bluuebunny/crossref_metadata_2025 huggingface dataset:
Improvement of Heterojunction Donor/Acceptor Organic Photovoltaic Devices by Employing Additional Active Layer
Authors: Triyana Kuwat , Yasuda Takeshi , Fujita Katsuhiko , Tsutsui Tetsuo
Published: July 2005

Single-heterojunction (HJ) donor/acceptor photovoltaic devices composed of copper phtalocyanine (CuPc) and 3,4,9,10-perylenetetracarboxylic bis-benzimidazole (PTCBI) sandwiched between indium–tin–oxide (ITO) and Ag top electrode were investigated. An improvement in device performance was obtained by inserting another perylene derivative, 3,4,9,10-perylenetetracarboxylic diimide (PTCDI) between the CuPc and the PTCBI layers. In this case, the PTCDI and the PTCBI act as an active layer and a buffer, respectively. The active layer increased the absorption efficiency of incident photons, while the buffer provided an ohmic contact with the Ag top electrode. The power conversion efficiency (PCE) was improved from 0.81% for the reference device (without a PTCDI layer) to 1.13% for the optimized single-HJ device (with a PTCDI layer). The concept found in the single-HJ device was introduced into the stacked tandem triple-HJ devices. The improvement of power conversion efficiency, however, was achieved by inserting the PTCDI layer between the PTCBI and the top electrode.
Effect of Indium-Tin Oxide Surface Micromodification and Improvement of Long-Wavelength Sensitivity on Photovoltaic Properties of Photovoltaic Cell with Conducting Polymer/C60 Interpenetrating Heterostructure
Authors: Hashimoto Yuuki , Umeda Tokiyoshi , Mizukami Hiroyoshi , Fujii Akihiko , Ozaki Masanori , Yoshino Katsumi
Published: July 2005

Photovoltaic cells, with a conducting polymer/C60 interpenetrating heterostructure fabricated by spin-coating a conducting polymer onto a C60 thin film, have been investigated and demonstrated a high efficiency as solar cells based on organic materials. The photovoltaic properties of the photovoltaic cell with a structure of indium-tin oxide (ITO)/C60/poly(3-hexylthiophene)/Au have been improved by the micromodification of the ITO surface and codeposition of metal-free phthalocyanine and C60.
Influence of 3,4,9,10-Perylene Tetracarboxylic Dianhydride Intermediate Layer on Molecular Orientation of Phthalocyanine
Authors: Sakurai Takeaki , Kawai Shunsuke , Fukasawa Ryosuke , Shibata Jo , Akimoto Katsuhiro
Published: July 2005

The influences of a 3,4,9,10-perylene tetracarboxylic dianhydride (PTCDA) layer on the molecular orientation and crystalline structure of phthalocyanine (H2Pc) films grown on PTCDA/glass structures were studied by X-ray diffraction analysis, grazing incidence X-ray diffraction analysis, atomic force microscopy and infrared reflection absorption spectroscopy. The orientation of the H2Pc molecular plane became parallel to the substrate surface with the introduction of a thin PTCDA layer on a glass substrate, although the molecular plane of a H2Pc film without a PTCDA layer was almost perpendicular to the substrate surface. Such a parallel orientation of the H2Pc molecular plane was observed even when the PTCDA layer thickness was only 5 Å. It was found that the intensity of the optical absorption of a H2Pc film is significantly influenced by the molecular orientation of H2Pc, and the importance of controlling this molecular orientation is suggested.
Versatile Portable Device for Solid-State Electrical Measurements of “Soft” Materials
Authors: Asanuma Hidehiko , Liu Yong-Jun , Yu Hua-Zhong
Published: July 2005

We describe a versatile portable prototype device for electrical measurements of “soft” materials. It consists of a custom-made micromanipulator and a gas-tight syringe to hold a mercury mini-drop to make reliable and controllable electrical contacts with solid-state materials of interest. Compared with the conventional method (deposition of thin metal films under vacuum), the proposed experimental approach is simpler and more cost-effective.
Performance Test of Fresnel Zone Plate with 50 nm Outermost Zone Width in Hard X-ray Region
Authors: Suzuki Yoshio , Takeuchi Akihisa , Takano Hidekazu , Takenaka Hisataka
Published: July 2005

A microfocusing experiment for hard X-rays has been performed to evaluate the performance of Fresnel zone plate optics. A tantalum Fresnel zone plate with an outermost zone width of 50 nm and a thickness of 0.5 µm has been fabricated by electron-beam lithography. The focused beam size measured by a knife-edge scan is 58 nm in full-width at half-maximum for the first-order diffraction at an X-ray energy of 8 keV. It can be concluded that this zone plate has nearly diffraction-limited resolution in the hard X-ray region. The measured diffraction efficiency is 5% at 8 keV. The spot size using the third-order focus of the zone plate is measured to be approximately 30 nm.
Design of Compact Monochromatic Tunable Hard X-Ray Source Based on X-band Linac
Authors: Dobashi Katsuhiro , Fukasawa Atsushi , Uesaka Mitsuru , Iijima Hokuto , Imai Takayuki , Sakamoto Fumito , Ebina Futaro , Urakawa Junji , Akemoto Mitsuo , Higo Toshiyasu , Hayano Hitoshi
Published: July 2005

A compact tunable monochromatic (1 to 10 percent bandwidth rms) hard X-ray source based on laser-electron collisions for medicine is proposed. An X-band linac is introduced to realize a remarkably compact system. We have designed a compact monochromatic tunable hard X-ray source as a demonstration. An X-band (11.424 GHz) linac for the purpose is being manufactured. Numerical considerations using CAIN code and luminosity calculations have been performed to estimate the X-ray yield. An X-band thermionic-cathode RF gun and an RDS (round detuned structure) X-band accelerating structure are applied to generate a 50 MeV electron beam with 20 pC/micro-bunch, 1 µs macro-pulse. The total X-ray yield by laser-electron collision with the electron beam and Q-switch Nd:YAG laser with a pulse intensity of 2 J/10 ns is 107 photons/RF-pulse (108 photons/s in 10 pps). We will adapt the technique of laser pulse circulating to increase the X-ray yield up to 108 photons/pulse (109 photons/s). Twenty eight percent of the photons with an energy spread of 10% rms are expected to be available by collimating the scattering angles of X-ray photons.
Low Pressure Plasma Confined in a Miniature Cylindrical Chamber and Its Application for In-Situ Elemental Analysis
Authors: Lie Tjung Jie , Kurniawan Hendrik , Hedwig Rinda , Pardede Marincan , Tjia May On , Idris Nasrullah , Kobayashi Takao , Lee Yong Inn , Kagawa Kiichiro
Published: July 2005

A unique miniature vacuum chamber made of a quartz tube has been devised for in situ spectrochemical analysis on samples with arbitrary curved surfaces. The dynamical analysis of the spatially integrated time profile of Pb I 405.7 nm and Hα emission lines showed that the cylindrically confined plasma at a low pressure in the miniature chamber was generated by the shock wave mechanism. The result of measurement of standard samples with various chromium concentrations showed an excellent linear calibration curve. Application of this new technique was carried out on a variety of samples having different shapes. It was found that the elements contained in the samples were clearly detected, including hydrogen impurities in the solid samples. It was further demonstrated that for samples with extremely rough surfaces, which prevent the attainment of low pressure, the use of helium gas flowing through the chamber instead of air still allowed the generation of low background plasma at atmospheric pressure.
Electrical Conductivity of Polymer Composites Filled with Carbon Black
Authors: Horibe Hideo , Kamimura Tomosumi , Yoshida Kunio
Published: July 2005

Conducting polymer composites filled with carbon black (CB) exhibit a positive temperature coefficient (PTC) effect. It is desirable to develop these composites with a low resistivity at room temperature and with a high PTC intensity. We evaluated the dependence of the PTC properties of the composites on the type and crystallinity of the component polymers, and the content and particle size of CB. Among the crystalline polymers investigated, we found that high-density polyethylene (HDPE) has the lowest resistivity at room temperature and the highest resistivity after polymer melting. The higher the crystallinity of HDPE, the lower the resistivity of the composites. The resistivity of the composites decreased with increasing CB content. The smaller the CB particle size, the lower the resistivity of the composites. We developed composites with a low resistivity at room temperature and a high resistivity after polymer melting. The resistivities of the composite consisting of 45 wt% HDPE and 55 wt% CB were 0.17 Ω cm at room temperature and 930 Ω cm after polymer melting.
Fabrication of Integrated Chip with Microinductors and Micro-Tunable Capacitors by Complementary Metal–Oxide–Semiconductor Postprocess
Authors: Dai Ching-Liang , Tsai Chih-Hao
Published: July 2005

In this study, we investigate the fabrication of integrated chips with microinductors and a micro-tunable capacitor using the standard 0.35 µm single polysilicon four-metal (SPFM) complementary metal–oxide–semiconductor (CMOS) and a postprocess. Two inductors-planar spiral and conical spiral-are fabricated and tested. The postprocess has two main steps: One step is the removal of a metal from sacrificial layers and the etching holes in structures using phosphoric acid. The other is the etching of a silicon substrate using tetramethyl ammonium hydroxide (TMAH) to increase the distance between the inductors and the silicon substrate, thereby reducing substrate loss and increasing the quality (Q) factor of the inductors. Experimental results show that the maximum Q factors of the conical spiral and planar spiral inductors were 4.6 at 3.5 GHz and 4.7 at 4 GHz, respectively, following the postprocess. The self-resonance frequency of the conical spiral inductor exceeded that of the planar spiral inductor.
New Shell Structures and Their Ground Electronic States in Spherical Quantum Dots (II) under Magnetic Field
Authors: Asari Yusuke , Takeda Kyozaburo , Tamura Hiroyuki
Published: July 2005

We theoretically studied the electronic structure of the three-dimensional spherical parabolic quantum dot (3D-SPQD) under a magnetic field. We obtained the quantum dot orbitals (QDOs) and determined the ground state by using the extended UHF approach where the expectation values of the z component of the total orbital angular momentum <\hatL

z
> are conserved during the scf-procedure. The single-electron treatment predicts that the applied magnetic field (B) creates k-th new shells at the magnetic field of B

k
=k(k+2)/(k+1)ω0 with the shell-energy interval of \hbarω0/(k+1), where ω0(=\hbar/m
*
l
0
2) is the characteristic frequency originating from the spherical parabolic confinement potential. These shells are formed by the level crossing among multiple QDOs. The interelectron interaction breaks the simple level crossing but causes complicated dependences among the total energy, the chemical potential and their differences (magic numbers) with the magnetic field or the number of confinement electrons. The ground state having a higher spin multiplicity is theoretically predicted on the basis of the quasi-degeneracies of the QDOs around these shells.
In Situ Transmission Electron Microscope Observation of Carbon Nanotubes in Electric Fields
Authors: Okai Makoto , Fujieda Tadashi , Hidaka Kishio , Muneyoshi Takahiko , Yaguchi Tomio
Published: July 2005

Transmission electron microscope is used to examine the movements of carbon nanotubes in electric fields. Carbon nanotubes lying along the surface of the cathode electrode start to move into alignment with the electric field vector when the field strength reaches 0.5 V/µm and become increasingly well-aligned with the vector as field strength increases. The carbon nanotubes return to their original positions when the electric field strength returns to zero. We also examine the abrupt breakdown of carbon nanotubes when the electric field is maintained at 5.5 V/µm. The corresponding breakdown emission current density is estimated as 3.4×107 A/cm2. The distance between the nearest nanotubes standing to align with the electric field vector is approximately 2 µm. This fact means that emission site density could be increased up to 3×107 points/cm2 (which corresponds to one tube for each 2 µm square).
Transmission Electron Microscopy and Electron Energy-Loss Spectroscopy Analysis of Hydrogenated Nanostructured Graphite Prepared by Mechanical Milling
Authors: Muto Shunsuke , Kimura Tomohiko , Tanabe Tetsuo , Kiyobayashi Tetsu , Maruyama Tadashi
Published: July 2005

Hydrogen trapping sites in hydrogenated nanostructured graphite (HNG) prepared by mechanical milling under hydrogen atmosphere were intensively studied with transmission electron microscopy (TEM) and electron energy-loss spectroscopy (EELS). Measurements of σ- and π-plasmon dispersion and 1s→2p
* excitation spectra of the graphitic matrix suggested the existence of at least two types of hydrogen trapping states: one was the conventional C–H covalent bond, and the other was related to the π-orbitals of the carbon atoms extending normal to the graphene layers. We found that iron carbide particles incorporated as contamination during the mechanical milling also stored a significant amount of hydrogen, as revealed by the change in the Fe-L
2,3 spectrum when the sample was annealed. We re-assigned the assumed hydrogen trapping sites to the hydrogen desorption peaks in the thermal desorption spectrum (TDS) based on these experimental results.
Growth of Carbon Nanowalls on a SiO2 Substrate by Microwave Plasma-Enhanced Chemical Vapor Deposition
Authors: Tanaka Kei , Yoshimura Masamichi , Okamoto Atsuto , Ueda Kazuyuki
Published: July 2005

We investigated the growth process of carbon nanowalls (CNWs) on a SiO2 substrate by microwave plasma-enhanced chemical vapor deposition (MPECVD). It is revealed that the CNWs are grown at the fine-textured structure on the SiO2 and the growth process does not require the catalyst. The CNW initially has a semicircular shape. The height, thickness, and mesh size increase with growth time. It is found that the height of CNWs as a function of time obeys the square root law. Extremely high growth rate, approximately 10 µm/h, is achieved, in contrast to previous studies.
CoFe-Coated Carbon Nanotube Probes for Magnetic Force Microscope
Authors: Kuramochi Hiromi , Akinaga Hiroyuki , Semba Yasuyuki , Kijima Mihoko , Uzumaki Takuya , Yasutake Masatoshi , Tanaka Atsushi , Yokoyama Hiroshi
Published: July 2005

CoFe-coated carbon nanotube (CNT) probes have been successfully fabricated by a radio-frequency sputtering method. The sputtering conditions for obtaining a uniform ferromagnetic film on the CNT probe were investigated. The optimal sputtering conditions were determined from the observations using a scanning electron microscope and an atomic force microscope. CNT magnetic force microscope (MFM) probes prepared under optimized conditions provided us clear images with an ultimate lateral resolution of approximately 10 nm.
Optical Band Gap of Barium Titanate Nanoparticles Prepared by RF-plasma Chemical Vapor Deposition
Authors: Suzuki Keigo , Kijima Kazunori
Published: July 2005

The size dependence of the band gap for barium titanate nanoparticles prepared by RF-plasma chemical vapor deposition was investigated by measuring the diffuse reflectance spectra. The band gap of the indirect transition gradually increased, as the particle sizes decreased to less than 11.5 nm. Consequently, the band gap for particles of 6.7 nm in size was measured to be 3.47 eV, which was approximately 0.25 eV larger than that of BaTiO3 bulk. This phenomenon was discussed on the basis of quantum confinement model.
Embedded Ultra High Density Flash Memory Cell and Corresponding Array Architecture
Authors: Lee Kung-Hong , Wu Meng-Yi , Dai Sen-Hue , King Ya-Chin
Published: July 2005

A novel flash memory cell fabricated by standard complementary metal oxide semiconductor (CMOS) logic process and its corresponding array architecture is presented. The cell which consists of two metal-oxide-semiconductor field effect transistors (MOSFET) in series is programmed by channel current induced drain avalanche hot hole and erased by channel hot electron injection. With novel operation principles and array architecture, a feature-sized n-MOSFET per non-volatile memory bit is successfully demonstrated and the CMOS-process-based flash cell size can be as small as multi-gated flash memory. The smallest bit area of a CMOS-process-based flash memory cell with good programming and erasing characteristics along with endurance up to 105 cycles, 10 years excellent read disturbance and data retention characteristics of data retention at 150°C is proposed. With its small cell size and full compatibility with standard CMOS logic process, the novel flash memory cell can be easily adapted in highly integrated very large scale integration (VLSI) systems.
Low-Voltage-Signaling CMOS Receiver with Dynamic Threshold Control
Authors: Tsuda Kazunori , Arima Yutaka , Asano Tanemasa
Published: July 2005

We propose a low-voltage-signaling complementary metal oxide semiconductor (CMOS) receiver with dynamic threshold control. The proposed dynamic threshold control receiver (DTCR) can be realized with a simple CMOS circuit, using a variable logic threshold inverter (VT-INV) consisting of two variable-channel-size MOSFETs (VS-MOSs). The characteristics of the DTCR are evaluated using a test circuit, and its capability for high-frequency-noise filtering is confirmed.
Flexible and Extendible Neural Stimulation Device with Distributed Multichip Architecture for Retinal Prosthesis
Authors: Pan Yi-Li , Tokuda Takashi , Uehara Akihiro , Kagawa Keiichiro , Nunoshita Masahiro , Ohta Jun
Published: July 2005

We have proposed and designed a flexible and extendible neural stimulation device based on a distributed multichip architecture. The device is intended for retinal prosthesis application. A 4×4 array of small (600 µm×600 µm) unit chips was designed and fabricated with 0.6 µm standard complementary metal-oxide semiconductor (CMOS) technology. A package technology for a flexible retinal stimulation device has also been developed. We have demonstrated the function and feasibility of the device as a retinal stimulator in a saline environment.
Directional Crystallizing Si Films with a Fundamental Continuous Wave Yttrium Aluminum Garnet Laser (Zone Melting for Film)
Authors: Sotani Naoya , Hasegawa Isao , Ide Daisuke , Nohda Tomoyuki , Yamano Koji
Published: July 2005

To form large-grained polycrystalline-silicon (poly-Si) films on glass substrates, we propose a new lateral crystallization method, zone melting for film, which uses a high-power fundamental continuous wave yttrium aluminum garnet (CW-YAG) laser and an absorption layer. The laser's infrared light is changed into thermal energy at the absorption layer and heats the amorphous Si (a-Si) film. Next, the Si film is zone-melted and solidified in one direction with a scanning laser beam. By this method, columnar structured Si films were successfully formed with scanning velocities from 400 to 1000 mm/s. Very large typical grains of 1 or 2 µm by few hundreds of µm were obtained on both glass and quartz substrates, and the long axes of the grains were almost parallel to the laser scanning direction. Textures were also observed in these columnar structured Si films. Recombination carrier lifetimes of these films were several times longer than those of conventional low-temperature-processed poly-Si films.
A CMOS Monocycle Pulse Generation Circuit in a Ultra-Wideband Transmitter for Intra/Inter Chip Wireless Interconnection
Authors: Saha Pran Kanai , Sasaki Nobuo , Kikkawa Takamaro
Published: July 2005

In this paper we present a simple circuit for generating the monocycle pulses required in a time hopping ultra-wideband transmitter for an intra/inter chip wireless interconnection system. The monocycle pulse, which has a wide bandwidth, is obtained from damped sinusoidal signals generated from a resistance-inductance-capacitance circuit with a low pass resistance-capacitance filter, transmission gate and digital control circuit. A single-chip implementation of this circuit based on 0.18 µm CMOS technology and results of its simulation named “HSPICE” are presented in this paper. The simulation shows that the generated monocycle pulse has wide bandwidth characteristics. The developed circuit consumes low power (4.4 mW) and occupies a small area (0.19 mm2).
Right-Brain/Left-Brain Integrated Associative Processor Employing Convertible Multiple-Instruction-Stream Multiple-Data-Stream Elements
Authors: Hayakawa Hitoshi , Ogawa Makoto , Shibata Tadashi
Published: July 2005

A very large scale integrated circuit (VLSI) architecture for a multiple-instruction-stream multiple-data-stream (MIMD) associative processor has been proposed. The processor employs an architecture that enables seamless switching from associative operations to arithmetic operations. The MIMD element is convertible to a regular central processing unit (CPU) while maintaining its high performance as an associative processor. Therefore, the MIMD associative processor can perform not only on-chip perception, i.e., searching for the vector most similar to an input vector throughout the on-chip cache memory, but also arithmetic and logic operations similar to those in ordinary CPUs, both simultaneously in parallel processing. Three key technologies have been developed to generate the MIMD element: associative-operation-and-arithmetic-operation switchable calculation units, a versatile register control scheme within the MIMD element for flexible operations, and a short instruction set for minimizing the memory size for program storage. Key circuit blocks were designed and fabricated using 0.18 µm complementary metal-oxide-semiconductor (CMOS) technology. As a result, the full-featured MIMD element is estimated to be 3 mm2, showing the feasibility of an 8-parallel-MIMD-element associative processor in a single chip of 5 mm×5 mm.
Quantum Mechanical Corrected Simulation Program with Integrated Circuit Emphasis Model for Simulation of Ultrathin Oxide Metal-Oxide-Semiconductor Field Effect Transistor Gate Tunneling Current
Authors: Li Yiming , Yu Shao-Ming , Lee Jam-Wem
Published: July 2005

In this paper we present a quantum mechanical corrected gate tunneling current model for simulating ultrathin oxide metal-oxide-semiconductor (MOS) devices. By approximating the physically based Esaki-Tsu tunneling formula and explicitly modeling the classical (CL) and quantum mechanical (QM) corrected surface potential, this model successfully predicts the gate tunneling current for ultrathin oxide MOS samples under different applied biases. Simply assuming all tunneling electrons have the same kinetic energy, the Esaki-Tsu tunneling formula is first simplified so that it can be solved without encountering numerical integral problems. Numerical solutions of the classical Poisson equation and Schrödinger-Poisson equations are then used to analytically express the CL and QM corrected surface potentials explicitly in terms of substrate doping, thickness of the gate oxide (T
ox), and applied bias. The full explicit, physical-based, and QM corrected gate tunneling current model quantitatively shows good agreement with the technology computer-aided design (TCAD) simulation. Compared with the measured gate tunneling current from fabricated 0.12 µm n-type Metal-Oxide-Semiconductor Field Effect Transistors (NMOSFETs) with three different thicknesses of gate oxide, T
ox=1, 1.2 and 1.5 nm, the QM corrected gate tunneling current model shows good accuracy for various ultrathin oxide samples under different biases. However, the gate tunneling current model with the CL surface potential results in one order of magnitude underestimation in comparison with the measured data. We implement the gate tunneling current model into the simulation program with integrated circuit emphasis (SPICE) simulator and perform a DC simulation. Simulated results preliminarily show the effect of the gate leakage current on the drain current without any numerical convergence problem.
Device Design of Direct Tunneling Memory (DTM) Using Technology Computer Aided Design (TCAD) for Low-Power RAM Applications
Authors: Tashiro Hiroko , Tsunoda Kouji , Sato Akira , Nakanishi Toshiro , Tanaka Hitoshi
Published: July 2005

Direct tunneling memory (DTM) is a floating-gate (FG) memory with ultra thin tunnel oxide. Using technology computer aided design (TCAD) to optimize the device parameters, we tried to prolong the retention time of DTM without degrading the operation speed. It has become clear that FG depletion, high substrate concentration, and source/drain offset from FG are essential techniques of improving the retention time. As a consequence, there is the prospect of simultaneously achieving fast program/erase time of 30 ns and long retention time of 10 s with an operation voltage of 3.3 V and tunnel oxide thickness of 1.2 nm.
Novel Nitrogen Doped Ni Self-Alingned Silicide Process for Nanoscale Complementary Metal Oxide Semiconductor Technology
Authors: Oh Soon-Young , Yun Jang-Gn , Huang Bin-Feng , Kim Yong-Jin , Ji Hee-Hwan , Kim Ui-Sik , Cha Han-Seob , Heo Sang-Bum , Lee Jeong-Gun , Wang Jin-Suk , Lee Hi-Deok
Published: July 2005

In this paper, 1%-nitrogen doped nickel was proposed to improve the thermal stability of Ni-silicide for nano-scale N-type Metal Oxide Semiconductor Field Effect Transistor. It is shown that thermal stability of nickel silicide is improved a lot by the Nitrogen incorporation in NiSi layer using the 1%-nitrogen doped nickel target. Even after post-silicidation annealing at 650°C for 30 min, the low resistivity NiSi with low junction leakage current can be achieved. Moreover, improved device characteristics such as threshold voltage, transconductance, and on-off current, subthreshold slope were obtained in 80 nm NMOSFET.
Novel Shallow Trench Isolation Process from Viewpoint of Total Strain Process Design for 45 nm Node Devices and Beyond
Authors: Ishibashi Masato , Horita Katsuyuki , Sawada Mahito , Kitazawa Masashi , Igarashi Motoshige , Kuroi Takashi , Eimori Takahisa , Kobayashi Kiyoteru , Inuishi Masahide , Ohji Yuzuru
Published: July 2005

In this paper, a novel shallow trench isolation (STI) process is proposed for 45 nm node technologies and beyond. The major features of this process are the use of a fluorine-doped (F-doped) SiO2 film for gap filling and high-temperature rapid thermal oxidation (HT-RTO) for gate oxidation. Voidless filling of a narrow trench can be realized by F-doped high-density plasma chemical vapor deposition (F-doped HDP-CVD). Moreover, electron mobility degradation caused by STI stress and junction leakage currents can be minimized using F-doped HDP-CVD with HT-RTO. It was also confirmed that compressive stress in the F-doped HDP-CVD sample is smaller in every measurement point around STI than that in the conventional HDP-CVD sample by convergent-beam electron diffraction (CBED). The Si-F bonds in the oxide film play a very important role in stress reduction. By utilizing HT-RTO, Si-F bonds remain and make the SiO2 film in the trench coarse. This technique is a very promising 45 nm node STI scheme with high performance and high reliability.
Suppression of Boron Penetration from Source/Drain-Extension to Improve Gate Leakage Characteristics and Gate-Oxide Reliability for 65-nm Node CMOS and Beyond
Authors: Hayashi Takashi , Yamashita Tomohiro , Shiga Katsuya , Hayashi Kiyoshi , Oda Hidekazu , Eimori Takahisa , Inuishi Masahide , Ohji Yuzuru
Published: July 2005

Boron penetration from the poly-silicon gate to the silicon substrate through gate dielectrics is a crucial problem in the dual gate complementary metal-oxide semiconductor (CMOS) process. Therefore, the plasma nitridation technique has been studied well, and it has succeeded to suppress boron penetration. However, boron penetration occurs not only from the doped poly-silicon gate but also from the substrate, and resulting in several degradations of gate-oxide characteristics. On the other hand, the boron concentration of source/drain (S/D) extension has been increasing with gate shrinkage. We found that boron penetration from the S/D extension becomes a crucial problem in gate leakage and gate-oxide integrity, particularly for nanoscale positive-channel MOS (pMOS). In this study, we examined several treatments in detail to suppress boron penetration from the S/D extension, and demonstrated that the plasma nitridation treatment after gate etching is the best solution for 65-nm node CMOS and beyond.
Realization of In Situ Doped n-Type and p-Type Si-Microprobe Array by Selective Vapor-Liquid-Solid (VLS) Growth Method
Authors: Islam Md. Shofiqul , Ishino Hiroshi , Kawano Takeshi , Takao Hidekuni , Sawada Kazuaki , Ishida Makoto
Published: July 2005

In this paper we report the development of n-type and p-type Si-microprobe arrays fabricated by using in situ doping in vapor-liquid-solid (VLS) growth employing a gas-source molecular beam epitaxy (GS-MBE) system as the growth environment. VLS growth using Si2H6 only gives intrinsic Si microprobes with the resistivity of ∼104 Ω-cm, which decreases to ∼10-2 Ω-cm after phosphorous diffusion at 1100°C. However, by incorporating in situ doping into the VLS growth method, more conductive probes (resistivity ∼10-3 Ω-cm) can be realized at a temperature less than 700°C. The site and diameter of the VLS-grown probe can be controlled and the growth rate is higher than that of a poly-Si or epitaxial Si crystal grown by the vapor-solid (VS) method. Due to the low processing temperature, in situ doping is effective for realizing highly conductive probe arrays with smart sensor devices by a standard IC process followed by VLS growth. The wide range of doping leads to the possibility of using these probes for the fabrication of vertical active devices such as diodes and transistors.
Device Design Consideration for 50 nm Dynamic Random Access Memory Using Bulk FinFET
Authors: Han Kyoung-Rok , Choi Byung-Kil , Park Tai-su , Yoon Euijoon , Chung In-Young , Lee Jong-Ho
Published: July 2005

Device design using body-tied fin field effect transistor (bulk FinFET) was considered for the application to 50 nm DRAM technology. We concentrated on the device characteristics such as threshold voltage (V
th), off-state leakage current (I
off), subthreshold swing (S.S), and drain induced barrier lowering (DIBL) by controlling lightly doped drain (LDD) profile of the bulk FinFET. Bulk FinFETs with 0 to 3 nm non-overlap between source/drain (S/D) to gate electrode show lower I
off, S.S, and DIBL than those with an overlap while maintaining reasonable threshold voltage. We also compared characteristics of the triple gate bulk FinFET with those of the double gate bulk FinFET. Finally, electrical characteristics with LDD doping profile, S/D to gate overlap length, top gate oxide thickness, body doping concentration, fin top doping concentration, and doping profile from the edge to the center of the fin body are also compared.
Atomistic Approach for Nanoscale Devices at the Scaling Limit and Beyond– Valley Splitting in Si
Authors: Rahman Anisur , Klimeck Gerhard , Lundstrom Mark , Boykin Timothy B. , Vagidov Nizami
Published: July 2005

Band-structure effects on channel carrier density in the ultrathin-body end of the ITRS roadmap silicon (100) n-type metal oxide semiconductor field effect transistors (MOSFETs) are assessed here using a semi-empirical nearest-neighbor sp3d5s* tight-binding model with spin-orbit interaction. The calculations focus on the body thickness range between 10 and 18 atomic layers (∼1.5–2.5 nm). At this range, the standard effective mass approach is limited by its inability to capture the conduction band nonparabolicity effects and the subband splitting. The tight-binding simulations show interesting effects of ground-state subband splitting in this thickness range, and as a result of this, the channel charge density was found to fluctuate by as much as 30%. Additionally, it was observed that strict process tolerance is necessary in this thickness range in order to maintain an acceptable threshold voltage variation.
Robust Metal/AHO/HSG-Cylinder Capacitor Technology Using Diagonal Cell Array Scheme and Double Mold Oxide
Authors: Kim Seong-Goo , Hyun Chang-Suk , Park Don , Cho Tai-Heui , Moon Hong-Joon , Kim Hyun-Chul , Jung Jae-Hwang , Kim Sun-Joon , Kang Hyuck-Jin , Jeong Sang-Moo , Lee Si-Woo , Lee Sung-Hyun , Suk Jong-Gyu , Jeon Young-Soo , Jeon Sang-Kil , Hong Hyeong-Sun , Lee Kang-Yoon , Oh Kyung-Seok
Published: July 2005

In this paper the novel robust Hemispherical Grain (HSG)-merged Al2O3/HfO2 (AHO) capacitor with diagonal cell array scheme and double mold oxide (DMO) is introduced. The capacitor process with diagonal cell array scheme and double mold oxide can maximize storage node (SN) height up to 2.0 µm in 0.11 µm dynamic random access memory (DRAM) technology by enlarging the bottom size of SN. Also we developed the HSG-merged AHO capacitor for the first time in mass production. The HSG-merged AHO capacitor technique exhibited a capacitance enhancement by 24% without any significant decrease in breakdown voltage compared to Al2O3 (ALO) capacitor.
A New Well Capacity Adjusting Scheme for High Sensitivity, Extended Dynamic Range CMOS Imaging Pixel Sensors
Authors: Lai Cheng-Hsiao , Yu Yueh-Ping , King Ya-Chin
Published: July 2005

An embedded 3T active-pixel complementary metal oxide semiconductor (CMOS) image sensor, fabricated with a standard 0.25-µm CMOS logic process with new well capacity adjusting scheme is proposed to extend dynamic range. The photo-sensing device consists of a photo-gate area and a photo-diode, and the well capacity is adjusted by controlling the pulse voltage on the photo-gate. Besides, the imaging sensitivity can be improved through optimizing the photo-gate to photo-diode area ratio and the pulse high level of photo-gate voltage. The experimental results demonstrate that the pixel can achieve both high sensitivity at low illumination and extended dynamic range of 25 dB under high illumination.
Reverse CoSi2 Thermal Stability and Digitized Sheet Resistance Increase of Sub-90 nm Polysilicon Lines
Authors: Lo Cheng-Yao , Peng Yuan-Ching , Chen Yen-Ming , Tu George C. , Lin Shyue-Shyh , Chen Wei-Ming
Published: July 2005

An equation for quantifying the CoSi2 thermal stability of polysilicon lines ranging from 50 nm to 2 µm is proposed for the first time. In contrast to the intuitive thinking of narrower lines having a worse thermal stability, the equation predicts the weakest thermal stability occurring at the super nominal line in 90 nm technology. An interesting phenomenon of digitized resistance increase is also reported for the first time.
Adsorption Behavior of Various Fluorocarbon Gases on Silicon Wafer Surface
Authors: Hidaka Atsushi , Yamashita Satoru , Ishii Hidekazu , Kato Takeyoshi , Tanahashi Naoki , Kitano Masafumi , Goto Tetsuya , Teramoto Akinobu , Shirai Yasuyuki , Ohmi Tadahiro
Published: July 2005

An analytical technique to clarifying the adsorption behavior of a fluorocarbon gas, which is one of the key steps in reactive ion etching, has been established. In this paper, we focus on the adsorption behavior of fluorocarbon gases to the silicon wafer surface to clarify the etching mechanism in order to realize etching to a high aspect ratio. Each fluorocarbon gas had surface selectivity for SiO2, Si and the photoresist. Each fluorocarbon gas reacted differently at the silicon wafer surface. As a result, the etching mechanism could be clarified using this newly established analytical technique. Therefore, an etching mechanism will be able to be clarified by applying the newly established analytical technique to the fluorocarbon gases expected to be useful for etching of high aspect ratio and further high performance ultra large scale integrated circuit device must be realized.
Color Tracking Analysis of the Fringe-Field-Switching Cell Using a Liquid Crystal with Negative Dielectric Anisotropy
Authors: Song Je Hoon , Rhee John Moon , Lee Chan Jae , Moon Dae Gyu , Han Jeong In , Lee Seung Hee
Published: July 2005

Color tracking in a fringe-field driven homogenously aligned nematic liquid crystal cell [named fringe-field switching (FFS)] has been investigated. In the in-plane switching (IPS) device and the FFS device using liquid crystals (LCs) with negative dielectric anisotropy (-LC), the LCs rotate almost in plane except for surfaces where the color tracking occurs for cell retardation value that shows a maximal transmittance. In the IPS device, authentic color appears at a very low cell retardation value that exhibits a low transmittance and bluish white. However, the FFS device shows authentic color even at a relatively high cell retardation value 0.30 µm so that high transmittance and greenish white are kept.
Effect of Fluorine on Interface Characteristics in Low-Temperature CMIS Process with HfO2 Metal Gate Stacks
Authors: Sasaki Takaoki , Akasaka Yasushi , Miyagawa Kazuhiro , Hoshi Takeshi , Watanabe Yasuhiko , Ootsuka Fumio , Yasuhira Mitsuo , Arikado Tsunetoshi
Published: July 2005

In this paper, the effects of fluorine into HfO2 interface region by a low-temperature process are described. The new process for incorporating fluorine in the interface region has been optimized, and it has been found that fluorine terminates the interface defect. As a consequence, an ideal interface has been realized, which improves the negative bias temperature instability (NBTI) in metal gate electrode devices fabricated by the low-temperature process.
Design and Fabrication of MOS Device Circuits with Reticle-Free Exposure Method
Authors: Wakasugi Katsuhiko , Wakimoto Satoshi , Nakada Akira , Ohshima Ichiro , Kubota Hiroshi , Nakamura Kazumitsu
Published: July 2005

An arbitrary pattern exposure method employing a liquid crystal display (LCD) for the formation of projection images has been applied to the design and fabrication of metal oxide semiconductor (MOS) devices and circuits. In this process, a transparent-type LCD with 1024×768 pixels and a g-line stepper were used. To realize the global pattern alignment on the stepper, we newly arranged an LCD reticle fitting the LCD on a quartz reticle which has a conventional alignment mark suitable for the stepper, in place of a conventional glass reticle. The MOS devices has been newly designed and fabricated with four layers in order to evaluate this new lithography concept. It has been confirmed that the n-MOS device can be correctly fabricated by this concept with reducing the manufacturing time. From the results, it is convinced that this method has the potential for replacing conventional glass reticles, particularly in the trial stage of device development.
Process Integration Issues on Mo-Metal-Gated MOSFETs with HfO2 High-k Gate Dielectrics
Authors: Aoyama Takayuki , Nara Yasuo
Published: July 2005

We investigate a MoN
x
/HfO2 gate stack fabricated using a gate-first process flow. We ideally etch the MoN
x
/HfO2 gate stack using a Cl2-O2 gas system. The work function variation of MoN
x
gates is more than 0.7 eV. The work function can extensively cover the energy of the band gap of Si except that near the conduction band. In addition, we show issues on thermal budget from N diffusion in Mo and the reaction of Mo with HfO2. We propose that thin-SiN insertion between MoN
x
and HfO2, and a decrease in Mo thickness are useful in fabricating process windows. On the basis of the results, we fabricate metal-oxide-semiconductor (MOS) devices and show their excellent characteristics.
Precise Frequency-Drift Measurement of Extended-Cavity Diode Laser Stabilized with Scanning Transfer Cavity
Authors: Matsubara Kensuke , Uetake Satoshi , Ito Hiroyuki , Li Ying , Hayasaka Kazuhiro , Hosokawa Mizuhiko
Published: July 2005

A simple and effective method for stabilizing laser frequencies using scanning transfer cavities and a stabilized helium–neon laser was applied to extended-cavity diode lasers near 866 nm and 397 nm. The frequency drift of the stabilized 866 nm laser measured using an optical frequency synthesizer was smaller than 200 kHz for 1 h. The square root of the Allan variance was 1×10-10 at an averaging time of 103 s.
Molecular Dynamics Calculation for Low-Energy Ion Implantation Process with Dynamic Annealing Effect
Authors: Kwon Oh-Seob , Seo Ji-Hyun , Kim Ki-Dong , Won Tae-Young
Published: July 2005

In this paper, we present a molecular dynamics (MD) study on a low-energy ion implantation process for nanoscale CMOS (Complementary Metal Oxide Semiconductor) processes. To model the profiles of interstitials and vacancies, the recoil interaction approximation (RIA) was employed, while the kinetic Monte Carlo (KMC) approach was used for modeling the dynamic annealing effect between cascades. The simulation results performed for as-implanted boron profiles were compared with the results of the binary collision approximation (BCA) calculation by UT-MARLOWE as well as with the experimental SIMS data. The simulation revealed that the dynamic annealing effect between cascades is essential for the accurate estimation of defect distribution as well as as-implanted ion distribution. The dynamic annealing effect was carefully investigated for a case of boron implantation with an ion implantation energy of 2 keV, doses of 1×1014 ions/cm2 and 1×1015 ions/cm2, and a dose rate of 1×1012 ions/cm2·s.
Effects of Post CF4 Plasma Treatment on the HfO2 Thin Film
Authors: Lai Chao Sung , Wu Woei Cherng , Fan Kung Ming , Wang Jer Chyi , Lin Shian Jyh
Published: July 2005

In this study, a novel approach was proposed to improve the characterization of HfO2. Fluorine was incorporated by CF4 plasma to improve the HfO2 gate dielectric properties including leakage current, breakdown voltage and hysteresis. The hysteresis of capacitance–voltage characteristics can be reduced to approximately 10% hysteresis voltage for the samples with CF4 plasma treatment. An inner-interface trapping model is presented to explain the hysteresis. The secondary-ion mass spectroscopy (SIMS) results show that there is a significant incorporation of fluorine (F) at the interface between the HfO2 thin film and silicon substrate. The incorporation of F effectively suppressed leakage current and improved carrier trapping without an increase in interfacial layer thickness.
Single-Frequency Tunable Fiber Ring Laser Based on Erbium-Doped Waveguide Amplifier and Double Filters
Authors: Chien Hung-Chang , Yeh Chien-Hung , Lee Chien-Chung , Chi Sien
Published: July 2005

We have proposed and experimentally demonstrated a single-longitudinal-mode tunable fiber ring laser based on an erbium-doped waveguide amplifier (EDWA) and two filters composed of a Fabry–Perot laser diode and a fiber Fabry–Perot filter. The side-mode suppression ratio (SMSR) of >32.6 dB/0.05 nm and the output power of >1.4 dBm over a wide tuning range from 1525.22 to 1565.45 nm in steps of 1.11 nm have been achieved for this ring laser. The power fluctuation of <0.1 dB and central wavelength variation of <0.01 nm also can be obtained.
Cubic-HfN Formation in Hf-Based High-k Gate Dielectrics with N Incorporation and Its Impact on Electrical Properties of Films
Authors: Koyama Masato , Kamimuta Yuuichi , Koike Masahiro , Ino Tsunehiro , Nishiyama Akira
Published: July 2005

We examined the effect of the annealing conditions on cubic-HfN (c-HfN) segregation in N-incorporated hafnium aluminate (HfAlON). Low-temperature activation (850°C, 30 min) leads to the inhibition of c-HfN segregation in HfAlON, which occurs at 1000°C for 30 s. This results in a reduced leakage current of the film in the 850°C annealing. k values of HfAlON (k ∼22) higher than those of hafnium aluminate are confirmed, through the polarization enhancement by Hf-N bonds without a long-range order of c-HfN. We also checked c-HfN segregation in N-incorporated HfO2 (HfON) and N-incorporated hafnium silicate (HfSiON), by changing the annealing conditions. HfON causes the segregation of Hf2NO2 and c-HfN at the 1065°C spike, whereas HfSiON maintains a homogeneous structure. We also found that, in the case of an excessive annealing of 1050°C for 30 min, HfSiON decomposes to HfO2/c-HfN. We think that the phase separation is thermodynamically favorable in N-incorporated Hf-based dielectrics at this temperature, however, HfSiON is fully sustainable under practical activation conditions for conventional complementary metal-oxide-semiconductor logic devices.
Temperature Dependence of Porogen Desorption from Low-k Porous Silica Films Incorporated with Ethylene Groups
Authors: Uchida Yasutaka , Maruyama Yoshiyuki , Katoh Tomohiro , Ito Yoshito , Ishida Koichi
Published: July 2005

The temperature dependence of porogen desorption from low-k silica films incorporated with ethylene groups was investigated. Total-reflection X-ray measurement indicated that porogen desorption characteristics strongly depended on temperature and time. The time required for film annealing at 400°C was 3 h, while that required for film annealing at 375°C was 8 h. These results were confirmed by temperature desorbing spectra measurement. The film vacuum annealed at 375°C for 8 h did not show that the peaks came from porogen.
Fabrication of Crystalline HfO2 High-κ Dielectric Films Deposited on Crystalline γ-Al2O3 Films
Authors: Okada Takayuki , Shahjahan Mohammad , Sawada Kazuaki , Ishida Makoto
Published: July 2005

Crystalline HfO2/γ-Al2O3 gate stacks were successfully fabricated by evaporating the HfO2 film on crystalline γ-Al2O3/Si substrates at 500°C. In the fabrication, crystalline γ-Al2O3 assisted the crystallization of the HfO2 film, which was deposited without the degradation of surface morphology. The electrical characteristics of the crystalline HfO2/γ-Al2O3 stacked dielectric and amorphous HfO2 unstacked dielectric were compared. The leakage current density of the stacked dielectric was lower than that of the unstacked dielectric. The HfO2 layer deposited on the crystalline γ-Al2O3/Si showed a higher dielectric constant than the amorphous HfO2 unstacked dielectric. It was also observed that the frequency dependence of the flat-band voltage shift of the stacked dielectric was negligible and different from that of the unstacked dielectric. These results indicate that crystalline γ-Al2O3 films prevented the formation of an interface layer between HfO2 and Si substrates. The crystalline γ-Al2O3 films work well as buffer layers and may be available for future high-κ gate stack application.
Direct Comparison of ZrO2 and HfO2 on Ge Substrate in Terms of the Realization of Ultrathin High-κ Gate Stacks
Authors: Kamata Yoshiki , Kamimuta Yuuichi , Ino Tsunehiro , Nishiyama Akira
Published: July 2005

Direct comparison of ZrO2 and HfO2 on Ge substrates was performed in terms of the realization of an ultrathin gate stack with low leakage current. Changes in the interfacial layer thickness, film dielectric constant and leakage current upon postdeposition annealing were investigated. Considerable thinning of the interfacial layer due to interdiffusion with ZrO2 was observed after annealing. Moreover, the high dielectric constant of ZrO2 was retained even after Ge incorporation by interdiffusion. These phenomena resulted in a small capacitance equivalent thickness (CET) of 1.2 nm. On the other hand, the interfacial layer under the high-permittivity (high-κ) film remained almost the same for HfO2 on Ge stack, resulting in a relatively large CET of 1.6 nm. Together with the fact that the leakage current is lower for the ZrO2 stack than that for the HfO2 stack, ZrO2 is considered to be preferable to HfO2.