bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of Varying Dwell Time During Non-melt Laser Annealing of Boron Implanted Silicon
Authors: Zeenberg Daniel , Jones Kevin S , Felch Susan B , Parihar Vijay
Published: April 2011

As the fabrication for the CMOS technology trends to decreasing the size of transistors for the benefit of increased performance and device density, the implant and annealing process technologies are being forced to meet increasingly challenging demands for ultra-shallow junctions. As the current annealing preferences shift from rapid thermal annealing toward sub-second RTP technologies such as flash and laser annealing, the dynamics of micro-structural evolution on the order of milliseconds and microseconds become of increasing importance. To investigate the kinetics in this ultra-fast annealing regime, this study investigated the effect of varying the temperature and time of a scanning laser anneal in the millisecond and microsecond timeframe. Amorphous layers were created in silicon substrates using a 30 keV silicon implant at a dose of 1x1015 ions/cm3. These wafers were then processed using a scanning continuous wave near infra-red laser at varying temperatures and scan rates in order to vary the dwell time of each condition. A combination of sheet resistance, optical interferometry, and secondary ion mass spectrometry characterization techniques were used in order to investigate the activation and diffusion of these laser annealed samples. The regrowth temperature across all samples showed a positive correlation to the sheet resistance; trending toward lower values as temperatures increased. Dwell time, however, showed an inverse effect at lower temperatures. The microsecond anneal at 1200 °C showed a lower Rs than the millisecond anneal, while at higher temperatures the trend reversed. This trending shows an obvious competition between activation and diffusion mechanisms and their dependence on regrowth temperature.
Issues and Optimization of Millisecond Anneal Process for 45 nm node and beyond
Authors: Adachi Kanna , Ohuchi Kazuya , Aoki Nobutoshi , Tsujii Hideji , Ito Takayuki , Itokawa Hiroshi , Matsuo Koji , Yoshinori Honguh , Tamaoki Naoki , Ishimaru Kazunari , Ishiuchi Hidemi
Published: April 2011

We have investigated MSA, namely, Laser Spike Annealing (LSA) and Flash Lamp Annealing (FLA), dopant activation technology of source/drain extension for 45 nm node, which can be substituted for spike RTA. Since it is possible to achieve a similar relation between a sheet resistance and a junction depth by using either FLA or LSA, both annealing methods are capable of providing the junction characteristics required by the ITRS target. However, we have noticed that there are three crucial issues from the viewpoints of device integration and CMOSFET performance: junction leakage current, gate leakage current and pattern dependence. In this report, we discuss these issues and indicate how to cope with them.
Amorphization/templated Recrystallization (ATR) Method for Hybrid Orientation Substrates
Authors: Saenger K. L. , de Souza J.P. , Fogel K.E. , Ott J.A. , Reznicek A. , Sung C.Y. , Yin H. , Sadana D.K.
Published: April 2011

Hybrid orientation substrates make it possible to have a CMOS technology in which nFETs are on (100) Si (the Si orientation in which electron mobility is the highest) and pFETs are on (110)-oriented Si (the Si orientation in which hole mobility is the highest). This talk will describe a new amorphization/templated recrystallization (ATR) method for fabricating bulk hybrid orientation substrates. In a preferred version of this method, a silicon layer with a (110) orientation is directly bonded to a Si base substrate with a (100) orientation. Si regions selected for an orientation change are amorphized by ion implantation and then recrystallized to the (100) orientation of the base substrate. After an overview of the ATR technique and its various implementations, we will describe some of the scientifically interesting materials and integration challenges encountered while reducing it to practice.
Evidence of Reduced Self Heating with Partially Depleted SOI MOSFET Scaling
Authors: Guegan Georges , Gwoziecki Romain , Gonnard Olivier , Gouget Gilles , Raynaud Christine , Casse Mikael , Deleonibus Simon
Published: April 2011

The temperature rise in SOI has been measured on two successive generations. This work shows that self-heating effects become less and less severe with both MOSFET and power supply voltage scaling.
Impact of Pore Size and Morphology of Porous Organosilicate Glasses on Integrated Circuit Manufacturing
Authors: O'Neill Mark , Haas Mary K , Peterson Brian K , Vrtis Raymond N , Weigel Scott J , Wu Dingjun , Bitner Mark D , Karwacki Eugene J
Published: April 2011

Porous organosilicate materials produced by plasma enhanced chemical vapor deposition are the leading candidates for back-end-of-line dielectric insulators for IC manufacturing at 45nm design features and beyond. The properties of porous organosilicate glass films of dielectric constant k=2.50 ± 0.05 formed using diethoxymethylsilane and five different porogen precursors with an ultraviolet post treatment are reported. By varying the porogen precursor type pore sizes of 1-2 nm (equivalent spherical diameter) and porosities in the range of 24-31% were measured. While there were no observable trends in pore size with the molecular volume or plasma reactivity of the porogen precursor, modulus values ranged from 6.6 to 10.8 GPa. Porous films with the highest mechanical properties were found to have the highest matrix dielectric constant, highest network connectivity (lowest methyl content), and highest density. Within this process space, maximizing the network connectivity of the film was found to be more important to mechanical properties than lowering the total porosity. In effect, the choice of porogen precursor dictates the film morphology through its impact on the organosilicate glass matrix and pore size.
Fracture Property Improvements of a Nanoporous Thin Film via Post Deposition UV Curing
Authors: Jacques Jeannette M. , Tsui Ting Y. , McKerrow Andrew J. , Kraft Robert
Published: April 2011

As silicon-based microelectronic devices continue to aggressively scale down in size, traditional BEOL dielectric materials have become obsolete due to their relatively high dielectric constant. Organosilicate glass (OSG) materials have emerged as the predominant choice for intermetal dielectrics in advancing technology nodes. A potential failure mechanism for this class of low-k dielectric films during the manufacturing process is catastrophic fracture due to channel cracking. To improve the mechanical strength and stability of these silicon-based materials, the use of post-deposition curing processes is under evaluation. In this work, the effects of UV curing on the properties of OSG films were characterized. After UV curing, film hardness and elastic modulus are improved, with no change in the residual film stress. The average film density increases linearly as a function of UV exposure time. Channel crack propagation velocities decrease with UV exposure. The improvements in the mechanical properties of OSG films are believed to correlate with the increasing Si-O-Si bond population. Comparisons between post-deposition UV and Electron Beam curing processes are provided.
Detection of Copper and Water in Low-k Dielectrics by Triangular Voltage Sweep Measurements
Authors: Ciofi Ivan , Tökei Zsolt , Saglimbeni Marco , Van Hove Marleen
Published: April 2011

Metal-Insulator-Semiconductor (MIS) planar capacitors were fabricated in order to systematically investigate the effect of Cu and water in Cu/low-k structures by Triangular Voltage Sweep (TVS) measurements. We were able to resolve peculiar features in the TVS traces of Cu and water contaminated samples, which were related to Cu ions and protons, respectively. We demonstrate that these features can be used to distinguish the two ionic species. As these features do not depend on the specific dielectric, we provide a methodology to detect and distinguish Cu and water in porous low-k materials embedded in MIS structures.
Supercritical Fluid Treatment to Improve Dielectric and Mechanical Properties of Porous ULK Thin Films
Authors: Beynet Julien , Jousseaume Vincent , Madec Alain , Rémiat Bruno , Albérola N. Dominique , Mercier Régis , Passemard Gérard
Published: April 2011

Spin-on glass organosilicate films are promising Ultra Low-ĸ (ULK) interlevel dielectric candidates in which porosity can be created by incorporating thermally labile porogens. The as-deposited film (called the hybrid film) consists of a methylsilsesquioxane (MSQ) matrix and an organic porogen. The standard porogen removal step consists of a 450°C thermal annealing. However, it leaves polymeric residues suspected to cause an incomplete matrix crosslinking and, consequently, to be detrimental to the porous film's electrical and mechanical properties. In this work, a supercritical fluid (SCF) treatment, performed on a 200 mm tool, was added before the thermal annealing with the intent of improving the dielectric properties. Electrical and mechanical properties were greatly enhanced: the dielectric constant was reduced from 2.5 to 2.1 and the Young's modulus was increased from 2 GPa to 3 GPa. Porogen residue removal and cross-linking improvements were investigated by Fourier Transform Infrared (FTIR) spectroscopy in transmission and multiple internal reflection (MIR) mode.
Zeolite Low-k Film Properties Dependence on Nanocrystal Size
Authors: Eslava-Fernandez Salvador , Baklanov M.R. , Iacopi F. , S.H. Brongersma , Kirschhock C.E.A. , Maex K.
Published: April 2011

Spin-on pure-silica-zeolite MFI films consist of zeolite nanocrystals embedded in a compacted silica matrix of zeolite primary nanoparticles. They appear to be promising as a low-k material due to their good mechanical properties and high microporosity, parallel to their intrinsic low k-value. Results are promising but the implementation of this material is still far away. To contribute to the implementation we present a study on the final film properties depending on the zeolite MFI nanocrystal size. Different techniques are used for the characterization: Dynamic Light Scattering, X-ray diffraction, Scanning Electron Microscopy, Nitrogen adsorption, EllipsoPorosimetry using toluene and NanoIndentation. The results show a clear dependence of the film properties on the nanocrystal size. Clearly, smaller nanocrystals provide better homogeneity, smaller pore size and higher mechanical properties. However, due to the hydrophilicity of the silica matrix lower k-values are only obtained for larger zeolite nanocrystals which provide with higher crystallinity in the films.
Topographical and chemical surface modification of porous MSQ using silylating agents with different numbers of methoxy groups
Authors: Smith Casey , Mueller Dennis , Matz Phil , Reidy Rick
Published: April 2011

Plasma ash processes that cause surface damage in porous interlayer dielectric materials (ILDs) result in increased water absorption, permittivity, and metal intrusion. In this study, we employ mono-, di-, and tri-functional alkoxide silylation agents in supercritical CO2 to repair O2 ash damaged low-k methylsilsesquioxane (MSQ) films. Fourier transform infrared spectroscopy (FTIR) was performed using normal incidence transmission and attenuated total reflection (ATR) techniques to highlight differences in silylation efficiency based on agent functionality. Contact angle measurements reveal a significant change in hydrophobicity after functionalization of the O2 ashed samples with multifunctional agents. Atomic force microscopy (AFM) was utilized to determine changes in surface topography after ashing and repair.
Effects of Dielectric Thermal Expansion and Elastic Modulus on the Stress and Deformation Fields in Copper Interconnects
Authors: Shen Yu-Lin
Published: April 2011

This study aims at assessing the role played by the coefficient of thermal expansion (CTE) and elastic modulus of low-k dielectric, in affecting the stress and deformation fields in copper interconnects. Parametric finite element analyses are conducted, varying one parameter at a time, for gaining fundamental understanding of the effect of individual properties. The analyses are based on a three dimensional model containing two levels of metal lines connected by a via. It is found that both the high CTE and low modulus values of the polymer-based dielectric contribute to the evolution of stress/strain fields in the metal structure. The low-k CTE plays a more significant role. Within certain limits, decreasing the low-k CTE and/or increasing the low-k modulus can help alleviate the plastic deformation, and thus the propensity of damage initiation, in the metal. Reducing the low-k CTE will be a more efficient and safer approach.
Copper Electroplating on Zero-Thickness ALD Platinum for Nanoscale Computer Chip Interconnects
Authors: Kaloyeros Alain , Zhu Yu , Dunn Kathleen , Mayti Richard , Miller Christopher , Breslin Matthew
Published: April 2011

Ultra-thin platinum (Pt) films grown by atomic layer deposition (ALD) have been investigated as an alternative to conventional physical vapor deposited (PVD) Cu as seed layer for copper (Cu) electroplating. The wetting angles between the electrolyte and both Pt and Cu seed layers were analyzed using sessile-drop contact-angle analysis prior to plating. Both constant current and pulse reverse current (PRC) were applied to electroplate Cu on both types of blanket seed layers. Scanning electron microscope (SEM) revealed that Cu nucleation density on ALD Pt is lower than on its PVD Cu counterpart, after 30 seconds plating using PRC. Nevertheless, Cu nuclei were observed after only 1.0 minute plating on ALD Pt surfaces, and continuous Cu films were achieved at longer plating times. To fill trench structures coated with ALD Pt/TaN, PRC was applied using the same organic-additive-free electrolyte. Initial results suggest that these seed layers were adequate for ECD fill of trenches with 200 nm feature size and aspect ratio 7:1. The composition and microstructure of the Cu films were analyzed by Auger electron spectroscopy (AES), X-ray diffraction (XRD), and cross-sectional transmission electron microscopy (TEM). Thermal stability of the Cu/Pt system was examined by annealing in forming gas at 450°C for 1 hour and subsequent analysis by XRD and TEM.
Scaling of Statistical and Physical Electromigration Characteristics in Cu Interconnects
Authors: Gall Martin , Hauschildt Meike , Justison Patrick , Ramakrishna Koneru , Hernandez Richard , Herrick Matthew , Michaelson Lynne , Kawasaki Hisao
Published: April 2011

Even after the successful introduction of Cu-based metallization, the electromigration (EM) failure risk has remained one of the important reliability concerns for most advanced process technologies. Ever increasing operating current densities and the introduction of low-k materials in the backend process scheme are some of the issues that threaten reliable, long-term operation at elevated temperatures. The main factors requiring attention and careful control are the activation energy related to the dominating diffusion mechanism, the resulting median lifetimes, and the lognormal standard deviation of experimentally acquired failure time distributions. Whereas the origin of the EM activation energy and the behavior of median lifetimes with continuing device scaling are relatively well understood, detailed models explaining the origin and scaling behavior of the lognormal standard deviation are scarce. The statistical behavior of EM-induced void sizes and resulting lifetime distributions appear to be explainable by geometrical variations of the void shapes and the consideration of kinetic aspects of the EM process. Using these models, expected lifetime distributions for future technology nodes can be simulated from current, experimentally obtained void size and lifetime distributions. These simulations have to include geometrical factors of the EM test structures and actual, on-chip interconnects, as well as kinetic aspects of the mass transport process, such as differences in interface diffusivity between the lines. By extrapolating the expected lifetime distributions for future technology nodes from current EM data, it is possible to predict when insertion of new process schemes, such as Cu-alloys and/or metallic coating of the Cu/passivation interface is required.
In-situ Observation of the Formation and Growth of Twin in the Copper Electrodeposits for Ultra Large Scale Integration
Authors: Han Heung Nam , Lee Hyo-Jong , Kim Do Hyun , Lee Ui-hyoung , Cha Pil-Ryung , Oh Kyu Hwan
Published: April 2011

During the self-annealing in the copper electrodeposits for the copper metallization, an in-situ observation of grain growth of the copper at room temperature was performed by using EBSD (electron backscatter diffraction). The thin film structure of the copper electrodeposits after annealing was columnar. New twin was initiated at the front surface of growing twin and grew along the normal direction of the twin boundary between the new and parent twins. It was confirmed that the annealing twin in the copper electrodeposits during the self-annealing have an {111} growth front surface.
Chemical Bonding, Permittivity and Elastic Properties in Locally Modified Organosilicate Glass
Authors: Zschech Ehrenfried , Stegmann Heiko , Hoffmann Patrick , Schmeisser Dieter , Potapov Pavel , Engelmann Hans-Juergen , Chumakov Dmytro , Geisler Holm
Published: April 2011

Changing local electronic polarizability and chemical bonding in OSG in such a way that the effective permittivity - and consequently the electrical performance of the Cu/low-k structure - deteriorates only slightly and that adhesion and stiffness are improved significantly is an extremely challenging task [1], [2]. As the interconnect line spacings continue to shrink, optimization of the electrical and mechanical properties of the ILD material becomes increasingly important for Cu/low-k integration since the effect of thin regions that have been modified by special treatments on the effective material properties, e. g. keff, increases. Composition and chemical bonding, changed by plasma or beam treatments, effect the materials properties significantly. Plasma processes for resist stripping, trench etching and post-etch cleaning remove C and H containing molecular groups from the near-surface layer of OSG. Electron-beam interaction with OSG changes the chemical bonding in the low-k material. In this paper, the effect of chemical bonding on permittivity and elastic modulus is studied. Compositional analysis and chemical bonding characterization of structured ILD films with nanometer resolution is done with electron energy loss spectroscopy (EELS). The fine structure near the C-K electron energy loss edge, allows to differentiate between C-H, C-C, and C-O bonds, and consequently, between individual low-k materials and their modifications. Dielectric permittivity changes are studied based on VEELS (valence EELS) measurements and subsequent Kramers-Kronig analysis. The elastic modulus is determined with atomic force microscopy (AFM) in force modulation (FM) mode. Nanoindentation was applied as a complementary technique to obtain reference data.
Bio-Hybrid Materials for Immunoassay-Based Sensing
Authors: Fang Jonathan , Lan Esther H. , Zhou Jing C. , Dunn Bruce
Published: April 2011

The process of encapsulating antibodies in sol-gel was used for sensing various hormones, specifically cortisol, insulin, and C-peptide. A sol-gel optical biosensor for cortisol has been developed for monitoring of crew health on-orbit during space missions. Our studies involving silica sol-gel materials with competitive immunoassays demonstrated linear calibration for cortisol in the range of 2-60 μg/dL, which covers the physiological range of cortisol blood concentration for an adult (2-28 μg/dL). The method of standard additions was used to analyze human serum samples sent to us from a NASA laboratory. Our sol-gel immunosensor values were typically within 20% of the values obtained by NASA-JSC using traditional immuno-binding techniques, with some values having less than a 5% error. Initial results are presented for sensing the hormones insulin and C-peptide.
Stem Cell Impregnated Carbon Nanofibers/Nanotubes for Healing Damaged Neural Tissue
Authors: Lee Jong Eun , Khang Dongwoo , Kim Yong Eul , Webster Thomas Jay
Published: April 2011

Carbon nanotubes and nanofibers are intriguing materials for medical applications due to their unique mechanical, electrical, and surface properties which have been shown to enhance neural cell functions compared to other central nervous system implants such as silicon. The objective of this study was to determine if stem cells can be combined with carbon nanofibers in the treatment of stroke damaged neural tissue in rats. Preliminary results demonstrate the ability of stem cells to differentiate into neurons when injected with carbon nanofibers into stroke damaged neural tissue. Moreover, little scar tissue formation was observed. Although preliminary, such results indicate promise for the use of carbon nanofibers as novel stem cell delivery vehicles for neural damage.
Newly Developed Fe-Fe2O3/Polyoxocarbosilane Core-Shell Nanocomposite Prepared by Laser Pyrolysis: Characterization and Sensing Properties
Authors: Morjan Ion , Pola Joseph , Alexandrescu Rodica , Dumitrache Florian , Tomescu Adelina , Birjega Ruxandra , Gavrila-Florescu Lavinia , Soare Iuliana , Voicu Ion , Galikova Anna , Ciupina Victor , Bastl Zdenek
Published: April 2011

Nanocomposites of iron /iron oxide/ polyoxocarbosilane were prepared by the IR co-pyrolysis of Fe(CO)5 and HMDSO. Their morphologies, chemical content and thermal behavior were studied by different analytical techniques. For examining the sensing capabilities of the low-polymer content nanocomposite thick films, the variation of the electrical resistance to CO and CH4 gases was tested. A promising behavior as concerning the sensitivity and the selectivity was found.
Modulation of Electronic Properties of Single Wall Carbon Nanotubes by the Presence of an Ionic Shell
Authors: Dobrokhotov Vladimir , Berven Chris
Published: April 2011

We report the change to the band structure of two types of carbon nanotubes due to the presence of an isolated, non-conducting, uniformly charged shell held at a fixed distance above their surfaces. We find that, depending on the chirality of the nanotube, the strain on the lattice causes the dispersion relationships to change. This change can result in a modification of the band structure which can induce a metal-semiconductor transition. We consider these effects as a possible mechanism for heavy-metal ion sensing by functionalized carbon-nanotubes.
Synthesis, Characterisation of WO3 Nanofibers and their Application in Chemical Gas Sensing
Authors: Piperno Silvia , Passacantando Maurizio , Lozzi Luca , Cantalini Carlo , Phani Ratna A. , Santucci Sandro
Published: April 2011

WO3 nanofibers have been produced by a simple method as electrospinnig. This is a process by which polymer nanofibers (with submicron scale diameters) can be formed when a droplet of viscoelastic polymer solution is subjected to high voltage electrostatic field. Polymer PMMA and WCl6 solution mixtures were used as precursors. The nanofiber were characterized morphologically and chemically by XPS, SEM, and XRD measurements and it was found the formation of mixed WOx/PMMA nanowires at room temperature that evolve after annealing at 300°C towards pure WO3 nanofibers as evidenced by XPS measurements. After the characterization the nanofibers have been deposited on the sensor devices to check their gas sensing properties. They show a semiconductor-like behaviour when they are heated and wide variation of the electrical resistance when they are exposure to NO2 gas.
A1Bi3C6 Thin Films as NO Sensors
Authors: Khlyap Halyna , Bilozertseva Violetta , Dyakonenko Nina , Gaman Dmitrii , Mamalui Andrey , Khlyap Hayna M.
Published: April 2011

The paper reports experimental data on growth, morphology, NO sensitivity and electrophysical properties of A1Bi3C6 thin films obtained by means of simple vacuum technology. The investigated samples were condensed onto the glass substrates under deposition rate 0.1-0.5 nm/s at T = 300 K and vacuum level P = 10-3 Pa. AFM investigations of the film surface before and after interaction with aggressive environment demonstrated sufficient sensitivity of the film relief to the aggressive component. Room-temperature electric field-induced characteristics were investigated for metal-semiconductor (MS) Cr/NaBiTe2 structures.
Platform based Detection Technologies from Micro scale to Nanoscale
Authors: Kundura Vindhya , Padigi Sudhaprasanna Kumar , Prasad Shalini
Published: April 2011

Rapid, multiplexed, high throughput detection of proteins is essential for the development of protein biomarkers as sensors. Electrical alignment and detection is a non-invasive, label free technique for rapid identification of bimolecular. We present here a micro fabricated platform based detector for rapidly identifying protein biomarkers present in atherosclerotic plaque for rapid clinical diagnosis of arterial obstruction. This is achieved by electrical assembly of polystyrene beads functionalized with specific antibody receptors (anti-C-reactive protein) .The electrical assembly is achieved using electrophoresis. The polystyrene “bridge” micro structure formed due to electrical assembly aids in the amplification of the antibody-antigen binding event. Antigen (C-reactive protein) at nanogram / ml concentration was detected when binding of the antigen resulted in an amplification of the electrical signal that was measured from the base microelectrode platform. This technique is a demonstration of the application of microscale technology (electrodes) in nanoscale (protein) electrical detection.
Control of Interfacial Structure and Electrical Properties in MBE Grown Single Crystalline SrTiO3 Gate Dielectrics on Si(100)
Authors: Norga Gerd , Marchiori Chiara , Rossel Christophe , Guiller Alexandre , Locquet Jean-Pierre , Siegwart Heinz , Caimi Daniele , Fompeyrine Jean , Seo J. W. , Dieker Christel
Published: April 2011

In this paper, we point out the critical role of oxygen stoichiometry in the solid state epitaxy process used for obtaining 5 A EOT in SrTiO3 gate dielectrics on Si. Incomplete oxygenation of the TiO2 fraction of the amorphous SrO.TiO2 film enhances the inherent tendency of TiO2 to react with Si to yield TiSi2 and SiO2. O2 excess is needed to obtain a crystalline interface after UHV crystallization. The solid state epitaxy process results in heavily oxygen deficient films, whose insulating properties can be recovered by an atomic oxygen treatment.
Correlation of Phase Segregation and Electrical Properties of Low-Power MOSFETs with Hf-based Silicate Gate Dielectric Layers and TaN Metal Gates
Authors: Petry Jasmine , Rittersma Chris , Vellianitis Georgios , Cosnier Vincent , Conard Thierry , Deweerd Wim , Van Berkum Jan G.M.
Published: April 2011

The need for nitridation of Hf silicate is controversial. On one hand, it has not been proven that the nitridation is mandatory to have working devices and on the other hand, it is known to increase the charge density. In this paper, we present a detailed comprehensive study of the role and the need for nitridation of Hf-based silicates deposited by Atomic Layer Deposition (ALD). The results are based on a correlation of Fourier-Transformed Infrared Spectroscopy (FT-IR), X-ray Photoelectron Spectroscopy (XPS), High-resolution Transmission Electron Microscopy (HR-TEM) and electrical measurements (gate leakage and mobility).

It was observed that the phase segregation in gate dielectrics is not detrimental for the gate leakage density at room temperature. However, the leakage current is significantly increased at higher temperature. The incorporation of nitrogen was either done by NH3 anneal (at 800C) or by Decoupled Plasma Nitridation (DPN – 25.9kJ). While the DPN or NH3 anneal prevent phase segregation for 50% Hf silicate, only the NH3 anneal helps prevent the phase segregation of Hf-rich silicate. Furthermore, the NH3 anneal increases the interfacial thickness, which produces a very low gate leakage with only 10% loss in mobility at high field. Interestingly, DPN followed by O2 anneal leads to an advantageous phase segregation of the Hf-rich silicate by transforming the silicate in a HfO2/SiO2-like stack.

As a conclusion, not only the phase segregation of the silicate does not always lead to shorted devices, but it can be beneficial in terms of mobility. However, the phase segregation seems to be responsible for an enlarged trap-assisted conduction mechanism at high temperature. But even if the 50% Hf silicates non-nitrided leads to working devices, the incorporation of nitrogen in the stack improves the Jg/CET trends and is therefore beneficial.
In situ ATR - FTIR spectroscopy of Hf(IV) tert butoxide adsorption on Si and Ge
Authors: Dubey Shilpa , Li Keijing , Bhandari Harish , Hu Zheng , Turner C. Heath , Klein Tonya M.
Published: April 2011

Hafnium oxide ultra thin films on Si (100) are being developed to replace thermally grown SiO2 gates in CMOS devices. In this work, a specially designed Attenuated Total Reflectance - Fourier Transform Infra Red Spectroscopy (ATR-FTIR) reaction cell has been developed to observe chemisorption of hafnium (IV) t-butoxide onto a Si and Ge ATR crystal heated up to 250°C and under 1 torr of vacuum to observe the initial reaction pathways and species on the substrate surface in real time and under typical process conditions. Chemisorption spectra were compared to spectra of the liquid precursor and to spectra generated by density functional theory (DFT) calculations of liquid, monodentate and bidentate absorbed precursor. An asymmetric stretching mode located at ~1017 cm-1 present in the chemisorbed spectra but not in the liquid spectra indicates that the adsorbed hafnium containing group is prevalent as a bidentate ligand according to calculations. Surface concentration of the chemisorbed species was dependant on the substrate temperature and precursor partial pressure allowing for determination of heats of adsorption which was 26.5 kJ/mol on Si.
Characterization of HfO2/Si Exposed to Water Vapor at Room Temperature
Authors: Driemeier Carlos , Martinazzi Elizandra , Baumvol Israel J. R. , Gusev Evgeni
Published: April 2011

HfO2-based materials are the leading candidates to replace SiO2 as the gate dielectric in Si-based metal-oxide-semiconductor filed-effect transistors. The ubiquitous presence of water vapor in the environments to which the dielectric films are exposed (e.g. in environmental air) leads to questions about how water could affect the properties of the dielectric/Si structures. In order to investigate this topic, HfO2/SiO2/Si(001) thin film structures were exposed at room temperature to water vapor isotopically enriched in 2H and 18O followed by quantification and profiling of these nuclides by nuclear reaction analysis. We showed i) the formation of strongly bonded hydroxyls at the HfO2 surface; ii) room temperature migration of oxygen and water-derived oxygenous species through the HfO2 films, indicating that HfO2 is a weak diffusion barrier for these oxidizing species; iii) hydrogenous, water-derived species attachment to the SiO2 interlayer, resulting in detrimental hydrogenous defects therein. Consequences of these results to HfO2-based metal-oxide-semiconductor devices are discussed.
Investigation on the Work Function of Tungsten and Thermal stability of W/SiO2/Si, W/SiON/Si and W/HfO2/Si Gate Stacks
Authors: Jiang Pei-Chuen , Chen Jen-Sue , Cheng K. H. , Hu T. J. , Huang K. B. , Lee F. S.
Published: April 2011

Replacement of poly-Si and SiO2with new gate electrode and high k gate oxide is an inevitable trend for next-generation CMOS integrated circuits. Therefore, work function (£Xm) of gate electrodes as well as the thermal stability and electrical behaviors of MOS capacitors should be understood. In this study, tungsten (W) is applied as the gate electrode and the gate dielectric materials are SiO2, SiON and HfO2. £Xm of W and electrical properties of the MOS structures are investigated. £Xm,measuredof W is calculated from the flat-band voltage (VFB) of MOS capacitors with dielectrics of various thicknesse. For W/SiO2/Si structure, the £Xm,measuredof W is 4.67 V; however, the £Xm,measuredof W in W/SiON/Si and W/HfO2/Si structures is 4.60 V and 4.84 V, respectively. The result means that the £Xm,measuredof W in W/HfO2/Si structures has extrinsic contributions to Fermi level pinning. The phase of as-deposited W is £]-W (or £]-W+£\-W) phase and transfers to £\-W+WO3 mix phase after annealing at 500°C in N2+H2 ambient for 30 min. The trapped charges and oxide charges of dielectric are reduced after annealing. However, the EOT of W/SiO2/Si increases significantly after annealing, indicating the thermal stability of this capacitor is poor.
Electrical and Material Evaluation of the MOCVD TiN as Metal Gate Electrode for Advanced CMOS Technology
Authors: Singanamalla Raghunath , Lisoni Judit , Ferain Isabelle , Richard Olivier , Carbonell Laure , Schram Tom , Yu HongYu , Kubicek Stefan , de Gendt Stefan , Jurczak Malgorzata , de Meyer Kristin
Published: April 2011

The electrical and material characterization of Ti(C)N deposited by metal organic chemical vapor deposition (MOCVD) technique, as metal gate electrode for advanced CMOS technology is investigated. The effects of the plasma treatment, post anneal treatment and the thickness variation of the Ti(C)N film on the flat band voltage (VFB) and effective work function (WF) of the Poly-Si/Ti(C)N/SiO2 Poly-Si/Ti(C)N/SiO2 gate stack s are reported. We found that both the in-situ plasma treatment and post anneal treatment help in reducing the carbon content (organic) in the film making it more metallic compared to the as-deposited films. However, the post anneal treatment was found to be a better option for getting rid of hydrocarbons as compared to plasma treatment from the gate dielectric integrity point of view. The thickness variation of post annealed Ti(C)N film ranged from 2.5 nm to 10 nm lead to WF shift of upto ~350 mV for both Poly-Si/Ti(C)N/SiO2 and Poly-Si/Ti(C)N/HfO2 gate stacks.
Electronic and Atomic Structure of Ge2Sb2Te5 phase change memory material
Authors: Robertson John , Xiong Ka , Peacock Paul
Published: April 2011

Electronic structure calculations are presented for various model structures of the crystalline and amorphous phases of Ge2Sb2Te5 (GST). The structures are all found to possess a band gap of order 0.5 eV, indicating closed shell behaviour. It is pointed out that structural vacancies in A7-like GST are not electronically active. In addition, A7-like structures do not support valence alternation pair (VAP) defects, which are one model of the conduction processes in the glassy phase in non-volatile memories.
Photo-oxidation and the Absence of Photodarkening in Ge2Sb2Te5 Phase Change Material
Authors: Lee Bong-Sub , Xiao Ying , Bishop Stephen G. , Abelson John R. , Raoux Simone , Deline Vaughn R. , Kwon Min-Ho , Kim Ki-Bum , Cheong Byung-ki , Li Heng , Taylor P. Craig
Published: April 2011

Ge2Sb2Te5 is under intense investigation for phase-change memory devices, including rewriteable DVDs where optical illumination is used to switch between the glassy and crystalline states. We investigate the influence of optical irradiation on amorphous phase. Many chalcogenides display photo-oxidation, photodarkening or photo-bleaching, but little has been reported on the Ge-Sb-Te system. Using spectroscopic ellipsometry (SE) and secondary ion mass spectrometry, we determine that the samples have a strong tendency to photo-oxidize; if this is not accounted for, then the analysis of SE data appears to show photodarkening. Other authors recently reported photodarkening in nonstoichiometric GexSb20-xTe80 [Pamukchieva et al., Proc. SPIE 5581, 608 (2004); Pamukchieva et al., J. Optoelectron. Adv. Mater 7, 1277 (2005)], but our analysis suggests that the changes were also the result of photo-oxidation. The oxide has lower value of (n, k) than Ge2Sb2Te5, and can be etched by hydrofluoric acid or water. The photo-oxidation is presumably the result of free carrier generation in the Ge2Sb2Te5. Our observation of negligible photodarkening is consistent with previous works that found less photodarkening in tellurides compared with selenides or sulfides, and that an increase in the mean coordination number, here by Ge addition, further reduces the photodarkening effect.
Photo-induced Metastable State of S8Clusters in Liquid Sulfur
Authors: Sakaguchi Yoshifumi , Tamura Kozaburo
Published: April 2011

It is well known that liquid sulfur undergoes a polymerization transition from S8 rings to the mixture of S8 rings and polymeric chains at Tp=159°C. In addition to the transition, it has been known that there is a transformation from S8ring to a molecular species other than S8ring and polymeric chain below Tpsince 19thcentury. Such molecular species can also be obtained by the illumination of light. Several models of the molecular form have been presented. However, the conclusive model which explains all experimental results has not been settled yet. Recently we measured transient photo-induced optical absorption in liquid sulfur and Munejiri et al. performed first-principles molecular-dynamics simulations to clarify the microscopic origin of the experimental results. The results of the simulations presented a plausible molecular form as the molecular species, which is a tadpole-shaped S8 cluster. We show that the molecular form clearly explains the previous experimental results. A possibility of the formation of an intimate valence alternation pair in the small cluster is also discussed.
What Makes Phase-Change Chalcogenide Alloys Materials of Choice for Optical Data Storage
Authors: Kolobov Alexander , Fons Paul , Tominaga Junji
Published: April 2011

In this paper we discuss properties of phase-change materials that are crucial for their performance
Investigation on Ultra-high Density and High Speed Non-volatile Phase Change Random Access Memory (PCRAM) by Material Engineering
Authors: Yeo E.G. , Shi L.P , Zhao R , Chong T.C.
Published: April 2011

In this paper, ultra-high memory density and high speed non-volatile phase change random access memory (PCRAM) was investigated by material engineering. The melting point, crystallization point and activation energy of crystallization of the Bismuth (Bi) doped Germanium-Antimony-Tellurium (GeSbTe) compound was measured using differential scanning calorimetry (DSC) and compared to other GeSbTe ternary compounds. It was observed that the melting temperature of Bi-doped GeSbTe was lower than that of GeSbTe. On the other hand, its activation barrier was found to be reduced, which in turn increased the speed of crystallization of Bi-doped GeSbTe. Bi-doped GeSbTe was then used as a phase change material in the fabrication of PCRAM devices. The properties of PCRAM fabricated using this material were then compared to those using GeSbTe, with emphasis on the programming current required. The results obtained revealed that lower programming current of up to 40% has been achieved for PCRAM with Bi-doped GeSbTe compared to those with other GeSbTe compounds. Bi-doped GeSbTe also has low RESET current and fast speed of crystallization with scaling, making it a suitable material for high speed, ultra-high density PCRAM fabrication in the future.
Laser Synthesis of Sn-Ge-Sb-Te Phase Change Materials
Authors: Song Wendong , Shi L.P. , Miao X.S. , Chong T.C.
Published: April 2011

Sn-doped Ge-Sb-Te films on Si substrates were prepared by laser synthesis at the different growth temperatures. The compositions of Sn-doped Ge-Sb-Te films were analysized by X-ray photoelectron spectroscopy. The crystal structures of Sn-doped Ge-Sb-Te thin films with a Sn content of less than 30 at% are close to Ge2Sb2Te5. The crystallization behaviors of Sn-doped Ge-Sb-Te films were analyzed by self-developed phase change temperature tester. The crystallization temperatures of Sn4.3Ge32.9Sb28.1Te34.6, Sn9.8Ge20.3Sb28.4Te41.5 and Sn18.8Ge19.5Sb25.3Te36.4 are 141.5, 137.3 and 135.0 °C at a ramp rate of 20 °C/min, respectively. Doping Sn into Ge-Sb-Te will result in a decrease of crystallization temperature. It was also found that crystallization temperature increases with an increase of ramp rate for a phase change material. The activity energy Ea and frequency factor ¦Ô for Sn9.8Ge20.3Sb28.4Te41.5 thin films are 2.42 eV and 1.7 × 1026 Hz, respectively. The crystallization speed of Sn-doped Ge-Sb-Te is estimated to be faster than Ge2Sb2Te5.
Realization of 3D Isotropic Negative Index Materials using Massively Parallel and Manufacturable Microfabrication and Micromachining Technology
Authors: VJ Logeeswaran , Islam M. Saif , Chan Mei Lin , Horsley David A , Wu Wei , Wang Shih-Yuan , Stanley Williams R.
Published: April 2011

In this paper, we present a method to realize a three dimensional (3D) homogeneous and isotropic negative index materials (3D-NIMs) fabricated using a low cost and massively parallel manufacturable microfabrication and microassembly technique. The construction of self-assembled 3D-NIM array was realized through two dimensional (2-D) planar microfabrication techniques exploiting the as-deposited residual stress imbalance between a bi-layer consisting of e-beam evaporated metal (650nm of chromium) and a structural layer of 500nm of low stress silicon nitride deposited by LPCVD on a silicon substrate.

A periodic continuation of a single rectangular unit cell consisting of split-ring resonators (SRR) and wires were fabricated to generate a 3D assembly by orienting them along all three Cartesian axes. The thin chromium and silicon nitride bi-layer is formed as hinges. The strain mismatch between the two layers curls the structural layer (flap) containing the SRR upwards. The self-assembled out-of-plane angular position depends on the thickness and material composing the bi-layer. This built-in stress-actuated assembly method is suitable for applications requiring a thin dielectric layer for the SRR. The split-ring resonators and other structures are created on the membrane which is then assembled into the 3-D configuration.
Wireless-based Monitoring of Body Movements Using Wearable Sensors
Authors: Brady Sarah , Coyle Shirley , Wu Yanzhe , Wallace Gordon , Diamond Dermot
Published: April 2011

The world is becoming more health conscious and as a result healthcare is evolving in many ways. Wearable computing is assisting with this evolution, finding its place in many biomedical applications where real-time monitoring of general health indicators is required. However, the inconvenience of connecting sensors through wires, which not only incurs high maintenance, limits the freedom of the person therefore hampering a true reflection of the person's actions. By using sensors attached to wireless sensor nodes, this constraint is removed. Also in order to be “wearable” the sensors must be comfortable, a factor often overlooked by traditional sensors, where functionality and robustness are of higher importance. This work is focused on the use of foam-based pressure sensors and similar textile-based sensors for monitoring the ambulatory movements of the wearer. Characterization of the molecular nature of the materials and their environment are presented. We find these sensors to be successful in detecting the movement events without imposing on the daily activity of the wearer.
Prediction of Fiber Die Coating Thickness
Authors: Yang An , Tao XiaoMing , Chen XiaoYin
Published: April 2011

Fiber coating is an effective way to impart smartness to a fiber. Die coating is a process that utilizes a die to control the thickness and concentricity of the coating layer. In the present work the die coating mechanism is studied numerically. A mathematical model for the fiber coating thickness has been developed. Compared with the previous work, the proposed model considers the effect of gravity force to get the general solution. The shear rate acting on the fiber surface is proportional to the fiber draw speed in an unpressurized applicator and can be minimized in a pressurized applicator through the applied external pressure. A serials of experiments using open-cup and pressurized applicators have been designed and conducted to measure simultaneously the coating speed and coating thickness in the coating process. It was found that the gravity may be an important driving force for the coating flow when the drawing velocity is small and the viscous force decreases, but may be relatively insignificant for high speed coating process. The calculated results were compared with the experimental data and a good agreement was obtained.
Self-cleaning Cotton Fabrics
Authors: Qi Kaihong , Daoud Walid A , Xin John , Mak C.L.
Published: April 2011

Nanocrystalline anatase titanium dioxide films were successfully produced on cotton fabrics from alkoxide solutions under ambient pressure using the low temperature sol-gel process. At a temperature as low as 40°C, only anatase phase formed from X-ray diffraction spectroscopy (XRD). Field scanning electron microscopy (FESEM) images show the formation of uniform continuous films of titanium dioxide on cotton fabrics. The self-cleaning properties of these fabrics were evaluated by measuring anti-bacterial activities and the decomposition of a colorant Neolan Blue 2G. The results indicated that anatase treated cotton fabrics exhibited good self-cleaning performance.
Synthesis and Electrochemical Properties of InVO4 Nanotube Arrays
Authors: Wang Ying , Cao Guozhong
Published: April 2011

A capillary-enforced template-based method is described for the preparation of InVO4 nanotube arrays. Nanotube arrays of InVO4 were prepared by filling the InVO4 sol into pores of polycarbonate membranes and pyrolyzing through sintering. Another type of InVO4 nanotube arrays (InVO4/acac) are obtained from the sol with the addition of acetylene acetone (acac). For comparison purposes, InVO4 films were prepared by drop casting from InVO4 same sol. Films and the two types of nanotube arrays of InVO4 annealed at 500°C consist of mixed monoclinic (InVO4-I) and orthorhombic (InVO4-III) phases. Scanning electron microscopy (SEM) characterizations indicate that the nanotubes are well-aligned, perpendicular to substrate surface with the outer diameter of ~200 nm for short InVO4 nanotubes and ~170 nm for long InVO4 nanotubes. Chronopotentiometry results reveal that InVO4/acac nanotube array has the highest charge capacity (790 mAh/g), followed by InVO4 nanotube array (600 mAh/g) then InVO4 film (290 mAh/g). Such enhanced lithium-ion intercalation properties are ascribed to the large surface area and short diffusion distance offered by nanostructures and amorphisation caused by acetylene acetone in the case of InVO4/acac nanotube arrays.
Nanotubes in Low Temperature Spray Deposited Nanocrystalline HgSe: I thin films
Authors: Arnepalli Ranga Rao , Dutta Viresh
Published: April 2011

HgSe nanotubes have been prepared by spray deposition of solvothermally synthesized HgSe: Iodine nanoparticles on glass substrates at low temperature (200°C). Spray deposition was done without voltage and with an externally applied voltage (700V) to the nozzle and it is found from TEM studies that the average length of the nanotubes increases in case of the films deposited with applied voltage compared to that of without voltage. But there is no change in the average diameter (~ 35 nm). The nanotubes are found to have cubic crystal structure. Iodine is found to act as a catalyst and helps in the growth of nanotubes. The growth mechanism of the nanotubes is analogous to the well known solution-liquid-solid/vapor-liquid-solid (SLS/VLS) mechanism. The EDAX analysis of the tip of the nanotube reveals the presence of Hg, Se and Iodine in the ratio of 73:2:24 for the spot size of <1μm.