bluuebunny/crossref_metadata_2025 huggingface dataset:
Monolithic Thin Wafer Stacking Using Low Temperture Direct Bonding
Authors: Burggraf Jürgen , Bravin Julian , Wiesbauer Harald , Dragoi Viorel
Published: September 2014

The high process temperature required for silicon oxide fusion bonding (e.g. ~1000°C) prevented its use for 3D applications. In the recent years low-temperature fusion bonding processes (200°C – 400°C) have been developed for addressing such applications. In this study, low-temperature fusion bonding in combination with standard thin wafer manufacturing processes based on temporary bonding/debonding technology in order to demonstrate thin layer direct bonding with subsequent multi-layer stacking capability using standard semiconductor manufacturing bonding equipment. Monolithic integration of two 10µm thin temporary bonded silicon layers onto a standard 775µm thick Si wafer is shown and discussed in detail.
(Invited) Water Stress Corrosion in Bonded Structures
Authors: Fournel Frank , Martin-Cocher Chloé , Radisson Damien , Larrey Vincent , Beche Elodie , Morales Christophe , Delean Pierre-Antoine , Rieutord François , Moriceau H.
Published: September 2014

Direct bonding is now a well-known technique to join two flat surfaces without any additional material. This technique is used in many applications and especially in SOI (Silicon-On-Insulator) elaboration or in some backside imager manufacturing processes which are now almost in mass production. Direct bonding mechanism study is then very important in order to clearly understand this bonding behavior. Especially in the case of silicon or silicon dioxide hydrophilic surface, the role of water is essential. Water could lead to lots of different reactions at the bonding interface and especially the water stress corrosion could play an important role in the direct bonding mechanism.
AlN-AlN Wafer Bonding and Its Thermal Characteristics
Authors: Bao Shuyu , Lee Kwang Hong , Chong Gang Yih , Fitzgerald Eugene A , Tan Chuan Seng
Published: September 2014

Homogeneous bonding was successfully demonstrated on 150 mm Si wafers by face-to-face fusion bonding of two clean and smooth aluminum nitride (AlN) layers. Characterization result from XPS confirms the layer composition and reveals that approximately 5 nm of the layer surface was partially oxidized during processing. The as-bonded wafer pair is nearly void and particle free with a high bonding strength of 1263.0 mJ/m2, enabling it to withstand the subsequent process steps. In addition, the AlN-AlN bonded wafers appear to have the best heat dissipation capability when compared with other bonded wafers, which used SiO2 or Al2O3 as the bonding layer.
Hermeticity and Reliability of Au-Au Thermocompression Bonds, Realized at Low Temperature
Authors: Malik Nisant , Tofteberg Hannah , Poppe Erik , Finstad Terje G , Schjolberg-Henriksen Kari
Published: September 2014

Hermeticity and reliability of four laminates bonded at different temperatures by Au-Au thermocompression bonding have been investigated. Laminates of diameter 150 mm were realized by bonding a wafer containing membrane structures to Si wafers with patterned bond frames. The laminates were bonded applying a bonding pressure of 8.5 MPa at temperatures of 150–300 °C for 15 minutes. The hermetic properties were estimated by measurement of membrane deflection at two different times after bonding. Reliability was tested by exposing the laminates to a steady-state life test, a thermal shock test, and a moisture resistance test. A dicing yield above 90 % was obtained for laminates bonded at or above 150 °C. Laminates bonded at 200 °C and above had significantly higher hermetic yield than the laminate bonded at 150 °C. No degradation in hermeticity was observed after the reliability tests. A maximum leak rate in the range of 10-11 mbar×l×s-1 was estimated.
Temporary Wafer Bonding by Polyelectrolyte Interlayers
Authors: Eichler Marko , Dillmann Helena , Reim Leo Clemens , Thomas Michael , Klages Claus-Peter
Published: September 2014

Polyelectrolyte multilayers of just a few nanometers thickness were used for direct bonding of silicon, thermally oxidized silicon, and borosilicate wafers, respectively, and the bonded wafer pairs were characterized during and after annealing at temperatures up to 350 °C. Determination of surface energy as a measure of bond strength was performed in situ during annealing. The bond strengths show an interesting temperature dependence which can be utilized for temporary bonding of silicon wafers. Infrared transmission photographs as well as FTIR and XPS measurements suggest that the formation of hydrogen bubbles, generated by the reaction between water and silicon, contributes to the debonding at elevated temperatures.
Effects of Miscut Substrates on Electrical Conductivity Across InP and GaAs Wafer-Bonded Structures
Authors: McKay Jeffrey , Seal Mark , Yeung K. , Jackson M. , Goorsky M. S.
Published: September 2014

Wafer bonding of GaAs and InP using an (NH4)2S treatment are investigated for the effect of the wafer offcut angle on the electrical conductivity of wafer-bonded III-V interfaces. HRTEM and STEM are used to confirm the misorientation of the bonded samples and to compare the interface morphology across the range of relative misorientations. A line ratio at the interface shows that the well-bonded crystalline regions to amorphous oxide inclusions is consistent across all bonded samples, indicating that the degree of misorientation does not affect the level of interface recrystallization at high temperatures. Fitting the zero-bias conductance over a range of temperatures reveals an increase in barrier heights for samples with greater than 4° misoriented bonded pairs. This demonstrates that the out-of-plane relative surface misorientation is a critical parameter to be monitored and thus any in-plane twist as well in order to achieve superior electrical conductivity in direct-bonded multijunction solar applications.
Type-II Band Profile of GaAs/Si Hetero Junctions by Surface Activated Bonding for Hybrid Tandem Cells
Authors: Shigekawa Naoteru , Liang Jianbo , Morimoto Masashi , Nishida Shota
Published: September 2014

We fabricated p+-GaAs/n-Si and n+-GaAs/p-Si junctions by using surface activated bonding and measured their current-voltage and capacitance-voltage characteristics at room temperature. Their conduction band offset, which was extracted from the capacitance-voltage characteristics, was 0.57-0.84 eV. The results suggested that the band profiles of junctions had type-II features, which was likely to be preferable for fabricating low-resistance tunnelling junctions in hybrid tandem cells. The influence of possible interface states on the electrical properties of junctions was also discussed using the charge neutral level model.
(Invited) Wafer-Level Integration of Embedded Cooling Approaches
Authors: Paredes Stephan , Madhour Yassir , Schlottig Gerd , Ong Chin Lee , Brunschwiler Thomas
Published: September 2014

New thermal management solutions to keep components within thermal limits are needed to fully exploit the potential of 3D integration of ICs yielding dense electronic systems with increased performance and power efficiency. A roadmap from embedded single-side towards 3D interlayer cooling is presented. The characteristics of single-phase water and two-phase dielectric cooling are discussed further. Dual-side cooling was identified as an intermediate step considering an active cooled interposer combining thermal and electrical functionality. Finally, various design aspects for interlayer cooling in 3D chip stacks are listed that can leverage wafer-level bonding as cost-efficient implementation of such cooling concepts.
Low Activation Temperature Au/Ti Getter Films for Wafer-Level Vacuum Packaging
Authors: Wu Ming , Moulin Johan , Agnus Guillaume , Bosseboeuf Alain
Published: September 2014

In this work thermal diffusion of titanium through an ultrathin capping gold layer has been investigated as an alternative way to produce a getter film activated at low temperature. Ti out-diffusion from Au/Ti thin films was studied using four probe resistivity measurements, XPS analysis, residual stress measurements, SEM cross section observation and Ion Beam Etching coupled with mass spectrometry. The results show that a titanium oxide film is growing as the titanium out diffuses and comes in contact with traces of oxidizing species in N2 annealing gaz. The pumping capacity is large enough to integrate Au/Ti film as a low temperature getter film for wafer-level vacuum packaging.
Voiding Phenomena in Copper-Copper Bonded Structures: Role of Creep
Authors: Gondcharton Paul , Imbert Bruno , Benaissa Lamine , Verdier Marc
Published: September 2014

In 3D integration industrial context, copper is widely favored over others metals as a bonding material for its exceptional electrical and mechanical properties. It has been already reported that directly bonded structures involving copper layers exhibit typical voids that drastically abound beyond 300°C. In order to have a better understanding of the voiding process, we specifically designed structures involving materials and surfaces exhibiting different properties. These stacks underwent different bonding processes which mainly differ in the mechanical applied load. For each variation in this study the total volume of voids was estimated throughout a strict protocol. Thus, we show that voiding phenomena is related to a stress driven vacancy diffusion very comparable to standard metallurgical creep mechanisms. Regarding the origin of the vacancies, among all the possible options, two predominant sources have been identified. Better understanding of these physical phenomena should enable the achievement of advanced wafer assemblies exhibiting much higher reliability and quality.
The Dual-Heterojunction Ge on Si Photodetector
Authors: Sahni Subal , Hon N. K. , Masini Gianlorenzo
Published: September 2014

Metal contact plugs are today commonly used to establish electrical connection to the anode and cathode electrodes of Ge on Si integrated photodetectors. While large progress have been made in optimizing these contacts, scattering loss at the metal regions still remains the most important efficiency limiting factor. In addition, the process used to form the contacts is challenging because of the relatively high attack rate of Ge in aqueous solutions. In this paper an alternative way of building and contacting a Ge diode is presented: leveraging the presence of the Si substrate, highly doped n- and p-type Si regions are formed on the sides of the Ge region replacing metal contacts. These both serve to establish the built in potential in the diode as well as offer a low resistance path for the photocurrent extraction
(Invited) Epitaxial Growth of GeSn Layers on (001), (110), and (111) Si and Ge Substrates
Authors: Nakatsuka Osamu , Taoka Noriyuki , Asano Takanori , Yamaha Takashi , Kurosawa Masashi , Takeuchi Wakana , Zaima Shigeaki
Published: September 2014

We have examined the epitaxial growth of Ge1-Snx on Ge(001), Ge(110), Ge(111), and Si(110) substrates and have investigated the crystalline properties of the epitaxial layers. We found that the Sn incorporation into Ge epitaxial layer effectively suppress the formation of stacking fault and twin growth in low temperature molecular beam epitaxy. We also found the strain relaxation of Ge1-Snx layers strongly depends on the residual strain which is dominated on not only the Sn content but also the substrate orientation. We demonstrate that Ge1-x-ySixSny epitaxial layer lattice-matching to Ge substrate exhibits the high thermal stability thanks to small misfit strain to substrate.
Medium Voltage Hybrid Si IGBT/SiC JBS Diode Module Development
Authors: Hobart Karl D , Imhoff Eugene A , Ray Biswajit
Published: September 2014

Medium voltage SiC Junction Barrier Schottky (JBS) diodes are considered as a replacement for conventional Si freewheeling PiN diodes in phase-leg applications. While lower voltage SiC Schottky diodes are commercially available, medium voltage SiC JBS diodes are also attractive due to their relative simplicity and thus potential for low cost. In this work, the performance of 4.5 kV SiC JBS diodes paired with Si IGBTs is reviewed and compared to legacy components. Hybrid Si/SiC module design and performance are reviewed and potential reliability issues are examined.
A Critique of Wide Bandgap (WBG) Power Semiconductor Device Datasheets
Authors: Shenai Krishna
Published: September 2014

Power switching devices fabricated using wide bandgap (WBG) semiconductors such as Silicon Carbide (SiC) and Gallium Nitride (GaN) have the potential to make transformative impact on electrical energy generation, transmission, distribution, conditioning, and utilization [1]. Although SiC power diodes and power MOSFETs are commercially available for voltage ratings up to 1,700 volts, a careful review of the datasheets suggests severe shortcomings and the need for improved consistency, parameter definition and standardization in order for application engineers to adapt this new technology with trust and confidence. This paper provides a critique of WBG datasheets with recommendations for specific improvements.
GaN Based Optoelectronic Devices: From Ultraviolet Detectors and Visible Emitters towards THz Intersubband Devices
Authors: McClintock Ryan , Razeghi Manijeh
Published: September 2014

III-Nitride material system (AlGaInN) possesses unique optical, electrical and structural properties such as a wide tunable direct bandgap, large longitudinal optical phonon energy, inherit fast carrier dynamics; good carrier transport properties, high breakdown fields; and high robustness and chemical stability. Thanks to these inherit advantages, they are investigated for everyday to military and scientific applications such as illumination sources; bio-agent detection, concealed weapons/drugs detection; and space exploration. With continuous developments in material growth/characterization and device processing/measurement technologies, gap engineered III-Nitride materials extend their unique solutions from ultraviolet and visible regime towards THz spectra.
Multi-Cycle High Temperature Rapid Thermal Annealing for Dislocation Elimination in 4H-SiC Epitaxy
Authors: Mahadik Nadeemullah A , Tadjer Marko J , Stahlbush Robert E , Imhoff Eugene A , Feigelson Boris
Published: September 2014

High temperature annealing of carbon capped SiC epilayers was performed using multi-cycle rapid thermal annealing technique to eliminate basal plane dislocations (BPD) and preserve the surface morphology. Annealing was performed in temperature range of 1750 oC – 1875 oC at N2 overpressure of 0.55MPa and 0.7MPa. BPDs in the epilayers were found to be eliminated for annealing at 1875 oC for 5 mins with 20 multiple heating cycles under 0.55MPa N2 overpressure. Under high temperature annealing, the BPDs convert to threading edge dislocations, which glides in the epilayers as the BPD retracts towards the substrate.
Design and Performance of Compact Air-Cooled SiC MOSFET Inverters for Low-Power Variable Speed Drive Applications
Authors: Bellur Dakshina-Murthy , Kunin Sergey , Ayana Elias , Palmer Brad , Leonarski Jaroslaw , Varigonda Subbarao , Shenai Krishna
Published: September 2014

Design and experimental results of a scalable and modular air-cooled power inverter using commercial SiC power MOSFETs are reported. Compared to the well-established silicon IGBT power inverter, the new SiC power MOSFET inverter offers 40% more output power and 4% higher efficiency for a 10kW, 20kHz air-cooled design. A detailed design and performance tradeoff is presented from a system-level perspective in terms of cost/kW for SiC inverter for vehicle electrification and power generation applications. The design is based on a simple circuit simulation model developed from measurements made on commercially available packaged discrete SiC power MOSFETs.
Reliability of Commercially Available SiC Power MOSFETs
Authors: Lelis Aivars , Green Ron , El Mooro , Habersat Dan
Published: September 2014

Results are presented indicating a disparity in the response of different vendors’ commercially available SiC power MOSFETs to bias temperature stressing. In addition, it was observed that bias-temperature stress under negative gate bias led to larger shifts in the threshold voltage than under positive gate bias.
A Simple and Accurate Circuit Simulation Model for High-Voltage SiC Power MOSFETs
Authors: Pozo Arribas Alejandro , Krishnamurthy Mahesh , Shenai Krishna
Published: September 2014

A complete and simple methodology to model SiC Power MOSFETs is presented in this paper. A simple and accurate model is defined in SPICE language. The core of the model is a Level 1 MOSFET, accounting for temperature dependence and voltage dependence of the gate-drain capacitance. All the values used to define these components can be easily extracted from measurements and/or datasheet. The model finds the best trade-off between simplicity and accuracy, required to perform fast and efficient simulations of power converters.
High, Low, and Zero Field Spin Dependent Recombination in 4H SiC Metal Oxide Semiconductor Field Effect and Bipolar Junction Transistors
Authors: Lenahan Patrick M , Cochrane Corey , Lelis Aivars
Published: September 2014

Silicon carbide based transistors have great promise in high temperature and high power applications. In particular, the great promise of silicon carbide based metal oxide semiconductor field effect transistors (MOSFETs) has been somewhat limited by materials physics problems in the region near the silicon carbide-silicon dioxide interface. Materials physics problems in SiC bipolar junction transistors (BJTs) are also topics of current interest. Studies involving a combination of high, low, and zero field electrically detected magnetic resonance via spin dependent recombination provide a powerful approach for the understanding of SiC transistor materials physics problems. In this paper, we will review our group’s work on multi-field spin dependent recombination of 4H SiC based MOSFETs and BJTs. We emphasize the physical principles involved in the measurements in part because they could potentially be quite useful if they were to be applied to other wide band gap semiconductor device systems.
Digital Control of DC-DC Converters Employing Wide Band Gap (WBG) Power Devices
Authors: Guo Liping , Pozo Arribas Alejandro , Krishnamurthy Mahesh , Shenai Krishna , Wang Ju
Published: September 2014

Next generation power supplies used in particle accelerator infrastructure need to be efficient, compact and reliable with excellent long-term stability and minimal noise in output current. This paper evaluates the performance of silicon carbide (SiC) power MOSFETs and the design and evaluation of a digital control system for dc-dc converters to power electromagnets at Argonne National Laboratory’s Advanced Photon Source. It is shown that the same control system used for a silicon IGBT may be applicable for a SiC power MOSFET in order to achieve the overall system stability while achieving significant reduction in power losses.
Advances in Diamond Integration for Thermal Management in GaN Power HEMTs
Authors: Anderson Travis J , Hobart Karl D , Tadjer Marko J , Koehler Andrew D. , Feygelson Tatyana I , Pate Bradford B , Hite Jennifer K. , Kub Fritz J , Eddy Charles R.
Published: September 2014

GaN high electron mobility transistors (HEMTs) performance is limited by self-heating during high power operation. Topside nanocrystalline diamond (NCD) layers have been integrated on AlGaN/GaN (HEMTs) to improve thermal management, exhibiting a 20%. decrease in peak channel temperature compared to reference HEMTs in a scalable process. Processing improvements, such as eliminating the SiN
x
passivation interlayer and developing a sacrificial gate process are being actively pursued. Also, boron doped p+-NCD films were implemented as gate electrodes for the AlGaN/GaN HEMT for a thermally stable heat-spreading gate contact.
Studies of Relaxation Processes and Basal Plane Dislocations in CVD Grown Homoepitaxial Layers of 4H-SiC
Authors: Wang Huanhuan , Wu Fangzhen , Yang Yu , Guo Jianqiu , Raghothamachar B , Dudley Michael , Zhang Jie , Chung Gil , Thomas Berndt , Sanchez Edward K , Mueller Stephan , Hansen Darren , Loboda Mark
Published: September 2014

Dislocation behavior during homo-epitaxy of 4H-SiC on offcut substrates by Chemical Vapor Deposition (CVD) has been studied using Synchrotron X-ray Topography and KOH etching. Studies carried out before and after epilayer growth have revealed that, in some cases, short, edge oriented segments of basal plane dislocation (BPD) inside the substrate can be drawn towards the interface producing screw oriented segments intersecting the growth surface. In other cases, BPD half-loops attached to the substrate surface are forced to glide into the epilayer producing similar screw oriented surface intersections. These screw segments subsequently produce interfacial dislocations (IDs) and half-loop arrays (HLAs). We also report on the formation of IDs and HLAs generated from: (a) surface sources of BPDs; (b) micropipes; (c) 3C inclusions; and (d) substrate/epilayer interface scratches. The HLAs are known to result in Shockley fault expansion within the epilayer which results in forward voltage drop and device failure.
Comparison of the Forward Voltage Drop of Si and SiC High Voltage Diodes
Authors: Gachovska Tanya , Hudgins Jerry L
Published: September 2014

Obtaining a high coefficient of efficiency for a power converter requires that the components used to build it are well chosen. Power semiconductor switches are responsible for significant power loss. For the same breakdown voltage, a silicon carbide (SiC) bipolar device has a significantly thinner, lightly doped drift region (n- base) compared to silicon (Si) devices and, therefore, low switching losses and low voltage drops in the drift region. The forward voltage drop of a bipolar device is the sum of the drift region voltage drop and the junction voltages. The junction voltages of a Si device are significantly smaller as compared to a SiC device since its band gap is smaller. Therefore, for lower voltage devices (< 6.5 kV), the forward voltage drop will be smaller for Si as compared to SiC devices. For high voltage devices, the opposite is true. In this work, physics-based models of Si and SiC diodes were used to calculate the forward voltage drop for different breakdown voltages; and the simulation results are compared to determine the difference between Si and SiC devices.
Angle-Resolved Photoelectron Spectroscopy Studies of Initial Stage of Oxidation on C-Face 4H-SiC
Authors: Sasago Tomoya , Yamahori Shunta , Nohira Hiroshi
Published: September 2014

We have investigated the initial stage of oxidation on C-face 4H-SiC using angle-resolved X-ray photoelectron spectroscopy. Analyses of Si 2p and C 1s photoelectron spectra show that the oxidation rate changes reflecting the crystal structure of 4H-SiC and that the amount of silicon oxycaribide species is the minimum when the oxide thickness is about 0.85 nm.
Accurate Estimation of Switching Losses in SiC Power MOSFET’s
Authors: Pozo Arribas Alejandro , Krishnamurthy Mahesh , Shenai Krishna
Published: September 2014

Accurate estimation of switching losses is difficult in SiC power MOSFET’s because of their low on-state resistance and small inter electrode capacitances. Even a small parasitic component present in the power switching measurement circuitry can cause significant error in the measured loss due to circuit ringing. This paper presents an approach to accurately estimate the switching losses in a high-speed low on-resistance SiC power MOSFET using a combination of circuit modeling and switching measurements.
Merits of Batch ALD
Authors: Dingemans Gijs , Jongbloed Bert , Knaepen Werner , Pierreux Dieter , Jdira Lucian , Terhorst Herbert
Published: September 2014

An overview of the merits and applications of batch ALD in a vertical furnace will be presented. We address new material and process developments and throughput enhancement which are key factors for future high-volume manufacturing applications. We present ALD SbOx as a new material on the batch platform. For the workhorse ALD Al2O3 and TiN materials, experimental and simulation results demonstrate that a reduction in cycle time to <21s does not significantly compromise uniformity, resistivity and step coverage. Moreover, batch ALD offers process flexibility in the mitigation of non-idealities, such as growth inhibition, as will be discussed for thermal ALD AlN. The very low non-uniformities < 1% (1σ) for the latter process demonstrate the competitive film properties that can be achieved by batch ALD. With applications as diverse as metal gates in logic, trench capacitor electrodes, capacitor dielectrics, barrier layers and passivation films, batch ALD has firmly established itself at device manufacturers and foundry sites with significant prospects for emerging markets.
Plasma Enhanced Atomic Layer Deposition on Powders
Authors: Rampelberg Geert , Longrie Delphine , Deduytsche Davy , Detavernier C.
Published: September 2014

During the last decades atomic layer deposition (ALD) gained a lot of interest for coating three dimensional structures with ultrathin conformal films. Although mainly applied on silicon wafers in microelectronics and solar, experimental efforts confirmed the technique is also applicable to powders and particles. This opens a wide window of new opportunities for ALD such as catalytic activation of powder surfaces, encapsulation and modifying powder rheology. Up to recently only thermal ALD on powders had been reported. For some processes however, plasma enhanced ALD (PE ALD) would be preferable. The higher reactivity during PE ALD results in several advantages including higher deposition rates, lower deposition temperatures and higher purity, while it extends the library of materials that can be grown. This paper elaborates on a rotary reactor for thermal and plasma enhanced ALD on powders, including a brief study of coatings like Al2O3, AlN and TiN.
Design Considerations for ZnO Transistors Made Using Spatial ALD
Authors: Nelson Shelby F. , Ellinger Carolyn R. , Tutt Lee W.
Published: September 2014

We have used spatial atomic layer deposition (SALD) to fabricate metal oxide thin-film devices with unusually simple processes. Selective area deposition allows us to fabricate transistors and circuits additively and with digital design variations when used in combination with an inkjet-printed inhibitor. In a second approach, we use the conformal nature of SALD films to produce self-aligned sub-micron channel length vertical transistors that have large alignment tolerances and are suitable for high-performance thin-film electronics. We discuss device design considerations for both architectures.
Highly Luminescent Monolayers Prepared by Molecular Layer Deposition
Authors: Räupke André , Albrecht Fabian , Maibach Julia , Behrendt Andreas , Polywka Andreas , Heiderhoff Ralf , Helzel Jonathan , Rabe Torsten , Johannes Hans-Hermann , Kowalsky Wolfgang , Mankel Eric , Mayer Thomas , Görrn Patrick , Riedl Thomas
Published: September 2014

A general avenue for the controlled preparation of conformal and highly luminescent monolayers of metal chelate complexes is presented, among them tris(8-hydroxyquinolinato)aluminium (Alq3) and bis(8-hydroxyquinoline)zinc (Znq2). Alq3 is an extremely important model compound for organic electronic applications - it has been the electron transporter and luminescent material in the first efficient hetero-structure organic light emitting diode (OLED). The controlled formation of Alq3 or Znq2 monolayers is achieved by functionalization of the substrate with amino groups which serve as initial docking sites for trimethyl aluminum (TMA) or diethyl zinc (DEZ) molecules which datively bind to the amine. Subsequent exposure to 8-hydroxyquinoline (8-HQ) results in the self-limiting formation of highly luminescent monolayers on arbitrary surfaces, e.g. curved 3D objects or highly porous silica aerogels. The growth mechanism is studied by in-situ quartz crystal microbalance and ex-situ by highly sensitive (time-resolved) optical absorption/emission spectroscopy and photo-electron spectroscopy.
ALD and PVD Tantalum Nitride Barrier Resistivity and Their Significance in via Resistance Trends
Authors: van der Straten O. , Zhang X. , Motoyama K. , Penny C. , Maniscalco J. , Knupp S.
Published: September 2014

Tantalum nitride (TaN) processes for barrier applications in advanced dual damascene Cu interconnect metallization schemes were developed and compared in order to study their electrical properties and the impact on via resistance. The limits of various physical vapor deposited (PVD) TaN processes in terms of resistivity were characterized, showing a rapid increase in TaN resistivity when DC sputtering is conducted with high nitrogen flow rates in an Ar/N2 plasma. More incorporation of nitrogen into TaN is observed at low PVD TaN deposition rates, established by applying low DC power sputtering conditions. Via resistance measurements were performed on dual damascene via structures built with either Ta-rich PVD TaN films with a resistivity of ~240 μΩcm, or ALD TaN films with a resistivity of ~5000 μΩcm as barriers. Even though the resistivity of ALD TaN blanket films is significantly higher than PVD TaN, reduced via resistance values were observed as a larger fraction of PVD TaN in the barrier stack was replaced by ALD TaN. For a TaN barrier at 3nm thickness, the via resistance measured for ALD TaN was ~28% lower than its PVD counterpart.
Design, Synthesis and ALD Assessment of Organometallic Precursors for Semiconductor Applications
Authors: Dussarrat Christian
Published: September 2014

As chip dimensions shrink, the delays in circuits are increasingly in a dramatic manner. New challenges are thus arising in processes for scaling and integration, so as to obtain the required performances. This may also include the need of novel transistor architectures, such as FinFET or FD-SOI, at a change of semiconductor node, leading to new material needs. The new associated manufacturing challenges, especially the needs to deposit more conformal metallic thin films, can be translated to new opportunities to introduce the usage of organometallic materials in electronic industry. Relevant precursors, reviewed in this paper, are available for ALD processing already, but there is still room for innovation to overcome downscaling challenges. The study of heteroleptic chemistries, e.g. consisting in the use of different ligands around the metal, is suggested to take advantage of advantageouns physical properties and improved process features, compared to their homoleptic counterparts.
(Invited) Single-Grain Si Tfts Fabricated on a Precursor from Doctor-Blade Coated Liquid-Si
Authors: Zhang Jin , Trifunovic Miki , van der Zwan Michiel , Takagishi Hideyuki , Shimoda Tatsuya , Ishihara Ryoichi
Published: September 2014

Printing is attractive for manufacturing flexible circuits. This manuscript presents our investigation of single-grain Si TFTs fabricated from printed liquid-Si, on a polyimide substrate with the maximum process temperature of 350 °C. The field-effect mobility is 460 cm2/Vs for electrons and 121 cm2/Vs for the holes. CMOS inverters were also fabricated. The devices function at the bending diameter of 3 mm. The device performance under the bending stress was discussed.
(Invited) Extraction of Trap Densities in TFTs using C-V Characteristics
Authors: Kimura Mutsumi , Matsuda Tokiyoshi
Published: September 2014

We will introduce device characterizations based on low-frequency capacitance-voltage methods and numerical analysis. First, surface potential is acquired, next, spatial distribution of the trap states is assumed, and finally, trap densities are extracted. We will also show results acquired for various kinds of TFTs as examples of the device characterizations.
(Invited) Analysis of Thermal Degradation in Oxide Thin Film Transistors
Authors: Uraoka Yukiharu , Urakawa Satoshi , Ishikawa Yasuaki
Published: September 2014

We have investigated the thermal degradation of oxide TFT with various gate length and width under various gate and drain voltages by using an infrared imaging system. An asymmetrical thermal distribution was observed at a local drain region in a TFT depending on bias stress. Threshold voltage shift was observed with stress time depending on the gate width. We discussed the degradation mechanism by analyzing the electrical properties and thermal distribution. We considered that the degradation phenomena are caused by a combination of Joule heating and the hot carrier effect. This model was confirmed by theoretical device simulation.
Effect of Negative Oxygen Ions on a-IGZO Thin Films by Superimposed RF/DC Magnetron Sputtering
Authors: Kim Doohyun , Jang JinNyoung , Yoon Soobok , Hong MunPyo
Published: September 2014

During the plasma sputtering process, the effects of the negative oxygen ions (NOIs) on the thin film properties of amorphous indium-gallium-zinc oxide (a-IGZO) has been investigated. While the energies of NOIs effectively controlling by using a superimposed rf/dc magnetron sputtering system, the energies of NOIs extracted by in situ analyses with ion energy analyzer are good agreement with the calculated values by the Kevin Meyer equation. Furthermore, we find that the observed energies of NOIs are enough high to cause a lattice distortion and/or displacement in a-IGZO thin films. Our work demonstrates the bombardment of NOIs is one of a crucial issue to achieve the high quality a-IGZO films.
(Invited) Solution Processed Oxide Thin Film Transistors
Authors: Avis Christophe , Jang Jin
Published: September 2014

The performance of oxide thin-film-transistors (TFTs) by solution process is investigated. From the choice of precursors to the TFTs, each step has its own importance to produce high performance TFTs. The TFT performance is also enhanced by the use of high-k dielectrics such as aluminum oxide (AlOx) instead of silicon dioxide (SiO2). We discuss the performance of both crystalline (SnO2, In2O3) and amorphous (ZTO, IZTO) active materials, manufactured by inkjet-printing. Field-effect mobility of 110cm2/Vs is achieved.
(Invited) Flexible Sensors Based on Low-Temperature Polycrystalline Silicon Thin Film Transistor Technology
Authors: Fortunato Guglielmo , Maiolo Luca , Maita Francesco , Minotti Antonio , Mirabella Salvo , Strano Vicky , Metta Giorgio , Ricci Davide , Pecora Alessandro
Published: September 2014

Flexible sensors are gaining increasing interest in a number of applications, including biomedical, food control, domotics and robotics, having very light weight, robustness and low cost. Low temperature polycrystalline silicon (LTPS) technology is particularly attractive for such applications, since LTPS TFTs show excellent electrical characteristics, good stability and offer the possibility to exploit CMOS architectures. Then, as examples of flexible sensing systems, we present a tactile sensor for robotic applications and a pH sensor for biomedical applications. The present results can pave the way to advanced flexible sensing systems, where sensors and local signal conditioning circuits can be integrated on the same flexible substrate.
Quadratic Prediction Models for the Performance Comparison of a Marine Engine Fuelled with Biodiesels B5 and B20
Authors: Poompipatpong Chedthawut
Published: September 2014

According to Thailand’s renewable energy development plan, biodiesel is one of the interesting alternative energies. In this research, biodiesels B5 and B20 are tested in a marine engine. The experimental results are then compared by using three different techniques including (1) the conventional technique, (2) average of the point-to-point comparisons, and (3) a comparison by using quadratic prediction models. This research aims to present the procedures of these techniques in-depth. The results show that the comparison by using quadratic prediction models can accurately predict ample amounts of results and make the comparison more logical. The results are compatible with those of the conventional technique, while the average of the point-to-point comparisons shows diverse results. These results are also explained on the fuel property basis, confirming that the quadratic prediction model and the conventional technique are practical, but the average of the point-to-point comparison technique presents an inaccurate result. The benefit of this research shows that the quadratic prediction model is more flexible for future science and engineering experimental design, thus reducing cost and time usage. The details of the calculation, results, and discussion are presented in the paper.
Systemic Granulomatous Diseases Associated with Multiple Palpable Masses That May Involve the Breast: Case Presentation and an Approach to the Differential Diagnosis
Authors: Jales Rodrigo Menezes , Pereira Patrick Nunes , Stelini Rafael Fantelli , Moro Luciano
Published: September 2014

Palpable mass is a common complaint presented to the breast surgeon. It is very uncommon for patients to report breast mass associated with palpable masses in other superficial structures. When these masses are related to systemic granulomatous diseases, the diagnosis and initiation of specific therapy can be challenging. The purpose of this paper is to report a case initially assessed by the breast surgeon and ultimately diagnosed as granulomatous variant of T-cell lymphoma, and discuss the main systemic granulomatous diseases associated with palpable masses involving the breast.
Ribavirin at the Era of Novel Direct Antiviral Agents for the Treatment of Hepatitis C Virus Infection: Relevance of Pharmacological Monitoring
Authors: Pradat Pierre , Virlogeux Victor , Gagnieu Marie-Claude , Zoulim Fabien , Bailly François
Published: September 2014

Ribavirin is often used for the treatment of hepatitis C virus (HCV) infection. Although its mechanisms of action remain to be clearly elucidated, ribavirin plays a beneficial role for achieving virological response and decreasing the rate of virological relapse after treatment cessation. However, ribavirin may induce side effects leading to early treatment discontinuation. Among them, hemolytic anemia is the most frequent and results from intraerythrocyte accumulation. Pharmacological studies have shown that early ribavirin exposure assessed by the area under the curve (AUC) at day 0 and ribavirin trough concentration during the first three months of therapy were correlated with sustained virological response (SVR). These studies highlighted the relevance of ribavirin pharmacologic monitoring and early dose adaptation during therapy. Although the role of ribavirin within new direct acting antiviral (DAA) combinations will probably decrease in the future, its potential benefit in difficult-to-treat patients such as patients with severe hepatopathy or patients who failed triple therapy including patients with multiresistance will need to be further investigated.
Searching for the Determinants of Climate Change Interest
Authors: Cavanagh Patrick , Lang Corey , Li Xinran , Miao Haoran , Ryder John David
Published: September 2014

A meaningful CO2 mitigation policy is unlikely at the national level in the United States. What is currently happening and what is much more likely to occur in the future are city and regional level efforts of mitigation and adaptation. This paper aims to understand the geographic and socioeconomic characteristics of metropolitan areas and regions that lead to engagement with the issue of climate change. We use geographically explicit, internet search data from Google to measure information seeking behavior, which we interpret as engagement, attention, and interest. Our spatial Hot Spot analysis creates a map that potentially could be harnessed by policymakers to gauge mitigation support or adaptation potential. The results of our multivariate analysis suggest that socioeconomic factors are the strongest determinants of search behavior and that climate and geography have little to no impact. With regard to political ideology, we find evidence of a nonlinear, inverse-U relationship with maximum search activity occurring in metropolitan areas with a near even political split, suggesting that parity may be good for engagement.
e-Waste Management Scenarios in Malaysia
Authors: Suja Fatihah , Abdul Rahman Rakmi , Yusof Arij , Masdar Mohd Shahbudin
Published: September 2014

e-Waste, or electronic waste, disposal that is uncontrolled can be harmful to human health and the environment because e-waste contains toxic substances and heavy metals. However, if the waste is properly managed, it can become a business opportunity that produces high returns because e-waste also contains valuable materials, such as gold, silver, platinum, and palladium. The government of Malaysia wants to ensure the safe, effective, and economically beneficial management of e-waste in Malaysia. Management approaches have included law enforcement and regulation and the promotion of e-waste recovery activities. e-Waste of no commercial value must be disposed of at sites/premises licensed by the Department of Environment (DOE), Malaysia. To date, 18 full recovery facilities and 128 partial recovery facilities that use various available technologies have been designated for the segregation, dismantling, and treatment of e-waste. However, there are issues faced by the recovery facilities in achieving the goal of converting e-waste into a source material. The issues include the e-waste supply, the importation of e-waste derived products and coding, and finally the need to develop the criteria for e-waste processing technologies to ensure the safety and the sustainability of the facilities.
Study on Polymer Modified Cement-Based Coating with Healing Effect on Rusty Carbon Steel
Authors: Wang Kunrong , Liu Zhiyong , Wang Zixiao , Yang Weibin
Published: September 2014

The anticorrosion properties of polymer emulsion modified cement-based coating with healing effect on carbon steel were investigated. The change of linear polarization resistance (Rp) and electrochemical impedance spectroscopy (EIS) have been used to measure the inhibitive and curative effect of electrodes painted with the coating in 3.5% NaCl solution. The results indicated the high alkalinity of filler (cement) in coating can obviously improve the anticorrosion performance of coated steel electrodes. And the inhibitive ability of cement-based coating with fluoride acrylic emulsion is superior to that of the coating with epoxy emulsion. Moreover, by adding antirust pigments and rust converters in the fluoride acrylic emulsion modified cement-based coating, the inhibitive property was improved and the curative effect can be observed.
A Day‐to‐Day Route Choice Model Based on Reinforcement Learning
Authors: Wei Fangfang , Ma Shoufeng , Jia Ning
Published: September 2014

Day‐to‐day traffic dynamics are generated by individual traveler’s route choice and route adjustment behaviors, which are appropriate to be researched by using agent‐based model and learning theory. In this paper, we propose a day‐to‐day route choice model based on reinforcement learning and multiagent simulation. Travelers’ memory, learning rate, and experience cognition are taken into account. Then the model is verified and analyzed. Results show that the network flow can converge to user equilibrium (UE) if travelers can remember all the travel time they have experienced, but which is not necessarily the case under limited memory; learning rate can strengthen the flow fluctuation, but memory leads to the contrary side; moreover, high learning rate results in the cyclical oscillation during the process of flow evolution. Finally, both the scenarios of link capacity degradation and random link capacity are used to illustrate the model’s applications. Analyses and applications of our model demonstrate the model is reasonable and useful for studying the day‐to‐day traffic dynamics.
Role of Renal Nerves in the Treatment of Renovascular Hypertensive Rats withL-Arginine
Authors: Gouvea Sonia Alves , Tiradentes Renata V. , Santuzzi Cintia H. , Mengal Vinícius , Futuro Neto Henrique de A. , Silva Nyam F. , Abreu Gláucia R.
Published: September 2014

The purpose was to determine the role of renal nerves in mediating the effects of antihypertensive treatment withL-arginine in a renovascular hypertension model. The 2K1C (two-kidney one-clip model) hypertensive rats were submitted to bilateral surgical-pharmacological renal denervation. The animals were subdivided into six experimental groups: normotensive control rats (SHAM), 2K1C rats, 2K1C rats treated withL-arginine (2K1C + L-arg), denervated normotensive (DN) rats, denervated 2K1C (2K1C + DN) rats, and denervated 2K1C + L-arg (2K1C + DN + L-arg) rats. Arterial blood pressure, water intake, urine volume, and sodium excretion were measured. The 2K1C rats exhibited an increase in the mean arterial pressure (MAP) (from 106 ± 3 to 183 ± 5.8 mmHg,P<0.01), whereasL-arg treatment induced a reduction in the MAP (143 ± 3.4 mmHg) without lowering it to the control level. Renal nerve denervation reduced the MAP to normotensive levels in 2K1C rats with or without chronicL-arg treatment.L-arg and denervation induced increases in water intake and urine volume, andL-arg caused a significant natriuretic effect. Our results suggest that renal sympathetic activity participates in the genesis and the maintenance of the hypertension and also demonstrate that treatment withL-arg alone is incapable of normalizing the MAP and that the effect of such treatment is not additive with the effect of kidney denervation.
Recurrent Catamenial Pneumothorax Suggestive of Pleural Endometriosis
Authors: Badawy Shawky Z. A. , Shrestha Pujan
Published: September 2014

A 42-year-old multiparous patient presented for consultation as a referral for management of recurrent catamenial pneumothorax. Evaluation by a pulmonologist failed to reveal any chest masses. She was treated for endometriosis using Danazol 800 mg daily for 6 months. Pneumothorax did not recur during treatment and during follow-up visits.
Mastalgia: Prevalence at a Sub-Saharan African Tertiary Hospital
Authors: Makumbi T. , Galukande M. , Gakwaya A.
Published: September 2014

Introduction. Mastalgia is a common breast condition among women referred to breast clinics worldwide. Whereas the prevalence is known in the Western world and Asia, the prevalence of the disease is unknown in many African countries. The aim of this study therefore was to determine the prevalence and describe factors associated with mastalgia among women attending a tertiary hospital in sub-Saharan Africa. Methods. A cross-sectional study was done in Kampala, Uganda. Mastalgia was defined as self-reported breast pain (unilateral or bilateral) for a period not less than two months. A pretested questionnaire was used to collect the data and statistical analysis was performed using SPSS version 11. Ethical approval was obtained. Results. Out of the 1048 women who presented to the breast clinic during the study period, 168 (16%) were diagnosed with mastalgia in the absence of breast cancer. Noncyclical and cyclical mastalgia were 22/168 (13%) and 5/168 (3%), respectively. The onset of noncyclical category as compared to the cyclical type of mastalgia was observed to manifest before 24 years of age (P=0.006). Conclusion. Mastalgia was a common condition among women in this sub-Saharan African setting as is elsewhere. The early onset mastalgia in this sub-Saharan African study requires further exploration for determination of its risk factors.