bluuebunny/crossref_metadata_2025 huggingface dataset:
In-situ Studies of High-κ Dielectrics for Graphene-Based Device
Authors: Pirkle Adam R. , Chabal Yves J. , Colombo Luigi , Wallace Robert M.
Published: May 2009

The deposition and subsequent oxidation of metallic Al and Hf on graphite has been studied as a route to the formation of a high-κ dielectric on graphene. We employ in-situ x-ray photoelectron spectroscopy (XPS), ex-situ atomic force microscopy (AFM) and Raman spectroscopy to study reactions with the substrate and dielectric film morphology. We show that Al2O3 can be formed on the freshly cleaved graphene surface by annealing the deposited metallic Al in ozone or oxygen. HfO2 is also formed in this manner, but we demonstrate that in the case of Hf, defects are created on the graphene surface unless physisorbed H2O is removed by vacuum annealing prior to deposition and the deposition performed under ultra high vacuum (UHV) conditions.
Graphene Aerogels
Authors: Wang Jian , Ellsworth Mark
Published: May 2009

We have demonstrated for the first time the creation of graphene oxide and graphene-based carbon aerogels by freeze-drying of graphite oxide/water dispersion. The graphene oxide aerogel consists of sheet-like nanocarbon structures, and could be significantly reinforced by small amounts of water soluble polymers. Controlled thermal treatments reduce graphene oxide to graphene and restore the electrical conductivity of the graphene aerogel. The graphene aerogels are electrically conducting, with extremely high surface-area-to-volume ratio, could outperform conventional carbon aerogels for applications such as sensors, actuators, high performance polymer nanocomposites, and electrochemical applications such as porous electrodes for batteries, fuel cells, and supercapacitors.
Graphene as a Permeable Ionic Barrier
Authors: Sreevatsa Sreeya , Banerjee Amrita , Haim Grebel
Published: May 2009

Previously, we have considered electronic p-n junction as a protector of steel from corroding. Here we add graphene between the electronic barrier and metal and study its effect on the corrosion process. We compare our results to metal-graphene-polypyrrole structures. While graphene occupies only a few monolayers of carbon it has a noticeable effect on the surface potential of the metal.
Recent Progress in Dilute Nitride-antimonide Materials for Photonic and Electronic Applications
Authors: Yoon Soon F. , Tan Kian Hua , Loke Wan Khai , Wicaksono Satrio , Lew Kim Luong , Ng Tien Khee , Xu Zhe , Sim Y.K. , Söhr A. , Fedderwitz S. , Weiß M. , Ecin O. , Poloczek A. , Malcoci A. , Jäger Dieter , Saadsaoud N. , Dogheche E. , Zegaoui M. , Lampin J.F. , Decoster D. , Tripon-Canseliet Charlotte , Faci S. , Chazelas J. , Gupta J. A. , McAlister S.P.
Published: May 2009

This paper reviews the recent progress in GaNAsSb material for photonic and electronic applications. All the results and data presented in this review article are summarized from our previously published works in refs. 6-12. Photoresponsivity of 12A/W and cut-off frequency of 4.5GHz were achieved in the 1.3μm GaNAsSb based photodetector. A GaNAsSb/GaAs optical waveguide system was also demonstrated at 1.55μm. The GaNAsSb based photoconductive switch exhibits pulsed response with FWHM of 30ps and photoresponse of up to 1.6μm. The turn-on voltage of the device fabricated from GaNAsSb based HBT is ~330mV lower than that of a conventional AlGaAs/GaAs HBT.
Detection of Cl- Ions with AlGaN/GaN High Electron Mobility Transistors
Authors: Hung S.C. , Chu Byung Hwan , Lo C.F. , Hicks B. , Wang Y.L. , Chang C.Y. , Pearton Stephen J. , Johnson J. W. , Rajagopa P. , Roberts J.C. , Piner E.L. , Linthicum K.J. , Chi G.C. , Ren F
Published: May 2009

AlGaN/GaN high electron mobility transistors (HEMTs) with Ag/AgCl gate are found to exhibit significant changes in channel conductance upon exposing the gate region to various concentrations of chorine ion solutions. Ag/AgCl gate electrode, prepared by potentiostatic anodization, changes the electrical potential when encounters chorine ions. This gate potential changes lead to a change of surface charge in the gate region on the HEMT, induced a higher positive charge on the AlGaN surface, and finally increases the pizeo-induced charge density in the HEMT channel. These anions create an image positive charge on the Ag gate metal for the required neutrality, thus increase the drain current of the HEMT. The HEMT source-drain current showed a clear dependence on the chorine concentration. The limit of detection (LOD) achieved was 1×10-8 M using a 20µm × 50µm gate sensing area.
GaN HEMT Reliability Through the Decade
Authors: Smith Kurt V. , Brierley Steve , McAnulty Robert , Tilas Cary , Zarkh Dimitry , Benedek Michael , Phalon Philip , Hooven Anna
Published: May 2009

The reliability of GaN-based transistors has improved over the last decade into a system insertion ready technology. Material quality and uniformity has played a strong role in this evolution. Identifying and understanding the physical evolution of the degradation mechanisms provides a basis for evaluating device lifetimes. Recent life testing has demonstrated sufficient lifetime for most applications.
Towards Sustainable Photovoltaic Solar Energy Conversion: Studies Of New Absorber Materials
Authors: Dale P. J. , Peter Laurence M. , Loken Andreas , Scragg Jonathan
Published: May 2009

The implementation of terawatt photovoltaic solar energy conversion will place new demands on materials supply and environmental impact. As a consequence, the search for sustainable photovoltaic materials that combine low cost with low toxicity and low energy manufacturing processes is becoming increasingly important. This paper examines the preparation and properties of two merging indium-free photovoltaic absorber materials, Cu2ZnSnS4 and Cu3BiS3. Electrochemical routes to fabrication of absorber layers are considered, and characterization methods based on photoelectrochemistry and electrolyte contacts are discussed.
Optimization of PbSe Nanofilms formation by Electrochemical Atomic Layer Deposition (ALD)
Authors: Banga Dhego , Kim You-Geun , Cox Stephen , Happek Uwe , Stickney J. L.
Published: May 2009

Optimization studies of lead selenide (PbSe) nanofilm formation using electrochemical Atomic Layer Deposition (ALD) are reported here. IV-VI compounds semiconductors, such as the lead chalcogenides (PbSe, PbTe and PbS), have narrow band gaps and crystallize in the cubic rock salt structure. They are of interest for their optical and electronic properties, which make them useful in thermoelectric device structures, infrared sensors, and photovoltaics. PbSe has the narrowest band gap of the lead chalcogenides, 0.26 eV at room temperature. PbSe deposits were formed using an ALD cycle on Au substrates, one atomic layer at a time, from separate solutions, containing Pb or Se ions. Single atomic layers were formed using surface limited reactions, referred to as underpotential deposition (UPD).
Dynamics of Macropore Growth in n-type Silicon Investigated by FFT In-Situ Analysis
Authors: Carstensen Jürgen , Cojocaru Ala , Leisner Malte , Föll Helmut
Published: May 2009

The dynamics of macropore growth in n-type silicon were investigated by in-situ FFT impedance spectroscopy and transient analysis. In particular the response to fast growing pores to current density steps in the context of so-called anti-phase diameter oscillations was investigated. These pore growth mode allows for a very fast growth of deep macropores and could for the first time be stimulated by external current steps.
Electrochemical Passivation of (100) Silicon in Alkyl Grignard Solutions
Authors: Vegunta Sri Sai Sivakumar , Ngunjiri Johnpeter , Flake John C.
Published: May 2009

Surface modification of (100) silicon with methyl groups is analyzed using electrografting and thermal hydrosilation. The surface chemistry is investigated by Fourier transform infrared (FTIR), X-ray photoelectron spectroscopy (XPS), voltammetry and atomic force microscopy (AFM). Surfaces anodically electrografted in methyl Grignard solutions show a smooth topology and improved passivation relative to passivation via hydrosilation. Functionalized surfaces are stable and hinder the formation of oxides up to 45 days after the electrografting as shown in the XPS results.
Electronic Properties and pH Stability of Si(111)/Alkyl Monolayers
Authors: Aureau Damien , Moraillon Anne , Henry de Villeneuve Catherine , Ozanam Francois , Allongue Philippe , Chazalviel Jean-Noël , Rappich Jörg
Published: May 2009

The electronic properties of hydrogenated and alkyl-grafted silicon surfaces have been investigated by photoluminescence, surface photovoltage and electrochemical capacitance measurements, which are sensitive methods for monitoring the presence of electronic defects. On p-type silicon, the electronic quality of the interface was found to depend critically on the surface preparation and was studied with special care. The thermal grafting of one monolayer of linear organic chains on atomically flat silicon allows the formation of stable alkyl-grafted p-Si surfaces, exhibiting a very low density of recombination centers comparable to those measured on hydrogenated silicon surfaces. Photoluminescence measurements show that the high electronic quality of the grafted surfaces is preserved on a month scale in air, indicating a much more efficient long term passivation by comparison with hydrogenated Si surfaces. The stability of the silicon/organic layer interface in aqueous buffer solution has been assessed by in situ photoluminescence and surface photovoltage measurements. Some degradation of the electronic properties was evidenced during exposure in basic solution of pH > 9.
Micro-Patterning of Semiconductors by Metal-Assisted Chemical Etching through Self-Assembled Colloidal Spheres
Authors: Ono Sachiko , Arai Fusao , Asoh Hidetaka
Published: May 2009

Macroporous semiconductors such as Si and GaAs with ordered pore intervals were fabricated by the site-selective chemical etching of a substrate using patterned Pd-Pt thin film catalyst through self-assembled colloidal spheres as a mask. The obtained macroporous silicon using noble metal catalyst was conical because the pore wall of macropores was chemically dissolved presumably due to the diffusion of positive holes injected at the metal catalyst. In contrast, relatively straight pores with uniform diameter were grown when the concentration of HF was high. With increasing concentration of HF, the etching rate at the pore bottoms in a vertical direction to the Si surface increased, while the etching rate in a lateral direction was suppressed markedly to yield high aspect ratio of pores up to 10. The change in features of macroporous silicon was thought to be involved in the difference in diffusion behavior of injected positive holes at the silicon/metal interface.
Novel Plasmaless Photoresist Removal Method in Gas Phase at Room Temperature
Authors: Miura Toshinori , Kekura Mitsuru , Horibe Hideo , Yamamoto Masashi , Umemoto Hironobu
Published: May 2009

Novel plasmaless photoresist removal method in gas phase at room temperature has been developed using pure ozone gas which has nearly 100% of concentration. This method has enabled the removal of high dose ion implanted photoresist that had been difficult to remove so far. Conventionally, the temperature rise of 200{degree sign}C or more was necessary in the photoresist removal with the ozone gas to achieve an enough effect. Because the strong reactiveness is due to the oxygen radical generated when the ozone molecules decomposed. However, Popping by the temperature rise becomes a problem in the removal of high dose ion implanted photoresist. Then, in this experiment, ethylene gas was used to control the decomposition of ozone molecule at the room temperature. As a result, it was confirmed that the ashing using ethylene gas and ozone gas was effective to remove the high dose ion implanted photoresist under unheating condition.
Impact of Deuterium and Fluorine Incorporation on Weibull Distribution of Dielectric Breakdown in Gate Dielectrics
Authors: Mitani Yuichiro , Satake Hideki , Toriumi Akira
Published: May 2009

TDDB (Time-Dependent Dielectric Breakdown) is still serious in the context of efforts to realize highly reliable ULSI. In particular, the statistical distribution of TDDB is essentially important from the viewpoint of determining the lifetime of the devices. In this work, we focus on the effect of deuterium (D) and fluorine (F) incorporation into gate oxides on TDDB statistics. These elements can terminate (passivate) dangling bonds of silicon or oxygen in SiO2 and its interface. As a result, stress-induced leakage current (SILC) is suppressed by deuterium incorporation, and consequently, Weibull distribution of Tbd shifts to long lifetime maintaining Weibull slope. Furthermore, Weibull slope monotonously increases with increasing fluorine dosage. On the basis of experimental results, the suppression of probability of Si-H bond breakage and the structural relaxation of SiO2 network invoke the improvement of Weibull distribution of Tbd.
Dielectric Breakdown Characteristics of Stacked High-k Dielectrics
Authors: Lee Byoung Hun , Choi Rino
Published: May 2009

Dielectric breakdown characteristics of high-k dielectric have been intensively studied to develop a lifetime extrapolation model for device with metal/high-k gate stacks. Majority of prior works treated the high-k dielectric as a single layer dielectric like thermally grown SiO2 while the actual structure of high-k dielectric consists of two layers (high-k layer stacked on interfacial SiO2 like interfacial layer). And, the results of reliability test were interpreted using the model developed for SiO2. In the previous works, the potential limit of such approach has been pointed out; 1) severe electric field distortion due to transient charging in high-k dielectric during the stress, 2) excessive electrical stress applied to the interfacial layer. Thus, it was suggested that the extrapolation method using high field stress may not be correct for high-k dielectric. In this paper, several breakdown models suggested for high-k dielectric will be reviewed and compared to provide a comprehensive understanding on the current knowledge and challenges in this area.
Moisture Effects on the 1/F Noise Of Mos Devices
Authors: Fleetwood Daniel M. , Francis Sarah A. , Dasgupta Aritra , Zhou Xing , Schrimpf Ronald , Shaneyfelt Marty R. , Schwank James R.
Published: May 2009

We have exposed MOS gate and field oxide transistors to moisture treatments with all pins grounded for up to three weeks. Irradiated field oxide structures showed a significant decrease in low frequency noise with moisture treatment, due to the passivation of Si dangling bonds at or near the Si/SiO2 interface. With moisture exposure, pMOS gate oxide transistors showed significant increases in pre-irradiation 1/f noise and post-irradiation oxide- and interface-trap charge densities. The 1/f noise of nMOS gate oxide transistors shows much less sensitivity to moisture exposure than pMOS transistors, before and after irradiation. We attribute these differences in sensitivities to moisture treatment to the enhancement of water diffusion in SiO2 by B atoms in the oxides that overlie the source/drain junctions of the pMOS transistors, in contrast to the retardation of moisture diffusion by P atoms in the corresponding regions of the nMOS devices.
Suppression of Leakage Current of Deposited SiO2 with Bandgap Increasing by High Temperature Annealing
Authors: Sometani Mitsuru , Hasunuma Ryu , Ogino Masaaki , Kuribayashi Hitoshi , Sugahara Yoshiyuki , Yamabe Kikuo
Published: May 2009

In this work, we suppressed the leakage current of chemical-vapor-deposited SiO2 films using tetraethylorthosilicate (TEOS-SiO2) by high temperature annealing. As a result of annealing, leakage currents of TEOS-SiO2 were suppressed to the level of thermally grown SiO2. Meanwhile, the relationship of electrical and structural characteristics of TEOS-SiO2 has been investigated to reveal the mechanism of the improvement of the dielectric properties with thermal annealing. Stress relaxation of the TEOS-SiO2 caused by thermal annealing was observed as blue shift of the infrared absorption spectral peak with a Fourier-transform infrared attenuated total reflection (FT-IR-ATR). It was concluded that the stress relaxation increased the bandgap of TEOS-SiO2, resulting in suppression of the leakage current. The roughness of the TEOS-SiO2 surface was also investigated by atomic force microscopy (AFM). Additionally, thermal desorption spectroscopy (TDS) was performed to understand the phenomena during film densification by thermal annealing.
Low-temperature-atomic-layer-deposition of SiO2 with Tris(dimethylamino)Silane (TDMAS) and Ozone using Temperature Controlled Water Vapor Treatment
Authors: Hirose Fumihiko , Kinoshita Yuta , Shibuya Suguru , Narita Yuzuru , Miya Hironobu , Hirahara Kazuhiro , Kimura Yasuo , Niwano Michio
Published: May 2009

SiO2 ALD with precursors of tris(dimethylamino)silane (TDMAS) and ozone on Si(100) surfaces at room temperature were investigated by infrared absorption spectroscopy with a multiple internal reflection geometry. TDMAS dissociatively adsorbs on OH sites of hydroxylated Si surfaces and ozone irradiation is effective to remove the hydroaminocarbon adsorbates introduced in the course of the TDMAS adsorption. After the ozone treatment, H2O vapor treatments at substrate temperatures around 160 åC allow generation of OH sites for the TDMAS adsorption. The TDMAS adsorption and the ozone treatment at room temperature followed by the H2O treatment at 160 åC enable the cyclic deposition of SiO2. V-I measurements of SiO2 grown by the present 160 åC ALD indicated the deposited film has breakdown electric fields from 3 to 11 MV/cm. C-V measurements indicated that the present ALD is available for MOS capacitors.
Atomic Layer Deposition of Rare-earth Oxide Thin Films for High-k Dielectric Applications
Authors: Stafford Nathan A. , Katamreddy Rajesh , Guerin Laurie , Feist Ben , Dussarrat Christian , Pallem Venkateswara , Weiland Conan , Opila Robert
Published: May 2009

Many different organolanthanide molecules are being proposed as metal sources for depositing metal and metal oxide layers for semiconductors by atomic layer deposition (ALD). These precursors need particular physical and thermal properties to be used in the semiconductor manufacturing process. ALD deposition methods are very promising; however, new high-κ metal oxide films will require new precursors to meet the very stringent requirements of the semiconductor process. Tris(cyclopentadienyl) rare earth compounds are interesting for use as precursors because of their high vapor pressures, often low melting points and availability in the liquid state, high reactivity towards water, and high growth rates for deposition. In this study, we examine the various important thermal properties of Cp-based lanthanide precursors along with their ALD properties for metal oxide deposition.
The Flash Memory Cell for the Nodes to Come: Material Requirements from a Device Perspective
Authors: Govoreanu Bogdan , Kittl Jorge A. , De Vos Joeri , Rothschild Aude , Blomme Pieter , Wellekens Dirk , Ruiz Aguado Daniel , Jurczak Malgorzata , Van Houdt Jan
Published: May 2009

The quest for mass storage and the diversity of end-user applications led to an aggressive scaling of the NAND Flash memory. A key factor to its success is the high density integration potential, which allows fabrication of large memory arrays. Reduction of the feature size below 40 nm may, however, require modifications of the conventional floating gate cell architecture, due to lack of physical space between neighboring cells, which no longer allows wrapping of the control gate over the floating gate. This has consequences on both intra- as well as inter-cell levels, calling for the introduction of high-k dielectrics in Flash memory. In this paper, we take a top-down stance and translate device characteristics into material requirements and/or points of attention that need to be addressed in order to ensure a successful continued scaling of the Flash memory for the upcoming technology generations.
Improved Growth Behaviors and Electrical Properties of SrTiO3 Thin Films Using the Optimized Seed Layer Deposited by Atomic Layer Deposition
Authors: Lee Sang Woon , Han Jeong Hwan , Hwang Cheol Seong
Published: May 2009

SrTiO3 (STO) thin films were deposited by an atomic layer deposition at a higher temperature (370 oC) in order to improve the crystallinity and density of the film using Ti(O-iPr)2(thd)2 and Sr(thd)2 as Ti-, and Sr-precursors, respectively, and H2O as the oxidant. With the help of the crystallized seed-layer, in-situ crystallized STO film could be deposited even at the as-deposited state with the excellent electrical performances. The process conditions including the annealing temperature and the thickness of the seed-layer were crucial for achieving the high dielectric constant. From a planar capacitor structure consisting of Pt/20-nm-thick STO/Ru(bottom) Tox of 0.72 nm (dielectric constant of 108) and a low leakage current density (~ 10-7 A/cm2 at 0.8 V) were achieved. The Schottky conduction mechanism mainly contributed to the electrical conduction process in the low electric field region (< ~ 0.3 MV/cm) with a Schottky barrier height of 0.47 eV between Ru and STO. The Fowler-Nordheim tunneling was appeared as the primary conduction mechanism in the high electric field region (0.3~0.5 MV/cm).
The Improvement Effect of the Plasma Nitridation Process to the Reliability of HfO2 Thin Films
Authors: Chang Kow-Ming , Chen Bwo-Ning , Tang Chun-Kai
Published: May 2009

There have been some researches which describe that the thermal stability and the dielectric constant of the high-k dielectrics could be improved by the nitridation process. In this study, we examined the effect of different ICP plasma nitridation process to the reliability of HfO2 thin films. The capacitance-voltage and current-voltage characteristics of nitrided samples were observed to decide the most suitable process time. The hysteresis, stress induced leakage current (SILC) and constant voltage stress (CVS) characteristics of the nitrided samples were preformed to verify the improvement effect of the plasma nitridation. According to this study, the ICP plasma nitridation process would be an effective technology to improve the reliability of pure HfO2 thin films.
The Effect of Periodic Relaxation on the Growth Behavior and Electrical Properties of Atomic Layer Deposited PbTiO3 Thin Film
Authors: Park Min Hyuk , Lee Hyun Ju , Kim Gun Hwan , Hwang Cheol Seong
Published: May 2009

Atomic layer deposition (ALD) is a promising technique for growing thin films on complicated 3-dimensional structures owing to its ability to achieve a uniform composition and conformal thickness. However, the growth rate and composition along the thickness direction are not necessarily uniform due to several reasons.. In this study, enhanced controllability of the composition of atomic layer deposited PbTiO3 film was achieved by dividing the overall deposition cycle into several groups with periodic relaxation. The structural and electrical properties of the films deposited were investigated. The effects of a post-deposition treatment, different electrode materials and the 2-step growth on the structural and electrical properties of the PbTiO3 film were investigated.
The Effects of Oxidants on the Growth Behavior of PbTiO3 Thin Film by Atomic Layer Deposition
Authors: Lee Hyun Ju , Park Min Hyuk , Hwang Cheol Seong
Published: May 2009

PbTiO3 thin films were deposited on Si and Ru substrates by atomic layer deposition (ALD) at a substrate temperature of 200oC using H2O and O3 as oxidants. When H2O was used as the oxidant for both Pb- and Ti-precursors, film growth was most effective under the PbO vs. TiO2 growth cycle ratio where stoichiometry (Pb/Ti concentration ratio = 1) of the film could be achieved. The previously reported catalytic effect observed in the PbTiO3 ALD process was attributed to the enhanced growth of the component oxide layer, i.e. PbO and TiO2, by previously formed stoichiometric PbTiO3 phase. On the other hand, when H2O and O3 were used for Pb- and Ti-precursors, respectively, the growth rate increased with increasing PbO vs. TiO2 growth cycle ratio. This was attributed to the effects of O3 used for the Ti-precursor on the adsorption of Pb-precursor during the subsequent PbO growth step.
On the Characteristics of Zinc Oxide Films Grown on (11-20) Sapphire Substrates by Atomic Layer Deposition Using Diethylzinc and Nitrous Oxide
Authors: Yen Kuo-Yi , Liu Kuang-Pi , Lin Yen-Ting , Gong Jyh-Rong , Tsai Kuen-Yau , Lyu Dong-Yuan , Lin Tai-Yuan , Liang Shih-Chang , Ni Guo-Yu , Jih Far-Wen
Published: May 2009

Zinc oxide (ZnO) films were grown on (11-20) sapphire substrates at 600oC by atomic layer deposition (ALD) using diethylzinc (DEZn) and nitrous oxide (N2O). For a typical growth run, a ZnO buffer layer was deposited at low temperature (LT) prior to the growth of a bulk ZnO film. In some cases, buffer-layer annealing or post-annealing treatments were employed to optimize ZnO growth. Based on the experimental results of x-ray diffractometry (XRD) and transmission electron microscopy (TEM), all the as-grown ZnO films were found to show c-axis preferred orientation with co-existence of <1-100>ZnO ‖<1-100>sapphire and <11-20>ZnO‖<1-100>sapphire relationships in the (0001)ZnO/(11-20)sapphire hetero-interface. Typical room temperature (RT) photoluminescence (PL) spectrum of the as-grown ZnO film shows only near band edge (NBE) emissions without defect luminescence. ZnO films with improved quality were achieved by post-annealing or buffer-layer annealing treatments. In particular, buffer-layer annealing was found to remarkably improve the crystalline and optical properties of a ZnO film.
CMP For Direct Wafer Bonding of Hermetically Sealed Cavity Structures
Authors: Rhoades Robert L. , Danzl Ralph
Published: May 2009

Direct wafer bonding (DWB) is being increasingly utilized for advanced device and packaging applications, but both surfaces must be extremely smooth to achieve a uniform bond. Chemical mechanical polishing (CMP) is the ideal process for pre-bond surface preparation. This work focused on developing a process sequence for DWB of both patterned and unpatterned substrates as part of a project to develop hermetically sealed cavities. Deep cavities were etched into various substrates and a CMP process was developed to achieve a target surface roughness, Ra, below 1 nm on borofloat 33 glass substrates. During the optimization phase, it was found that DWB of a patterned substrate requires not only a smooth contact surface, but also that edge rounding of the patterned cavities be minimized. Finally, a series of samples were prepared and tested for suitability of the final process sequence. Data for bond toughness (J/m2) and hermeticity (MIL-STD-883) clearly show that the technique can produce sealed cavities.
CMP Process for Phase Change Materials
Authors: Liu Feng Q , Ge Chenhao , Xu Kun , Ye Mengqi , Wang Yuchun , Chen Yufei , Xia Sherry , Rosenbusch Anja , Duboust Alain , Tu Wen-Chiang , Karuppiah Lakshmanan
Published: May 2009

Since the CMP process depends on chemical and mechanical effects, the interaction with the physical and chemical properties of the GST alloy play very important roles during the CMP process. In this paper, the impact of the CMP process on a soft GST alloy will be discussed. In addition, the paper addresses how major chemical properties of the GST alloy affect the GST CMP process. For example, in order to remove the three different elements of GST material during the CMP process, it is critical to understand how the alloy's chemical behavior changes when interacting with the CMP slurries. A fully characterized GST CMP baseline process, including its process and defect results, will be presented. The methods used to optimize the CMP process and reduce post-CMP defects will also be discussed.
Challenges in Post CMP Cleaning for Advanced Technology Nodes
Authors: Tamboli Dnyanesh , Rao Madhukar , Banerjee G.
Published: May 2009

Even as CMP technology is maturing, there are several new challenges that are testing the limits of existing post CMP cleaning processes and demand new innovative cleaning solutions. For copper interconnects, the primary challenge comes from likely changes in barrier metal at 32nm node or beyond. A number of materials are being considered to meet these requirements including noble metals such as ruthenium or use of alloying additions such as manganese, which would form a barrier layer to copper diffusion at the metal-dielectric interface. The type of barrier material plays a very important role in galvanic corrosion in form of interfacial corrosion and surface roughening of copper lines during post-CMP cleaning. Additional issues stem from use of hydrophobic and porous dielectrics, which cause issues relating to watermarks, difficulties in removing small particles and chemical penetration inside porous dielectric. In this paper, we discuss in details challenges in these various advanced post-CMP cleaning applications and demonstrate how optimized cleaning solutions can provide necessary cleaning performance.
Electrochemical Fabrication of CoPt Nanodot Arrays on Glass Disks by UV Nanoimprint Lithography
Authors: Ouchi Takanari , Arikawa Yuki , Mizuno Jun , Shoji S. , Homma Takayuki
Published: May 2009

A fabrication process for CoPt nanodot arrays using an electrochemical approach was proposed. The nano-patterned substrates were formed using electron beam lithography (EBL) and UV nanoimprint lithography (UV-NIL). CoPt was electrodeposited into nano-patterned Si substrates. CoPt nandot arrays with 35 nm diameter and 50 nm pitch using EBL and 50 nm diameter and 100 nm pitch using UV-NIL were successfully fabricated. In addition, we attempted to apply 1 inch glass disk substrates with CoZrNb underlayer as soft magnetic underlayer (SUL). We focused on the surface condition of the underlayers to deposit CoPt with uniformity and high magnetic properties. As a result, CoPt nanodot arrays were successfully fabricated on a 1 inch glass disk substrate with SUL using thin Cu intermediate layers. From these results, it has been found that the combination of the UV-NIL and electrochemical processes is a candidate for the fabrication of ultra high-density magnetic recording media.
Electrodeposition of an Iron-Cobalt Phase Isostructural to α-Mn
Authors: Crozier Brendan M. , Liu Qi , Ivey Douglas
Published: May 2009

Electrodeposition at elevated temperatures from a dibasic ammonium citrate-stabilized iron-cobalt electroplating solution is shown to promote the deposition of a metastable phase. The metastable phase is isostructural to α-Mn. XRD analysis indicated that the α-Mn-type phase begins to be deposited at temperatures between 30{degree sign}C and 40{degree sign}C. Below this the equilibrium BCC phase is deposited. Plating at 60{degree sign}C produced deposits composed completely of the α-Mn-type phase. TEM analysis indicated that increasing the plating temperature refined the deposit's grain structure and also led to regions with preferred orientation. Annealing of deposits composed of the α-Mn-type phase above its transformation temperature resulted in the formation of a textured BCC phase. The presence of the α-Mn-type phase led to high deposit coercivities. Annealing of deposits, which resulted in transformation of the α-Mn-type phase to the BCC phase, reduced their coercivities. The coercivities of these films, however, were not reduced to the level of those deposits which were plated as the BCC phase. In deposits completely composed of the BCC phase, either plated as such or transformed, annealing led to higher coercivities. This is attributed to coarsening of the deposit microstructure.
Magnetic Micro Electro-mechanical Systems for Sensor and Actuator Applications
Authors: Gatzen H. H.
Published: May 2009

Sensors and actuators based on magnetic, electromagnetic, and electrodynamic principles allow the realization of a wide range of Magnetic Micro Electro-magnetic Systems (magnetic MEMS). Preconditions for fabricating such devices is the availability of enabling technologies like deposition technologies for magnetic materials or high aspect ratio micro structure technologies (HARMST) for creating coils and core structures. Examples for microsensor applications are the use of either magnetoelastic effects for strain gauge measurements and the inductive effect for measuring the properties of thin-films during the wafer fabrication of magnetic MEMS devices. Magnetic microactuation applications are for instance microactuator with latching capabilities, a rather simple micro synchronous motors, and a hard disc drive (HDD) recording head featuring a Slider with an Integrated Microactuator (SLIM) for second stage actuation.
Electroplated Cu Micro Electrode for the Application in Micro Sinking Electro Discharge Machining (Micro-SEDM)
Authors: Gatzen H. H. , Klocke Fritz , Kamenzky Susanne , Traisigkhachol Ornwasa
Published: May 2009

Fabricating electrodes for Micro Sinking Electro Discharge Machining (Micro-SEDM) using thin-film technology is an attractive alternative to conventional processes. A lithography process taking advantage of a positive photoresist to create a micro mold for electroplating was optimized to reach a thickness in the order of 200 µm at a maximal structure aspect ratio of 10 (structure diameter 20 µm). The resist stability during the electroplating process was investigated. Sample micro Cu electrodes with a length of 167 µm could be deposited in micro mold with a maximal aspect ratio of 8. The paper provides simulation results for Cu and W micro electrodes, a fabrication process for the microelectrode mentioned above, as well as experimental investigations regarding their usage in a Micro-SEDM process.
Development of a 1 kW Solid Oxide Fuel Cell Stack with Anode Supported Planar Cells at NTT
Authors: Hayashi Katsuya , Yokoo Masayuki , Yoshida Yoshiteru , Tabata Yoshitaka , Orui Himeko , Nozawa Kazuhiko , Nozaki Yousuke , Arai Hajime
Published: May 2009

We have developed a 1 kW class solid oxide fuel cell (SOFC) stack composed of 40-50 anode supported planar 120-mm-diameter SOFCs. The 50-cell stack provided an electrical conversion efficiency of 53.4% (based on the lower heating value (LHV) of the methane used as a fuel) and an output of 1120 W when the fuel utilization, current density, and operating temperature were 67%, 0.28 A cm-2, and 1073 K, respectively. The stack operated stably for almost 700 hours. Moreover, the 40-cell stack provided an electrical conversion efficiency of 63.9% (LHV) and an output of 1560 W when the fuel utilization, current density, and operating temperature were 85%, 0.53 A cm-2, and 1073 K, respectively.
The Impact and Mitigation of Carbon Formation on Ni-YSZ Anodes from Biomass Gasification Tars
Authors: Mermelstein Joshua , Millan-Agorio Marcos , Brandon Nigel
Published: May 2009

The combination of Solid Oxide Fuel Cells (SOFCs) and biomass gasification has the potential to become an attractive technology for the production of clean renewable energy. However the impact of tars, formed during biomass gasification, on the performance and durability of SOFC anodes has not been well established experimentally. This paper reports on an experimental study assessment of the performance and mitigation of carbon formation on the anodes of SOFC button cells from synthetic model tars arising from the gasification of biomass material. The anode material was a 60:40 wt.% NiO/YSZ cermet, which was tested in a synthetically generated syngas containing a concentration of up to 15 g/Nm3 biomass gasification tars. It was found that carbon formation in dry conditions significantly damaged the anode of the fuel cell resulting in decreased cell performance and excessive anode polarization resistances. These effects were reduced by applying a load to the cell, and were essentially inhibited once the steam content of the input fuel was > 2%.
A Comprehensive Model for Fuel Cell Exergetic Performance Which Includes Both ASR and Electronic Shorting
Authors: Williams Mark
Published: May 2009

This paper presents the development of a comprehensive model of fuel cell electrochemical performance which incorporates only a general definition of area specific resistance (ASR), but electronic shorting, leakage and other current loss mechanisms. The comprehensive model is demonstrated in this paper for an anode-supported solid oxide fuel cell. The emphasis here is to show the possible effects of electronic shorting and its relationship to performance. The goal is to show or predict the range and extent of possible effects on performance. Through the developed approach, the relationship between shorting and ASR relationship was investigated. ASR can actually go down with increased electronic shorting since current effects ASR.
Detection and Verification of Electrode Flooding in Single Cell Studies
Authors: Dhar Hari P. , Chaudhuri Swades K.
Published: May 2009

Measurements of internal cell resistances in single cells have proven useful in detecting the startup of electrode hydration or the initial stage of flooding. Subtle verification of the startup of flooding of the MEA matrix has been made from the short term performance loss data and resistance data as a function of time. For experimental purposes, self-humidified single cells of electrode area 25 cm2 were built with membrane-electrode assemblies (MEAs) made from a Pt-catalyzed experimental gas diffusion layer (GDL) and a Pt-catalyzed commercial GDL sample. To facilitate flooding, favorable conditions of lower temperature, air flow and air pressure were chosen. The comparative performance decay and the decay with increased performance loss along with steady resistance data with time have been interpreted to mean that the micro-porous layer of the MEA matrix is affected, and that the performance decay consists of contributions from MEA characteristics and electrode flooding.
Analysis of Air Supply in Bellows-Type DMFC by Three-Dimensional Simulation
Authors: Imai Tatsunori , Watanabe Daisuke , Yachi Toshiaki
Published: May 2009

We previously proposed a new DMFC employing a bellows-type assembly. In the conventional structure called the stack type and Planar type, there is a problem of the fuel density varies widely and difficult to achieve connection in parallel. However, in the bellows type structure, the anode and cathode are completely separated. Because of this, it is possible to supply fuel by soaking the entire cell in fuel, and to increase the fuel supply and provide a uniform density. And with this structure, it is easy to connect in parallel. In this paper, The air supply method that was most serious problems in the bellows type structure was studied by three dimensional simulation.
Development of the Pure Hydrogen Production Process from Reductive Gas by Using the Solid Oxide Electrolysis Cells
Authors: Yokota Hiroshi , Yamada Hiroyuki , Shimizu Shunsuke , Noguchi Manabu
Published: May 2009

Our research and development aims to develop an efficient process technology for high-purity hydrogen production with simple system component by using various reductive gases especially by using low calorie gases such as biogas. This process is a high temperature steam electrolysis process using solid oxide electrolysis cells with reductive gas supplied into the anode of the cells. For developing the high performance electrolysis cells, tubular electrolysis cells with thin electrolyte of yttria stabilized zirconia(YSZ) were fabricated. The performance of the electrolysis cell was evaluated by an electrolysis test for single cell using a simulated gas, determining that electrolysis could be achieved at lower voltage than 0.4V with a current density of 320mA/cm2 at 730 degree C. Then, a cell stack of 7 tubular electrolysis cells connected in series was fabricated and the low voltage electrolysis with the cell stack and the hydrogen production from the biogas were successfully demonstrated.
Evolutionary Conservation Levels of Subunits of Histone-Modifying Protein Complexes in Fungi
Authors: Nishida Hiromi
Published: May 2009

Eukaryotes possess a variety of histone-modifying protein complexes. Generally, a histone-modifying protein complex consists of multiple subunits, that is, a catalytic subunit and the associated subunits. In this study, I analyzed 62 and 48 subunits of the histone-modifying protein complexes ofSaccharomyces cerevisiaeandSchizosaccharomyces pombe, respectively. The evolutionary conservation levels of the 110 subunits were measured. The measurements revealed that the conservation levels of the catalytic subunits are significantly higher than those of the associated subunits of the histone acetyltransferase and deacetylase complexes; however, the conservation level of the catalytic subunits is similar to that of the associated subunits of the histone methyltransferase complexes. Thus, in the fungal histone acetylation and deacetylation systems, the catalytic subunits of histone-modifying protein complexes are conserved and the associated subunits are evolutionary lineage-specific. In contrast, in the fungal histone methylation system, both the catalytic and the associated subunits are evolutionary lineage-specific.
Sand Floor for Farmed Blue Foxes: Effects on Claws, Adrenal Cortex Function, Growth and Fur Properties
Authors: Ahola Leena , Koistinen Tarja , Mononen Jaakko
Published: May 2009

Farmed blue foxes (Vulpes lagopus) are traditionally housed on mesh floors where they are unable to perform certain species-specific behaviours, such as digging, which may compromise the animals' welfare. This study describes how a possibility to use in-cage sand floor affects welfare-related variables like growth of the claws, adrenal cortex function, and fur properties in juvenile blue foxes. The foxes (N=32) were housed in male-female sibling pairs in an outdoor fur animal shed in cage systems consisting of two traditional fox cages. For the eight male-female sibling pairs of the Control group, there was a mesh floor in both cages of each cage system, whereas for the eight pairs of the Sand group there was a mesh floor in one cage and a 30–40 cm deep earth floor in the other cage. The results show that sand floor is beneficial for the wearing of the claws of foxes. Furthermore, an early experience of sand floor may have positive effects on the foxes' fur development. The results, however, also suggest that there might appear welfare problems observed as disturbed claw growth and increased adrenal cortex activation if foxes that are once provided with clean and unfrozen sand floor are not allowed to enjoy this floor all the time.
Folate Supplementation Limits the Aggressiveness of Glioma via the Remethylation of DNA Repeats Element and Genes Governing Apoptosis and Proliferation
Authors: Hervouet Eric , Debien Emilie , Campion Loic , Charbord Jeremie , Menanteau Jean , Vallette Francois M. , Cartron Pierre-Francois
Published: May 2009

Purpose: We have investigated whether the folate supplementation could be used to limit the aggressiveness of glioma through the DNA remethylation because (a) the cancer genome is characterized by a low level of DNA methylation (or 5-methylcytosine, 5 mC); and (b) folate is the main generator of S-adenosyl-methionine, the methyl donor molecule in the DNA methylation reaction catalyzed by the DNA methyltranferases.

Experimental Design: The effects of folate supplementations were analyzed on the global DNA methylation status, the methylation status of DNA repeat element, the sensitivity of temozolomide-induced apoptosis, and the proliferation index of glioma cells. Finally, we analyzed whether the DNA methylation level could be used as a prognostic factor and/or a biomarker in an antiglioma therapy using folate supplementation as an adjuvant.

Results: Our data show that gliomagenesis is accompanied by a reduction in 5 mC levels and that this low level of 5 mC is a poor prognostic factor in Glioblastoma Multiforme patients. We also show that folate supplementation enhanced the DNA remethylation through the Sp1/Sp3-mediated transcriptional up-regulation of genes coding for Dnmt3a and Dnmt3b proteins, two de novo methyltranferases. Finally, we show that the folate-induced DNA methylation limits proliferation and increases the sensitivity to temozolomide-induced apoptosis in glioma cells through methylation of the genes implicated in these processes (PDGF-B, MGMT, survivin, and bcl-w).

Conclusion: This study suggests that folate supplementation could be a promising adjuvant for the future design of antiglioma therapies in preclinical and/or clinical studies.
Interstitial telomeric sequences (ITSs) are not located at the exact evolutionary breakpoints in primates
Authors: Farré M. , Ponsà M. , Bosch M.
Published: May 2009

Although their function has not yet been clearly elucidated, interstitial telomeric sequences (ITSs) have been cytogenetically associated with chromosomal reorganizations, fragile sites, and recombination hotspots. In this paper, we show that ITSs are not located at the exact evolutionary breakpoints of the inversions between human and chimpanzee and between human and rhesus macaque chromosomes. We proved that ITSs are not signs of repair in the breakpoints of the chromosome reorganizations analyzed. We found ITSs in the region (0.7–2.7 Mb) flanking one of the two breakpoints in all the inversions assessed. The presence of ITSs in those locations is not by chance. They are short (up to 7.83 repeats) and almost perfect (82.5–97.1% matches). The ITSs are conserved in the species compared, showing that they were present before the reorganizations occurred.
A Positive Breath Hydrogen Test Does Not Predict the Occurrence of a Spontaneous Bacterial Peritonitis in Cirrhotic Patients with Ascites
Authors: Nancey Stéphane , Moussata Driffa , Roman Sabine , Benmansour Hédia , Claudel Sylvette , Flourié Bernard
Published: May 2009

Background/Aims: A positive breath hydrogen test (BH2 T) suggesting the presence of a small intestinal bacterial overgrowth (SIBO) might be a factor increasing the risk of spontaneous bacterial peritonitis (SBP) in cirrhotic patients. In this prospective observational study, we aimed to determine whether a positive BH2 T was associated in time with the development of SBP in cirrhotics with ascites. Methods: During a 3-year period, we prospectively included 29 consecutive cirrhotics with ascites but without previous episodes of SBP or recent antibiotherapy. Every 3 months or before in the event of cirrhosis complications, patients underwent clinical examination, routine laboratory tests, analysis of ascitic fluid and a BH2 T after ingestion of 50 g D-glucose. Results: During a mean follow-up of 12 months (range 3–33), 11 patients were prematurely withdrawn from the study without SBP (3 transplantations, 2 lost to follow-up, 6 deaths from hepatorenal syndrome, terminal liver failure, variceal bleeding or septic shock) and 9 developed SBP. In the 29 patients, 116 BH2 T were performed and were positive 12 times in 8 patients; however, in the same patient the positivity was not constant during the follow-up and not related to the clinical presence of ascites. Among the 9 patients who developed SBP, only 2 had a previous transitory positive BH2 T, which became negative at least 3 months before the occurrence of SBP. Conclusion: In cirrhotics with ascites the diagnosis of SBP is not associated in time with a recent positive BH2 T.