bluuebunny/crossref_metadata_2025 huggingface dataset:
Improved I-V Characteristics of Polysilicon Thin Film Transistors with Novel Dual-Buffer Drain Structure
Authors: Ching-Fa Yeh Ching-Fa Yeh , Chyi-Hsiang Chern Chyi-Hsiang Chern
Published: October 2002

ON/OFF current ratio of poly-Si TFTs has been improved by using a novel structure called the dual-buffer drain (DBD). The new DBD TFT not only reduces the anomalous off-current, but also maintains a high on-current. It mainly combines features of the double-gate and the field-induced drain structures, so that owns advantages of low electric field near the drain junction and good drain junction characteristics. Furthermore, it will be shown that the DBD TFT is superior in off-current stability to the FID TFT. Finally, we will discuss high voltage operation for the DBD TFT.
Atomic Force Microscopy Investigation of Tensile-Stressed Silicon Grown by Rapid Thermal Chemical Vapour Deposition on Si0.68Ge0.32Relaxed Pseudo-substrates
Authors: Chollet Frederic , Warren Patricia , Didier Dutartre Didier Dutartre , Elie Andre Elie Andre
Published: October 2002

Rapid thermal chemical vapour deposition (RTCVD) has been applied to the growth of silicon layers under tensile stress on relaxed Si0.68Ge0.32buffer layers at 610 and 810°C. Their surface morphology was characterised with atomic height resolution by Tapping-mode atomic force microscopy (TM-AFM). While a uniform isotropic nanoroughness is revealed on pseudo-substrates, a quite different roughness can be observed for silicon films. For high temperature grown films, high surface diffusion rates of adsorbed species enable an extended reconstruction of the Si (100) surface: large domains showing terraces as well as faceted planes appear; the resulting non-uniform silicon film exhibits early mechanical failure. In contrast, low temperature grown Si films exhibit almost the same morphology as pseudo-substrates for thicknesses up to 15 nm with no apparent mechanical failure. For thicknesses beyond 20 nm, terraces form on the steepest part of the slopes, whereas beyond 80 nm <110> slip lines indicate the plastic yield of the film.
Low Dark Current and High-Speed Metal-Semiconductor-Metal Photodetector on Sulfur-Treated InP
Authors: Han Il Ki , Her June , Byun Young Tae , Lee Seok , Woo Deok Ha , Lee Jung Il , Kim Sun Ho , Park Kwang Nam Kang
Published: October 2002

We report on a metal-semiconductor-metal (MSM) photodetector on
sulfur-treated undoped InP. We show that the dark current and capacitance of
the sulfur-treated detector are 100 times lower and 30% smaller than those of
the untreated detector, respectively. The improved performance of the detector
characteristics is understood in terms of Fermi level depinning and the
existence of a thin layer of InP
x
S
y
between the contact metal and
semiconductor due to sulfur treatment. We found that it is necessary to anneal
the sulfur-treated substrates at 270°C to obtain such improved device
characteristics. The reason is attributed to the formation of thermally stable
In–S bonds.
Quantum Size Effects in Amorphous Diamond-like Carbon Superlattices
Authors: Silva S. Ravi P. , Amaratunga Gehan A. J. , Woodburn Charles N. , Haq Mark E. Welland
Published: October 2002

Evidence for the existence of quantum size effects in amorphous diamond-like carbon superlattice structures from optical and electronic measurements together with theoretical predictions are reported. A `blue shift' in the optical gap is shown to occur with decreasing well width from which an effective mass for the electrons (and holes) is obtained. Regions of negative differential resistance are observed in the current-voltage characteristics at temperatures ranging from 4–300 K. Dark conductivity studies point to a current that is dominated by a tunnelling component rather than thermal carrier emission over the barrier layers of the superlattice. Activation energy studies show an increase in the activation energy with decreasing well width, in keeping with the observed optical `blue shift'. The voltage range over which negative differential resistance is measured agrees well with resonant tunnelling predictions.
Reversible Photowriting and Thermal Erasing of Ag Patterns on Ag-Rich Ag–Ge–S Films
Authors: Takeshi Kawaguchi Takeshi Kawaguchi , Shigeo Maruno Shigeo Maruno
Published: October 2002

The photoinduced surface deposition (PSD) of metallic Ag has been studied for its application to new optical recording devices, using Ag-rich Ag–Ge–S films. The Ag pattern written using the PSD phenomenon was found to be erased by annealing below the glass transition temperature of the films. The repetition of photowriting and thermal erasing was successful for at least 20 times. From this result, it can be said that the PSD phenomenon is a unique reversible phenomenon involving long-range movement of the constituent atoms. Furthermore, the reversibility is assumed to be an important factor for the application of the PSD phenomenon.
PbMgSrTe and PbSrTeSe Films Prepared by Hot-Wall Epitaxy
Authors: Sakurai Nobuhiro , Matsushita Keiichi , Hiroshi Fujiyasu Hiroshi Fujiyasu , Akihiro Ishida Akihiro Ishida
Published: October 2002

PbSrSe and PbSrTe films were prepared by hot-wall epitaxy, and their characteristics such as energy band gaps, lattice constants and electrical properties were measured and compared with those of PbSrS. The band gaps of Pb1-xSrxSe and Pb1-xSrxTe films increase as dEg/ dx=2.5 eV and dEg/ dx=3.6 eV, respectively. Deviation of the lattice constant of PbSrSe from that of PbSe was very small with Sr composition less than 10%, and PbSrSe/PbSe system is lattice-matched better than PbSrS/PbS system. On the other hand, the lattice constant of PbSrTe increased rapidly with Sr composition. New quaternary semiconductors such as Pb1-x-yMgxSryTe and Pb1-xSrxTe1-ySeyfilms lattice-matched to PbTe were also prepared. Growth and characteristics of these films are also presented.
Estimation of Phase Coherent Length of Hot Electrons in GaInAs Using Resonant Tunneling Diodes
Authors: Kang Young Cheul , Furuya Kazuhito , Michihiko Suhara Michihiko Suhara , Yasuyuki Miyamoto Yasuyuki Miyamoto
Published: October 2002

The relationship between the resonant level width of resonant tunneling diodes
(RTD) and the coherent length of electrons is investigated theoretically. The resonant
level widths were measured using the second derivative of the J-V characteristics
of GaInAs/InP RTDs. Measured data are compared with theory, and it is estimated that
the coherent length of hot electrons is longer than 50 to 90 nm.
Transmission Electron Microscopy Study of the Compositionally Graded InGaAs Layer
Authors: Zuoya Yang Zuoya Yang
Published: October 2002

Two types of molecular beam epitaxy grown InGaAs/GaAs structures with 1-µ m-thick
compositionally graded buffer layer were studied by cross sectional transmission electron
microscopy, plan-view transmission electron microscopy and off-axis convergent beam
electron diffraction (CBED). The observed misfit dislocations in both structures were
distributed in a region from the interface between the graded InGaAs layer and the GaAs
buffer layer up to about 0.6 µ m in the graded layer with a density of
1× 109 cm-2. No dislocations were observed to pin at the upper
interface between the constant and the graded InGaAs layers or within the constant
InGaAs layer itself for the type B structure. Threading dislocations were found to
spread over the majority of the graded layer with Burger's vector of a/2<011>.
CBED was used to determine the local lattice parameters, and thus the corresponding
In composition and relaxation of the layered structures. The accuracy of CBED results
was proved by the double crystal X-ray diffraction data when DCXRD was applicable.
Tersoff's model was used to determine the residual strain in the graded layer by
substituting the measured lattice parameters, giving reasonable results for the graded buffer layer.
Geometry Considerations for Thermal Design of Microwave Heterojunction Bipolar Transistors
Authors: Martin Kärner Martin Kärner , Ulrich Schaper Ulrich Schaper
Published: October 2002

An efficient general algorithm for three-dimensional thermal simulation of semiconductor
chips and its exemplary application to AlGaAs/GaAs heterojunction bipolar transistors
(HBT) is presented. Firstly, the assumption of stationary heat sources as a boundary
condition is validated by pulsed scattering parameter measurements. Secondly, the
simulation method based on the fast Fourier transform is introduced. The model is
verified by liquid crystal thermography, infrared thermography and comparison to
another simulation method. In the third part of the paper, the model is applied to
the self-heating problem in multifinger HBTs. Geometrical design rules for minimization
of the maximum temperature and temperature gradients between the individual emitters
are deduced. A tradeoff between the emitter size, the number of emitters, the power
level and cooling measures such as substrate thinning must be carried out in order
to control the thermal properties with respect to safe operation and reliability.
Study of HF-Treated Heavily-Doped Si Surface Using Contact Angle Measurements
Authors: Yasuhiro Sato Yasuhiro Sato , Masahiko Maeda Masahiko Maeda
Published: October 2002

The surface chemistry of heavily-doped Si treated in a hydrofluoric acid (HF)
solution is evaluated using contact angle measurements. The saturated contact angles of
H2O on hydrophobic Si surfaces are affected by conduction types and dopant
concentrations. Boron-doped surfaces show smaller contact angles, which corresponds to
the larger polar-force interaction energy, than phosphorous-doped surfaces. The polar-force
interaction is due to the hydrogen bondings between Si–OH bonds, which replace Si–F
bonds through hydrolysis reaction in the HF solution, and H2O molecules.
In addition, a marked difference in the hydrogen termination process can be observed,
depending on the surface orientation, during the dip in extremely dilute HF solution.
Influence of Dislocations on the Threshold Current Density of AlGaAs/GaAs/InGaAs Strained Quantum-Well Lasers
Authors: Harris Hiroshi Ito , Jr. Jr.
Published: October 2002

The influence of dislocations on the threshold current density of AlGaAs/GaAs/InGaAs
strained quantum-well lasers has been investigated. The experimental results agree well
with the calculated tendency where the dislocations are assumed to act as recombination
centers. It is revealed that the threshold current density does not significantly increase
when the dislocation density is lower than middle of 106/cm2.
Oriented Bulk Consolidation of Bi–Sr–Ca–Cu–O by Shock-Loading Method
Authors: Kikuchi Masae , Atou Toshiyuki , Hikosaka Hideaki , Fukuoka Kiyoto , Syono Yasuhiko , Kobayashi Norio , Kawamata Shuichi , Okuda Kiichi
Published: October 2002

Shock compaction experiments were carried out for Bi2Sr2CaCu2O

y

particles sorted to 46–74 µ m and packing density of 50–82% at a
shock pressure of 8 GPa. Bulk density reached 95% by shock compaction independent of the
porosity. The most effective orientation was achieved by shock loading for the packing
density of 67% and with post annealing at 870°C. The texture of the shocked
plus postannealed specimen showed crystal growth not only within the c-plane
but also along the c-axis. The Meissner volume fraction of the shock compacted
specimen decreased with decreasing packing density but the onset temperature did not change.
The magnetic torque of shock plus annealed specimen showed the alignment of particles.
Homogeneity of Superconductivity in YBa2Cu3Ox Single Crystals
Authors: Asaoka Hidehito , Ishida Takekazu , Kazumata Yukio , Okuda Kiichi , Takei Kenji Noda
Published: October 2002

We investigated the homogeneity of high-purity YBa2Cu3O

x

(123)
single crystals at different oxygen concentrations by means of the higher-harmonic susceptibility.
The superconductivity of the onset temperature at 93.8 K was observed in the samples of
the hypostoichiometric composition (x=6.87). Also, we succeeded in obtaining the 123
single crystals of the optimum stoichiometry (x=7.00) which showed a sharp single transition
at 92.5 K corresponding to occurrence of the homogeneous superconductivity.
Structure and Magnetic Properties of Mechanically Ground ε-Fe2.3N
Authors: Kim Kyu-Jin , Sumiyama Kenji , Hideya Onodera Hideya Onodera , Kenji Suzuki Kenji Suzuki
Published: October 2002

The structure and magnetic properties of mechanically ground ε- Fe2.3N
alloy powders have been investigated by X-ray diffraction, vibrating sample magnetometer
and Mössbauer spectroscopy. Even after milling of 300 h, the ε- Fe2.3N
alloy powders form only nanocrystallites and yield no phase transformation. Saturation
magnetization of ε- Fe2.3N initially increases and then becomes
constant, indicating the homogeneous distribution of N atoms.
Effect of Damping Constant on Switching of Hexagonal Platelet Particle
Authors: Nakatani Yoshinobu , Hayashi Nobuo , Uesaka Yasutaro , Fujiwara Hideo
Published: October 2002

The effect of Gilbert's damping constant α of a hexagonal platelet particle
and the effect of the angle of the applied field on switching are investigated by computer
simulation. The switching time decreases with the decrease of α in the range of
0.01<α<1 and becomes almost constant at α<0.01; the switching time is
the time interval between the application of field and the earliest point at which the
average magnetization in the easy direction becomes zero. The switching time decreases
with the increase of the angle between the applied field and the easy direction. The
oscillation amplitude of the average magnetization in the easy direction increases
with the decrease of α, decreases with the increase of the presetting field,
and increases with the increase of the angle between the applied field and the easy direction.
Dual-Wavelength Operation of a Flashlamp Pumped Narrow-Linewidth Ti:Sapphire Laser
Authors: Takeda Hideki , Yousuke Akabane Yousuke Akabane , Fumihiko Kannari Fumihiko Kannari
Published: October 2002

Dual-wavelength operation of a flashlamp-pumped Ti:sapphire laser employing a modified grazing-incidence
grating resonator with two tuning mirrors is described. Spatially resolved laser spectra in the output beam at
the near field indicate that a large part of each wavelength laser beam oscillates in the separated gain volume.
Linewidth of ∼16 pm is achieved for both laser wavelengths. Simultaneous second-harmonic generation of the dual-wavelength laser is also demonstrated in the spectral range of 390–420 nm with a β-BaB2O4 nonlinear crystal.
The phase-matching angle of each wavelength is automatically satisfied in a fixed optical arrangement by using four dispersive prisms and a lens.
Eye-Safe Compact Mie Scattering Lidar Using a Diode-Laser-Pumped Nd:YAG Laser for Measuring the Atmospheric Boundary Layer
Authors: Matsui Ichiro , Kubomura Hiroyuki , Imoto Hiroshi , Nobuo Sugimoto Nobuo Sugimoto
Published: October 2002

An eye-safe compact Mie scattering lidar for atmospheric boundary layer measurement
was developed. The lidar employs a low-pulse-energy high-repetition-rate Q-switched Nd:YAG
laser pumped by cw diode lasers. The vertical profiles of aerosols measured with the
lidar were found to have sufficient signal-to-noise ratio for observing the structure
of the atmospheric boundary layer which plays an important role in air pollution phenomena.
Disk Noise of Quadrilayer MnBi Magneto-Optical Disks
Authors: Masafumi Nakada Masafumi Nakada , Mitsuya Okada Mitsuya Okada
Published: October 2002

Disk noise of quadrilayer MnBi magneto-optical disks with grooved glass substrates
was investigated. Both reflectivity noise and polarization noise of MnBi disks were
20 dB higher than those of TbFeCo disks. The degree of c-axis orientation of a
hexagonal MnBi layer, which is inversely proportional to fluctuation in the magnetization
direction, and Mn oxide in a MnBi layer are not dominant origins of the high disk noise.
Bi layers 20 nm in thickness on grooved substrates have many hillocks over 50 nm in
height at land edges. Noise reduction of 10 dB can be achieved by using a flat glass
substrate. Surface roughness on the Bi layers is one of the main causes of high disk noise of MnBi disks.
High Contrast Thin Film Electroluminescent Devices on Textured Glass
Authors: Benalloul Paul , Barthou Charles , Poels Jacques Benoit
Published: October 2002

In order to enhance the contrast of thin-film electroluminescent devices, special
textured glasses are considered. The performances and the resolution of the pixel are
preserved and the specular reflectance of the Al rear electrode is lowered to a value of 3%.
Photoluminescence of Si Microcrystals Embedded in SiO2 Glass Films
Authors: Kohno Kenji , Osaka Yukio , Toyomura Fumitaka , Katayama Hideyuki
Published: October 2002

Si microcrystals were doped into SiO2 glass film by the rf magnetron sputtering
technique. The average diameter of Si microcrystals was estimated by transmission electron
microscopy observation. The dependence of photoluminescence of Si microcrystals on the
average diameter is discussed in detail. The absorption of Si microcrystals and the
photoluminescence for the larger diameter (≥ 3 nm) seem to be determined by
the bulk property of a quantum dot. For the smaller diameter (≤ 3 nm), surface
effects of a quantum dot seem to play a role in the photoluminescence. The experimental
line shape of the PL spectrum was explained theoretically by the inhomogeneous broadening
of the size distribution function of a quantum dot for the larger diameter (> 3 nm).
Dielectric and Electrostrictive Properties of Pb(Zn1/3Nb2/3)O3–Pb(Mg1/3Nb2/3)O3–PbTiO3 Ceramic Solid Solutions
Authors: Zhu Xinhua , Tan Yan , Wang Qun , Zhaohui Cai Zhaohui Cai , Zhongyan Meng Zhongyan Meng
Published: October 2002

Perovskite-type ferroelectric ceramics of the Pb(Zn1/3Nb2/3)O3–PbTiO3–Pb(Mg1/3Nb2/3)O3
ternary system have been synthesized by the columbite method. The dielectric and
electrostrictive properties of the present ternary system have been investigated
from the view point of actuator materials. With increasing Pb(Zn1/3Nb2/3)O3
content, the peak value of the dielectric constant decreased; however, the Curie
temperature increased. Using suitably selected compositions and sintering process,
material has been obtained with Curie temperature near room temperture, dielectric
constant above 12000, and transverse strain near -3–-4×10-4 induced
at an applied electric field of 20 kV/cm.
Effects of Anchoring Strength in Poly(vinyl alcohol)/Liquid Crystal Composite Films with Interface Layers
Authors: Hiroshi Ono Hiroshi Ono , Nobuhiro Kawatsuki Nobuhiro Kawatsuki
Published: October 2002

The electrooptical properties of three kinds of poly(vinyl alcohol) (PVA)/liquid
crystal (LC) composite films with three combinations of added photocurable mixtures of
benzylacrylate (BzA) and perfluorooctylethylacrylate (FA-108), benzylmethacrylate (BzMA)
and FA-108, and nonaoxyethylenediacrylate (9EG-A) and FA-108 were studied paying special
attention to the LC droplet size and the anchoring energy at the interface between the
polymer and the LC, and effects of photocurable monomers on morphology and electrooptical
properties of PVA/LC composite films with added photocured polymers. The PVA/LC composite
films with added photo-crosslinkable monomers showed a low driving voltage of 15 V
r
m
s

and a low hysteresis of less than 1 V
r
m
s
, suggesting the improvement of
electrooptical properties caused by reduction of the anchoring energy and the thermal dynamics of polymers.
Gas Evaporation in Space
Authors: Wada Nobuhiko , Kato Manabu , Dohi Minoru , Sawai Sinya , Tani Masaaki , Sengoku Masaya , Gotoh Toshiaki , Toshikazu Sato Toshikazu Sato , Tosiaki Noda Tosiaki Noda
Published: October 2002

Silver (Ag) was evaporated in argon (Ar) and xenon (Xe) gases at various pressures in the low-gravity environment aboard the space shuttle. Four glass bulbs with filament tips coated with 50 mg of silver were filled with
Ar gas of 6.7 Pa (A) or 40 Pa (B) or Xe gas of 0.67 Pa (C) or 1.33 Pa (D) and ignited one by one in the low
gravitational field of space. The evaporation temperatures were maintained at 1150°C at which smoke plumes
were barely detectable in all cases in the ground experiment. A ball of smoke particles appeared to grow around
the evaporation source instead of rising as it would under earth gravity conditions. No smoke was observed in
(A), but it was observed in (B) and (C) and bursts of smoke extended in various directions from the smoke ball
in the case of (D). The experiment suggested that vapor could be confined locally around the source with high
pressure and temperature by the surrounding gas in the low gravity. This suggestion cannot be derived from any
conventional model of evaporation in the gas.
Preparation and Electrochromic Properties of RF-Sputtered NiOx Films Prepared in Ar/O2/H2 Atmosphere
Authors: Kitao Michihiko , Izawa Kuniyuki , Urabe Kazuo , Komatsu Takeshi , Kuwano Saburou , Yamada Shoji
Published: October 2002

The preparation of electrochromic nickel oxide ( NiO

x

) films, which are
colorless in an as-deposited state, has been carried out in Ar/O2/H2 mixed
gas by the rf-sputtering method. Highly transparent films of as-deposited nickel oxide
could be prepared in the sputtering atmosphere consisting of Ar:O2:H2=50:10:40.
From IR and XPS measurements, the as-deposited films were found to be hydrated and to
have the component of Ni(OH)2. When these films were electrochemically colored,
NiOOH was known to remain in the films. The coloration efficiency of the films at the
wavelength of 633 nm was nearly independent of hydrogen content in sputtering atmosphere
up to 40%, but it depended on sputtering pressure. The maximum value of coloration efficiency
was 36 cm2/C for films prepared at hydrogen content of 40% and total pressure of 8 Pa.
Preparation of Conductive and Transparent Thin Films by Argon Ion Beam Sputtering of Zinc Oxide in Atmosphere Containing Hydrogen
Authors: Kohiki Shigemi , Nishitani Mikihiko , Wada Takahiro
Published: October 2002

Conductive and transparent thin films of zinc oxide were prepared by argon ion
beam sputtering of a zinc oxide target. The films, deposited at room temperature in
an atmosphere containing hydrogen, typically showed the conductivity of
3.8×102/ Ω· cm. An increase of the hydrogen/argon ratio
brought about an increase of carrier concentration, which was reflected by an increase of the
absorption energy of the optical spectra.
Development and Surface Evaluation of Large SiC X-Ray Mirrors for High-Brilliance Synchrotron Radiation
Authors: Yamaoka Hitoshi , Uruga Tomoya , Arakawa Etsuo , Matsuoka Masaru , Ogasaka Yasushi , Yamashita Koujyun , Ohtomo Norio
Published: October 2002

Flat SiC mirrors coated with Pt, of which size are 800?50 mm2 and 1000?140 mm2 in area, are developed for
high-brilliance synchrotron radiation. The large mirrors are well polished over the entire area from the viewpoint
of surface roughness for application to the use for the synchrotron radiation beamline. The performance of the
large mirror surface is evaluated by the measurements of not only reflectivity near the critical angle but also of
the angle-resolved scattering (ARS) curve as a function of mirror surface position at several glancing angles with
CuK? X-rays from a rotating target at the 30-m-long X-ray beamline facility of ISAS. By analyzing the ARS curves the power spectral density functions are derived as a function of the surface wave number. It is suggested
that the large mirror may have a fractal surface finish like that of small mirrors. Evaluation of the longitudinal
mirror curvature on the order of 10 km from the reflected beam profile width is also described. The results are
compared with the measurements of the laser interferometers.
Effect of the Silicidation Reaction Condition on the Gate Oxide Integrity in Ti-polycide Gate
Authors: Lee Nae-In , Young-Wug Kim Young-Wug Kim , Sung Tae Ahn Sung Tae Ahn
Published: October 2002

The effect of the silicidation reaction between the sputtered titanium film and underlying polysilicon on the gate oxide integrity in the Ti-polycide gate was studied. The gate oxide breakdown failure increased with increasing silicidation temperature for both cases of 1-step and 2-step silicidation processes. This is related to increased amount of Ti diffusion from Ti-silicide to the gate oxide. However, for 1-step silicidation process reliability of the gate oxide for 750° C silicidation is better than for 650° C silicidation. This is because of the formation of the metastable C49 structure when solid-state reaction between the sputtered titanium film and underlying polysilicon occurs. Therefore, to obtain better reliablility of the Ti-polycide gate low temperature silicidatlon and the stable C54 phase are essential.
Extending the Lifetime of Optical Lithography Technologies with Wavefront Engineering
Authors: Marc D. Levenson Marc D. Levenson
Published: October 2002

Various types of phase shifting mask, off-axis illumination, optical proximity
correction and other innovations promise to extend the lifetime of i-line (365 nm) and
deep ultra-violet (DUV) optical lithography technologies into the subhalf-micron era.
No single innovation seems likely to produce a patterning paradigm that lasts more than
one generation, but engineering solutions using combinations of new options and familiar
technologies may make optical technology viable well into the next century.
2×2 Phase Mask for Arbitrary Pattern Formation
Authors: Watanabe Hisashi , Pati Yagyensh C. , Pease R. Fabian
Published: October 2002

The phase-shifting mask (PSM) extends the resolution limit of optical lithography.
The major hurdle to the widespread use of PSMs is that high resolution can be obtained
only for the limited pattern layouts with the PSMs. In this paper, we describe the
double exposure method with a pair of 2 phase masks (“2×2 phase mask”)
for arbitrary two-dimensional pattern formation. Simple mask design procedures which
are based on a few rules are derived from the imaging characteristics of alternating PSMs.
With a 2×2 phase mask, complicated patterns including large scale integration
(LSI) patterns are successfully fabricated.
Performance of Dipole Illumination Combined with Pupil Filter
Authors: Seiji Orii Seiji Orii , Tetsuya Sekino Tetsuya Sekino
Published: October 2002

The pupil filtering technique has been proposed as an effective method in the field of optics. In this work, pupil
filtering is applied to an optical lithography system. We theoretically analyze partially coherent imaging, and not
only the pupil filter but one combined with other optical elements, is suggested. Through these two methods, the
following results are obtained: 1) twofold enhancement of depth of focus (DOF) and resolution limit improved to
0.26 µm (i-line, 0.60 NA) for lines and spaces, using the pupil filter combined with oblique illumination, i.e., dipole
illumination; 2) twofold enhancement of DOF for hole, using the pupil filter assisted by a mask, i.e., shifterless
halftone mask. In this paper, several calculations and experimental results of using an i-line stepper with pupil
filtering are presented and the potential for pupil filtering in optical lithography is discussed.
Evaluation of Incoherent-Type Pupil Filter: Spatial Filter for Incoherent Stream
Authors: Hirukawa Shigeru , Shiraishi Naomasa , Matsumoto Yuichiro Takeuchi
Published: October 2002

A new imaging method using an incoherent type filter, spatial filter for incoherent
stream (SFINCS) is evaluated by experiment. The experiment was done with an i-line N
A0.57
projection lens. The experimental results show the excellent depth-of-focus (DOF) expanding
effect of SFINCS for fine hole patterns with good exposure dose latitude and mask
manufacturing error latitude even if multiple focus exposure (FLEX) is used.
Accuracy Improvement of Shot Leveling and Focusing with Interferometry for Optical Lithography
Authors: Nakayama Yasuhiko , Watanabe Masahiro , Yoshitada Oshida Yoshitada Oshida , Minoru Yoshida Minoru Yoshida
Published: October 2002

This paper describes a new algorithm of shot-by-shot leveling using laser interferometry
for a high resolution stepper system (wave amplitude uniform method). This unifies the
interference fringe and can improve the accuracy of the height and tilt detection deviation.
The effect of the WAUM was verified by simulation. The maximum offset deviation for
tilt and height was proved to be ±2.4 µ rad and ±0.03 µ m respectively.
The performance was evaluated with an Al processed wafer and tilt offset deviation was
proved to be ±6.4 µ rad.
Performance of Resolution Enhancement Technique Using Both Multiple Exposure and Nonlinear Resist
Authors: Shibuya Masato , Komatsu Masaya , Toshihiko Ozawa Toshihiko Ozawa , Hiroshi Ooki Hiroshi Ooki
Published: October 2002

We have proposed a resolution enhancement lithography technique named NOLMEX.
In this paper, we investigate the performance of this method by using the analytical
relationship between line-and-space pattern resolution and N
A, and by numerical
calculation for isolated hole patterns. It is confirmed that this technique is useful
for both kinds of patterns. Using the NOLMEX method, a 0.1-µ m-rule pattern can be
fabricated by optical lithography.
High-Accuracy Defect-Free X-Ray Mask Technology
Authors: Nash Steven C. , Faure Thomas B. , Levin James P. , Puisto Denise M. , Rocque Janet M. , Kimmel Kurt R. , McCord Mark A. , Viswanathan Raman G.
Published: October 2002

There are many material and processing options for building highly accurate
defect-free X-ray masks that meet the 0.25-µ m and smaller lithography
groundrules. IBM's path and rationale for reducing the key mask parameters of image size,
image placement and defects is covered. For image size resolution and control, high
voltage e-beam lithography (greater then 50 kV) is the preferred technique for X-ray
masks. For tighter image placement control, special writing schemes that reduce the
e-beam lithography systematic and random placement errors must be used. Special absorber
electroplating conditions and thermal controls were implemented to control process-induced
distortion. For tight defect control, identifying and eliminating sources of defect is key.
Clearly, for IBM, most of the defect sources were process rather than foreign material related.
Our defect reduction work has resulted in the fabrication of a fully functional 64-Mb DRAM (single chip) mask.
Performance of the Modified Suss XRS 200/2M X-Ray Stepper at CXrL
Authors: Reilly Michael , Leonard Quinn , Wells Gregory , Capasso Cristiano , Anderson Paul , Taylor James , Waldo Whit , Yamazaki Kuniaki , Chen Gong , Simon Klaus , Franco Cerrina Franco Cerrina
Published: October 2002

An XRS 200 model 2M X-ray stepper has been installed at the Center for X-ray Lithography.
This paper describes the capability of the machine and its installation. Of greater
interest is the performance the stepper gives with respect to the dose control and the
mask/wafer alignment. How robust a process is depends on the latitude of each process
parameter and the control tolerance accorded the machines and materials that affect each one.
The dose repeatabillty and uniformity is determined by the optical elements in the beamline,
the helium delivery system, and the accuracy of the scanning stage. Test results are
reported for dose control using three separate methods. The scan speed is measured using
Suss supplied equipment and is verified separately by CXrL's own technique. The dose
delivered is analysed by the response of radiachromic film. Also important is the
behavior and performance of the ALX-100 alignment system. The optical set-up is described
as a model that includes the ALX hardware and illumination as well as the mask and wafer.
The signal and contrast from the mask and wafer are compared to data for several substrates.
A figure of merit is discussed for determining which membranes will give the best overlay.
Ultrahigh-Vacuum Electron Cyclotron Resonance-Plasma Chemical-Vapor-Deposited SiNx Films for X-Ray Lithography Mask Membrane: As-Deposited Properties and Radiation Stability
Authors: Ahn Jinho , Suzuki Katsumi , Tsuboi Shinji , Yamashita Yoshio
Published: October 2002

In this paper, a new approach to improve the radiation stability of silicon nitride
film is presented using an ultrahigh-vacuum electron cyclotron resonance plasma chemical
vapor deposition system. A membrane with a high optical transmittance (∼99% at 633 nm)
can be obtained with a lower SiH4/NH3 flow ratio. The X-ray radiation immunity,
however, can be improved with a higher SiH4/NH3 flow ratio at the sacrifice of optical
transmittance. Shrinkage of the band gap and the generation of energy states in the
band gap with increasing Si/N ratio of the film are speculated to be primary parameters
for improving the radiation stability of silicon nitride film. Hydrogen content in the low
1021 atom/cm3 range, however, does not seem to have a critical effect
on the radiation immunity, even though the Si-H bonds may act as the source for the radiation-induced damage.
X-Ray Mask Inspection Using Replicated Resist Patterns
Authors: Sekimoto Misao , Tsuyuzaki Haruo , Okada Ikuo , Akinori Shibayama Akinori Shibayama , Tadahito Matsuda Tadahito Matsuda
Published: October 2002

A new X-ray mask inspection method using replicated resist patterns is proposed.
It is able to detect fatal opaque defects on the back surface of the mask and at the
bottom of the hole pattern, in addition to those on the front surface. It can also
ignore transparent defects on the mask. This method is useful even for defect detection
on a single-die mask through die-to-die comparison. For the false process defects
occurring during the replication process, a discrimination procedure using a 2-step
die-to-die comparison is proposed. In inspection tests with SEMSpec, we investigate
the relation between the detection sensitivity to small resist defects and the conductive-coating thickness on them.
Improvements of Nanostructure Patterning in X-Ray Mask Making
Authors: Chen Yong , Carcenac Frank , Françoise Rousseaux Françoise Rousseaux , Huguette Launois Huguette Launois
Published: October 2002

In order to evaluate the resolution limits and to achieve a high resolution X-ray
lithography under proximity condition, masks compatible with Karl Suss XRS200 stepper
have been fabricated with a conventional electron beam lithography at 50 keV energy
and a reactive ion etching (RIE) technique for the pattern transfer. It was found that
with a relative thin (300 nm) tungsten absorber 50 nm linewidth and high density
gratings of period down to 120 nm can be fabricated without proximity correction.
Experimental results with gratings of different linewidths and different periods are
analyzed to clarify the process parameter influences on the dose correction. In addition,
the fabricated masks were tested by proximity replication with Karl Suss stepper at a
gap of 5 µ m using synchrotron radiation. Finally the replication results were
discussed in terms of the resolution limit as a function of proximity gap.
Selective Growth of Cubic GaN in Small Areas on Patterned GaAs(100) Substrates by Metalorganic Vapor Phase Epitaxy
Authors: Nagahara Masaki , Miyoshi Seiro , Yaguchi Hiroyuki , Onabe Kentaro , Shiraki Yasuhiro , Ryoichi Ito Ryoichi Ito
Published: October 2002

The metalorganic vapor phase epitaxy growth of cubic GaN in small areas on SiO2-patterned GaAs substrates has been performed. We have succeeded in selective growth without deposition on the SiO2 mask at temperatures between 620 and 675° C. The crystal quality of cubic GaN has been improved through growth in small areas on patterned GaAs substrates. It is found that the grain size becomes larger and the full width at half maximum of the X-ray diffraction peak of cubic GaN becomes narrower on patterned substrates than on unpatterned ones.
Proximity Effect Correction for 1:1 X-Ray Mask Fabrication
Authors: Aya Sunao , Moriizumi Kouichi , Fujino Takeshi , Kamiyama Kinya , Minami Hiroyuki , Kise Koji , Yabe Hideki , Kenji Marumoto Kenji Marumoto , Yasuji Matsui Yasuji Matsui
Published: October 2002

This article describes the improvement of a self-consistent proximity effect correction
to fabricate 1:1 X-ray masks. The present method has two features; the first is the
change of sampling point from pattern edges to the center. This is effictive in saving
on the calculation time, and it is theoretically shown that the deposited energy intensity
at the edge is equal to that obtained with the conventional method. The other is to
combine the pattern shape and additional dose modulations for finer patterns (≤4β f,
β f is the forward scattering range of electrons) with the ordinary dose
modulation method. The algorithm is verified by experiments and simulations, and is
found to be effective in reproducing 0.1 µ m patterns with high accuracy.
Critical Dimension Control of Poly-Butene-Sulfone Resist in Electron Beam Lithography
Authors: Nakamura Kazumitsu , Shy Shi L. , Tuo Chu C. , Huang Chen C.
Published: October 2002

Critical dimension uniformity is one of the key parameters to define the performance
of electron beam lithography as well as the other lithography technologies. The characteristics
of poly-butene-sulfone (PBS), a positive-type electron resist, have been investigated
from the view-point of critical dimension control, using two types of electron beam
lithography systems which use Gaussian spot and variable-shaped beams. It has been
elucidated that the sensitivity of the PBS has a strong relationship with humidity
during development. When the humidity changes from 30% to 32%, the sensitivity
increases corresponding to the increase of 1 µ C/cm2 dosage. A very good critical
dimension uniformity of less than 0.04 µ m has been attained using a variable-shaped
beam at 30% humidity. The spot beam can also obtain a good pattern width uniformity at
32% humidity and 4.5 µ C/cm2 dosage. It is expected to correct the proximity
effect in PBS by selecting the electron dosage related to humidity.
Dissolution Kinetics Analysis for Chemically Amplified Deep Ultraviolet Resist
Authors: Itani Toshiro , Iwasaki Haruo , Masashi Fujimoto Masashi Fujimoto , Kunihiko Kasama Kunihiko Kasama
Published: October 2002

Dissolution kinetics of a chemically amplified deep-ultraviolet (DUV) positive resist,
which consists of tert-butoxycarbonyl (t-BOC)-protected phenolic resin, benzenesulfonic
acid derivative as a photoacid generator (PAG) and an additional dissolution inhibitor,
has been investigated by focusing on the t-BOC-protected phenolic resin structure
(t-BOC protection ratio/molecular weight M
w) and postexposure bake (PEB) temperature.
Based on the analysis of the dissolution rate curve and Arrhenius plots, it was concluded
that only one mechanism, namely, the penetration of tetramethylammonium hydroxide
(TMAH) developer into hydrophobic t-BOC resin, rules the dissolution kinetics. It
was also found that a steep slope of the dissolution rate curve is very effective for
improving resolution capability. Polymer structure, as well as the PEB condition,
was optimized from the correlation between dissolution kinetics and resist performance,
and good resist performance was realized.
Dissolution Study of a Novolak-Based Photoresist Based on a Developer Diffusion Model
Authors: Krasnoperova Azalia A. , Bell Todd , Rhyner Steven , Taylor James W. , DePablo Juan , Franco Cerrina Franco Cerrina
Published: October 2002

Dissolution characteristics of a positive chemically amplified photoresist, AZ-PF514 from Hoechst Celanese,
have been studied. Development rate monitor data for different developer concentrations are analyzed. The
experimental dissolution rates of the X-ray-exposed photoresist are examined in view of the dissolution model
proposed earlier by Reiser. Parameters of Reiser's model associated with the diffusion of an aqueous base through
a thin penetration layer and solubility of a phenolate complex in an aqueous base solution are derived for different
X-ray exposure conditions. Reiser's dissolution model was used to simulate the developed photoresist pattern
profile. An example of 0.25 µm pattern development simulation using a dose-dependent coefficient for diffusion
of a developer base into polymer is demonstrated.
Oxide Etching Using Surface Wave Coupled Plasma
Authors: Akimoto Takeshi , Ikawa Eiji , Sango Toshiaki , Komachi Kyouichi , Katayama Katuo , Ebata Tosiki
Published: October 2002

Oxide etching was evaluated using a new high-density plasma, which was based on
surface wave coupled plasma (SWP). This plasma applicator can uniformly generate microwave
plasma over a large area, and it can be formed without quartz tubes or plates. The plasma
characteristics of SWP were investigated at the low-pressure region. At the First stage,
oxide etching characteristics were evaluated. The SWP oxide etcher had a high etching
rate and achieved quarter-micron window etching of vertical profile.
Microloading Effect in Highly Selective SiO2 Contact Hole Etching Employing Inductively Coupled Plasma
Authors: Fukasawa Takayuki , Kubota Kazuhiro , Shindo Haruo , Horiike Yasuhiro
Published: October 2002

The highly selective SiO2 etching achieved in the downstream region of
the inductively coupled plasma (ICP) employing C4F8+H2 was studied regarding
polymer film deposition characteristics. Polymer deposition into as-etched 0.5 µ m
holes at floating potential showed an overhang feature with C4F8 alone and a
conformal one with C4F8+30%H2. When as-etched 0.5 µ m holes were subjected to
C4F8+30%H2 plasma, the film thickness on bottom surfaces increased
rapidly with increasing self-bias voltages. This result demonstrated that high selectivity
in holes less than 0.8 µ m was achieved by deposition of resputtered film
on the side wall onto the bottom. To analyze the bottom Si surface in deep holes,
a simulated experiment was also performed using a capillary plate with 10 µ mφ
(aspect ratio 40); the Si surface masked by the plate was exposed to plasma, then the
Si surface was measured by X-ray photoemission spectroscopy (XPS). Etching occurred on
the Si surface covered by the fluorine-rich polymer in C4F8 alone, and
carbon-rich film was deposited on the Si surface with addition of 30%H2.
The latter explains the origin of high selectivity.
Characteristics of Indium-Tin Oxide Thin Film Etched by Reactive Ion Etching
Authors: Yokoyama Meiso , Li Jiin Wen , Shui Hsiang Su Shui Hsiang Su , Yan Kuin Su Yan Kuin Su
Published: October 2002

Indium-tin oxide (ITO) films coated on glass have been etched by reactive ion etching
(RIE) with a gas mixture of Ar and Cl2. The etching rates of ITO films depend
strongly on power density, gas pressure, the composition of reactive gases, and the
total flow rate of etchants. According to the results from the study, we can postulate
that the ITO films' etching follows the ion-assisted chemical etching. A high etching
rate above 100 Å/min can be achieved, and an etching mechanism will be proposed.
The selectivity of ITO films to glass reaches 35 with a 30 line/mm pattern. After
exposure of ITO films to an Ar/Cl2 mixed gas plasma discharge, their sheet
resistance does not markedly change. The residue of Cl atoms exists only in the region
near the surface. By means of parameter control, we can obtain good pattern images of
ITO films measured by scanning electron microscopy (SEM).
A Simple and Efficient Pretreatment Technology for Selective Tungsten Deposition in Low-Pressure Chemical Vapor Deposition Reactor
Authors: Chang Kow-Ming , Yeh Ta-Hsun , Chi-Hung Li Chi-Hung Li , Shih-Wei Wang Shih-Wei Wang
Published: October 2002

In this paper we develop a two-step pretreatment method which is a simple but
effective cleaning process that can be used to achieve a high deposition rate and
excellent interface characteristics, as well as improve the selectivity. In the first step,
we use CF4/O2 mixing gases as a plasma etching system without substrate bias.
The removal of damage and contaminants by reactive ion etching (RIE) during contact
hole opening can thus be obtained. We consider that the role of oxygen is first to
oxidize the polymer residues (i.e., fluorocarbons like C

x

F

y

) and
the RIE-damaged regions on the silicon surface, and it is then followed with CF4
to remove these oxides. In experiments, the plasma modification rate can be controlled at
120 Å/min. Results of the high deposition rate, smooth interface, low selectivity
loss and the other improvements are observed. These are superior to those of cases
without pretreatment. The second step is that anhydrous HF cleaning was used to remove
surface oxide which was formed during the first step. Obviously, this new cleaning
technology is very efficient not only for contact hole pretreatment but also for polysilicon
materials. This also implies that this technology may have potential for polycide gate applications.
Deposition and Properties of Reactively Sputtered Ruthenium Dioxide Thin Films as an Electrode for Ferroelectric Capacitors
Authors: Lee Jeong-gun , Choh Suk-ki Min
Published: October 2002

Ruthenium dioxide (RuO2) films are studied for use as a bottom electrode of the (Ba, Sr)TiO3 thin-film capacitor. RuO2 films have been deposited by reactive DC magnetron sputtering of ruthenium at a relatively low
sputtering power. Stoichiometric RuO2 films are obtained at oxygen partial pressures as low as 0.6 mTorr. The
properties of the films have been investigated using techniques such as Rutherford backscattering spectrometry,
Auger electron spectrometry, X-ray diffraction, and scanning electron microscopy. The oxygen composition in
as-deposited RuO
x
films increases from 2.0 to 2.4 with the increase of initial O2 partial pressure from 1.2 to
5.6 mTorr at a sputtering power of 200 W. The films deposited under low oxygen partial pressures followed by
annealing show preferential crystal growth in the [110] direction, whereas those deposited in high oxygen partial
pressures show growth in the [101] direction. A resistivity of 65 µΩ·cm is obtained after annealing at 800°C. Even after high-temperature deposition and subsequent annealing processes, clear interfaces between (Ba, Sr)TiO3
and RuO2 films are obtained.
Fabrication of Multilayers with Growth Controlled by Sequential Surface Chemical Reactions
Authors: Kumagai Hiroshi , Matsumoto Masahiko , Kawamura Yoshiyuki , Obara Koichi Toyoda
Published: October 2002

A multilayer of aluminum oxide and titanium oxide was fabricated with growth
controlled by sequential surface chemical reactions of trimethylaluminum/hydrogen peroxide
for the aluminum oxide layer, and tetrachlorotitanium/hydrogen peroxide for the titanium
oxide layer. Evaluation of the multilayer using a transmission electron microscope and
an X-ray diffractometer indicated that the 1.6 nm thickness of each layer equaled the
design value, and the ratio (Δ2θ/2θ0) of the full width of the
first peak to the center angle of the peak was close to the theoretical minimum.
Focused-Ion-Beam-Induced Gas Etching
Authors: Lloyd R. Harriott Lloyd R. Harriott
Published: October 2002

Focused ion beam (FIB)-assisted gas etching has several advantages over physical
sputtering in many applications. Advantages include etch rate enhancements of one to
two orders of magnitude, dramatically reduced redeposition of etched material on sidewalls
in high-aspect-ratio structures, etch selectivity, and reduced implantation of the
primary ion species in the sample. Applications which benefit from focused ion beam
(FIB) gas etching include photomask and X-ray mask defect repair, integrated circuit
modification for failure analysis, and sample preparation for scanning electron microscope
and transmission electron microscope analysis. This paper describes a simple phenomenological
model which takes into account the ion beam and scanning parameters, gas flux, and
basic material constants. Approximate formulas are given in terms of these parameters
and compared to experimental results.