4 to 5.0 Å. In these separations, we observed strong distance dependences of the exchange interaction and the exchange force. The variation in the exchange interaction and the exchange force relative to the atomic site on the surface are significant. Based on these results, the feasibility of exchange force microscopy (EFM) which probes the exchange force between the tip and the sample is discussed.
Development of a Compact Atomic Beam Flux Monitor Based on Surface Ionization
Authors: Tamura Koji , Ohba Hironori , Okazaki Tetsuji , Adachi Hajime , Shibata Takemasa
Published: October 2002

We have developed a compact atomic beam flux monitor by means of
surface ionization. The properties were studied by measuring various rare-earth elements (Ce, Nd, Sm, Dy, Yb). The proportional region between the
beam flux and the surface ionization ion current was observed for every
element, which indicates that with this monitor, the atomic beam flux can be
determined from the observed ion current. For Nd, Sm, Dy, and Yb, the ion
current was proportional to the atomic beam flux up to 100–200 Å/s. On the
other hand, the ion current for Ce saturated around the beam flux of 30 Å/s.
This can be explained by the fact that since the vapor pressure of Ce atoms
is low they do not desorp fast enough from the filament, and the filament is
covered with Ce atoms. The coverage of the filament limits the measurable
range of the monitor.
Multiple Light Scattering Model Applied to Reflective Display Materials
Authors: Barchini R. , Hart J. G. Gordon II
Published: October 2002

An estimate for the minimum film thickness required to give the scattering state
of a reflective display material, such as a polymer dispersed liquid crystal (PDLC) or
polymer stabilized cholesteric texture (PSCT), a desired diffuse luminous reflectance is
presented. It is concluded that single scattering models are not suited for this task. To
account for the multiple scattering of light, a previously developed model based on Mie
scattering and two-flux radiative transfer theory is implemented. This simple model
relates the size, composition, and the volume fraction of the scattering entities to the
diffuse reflectance of the material. It is shown that the diffuse reflectance predictions
from this model are in good agreement with measurements from other turbid systems.
Using assumptions intended to produce an underestimate, it is concluded that the most
birefringent liquid crystal materials currently available would require a film thickness
between 11.5 µm and 17 µm to give an ideal black substrate a diffuse luminous
reflectance of 60%.
Process Technology for Next Generation Photomask
Authors: Sohn Jung-Min , Kim Byung-Gook , Choi Sung-Woon , Kim Jin-Min , Cha Byung-Cheol , Yoon Hee-Sun
Published: October 2002

Optical lithography will be extended to 0.13 µm device generation even though other lithography methods have
been developed and on-mask chrome structures must undergo a corresponding in size reduction. Therefore, the
current photomask manufacturing technologies should be further developed in order to meet the requirements for
rapidly shrinking devices geometries with increasing device densities. This requires the mass production of optical
proximity correction masks with quarter micron assist features and phase shift masks. Excellent linewidth control
will also be required in the core of 6 inch area. In this paper, a photomask process technology for making next
generation photomask satisfying high resolution and good CD control requirements has been described
Lithography Computer Aided Design Technology for Embedded Memory in Logic
Authors: Ohnuma Hidetoshi , Tsudaka Keisuke , Kawahira Hiroichi , Nozawa Satoru
Published: October 2002

We have developed an optical proximity effect correction (OPC) flow
for both, the repetitive memory cell patterns by a simulation-based
method and for the random logic application specific IC (ASIC) patterns
by a rule-based method.
Application results for a 0.28 µm static random access memory
(SRAM) cell and 0.25 µm ASIC devices have shown that
correction time and final data size were feasible for conventional
layout design flow and mask fabrication.
Also, our system has achieved significant improvement with respect to pattern
printing fidelity between designed and printed resist patterns.
In addition to this, an automatic alternative phase shift mask (PSM)
pattern layout tool has been developed.
Using the tool with a double exposure method,
0.16 µm gate patterns for both logic and dynamic random access
memory (DRAM) have been obtained with a positive photoresist. The developed
lithography computer aided design (CAD) technology has improved the
accuracy of pattern formation for
state of the art device fabrication.
The fabricated patterns have satisfied the required linewidth accuracy,
within ±10% of the design value, ones under the practical
exposure-focus window.
0.12 µm Optical Lithography Performances Using an Alternating Deep UV Phase Shift Mask
Authors: Trouiller Yorick , Buffet Nicolas , Mourier Thierry , Schiavone Patrick , Quere Yves
Published: October 2002

Manufacturing the next generation of devices will demand lithographic capability in the sub-0.18 µm range. The
phase shift mask (PSM) is a key emerging technology which is thought to extend 248 nm optical lithography.
Using the Levenson PSM technique allows us to improve resolution by as much as 50% at gate level. This paper
describes the lithographic performances of the Shipley UV5 photoresist on SiO
x
N
y
bottom antireflective coating
(BARC), using alternating PSM and an ASM/90 Deep UV stepper. Critical dimension (CD) measurement was
done on an OPAL 7830i metrology scanning electron microscope (SEM). Results on sub-0.18 µm design rules are
presented as follows.

–The first part concerns experimental conditions: masks, process conditions, anti-reflective substrates, etching and
metrology are discussed.

–The second part concerns lithographic performances: process linearity from 0.12 µm to 0.18 µm, 0.12 µm isolated
line process latitudes of 7% energy latitude for 0.8 µm depth of focus (DOF) have been exhibited. Finally we try to
evaluate the proximity effect and the ultimate resolution of this technology.
Charge-reducing Effect of Chemically Amplified Resist in Electron-Beam Lithography
Authors: Nakasugi Tetsuro , Magoshi Shunko , Sugihara Kazuyoshi , Saito Satoshi , Kihara Naoko
Published: October 2002

The charging effect of chemically amplified resists in electron-beam (EB) lithography is described.
The results of pattern placement error caused by the charging effect using SiO2 substrates with
various thicknesses revealed that the resist with polyhydroxystyrene (PHS) has the ability to reduce
the pattern placement error due to the charging effect as compared to the resist, SAL601. From the
measurement of the surface resistance of the resist, it was found that the surface resistance of the
resist with PHS decreases from 1017Ω to 1012Ω after UV exposure, even though no change in
surface resistance was observed for SAL601. These results imply the following: (1) the charge-reducing effect of the resist with PHS is related to EB bombardment-induced conductivity of resist
and (2) the deposited charge in the resist with PHS dissipates at a rate sufficient to avoid charging
problems as a result of a leakage current through the surface of SiO2 film or electron-beam-induced
current (EBIC). In this paper, we report the experimental results and the possible mechanism to
explain the charge-reducing effect of the resist with PHS.
Application of a New Empirical Model to the Electron Beam Lithography Process with Chemically Amplified Resists
Authors: Ham Young-Mog , Baik Ki-Ho , Lee Won-Gyu , Chung Tack Dong , Chun Kukjin
Published: October 2002

We study on the simulation models and characteristics of a highly sensitive chemically amplified resist (CAR), which is used in the fabrication of deep submicron pattern delineation. The main aim of this model is to express the positive and negative CAR by using similar principles in acid generation, reaction and diffusion, reaction mechanism, and development. Profile simulation uses the fitted parameters. Therefore, resist pattern shapes are in good agreement with the experimental ones. Simulation accuracy is 1.04% and 7.5%, for resist wall angle and critical dimension (CD) of CAR respectively. We also verify that components and properties of CAR determine the resist profile and process margin. Using this model, process feasibility of electron beam lithography is predicted, and accurate simulation is possible in the deep submicron region.
Proximity Effect Correction by Pattern Modified Stencil Mask in Large-Field Projection Electron-Beam Lithography
Authors: Kobinata Hideo , Yamashita Hiroshi , Nomura Eiichi , Nakajima Ken , Kuroki Yukinori
Published: October 2002

A new method for proximity effect correction, suitable for large-field electron-beam (EB)
projection lithography with high accelerating voltage, such as SCALPEL and PREVAIL in the
case where a stencil mask is used, is discussed. In this lithography, a large-field is exposed by
the same dose, and thus, the dose modification method, which is used in the variable-shaped
beam and the cell projection methods, cannot be used in this case. In this study, we report on
development of a new proximity effect correction method which uses a pattern modified stencil
mask suitable for high accelerating voltage and large-field EB projection lithography. In order
to obtain the mask bias value, we have investigated linewidth reduction, due to the proximity
effect, in the peripheral memory cell area, and found that it could be expressed by a simple
function and all the correction parameters were easily determined from only the mask pattern
data. The proximity effect for the peripheral array pattern could also be corrected by
considering the pattern density. Calculated linewidth deviation was 3% or less for a 0.07-µm-L/S memory cell pattern and 5% or less for a 0.14-µm-line and 0.42-µm-space peripheral array
pattern, simultaneously.
High-Speed Convolution System for Real-Time Proximity Effect Correction
Authors: Susumu Oogi Susumu Oogi , Takiji Ishimura Takiji Ishimura , Takashi Kamikubo Takashi Kamikubo , Mitsuko Shimizu Mitsuko Shimizu , Yoshiaki Hattori Yoshiaki Hattori , Tomohiro Iijima Tomohiro Iijima , Hirohito Anze Hirohito Anze , Takayuki Abe Takayuki Abe , Toru Tojo Toru Tojo , Tadahiro Takigawa Tadahiro Takigawa
Published: October 2002

In order to realize a real-time proximity effect correction system, a high-speed, highly accurate hardware system for convolution calculation has been developed. The representative figure method is used in the system. Pipeline architecture and parallel processing architecture are also used. The calculation speed of the system is 500 s for a writing region of 10 ×10 cm. The optimum correction dose has been evaluated using the output data of the convolution system. The error in the correction dose caused by our system is found to be 0.5% at most. These results suggest that a real-time proximity effect correction system can be realized, which can be used for making reticles of Gbit-class dynamic ramdom access memories (DRAMs).
Sub-10-nm Electron Beam Lithography Using a Poly(α-methylstyrene) Resist with a Molecular Weight of 650
Authors: Manako Shoko , Fujita Jun-ichi , Tanigaki Katsumi , Ochiai Yukinori , Nomura Eiichi
Published: October 2002

Only the 7 nm patterning has been achieved by using an organic
negative electron beam (EB) resist, poly(α-methylstyrene) resist with a molecular weight of 650 (αMST650). An
αMST650 resist film can be prepared by a conventional spin-coating technique and its
surface roughness is smooth, with peak-to-valley roughness of less than 1.5 nm.
Although the sensitivity of αMST650 is very low, 30 mC/cm2, high-resolution patterns
of 15 nm width and 25 nm pitch with no scum have been fabricated using a 50 kV
electron beam of about 7 nm diameter. The etching selectivity between Si and
αMST650 is about 2.3 and the etching durability of αMST650 is superior to thouse of
calixarene resist and polystyrene resist. The minimum line pattern sizes achievable with
αMST650 resist is 7 nm, although the minimum line pattern size of polystyrene with a
molecular weight of 1100 is about 12 nm. The pattern size dependence of resist resin
molecular weight exit in beyond resist molecular weight of 650.
Sub-10-nm Overlay Accuracy in Electron Beam Lithography for Nanometer-Scale Device Fabrication
Authors: Yamazaki Kenji , Fujiwara Akira , Takahashi Yasuo , Namatsu Hideo , Kurihara Kenji
Published: October 2002

A high-performance electron beam nanolithography system
with an overlay accuracy of better than 10 nm has been developed
and applied to nanodevice fabrication.
Owing to the suppression of charge-up and
precise beam position control by taking into account stage position error
as well as improvements in other factors,
we have obtained a stable beam (< 2 nm/5 min.),
the exposure position reproducibility with stage movement
(< 3 nm/500 times), and high mark-locating accuracy (3 nm).
The resulting overlay accuracy is 6–9 nm in |mean|+2σ.
Using this system,
we have made multi-island single-electron devices with fine gates
overlaid on the Si islands within a 10-nm error.
The high overlay accuracy in electron beam nanolithography will
allow the study of highly functional single-electron devices.
Sub-0.1 µm Patterning Characteristics of Inorganic Thin Films by Focused-Ion-Beam Lithography
Authors: Lee Hyun-Yong , Paek Seung-Woo , Hong-BayChung Hong-BayChung
Published: October 2002

Sub-0.1 µm patterning characteristics of low-pressure chemical-vapor-deposited Si3N4 and normally(0°) and obliquely(60° and 80°) deposited Se75Ge25 inorganic thin films have been investigated using low-energy Ga+ focused-ion-beam (FIB) lithography. These thin films act as a negative type resist for CF4-reactive-ion-etching (RIE) development. In the case of 0°-deposited Se75Ge25 and Si3N4
resists exposed by 30 keV Ga+ FIB and developed by CF4 RIE under a gas pressure of 150–200 mTorr, the image-contrasts (γ) are reasonably high, about 4.4 and 3.5, respectively. Their sensitivities (S), nevertheless, are relatively low in comparison with that of conventional polymer resist. Therefore, this problem should be solved, especially in order to employ these films as resists of ion-projection lithography. In the case of an 80°-deposited Se75Ge25 resist, columnar structures with an a
ngle of approximately 65° are formed which disappear after
annealing at the glass-transition temperature. The γ of this
resist is evaluated to be about 4.0, similar to that of
0°-deposited Se75Ge25, but the S is enhanced to
be about 7.0×1014 ions/cm2, which corresponds to below
half that of 0°-deposited Se75Ge25. With an
exposure of 30 keV FIB with a beam diameter of 0.1 µm and just
above the threshold dose, negative-type fine patterns with linewidths of about 0.06–0.09 µm are fabricated successfully.
Thermal Distortion of an X-Ray Mask for Synchrotron Radiation Lithography
Authors: Yang Jinfeng , Toyota Eijiro , Kawachi Shunichi
Published: October 2002

A thermal model is developed to calculate the temperature rise in scanning exposure
of synchrotron radiation lithography. The maximum temperature rise on a mask
membrane is 1°C in the scanning exposure under the given X-ray beam conditions. The
behavior of the thermal distortion of the mask has been described in the scanning
exposure. The thermal distortion is found to be smaller than 5.7 nm in the x-direction and
12.7 nm (from +8.2 nm to -4.5 nm) in the y-direction from the beginning to the end of the
exposure.
Characterization of Proximity Correction in 100-nm-Regime X-Ray Lithography
Authors: Moonsuk Yi Moonsuk Yi , Eunsung Seo Eunsung Seo , Yongduck Seo Yongduck Seo , Kyoungho Lee Kyoungho Lee , Ohyun Kim Ohyun Kim
Published: October 2002

The possibility and usefulness of proximity correction in
100-nm-regime
X-ray lithography was examined. Two-dimensional
array patterns of around 100 nm linewidth were
fabricated by e-beam exposure and subsequent gold electroplating.
The mask patterns consist of normal rectangular patterns and
shape-modified patterns which are
modified by a simple optical proximity correction (OPC)-like method
such as the addition of a simple serif at the end of the pattern.
Different serifs sizes and pattern shapes were considered.
The delineated images printed by normal rectangular mask pattern and
shape-modified mask patterns were
compared with a target image to be defined on the wafer, and
the faithfulness of printed images was determined by measuring
the lengths and widths at all the significant points on
two-dimensional patterns.
The OPC-like mask modification technique had positive effects in
improving the fidelity
of the printed image in the linewidth range below 150 nm,
especially in the reduction of image shortening in array patterns.
The optimum serif size depends on the pattern size, pattern density
and the process conditions, especially the gap between the mask and wafer.
In addition, two-dimensional aerial image simulations were performed
and compared with experimental results and showed the same results as
the experiments.
Experimental Observation of Short Microwave Generation via Relativistic Ionization Front Produced by CO2 Laser
Authors: Noboru Yugami Noboru Yugami , Katsura Fujita Katsura Fujita , Takeshi Higashiguchi Takeshi Higashiguchi , Yasushi Nishida Yasushi Nishida
Published: October 2002

A short microwave pulse is generated by the interaction between the relativistic ionization front produced by CO2 laser and a static, zero-frequency electric field. The zero-frequency electric field is produced by an alternately biased capacitor array. Laser light propagation between electrodes produces the ionization front propagating with the velocity equal to the laser group velocity. The maximum frequency of the generated microwave is determined to be in the range of 8.2 to 17.6 GHz by several waveguides with specific cut-off frequency and horn antenna combination.
Negative Ion Formation in SiO2 Etching Using a Pulsed Inductively Coupled Plasma
Authors: Choi Chang Ju , Kwon O Sung , Seol Yeo Song
Published: October 2002

The formation of negative ions in conjunction with their effect on SiO2 etching
characteristics has been investigated within a CF4/Ar pulsed-power inductively coupled plasma.
Electron energy distribution function in the pulsed plasma shows a narrow distribution compared
with the CW mode. The average electron energy and electron density decrease greatly with
decreasing duty ratio, which indicates that the high-energy electrons can be cooled effectively during
afterglow time. By means of threshold ionization mass spectrometry, radical densities including CF
x

(x=1 to 3) and F are measured as a function of duty ratio and also correlated with the average
energy and density of electrons. For negative ions, two major peaks, F- and CF3
-, are formed
predominantly through the electron attachment reactions during afterglow time. The possible
mechanisms for the negative ion formation are proposed in the pulsed plasma. Additionally, the SiO2
etch rate decreases nearly linearly with decreasing duty ratio and microtrenching is suppressed by the
reduction of charge accumulation on the sidewalls in the pulsed plasma.
Plasma-Wall Interactions in Dual Frequency Narrow-Gap Reactive Ion Etching System
Authors: Morishita Satoshi , Hayashi Hisataka , Tatsumi Tetsuya , Hikosaka Yukinobu , Noda Shuichi , Okigawa Mitsuru , Matsui Miyako , Inoue Masami , Sekine Makoto
Published: October 2002

The effects of plasma-wall interactions on the plasma chemistry in a dual frequency narrow-gap
reactive ion etching (RIE) system is investigated as a function of electron density, residence time, and partial
pressure of additive O2 gas. It is found that there is a critical point in the residence time, where the
dissociation dominant region and the wall-interaction dominant region are separated. The net flux of
chemically reactive species is estimated. The net flux of carbon-inclusive ions is of the order of 1016 cm-2s-1, and is larger than that of CF
x
radicals. Carbon-inclusive and silicon-inclusive ions dominate the total flux
of chemically reactive species. The deposition rate of the fluorocarbon film is strongly dependent on the
O2 partial pressure, and is controlled by the chemical etching with oxygen as well as the reduction of
fluorocarbon radical density in the gas phase. Based on the estimation of the net flux of chemically
reactive species and the effect of added oxygen, dominant chemical species that control the etching reaction
in the RIE system are discussed.
Depth Profiling of Na in SiOx Films by Combination of Chemical Etching and Secondary Ion Mass Spectrometry
Authors: Saito Reiko , Kudo Masahiro
Published: October 2002

A simple procedure to obtain accurate secondary ion mass spectrometry (SIMS) depth profiles of Na in SiO
x
films has been studied. SiO
x
on Si samples implanted with Na were etched off with HF solution and the surfaces were analyzed with SIMS after being coated with Ag. The Na intensity at the Ag/SiO
x
interface was plotted against the etched-off depth and the depth profile of Na was obtained. On comparing these results with those by Lindhard, Scharff and Schiott (LSS) simulation, it was proved that this procedure is useful for the depth profiling of Na in SiO
x
films. This technique was also applied to the analysis of Na in various types of SiO
x
films, which were fabricated with different processes and have different densities and compositions. It was found that this technique is quite effective for analyzing the Na distribution in the samples which cannot be analyzed accurately by the self-charge compensation method due to the structural properties of the films.
Study of Electron Energy Distribution Functions (EEDFs) in Three DC Low-Pressure Plasma Sources
Authors: Antonova Tatjana , Bougrov Gleb , Bougrova Antonina , Choi Won-Kook , Goncharov Leonid , Jung Hyung-Jin , Koh Seoh-Keun , Kondranin Sergey , Kralkina Elena , Sitin Evgeniy , Obukhov Vladimir
Published: October 2002

In the present paper the possibility of application of the regularization method for reliable determination of the position and form of structural features of electron energy distribution is considered. The regularization method is used in the processing of the probe characteristics, measured in gas discharge chambers of broad beam gridded Xe ion sources, with peripheral and with divergent magnetic fields, as well as in an ion accelerator with closed electron drift. Electron energy distribution functions with secondary maxima are observed in the plasma devices.
Spatial and Temporal Behavior of Radicals in Inductively Coupled Plasm for SiO2 Etching
Authors: Hayashi Shigenori , Yamanaka Michinari , Kubota Masafumi , Ogura Mototsugu
Published: October 2002

Fluorocarbon CF
x
(x=1, 2) radicals in an inductively coupled plasma (ICP) have been
measured using a spatially and temporally resolved laser-induced fluorescence (LIF)
technique. Hollow profiles in the radial and axial distributions for the radicals in C4F8 ICPs, in
contrast to uniform radial profiles near the substrate, suggest a destructive character within
the ICP bulk and a small surface loss probability on the chamber wall. Temporal change of
the CF2 radical distribution in the afterglow ICP was found to be dominated by the slow
diffusion and wall-reflection processes.
Study of Self-Limiting Etching Behavior in Wet Isotropic Etching of Silicon
Authors: Han Cheol-Hyun , Kim Eun-Sok
Published: October 2002

This paper reports a self-limiting etching behavior of an isotropic
silicon etchant (consisted of hydrofluoric, nitric and acetic acids)
during the formation of a spherical cavity in a silicon wafer. We
observe that the etch rate drops drastically when the etch-front diameter
is approximately equal to 1.8 times the etch window size plus 400 µm.
Such self-limiting behavior is due to the presence of gas bubbles
(consisted of SiF4 and NO, etch by-products) which close the etch window
and limit the mass transport of the etchant to the silicon surface.
Because of that, the spherical cavity size has been observed to depend
mostly on the size of the etch-mask opening, and to be independent of the
etching time. A variety of mask materials and etching conditions have
been investigated to obtain a large spherical cavity (2.5 mm in radius)
with good circularity and smoothness for microelectromechanical systems (MEMS) applications.
Epitaxial Growth of GaN by Helicon Wave Plasma Assisted Metal Organic Chemical Vapor Deposition Process
Authors: Kim Ki-Sung , Kim Seon-Hyo
Published: October 2002

A high density helicon wave plasma (HWP) source was used to synthesize a thin film of GaN epilayer on sapphire (0001).
The plasma source coupled with RF field was diagnosed with the aid of an electrical probe and an ion energy analyzer in order to investigate
its applicability to the epitaxial film growth process. The helicon wave excited plasma produced by Ar+N2 mixed gases was
extensively investigated to enhance activated nitrogens while simultaneously reducing their ion energy for their utilization
in the synthesis of GaN film with the help of a TMGa precursor. By controlling the mixing ratio of Ar to N2 gases,
the optimum plasma conditions suitable for growing the GaN epilayer were determined to be as follows: ratio of Ar to total
(Ar+N2) gas flow \cong0.5, RF power of 400 W and axial magnetic field of 750 G. The GaN films synthesized by
the HWP-assisted MOCVD process under optimum deposition conditions featured good crystallinity, and showed a full width
of half maximum (FWHM) of 6.5 arcmin for the GaN (002) peak rocking curve. The effects of deposition temperature,
group III/V elemental ratio and plasma conditions on the crystalline quality of the film are discussed.
Simulation of Phthalocyanine Dimer Spectra by Extended Dipole Model
Authors: Sakakibara Youichi , Saito Kazuhiro , Tani Toshiro
Published: October 2002

Optical absorption spectra of phthalocyanine (Pc) dimers are simulated for a series of assembling structures in which two Pc molecules are parallel to each other. Intermolecular interaction that induces change of spectra is calculated by extended dipole model and extended double-dipole model. The splitting feature of the dimer spectra shows several spectral patterns, depending on a structural parameter, namely, the slipping distance. Among the patterns we find spectral characteristics of major crystals such as α-form and β-form by choosing the appropriate parameter values. By using dipole lengths of realistic molecular dimension, simulated interaction energy approaches the experimental scale for a coaxial face-to-face structure.
Effects of BF2 and B Implantation-Doping on Crystalline Degradation of Pseudomorphic Metastable Ge0.06Si0.94
Authors: Im Seongil , Oh Min Suk , Joo Min Ho , Kim Hyo Bae , Kim Hyun Kyoung , Song Jong Han
Published: October 2002

Pseudomorphic metastable Ge0.06Si0.94 layers grown by molecular
beam epitaxy (MBE) on Si (100) substrates were implanted at room temperature
by 70 keV BF2 ions with two different doses of 3 ×1013 and
2.5 ×1014 cm-2, or by 16 keV B ions with a dose of 4 ×1014 cm-2.
The implanted samples were subsequently annealed
at 800 and 900°C for 30 min in a vacuum tube furnace.
Observed by 2 MeV 4He channeling spectrometry before annealing, only the
sample implanted at a dose of 2.5 ×1014 BF2 cm-2
is amorphized from surface to a depth of about 90 nm. Crystalline
degradation of post-annealed Ge0.06Si0.94 samples becomes
pronounced as the dose increases. Even though the both samples implanted
with 3 ×1013 BF2 cm-2 and 4 ×1014 B cm-2
initially show almost the same levels of radiation damage in the channeling spectra,
the sample implanted at 3 ×1013 BF2 cm-2 only conserves
the same crystalline quality as the as-grown GeSi after being annealed.
It is concluded that such a low dose of 3 ×1013 BF2 cm-2 can be doped by implantation
without causing radiation or strain-induced defects in the pseudomorphic GeSi.
Defect vs. Nanocrystal Luminescence Emitted in Si-Implanted SiO2 Layers
Authors: Jeong Jun Yong , Im Seongil , Oh Min Suk , Kim Hyo Bae , Chae Keun Hwa , Whang Chung Nam , Song Jong Han
Published: October 2002

Visible photoluminescence is observed from thin Si-implanted SiO2
films. Si ions were implanted into 300-nm-thick SiO2 films grown
on crystalline Si at energies of 30 and 55 keV, and with doses of 5×1015 and 1 ×1017 cm-2. Implanted samples were
subsequently annealed in N2 ambient at 500–1100°C. PL
spectra for the sample implanted with 1×1017 cm-2 at 55 keV show that red luminescence (750 nm) related to Si-nanocrystals
clearly increases with annealing temperature in intensity, and that a weak
orange luminescence (600 nm) is observed after annealing at low
temperatures of 500 and 800°C. The luminescence around 600 nm becomes very intense when a thin SiO2 sample is implanted at a
substrate temperature of 400°C with an energy of 30 keV and a
dose of 5×1015 cm-2. After annealing the sample in
forming gas the PL intensity remarkably decreases. It indicates that defects
are passivated by hydrogen. We conclude that this luminescence observed
around 600 nm is caused by some radiative defects formed in
Si-implanted SiO2.
Simple Subtraction Method for Determining the Mean Path Length Traveled by Photons in Turbid Media
Authors: Zhang Hedong , Miwa Mitsuharu , Urakami Tsuneyuki , Yamashita Yutaka , Tsuchiya Yutaka
Published: October 2002

The mean path length is a key parameter in the study of light propagation in turbid media such as living tissues. In this paper, we propose a simple subtraction method for determining the mean path length traveled by photons in turbid media. The method is based on the fact that the mean time delay (i.e., the center of gravity) of the measured re-emission profile is the sum of the mean time delays of the instrumental function (i.e., the impulse response of the measuring system) and the impulse response of a highly scattering medium. Using this method, the mean path length can be calculated quickly and accurately without the need for performing deconvolution. The theory, computer simulation and experimental demonstration are described.
Etch Properties of Gallium Nitride Using Chemically Assisted Ion Beam Etching (CAIBE)
Authors: Lee Weon-Jeong , Kim Hyeon-Soo , Lee Jae-Won , Kim Tae-Il , Yeom Geun-Young
Published: October 2002

Dry etching properties of GaN were investigated using chemically assisted ion beam etching (CAIBE) with
Cl2, BCl3, and HCl gases. The measured GaN etch rate with increasing tilt angle showed the maximum
at a 30° tilt angle, similar to the effect of tilt angle on sputter yield. The GaN etch rate was the highest
with Cl2 and the lowest with BCl3. In the case of GaN etching with BCl3, the GaN etch rate was even lower
than that in the case of GaN etched with Ar ion source only. The lower etch rate appears to be related to the higher binding energy of
BCl3 and high degree of condensation on the substrate maintained at 0°C. A highly anisotropic etch
profile with smooth sidewalls could be obtained with Cl2. The addition of Cl2 to BCl3 did not improve
GaN etch profile. The lowest roughness value of about 10 Å was obtained for the etching with Cl2. The GaN surface
etched by Cl2 and BCl3 showed an N-rich surface possibly due to the removal of Ga preferentially
by forming GaClx, and GaN surface etched by HCl showed near-stoichiometric surface possibly due to the removal of
Ga by forming GaClx and N by forming NHx.
In-situ Observation of Focused Ion Beam Micropatterns on Semiconductors and Insulators
Authors: Tanaka Miyoko , Furuya Kazuo , Saito Tetsuya
Published: October 2002

A focused ion beam (FIB) interface attached to a column of a 200 keV transmission
electron microscope (TEM) was used to perform in-situ micropatterning to semiconductors
and insulators. TEM specimens of GaAs, Si, α-SiO2 and 6H-SiC were micromilled in the
TEM during observation. Several figures were patterned with a 25 keV Ga+ FIB of 0.2 µm
beam diameter at room temperature. The effect of FIB irradiation on the structural changes
was observed simultaneously using a TV-rate video camera and sequentially using regular films.
FIB micropatterning caused polycrystallization, amorphization and Ga injection. The excess
Ga in the specimens of GaAs precipitated as liquid or amorphus particles of 0.2 µm in diameter
due to the selective etching of As. That in Si, SiO2 and SiC, on the other hand, precipitated
as small Ga dots of 1 to 10 nm in diameter, because of the low solubility of Ga in these materials.
Evaluation of Shot Position Error in Electron Beam Lithography Using Overlay Metrology with `One-Shot' Inspection Mark
Authors: Asano Koji , Nagata Takeo , Sato Masami , Nara Yasuo , Arimoto Hiroshi
Published: October 2002

Electron Beam (EB) lithography is the most attractive tool for
the development of the Ultra Large Scale Integrated Circuit (ULSI)
devices with the finest pattern rule. It is necessary to estimate
precisely the unsteadiness of the pattern positions in EB
lithography. We measured shot unsteadiness in EB lithography using
conventional overlay (O/L) technology with the one-shot inspection
mark. The reproducibility of mark edge detection of the same mark
pattern was found to have a standard deviation (σ) of less than
0.3 nano-meters (nm), and the steadiness of shot-positioning was
estimated to have a σ of less than 3 nm.
A Capacitive Silicon Microaccelerometer with Force-Balancing Electrodes
Authors: Ha Byeoungju , Oh Yongsoo , Song Cimoo
Published: October 2002

A surface micromachined accelerometer, which senses an inertial motion with an area variation, has been developed. The accelerometer is designed as an interdigital rib structure that has a differential capacitor arrangement. The movable electrodes are mounted on a mass of 7 µm thick polysilicon and a pair of stationary electrodes is formed under the mass with a 1.5 µm gap. Both sides of the movable electrodes are fixed on the mass, and the stationary electrode is formed on the substrate without being suspended. As a result, the mechanical stress and the electrical pulling effects can be reduced in comparison to the comb-type capacitor arrangement. In order to improve the dynamic range and the linearity, a pair of comb-shaped force-balancing electrodes is placed on both sides of the mass. The force-balancing electrodes are fabricated on the same layer as the mass and anchored on a silicon substrate. In particular, differential feedback electrodes enable linear control of mass repositioning.
Deposition and Patterning Technique for Realization of Pb(Zr0.52, Ti0.48)O3 Thick Film Micro Actuator
Authors: Maeda Ryutaro , Wang Zhanjie , Chu Jiaru , Akedo Jun , Ichiki Masaaki , Yonekubo So
Published: October 2002

The deposition technology for thin PZT (Pb(Zr0.52,Ti0.48)O3) layers has reached an advanced state in
the application area of memory fabrication. On the other hand, the application of PZT layers for
actuation of micro electromechanical system (MEMS) is not well established. A relatively thicker
film is necessary for this application. Conventional preparation techniques provide poor deposition
rates and the accumulated residual stress during deposition results in the deposited layer peeling off. Another difficulty lies in the low etching rate of the multilayered structure of SiO2/Ti/Pt/PZT.
These are the reasons why we have studied thick PZT film preparation technology and efficient
pattering processes. Thick film deposition processes include repeated multilayer coating by the sol-gel method, the excimer laser ablation deposition (ELAD), and the jet molding system (JMS).
Pattering processes include RIE, ECR and deposition methods on a non-planar surface. The electrical
properties of PZT layers were determined for microfabricated actuators.
Atom Manipulation with the Scanning Tunneling Microscope: Nanostructuring and Femtochemistry
Authors: Meyer Gerhard , Bartels Ludwig , Rieder Karl-Heinz
Published: October 2002

We briefly survey our recent studies on the “soft” lateral manipulation of atoms and small molecules with a scanning tunneling microscope (STM), whereby the tip-surface forces are mainly employed. Repulsive (pushing) as well as discontinuous (pulling) and continuous (sliding) attractive manipulation modes could be distinguished on Cu(211) for CO molecules and metal atoms, respectively. In the case of pulling of Cu atoms on Cu(111), even very fine details could be discerned, the adparticle may show various movement patterns visiting different surface sites upon the application of different tip forces. Lateral manipulation also allows modifications of the Cu(211) substrate itself in an atom-by-atom manner by releasing atoms from sixfold coordinated kink sites as well as from sevenfold coordinated regular step sites. Furthermore, investigations concerning controlled vertical manipulation with emphasis on “picking up” single CO molecules are reported. The mechanism behind vertical transfer of CO-molecules relates to ultrafast chemical processes. Vertical manipulation implies, besides extending the possibilities for the buildup of nanostructures, the important possibility of creating structurally and compositionally well defined tips, which may eventually lead to the realization of chemical sensitivity with the STM.
Fabrication of GaAs Microtips and Their Application to Spin-Polarized Scanning Tunneling Microscope
Authors: Shinohara Ryoichi , Yamaguchi Koichi , Suzuki Yoshishige , Nabhan Walid
Published: October 2002

GaAs microtips were fabricated by anisotropic wet etching and sulfur passivation. Scanning tunneling microscope (STM) observation with atomic-order spatial resolution was achieved using the GaAs microtips. Sulfur passivation was effective for the suppressing the surface states of the GaAs tip. For the magnetized Ni thin film, the difference in tunneling current between right and left circularly polarized light excitations was observed in the negative tip bias region and was found to depend on the magnetization direction. This result suggests that the polarization response signal is related to the spin structure of the magnetized Ni thin-film surface. Imaging of the polarization response signal was attempted, and the possibility of spin-polarized STM using circularly polarized-light-pumped GaAs microtips was revealed.
Fabrication of a Nanometer-Scale Si-Wire by Micromachining of a Silicon-on-Insulator Substrate
Authors: Fujii Hideo , Kanemaru Seigo , Matsukawa Takashi , Hiroshima Hiroshi , Yokoyama Hiroshi , Itoh Junji
Published: October 2002

Air-bridge-structured Si wires were fabricated by using a silicon-on-insulator (SOI) substrate and electrically characterized. The SOI substrate used had a sandwich structure of a 200-nm-thick p-type Si layer (SOI layer), a 400-nm-thick buried oxide layer (BOX layer) and a p-type Si substrate. The wires were made by conventional photolithography process followed by dry etching and thermal oxidation thinning of the SOI layer. The Si wires were isolated from the substrate by an air gap made in the BOX layer and had dimensions of typically 20 nm in width, 40 nm in height and 150 nm in length. It was found from the measurements of current-voltage characteristics that the current through the wires much increased by illumination with a He-Ne laser and reached about 20 nA at a bias of 1 V.
Fabrication of Nanometer-Order Dot Patterns by Lift-off Using a Fullerene-Incorporated Bilayer Resist System
Authors: Ishii Tetsuyoshi , Tanaka Hirotaka , Kuramochi Eiichi , Tamamura Toshiaki
Published: October 2002

We propose a new bilayer resist system consisting of a fullerene-incorporated positive-type
electron beam resist, ZEP520, top layer and a pure ZEP bottom layer. In this system, the difference
in resist sensitivity between the top and bottom layers can be readily optimized by changing the
fullerene content of the top layer so as to create an overhang resist pattern favorable for lift-off. A
bilayer system composed of 20 wt% fullerene-incorporated ZEP and pure ZEP produces suitable
overhang patterns with a sensitivity of ∼60 µC/cm2. The applicability of the system has been
verified through the successful fabrication of a highly-ordered array of self-organized ∼50-nm InGaAs/AlGaAs boxlike structures and a SiC nanoprinting mold with a 150-nm-pitch dot array.
Lateral Spread of Tungsten Ions Implanted in Silicon
Authors: Liang Jenq-Horng
Published: October 2002

Silicon wafers were irradiated at tilted geometry to measure the lateral spread of tungsten ions in silicon for implantation energies between 40 and 360 keV. The depth profiles of implanted tungsten ions were measured by means of secondary ion mass spectrometry. The measured transverse range stragglings were obtained by using Furukawa and Matsumura's formula. An analysis of the measured transverse range stragglings as compared to the values calculated from the Biersack theory and SRIM reveals that the calculated transverse range stragglings from the Biersack theory correlated closer to the measured ones.
Characterization of the Refractive Index of Strained GaInNAs Layers by Spectroscopic Ellipsometry
Authors: Kitatani Takeshi , Kondow Masahiko , Shinoda Kazunori , Yazawa Yoshiaki , Okai Makoto
Published: October 2002

We have characterized the refractive index of strained GaInNAs layers. Using spectroscopic ellipsometry (SE), the variation in optical constants of GaInNAs layers, about 6 nm thick with a nitrogen content lower than 1%, can be clearly observed. Analysis of the SE data, including the strain effect in the layer, clarified that the refractive index of GaInNAs increases in proportion to the nitrogen content. While the trend for increase in refractive index with a decrease in the bandgap energy is the same as that observed in conventional III–V alloy semiconductors, the rate of increase is found to be much larger than that in GaInAs. This result suggests a large density of states in the conduction band characteristics of this type of material system that includes nitrogen atoms.
Thermodynamic Analysis of Hydride Vapor Phase Epitaxy of GaN
Authors: Akinori Koukitu Akinori Koukitu , Shin-ichi Hama Shin-ichi Hama , Tetsuya Taki Tetsuya Taki , Hisashi Seki Hisashi Seki
Published: October 2002

A thermodynamic analysis of hydride vapor phase epitaxy (HVPE) is described for GaN. The partial pressures of gaseous species in equilibrium with GaN are calculated for temperatures, input GaCl partial pressures, input V/III ratios and mole fractions of hydrogen relative to the inert gas atoms. It is shown that the deposition of GaN is significantly influenced by the hydrogen mole fraction in the carrier gas. The growth rate is discussed in comparison with the experimental data reported in the literature. It is shown that the growth rate of GaN grown using HVPE is thermodynamically controlled.
Yb-Related Photoluminescence in CuGaS2, AgGaSe2and AgGaS2
Authors: Sho Shirakata Sho Shirakata , Shigehiro Isomura Shigehiro Isomura
Published: October 2002

Near-infrared photoluminescence (PL) has been studied in CuGaS2, AgGaSe2and AgGaS2crystals doped with Yb. Sharp PL lines are observed in the 1.0 µm region for these crystals. These PL lines are assigned to2F5/2→2F7/2transition of the spin-orbit split states of the Yb3+ion in the chalcopyrite crystal lattice.
Metal Alloy Characteristics in Rapid Thermal Process System Using a Tungsten Halogen Lamp
Authors: Lee Dong-Youb , Choi Jin-Ho
Published: October 2002

A rapid thermal processing (RTP) system operated below 500°C has been designed and constructed. It uses an optical pyrometer for measuring wafer temperature, in the sensing range from 2.0 µm to 2.4 µm. To remove the interference effect of IR emitted from lamps, an IR filter which uses water is adopted. The electrical characteristics of an alloy after RTP are superior to those of an alloy processed in a conventional furnace, from in the viewpoint of junction spiking, contact resistance and pn diode characteristics. The optimal RTP conditions for aluminium alloy is 425°C for 10 s. The reverse leakage current (at V=5 V) after RTP decreases from 44.9 nA/cm2 to 29.3 nA/cm2 in the p+n diode. Also, in the n+p diode, the leakage current decreases from 122 pA/cm2 to 85.3 pA/cm2.
Effective Channel Length and Source-Drain Series-Resistance Determination after Electrical Gate Length Verification of Metal-Oxide-Semiconductor Field-Effect Transistor
Authors: Chang Ting-Huan , Lo Jenn-Gee , Kuo Tung-Cheng , Hsu Charles Ching-Hsiang , Yu Swei-Yam , Tseng Kun-Fu , Lu Luke Su
Published: October 2002

A new technique of determining the effective channel length by directly measuring source-drain series resistance of metal-oxide-semiconductor field-effect transistors (MOSFETs) was proposed. By using MOSFETs with scaled gate lengths, the source-drain series resistance can be obtained from a device whose source and drain regions are connected. In order to determine whether a MOSFET's source and drain are connected, a `difference of total resistance' (DTR) method, which can also be used to electrically determine the gate length of a normal MOSFET after the fabrication process, was developed in this study. The effective channel length can then be extracted from the obtained series resistance and I–V of MOSFETs. This technique, although it requires very short-gate-length devices, is not affected by source-drain series-resistance gate bias dependence issue encountered in conventional I–V methods.
Gettering Properties in Praseodymium-Added Crystal Growth
Authors: Chang Liann-Be , Cheng Yi-Chang , Wang Hung-Thung
Published: October 2002

Both Auger and secondary ion mass spectroscopy (SIMS) measurements were carried out to give a direct evidence of the impurity gettering phenomena of the rare earth (RE) element Praseodymium (Pr) for the first time during liquid phase thin crystal film growth. Sullur and praseodymium intentionally co-added samples were grown and a significant (around two orders of magnitudes) decrease in the sullur concentration was reported.