bluuebunny/crossref_metadata_2025 huggingface dataset:
(Invited) Epitaxial Formation of Graphene on Si Substrates: From Heteroepitaxy of 3C-SiC to Si Sublimation
Authors: Suemitsu Maki , Handa Hiroyuki , Saito Eiji , Fukidome Hirokazu
Published: October 2010

Epitaxial graphene can be formed on Si substrates by a vacuum annealing of a 3C-SiC thin film preformed on Si substrate. In this graphene-on-silicon (GOS) method, graphene grows on three major low-index planes of Si substrates: Si(111), (110), and (100). Despite the difference in the quality of the SiC film depending on the orientation, the quality of the formed graphene shows very little variation, leaving the growth mechanism of graphene on cubic SiC crystals open to future studies. The growth rate of graphene, however, shows a sharp dependence on the orientation, which increases in the order of (111) < (001) < (110).
Novel SiGe Source/Drain for Reduced Parasitic Resistance in Ge NMOS
Authors: Raghunathan Shyam , Krishnamohan Tejas , Saraswat Krishna C.
Published: October 2010

Parasitic resistance issues are an important limitation of Germanium n-channel MOSFETs. We have experimentally investigated the use of SiGe as source/drain material to reduce the parasitic resistance. We have utilized circular TLM (transmission line method) measurement structures to extract the parasitic resistances of these SiGe layers. Results show about two orders of magnitude improvement in specific contact resistivity for insitu-doped n+ SiGe (20% Ge) over 100% n+ Ge layers, thus making it suitable for utilization as source/drain material in Ge NMOS transistors to reduce parasitic resistance, among other benefits.
Non-Contact and Non-Destructive Measurement of Ge and B Content in Si1-xGex/Si Using Very High Resolution Multiwavelength Raman Spectroscopy
Authors: Yoo Woo Sik , Ueda Takeshi , Ishigaki Toshikazu , Kang Kitaek
Published: October 2010

A multi-wavelength, micro-Raman spectroscopy system was designed and used as a non-contact and non-destructive, in-line material and process monitoring tool. A large number of Si1-xGex/Si wafers with varied Ge and B content were prepared and characterized. Ge and B content in the Si1-xGex/Si and Si1-xGex epitaxial layer were estimated from Raman measurements and were compared to those values obtained from secondary ion mass spectroscopy (SIMS), high resolution X-ray diffraction (HRXRD), X-ray reflectance (XRR) measurements for cross-reference. The estimated values were generally in good agreement with average values from other characterization techniques. Multi-wavelength Raman spectroscopy allows non-contact and non-destructive analysis, but with the added advantage of depth profiling capabilities. It is very effective in monitoring and controlling process equipment and process conditions in line.
X-ray Microdiffraction Study on Crystallinity of Micron-Sized Ge Films Selectively Grown on Si(001) Substrates
Authors: Ebihara Kouhei , Harada Shinji , Kikkawa Jun , Nakamura Yoshiaki , Sakai A. , Wang Gang , Caymax Matty , Imai Yasuhiko , Kimura Shigeru , Sakata Osami
Published: October 2010

Using X-ray microdiffraction with a focused beam size of about 0.4 × 1.0 μm2, we investigated the strain relaxation and crystallinity of Ge thin films with areas of 2 × 2 μm2 and 250 × 250 μm2 grown on Si (001) substrates with SiO2 standard shallow-trench-isolation patterning. Results showed slower progression of strain relaxation in the 2 × 2 μm2 Ge films compared to the 250 × 250 μm2 films, which can be attributed to the effects of the SiO2 side walls during annealing.
Misfit Stress Relaxation Mechanism in GeO2/Ge Systems: A Classical Molecular Simulation Study
Authors: Watanabe Takanobu , Onda Tomoya , Ohdomari Iwao
Published: October 2010

The stress relaxation mechanism at the GeO2/Ge interface is studied by means of classical molecular simulation employing empirical force-fields. In general, the chemistry in GeO2 is characterized by weaker bonds and softer bond angles than that in SiO2, which has been considered to lead to the relaxation of the GeO2 film on Ge substrate. However, Ge-O-Ge angle is stiffer than Si-O-Si angle, and has a narrower equilibrium angle of 133o than that of Si-O-Si of 144o. The present simulation results show that the narrow Ge-O-Ge bond contribute the reduction of the compressive stress in the GeO2 films. If the Ge-O-Ge bond angle had the same equilibrium angle with Si-O-Si angle, a higher residual stress would remain in the GeO2 films.
Chemical Trend of Schottky-Barrier Change by Segregation Layers at Metal/Si Interfaces: First-Principles Study
Authors: Nakayama Takashi , Maruta Yusuke , Kobinata Kyousuke
Published: October 2010

Chemical trend of segregation-induced Schottky-barrier modulation and the stability of segregation layers are studied for Au/Si interfaces, using the first-principles calculations. The Schottky barrier for electrons monotonously decreases as increasing the valency of segregated atoms. This variation is shown closely related to how the Si atoms are terminated at the interface.
(Invited) III-V Photovoltaics: Recent Developments and Prospects
Authors: Sosa Norma , Van Kessel Theodore , Martin Yves , Hovel Harold
Published: October 2010

III-V materials are the unchallenged front runner for high-efficiency photovoltaics. This high-efficiency arises from the tunability of the materials system. In particular, III-Vs can be epitaxially grown and, by varying the stoichiometry of binary (ternary or quarternary) systems, the lattice parameter can be controlled to yield devices with very low crystal defect density and simultaneously result in different band gaps. Thus, one p-n junction can be grown epitaxially on top of the next, each absorbing a different portion of the solar spectrum-ultimately yielding multiple p-n junctions in tandem with the ability to harness the solar spectrum more efficiently than a single junction or a typical silicon-based solar cell. Furthermore, III-V photovoltaics have the dual advantage of being applicable in thin-film form and to operate under high concentration. There lies the beauty of III-V photovoltaics. This dual ability is lacking in Si- and CIGS-based PV.
(Invited) Ge/III-V Heterostructures and Their Applications in Fabricating Engineered Substrates
Authors: Bai Yu , Fitzgerald Eugene A.
Published: October 2010

Chip level integration of III-V devices with Si-CMOS platform requires the use of engineered substrates. Fabrication of engineered substrates utilizes technologies such as epitaxy, wafer bonding and layer transfer. We report on two aspects of III-V/IV materials integration developments that are on the path to enabling Ge-on-insulator (GeOI) and GaAs-on-insulator (GaAsOI) on Si substrates without the use of SmartcutTM technology. We report on the establishment of Ge/AlAs/GaAs and GaAs/Ge/GaAs epitaxial structures/sequences with low defect density and surface properties suitable for wafer bonding. The epitaxial structures have embedded layers that offer highly selective etch properties that facilitate lift-off onto Si substrates. We demonstrate the use of these novel Ge/III-V heterostructures to liftoff layers of Ge through an aqueous hydrogen fluoride (HF) based epitaxial lift-off (ELO) process, or layers of GaAs through a gas phased ELO process enabled by xenon difluoride (XeF2) selective etching of Ge.
(Invited) Selective Epitaxial Growth of III-V Semiconductor Heterostructures on Si Substrates for Logic Applications
Authors: Nguyen Ngoc Duy , Wang Gang , Brammertz Guy , Leys Maarten , Waldron Niamh , Winderickx Gillis , Lismont Kevin , Dekoster J. , Loo Roger , Meuris Marc , Degroote Stefan , Buttitta Francesco , O'Neil Barry , Féron Olivier , Lindner Johannes , Schulte Frank , Schineller Bernd , Heuken Michael , Caymax Matty
Published: October 2010

We have deposited III-V alloys on 200 mm Si miscut wafers with an oxide pattern. The selective epitaxial growth (SEG) of GaAs in large windows defined by SiO2 lines on a thick strained-relaxed Ge buffer layer served as a test vehicle which allowed us to demonstrate the integration of a III-V material deposition process step in a Si manufacturing line using an industrial reactor. High quality GaAs layers with high wafer-scale thickness uniformity were achieved. In a subsequent step, SEG of InP was successfully performed on wafers with a 300 nm shallow trench isolation pattern. The seed layer morphology depended on the treatment of the Ge surface and on the growth temperature. Such an approach for the integration of III-V materials on Si substrates allowed us to obtain extended-defect-free epitaxial regions suitable for the fabrication of high-performance devices.
Growth and Optical Properties of InGaAs via Ge-Based Virtual Substrates: A New Chemistry Based Strategy
Authors: Beeler Richard , Weng Change , Tolle John , Roucka Radek , Mathews Jay , Ahmari David A. , Menéndéz Jose , Kouvetakis John
Published: October 2010

In this study, we report the epitaxial integration of InGaAs films on Ge/Si(100) virtual substrates for photonic applications. Ge buffer layers with thicknesses of 400-700 nm were grown directly on vicinal (5 degrees miscut) and on-axis Si (100) wafers using a new low-temperature, chemistry-based approach that allows unprecedented control of film microstructure, morphology and purity at CMOS-compatible conditions. In0.01Ga0.49As0.50 films lattice matched to Ge and with thicknesses in the range of 800-2500 nm were then deposited on both Ge/Si substrates and bulk Ge wafers using industrial MOCVD. All materials were characterized by high-resolution X-ray diffraction, atomic force microscopy, transmission electron microscopy, time-resolved and steady-state photoluminescence, as well as cathodoluminescence. It is found that the properties of the InGaAs/Ge/Si(100) samples are comparable with those grown directly on bulk Ge platforms. Most importantly the films grown on miscut Ge templates are devoid of deleterious antiphase boundaries, making them promising candidates for large scale production of III-V photovoltaics.
Epitaxial Growth on High Aspect Ratio Structures
Authors: Chopra Saurabh , Tran Vinh , Wood Bingxi , Kim Yihwan , Kuppurao Satheesh
Published: October 2010

A continuous scaling of transistor devices is carried out by not only increasing the drive current but also reducing the off-state leakage current. For short channel devices, the reduction of leakage current is increasingly difficult and hence the use of multi-gate devices is looking increasingly more promising. One of the main areas of concern for multi-gate devices is the higher junction resistance due to high aspect ratio structures in these devices. Hence the use of epitaxy in these junctions is inevitable. In this work, we study the impact of process parameters on the final epitaxial junction shapes and how this affects the junction resistance. It is shown that the epitaxial junctions for n- and p-MOS have different shapes and hence will have to be controlled differently for the most optimum integration scheme.
HCl Selective Etching of SiGe versus Si in Stacks Grown on (110)
Authors: Hartmann Jean Michel , Destefanis Vincent , Rabillé Gilles , Monfray Stephane
Published: October 2010

We have investigated the lateral HCl selective etching of SiGe versus Si in various patterned (110) SiGe/Si stacks. Given that Si(110) vertical etch rates are roughly 4 times higher than Si(100) ones, a moderate HCl partial pressure (0.4 Torr) was adopted for this 600-700C study. A definite SiGe versus Si etch selectivity has been demonstrated on (110) for 30-40% of Ge (none for 20% of Ge). SiGe lateral etch rates higher in the [1-10] than in the [001] direction have also been evidenced. A definite increase of both [1-10] and [001] lateral etch rates occurred when increasing the Ge content, the SiGe layer thickness and the etch temperature. Mean selectivities for 15 nm thick layers were however not that high, 20 for Si0.7Ge0.3 and 60 for Si0.6Ge0.4. [1-10] versus [001] etch anisotropy was otherwise minimized for low temperature etches, high Ge content and thick SiGe layers.
Non-Contact and Non-Destructive Characterization of Laser Spike Annealed Si1-xGex/Si Using Very High Resolution Multiwavelength Raman Spectroscopy
Authors: Yoo Woo Sik , Ueda Takeshi , Ishigaki Toshikazu , Kang Kitaek
Published: October 2010

Undoped and B doped Si1-xGex epitaxial layers, on Si(100) wafers with various Ge content and Si1-xGex layer thickness, were prepared and annealed by a laser spike annealing (LSA) system using a 10.6 μm laser beam to investigate the effect of LSA on the integrity of Si1-xGex/Si. Various target wafer temperatures and dwell times were used in the LSA steps. Ge content and lattice level stress were characterized using a multi-wavelength, high resolution micro-Raman (MRS-300) system before and after LSA exposures with various temperatures and dwell times. Strain relaxation of the Si1-xGex and Si was observed, post-LSA, for exposures exceeding a critical temperature (>1190oC). The critical temperature for strain relaxation was higher for Si1-xGex epitaxial layers with low Ge content or high B dopant concentration in the Si1-xGex epitaxial layers.
Defect-Induced Surface Morphological Evolution in Epitaxial Germanium Growth on Silicon
Authors: Huang Yi-Chiau , Tao Xianzhi , Jin Miao , Wang Charles , Sanchez Errol
Published: October 2010

The evolution of surface morphologies during epitaxial germanium growth on silicon substrate by thermal chemical vapor deposition is discussed. When the growth is reaction rate limited, the germanium surface exhibits a thickness-dependent morphology. After a certain thickness of germanium is grown, a distinctive surface protrusion feature is observed. Analysis by transmission electron microscopy shows that the formation of these protrusion features is correlated with the development of in-film defects in germanium that originate from the lattice mismatch between germanium and silicon.
Defectivity Avoidance in Chemical Mechanical Planarization: Role of Multi-Scale and Multi-Physics Interactions
Authors: Chandra Abhijit , Karra Pavan , Bastawros Ashraf
Published: October 2010

A multi-physics model encompassing chemical dissolution and mechanical abrasion effects in CMP is developed. This augments a previously developed multi-scale model accounting for both pad response and slurry behavior evolution. The augmented model is utilized to predict scratch propensity in a CMP process. The pad response delineates the interplay between the local particle level deformation and the cell level bending of the pad. The slurry agglomerates in the diffusion limited agglomeration (DLA) or reaction limited agglomeration (RLA) regime. Various nano-scale slurry properties significantly influence the spatial and temporal modulation of the material removal rate (MRR) and scratch generation characteristics. The model predictions are first validated against experimental observations. A parametric study is then undertaken. Such physically based models can be utilized to optimize slurry and pad designs to control the depth of generated scratches and their frequency of occurrence per unit area.
Effect of CMP Pad and Slurry to STI and ILD Polishing
Authors: Huang David , Babu S.V. , Wang Liangyong , Moser Tim
Published: October 2010

STI (Shallow-Trench-Isolation) and ILD (Inter-layer-Dielectric polishing steps are important polish stages in FEOL (Front-End- of-Line) due to the early stage of transistor device formation. In recent years, ceria based slurries have been used in STI and ILD applications, and the slurry has demonstrated self-stopping capability for better planarization efficiency and wider process window. Many studies have been done on the mechanism of why ceria has better selectivity than silica, particularly at the interface between wafer and abrasive interaction. This paper will focus on the effect of pad properties as well as slurry additives through a detailed pad characterization and slurry formulation study of ceria-based slurry. Polishing tests have been performed to investigate the interaction between wafer, slurry and pad through in-situ friction coefficient measurements. Consumables selection recommendation and polishing mechanism will be discussed as well in this paper.
High Selectivity Slurries for STI CMP
Authors: Ramanathan Srinivasan , Manivannan Ramachandran , Venunath Vineeth
Published: October 2010

Ceria particles were synthesized by two different methods, solid-state displacement reaction method and colloidal method and used for STI CMP. Calcined abrasives were used directly as well as after milling. The effect of calcination parameters on the crystal size was measured. The effect of synthesis method and conditions on the removal rates and the selectivities are presented. Colloidal ceria and calcined ceria showed enhanced selectivity in the presence of DL aspartic acid. There is a strong correlation between the polishing behavior and the calcination temperature and a weak correlation between the polishing behavior and the duration of calcination. Titania and zirconia based slurries were also employed and they exhibited higher selectivities in presence of the additive. Our results show that other multivalent abrasives, such as titania and zirconia, exhibit chemical tooth behavior and the interaction of the additive with the chemical tooth action may explain the enhanced selectivity.
Measurement of Zeta Potential with a Rotating Disk
Authors: Sides Paul J. , Rock Reza L. , Shekhar Sairam C.
Published: October 2010

The ZetaSpin, a tool for measurement of zeta potential on planar disk-shaped samples, also can accommodate fibrous and porous samples in their as-used state. Titration with salt, acid, or base demonstrates the expected dependence on solution parameters, but the magnitudes are much larger than typical. The porous structure causes increased surface current not recognized in the theory for a smooth sample. Adsorbing a probe particle of known zeta potential allows deduction of a correction factor, however, for complex samples. The technique might find application in the measurement of the zeta potential of CMP consumables in the form of fibrous and porous materials.
Breaking-In a Pad for Scratch-Free, Cu Chemical-Mechanical Polishing (CuCMP)
Authors: Eusner Thor , Saka Nannaji , Chun Jung-Hoon
Published: October 2010

This paper presents a quantitative analysis of the topography and material properties of new and broken-in CMP pads. Approximately 50 Cu wafers were polished under typical CMP conditions to break-in the pad. The changes in material properties were measured using a Hysitron TriboIndenter and the changes in the topography of the pad were measured using a Tencor P-10 Profilometer. Additionally, SEM micrographs are presented to show the qualitative difference between broken-in and new pad surfaces. Polishing 56 Cu wafers decreased the average pad modulus from 0.66 GPa to 0.34 GPa and the average pad hardness from 0.05 GPa to 0.03 GPa. Furthermore, as a result of breaking-in the pad, the average asperity radius of curvature increased from 16 μm to 93 μm. The increase in the pad asperity radius of curvature decreased the severity of scratching.
New Materials and Novel Applications for CMP
Authors: Rhoades Robert L.
Published: October 2010

New materials and novel devices are continuing to expand in leveraging the unique capabilities of CMP. Thru silicon vias (TSV's) are being developed for advanced packaging to reduce parasitic losses and shrink form factors. Most TSV process flows rely on CMP at least once, often twice, during the fabrication sequence. Direct wafer bonding requires Angstrom-level smooth surfaces, but CMP can enable bonding of almost anything to almost anything else. In one unique application, CMP enables the formation of hermetically sealed cavities up to several square mm in area and several hundred microns deep. Polycrystalline diamond films can require extremely long polish times due to the intrinsic hardness and chemical inertness of diamond. An optimized CMP process achieves sub-nm roughness of certain kinds of polycrystalline diamond with reasonable polish times and enables fabrication of some very unique resonator designs. These and other new materials and novel applications represent emerging growth areas for CMP.
Chemical Mechanical Planarization Technology for Si Wafer Bonding
Authors: Lim JongHeun , Yoon BoUn , Kim KyungHyun , Ko YoungSun , Kang ChangJin
Published: October 2010

This paper deals with chemical mechanical planarization (CMP) technology to develop 3D (3-Dimentional) stacked Flash Memory. The purpose of IGD CMP in full wafer process is to recover local planarity and surface roughness. Based on small elastic deflection theory, the following formula is derived. CMP Step Height of local planarity H = 3.5×(W×γ/4)1/2 × { 0.75×(1-ν2)/E + 0.75×(1-ν2)/E }1/2 . When this formula is applied, local planarity H should be under 30A, which is confirmed through the experiment. Channel Silicon CMP is the important planarization process to improve the single crystal silicon property. The polished Channel Silicon layer has surface roughness of about 1A rms using colloidal silica based slurry with self stop function.
Effects of CMP Pad Conditioner Properties and Performance on Polishing Pad, Process and Wafer Removal Rate
Authors: Kakireddy Raghava , Galpin Andrew , Smith Joseph , Slutz David
Published: October 2010

The focus of this work is CMP pad conditioners and the impact of diamond shape, size, density and protrusion on pad cut rate, pad surface roughness and wafer removal rate. Conditioner properties such as diamond shape, density and protrusion were found to directly impact the pad cut rate and wafer removal rate. Conditioners with high variation in diamond protrusion and uneven diamond shapes exhibited high drop in pad cut rate and wafer removal rate over the test period. Conditioners with high and very aggressive diamonds led to uneven pad conditioning creating step like features on the pad. Diamonds show wearing off sharp edges and chipping of edges due to mechanical forces exerted on them during conditioning. Also diamonds on some of the tested conditioners were found to be missing or sheared off during conditioning due to the mechanical stress and weak bonding process.
PVA Brush Technology for Next Generation Post-CMP Cleaning Applications
Authors: Singh Rakesh K. , Patel Chintan , Trio David , McNamara Eric , Wargo Christopher
Published: October 2010

This paper presents recent developments in the design and characterization of chemical-mechanical planarization (CMP) consumables, with specific emphasis on post-CMP (PCMP) cleaning polyvinyl alcohol (PVA) brushes. Special nodule design and modified charge super-clean PVA brushes were developed to obtain more effective near-wafer-edge cleaning and significantly improved overall PCMP cleaning performance in advanced applications. The profiled nodule-top, elongated-nodule brushes provided optimum cleaning contact area and contact force at the brush-wafer interface in the wafer edge region, whereas the negative zeta potential (NZP) modified PVA brushes resulted in significantly improved PCMP cleaning efficiency in smaller-node high-sensitive copper/low-k processes. The effects of extended exposure of one alkaline and four acidic PCMP cleaning chemistries on brush PVA discoloration and properties were investigated. All the tested acidic cleans caused significant discoloration, whereas the alkaline clean caused minimal change. Further, all the tested chemistries did not show much change in PVA physical properties and compressive stress.
Advanced Rework Process Development for Cu-CMP at 28 nm Technology Node
Authors: Lin Jen-Chieh , Tsai Teng-Chun , Hsu Chia-Lin , Lin Welch , Huang Chien-Chung , Chen Chih-Hsien , Wu J. Y.
Published: October 2010

Advance Copper chemical mechanical polishing (Cu-CMP) requires more excellent control to Cu remaining thickness post CMP as IC fabrication scales down. But there is no mature technology or end point system to guarantee Cu thickness of processing wafers always well control. And barrier step CU-CMP rework process post 1st CU-CMP is inevitable to address ideal Cu thickness. However, post CMP reworked IC often results in higher Cu line sheet resistance (Rs) value and worse resistance distribution due to worse Cu dishing & more pattern effect comparing with no reworked IC. The experiment tries to find out the most key parameter in order to lower side effect of CU-CMP rework process. After the revolution, reworked IC could achieve very similar electric properties level to no reworked IC approach.
Investigating the Compatibility of Ruthenium Liners with Copper Interconnects
Authors: Tamboli Dnyanesh , Osso Oriol , McEvoy Todd , Vega Lourdes , Rao Madhukar , Banerjee G.
Published: October 2010

Ruthenium is proposed as an alternative liner material in sub 30-nm line-width device technology. Ruthenium is a noble metal and does not oxidize readily. Hence, it is possible to directly plate copper on ruthenium. Because of very low solubility of copper in ruthenium, ruthenium also offers good barrier properties. However, the same noble electrochemical characteristics that prevent the oxidation of ruthenium and so useful for being able to directly plate copper provides challenges in terms of corrosion of copper lines in subsequent wet processing. Copper is electrochemically active to ruthenium. As a result of which, in a galvanic couple with ruthenium copper corrosion will be accelerated. In this paper we will examine the kinetics of galvanic corrosion using novel techniques of in-situ AFM analysis and demonstrate that through chemistry optimization, galvanic corrosion can be minimized.
In Situ Growth of Carbon for Nanoelectronics: From Nanotubes to Graphene
Authors: Rispal Lorraine , Ginsel Pia Juliane , Schwalke Udo
Published: October 2010

We propose in this work a technological transfer of our self-aligned process for carbon nanotube field-effect transistor fabrication to the fabrication of graphene nanoribbon field-effect transistors, based on in-situ grown and etched graphene nano-ribbons.
Highly Efficient Photocatalysts from Nanoscale Metal/Semiconductor/Metal Heterojunctions
Authors: Qu Yongquan , Duan Xiangfeng
Published: October 2010

Photocatalyst-mediated photoelectrochemical processes can utilize photogenerated electrons and holes onsite for photocatalytic redox reactions, and enable the harness and conversion of solar energy into chemical energy, in analogy to natural photosynthesis. However, the photocatalysts available to date are limited by either poor efficiency in visible light range, or insufficient photoelectrochemical stability. Metal/semiconductor/metal heterostructures are designed and synthesized as highly efficient and stable photocatalysts by integrating a nanoscale Schottky photodiode encased in a protective insulating shell with two exposed metal catalysts. As an example, Pt/Si/Ag nanowire heterostructures are synthesized to exhibit efficient photocatalytic activity for a wide range of thermodynamically downhill and uphill reactions, including photocatalytic degradation of organic dyes and toxic pollutants, reduction of metal ions and carbon dioxide, as well as hydrogen generation.
3D Ordered Assemblies of Micro/Nanowires Using Fibrous Building Blocks
Authors: Su Ming , Hong Yan
Published: October 2010

Three-dimensional (3D) ordered assemblies of semiconductive micro/nanowires are made by match-stick assembly of fibrous building blocks (FBBs). A glass tube filled with powders of starting material is processed drawn into centimeter-long, micrometer-diameter FBBs with controlled diameter and spacing. By repeating a draw-cut-stack process, the diameter and spacing of filling material can be programmably reduced from millimeters to hundreds nanometers. The FBBs are densely packed into 3D ordered structures such that wires in one layer are at defined angle (θ) relative to those in the adjacent layers, where θ is between 0 to 180°. The electrical measurements at bundled wires and single wire level confirm semiconducting behavior of wires. By direct manipulating microscale FBBs, the method allows high yield production of 3D ordered micro/nanowires with controlled position and orientation, enabling the construction of a new class of micro/nanomaterials.
The Application of Atomic Layer Deposition for Low Dimensional Nanomaterial Synthesis
Authors: Kim Hyungjun
Published: October 2010

Atomic layer deposition (ALD) has been considered as a promising thin film deposition technique for nanoscale semiconductor device fabrication. Recently, however, the exclusive benefits of ALD make it viable tool for nanotechnology. In this presentation, I will present several examples on the application of ALD for low dimensional nanomaterials synthesis aiming at the next generation electronics. Due to its excellent conformality, ALD is an ideal technique to produce nanomaterials with combination of nanopatterning techniques. Utilizing highly conformal ZnO ALD on the nanohole arrays made by anodized aluminum oxide nanotemplates, low dimensional nanostructures were fabricated. And the constructed nanostructure were applied to fabricate high performance gas sensor. Also, by applying highly conformal ALD processes for transition metals followed by annealing, silicide nanowires were synthesized. Moreover, by adding SiH4 to the NH3 plasma reactant during Co plasma-enhanced ALD process, Co nanorod array was formed on Si substrates without using nanotemplates.
Vertically and Laterally Self-Aligned Double-Layer of Nanocrystals in Nanopatterned Dielectric Layer for Nanocrystal Floating Gate Memory Device
Authors: Hu Quanli , Eom Tae-Kwang , Kim Soo-Hyun , Kim Hyung-Jun , Lee Hyun Ho , Kim Yong-Sang , Ryu Du Yeol , Kim Ki-Bum , Yoon Tae-Sik
Published: October 2010

The formation of vertically and laterally self-aligned double-layer of CdSe colloidal nanocrystals (NCs) in nanopatterned dielectric layer on Si substrate was demonstrated by repeating dip-coating process for NC deposition and atomic layer deposition (ALD) of Al2O3 layer. A nanopatterned-SiO2/Si substrate was formed by patterning with self-assembled diblock copolymer. After the selective deposition of the 1st NC layer inside SiO2 nanopattern by dip-coating, an Al2O3 interdielectric layer and the 2nd NC layer in Al2O3 nanopattern were sequentially deposited. The capacitance-voltage measurement of Al-gate/ALD-Al2O3(25nm)/2nd-CdSe-NCs/ALD-Al2O3(2nm)/1st-CdSe-NCs/nanopatterned-SiO2(15nm) /p-Si substrate structure showed the flatband voltage shift resulting from the charging of NCs.
A Numerical Approach to Transient Currents in a Quantum Dot Connected to a Single Electrode
Authors: Sasaoka Kenji , Yamamoto Takahiro , Watanabe Satoshi
Published: October 2010

We have theoretically investigated the time evolution of electron emission from a quantum dot (QD) to an electrode by the non-equilibrium Green's function technique. We found that the emitted current behavior depends sensitively on the relative position of the energy level of the QD to the Fermi level of the electrode and on the amplitude of gate voltage applied the QD.
Integration and Frequency Dependent Parametric Modeling of Through Silicon via Involved in High Density 3D Chip Stacking
Authors: Cadix Lionel , Fuchs Christine , Rousseau Maxime , Leduc Patrick , Chaabouni Hamed , Thuaire Aurelie , Brocard Melanie , Valentian Alexandre , Farcy Alexis , Bermond Cedric , Sillon Nicolas , Ancey Pascal , Fléchet Bernard
Published: October 2010

Evaluation of Through Silicon Via (TSV) electrical performance is hardly required today to improve heterogeneous 3D chip performance in the frame of a "more than Moore" approach. Accurate modeling of TSV is consequently essential to perform design optimizations and process tuning. This paper proposes a methodology based on RF characterizations and simulations, leading to a frequency dependent analytical model including MOS effect of high aspect ratio TSV. Specific test structures integrated on both floating Si bulk and CMOS 65 nm active wafers according to a face-to-face Via Last After Bonding process enable C(V) and RF measurements. TSV equivalent model including all substrate effects is proposed according to CMOS 65 nm specificities (voltage, frequency, dimensions and Si conductivity) and implemented in SPICE simulator to predict TSV impact on signal propagation.
Modeling of Electromigration Induced Contact Resistance Reduction of Cu-Cu Bonded Interface
Authors: Made Riko I. , Gan Chee Lip , Tan Chuan Seng
Published: October 2010

Metal to metal bonding, particularly Cu-Cu bonding, is an important part of three dimensional integrated circuits (3DICs) that utilizes wafer bonding. The use of Cu to Cu bonding in 3DICs is advantageous as it functions as both the glue layer and electrical interconnection. It has been observed that the contact resistance of bonded Cu interface could be decreased under direct current stressing. In this paper the mentioned phenomena is modeled and simulated. Electromigration induced contact resistance reduction of bonded interconnects may provide a method for post-bonding bond property improvement for 3DICs
From 2D Lithography to 3D Patterning
Authors: Van Zeijl Henk W. , Wei J. , Shen C. , Verhaar T. M. , Sarro P. M.
Published: October 2010

Lithography as developed for IC device fabrication is a high volume high accuracy patterning technology with strong 2 dimensional (2D) characteristics. This 2D nature makes it a challenge to integrate this technology in a 3 dimensional (3D) manufacturing environment. This article addresses the performance of a waferstepper (ASML PAS5000) in several 3D processes ranging form waferbonding and thinning to dual side processing with through silicon vias (TSV). Four different generic expose/etch strategies are discussed to fabricate vertical micro sieves, vertical through wafer silicon plate springs, dual side interconnect with TSV and vertical electrodes in deep silicon channels. It is concluded, that despite the 2D nature of advanced waferstepper lithography a wide range of 3D structures can be fabricated. The multi point alignment capabilities of a waferstepper can improve the overlay in several 3D manufacturing processes and the high accuracy alignment system can be used as a metrology tool for further development of 3D integration processes.
High-Performance 3D Interconnects Based on Electrochemical Etch and Liquid Metal Fill
Authors: Hedler Harry , Scheiter Thomas , Schieber Markus
Published: October 2010

Besides usually known TSV technologies to etch and fill Si interconnects there is a powerful photo assisted electrochemical etch technology for fine pitch TSV which goes hand in hand with a liquid fill metallization. Both together allow the generation of high density wiring on and through thick self carrying interposers, where other technologies fail. Together with any etching technology the liquid fill technology allows an extreme simple process flow to realize conductor lines inside buried channels. Taking the right material combinations there is very low stress inside the substrate, which allows a high design freedom for larger via or systematic aligned via. Using the fill technology for stacked die an extremely simple and compact 3D wiring is possible. It is less complex then conventional ones since it doesn't need any seed layer or additional balls between chips. The fill technology has the potential of complete wiring of multichip systems.
Ultrathin (5-35 nm) SiCNH Dielectrics for Damascene Cu Cap Application: Thickness Scaling and Oxidation Barrier Performance Limitation
Authors: Nguyen Son V. , Haigh Thomas , Shaw Thomas , Molis Steven , Dziobkowski Chet , Zahakos C. , Cohen Steve , Shobha Hosadurga , Liniger E. , Hu C. K. , Bonilla Griselda , Klymko Nancy , Grill Alfred
Published: October 2010

The scaling limit of plasma enhanced chemical vapor deposited (PECVD) ultrathin(5-35 nm) silicon carbon nitride (SiCNH) dielectric as an oxidation and Cu diffusion barrier for damascene process is explored. The SiCNH cap's electrical properties, oxidation barrier performance, and the compositional depth profile analysis results showed that the scaling of the SiCNH cap is limited to 25 nm thickness. Without additional changes in current optimal SiCNH cap, 25 nm is the minimum required thickness for a reliable SiCNH cap in sub-30 nm Cu BEOL devices.
Changes in mitochondrial surface charge mediate recruitment of signaling molecules during apoptosis
Authors: Heit Bryan , Yeung Tony , Grinstein Sergio
Published: October 2010

Electrostatic interactions with negative lipids contribute to the subcellular localization of polycationic proteins. In situ measurements using cytosolic probes of surface charge indicate that normal mitochondria are not noticeably electronegative. However, during apoptosis mitochondria accrue negative charge and acquire the ability to attract cationic proteins, including K-Ras. The marked increase in the surface charge of mitochondria occurs early in apoptosis, preceding depolarization of their inner membrane, cytochrome c release, and flipping of phosphatidylserine across the plasmalemma. Using novel biosensors, we determined that the increased electronegativity of the mitochondria coincided with and was likely attributable to increased exposure of cardiolipin, which is dianionic. Ectopic (over)expression of cardiolipin-binding proteins precluded the increase in surface charge and inhibited apoptosis, implying that mitochondrial exposure of negatively charged lipids is required for progression of programmed cell death.
Effect of activation sequence on transmural patterns of repolarization and action potential duration in rabbit ventricular myocardium
Authors: Myles Rachel C. , Bernus Olivier , Burton Francis L. , Cobbe Stuart M. , Smith Godfrey L.
Published: October 2010

Although transmural heterogeneity of action potential duration (APD) is established in single cells isolated from different tissue layers, the extent to which it produces transmural gradients of repolarization in electrotonically coupled ventricular myocardium remains controversial. The purpose of this study was to examine the relative contribution of intrinsic cellular gradients of APD and electrotonic influences to transmural repolarization in rabbit ventricular myocardium. Transmural optical mapping was performed in left ventricular wedge preparations from eight rabbits. Transmural patterns of activation, repolarization, and APD were recorded during endocardial and epicardial stimulation. Experimental results were compared with modeled data during variations in electrotonic coupling. A transmural gradient of APD was evident during endocardial stimulation, which reflected differences previously seen in isolated cells, with the longest APD at the endocardium and the shortest at the epicardium (endo: 165 ± 5 vs. epi: 147 ± 4 ms; P < 0.05). During epicardial stimulation, this gradient reversed (epi: 162 ± 4 vs. endo: 148 ± 6 ms; P < 0.05). In both activation sequences, transmural repolarization followed activation and APD shortened along the activation path such that significant transmural gradients of repolarization did not occur. This correlation between transmural activation time and APD was recapitulated in simulations and varied with changes in intercellular coupling, confirming that it is mediated by electrotonic current flow between cells. These data suggest that electrotonic influences are important in determining the transmural repolarization sequence in rabbit ventricular myocardium and that they are sufficient to overcome intrinsic differences in the electrophysiological properties of the cells across the ventricular wall.
A tandem repeat of a fragment of Listeria monocytogenes internalin B protein induces cell survival and proliferation
Authors: Mungunsukh Ognoon , Lee Young H. , Marquez Ana P. , Cecchi Fabiola , Bottaro Donald P. , Day Regina M.
Published: October 2010

Hepatocyte growth factor (HGF) is critical for tissue homeostasis and repair in many organs including the lung, heart, kidney, liver, nervous system, and skin. HGF is a heterodimeric protein containing 20 disulfide bonds distributed among an amino-terminal hairpin, four kringle domains, and a serine protease-like domain. Due to its complex structure, recombinant production of HGF in prokaryotes requires denaturation and refolding, processes that are impractical for large-scale manufacture. Thus, pharmaceutical quantities of HGF are not available despite its potential applications. A fragment of the Listeria monocytogenes internalin B protein from amino acids 36–321 (InlB36–321) was demonstrated to bind to and partially activate the HGF receptor Met. InlB36–321has a stable β-sheet structure and is easily produced in its native conformation by Escherichia coli . We cloned InlB36–321(1×InlB36–321) and engineered a head-to-tail repeat of InlB36–321with a linker peptide (2×InlB36–321); 1×InlB36–321and 2×InlB36–321were purified from E. coli . Both 1× and 2×InlB36–321activated the Met tyrosine kinase. We subsequently compared signal transduction of the two proteins in primary lung endothelial cells. 2×InlB36–321activated ERK1/2, STAT3, and phosphatidylinositol 3-kinase/Akt pathways, whereas 1×InlB36–321activated only STAT3 and ERK1/2. The 2×InlB36–321promoted improved motility compared with 1×InlB36–321and additionally stimulated proliferation equivalent to full-length HGF. Both the 1× and 2×InlB36–321prevented apoptosis by the profibrotic peptide angiotensin II in cell culture and ex vivo lung slice cultures. The ease of large-scale production and capacity of 2×InlB36–321to mimic HGF make it a potential candidate as a pharmaceutical agent for tissue repair.
Determinants of plasma membrane wounding by deforming stress
Authors: Oeckler Richard A. , Lee Won-Yeon , Park Mun-Gi , Kofler Othmar , Rasmussen Deborah L. , Lee Heung-Bum , Belete Hewan , Walters Bruce J. , Stroetz Randolph W. , Hubmayr Rolf D.
Published: October 2010

Once excess liquid gains access to air spaces of an injured lung, the act of breathing creates and destroys foam and thereby contributes to the wounding of epithelial cells by interfacial stress. Since cells are not elastic continua, but rather complex network structures composed of solid as well as liquid elements, we hypothesize that plasma membrane (PM) wounding is preceded by a phase separation, which results in blebbing. We postulate that interventions such as a hypertonic treatment increase adhesive PM-cytoskeletal (CSK) interactions, thereby preventing blebbing as well as PM wounds. We formed PM tethers in alveolar epithelial cells and fibroblasts and measured their retractive force as readout of PM-CSK adhesive interactions using optical tweezers. A 50-mOsm increase in media osmolarity consistently increased the tether retractive force in epithelial cells but lowered it in fibroblasts. The osmo-response was abolished by pretreatment with latrunculin, cytochalasin D, and calcium chelation. Epithelial cells and fibroblasts were exposed to interfacial stress in a microchannel, and the fraction of wounded cells were measured. Interventions that increased PM-CSK adhesive interactions prevented blebbing and were cytoprotective regardless of cell type. Finally, we exposed ex vivo perfused rat lungs to injurious mechanical ventilation and showed that hypertonic conditioning reduced the number of wounded subpleural alveolus resident cells to baseline levels. Our observations support the hypothesis that PM-CSK adhesive interactions are important determinants of the cellular response to deforming stress and pave the way for preclinical efficacy trials of hypertonic treatment in experimental models of acute lung injury.
Encoding of the cough reflex in anesthetized guinea pigs
Authors: Canning Brendan J. , Mori Nanako
Published: October 2010

We have previously described the physiological and morphological properties of the cough receptors and their sites of termination in the airways and centrally in the nucleus tractus solitarius (nTS). In the present study, we have addressed the hypothesis that the primary central synapses of the cough receptors subserve an essential role in the encoding of cough. We found that cough requires sustained, high-frequency (≥8-Hz) afferent nerve activation. We also found evidence for processes that both facilitate (summation, sensitization) and inhibit the initiation of cough. Sensitization of cough occurs with repetitive subthreshold activation of the cough receptors or by coincident activation of C-fibers and/or nTS neurokinin receptor activation. Desensitization of cough evoked by repetitive and/or continuous afferent nerve activation has a rapid onset (<60 s) and does not differentiate between tussive stimuli, suggesting a central nervous system-dependent process. The cough reflex can also be actively inhibited upon activation of other airway afferent nerve subtypes, including slowly adapting receptors and pulmonary C-fibers. The sensitization and desensitization of cough are likely attributable to the prominent, primary, and unique role of N-methyl-d-aspartate receptor-dependent signaling at the central synapses of the cough receptors. These attributes may have direct relevance to the presentation of cough in disease and for the effectiveness of antitussive therapies.
Gut T1R3 sweet taste receptors do not mediate sucrose-conditioned flavor preferences in mice
Authors: Sclafani Anthony , Glass Damien S. , Margolskee Robert F. , Glendinning John I.
Published: October 2010

Most mammals prefer the sweet taste of sugars, which is mediated by the heterodimeric T1R2+T1R3 taste receptor. Sugar appetite is also enhanced by the post-oral reinforcing actions of the nutrient in the gut. Here, we examined the contribution of gut T1R3 (either alone or as part of the T1R3+T1R3 receptor) to post-oral sugar reinforcement using a flavor-conditioning paradigm. We trained mice to associate consumption of a flavored solution (CS+) with intragastric (IG) infusions of a sweetener, and a different flavored solution (CS-) with IG infusions of water (23 h/day); then, we measured preference in a CS+ vs. CS- choice test. In experiment 1, we predicted that if activation of gut T1R3 mediates sugar reinforcement, then IG infusions of a nutritive (sucrose) or nonnutritive (sucralose) ligand for this receptor should condition a preference for the CS+ in B6 wild-type (WT) mice. While the mice that received IG sucrose infusions developed a strong preference for the CS+, those that received IG sucralose infusions developed a weak avoidance of the CS+. In experiment 2, we used T1R3 knockout (KO) mice to examine the necessity of gut T1R2+T1R3 receptors for conditioned flavor preferences. If intact gut T1R3 (or T1R2+T1R3) receptors are necessary for flavor-sugar conditioning, then T1R3 KO mice should not develop a sugar-conditioned flavor preference. We found that T1R3 KO mice, like WT mice, acquired a strong preference for the CS+ paired with IG sucrose infusions. The KO mice were also like WT mice in avoiding a CS+ flavor paired with IG sucralose infusions These findings provide clear evidence that gut T1R3 receptors are not necessary for sugar-conditioned flavor preferences or sucralose-induced flavor avoidance in mice.