bluuebunny/crossref_metadata_2025 huggingface dataset:
Reaction of Ozone and H2O2 in NH4OH Solutions and Their Reaction with Silicon Wafers
Authors: Eom Dae-Hong , Lim Geun-Bae , Park Jin-Goo , Busnaina Ahmed A.
Published: February 2005

The main purpose of this study was to evaluate ozone chemistry in NH4OH solutions in terms of oxidizing power compared with H2O2-based NH4OH solutions. The solubility of ozone in the solutions tested was almost nil at room temperature when the solution pH was higher than 9. However, the decrease in solution temperature to 10°C resulted in a dissolved ozone concentration at the ppm level in NH4OH solutions. The slow decrease in pH and the increase in redox potential were measured as functions of ozone injection time in NH4OH solutions at 10°C. The half-life times of peroxide were 40 min and 4 h in 1:1:5 (volume ratio) NH4OH:H2O2:H2O (SC1, standard clean 1) solution at 80 and 50°C, respectively. However, the half-life of ozone at room temperature was less than 2∼ 5 min at the concentrations investigated. The contact angles of bare silicon changed from 72° to less than 5° within 10 s in SC1 at 80°C. In ozonated solutions, change of contact angle to hydrophilic took longer than 3 min depending on the concentration of ozone in NH4OH solutions. The addition of peroxide and ozone significantly reduced the etch rate of silicon in NH4OH solutions. When Al2O3 particles were deposited on silicon wafers, ozonated NH4OH combined use with megasonic power at room temperature could remove more than over 90% of particles from the wafer surface.
Design of Transparent, Half-Metallic Ferromagnetic 4d-Transition-Metal-Doped K2S with High Curie Temperature
Authors: Seike Masayoshi , Sato Kazunori , Yanase Akira , Katayama-Yoshida Hiroshi
Published: February 2005

Curie temperatures are evaluated using first principles in (K,Zr)2S and (K,Nb)2S diluted magnetic semiconductors which have been designed as half-metallic and transparent materials with a large magnetoptical effect. From the total energy differences between the ferromagnetic state and the spin-glass state, estimations of Curie temperatures are achieved by mapping to the Heisenberg model within the mean-field approximation. According to the results, it is possible to fabricate transparent, half-metallic and room-temperature ferromagnets with Zr- and Nb-concentrations of around 5 at%. Effects of additional carrier doping for (K,Mo)2S are also evaluated and it is found that (K,Mo)2S with hole doping (∼5 at%) exhibits transparency, is half-metallic and has room-temperature ferromagnetism.
Effect of Different Quasi-Phase Matchings in Two-Dimensional Nonlinear Photonic Crystal
Authors: Ma Boqin , Ni Peigen , Feng Shuai , Cheng Bingying , Zhang Daozhong
Published: February 2005

The second-harmonic generations (SHGs) of nanosecond pulses using first- and second-order quasi-phase matching (QPM) were realized in a two-dimensional periodically poled LiNbO3with square lattice. Maximum conversion efficiency of 35% and 14% was achieved respectively at the fundamental wavelengths of 1.352 µm and 1.064 µm. In addition, the SHG of 1.064 µm picosecond laser using second-order QPM was also studied in this crystal. Based on the comparison between the SHGs excited by nanosecond and picosecond pulses, it may be concluded that if second-order QPM is used, the incident laser with higher peak power is necessary.
AlGaAs/GaAs Quantum Well Lasers Grown by Metalorganic Chemical Deposition Using Tertiarybutylarsine in Nitrogen Ambient
Authors: Bo Baoxue , Tang Xiaohong , Zhang Baolin , Huang Gensheng , Zhang Yuanchang , Chuan Tjin Swee
Published: February 2005

Using tertiarybutylarsine (TBAs) as the arsenic precursor and the nitrogen as the carrier gas, high-quality AlGaAs/GaAs quantum well (QW) diode laser materials have been grown by metalorganic chemical vapor deposition (MOCVD). Photoluminescence and device measurement studies indicate that the quality of the grown AlGaAs/GaAs laser materials can be comparable to those grown by using AsH3 as the arsenic precursor and hydrogen as the carrier gas. For the first time, a low threshold current density of 200 A/cm2 for 1000 µm cavity length broad area AlGaAs/GaAs lasers has been achieved by this MOCVD growth method. It has been shown that TBAs and nitrogen gas can be employed in MOCVD growth of the widely used AlGaAs/GaAs laser materials, for substituting the highly toxic source gas AsH3 and the highly explosive carrier gas H2.
Optimization of Pit Depth for Concurrent Read Only Memory–Random Access Memory Optical Disk
Authors: Aoyama Nobuhide , Yamashita Satoshi , Kunimatsu Yasukiyo , Hosokawa Tetsuo , Morimoto Yasuaki , Suenaga Masashi , Masafumi Yoshihiro*** Masafumi Yoshihiro*** , Katsusuke Shimazaki*** Katsusuke Shimazaki***
Published: February 2005

We have studied a concurrent read only memory–random access memory (ROM–RAM) optical disk system without laser feedback by optimizing pit depth. When the pit depth was 47 nm (optical depth about 1/11 λ) and the pit width 0.45 µm, about 8% jitter in both pit and magneto-optical (MO) signals was obtained with a 785 nm wavelength laser diode and 0.55 NA objective lens by employing magnetic-field-modulation (MFM) MO recording. Both pit data and MO data were recorded with eight to fourteen modulation (EFM) code with a minimum mark length of 0.83 µm and a track pitch of 1.6 µm and thus the areal density is comparable to 1.3 GB for φ120 mm single sided disk. By the optimization of the pit depth, sufficient system margins for practical use were obtained without laser feed back for the simultaneous reproduction of both pit and MO signals.
Vibronic Structures in Excitation and Emission Spectra Characteristics of O2
- Molecular Ions in KI, KBr and KCl Crystals
Authors: Sarjono S. , Baba M. , Nishidate K. , Ohta K. , Sokolska I. , Ryba-Romanowski W.
Published: February 2005

The excitation and emission spectra of O2
- molecular ions in KI, KBr and KCl crystals have systematically been investigated at 8.7 K. The present results for the emission spectra with zero-phonon lines were in good agreement with previous results. From the temperature dependence of their emissions, we found that the luminescence intensities of O2
- ions still appear at room temperature (RT) and are much stronger than those of other chalcogen molecular ions particularly in a KCl crystal. On the other hand, we found vibronic structures on the low-energy sides of the excitation spectra of KI and KBr:O2
- crystals, showing several peaks with nearly equidistant spacings. The anharmonic vibrational energies of O2
- molecular ions in the excited state were obtained from these energy differences, depending on their lattice constants. Using spectroscopic constants calculated from the experimental data, we could construct a configurational-coordinate diagram for an O2
- center in a KI:O2
- crystal.
Enhancement of Photoresponse by Enlarging the Effective Interface between Conducting Polymer and Titanium Oxide in Photovoltaic Device
Authors: Feng Wei , Umeda Tokiyoshi , Fujii Akihiko , Wang Xiaogong , Yoshino Katsumi
Published: February 2005

The morphology of titanium oxide films, prepared via two different methods, oxidation following the evaporation of titanium and spin-coating a suspension of TiO2 nanoparticles, was investigated by scanning electron micrograph (SEM) and X-ray diffraction (XRD). SEM images indicated that the surface of the TiO2 film is rough and the pore size is large, compared with those of the TiO
x
film, which results from the connected network of the TiO2 film. Pore filling is likely to be easier in the TiO2 film than in the TiO
x
film due to its larger pore sizes. Poly(3-hexylthiophene) (PAT6) chains can be interrupted by the TiO2 network structure, as evidenced in UV-Vis spectrum. XRD revealed better crystallinity in the TiO2 film than in the TiO
x
film. The investigation of the photoluminescence (PL) spectra revealed that PL of PAT6 is quenched when it was filled into the network pores. We prepared the photovoltaic devices using PAT6 as both sensitizer and hole conductor and titanium oxide and PV films as the electron conductor, to reveal the effect of the morphology of the titanium oxide films on the photovoltaic performance. An improvement of conversion efficiency by over twofold in the TiO2 cells compared with that of the TiO
x
cells was observed. These phenomena suggest that the photovoltaic performances of PAT-TiO2 (or TiO
x
)/PV cell were dependent on the interfacial morphology between both PAT6 and TiO
x
and PAT6 and PV.
Effects of Substrates on Properties of Tin Oxide Gas Sensors
Authors: Rue Gi-Hong , Lee Dae-Sik , Lee Duk-Dong
Published: February 2005

SnO2 thin films on three different kinds of substrates (sapphire, alumina, and Si with 1000 Å-thin oxide layer) were grown by a reactive r.f. magnetron sputter method. Epitaxial SnO2 thin film without an apparent grain structure but with high dislocation density along lateral direction to substrate was grown on a sapphire substrate. The microstructure of the thin film was investigated, using the 3C2 beam line from a Pohang Light Source (PLS) consisting of a 2-GeV electron accelerator, 4 circle X-ray diffractometer, and AFM. It was confirmed that the thin film grew epitaxially on the sapphire substrate with variants structure. A large defect density was exhibited on the surface of the epitaxial thin film, which is related to sorption sites reacted with the gas. SnO2 films on the polished alumina and Si substrate showed poly-crystalline structure of tetragonal structure, low resistance of about 10 Ω, and good optical transmittance. An epitaxial SnO2 thin film exhibited the highest sensitivity to combustible gases and a particular sensitivity of 95% to alcohol at 2000 ppm and 350°C. The sensor also showed a good stability with small baseline drift and short reaction times of about 5 seconds, respectively. This experiment confirms substrate effects on characteristics of an SnO2 thin film plus the potential for the application of epitaxial SnO2 film in the production of stable gas sensors.
Ultra High Frequency Riplon Spectroscopy
Authors: Sakai Keiji , Omata Kazuyohi , Takagi Kenshiro
Published: February 2005

Light scattering study of ripplon (surface tension waves of thermal origin) was made at a high frequency range of more than 10 MHz on pure water surface. The observed power spectra were in very good agreement with the theoretical curves strictly derived from the fluctuation dissipation theory. The two approximations currently used for the ripplon analysis were also examined, namely, the first approximation P
1(ω) of two Lorentzian peaks and the second one P
2(ω) with two additional terms of antisymmetric components. Contrary to most expectations, P
1(ω) proved to be a much better approximation than P
2(ω) that has the higher-order terms. The possibility of surface viscosity on the pure water surface was experimentally confirmed by the wide-band frequency measurement. However, the ripplon power spectra obtained up to 40 MHz showed no such evidence.
Applicability of Insensitive Properties of Measured Equation of Invariance Coefficients for Modified Scattering Objects
Authors: Chowdhury N. M. Alam , Takada Jun-ichi , Hirose Masanobu
Published: February 2005

The applicability of insensitive properties of measured equation of invariance (MEI) coefficients for the computation of scattering from modified structured bodies is presented in this letter. During scattering computation by using MEI technique (in IE-MEI or SIE-MEI method), the MEI coefficients of the whole scatterer is calculated in the conventional method. In contrast, using the insensitive properties of the MEI coefficients, the new method calculates the MEI coefficients only around the modified area if some portion of the scatterer is modified and reuse those for the other portion of the scatterer. Thus CPU time for solving the modified problem can be saved by using the new method. The numerical results verified the validity of the new technique which is compared with the available numerical solutions.
Synthesis of Highly Crystalline Multiwalled Carbon Nanotubes by Thermal Chemical Vapor Deposition Using Buffer Gases
Authors: Han In Taek , Kim Ha Jin , Park Young Jun , Jin Yong Wan , Jung Jae Eun , Kim Jong Min , Kim Bum Kwon , Lee Naesung , Kim Seong Keun
Published: February 2005

Multiwalled carbon nanotubes were formed on Fe–Ni–Co alloy-coated glass substrates by infrared-radiation-heated thermal chemical vapor deposition using CO and H2 gases at temperatures as low as 480–580°C. Growth of the carbon nanotubes was strongly affected by Ar or N2 gas introduced during the heat-up stage prior to the growth, which markedly increased the growth rate of carbon nanotubes by an order of magnitude and yielded the carbon nanotubes with better crystallinity and less amount of carbonaceous impurity particles, in comparison with those grown at the same condition but heated in vacuum to the growth temperature. It is proposed that gas-phase energy transfer enhances the synthesis of highly crystalline carbon nanotubes while suppressing the formation of carbonaceous impurity particles.
An Innovative Method for Contact Hole Printing with Binary Mask and Single Exposure
Authors: Yamazoe Kenji , Saitoh Kenji , Suzuki Akiyoshi
Published: February 2005

We have introduced a new method for fine contact hole printing using a specially designed binary mask and modified illumination in a single exposure, which can realize k
1=0.3 lithography. The binary mask has periodic assist holes around the main holes and the illumination is the combination of strong and weak off-axis parts. Conventionally, assist holes are placed in longitudinal and lateral directions around the main holes or 45° to the main pattern. In this paper, we will show that a new kind of assist hole configuration can be applied to this method and that the new configuration has better imaging characteristics in some cases. Since these three configurations can be utilized with the same illumination, a combination of these configurations in the same mask leads to a wider application of this method because conflicting patterns are avoided.
Effect of Extreme Ultraviolet Light Scattering from the Rough Absorber and Buffer Side Wall
Authors: Kwon Yeong-Keun , Sim Sang-Jin , Kim Jong-Hoi , Cha Byung-Cheol , Park Seung-Wook , An Ilsin , Oh Hye-keun
Published: February 2005

The Monte-Carlo method is adopted to define the roughness of the mask structure. A random surface height variation described by power spectral density for the rough surfaces of an extreme ultraviolet (EUV) mask is redefined in order to calculate the field in the image plane. A general explicit formula of the scattering, which is analogous to Feynman's approach, is derived, and it is adapted to the EUV mask structure to evaluate the effect of the surface roughness of the side wall of the mask topography on the image formation. The multiple random scattering problems are dealt with the different pattern types, which are an isolated pattern and a dense pattern, in order to compare field variations in phase and amplitude with the ideal flat surface.
Double-Grating Lateral Shearing Interferometer for Extreme Ultraviolet Lithography
Authors: Liu Zhiqiang , Sugisaki Kasumi , Zhu Yucong , Ishii Mikihiko , Murakami Katsuhiko , Saito Jun , Suzuki Akiyosi , Hasegawa Masanobu
Published: February 2005

A lateral shearing interferometer (LSI) is one of the tools for measuring extreme ultraviolet lithograph project optics (EUVL PO) at-wavelength. In LSI, a grating is set behind the EUVL PO to shear the test wavefront. A point diffraction pinhole is used to correct the aberration of the light source. In LSI, there are some problems limiting measurement accuracy and dynamic range, for example, the fine fringe of the interferogram and the power change of the test beam. In order to solve all of these problems, we propose a new LSI for EUVL PO at-wavelength measurement. In the new LSI, the wavefront of the light source is sheared beforehand against the shearing direction of LSI by another grating set in front of the EUVL PO. After passing through the EUVL PO, the wavefront is sheared again as in a normal LSI. By two times of shearing, the wavefront of the light source is superposed on the imaging sensor, and therefore, the aberration of the light source can be canceled without using a point diffraction pinhole. On the other hand, the test wavefront is sheared on the imaging sensor and is measured as in a normal LSI. Because the point diffraction pinhole is removed from the interferometer, the test beam power becomes strong and stable. By setting the two gratings conjugated by the EUVL PO, a one-color interferogram is realized. We designed a new LSI with double gratings to realize our LSI in the at-wavelength EUVL PO test. The accuracy of the new interferometer is expected to be higher than 0.3 nm (RMS).
Advantageous Exposure of X Architecture Patterns when Using a Variable-Shaped Beam Tool
Authors: Boettcher Monika , Gramss Juergen , Eichhorn Hans , Hahmann Peter , Lemke Melchior , Schnabel Bernd
Published: February 2005

The concept of introducing diagonal interconnects in chip manufacturing offers several advantages and is known as X architecture. We investigated the fabrication of such patterns for high-resolution direct writing applications using variable-shaped electron beam lithography. The variable-shaped beam offers throughput advantages for Manhattan patterns. These advantages apply also to X architecture patterns, provided slanted rectangular and triangular shots can be used for pattern generation. This specific shot generation method has already been incorporated in Leica SB350 electron beam writing tools, so that it has become possible to significantly reduce the number of shots required for exposing X architecture layouts. The resolution is not affected by the pattern orientation. 130 nm pitch lines and spaces with axis-parallel and slanted orientations were successfully exposed in a 250-nm-thick NEB-33 resist.
Calculation of Coulomb Interaction among Electrons in a High-Current Electron-Beam Exposure System
Authors: Kotera Masatoshi , Yukumoto Taisuke
Published: February 2005

In the present study, we propose a new calculation method for the Coulomb interaction among electrons in an electron beam running at a given optical system. In the simulation, the interaction is expressed by separating the global and the stochastic mechanisms, and then, they are combined in a Monte Carlo electron trajectory simulation. In the case of the global Coulomb effect, the potential distribution is obtained in the beam, and the electron trajectory deflection due to the distribution is calculated. In the case of the stochastic Coulomb effect, it is assumed that electrons interact with only their nearest neighbor electrons in the beam. All electron trajectories in the entire optical system are traced three-dimensionally. Since the Coulomb interaction is calculated for only one pair of electrons instead of all pairs of other electrons around the electron in the present model, the computation time is markedly reduced. It is found that the results obtained by the present simulation show a fair agreement with that obtained by considering all existent electrons in the beam, as in the conventional Monte Carlo simulation of the Coulomb interaction.
Design and Fabrication of Diffractive Optical Element-Microlens with Continuous Relief Fabricated On-Top of Optical Fibre by Focused Ion Beam for Fibre-to-Waveguide Coupling
Authors: Schiappelli F. , Kumar R. , Prasciolu M. , Cojoc D. , Cabrini S. , Proietti R. , Degiorgio V. , Fabrizio E. Di
Published: February 2005

The purpose of this work is to demonstrate efficient optical coupling between a single mode fibre and a waveguide (LiNbO3-APE) using a diffractive optical elements (DOEs)-microlens with continuous relief fabricated directly on the top of a cleaved fibre using a focused ion beam (FIB) milling process. DOE's with diameters as small as 15 µm were fabricated by means of FIB milling process. A focused Ga + ion beam was used to mill a continuous relief microstructure at a 30 kV acceleration voltage. The design of the DOE-microlens and the calculations related to the optical fibre-to-waveguide coupling was carried with our own developed code. The profile of the fabricated DOE-microlens was very well reproduced in nine annulus each of 100 nm thick. The focusing performance of DOE-microlens with nine annulus was investigated. This fabricated DOE-microlens was able to focalize the Gaussian beam leaving the fibre, into a wave guide plane at a distance of 28 µm from the DOE-microlens surface. The fundamental mode size of the beam leaving the fibre was of about 10.5 µm while the size of the focused waist was 5.2 µm. This has led to an efficient matching the fundamental mode of the fibre vis-à-vis that of waveguide. Coupling efficiency test were carried using a laser beam λ=1550-nm wavelength. The optical coupling using the DOE-microlens on-top-of the fibre-to-waveguide is 67% more efficient than the direct coupling between the fibre and the waveguide. This shows that the design meets the application's requirement for fibre-waveguide coupling, and that DOE-microlens fabricated by FIB technology are practicable.
Electrical Field Analysis of Nanoscale Field Effect Transistors
Authors: Boudjella Aissa , Jin Zhongfang , Savaria Yvon
Published: February 2005

Numerical simulations have been performed to analyze the electric field inside nanoscale field effect transistors with channel lengths L
ch of 2 and 4 nm. Our electrostatic analyses characterize the electric field distribution inside the device structure when the ratio of dielectric thickness T
ox to L
ch (T
ox/L
ch) ranges from 0.2 to 50. At constant drain voltage, the relationship between the gate voltage V
g and T
ox/L
ch in the field distribution was investigated. Near the interface, the field intensity changes significantly and depends on V
g, T
ox/L
ch and on the distance from the interface. V
g has a strong effect on channel field for a small T
ox/L
ch (0.2–0.66). This effect decreases but remains significant when T
ox/L
ch increases in the range of 0.66–5. On the other hand, for T
ox/L
ch on the order of 5, V
g has a limited impact on the channel field and becomes negligible as T
ox/L
ch increases up to 50. We confirmed Kagen et al.'s suggestion that the values of T
ox and L
ch need to be properly selected to obtain functional nanoscale field effect transistors. However, we found that the gating effect should be included in device models for much higher of T
ox/L
ch values. Moreover, our results approximately corresponded to related work published by Damle et al.
Field Effect Transistor-based Bimolecular Sensor Employing a Pt Reference Electrode for the Detection of Deoxyribonucleic Acid Sequence
Authors: Kim Dong-Sun , Park Hey-Jung , Jung Hwan-Mok , Shin Jang-Kyoo , Choi Pyung , Lee Jong-Hyun , Lim Geunbae
Published: February 2005

We have fabricated field effect transistor (FET)-type biomolecular sensor for the detection of the deoxyribonucleic acid (DNA) sequence based on 0.5 µm standard complementary metal oxide semiconductor (CMOS) technology and investigated its electrical characteristics. A Pt reference electrode with improved performance was employed for the detection of the DNA sequence and Au, which has a chemical affinity with thiol by forming a self-assembled monolayer (SAM), was used as the gate metal in order to immobilize the DNA. It was fabricated as a p-channel metal oxide semiconductor (PMOS) FET-type because PMOSFET with positive surface potential could be very attractive for detecting negatively charged DNA from the view point of high sensitivity and fast response time. The FET-based biomolecular sensor can detect the DNA sequence by measuring the variation of drain current due to a biomolecular charge after DNA probe immobilization and variation of capacitance after DNA hybridization. The gate potential of the sensor was applied by the Pt reference electrode and DNA was detected by both in situ and ex situ measurements. The drain current increased when a single-stranded DNA (ss-DNA) with thiol was immobilized because the effect of DNA charge with thiol is dominant. The drain current decreased when the DNA was hybridized into a double-stranded DNA (ds-DNA) because of the decrease in capacitance due to DNA hybridization. In situ measurement showed good agreement with ex situ measurement.
Increased Emission Efficiency of Gated Cold Cathode with Carbonic Nano-Pillars
Authors: Yoshida Tomoya , Baba Akiyoshi , Asano Tanemasa
Published: February 2005

Carbonic field emitter material produced from organic films such as photoresists and polyimides, is a very attractive candidate for application in large-area field-emission displays (FEDs). In this paper we describe improvements in the fabrication yield and emission efficiency of a gated cold cathode whose emitter is made up of nano-pillars of carbonic material. We have found that the low-density porouslike-structure photoresist film causes structural damage of the device and this leads to an increase in leakage current. The film density can be significantly improved by Ar-ion-beam irradiation, which contributes to the complete fabrication of the device. After the complete fabrication, the electron emission efficiency was markedly improved from 0.1% to 50%. Electric breakdown voltage was also improved. Field electron emission from the 4×4 matrix gated cold cathode is demonstrated.
Scratch Drive Actuator Driven Self-assembled Variable Optical Attenuator
Authors: Lee Chengkuo , Lai Yen-Jyh , Wu Chia-Yu , Lin Yu-Shen , Tasi Ming Hung , Huang Ruey-Shing , Lin Min-Shyong
Published: February 2005

This paper describes the new concept and design for a self-assembled variable optical attenuator (VOA) derived by using surface micromachining technology. A residual stress-induced flexure curved beam with corrugated trench anchors can lift up the reflective mirror shutter. This self-assembled reflective shutter can be driven by a set of scratch drive actuator (SDA), then slides into the spacing between input and output fiber ends. The attenuation range of proposed microelectromechanical systems (MEMS) VOA is determined by the vertical position of self-assembled pop-up polysilicon reflective shutter in which it is controlled by the value of applied dc voltage. This new VOA demonstrates continuous attenuation capability and wide attenuation range based on using an electrostatic actuator that is a new residual stress-induced flexure curved beam with corrugated-trench anchors. This device exhibits attenuation range of 70 dB and insertion loss less than 1 dB.
Multiple Optical Trapping by Means of Diffractive Optical Elements
Authors: Cojoc Dan , Emiliani Valentina , Ferrari Enrico , Malureanu Radu , Cabrini Stefano , Proietti Remo Zaccaria , Fabrizio Enzo Di
Published: February 2005

In this paper we report multiple optical trapping of microscopic dielectric particles using diffractive optical elements implemented on twisted nematic liquid crystal spatial light modulators. The particles are trapped in arrays disposed in plane or in volume and can be moved independently in x-y-z by changing the configuration of the diffractive optical element. We show also multiple trapping using Laguerre-Gaussian and Gaussian beams simultaneously. The orbital angular momentum of the Laguerre-Gaussian beam is transferred to the particle, making it to move on a circular trajectory defined by the intensity pattern specific to this beam. We use sample cells built with two microscope slides separated by 120 µm with a sticky tape. The space between the two slides is filled with 2 µm diameter silica spheres diluted in water (concentration 0.026% wt). We show that optical trapping is also possible in a small glass capillary with a diameter of 100 µm.
Optimum Incident Angle of Ar Cluster Ion Beam for Superhard Carbon Film Deposition
Authors: Kitagawa Teruyuki , Miyauchi Kazuya , Toyoda Noriaki , Tsubakino Harushige , Yamada Isao
Published: February 2005

Diamond-like carbon (DLC) films with super hardness (>50 GPa) were deposited using Ar cluster ion beams at various oblique incident angles irradiated towards substrates on which C60 was simultaneously deposited. When the incident angles of Ar cluster ions were from 0° to 20°, the DLC films had a super hardness of approximately 50 GPa, the hardness three times higher than that of conventional DLC films. Furthermore, the films had a flat surface and a low sp2 content, which was estimated with a near edge X-ray absorption fine structure (NEXAFS). However, in the range of angles above 40°, the carbon films had a lower hardness, a rougher surface, and a higher sp2 content. Therefore, the incident angles of the Ar cluster ions for obtaining super hardness ranged from 0° to 20°.
Fine Pattern Etching of Silicon Substrates Using Atmospheric Line-Shaped Microplasma Source
Authors: Okumura Tomohiro , Saitoh Mitsuo , Matsuda Izuru
Published: February 2005

An atmospheric line-shaped microplasma source was developed for fine pattern etching, and the dependence of the etching properties on the substrate temperature and the distance between the two outer gas outlets was investigated. There was a sudden increase of the etching rate and a decrease of top width when the substrate temperature was 300°C or more. Auger electron spectroscopy (AES) analysis indicates that oxidation on the line shoulder caused the top width to decrease. By decreasing the distance between the two outer gas outlets from 3 mm to 650 µm, the top width decreased from 441 µm to 234 µm. The gas flow simulation result revealed that there exists a firing limit of SF6 partial pressure from 0.1% to 0.2% in the configuration.
A Detection Method for a T-Topped Profile in Resist Patterns by Top-Down-View Critical Dimension Scanning Electron Microscope
Authors: Yamaguchi Atsuko , Fukuda Hiroshi , Komuro Osamu , Yoneda Shozo , Iizumi Takashi
Published: February 2005

A new detection method for a T-topped profile in resist patterns is proposed. This method can determine a T-topped tendency from only a single top-down critical dimension scanning electron microscope (CD-SEM) image. The method is based on the relationship between a cross-sectional pattern profile and a shape of a bright area near the pattern edge in the top-down image. Two kinds of indices for a T-topped tendency are obtained from line-edge roughness, width of the area and a correlation coefficient between the left and right borders of the area. Both indices agreed well with actual cross-sectional profiles of various resist patterns.
High-Resolution Hybrid Lithography with Negative Tone Chemically Amplified Resists
Authors: Landis S. , Pauliac S. , Saint-Pol J. , Gourgon C. , Akita M. , Hanawa R. , Suetsugu M.
Published: February 2005

We present in this paper the development of a hybrid lithographic process using negative tone chemically amplified resists. Starting with the Sumitomo commercial negative-tone chemically amplified resist NEB-33, experimental formulations have been developed to extend resolution below 30 nm in electron beam lithography. Thermal and infrared spectroscopy measurements were carried out to determine the macroscopic properties of samples. Electron beam lithography at 50 kV and 100 kV was performed to determine the ultimate resolution. Although they were first designed for electron beam lithography, deep ultra-violet exposures were carried out to develop a hybrid process. Post exposure bake effects on resist line widths and cross-sectional profiles were examined. As a result of process optimization, 20 nm isolated lines have been resolved using these new resists.
High-Sensitive Ultrathin Negative Electron Beam Resist Based on Langmuir-Blodgett Films of Polycyanoacrylate
Authors: Pisignano Dario , Berzina Tatiana , Erokhin Victor , Fontana Marco P. , Torre Antonio Della , Visconti Paolo , Rinaldi Ross
Published: February 2005

We carried out an electron-beam lithography study of the sub-µm performances of Langmuir-Blodgett films of Polycyanoacrylates fabricated by the Langmuir-Schaefer technique. We tested the sensitivity of films made by 48 monolayers, finding a dose of less than 1 µC/cm2, and employed them as masks for wet etching of Cr metal layers, with resolutions up to 100 nm. These results suggest that the modified Langmuir-Schaefer technique, and the Polycyanoacrylate-based resists, are very promising for nanotechnology applications.
Alignment Offset Analyzer against Wafer-Induced Shift
Authors: Ina Hideki , Matsumoto Takahiro , Sentoku Koichi
Published: February 2005

In lithography, the alignment error can be caused by three factors. The first factor is the tool-induced shift (TIS), the second is the wafer-induced shift (WIS) and the third is the interaction between TIS and WIS. Regarding TIS, we have defined a new evaluation criterion, and regarding WIS, we have shown that the error analyzer can quantify and compensate for the alignment error using an atomic force microscope (AFM) and optical simulation. We have termed this analyzer the `alignment offset analyzer'. By using this analyzer, the topography of the alignment mark and the topography of the resist surface can be measured individually using the AFM. The two topography data are wrapped over in the signal simulator. By using this wrapped topography, the alignment signal and alignment measurement error value are calculated. By considering the topography and alignment measurement error values, the alignment error can be quantified. Furthermore, the alignment offset can also be calculated before the exposure sequence, and the alignment offset can be fed to the exposure tool without using the send-ahead wafer. For this analyzer, we use the AFM Dimension 9000 M (Veeco Inc.) and the simulator that contains TEMPESTpr (Panoramic Technology Inc.), and CODEV (Optical Research Associates). In this paper, we report the accuracy of the alignment offset analyzer. The exposure tool result and the calculated result from AFM data by the simulator showed a good agreement, and the difference was several nanometers.
A Monte Carlo Calculation of Secondary Electron Emission from Organic Compounds
Authors: Yasuda Masaaki , Nobuo Takahiro , Kawata Hiroaki
Published: February 2005

A Monte Carlo simulation of secondary electron emission from organic compounds has been developed. The number of secondary electrons generated in the specimen is determined parametrically and the energy of the secondary electrons is calculated using a simple electron excitation function, which is an approximate formula for the outer shell ionization. The cascade scattering process of the secondary electrons generated is included. The variation of secondary electron yield with the primary electron energy is calculated and the validity of the simulation is checked in comparison with the experimental data reported for several types of materials. A relatively good agreement is obtained between the calculated secondary yields and experimental ones.
Imprint/Photo Hybrid Lithography Using Conventional Contact Aligner
Authors: Kawata Hiroaki , Hirai Yoshihiko , Kikuta Hisao
Published: February 2005

Fine patterns were fabricated by a combination of imprint lithography and photo-lithography using a conventional contact aligner. A resist film was pressed at an atmospheric pressure. Since it was difficult to press the mold mask onto the resist film completely, the residual resist was removed by a photolithography process. An image reversal process is used. It was important that the press was carried out on an unbaked resist. Patterns were exposed to a mercury lamp without a monochromatic filter during the atmospheric pressure press. After the photolithography no residual resist could be found. Good patterns can be obtained up to approximately 0.5 µm. A 0.35 µm line and 0.65 µm space pattern can also be fabricated, but the resist thickness of the fabricated pattern is less than the initial resist thickness.
Fabrication of Low Line Edge Roughness Mold for Photo-Nanoimprint
Authors: Kurashima Yuichi , Hiroshima Hiroshi , Komuro Masanori , Kim Sang Hoon , Yamazaki Naoto , Taniguchi Jun , Miyamoto Iwao , Namatsu Hideo , Matsui Shinji
Published: February 2005

We attempted to fabricate patterns having low line edge roughness (LER) by photo-nanoimprint for evaluation of critical dimension (CD) atomic-force microscopy (AFM). In order to fabricate the transparent low LER mold, we used spin on glass (SOG) imprinted using a low LER Si master mold made by anisotropic wet etching. We investigated SOG imprint properties as a function of pattern size. For patterns less than 0.5 µm wide, we formed the patterns on SOG having the same depth as the corresponding pattern height on the mold. Detailed observation showed that patterns broadened for outermost lines in line-and-space patterns where the Si master mold was not pushed perpendicularly into the SOG layer. We fabricated patterns on SOG molds 180 nm high and 100 nm wide and having a 200 nm period. Photo-nanoimprint was carried out using the SOG mold, and the LER of patterns on a photocurable polymer was 0.74 nm, comparable to that of the Si master mold.
Present Status and Prospect of Si Wafers for Ultra Large Scale Integration
Authors: Tsuya Hideki
Published: February 2005

Si wafers have contributed to the rapid growth of the semiconductor industry as a basic material for ultra large scale integration (ULSI) through the research and development of new technologies and mass production in response to the various demands of device manufacturers. In this paper, first, the key issues of wafer quality improvement with respect to wafer fabrication technology, gettering and grown-in defects are reviewed. Various wafers currently in use such as annealed wafers, epitaxial wafers and 300 mm diameter wafer are discussed with respect to technology and cost effectiveness. Advanced Si-based wafers represented by silicon on insulator (SOI) and strained SiGe wafers are also described. After discussing the challenge to develop innovative Si wafer technologies which will lead to the future development of ULSI, the other important issues associated with Si wafers such as the re-examination of over-stringent specifications, cost reduction, economically reasonable pricing and the promotion of mutual understanding and cooperation between device makers and wafer makers for the continued development of both industries are emphasized.
Liquid Phase Chemical Enhanced Oxidation on AlGaAs and Its Application
Authors: Lee Kuan-Wei , Wang Yeong-Her , Houng Mau-Phon
Published: February 2005

A new method named the liquid phase chemical enhanced oxidation (LPCEO) technique has been proposed for the oxidation of aluminum gallium arsenide (AlGaAs) near room temperature. The initial stage of AlGaAs oxidation by this method has been investigated. The native oxide film composition is determined on the basis of the results of Auger electron spectroscopy (AES), X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy. Based on current–voltage (I–V) characteristics of the metal–oxide–semiconductor (MOS) structure, the leakage current density is approximately 5×10-9 A/cm2 at the electric field of 1 MV/cm, and the breakdown field is at least 10 MV/cm after rapid temperature annealing. In addition, the oxide film properties can be improved after thermal annealing based on capacitance–voltage (C–V) measurements. Finally, the application of the new method to the AlGaAs/InGaAs metal–oxide–semiconductor pseudomorphic high-electronic-mobility transistor (MOS-PHEMT) is demonstrated.
Effect of Hf Sources, Oxidizing Agents, and NH3/Ar Plasma on the Properties of HfAlOx Films Prepared by Atomic Layer Deposition
Authors: Kawahara Takaaki , Torii Kazuyoshi , Mitsuhashi Riichirou , Muto Akiyoshi , Horiuchi Atsushi , Ito Hiroyuki , Kitajima Hiroshi
Published: February 2005

The effect of Hf sources, oxidizing agents, and NH3/Ar plasma on the properties of HfO2 and HfAlO
x
films prepared by atomic layer deposition (ALD) have been investigated. The use of tetrakis(ethylmethylamino)hafnium: Hf(NEtMe)4 (TEMAHf) as a source of hafnium has avoided the problems associated with hafnium tetrachloride (HfCl4), such as poor throughput and the generation of a large number of particles. This source has also been effective in reducing the level of residual chlorine (Cl). However, the level of residual carbon (C) increased. Hydrolysis was found to be more effective than oxidation using O3 in removing ligands from the TEMAHf and/or trimethylaluminum (TMA); the film formed using O3 contained a higher level of C than that using H2O, resulting in the deterioration in field-effect transistor (FET) properties, such as the subthreshold swings and the mobilities. The total levels of residual impurities (C+Cl) were successfully reduced through the combination of TEMAHf and NH3/Ar plasma, leading to improvements in FET properties, particularly in the reduction of the gate leakage current.
Simultaneous Observation of Molecular Contamination Behavior in Semiconductor Clean room Using Quartz Crystal Microbalance
Authors: Okamura Shigeru , Shimada Manabu , Okuyama Kikuo
Published: February 2005

To search the cause and mechanism of the molecular contamination trouble that sometimes occurs in the semiconductor manufacturing, we developed a quartz crystal microbalance (QCM) molecular contamination monitoring system that is able to carry out two-dimensional simultaneous observation with a high sensitivity. As the result of long-term simultaneous observation of different QCM sensor surface materials in an operating semiconductor clean room, it has been understood that QCM can monitor the changes in the molecular contamination environment very sensitively. We observed for the first time the emission phenomenon of molecular contamination that is discharged from equipments synchronizing with the process sequence by observation of the QCM system. Moreover, the phenomena of NOx in a clean room air of less than 100 ppb promoting the adsorption of the molecular contaminants were observed. The multipoint continuous monitoring of the clean room atmosphere by the QCM system was shown to be very effective in the clarification of the cause of molecular contamination trouble.
Fabrication of High-Density Wiring Interposer for 10 GHz 3D Packaging Using a Photosensitive Multiblock Copolymerized Polyimide
Authors: Kikuchi Katsuya , Segawa Shigemasa , Jung Eun-Sil , Nemoto Yoshihiko , Umemoto Mitsuo , Nakagawa Hiroshi , Tokoro Kazuhiko , Aoyagi Masahiro
Published: February 2005

We have developed a high-density wiring interposer for 10 GHz 3D packaging using a photosensitive multiblock copolymerized polyimide. This new polyimide can realize micron-sized fine patterns without pattern shrinkage because of the nonrequirement of high-temperature thermal curing. The polyimide has good electric properties such as high breakdown voltage and low dielectric constant. Therefore, it is considered that by introducing this photosensitive polyimide as an insulator of the interposer, a high-performance interposer for LSI packaging can be realized. We confirmed experimentally that the high-density wiring interposer can be fabricated using the polyimide and gold. We optimized the basic properties of the photosensitive polyimide film for the fabrication of the interposer. Fine metal wirings were smoothly covered by the polyimide, as confirmed by scanning electron microscopy (SEM) of the cross section of the fabricated balance pair strip line structure. From the time domain reflectometry (TDR) measurement, it was determined that the characteristic impedance of the strip line is within 55.2 Ω ± 11.5% at the center of the interposer chip.
GaN Photodetectors with Transparent Indium Tin Oxide Electrodes
Authors: Chiou Yu-Zung , Tang Jing-Jou
Published: February 2005

Sputtering indium tin oxide (ITO) and e-beam ITO films deposited onto GaN as transparent electrodes for applications in metal–semiconductor–metal (MSM) photodetectors were fabricated and reported. The transmittances of 1000 Å-thick sputtering-ITO and e-beam ITO films were 78% and 67%, respectively, at a wavelength of 350 nm. The variation in the transmittance of the sputtering ITO films was not dependent on film thickness. The estimated effective barrier heights of the sputtering ITO and e-beam ITO films to GaN were 0.46 and 0.95 eV, respectively. This difference in barrier height originates from the formation of InGaN at the interface of ITO/GaN. Finally, GaN MSM photodetectors were fabricated using e-beam ITO electrodes. The peak responsivity of these e-beam ITO MSM photodetectors was 0.11 A/W at a 3 V bias. For a given bandwidth of 500 Hz, the corresponding noise equivalent power (NEP) and normalized detectivity D
* were calculated to be 1.51×10-10 W and 2.96×109 cmHz0.5W-1, respectively.
Selective Dry Etching of Zinc Telluride Using Aluminum Mask
Authors: Guo Qixin , Matsumoto Yuichi , Tanaka Tooru , Nishio Mitsuhiro , Ogawa Hiroshi
Published: February 2005

Selective reactive ion etching of zinc telluride using aluminum mask has been investigated. The etching rate for Al mask was determined to be 0.7 nm/min, which is much smaller than that of ZnTe under the same etching condition using CH4 and H2 gases. The mask selectivity of Al was determined to be approximately 88 for ZnTe, indicating that the thin layer of Al film can be a good mask for fabricating ZnTe microelectronic devices.
Universal Wideband Antireflection Coating Designs for Substrates over the Visible Spectral Region by Minimizing Search Method
Authors: Liou Yeuh-Yeong
Published: February 2005

A design method based on the minimizing search algorithm was applied to create universal wideband visible antireflection coating designs for commonly used substrates with refractive indices ranging from 1.45 to 1.784. The minimizing search algorithm consists of a tuning operation of sublayer thickness and an eliminating operation of sublayers, which can refine the mean visible antireflection performance and simplify the design structure of the desired solution. It was shown that the two-material 30-layer minimizing search for universal wideband visible antireflection coating designs of a set of eight different substrates with refractive indices of 1.45, 1.50, 1.55, 1.60, 1.65, 1.70, 1.75 and 1.784 were reduced to 12-layer structures and the average reflectivities for the eight different substrate systems over the visible spectral region were very coincident and were reduced to lie between 0.172–0.173%.
Correlation between O/Er Content Ratio and Photoluminescence Intensity of (Er, O)-Doped Hydrogenated Amorphous Si Thin Films Prepared by a Catalytic Chemical Vapor Deposition/Laser Ablation Hybrid Process
Authors: Sakai Joe , Masuda Atsushi , Akiyama Haruo , Eryu Osamu , Nakashima Kenshiro , Matsumura Hideki
Published: February 2005

(Er, O)-doped hydrogenated amorphous Si (a-Si:H) thin films were prepared on Si or SiO2 substrates by a novel catalytic chemical vapor deposition (Cat-CVD)/laser ablation hybrid process which simultaneously performs a Cat-CVD of a-Si:H matrices and a doping of laser-ablated (Er, O) from an Er2O3 sintered target. These (Er, O)-doped a-Si:H films showed excellent photoluminescence (PL) properties in spite of the low temperature of the process (200°C during deposition and no postannealing). The Er and O contents of these films were evaluated by Rutherford backscattering and non-Rutherford elastic resonance scattering (NRERS), respectively. It was clarified that the dependence of the (Er, O) content on ambient pressure was not identical for O and Er. Thus, the O/Er content ratio, correlated to the PL intensity, strongly depended on the ambient pressure.