bluuebunny/crossref_metadata_2025 huggingface dataset:
What We Learned and Used in the First Inductively Coupled Plasma for Plasma Processing and in Later Development
Authors: Keller John H.
Published: August 2011

The first inductively coupled plasmas (ICPs) for plasma processing, also called radio frequency induction (RFI), were developed at IBM, East Fishkill, NY, U.S.A. These were extremely efficient at producing high density plasma. This paper will discuss: 1) How to drive the antenna to get high plasma density with low plasma voltage and low capacitively coupled plasma (CCP) losses, 2) low matching losses, 3) the optimum way (presets) to start an ICP, 4) frequency effects, and 5) achieving high plasma stability.
Wave-Cutoff Method: Theory, Apparatus, Characteristics, and Applications
Authors: Na Byung-Keun , You Kwang-Ho , Chang Hong-Young
Published: August 2011

In this paper, we present an overview of recent studies of the wave-cutoff method, so that researchers who are not familiar with it can use this method easily. This method uses a wave-cutoff probe to acquire plasma parameters from the transmission or reflection spectra of plasma. Since this method was developed, some applications and analysis methods have been attempted and much progress has been achieved. The wave-cutoff method can measure electron density and electron temperature simultaneously, and is usable even in processing plasma. This method can measure the plasma parameters very accurately in a very short time.
Time-Resolved Quantum Cascade Laser Absorption Spectroscopy of Pulsed Plasma Assisted Chemical Vapor Deposition Processes Containing BCl3
Authors: Lang Norbert , Hempel Frank , Strämke Siegfried , Röpcke Jürgen
Published: August 2011

In situmeasurements are reported giving insight into the plasma chemical conversion of the precursor BCl3in industrial applications of boriding plasmas. For the online monitoring of its ground state concentration, quantum cascade laser absorption spectroscopy (QCLAS) in the mid-infrared spectral range was applied in a plasma assisted chemical vapor deposition (PACVD) reactor. A compact quantum cascade laser measurement and control system (Q-MACS) was developed to allow a flexible and completely dust-sealed optical coupling to the reactor chamber of an industrial plasma surface modification system. The process under the study was a pulsed DC plasma with periodically injected BCl3at 200 Pa. A synchronization of the Q-MACS with the process control unit enabled an insight into individual process cycles with a sensitivity of 10-6cm-1·Hz-1/2. Different fragmentation rates of the precursor were found during an individual process cycle. The detected BCl3concentrations were in the order of 1014molecules·cm-3. The reported results ofin situmonitoring with QCLAS demonstrate the potential for effective optimization procedures in industrial PACVD processes.
Spatial Profile Measurement of SiH3 Radical Flux in SiH4/H2 Microwave Plasma by Modified Appearance Mass Spectrometry
Authors: Kuroda Toshiyuki , Ikeda Masahira , Ishijima Tatsuo , Toyoda Hirotaka
Published: August 2011

Appearance mass spectrometry (AMS) is one of the well-known detection techniques for neutral radicals. In this technique, however, radical flux is sometimes underestimated owing to radical loss on the inner surface of the differentially pumped mass spectrometer chamber. To avoid this problem, we propose a modified AMS that enables the evaluation of radical loss. The decay time of neutral radicals inside the mass spectrometer is measured using a compact piezochopper that is installed in front of the mass spectrometer orifice. This technique is applied to the evaluation of SiH3 radical flux in SiH4/H2 microwave plasma.
Optical Diagnostics of Breakdown Phase of Pulsed N2/He Atmospheric-Pressure Microhollow Cathode Discharge Plasma
Authors: Wake Shinya , Nakano Toshiki , Kitajima Takeshi
Published: August 2011

The breakdown phase of a pulsed N2/He atmospheric-pressure microhollow cathode discharge plasma is studied using the time-resolved N2 optical emission spectra as well as the discharge current and voltage. The N2 emission intensity exhibits a sharp peak in the breakdown phase and becomes constant in the glow discharge phase. The temporal variation of the N2 emission spectra indicates that the N2 rotational temperature remains below 500 K immediately after discharge ignition but increases to ≈1000 K within ≈20 µs after the ignition. In the breakdown phase, the plasma with high excitation and dissociation rates is probably generated at the low neutral temperature. The prompt increase in neutral temperature indicated by the N2 rotational temperature is explained using a simple, zero-dimension model including the neutral heating due to electron–neutral collisions and the neutral cooling caused by the removal and refilling of the gas in the discharge volume.
Chemical Activity of Oxygen Atoms in Magnetron Sputter-Deposited ZnO Films during Film Growth
Authors: Morita Aya , Watanabe Ikuo , Ohta Naoki , Shirai Hajime
Published: August 2011

The role of oxygen atoms in the growth of magnetron sputter-deposited ZnO films was studied by alternating the deposition of a several-nanometer-thick ZnO layer and an O2/Ar mixed plasma exposure, i.e., alayer-by-layer(LbL) technique. Film crystallization was promoted by suppressing the formation of oxygen vacancies and interstitial defects by adjusting the exposure conditions of the O2/Ar plasma. These findings suggest that the chemical potential of oxygen atoms influences film crystallization and the electronic state. The diffusion and effusion of oxygen atoms at the growing surface have effects similar to those of thermal annealing, namely, the promotion of film crystallization and the creation and annihilation of oxygen- and zinc-related defects. The role of oxygen atoms reaching the growing film surface is discussed in terms ofchemical annealing, and a possible oxygen diffusion mechanism is proposed.
Characterization of Deposited Films and the Electron Beam Generated in the Pulsed Plasma Deposition Gun
Authors: Yarmolich Dmitry , Nozar Petr , Gleizer Svetlana , Krasik Yakov E. , Mittica Giuseppe , Ancora Cosimo , Brillante Aldo , Bilotti Ivano , Taliani Carlo
Published: August 2011

The channel spark discharge was used as a high-current density (up to 30 kA/cm2) relatively low-energy (<20 keV) electron beam source in a pulsed plasma deposition (PPD) gun. The PPD gun was used for the deposition of thin films by pulsed ablation of different target materials, at a background gas pressure in the 10-3–10-5Torr range. The parameters of the electron beam generated in the modified PPD gun were studied using electrical, optical, and X-ray diagnostics. It was found that a higher background pressure stimulates a denser plasma formation between the gun output and the target, that restricts the energy delivery to the beam electrons. Namely, the efficient (up to ∼74%) transfer of the initially stored energy to the electron beam is realized at the background gas pressure of 10-4Torr. Conversely, at a pressure of 10-3Torr, only ≤10% of the stored energy is acquired by the energetic electrons. It was shown that the modified PPD gun, owing to the extremely high energy density delivered by the electrons to the target, may be applied for the deposition of a wide variety of different insulators, semiconductors, and metals. A selection of materials such as diamond-like carbon (DLC), cadmium telluride (CdTe), cadmium sulphide (CdS), zinc oxide (ZnO), tungsten, and tungsten carbide (WC) have been deposited as thin films and the properties and deposition rates of the deposited thin films are discussed.
Near-Edge X-ray Absorption Fine-Structure Spectroscopic Study on Nitrogen-Doped Ultrananocrystalline Diamond/Hydrogenated Amorphous Carbon Composite Films Prepared by Pulsed Laser Deposition
Authors: Al-Riyami Sausan , Ohmagari Shinya , Yoshitake Tsuyoshi
Published: August 2011

Nitrogen-doped ultrananocrystalline diamond (UNCD)/hydrogenated amorphous carbon (a-C:H) composite films, which possessed n-type conduction with enhanced electrical conductivity, were prepared by pulsed laser deposition. The film doped with a nitrogen content of 7.9 at. % possessed enhanced electrical conductivity of 18 Ω-1·cm-1 at 300 K. The near-edge X-ray absorption fine-structure (NEXAFS) measurement indicated the appearance of additional peaks due to π* C=N, σ* C=N, and σ* C–N bonds compared with the spectra of undoped films. The sp2 bonding fraction estimated from the NEXAFS spectra increased with the nitrogen content. The enhanced electrical conductivity is probably due to the formation of additional π* and σ* states and the enhancement in the sp2 bonding fraction.
Fabrication of Transparent Protective Diamond-Like Carbon Films on Polymer
Authors: Baek Sang-min , Shirafuji Tatsuru , Saito Nagahiro , Takai Osamu
Published: August 2011

Si doped hydrogenated amorphous carbon (Si-DLC) films as a candidate protection coating for polycarbonate (PC) were prepared using a pulse-biased inductively coupled plasma chemical vapor deposition (ICP-CVD) system with a gas mixture of acetylene (C2H2) and tetramethylsilane [Si(CH3)4]. The effects of Si incorporation on the structure and optical properties of the Si-DLC films were investigated. In addition, plasma pretreatments with O2, N2, and Ar gases were carried out to enhance the adhesion strength of Si-DLC films on polycarbonate. Structural characterization through Raman and X-ray photoelectron spectroscopy (XPS) analyses showed that the incorporation of Si atoms in DLC films leads to an increase in the optical band gap (E
opt) with the formation of sp3 C–Si bonds. O2 plasma pretreatment improved the strength of adhesion of the Si-DLC films to polycarbonate, while Ar and N2 plasma treatments did not. This can be explained by the formation of an activated dense interfacial layer by O2 plasma pretreatment.
Effect of Oxygen Gas Pressure on Electrical, Optical, and Structural Properties of Al-Doped ZnO Thin Films Fabricated by Pulsed Laser Deposition for Use as Transparent Electrodes in All-Solid-State Electrochromic Devices
Authors: Ohshima Tamiko , Murakami Yuuki , Kawasaki Hiroharu , Suda Yoshiaki , Yagyu Yoshihito
Published: August 2011

Low-resistivity and high-transmittance Al-doped ZnO (AZO) thin films were obtained by pulsed laser deposition with the substrate at room temperature. The electrical, optical, and structural properties of the AZO thin films deposited at various oxygen gas pressures (P
O2) were investigated. X-ray diffraction shows that the AZO thin films have (002) preferred orientation and the diffraction angle of the (002) plane shifts to a higher value with increasing oxygen gas pressure. All AZO thin films deposited under ambient oxygen gas pressure conditions have an optical transmittance of over 80% in the visible region. AZO thin films deposited at lower P
O2 of ≤1 Pa have resistivities of <10-3 Ω cm that increase with increasing P
O2 > 1 Pa. The AZO film deposited at P
O2 = 1 Pa had the lowest resistivity (5.8 ×10-4 Ω cm) with a high carrier concentration of 1.1 ×1021 cm-3.
Behavior of Dust Particles in Plasma Etching Apparatus
Authors: Kobayashi Hiroyuki
Published: August 2011

The behavior of dust particles in a plasma etching apparatus was investigated with an in-situ particle monitor. The properties of the particles are classified into three types according to the particle velocity. Slow-velocity particles (less than 1 m/s) are trapped by a plasma-sheath boundary and rarely fall on the wafer during plasma discharge. These particles should be removed from the region above the wafer before turning off the plasma. Increasing gas flow rate and changing plasma density distribution are effective to control the particle transport. Medium-velocity particles (a few meters per second) travel above the wafer surface due to a balance between ion drag and electrostatic forces during plasma discharge. The number of particles that attach to the wafer can be reduced by supplying wafer bias power for the purpose of increasing the electrostatic force. Fast-velocity particles (a few dozen meters per second or more) are generated by the reflection of particles in a turbo molecular pump (TMP), and these may damage fine patterns on the wafer by colliding with it. The fine pattern damage can be reduced by increasing the distance between the wafer and the TMP. The number of particles fall on the wafer is decreased by supplying down-flow gas. It is therefore important to decelerate fast-velocity particles by using gas viscous force.
Model for Effects of RF Bias Frequency and Waveform on Si Damaged-Layer Formation during Plasma Etching
Authors: Eriguchi Koji , Takao Yoshinori , Ono Kouichi
Published: August 2011

We investigated damaged-layer formation on the Si substrate surface induced by high-energy ion bombardment during plasma processing, by focusing on ion energy distribution function (IEDF). We introduced a modified range theory for the projection of incident ions and applied the model to damaged-layer formation under various plasma conditions – various rf bias frequencies and waveforms, furthermore their single- or dual-frequency bias configurations. Damaged-layer thickness and residual defect site density after the wet-etch process following the plasma treatment were simulated. The IEDF having more high-energy ions induces the formation of thicker damaged layer than in the case of a monochromatic ion energy when the average ion energies are the same. However, we found that, owing to the stochastic effect on the ion-projected range, the effects of bias frequency and the waveform were suppressed, i.e., the thickness of the damaged layer and the density of residual defect sites are weakly dependent on IEDFs under the same average incident ion energy. The present findings obtained by the model prediction are significant and useful for designing bias configurations for future plasma processes.
Impacts of CF+, CF2
+, CF3
+, and Ar Ion Beam Bombardment with Energies of 100 and 400 eV on Surface Modification of Photoresist
Authors: Takeuchi Takuya , Amasaki Shinpei , Kondo Hiroki , Ishikawa Kenji , Toyoda Hirotaka , Sekine Makoto , Kang Song-Yun , Sawada Ikuo , Hori Masaru
Published: August 2011

Photoresists used in advanced ArF-excimer laser lithography are not tolerant enough for plasma etching processes. Degradation of photoresists during etching processes might cause not only low selectivity, but also line edge roughness (LER) on the sidewalls of etched patterns. For a highly accurate processing, it is necessary to understand the mechanisms of etching photoresists and to construct a new plasma chemistry that realizes a nano scale precise pattern definition. In this study, the modified layers formed on the surface of a photoresist by the bombardment of fluorocarbon ions of CF+, CF2
+, and CF3
+, and argon (Ar) ions were analyzed by X-ray photoelectron spectroscopy (XPS). The etching yield of the modified steady-state surface was almost dependent on the mass of incident ion species. The surface composition was modified with increasing dosage of each ion species, and reached a specific steady state that was dependent on the ion species. The bombardment of F-rich ion species such as CF2
+ and CF3
+ resulted in the formation of not only fluorocarbon layers, but also graphite like structures on the surface. On the basis of these results, the surface reaction for the ion-beam-induced modification was discussed.
Three-Dimensional Atomic-Scale Cellular Model and Feature Profile Evolution during Si Etching in Chlorine-Based Plasmas: Analysis of Profile Anomalies and Surface Roughness
Authors: Tsuda Hirotaka , Miyata Hiroki , Takao Yoshinori , Eriguchi Koji , Ono Kouichi
Published: August 2011

Three-dimensional measurement and prediction of atomic-scale surface roughness on etched features become increasingly important for the fabrication of next-generation devices; however, the feature profiles are too small or too complex to measure the surface roughness on bottom surfaces and sidewalls of the etched features. To predict the surface roughness on an atomic or nanometer scale, we developed our own three-dimensional atomic-scale cellular model (ASCeM-3D) and feature profile simulation, with emphasis being placed on the formation of surface roughness on the atomic scale soon after the start of Si etching in Cl2 plasmas. Numerical results indicated that nanometer-scale convex roughened features appear on the surface soon after the start of etching, which causes the formation of a larger surface roughness, and that the surface roughness tends to be saturated after several seconds. In effect, the nanoscale convex features increase in size with increasing etching or plasma exposure time, and new nanoscale convex ones continue to appear on top of the enlarged convex ones during etching, thus resulting in concavo-convex features superimposed on the roughened surface. A comparison was also made between numerical results and experiments.
Patterning of 25 nm Contact Holes at 90 nm Pitch: Combination of Line/Space Double Exposure Immersion Lithography and Plasma-Assisted Shrink Technology
Authors: Marneffe Jean-François de , Lazzarino Frédéric , Goossens Danny , Vandervorst Alain , Richard Olivier , Shamiryan Denis , Xu Kaidong , Truffert Vincent , Boullart Werner
Published: August 2011

In this work, two methods are combined in order to provide 25 nm contact holes at 90 nm pitch: the line/space double exposure immersion lithography and the plasma-assisted shrink technology. We first present the line/space imaging method with negative tone development to create directly 45 nm CH at 90 nm pitch. Then, we discuss plasma-assisted shrink technology and how it applies to these small contacts. Plasma-assisted shrink technology relies on running a fast cyclic process, where plasma polymers are deposited on the photoresist mask, then subsequently redistributed over the features sidewalls, allowing in final a diameter reduction of approximatively 50%. Finally, for the metal-hard-mask patterning approach, the dielectric etch challenges driven by the dimensional scaling are analysed and discussed.
Biomedical Applications of Low Temperature Atmospheric Pressure Plasmas to Cancerous Cell Treatment and Tooth Bleaching
Authors: Lee Jae Koo , Kim Myoung Soo , Byun June Ho , Kim Kyong Tai , Kim Gyoo Cheon , Park Gan Young
Published: August 2011

Low temperature atmospheric pressure plasmas have attracted great interests and they have been widely applied to biomedical applications to interact with living tissues, cells, and bacteria due to their non-thermal property. This paper reviews the biomedical applications of low temperature atmospheric pressure plasmas to cancerous cell treatment and tooth bleaching. Gold nanoparticles conjugated with cancer-specific antibodies have been introduced to cancerous cells to enhance selective killing of cells, and the mechanism of cell apoptosis induced by plasma has been investigated. Tooth exposed to helium plasma jet with hydrogen peroxide has become brighter and the productions of hydroxyl radicals from hydrogen peroxide have been enhanced by plasma exposure.
Hemocompatible Poly(ethylene terephthalate) Polymer Modified via Reactive Plasma Treatment
Authors: Cvelbar Uroš , Junkar Ita , Modic Martina
Published: August 2011

In this paper we present the fabrication of micro- and nanostructure poly(ethylene terephthalate) (PET) polymer surfaces used for as synthetic vascular grafts and their hemocompatible response to plasma-treated surfaces. The surface modification of PET polymer was performed using radio frequency (RF) weakly ionized and highly dissociated oxygen or nitrogen plasma. The surface of the PET polymer was modified to enable the improved proliferation of endothelial cells. In addition to biological experiments performedin vitroby assessing the number of attached cells by tetrazolium compound (MTS)-based cell proliferation assay, we also analyzed the chemical modification of plasma-treated surfaces by X-ray photoelectron spectroscopy (XPS), while the changes in morphology and surface roughness were observed by scanning electron microscopy (SEM) and atomic force microscopy (AFM), respectively. Our results indicate that surface treatment with both oxygen and nitrogen plasma improved the proliferation of endothelial cells, which increased with treatment time by 15 to 30%. This phenomenon was explained by the creation of new functional groups and the modification of surface morphology, which promotes the adhesion of endothelial cells.
Immobilization of L-Cysteine onto Poly(ethylene glycol) Polymerized by Surface-Wave Plasma
Authors: Shao Zhenyi , Ogino Akihisa , Nagatsu Masaaki
Published: August 2011

Poly(ethylene glycol) (PEG) terminated with hydroxyl functional groups is expected to play the roles of a hydrophilic layer to alleviate the aging effect and an intermediate for the subsequent covalent immobilization of L-cysteine. A plasma-induced grafting-polymerization or crosslinking technique using microwave-excited surface-wave plasma for grafting PEG molecules on a polyurethane (PU) surface is presented. The effects of Ar plasma pretreatment and post-treatment on the in situ polymerization or crosslinking of PEG molecules are investigated. The effect of Ar plasma pretreatment on the surface shows that pretreatment can induce the adsorption of more PEG molecules on the surface for the subsequent post-treatment. Increasing the post-treatment power and post-treatment time can achieve the in situ polymerization or crosslinking of PEG molecules, whereas excessively increasing the post-treatment power and post-treatment time can induce excessive damage to the hydroxyl functional groups.
Effects of N2–O2Gas Mixture Ratio on Microorganism Inactivation in Low-Pressure Surface Wave Plasma
Authors: Zhao Ying , Ogino Akihisa , Nagatsu Masaaki
Published: August 2011

In this study, the effect of N2/O2gas mixture ratio on low-pressure surface wave plasma inactivation of spore-forming bacteria was investigated. It was experimentally confirmed from the quadrupole mass spectrometry measurements that the spores were etched by atomic oxygen via converting the hydrogen atoms constituting microorganisms into H2O and the carbon into CO2. On the basis of results of plasma diagnostics by optical emission spectroscopy and the results of inactivation efficiency by colony-forming units and scanning electron microscope, we found that although there is the highest ultraviolet (UV) emission intensity in pure N2plasma and the highest etching efficiency in 90% O2/10% N2plasma, the inactivation rate of microorganisms was not so efficient. The best inactivation result was obtained in 30–80% O2gas mixture ratios after 60 s plasma irradiation. The present results indicated that more efficient inactivation is achieved by the synergetic effects between atomic oxygen etching and the vacuum ultraviolet (VUV)/UV emission by combining both effects via optimizing N2/O2gas mixture ratio.
Optimization of Amino Group Introduction onto Polyurethane Surface Using Ammonia and Argon Surface-Wave Plasma
Authors: Ogino Akihisa , Noguchi Suguru , Nagatsu Masaaki
Published: August 2011

Effects of hydrogen and NH
x
species produced by a surface-wave excited Ar/NH3 plasma on amino group introduction onto a polyurethane surface were studied by comparing the results of optical emission spectroscopy (OES) and primary amino group concentration. For increasing the introduced primary amino group concentration on the surface, the monitoring and control of the concentration of NH
x
species as a precursor and that of atomic hydrogen as an etchant are important. From the results of X-ray photoelectron spectroscopy (XPS) and OES analysis, the primary amino group concentration and the emission intensity of Hβ reached a minimum and a maximum, respectively, at around 25% NH3 gas mixture ratio. An excess of atomic hydrogen over nitrogen grafting species might reduce the amino group selectivity and N/C surface density. To increase the concentration of NH
x
species produced in a plasma, the enhancement of NH
x
generation by the Penning effect was examined by adding Ar gas. As a result, the primary amino group concentration increased with the increase in the emission intensity of NH. However, the amino group selectivity became lower than that in the case of pure NH3 plasma treatment since not only the primary amino group concentration but also the secondary and tertiary amino group concentrations increased with the enhanced decomposition of NH3 by Ar metastables.
Effects of Nitrogen and Oxygen Radicals on Low-Temperature Bio-Molecule Processing
Authors: Motrescu Iuliana , Ogino Akihisa , Tanaka Shigeyasu , Fujiwara Taketomo , Kodani Shinya , Kawagishi Hirokazu , Popa Gheorghe , Nagatsu Masaaki
Published: August 2011

The mechanism by which microwave plasma is able to modify the structure and function of proteinaceous molecules is investigated. The biomolecule cystine, a dimer aminoacid, was exposed to microwave surface wave plasma produced in reactive gases, such as oxygen and nitrogen, in different conditions. Except for the physical interactions of the charged particles with the samples and the photophysical reactions induced mostly by ultraviolet radiation, these plasmas contain reactive species which promote chemical interactions. In this study we focus on the changes of biomolecules due to neutral particles inside reactive plasmas. The results proved that the effects of neutrals and charged species are not cumulative. Moreover, it seems that the charged species inside the nitrogen plasma promote nitrogen addition while the outcome of neutral exposure is cleavage. Strong oxidation occurs for oxygen treatments, most reactive species which cause oxygen addition being the oxygen molecular ions O2
+.
Effect of Filament Discharge on Uprightness of Carbon Nanotwists Tightly-Adhered to Substrate
Authors: Sugioka Yuki , Yokota Masashi , Pude Tang , Suda Yoshiyuki , Takikawa Hirofumi , Tanoue Hideto , Ue Hitoshi , Umeda Yoshito , Shimizu Kazuki
Published: August 2011

Making carbon nanofibers stand up in a field electron emitter to obtain a good field emission property when emitters are fabricated by printing on a substrate has been proposed. In the fabrication process of carbon nanotwist (CNTw) field emitters, paste composed of an ethyl cellulose binder and carbon nanotwists (CNTws) is printed on the substrate. Filament discharge (FD) treatment is an excellent technique that makes CNTws stand up because large-area treatment is possible at a low cost. To solve the problems of weak adhesion between CNTws and the substrate and the generation of fragments during FD treatment, we added a silicone binder to the paste at 0.83–0.97%. The variations in the silicone binder content were compared by the scanning electron microscopy (SEM) observation of CNTw emitter surfaces. As the content decreased, the number of upright CNTws increased and the height of upright CNTws became uniform. We confirmed that the crystalline property of CNTws was not changed by the FD treatment when the silicone binder was added. Also, spark from the CNTw emitter was inhibited with the addition of the silicone binder and the field emission current density in the case with the binder was 200 µA/cm2 higher than that in the case without the binder.
Synthesis of Carbon-Nanotube Fine Particles in a Glow-Discharge Plasma and Evaluation of Hydrogen Storage Properties
Authors: Hayashi Yasuaki , Imano Masayoshi , Kinoshita Yumi , Kimura Yoshifumi , Masaki Yasuhiro
Published: August 2011

Carbon fine particles including single-walled carbon nanotubes (SWNTs) were successfully synthesized in the gas phase by hot filament thermal chemical vapor deposition with radio-frequency (RF) plasma. The process of formation of fine particles was monitored from the variation of RF self-bias voltage. Synthesized carbon fine particles showed a higher hydrogen storage capacity than commercialized SWNTs (CoMoCAT) under the storage conditions of atmospheric pressure and room temperature.
Iron-Based Nanopowders Containing α-Fe, Fe3C, and γ-Fe Particles Synthesised in Microwave Torch Plasma and Investigated with Mössbauer Spectroscopy
Authors: David Bohumil , Pizúrová Naděžda , Schneeweiss Oldřich , Kudrle Vít , Jašek Ondřej , Synek Petr
Published: August 2011

Two Fe-based nanopowders were synthesised using microwave torch discharge at 1 bar. The main channel of the discharge was operating in Ar, which flowed through the central nozzle of an electrode, whereas the reactive mixture H2/Fe(CO)5was added through a concentric outer nozzle. Besides rarely observed γ-Fe particles (for the first sample:dXRD= 30 nm, 35 wt %; for the second sample:dXRD= 9 nm, 33 wt %) samples also included α-Fe, Fe3C, and Fe3O4/γ-Fe2O3particles. The presence of γ-Fe phase was proved by the interpretation of the XRD patterns and the Mössbauer spectra taken at 293 and 5 K.
Mechanisms of Decomposition of Organic Compounds by Water Plasmas at Atmospheric Pressure
Authors: Nishioka Narengerile , Watanabe Takayuki
Published: August 2011

The decomposition of acetone, methanol, and ethanol by water plasmas at atmospheric pressure has been investigated using a direct current (DC) discharge. At torch powers of 910–1050 W and organic compound concentrations of 1–10 mol %, the decomposition rate of methanol was over 99.99%, while those of acetone and/or ethanol was 96–99%. The concentrations of H2 obtained were 65–71% in the effluent gas and the removal efficiencies of 90–95% for total organic carbon (TOC) were achieved in liquid effluent for any compounds by pyrolysis. Over 50 wt % carbon in acetone or ethanol fed as the plasma supporting gas was transformed into soot, while the soot formation was negligible during methanol decomposition. On the basis of the experimental results, the mechanisms of decomposition of organic compounds in water plasmas were proposed and the mechanism of soot formation was clarified for the first time.
Process Performances of 2 ns Pulsed Discharge Plasma
Authors: Matsumoto Takao , Wang Douyan , Namihira Takao , Akiyama Hidenori
Published: August 2011

Pulsed discharge plasmas have been used to treat exhaust gases. Since pulse duration and the rise time of applied voltage to the discharge electrode has a strong influence on the energy efficiency of pollutant removal, the development of a short-pulse generator is of paramount importance for practical applications. In this work, it is demonstrated that the non thermal plasma produced by the 2 ns pulsed discharge has a higher energy efficiency than the 5 ns pulsed discharge plasma for NO removal and ozone generation. Typically, the NO removal efficiency was 1.0 mol kW-1 h-1 for 70% NO removal (initial NO concentration = 200 ppm, gas flow = 10 L/min). Meanwhile, the ozone yield was 500 g kW-1 h-1 for 20 g/m3 ozone concentration in the case of oxygen feeding. These energy efficiencies are the highest in the literature.
Depth Profile Characterization of Spin-Coated Poly(3,4-ethylenedioxythiophene):Poly(styrene sulfonic acid) Films for Thin-Film Solar Cells during Argon Plasma Etching by Spectroscopic Ellipsometry
Authors: Ino Tomohisa , Hayashi Tatsuya , Ueno Keiji , Shirai Hajime
Published: August 2011

Depth profiles of the optical constants, carrier mobility, and carrier density of spin-coated poly(3,4-ethylenedioxythiophene):poly(styrene sulfonic acid) (PEDOT:PSS) films were investigated by real-time characterization by spectroscopic ellipsometry (SE) during argon plasma etching at atmospheric pressure. Spectral analysis revealed that homogeneous etching occurred within 10–15 nm of the top surface, followed by the appearance of a conductive PEDOT phase and surface roughening, which originated from the depth profile of the PEDOT-to-PSS molar concentration ratio. The use of the plasma-etched PEDOT:PSS layer relatively improved the performance of the cupper phthalocyanine (CuPc)/C60organic thin-films solar cells as a hole-transport layer with higher optical transmittance by adjusting the plasma etching condition.
Molecular Dynamics of Ion Incident Angle Dependence of Sputtering Yield in Chlorine-Adsorbed GaN Crystal
Authors: Harafuji Kenji , Kawamura Katsuyuki
Published: August 2011

A molecular dynamics simulation has been carried out to investigate the dependence of chemical sputtering yield on the ion incident angle in the wurtzite-type GaN(0001) surface with a Cl-adsorbed layer. The sputtering yields of both Ga and N atoms show only a weak dependence on ion incident angle for the range of 60 to 90° (normal incidence). Ga is chemically sputtered mostly in the form of Ga–Cl2, and sometimes in the form of Ga–Cl, Ga–Cl3, Ga
x
N
y
, and Ga
x
N
y
Cl
z
. These products escape from the surface in the time range of mainly 200–500 fs after the impact of the incident Ar ion. There are small amounts of products escaping in the time range of 500–5000 fs.
Cutting Tools Nitriding in Plasma Produced by a Fast Neutral Molecule Beam
Authors: Metel Alexander , Grigoriev Sergei , Melnik Yury , Panin Vitaly , Prudnikov Vladimir
Published: August 2011

Nitrogen plasma produced by a broad beam of fast neutral nitrogen molecules in 0.12-m3 vacuum chamber has been studied and used for cutting tools nitriding. The study results prove that fast molecules play a leading role in gas ionization and plasma density is proportional to their energy, equivalent current and gas pressure. Plasma is quite nonuniform: its density is maximal within the beam and rapidly decreases beyond it. Non-self-sustained glow discharge between chamber and an anode immersed in the plasma reduces plasma nonuniformity down to 10%, when discharge voltage amounts to 200–300 V, and raises plasma density by an order of magnitude. After 1-h-long soaking in discharge plasma of isolated from the chamber and heated by 4-keV beam up to 500 °C cutting plates made of high-speed steel their microhardness rises from 950 up to 1400 HV, and the mean radius of cutting edges decreases from 20 to 18 µm.
Damage-Free Dry Polishing of 4H-SiC Combined with Atmospheric-Pressure Water Vapor Plasma Oxidation
Authors: Deng Hui , Takiguchi Tatsuya , Ueda Masaki , Hattori Azusa N. , Zettsu Nobuyuki , Yamamura Kazuya
Published: August 2011

A dry polishing technique combined with the atmospheric-pressure water vapor plasma oxidation has been proposed for the high-integrity smoothing of SiC materials. Optical emission spectra revealed the composition of the plasma, and strong emission from OH, which has a high oxidation-reduction potential (ORP), was observed. X-ray photoelectron spectroscopy (XPS) measurements indicated that the irradiation of water vapor plasma efficiently oxidized the surface of SiC because of the reactive species in plasma such as OH radicals. Swell-like structures were also observed along scratches on the SiC surface. Plasma-assisted polishing using CeO2 abrasive enabled us to reduce the surface roughness of SiC without introducing crystallographical subsurface damage, and an atomically flat scratch-free surface with an rms roughness of less than 0.1 nm was obtained.
Novel Precursors for SiCH Low-k Caps beyond the 22 nm Node: Reactions of Silacyclopentane Precursors in the Plasma-Enhanced Chemical Vapor Deposition Process and Structural Analyses of SiCH Films
Authors: Shimizu Hideharu , Tajima Nobuo , Kada Takeshi , Nagano Shuji , Shimogaki Yukihiro
Published: August 2011

To form SiCH films with high carbon content using plasma-enhanced chemical vapor deposition (PECVD), 1,1-divinylsilacyclopentane (DVScP) and 5-silaspiro[4,4]nonane (SSN) were designed as novel precursors for the low-k cap layer and Cu diffusion barrier at the top of Cu lines. We elucidated the relationship between the structure of low-k SiCH films made from these newly developed precursors and their barrier properties against copper and oxygen diffusion. We also studied the relationship between the structure of SiCH and the deposition process under various RF plasma powers. A Monte Carlo simulation was employed to estimate the deposition profile using an overhang test structure. Fourier transform infrared (FT-IR) spectroscopy was used to analyze the molecular structures. Our novel silacyclopentanes formed SiCH films with high carbon content and good barrier properties at high RF powers due to the specific reactions of silacyclopentanes designed according to our quantum chemical calculations. Precursor design is thus an important factor in forming SiCH with high carbon content that achieves both lower k and good barrier properties.
Surface Modification of Polypropylene Membrane by RF Methane/Oxygen Mixture Plasma Treatment
Authors: Tsai Ching-Yuan , Juang Ruey-Shin , Huang Chun
Published: August 2011

The hydrophilic surface modification of micro-porous polypropylene (PP) membranes is achieved by low-pressure 13.56 MHz RF methane (CH4)/oxygen (O2) gas mixture plasma treatment. The changes in surface wettability and surface free energy were examined by static contact angle analysis. The static water contact angle of the plasma modified membrane notably decreased with increases in treatment time and plasma power. The obvious increase in the surface energy of polypropylene membranes due to CH4/O2 mixture gas plasma treatments was also observed. Optical emission spectroscopy (OES) was used to analyze the chemical species of CH4/O2 mixture gas plasma treatment. The variations in the surface morphology and chemical structure of the micro-porous PP membranes were confirmed by confocal laser scanning microscopy (CLSM), Fourier transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS) measurements. XPS analysis showed significantly higher surface concentrations of oxygen functional groups for CH4/O2 mixture gas plasma-modified polypropylene membrane surfaces than for the originally unmodified polypropylene membrane surface. The experimental results show the important role of chemical species in the interaction between a CH4/O2 mixture gas plasma and a membrane surface, which can be controlled by surface modification to tailor the hydrophilicity of the membrane to the requirements of various applications.
Surface Treatment of Polymer Film by Atmospheric Pulsed Microplasma: Study on Gas Humidity Effect for Improving the Hydrophilic Property
Authors: Shimizu Kazuo , Umeda Akira , Blajan Marius
Published: August 2011

Surface treatment of a poly(ethylene naphthalate) (PEN) film by atmospheric pulsed microplasma with humid Ar gas was experimentally investigated. A Marx generator with metal–oxide–semiconductor field-effect transistor (MOSFET) switches that generates negative pulses was used for generating microplasma. Hydrophilization was estimated by measuring contact angle before and after the microplasma surface treatment by a remote process. The initial contact angle was about 76°. The minimum contact angle of about 20° was obtained after a treatment, a discharge voltage of -1.3 kV negative pulse, a frequency of 24 kHz, a gas relative humidity of about 60%. Analysis by X-ray photoelectron spectroscopy (XPS) showed a decrease in the C 1s peak corresponding to the C–H bond or C–C bond, and increases in the O 1s peaks corresponding to the C=O bond or O–H bond.
Improving Single-Chamber Solid Oxide Fuel Cell Performance by Plasma Treatment Using an Atmospheric-Pressure Helium Plasma Jet
Authors: Kanazawa Seiji , Iwao Tadasuke , Akamine Shuichi , Ichiki Ryuta
Published: August 2011

An atmospheric-pressure helium plasma jet was used for the surface treatment of the electrodes in single-chamber solid oxide fuel cells (SC-SOFCs). The jet-type plasma source used in this study is suitable for the continuous and fine-area processing of materials, such as patterned electrodes. The basic plasma property was investigated by optical emission spectroscopy. Improvement in the performance of SC-SOFC was observed for the plasma-treated cell. From the scanning electron microscopy (SEM) observation, it was found that the surface morphology of the cell was largely changed. The increase in the area of the three-phase boundary among the electrode, electrolyte, and gas phase promoted electrochemical reactions. Under single-chamber operation condition at 850 °C, an open circuit voltage of 650 mV and a maximum power density of approximately 75 mW/cm2were achieved for a coplanar-type cell.
Measurement of Negative Ions Generated on the Si Etched Surface
Authors: Hayashi Toshio , Murai Sonomi , Sato Fumihiko , Kono Akihiro , Mizutani Naoki , Suu Koukou
Published: August 2011

Negative ions emerging from etched Si surface were measured in CF4+O2 mixed capacitive coupled plasmas (CCP) in order to observe the surface reaction in real time. Carbon containing negative ions were observed in the low O2 concentration mixed plasma, and C2F4
- ion was observed in the high O2 concentration mixed plasma. C2F3
- and C2F4
- ions abruptly increased at around the O2 mixing ratio of 15%.
Molecular Dynamics Analysis of the Formation of Surface Roughness during Si Etching in Chlorine-Based Plasmas
Authors: Tsuda Hirotaka , Takao Yoshinori , Eriguchi Koji , Ono Kouichi
Published: August 2011

Addition of oxygen to Cl2 discharge is widely used in Si etching for the fabrication of gate electrodes and shallow trench isolation. As the control of etching processes becomes more critical, a deeper understanding of plasma-surface interactions is required for the formation of roughened surfaces during etching. In particular, a small amount of O2 often leads to profile anomalies such as residues, micropillars, and roughened surfaces. In this study, we focus on the mechanism underlying local surface oxidation during Si etching in Cl2/O2 plasmas, and analyze the relationship between local surface oxidation and surface roughness on the nanometer scale, by a classical molecular dynamics (MD) simulation. The numerical results indicated that O radicals tend to break Si–Si bonds and distort the Si lattice structure; thus, nanometer-scale micromasks tend to be formed on convex roughened surfaces, owing to the reactivity of O radicals with substrate Si atoms and Cl atoms. The results also imply that the nanometer-scale micromasks significantly affect the formation of roughened surfaces and evolution of micropillars.
Etch Properties of TiN Thin Film in Metal–Insulator–Metal Capacitor Using Inductively Coupled Plasma
Authors: Park Jung-Soo , Woo Jong-Chang , Kim Chang-Il
Published: August 2011

In this work, we investigated the etching characteristics of the titanium nitride (TiN) thin film in BCl3/Cl2 plasma and the effect of the gases (O2 and Ar) added to BCl3/Cl2 plasma. The etch rate was measured under various etching conditions, such as the gas mixing ratio, the process pressure and the substrate temperature. The maximum etch rate of TiN thin film was 343 nm/min in BCl3 (25%)/Cl2 (75%) plasma. To enhance the etching characteristics, we added O2 and Ar gas to BCl3 (25%)/Cl2 (75%) plasma. Added O2 and Ar gas flow rates were 2, 5, 8, and 10 sccm. The etch rates with O2 addition decrease from 221 to 4 nm/min. The etch rate in Ar/BCl3/Cl2 plasma decreased slightly compared with that in the case of O2 addition. The nonvolatile etched byproduct was formed on the surface, and was analyzed by X-ray photoelectron spectroscopy (XPS) analysis. O2 addition without Ar ion bombardment in BCl3/Cl2 plasma leaded to increased morphological surface roughening. The etch rate decreased with increasing O2 content owing to the O2 reaction with Ti and TiO2 layer formation on the surface. A nonvolatile etched byproduct was observed by XPS analysis. It could be estimated to be a Ti–Cl compound.
Etch Characterization of TiO2 Thin Films Using Metal–Insulator–Metal Capacitor in Adaptively Coupled Plasma
Authors: Woo Jong-Chang , Joo Young-Hee , Kim Chang-Il
Published: August 2011

In this work, we investigated the etching characteristics of TiO2, and SiO2 thin films and the selectivity of TiO2 to SiO2 in a CF4/Ar adaptively coupled plasma (ACP) system. The maximum etch rates of TiO2, and for SiO2 thin films were 99 and 255.6 nm/min at a gas mixing ratio of CF4 (75%)/Ar (25%). At the same time, the etch rate was measured as a function of the etching parameters, such as the ACP source power, bias power and process pressure. The X-ray photoelectron spectroscopy analysis showed the efficient destruction of the oxide bonds by the ion bombardment, as well as the accumulation of low volatile reaction products on the etched surface. Based on these data, the ion-assisted chemical reaction was proposed as the main etch mechanism for the CF4-containing plasmas.
25 nm Wide Silicon Trench Fabrication by Edge Lithography
Authors: Sakamoto Junji , Kawata Hiroaki , Yasuda Masaaki , Hirai Yoshihiko
Published: August 2011

Very narrow SiO2line patterns are obtained by a new edge lithography technique and narrow silicon trenches are fabricated using the SiO2line patterns. A line pattern with a width below 20 nm is successfully fabricated. Its line height is 180 nm and the aspect ratio exceeds 9. The line is rippled because of the high aspect ratio. A circular line of 40 nm width and 400 nm height is obtained without a ripple. The narrow SiO2patterns are transferred to a Cr pattern by a lift-off process. Silicon is etched by an improved switching process using a Cr pattern mask. The etching rate decreases as the opening width decreases below 500 nm. Very narrow trenches of 25 nm width are fabricated. The side wall profile is vertical when the trench depth is 325 nm. Its aspect ratio is 13. However, bowing is observed in the side wall profile for a trench depth of 1000 nm.
Damage Characteristics of TiO2 Thin Film Surfaces Etched by Capacitively Coupled Radio Frequency Helium Plasmas
Authors: Kawakami Retsuo , Takeichi Atsushi , Niibe Masahito , Inaoka Takeshi , Tominaga Kikuo
Published: August 2011

Damage characteristics of TiO2 thin film surfaces etched by capacitively coupled RF He plasmas are found to be dependent on gas pressure and etch time. At a low gas pressure (10 mTorr), the morphology of TiO2 surface etched for 5 min is smooth like the as-grown surface. When the etch time lengthens to 60 min, the surface morphology is smoother. However, the atomic O concentration at the surface is lower than that of the as-grown surface. On the other hand, at a high gas pressure (50–100 mTorr), the He plasma etch causes a rough surface morphology (surface defects) when the etch time lengthens to 60 min.
Si Recess of Polycrystalline Silicon Gate Etching: Damage Enhanced by Ion Assisted Oxygen Diffusion
Authors: Ito Tomoko , Karahashi Kazuhiro , Fukasawa Masanaga , Tatsumi Tetsuya , Hamaguchi Satoshi
Published: August 2011

The cause of Si recess (i.e., formation of shallow hollows on a Si surface after removal of an oxide layer from the Si surface in a polycrystalline silicon gate etching process by a HBr plasma) has been identified as ion assisted oxygen diffusion, i.e., oxygen diffusion enhanced by hydrogen ion bombardment from the plasma. Both plasma and multi-beam experiments were employed for the analysis of this oxidation mechanism. It has been also found in the analysis that oxidation of a Si surface exposed to oxygen radicals is significantly enhanced only if the surface is subject to both oxygen radical supply and energetic hydrogen ion bombardment simultaneously.
Advanced Contactless Analysis of Plasma-Induced Damage on Si by Temperature-Controlled Photoreflectance Spectroscopy
Authors: Matsuda Asahiko , Nakakubo Yoshinori , Takao Yoshinori , Eriguchi Koji , Ono Kouichi
Published: August 2011

We propose an advanced photoreflectance (PR) spectroscopy technique, for use as a method for the contactless analysis of plasma-induced damage (physical damage) on Si. Si wafers damaged by Ar plasma were placed on a measurement stage capable of sample cooling by liquid nitrogen. In comparison to the spectra at 300 K, the signal intensity at 90 K was increased by cooling. A spectral peak of a heavily-damaged sample was identified at 90 K, which was difficult at 300 K. Changes in the surface potential induced by plasma exposure (ΔVs) were calculated by analyzing the spectral parameters. Areal densities of trapped charges were estimated from ΔVs. The temperature dependence of the PR spectra was discussed, and the primary cause of the increase in signal intensity was attributed to the reduced electron–phonon interactions in a lower temperature range. The proposed technique expands the applicable range of PR-based damage analysis.