bluuebunny/crossref_metadata_2025 huggingface dataset:
FTIR Study of Porous Low Dielectric Constant SiOC Film under Various Post-Deposition Curing Conditions
Authors: Sardo Massimo D. , Lagha Anissa , Humbert Aurelie , Desbois Morgane , Laurent Nicolas
Published: November 2006

This paper presents the characterization done by FTIR method of a carbon-doped SiOC film deposited in a 300mm PECVD reactor, using the diethoxymethylsilane molecule as main precursor and other reactant gases, and then baked in a dedicated post- deposition treatment chamber, where the porosity creation is stimulated by a flow of electrons. The effects of tunable parameters in the post-deposition curing chamber to the absorbance peak and to the dielectric constant are presented. It was found that C-Hx group absorption peaks reveal a wavenumber shift following different curing conditions, along with the Si-(CH3)x absorption peak. Furthermore the primary effect of curing temperature on dielectric constant and the role played by additional parameters on the restrucuration process is presented. It is shown that some of the curing chamber parameters although affecting greatly the Si-(CH3)x and H-Si-O absorption peaks associated to cross-linking processes, do not cause a relevant variation in the dielectric constant
Significance of Nitrogen and Aluminum Depth Profile Control in HfAlON Gate Insulators
Authors: Ota Hiroyuki , Ogawa Arito , Kadoshima Masaru , Iwamoto Kunihiko , Okada Kenji , Satake Hideki , Nabatame Toshihide , Toriumi Akira
Published: November 2006

Aluminum and nitrogen depth-profile dependences of the electron mobility are examined. We show that the electron mobility for MOSFETs with HfAlON gate dielectrics in which nitrogen and aluminum depth profiles are controlled is strongly affected by the nitrogen profile rather than the aluminum one, although the nitrogen profile does not affect the VFB shift. These results suggest that additional scattering due to nitrogen incorporation cannot be explained by only the Coulombic components such as the fixed charges. Thus, an appropriate profile control of the nitrogen to suppress the mobility degradation is a key for obtaining high performance MOSFETs with HfAlON dielectrics.
Impact of Dielectric Material Selection on Electrical Characteristics of High-k/Ge Devices
Authors: Kita Koji , Nomura Hideyuki , Nishimura Tomonori , Toriumi Akira
Published: November 2006

The impact of high-k material selection on the electrical characteristics of high-k/Ge MIS capacitors is investigated. The Y2O3/Ge can maintain good electrical characteristics even after annealing at 600{degree sign}C, while HfO2/Ge seriously degrades. The Ge diffusion into Y2O3 occurs during the annealing, but the characteristics of MIS capacitors do not change even by an intentional doping of Ge into high-k films. The Ge substrate quality is not significantly affected by metal diffusion, neither. These results clearly show that the critical difference between HfO2/Ge and Y2O3/Ge systems is, the ability to form a high quality interface through interface reaction.
Thermal Stability of Stack Structures of Aluminum Nitride and Lanthanum Oxide Thin Films
Authors: Eom Dail , Hwang Cheol Seong , Kim Hyeong Joon
Published: November 2006

Lanthanum oxide thin films were deposited using alternate injections of La(iPrCp)3 and H2O and Aluminum nitride films were deposited as capping layer and reaction barrier layer. The AlN reaction barrier layer was effective in increasing thermal stability of La2O3 films. However, it was found that Al atoms diffuse onto the film surface during annealing in La2O3/AlN/Si stacks and AlOx species in stacks seems to suppress the oxidizing gas diffusion to the interface. It appears that the behavior of Al and Si atoms in LaxAl(1-x) O3/Si system is very important in determining the electrical and structural properties of the film although the diffusion behaviors are not fully understood yet.
Physics of Metal/High-k Interfaces
Authors: Nakayama Takashi , Shiraishi Kenji , Miyazaki Seiichi , Akasaka Yasushi , Torii K. , Ahmet Parhat , Ohmori Kenji , Umezawa Naoto , Watanabe Heiji , Chikyow Toyohiro , Nara Yasuo , Ohta Akio , Iwai H. , Yamada Keisaku , Nakaoka Takashi
Published: November 2006

The conventional theory of work functions (Schottky barriers) does not work at pure-metal/high-k-dielectrics interfaces. This occurs due to the selective interface atom bonding reflecting the large ionicity of high-k materials and the characteristic density of p-metal electronic states. Taking into accounts these features, we have constructed a new theory of work functions based on a concept of generalized charge neutrality levels. This theory systematically explains work functions of various gate materials on high-k dielectrics, in particular the unusual behavior of p-metal work functions, and naturally reproduces band offsets at various semiconductor/semiconductor interfaces.
NBTI Effects in pMOSFETS with TiN/Hf-Silicate Based Gate Stacks
Authors: Chowdhury Naser A. , Misra D.
Published: November 2006

Effects of negative bias temperature instability (NBTI) on p-channel MOSFETS with TiN/HfSixOy (20% SiO2) based high-k gate stacks are studied under different gate bias and elevated temperature conditions. For low bias conditions, threshold voltage shift (Delta VT) is most probably due to the mixed degradation within the bulk high-k. For moderately high bias conditions, H-species dissociation in the presence of holes and subsequent diffusion may be initially responsible for interface state and positively charged bulk trap generation. Initial time, temperature and oxide electric field dependence of Delta VT in our devices conform to SiO2 based reaction-diffusion (R- D) model of NBTI. Under high bias condition at elevated temperatures higher Si-H bond-annealing/bond-breaking ratio, due to the experimentally observed absence of the impact ionization induced hot holes at the interracial layer (IL)/Si interface, probably limits the interface state generation and Delta VT as they quickly tend to saturate.
Charge Trapping Characteristics of W-La2O3-nSi MIS Capacitors After Post-Metallization Annealing PMA in N2
Authors: Molina Joel , Tachi Kiichi , Kakushima Kuniyuki , Ahmet Parhat , Tsutsui Kazuo , Sugii Nobuyuki , Hattori Takeo , Hiroshi Iwai
Published: November 2006

In this paper, we report the effects of a N2-based Post- Metallization Annealing (PMA) thermal process on the reliability and charge trapping characteristics of tungsten- gated La2O3 thin films. The samples are stressed with a Constant Voltage Stress (CVS) under substrate injection so that electrons from the substrate are injected and trapped into localized states within the dielectric. Post-stress measurements of the flat band voltage Vfb of the samples have shown a positive shift indicating a net negative charge trapping effect within La2O3 and its interfaces. PMA samples have shown less Vfb shift after stress as compared to La2O3 films annealed before the gate metallization step. Moreover, relatively higher PMA temperatures will produce the higher endurance to Vfb shift while the Equivalent Oxide Thickness (EOT) of the MIS capacitors is compromised thus the necessity of a trade-off between less Vfb shift and low EOT is required.
Polaron-like Charge Trapping in Oxygen Deficient and Disordered HfO2: Theoretical Insight
Authors: Gavartin Jacob L. , Munoz Ramo David , Shluger Alexander , Bersuker Gennadi
Published: November 2006

We suggest that the polaronic trapping of electrons is possible in the high-k dielectrics alongside with the commonly discussed Poole-Frankel resonant tunneling process or recapture of the electrons from the conduction band onto pre- existed defect states. The main feature of this mechanism is the charge self-trapping, i.e. formation of a localized defect state as a result of the electron-lattice interaction. We consider the charge trapping properties of single oxygen vacancies and di-vacancies in the m-HfO2 as well as the various models for oxygen deficient and stoichiometric disordered hafnia. We find evidence of polaronic trapping in all these systems, which may indicate its universality in high- k materials.
Numerical Analysis of Gate Stacks
Authors: Karner Markus , Holzer Stefan , Vasicek Martin , Goes Wolfgang , Wagner Martin , Kosina Hans , Selberherr Siegfried
Published: November 2006

An efficient software tool for investigations on novel stacked gate dielectrics with emphasis on reliability has been developed. The accumulation, depletion, and inversion of carriers in MOS capacitors is properly considered for n- and p-substrates. The effect of carrier quantization on the electrostatics and the leakage current is included by treating carriers in quasi-bound states (QBS) and continuum states. The effect of interface traps and bulk traps in arbitrarily stacked gate dielectrics is taken into account. Trap assisted tunneling (TAT) is incorporated assuming an inelastic single step tunneling process. A brief overview of implemented models is given. The capabilities of our tool are demonstrated by several examples.
Alternative Gate Dielectric Materials
Authors: Van Elshocht Sven , Hardy An , De Gendt S. , Adelmann Christophe , Baumann Peter K. , Brunco David P. , Caymax Matty R. , Conard Thierry , Delugas Pietro , Lehnen Peer , Richard Olivier , Rohr Erika , Shamiryan Denis , Vos Rita , Witters Thomas , Zimmerman Paul , Van Bael Marlies K. , Mullens Jules , Meuris Marc M. , Heyns Marc M.
Published: November 2006

Alternative high-k materials are being researched as a replacement for SiON. At present HfSiON is the most popular material because of good transistor performance. Still, issues such as threshold voltage control and a limited k-value improvement encourage continuing material screening. In this paper, we give a short overview of some of the work done in this field, where we focus on DyxSc2-xO3 as potential candidate. In addition, we discuss the use of the aqueous chemical solution-gel deposition technique as potential technique to facilitate high-k screening.
Laminated CeO2/HfO2 High-K Gate Dielectrics Grown by Pulsed Laser Deposition in Reducing Ambient
Authors: Karakaya Koray , Barcones Beatriz , Zinine Andrei , Rittersma Chris , Graat Peter , van Berkum Jurgen , Verheijen Marcel , Rijnders Guus , Blank Dave
Published: November 2006

CeO2 and HfO2 dielectric layers were deposited in an Ar+(5%)H2 gas mixture by Pulsed Laser Deposition (PLD) on Si (100). A CeO2-Ce2O3 transformation is achieved by deposition in reducing ambient. It is also shown that in-situ post deposition anneal efficiently oxidizes Ce2O3 layers to CeO2. The properties of CeO2/HfO2 laminated structures deposited in reducing ambient are compared with binary oxide layers of CeO2 and HfO2. The effect of the layer sequence, individual layer thickness and deposition temperature on the properties of the laminates were investigated. It is found that the layer sequence affects the crystallinity of the laminates and changes their electrical properties. The amorphous laminate with a CeO2 starting layer with 4 nm physical thickness and an EOT of 2 nm, has the lowest J@Vfb 1V=1.88x10-7 A/cm2. The best EOT Jg trade off is achieved by the laminated layers with a CeO2 starting layer deposited at 520{degree sign}C
Melt Flow Simulations of Czochralski Crystal Growth Process of Silicon for Large Crystals
Authors: Gunjal Prashant R. , Kulkarni Milind S. , Ramachandran Palghat A.
Published: November 2006

Czochralski Growth of Silicon Crystal (Cz) is extensively used for single crystal manufacturing and most of the Silicon wafers are manufactured by this process. Melt flow in large crucibles, used for growth of large diameter (300mm) crystal, is turbulent in nature. In this study, we present a model for simulating Czochralski crystal growth process for 300mm crystal. This study is mainly focused on effect of crucible rotation on flow and temperature profiles in the melt. Two-dimensional axisymmetric model was used for this purpose which accounts for generated turbulence, heat/ mass transfer with phase change. Investigations show that flow pattern in co-rotation below the crystal is totally opposite that of counter-rotation. Centrifugal force is dominant due to crystal and crucible rotation, which creates vertical upwards or downward flow below the crystal, depending upon the co-rotation or counter rotation. With increase in pull rate, depth of the predicted interface in the melt was also found to be increased. Simulated results will be helpful for optimization of process parameters to achieve better quality of crystals.
Nitrogen Diffusion in Silicon: a Multi-Species Process
Authors: Voronkov Vladimir V. , Falster R. J.
Published: November 2006

Out-diffusion profiles of nitrogen produced by annealing at 900oC show that there are at least two independent nitrogen components which we label A and B. The A-component - dominant at higher nitrogen concentration - can be attributed to the interstitial dimeric species N2 that are transported by a dissociation mechanism through minor mobile monomers N1. The B- component can be attributed to the presence of substitutional nitrogen species VN. At lower temperature, these species attach N2 dimers and thus partially convert into VN3. A central point of the model is that the out-diffused nitrogen is collected into near-surface precipitates that emit self-interstitials. The self-intestitials in-diffuse and convert the VN3 species into highly mobile interstitial trimers N3. In this way the substitutional subsystem is fast removed from a near-surface region and remains only deeper in the bulk, creating a peculiar step-wise depth profile.
Hydrogen Gettering and Platelet Formation in Implanted and Hydrogenated Silicon
Authors: Job Reinhart , Düngen Wolfgang , Ma Yue , Fahrner Wolfgang R. , Keller Lars O. , Horstmann John T. , Fiedler Horst
Published: November 2006

The trapping of hydrogen in crystalline silicon at a buried defect layer has been investigated by Raman scattering spectroscopy. The defect concentration of the trap layer was created by various implantation doses of hydrogen ions. Hydrogen was additionally inserted by subsequent plasma exposure at various temperatures. The basic platelet formation and hydrogen trapping mechanisms are investigated with regard to the use for hydrogen induced silicon layer exfoliation. The analyzed results exhibit that the platelet formation mechanism highly depends on the hydrogenation temperature and on the vacancy concentration.
Precise Control of Annealed Wafer For Nanometer Devices
Authors: Matsushita Yoshiaki , Nagahama Hiromi , Takeda Ryuji , Hirasawa Manabu
Published: November 2006

In the nanometer device era, surface morphology of atomic level becomes one of critical issues for device performance. The surface morphology of atomic level was evaluated in various wafer types and surface indexes. It was found that a hydrogen anneal wafer has the largest terrace comparing to other wafers. It is possible to control the terrace width by adjusting the off angle and azimuth. The channel area of the device has atomically flat or only one step with mono-atomic height by using the hydrogen-annealed wafer.
Effects of Annealing on the Electrical Properties of Nitrogen-Doped Float-Zoned Silicon
Authors: Voronkov Vladimir V. , Voronkova Galina , Batunina Anna , Falster R. J. , Moiraghi Luca , Milvidski Mikhail
Published: November 2006

The nitrogen impurity, in nitrogen-doped Float-Zone (FZ) silicon, is known to show no electrical activity in as-grown state, but to produce deep centers after annealing at relatively high temperatures like 900 or 1000{degree sign}C. In the present work it was found that in FZ samples of relatively high initial resistivity (greater than 1000 Ohm.cm, p- and n- type) the generation of deep centers is well pronounced after annealing at a lower temperature (680{degree sign}C). In p-type samples, deep donors are produced, and the material is converted into n-type of an extremely high-resistivity. Another striking feature of this material is an extremely low apparent Hall mobility indicating to a well-pronounced non-uniformity in the carrier distribution. In n-type samples, deep acceptors are generated. The deep center concentration is on the order of 2x1013 cm-3. A possible identification of the deep centers is substitutional nitrogen.
Some Recent Advances in Contactless Silicon Characterization
Authors: Schroder Dieter
Published: November 2006

Contactless measurements are attractive because they do not contaminate the sample and generally do not require extensive sample preparation. It is for these reasons that they are more commonly used. We will discuss mainly methods for material but some for device characterization and point out the advantages of these methods and also indicate their short-comings.
Comparative Study of Carrier Lifetime Variations with Doping in Si and Ge
Authors: Vanhellemont Jan , Gaubas Eugenijus
Published: November 2006

The joint application of Si and Ge in advanced devices is the motivation for a comparative study of the dependence of recombination characteristics on excitation and doping density. Carrier lifetimes measured at high and low excitation levels are compared with simulations varying the excitation level. The Shockley-Read-Hall (SRH) model was combined with Auger recombination above a doping concentration threshold to simulate the observations. The dependence of carrier lifetime on dopant concentration and excitation level shows a very similar behaviour in Si and Ge and can explained well by a combined SRH and Auger recombination model.
Observation of Vacancy in High Purity Silicon Crystal Using Low-Temperature Ultrasonic Measurements
Authors: Goto Terutaka , Yamada-Kaneta Hiroshi , Saito Yasuhiro , Nemoto Yuichi , Sato Koji , Kakimoto Koichi , Nakamura Shintaro
Published: November 2006

We have succeeded in direct observation of isolated vacancies in high purity silicon crystals grown by a floating zone (FZ) method using low-temperature ultrasonic measurements. The softening of elastic constants below 20 K down to 20 mK is observed in non-doped FZ silicon and B-doped FZ silicon. This softening is caused by an interaction of electric quadrupoles of triply degenerate vacancy orbital to elastic strains of ultrasonic waves. The low-temperature elastic softening measured by ultrasonic methods verifies existence of the isolated vacancies in Pv-region distributed in pure crystal of a Czockralski ingot. The ultrasonic measurement of the low- temperature softening is a faithful probe for vacancy evaluation in high purity silicon crystals in commercial base.
Brother Silicon, Sister Germanium
Authors: Vanhellemont Jan , Simoen Eddy R.
Published: November 2006

Material and lattice defect properties of silicon and germanium relevant for device processing are discussed and compared. It is shown that both semiconductors are very similar when comparing their material properties at the same temperature T normalized to the melt temperature Tm. In other respects, however, like the diffusion of dopants, Ge behaves quite differently.
Channel Material Innovations for Continuing the Historical MOSFET Performance Increase with Scaling
Authors: Antoniadis Dimitri A. , Khakifirooz Ali , Aberg Ingvar , Hoyt Judy L.
Published: November 2006

A simple model is developed which relates the intrinsic transistor delay to the key technological parameters and the effective carrier velocity in the channel. Nearly continuous increase in the velocity, first as a direct result of scaling and most recently through the introduction of the process-induced strain, is shown to be responsible for device performance increase. Furthermore the carrier velocity is shown to be correlated with the effective mobility in the channel by examining the most recent results of strain engineering. We further review channel material innovations that will be required in order to maintain continued commensurate scaling beyond what can be achieved with process-induced strain and discuss some of the technological challenges that should be addressed for their introduction.
Low-Field Electron Mobility in Stressed UTB SOI MOSFETs for Different Substrate Orientations
Authors: Ungersboeck Enzo , Sverdlov Viktor , Kosina Hans , Selberherr Siegfried
Published: November 2006

In this work stress induced electron mobility enhancement in bulk Si, inversion layers formed on (001) and (110) substrate orientations, and UTB MOSFETs is modeled using the Monte Carlo method. Uniaxial stress effects on the bulk band structure are incorporated by adapting the non-local empirical pseudopotential method with spin-orbit interaction for arbitrary strain conditions. Stress induced change of the electron effective mass is found to be very important to enhance mobility in UTB MOSFETs. Simulation results of electron mobility are compared to experimental data and good qualitative agreement is found.
The Utility of Novel Single-Source Germyl Silanes
Authors: Stephens Matthew D. , Pikulin Michael , Ritter Cole
Published: November 2006

A new family of molecules developed by J. Kouvetakis, et al. (1,2) at Arizona State University enables low temperature deposition of SiGe films having Ge contents {greater than or equal to} 50%. This family includes germyl silane molecules ((H3Ge)xSiH4-x where x=(1-4) (1) and butane-like derivatives such as H3Ge(SiH2)2GeH3.(2) The composition of layers deposited from these precursors is highly uniform and matches the stoichiometry of the parent compound.(3) Voltaix has licensed the intellectual property rights to these molecules and is developing commercial applications. We review the deposition properties of these precursors and present information on their physical and chemical properties. We discuss their potential use in a variety of applications from strained silicon to CMOS- integrated MEMS. 1. C. J. Ritter, C.-W. Hu, A. V. G. Chizmeshya, J. Tolle, D. Klewer, I. S. T. Tsong, and J. Kouvetakis, J. Am. Chem. Soc., 2005, 127 (27), 9855-9864. 2. A.V. G. Chizmeshya, C. J. Ritter, C. Hu, J. B. Tice, J. Tolle, R. A. Nieman, I. S. T. Tsong, J. Kouvetakis, J. Am. Chem. Soc., 2006, 128 (21); 6919-6930.
Ge Epitaxy on (100) Ge: High Growth Rates at Low Temperature from GeH4 using N2 as a Carrier Gas
Authors: Leys Frederik , Bonzom Renaud , Loo Roger , Theuwis Antoon , Vandervorst Wilfried , Caymax Matty R.
Published: November 2006

The growth kinetics of Ge homo-epitaxy using GeH4 is investigated as a function of carrier gas, comparing H2 to N2. Using N2, the mass-flow controlled regime is shown to extend to much lower temperatures, yielding a significantly enhanced growth rate compared to H2 between 500 and 400ºC.
Improvement of Dopant Concentration Control with Acoustic Control System for B-SiGe Epitaxy Deposition
Authors: Woods Terry , Zhou Yiyang , Dominguez Selene D. , Carey Raymond D.
Published: November 2006

Currently, SiGe-B epitaxy is a leading technology to induce strain in PMOS channel and improve the hole mobility to achieve better device performance [1-2]. In practice, we observe that the device performance strongly depends on the dopant concentration, especially boron concentration. It is shown that the Acoustic Control System [ACS] is able to actively respond to instantaneous variations of incoming gas and achieve better dopant control [3]. In this paper, we report reduction of boron concentration variation using ACS technology for SiGe-B epitaxy.
Electrical Properties and Bonding Structures of Germanium Nitride/Ge(100) Structures Formed by Radical Nitridation
Authors: Kondo Hiroki , Yanagi Itaru , Sakashita Mitsuo , Sakai Akira , Ogawa Masaki , Zaima Shigeaki
Published: November 2006

Metal-oxide-semiconductor field-effect-transistor (MOSFET) with germanium (Ge) channel draws much attention as a probable candidate of next-generation high-mobility devices in recent years. However, it is a serious and essential issue that there is much interface state density (Dit) between germanium dioxide (GeO2) and Ge. Additionally, as is well known, GeO2 is water-soluble so that it is hard to perform conventional ULSI processes to GeO2/Ge stacked structures. Therefore, a stable gate dielectric film on the Ge surface, like silicon dioxide (SiO2) on a silicon (Si) surface, is required. Ge nitride (Ge3N4) is an interesting candidate, which is water-insoluble, and Dit at Ge3N4/Ge interface might be sufficiently low. However, electrical properties of Ge3N4, such as Dit against Ge surface and energy band diagram, are not clear yet. In this study, performing a radical nitridation of amorphous Si (a-Si)/Ge structures, Si nitride/Ge nitride/Ge stacked structures were formed.
Structural Properties of Tensile-Strained Si Layers Grown on Si0.6Ge0.4 and Si0.5Ge0.5 Virtual Substrates
Authors: Hartmann Jean-Michel , Abbadie Alexandra , Rouchon Denis , Guinche Y. , Holliger Phillipe , Rolland Guy , Buisson M. , Mermoux Michel , Brunier F. , Defranoux C. , Pierrel F. , Billon Thierry
Published: November 2006

We have studied the structural properties of tensile strained Si (sSi) layers grown on polished Si0.6Ge0.4 and Si0.5Ge0.5 virtual substrates as a function of their thickness. The surface morphology, the tensile strain, the linear density of defects, and the threading dislocation density have been quantified for different growth conditions and sSi layer thickness.
Prospects for Complementary SiGeC BiCMOS on Thin-Film SOI
Authors: Chantre Alain , Avenier Gregory , Boissonnet Laurence , Borot Gael , Bouillon Pierre , Brossard Florence , Chevalier Pascal , Deleglise Florence , Dutartre Didier , Duvernay Julien , Fregonese Sebastien , Judong Fabienne , Pantel Roland , Perrotin Andre , Rauber Bruno , Rubaldo Laurent , Saguin Fabienne , Schwartzmann Thierry , Vandelle Benoit , Zimmer Thomas
Published: November 2006

This paper reviews the concept, manufacturing process and electrical characteristics of a novel self-aligned SiGeC HBT structure suitable for thin-film SOI substrates. It then describes the integration of this device into 130nm SOI CMOS technology, and presents early results on the development of a complementary pnp HBT.
Facet Propagation in Si and SiGe Epitaxy or Etching
Authors: Dutartre Didier , Talbot Alexandre , Loubet Nicolas
Published: November 2006

The facets propagation during silicon and SiGe epitaxial growth has been studied in terms of morphology and kinetics. In a similar way the faceting effects during chemical etching of monocrystalline silicon have been examined. In both cases, the appearance of certain facets in certain experimental conditions have been explained on the basis of activation energies of the growth kinetics of the main high density crystal planes.
Interface Layers for High-k/Ge Gate Stacks: Are They Necessary?
Authors: McIntyre Paul , Chi David , Chui Chi On , Kim Hyoungsub , Seo Kang-Ill , Saraswat Krishna , Sreenivasan Raghavasimhan , Sugawara Takuya , Aguirre-Testado F. S. , Wallace Robert M.
Published: November 2006

We discuss the effects of interface layers between high-k gate insulators and the Ge substrate on the electrical characteristics of Ge MOS devices. Our work has focused on both germanium oxynitride (GeOxNy) and tantalum oxynitride (TaOxNy) interface layers. We find that ultrathin interface layers of TaOxNy, a high permittivity diffusion barrier, produce greatly improved charge trapping characteristics and promising capacitance scaling for high-k/Ge gate stacks. Effects of interface layers on interface state density and the frequency dispersion of the capacitance-voltage (CV) behavior under inversion are also described.
Low Temperature Crystallization of a-SiGe on Insulating Films for Thin Film Transistor Application
Authors: Miyao Masanobu , Kanno Hiroshi , Tsunoda Isao , Sadoh Taizoh
Published: November 2006

Development of high-mobility semiconductors is strongly needed to realize high-performance thin-film transistors. To achieve this, we have been investigating low temperature solid-phase crystallization and metal-induced lateral crystallization of a- SiGe on insulating substrates. These realize uniform crystal growth of SiGe with all Ge fractions. In addition, thin-film transistors with Schottky source and drain structures were fabricated, which showed good ambipolar operation characteristics. Present paper reviews such our recent progress of low temperature SiGe growth and discusses the possible application to thin-film transistors with high speed operation.
Nickel Selective Etching Studies for Self-Aligned Silicide Process in Ge and SiGe-Based Devices
Authors: Carron Veronique , Ribeiro Mathilde , Besson Pascal , Rolland Guy , Hartmann Jean-Michel , Loup Virginie , Minoret Stephane , Clavelier Laurent , Leroyer Cyrille , Billon Thierry
Published: November 2006

The limitations of the H2SO4/H2O2/H2O mixture (diluted SPM chemistry) as a reagent for the nickel selective etching step of the salicidation process when silicon is replaced by silicon- germanium alloys or pure germanium is investigated. When the Ge content in SiGe is higher than 30%, SPM is not suitable anymore due to the high etch rate of the germanosilicide layer. This high etch rate is related to the poor stability of the Ge oxide in aqueous solutions. For Ge contents above 30%, H2SO4 96% is proposed as a selective etching reagent instead of SPM. With this chemistry, a very high Ni/NiSiGe selectivity and a good Ni/NiGe selectivity are obtained, since only 10% of the germanide layer is attacked while the Ni layer is completely removed.
III-V Device Integration on Silicon Via Metamorphic SiGe Substrates
Authors: Carlin John A. , Andre Carrie , Kwon Ojin , Gonzalez Maria , Lueck Matt , Fitzgerald Eugene , Wilt David , Ringel Steven
Published: November 2006

A range of high performance minority carrier devices have been successfully fabricated on Si virtual substrates where threading dislocation densities (TDDs) as low as 1x106 cm-2 are routinely achieved. Minority carrier lifetime data achieved on GaAs-on-Si layers exploiting this novel SiGe buffer approach to monolithic integration (τp = 10.5 ns and τn = 1.7ns) verifies the high III-V material quality. Single junction GaAs solar cells with high efficiencies for GaAs/Si of 18.1% under AM1.5-G illumination were demonstrated. Further exploiting the novel GaAs/Si material quality, even more complex minority carrier devices including dual-junction solar cells and LEDs were fabricated, yielding high performance consistent with the high III-V/Si mobilities. In both cases, certain device metrics on SiGe outperformed identical GaAs monolithic devices. Finally, a visible laser on Si was achieved, demonstrating the success and further potential of this III-V/Si integration methodology.
Review of Some Critical Aspects of Ge and GeOI Substrates
Authors: Clavelier Laurent , Le Royer Cyrille , Morand Yves , Deguet Chrystel , Vincent B. , Damlencourt Jean-François , Hartmann Jean-Michel , Kermarrec O. , Signamarcheix T. , Depuydt B. , Theuwis Antoon , Quaeyhaegens C. , Cherkashin N. , Rivallin P. , Tabone Claude , Lagrasta S. , Campidelli Y. , Descombes S. , Sanchez L. , Akastu T. , Rigny A. , Bensahel D. , Billon Thierry , Kernevez Nelly , Deleonibus Simon
Published: November 2006

The challenges posed by the scaling of Silicon (Si) devices make mandatory the study of new materials to overcome the physical limitations of the Si. Germanium (Ge) was actually used in the first transistors but was then abandoned in favour of Si due to difficulties in processing Ge Oxide. However, the introduction of high-K gate dielectrics makes the use of Ge possible in an advanced technology. Its benefits for MOSFET applications are important: better transport properties than with Silicon hence higher saturation currents; lower band gap hence lower supply voltages and lower power dissipation and a lattice parameter compatible with Gallium Arsenide (GaAs) epitaxy. These are the main reasons why, during the last 4 years, the interest in Ge and Ge-On-Insulator (GeOI) substrates fabrication and properties has grown. This paper is a review of the different types of Ge and GeOI substrates, their critical aspects and their new potential applications.
Substrate Engineering for Germanium-Based CMOS Technology
Authors: Bedell Stephen W. , Fogel Keith , Reznicek A , Ott John , Sadana Devendra
Published: November 2006

Germanium has been proposed as a candidate channel material for high-performance IC devices. The most practical implementation of Ge will be to integrate the material into existing Si-based substrates. Silicon-germanium on insulator (SGOI) has the potential to serve as substrate that can bridge the misfit strain between Ge (or Ge-rich) channel layers for high-mobility pFET devices and strained Si nFET devices. The method of forming SGOI and GeOI using the thermal oxidation approach offers several advantages over competing methods such as wafer bonding. The formation of stacking faults (not oxidation induced) during the relaxation of high Ge content SGOI is suggested to be a significant limitation of this method. The process of SGOI formed by thermal oxidation and its possible use for Ge FET technology development will be critically reviewed.
Germanium MOSFETs for Nanoelectronics
Authors: Saraswat Krishna
Published: November 2006

Ge is a promising channel material for nanoscale MOSFETs due to its high mobility, which translates into higher drive current and smaller gate delay. However, for Ge to become main-stream, surface passivation and heterogeneous integration of crystalline Ge layers on Si must be achieved. We have demonstrated growth of fully-relaxed smooth single crystal Ge layers on Si using a novel multi-step growth and hydrogen anneal process without any graded buffer SiGe layer. Surface passivation of Ge has been achieved with its native oxynitride and high-k metal oxides of Al, Zr and Hf. High mobility p-MOSFETs have been demonstrated in bulk Ge with these gate dielectrics and metal gates. However, due to its smaller bandgap Ge suffers from large leakage currents. We present novel, Si and Ge based heterostructure MOSFETs, which significantly reduce the leakage while retaining high mobility, making them suitable for scaling into the sub-20nm regime.
Bandgap Engineering in SiGe:C HBTs For Power Amplifier Applications
Authors: Jouan Sebastien , Talbot Alexandre , Haendler Sebastien , Mans Pierre-Marie , Perrotin Andre , Monroy Augustin
Published: November 2006

Since the introduction of Germanium in Silicon Bipolar transistors, and more recently the introduction of Carbon, the base bandgap of SiGe:C heterojunction Bipolar transistors have been engineered to enhance device performance, thereby making them suitable for a wide range of high speed analog and RF applications
Nanoscaled MOSFET Transistors on Strained Si, SiGe, Ge Layers: Some Integration and Electrical Properties Features
Authors: Ernst Thomas P. , Andrieu Francois , Weber O , Hartmann Jean-Michel , Dupre C , Faynot O , Barbe J-C , Eymery Joel , Barraud S , Ducroquet Frédérique , Ghibaudo G , Deleonibus Simon
Published: November 2006

We have studied the integration process and the electrical properties of TiN/metal gate transistors with high k dielectrics for various strained substrates: Strained SOI, Strained SiGeOI, and Strained Ge. Substrate approaches enable (i)higher strain levels (additive with process induced strain), (ii)the co-integration of opposite strained layers for nMOS and PMOS, (iii)VT engineering for metal gates. Those features make the substrate approach a very promising solution for ultimate CMOS integration.
Buried-Channel Field Effect Transistors of Triple SiGe Quantum Wells on SOI
Authors: Fujinaga Kiyohisa
Published: November 2006

This report described the electrical characteristics of triple SiGe quantum wells channel pMOSFETs on SIMOX substrate. The two sorts of the transistors were fabricated and compared with the single SiGe quantum well channel pMOSFETs.
Ge Condensation Technologies for Advanced MOSFETs on SGOI and GOI Substrates
Authors: Sugiyama Naoharu , Tezuka Tsutomu , Irisawa Toshifumi , Usuda Koji , Moriyama Yoshihiko , Nakaharai Shu , Hirashita Norio , Takagi Shin-Ichi
Published: November 2006

Recent developments in the Ge condensation technique for the fabrication of the SiGe on insulator (SGOI) structures, which are the basic templates for the strained channel MOSFET's, and the further extensions to the SGOI formation on (110) substrates and the Ge on insulator (GOI) formation are reviewed in this paper. The detail analyses of the phenomenon during the initial stage in the Ge condensation process, in which the fragments of the misfit dislocations, that are formed at the SiGe / SOI interface, rise up resulting the generation of the threading dislocations are quite important, and the controlling of the understood phenomenon by the modification of the condensation recipe brings the successful fabrication of the high quality SGOI substrates with low dislocation density.
Characterization of Ge Implanted with Ni and Hf Ions
Authors: Sioncke Sonja , Simoen Eddy R. , Janssens Tom , Meuris Marc M. , Mertens Paul W. , Forment Stefaan , Clauws Paul , Theuwis Antoon
Published: November 2006

In this paper, we report the results of a study aimed at assessing the influence of Hf and Ni contamination on the electrical properties of Ge. Hf and Ni were implanted in n-type Ge wafers that were subsequently annealed and characterized by several techniques (SIMS, ToFSIMS, TEM, DLTS, MCLT). It is shown that the minority carrier lifetime is drastically reduced by Ni contamination. Also, the presence of Hf introduces deep levels. However, we cannot assign the reduction in minority carrier lifetime unambiguously to the Hf contamination due to contamination issues during the annealing step.
Integration of SiGe to MEMS applications
Authors: Reiche Manfred
Published: November 2006

SiGe offers new advantages in MEMS technologies. The excellent electronic and optoelectronic properties of SiGe alloys are of main interest for MEMS and NEMS. SiGe combines the electronic properties of Si and Ge having different band structures. Bandgap engineering allows the realization of different electronic and optical properties depending on the composition of the alloy and on the strain in the layer. This gives the opportunity to create new components and microsystems using a silicon-based technology and to replace III-V compound materials. Depending on the growth of SiGe layers tensile or compressive stress is caused in the layers making it possible to create prestressed or deformable elements. Strain engineering allows the realization of numerous microsystems. Combining, for instance, thin SiGe and Si layers result in deformable structures used as nanometer-range building blocks for future electronic and mechanical nanodevices.
Halide Passivation of Germanium Nanowires
Authors: Jagannathan Hemanth , Kim Jungyup , Deal Michael , Kelly Michael , Nishi Yoshio
Published: November 2006

A study on the passivation of germanium nanowires with aqueous halide solutions is presented. Germanium nanowires grown on silicon (100) substrates were treated with either hydrofluoric, hydrochloric, hydrobromic or hydroiodic acid (each of 20 wt %) and were analyzed using x-ray photoelectron spectroscopy after varying exposures to ambient air. Samples exposed to air for 10 minutes after hydrofluoric acid passivation show signs of oxidation while hydrochloric acid passivation results in mild oxidation after 3 hours. The hydrobromic and hydroiodic acid passivations produce stable and oxidation resistant nanowires up to 48 hours in room air. In addition to superior passivation, hydrobromic acid does not aggressively etch germanium compared to hydroiodic acid which etches germanium (100) at a rate of 0.6 nm/min. These results provide insight for obtaining proper passivation techniques that are required for the controlled fabrication of germanium devices.
Study of the Surface Cleaning of GOI and SGOI Substrates for Ge Epitaxial Growth
Authors: Moriyama Yoshihiko , Hirashita Norio , Toyoda Eiji , Usuda Koji , Nakaharai Shu , Sugiyama Naoharu , Takagi Shin-Ichi
Published: November 2006

An effective wet cleaning process, optimized for low temperature Ge epitaxy on thin Ge or SiGe structures with reduced surface roughening, is proposed. It is found that the HF+HCl cleaning is the most effective wet cleaning method that is applicable to the low temperature thermal cleaning. It is also found that temperature of the thermal cleaning appropriate for thin Germanium on Insulator (GOI) substrates is approximately 450ºC. Moreover, the successful formation of the strained-GOI structures is demonstrated by applying these wet and thermal cleaning processes to thin Silicon-Germanium on Insulator (SGOI) substrates.
Comparison of Electrical and Structural Properties of HfO2 Thin Films on Strained and Relaxed Si1-xGex
Authors: Park Tae Joo , Kim Jeonghwan , Hwang Cheol Seong
Published: November 2006

The changes in the electrical and physical properties of HfO2films grown using atomic layer deposition (ALD) on strained and relaxed Si1-xGex (x=0.1, 0.2, 0.3) substrates after post-annealing have been studied. The Ge atoms which have already diffused into the HfO2 upper layer during deposition are drawn back to interfacial layer and substrate. This migration of Ge plays a key role in reducing the capacitance equivalent thickness (CET) competing with additional interfacial oxidation of substrate and Si diffusion. The larger amount of Ge diffusion for HfO2 grown on relaxed Si1-xGex results in further reduction of CET. This was expected to occur by the bonding nature of Si-Ge under different stress circumstances.
Toward the Realization of Sustainable Mobility - Grand Design for an Advanced Transportation Society
Authors: Watanabe Hiroyuki
Published: November 2006

The circumstance in which automobiles are made and used faces daunting issues related to safety, air pollution, energy and climate. In an effort to address these issues on an industry- wide basis, the world's eight leading automobile manufacturers, through the World Business Council for Sustainable Development (WBCSD), have commonly identified seven goals necessary for ensuring sustainable development. Among these, the issue of global warming is both critical and complex. This paper provides an overview of the issues and challenges to be overcome in internal combustion engine with hybrid technology, and fuel cell (FC) technology. A new definition of vehicle efficiency is then suggested, and used as a basis for a discussion of future mobility technology and societal issues that must be addressed.
Highly Durable MEA for PEMFC Under High Temperature and Low Humidity Conditions
Authors: Endoh Eiji
Published: November 2006

The world's first highly durable perfluorinated polymer based MEA for PEMFC, under high temperature and low humidity, has been developed. The newly developed MEA, which is composed of a new perfluorinated polymer composite (NPC), reduces the degradation rate to 1/100 - 1/1000 compared to the conventional MEA. The NPC MEA can be operated for more than 4000 hours at 120ºC and 50% relative humidity (RH).
Platinum and Mixed Platinum-Metal Monolayer Fuel Cell Electrocatalysts: Design, Activity and Long-term Performance Stability
Authors: Adzic Radoslav R. , Zhang Junliag , Shao Minhua , Sasaki Kotaro , Vukmirovic Miomir , Uribe Francisco A.
Published: November 2006

We have synthesized a new class of electrocatalysts for the oxygen reduction reaction, consisting of a monolayer of Pt or mixed monolayer of Pt and another late transition metal (Au, Pd, Ir, Ru, Rh, Re or Os) deposited on a Pd(111) single crystal or on carbon-supported Pd nanoparticles. Several of these electrocatalysts exhibited very high activity, amounting to 20-fold increase in a Pt mass activity, compared with conventional carbon supported-Pt electrocatalysts. The origin of this effect was identified through a combination of experimental methods, employing electrochemical techniques, x- ray absorption spectroscopy. In addition, we found that gold submonolayer clusters modified Pt or Pt/Pd catalysts have high activity and an exceptional stability against Pt dissolution under potential (0.6-1.1V) cycling regimes. These new electrocatalysts promise to alleviate some major problems of existing fuel cell technology by simultaneously decreasing materials cost and enhancing performance.
Simulating Nonuniform Properties in Polymer-Electrolyte Fuel Cells
Authors: Weber Adam Z. , Newman John
Published: November 2006

In this transaction, results from mathematical, pseudo 2-D simulations are shown for four different thickness distributions of both the membrane and cathode catalyst layer. The results and subsequent analysis clearly demonstrate that the position along the gas channel is more important than the local thickness variations, especially for the membrane.
Nafion®/TiO2 Composite Membranes for PEM Fuel Cells Operating at Elevated Temperature and Reduced Relative Humidity
Authors: Lvov Serguei , Chalkova Elena , Rybka Gregory , Fedkin Mark , Wesolowski David , Roelofs Mark
Published: November 2006

Our approach for elevating the operational temperature of PEM fuel cells above 100 oC is to use inorganic particles inside a composite membrane. Inorganic components tend to enhance water retention at elevated temperatures and can reduce undesirable crossover processes. In this study, we compared the properties of the Nafion®/TiO2 composite membranes fabricated from Nafion® polymers with different ion exchange capacity (IEC) - 0.91 meq/g and 1.08 meq/g. The main objective was to find a balance between the membrane IEC and the TiO2 content for optimal fuel cell performance. The membranes were tested for swelling, conductivity, and fuel cell performance under different relative humidity at 120 oC. The membranes with IEC of 1.08 meq/g demonstrated better transport properties and much higher performance in a PEMFC. However, excessive swelling of membranes with IEC of 1.08 meq/g caused instability in performance at high current densities and this can be detrimental to membrane durability.
Experimental Elucidation of Proton Conducting Mechanism in a Polymer Electrolyte Membrane of Fuel Cell by Nuclei Labeling MRI
Authors: Tsushima Shohji , Teranishi Kazuhiro , Hirai Shuichiro
Published: November 2006

Isotope labeling with deuterium (2D) supply to a polymer electrolyte fuel cell was applied to monitor 2D permeation process in accordance with proton conducting mechanism involved in the membrane by using magnetic resonance imaging (MRI) which detected hydrogen (1H). It was shown that MRI signal intensity decreased at the anode, which indicated Grotthuss mechanism plays a dominant roll in proton conducting process in the membrane.
Performance Enhancement of PVA/PAMPS Conducting Composites using High Molecular Weight PVA
Authors: Qiao Jinli , Ono Hiroyuki , Oishi Tsukasa , Okada Tatsuhiro
Published: November 2006

PVA/PAMPS proton conducting composites have been presented for low temperature DMFCs using high molecular weight PVA (HMw- PVA). By using high molecular weight PVA as polymer matrices, the membrane micro-phase structure is improved and this brings about a performance enhancement of the membrane such as low water uptake, high proton conductivity, low methanol permeability and excellent longevity towards the Fenton's reagent.
Nano-Structure Controlled Polymer Electrolyte Membranes for Fuel Cell Applications Prepared by Ion Beam Irradiation
Authors: Yamaki Tetsuya , Kozone Yuichi , Hiroki Akihiro , Asano Masaharu , Kubota Hitoshi , Yoshida Masaru
Published: November 2006

Fluoropolymer-based electrolyte membranes for fuel cells were prepared by using heavy ion beams from the cyclotron accelerator of the Takasaki Ion Accelerators for Advanced Radiation Application (TIARA), Japan Atomic Energy Agency (JAEA). The preparation method for these so-called nano-scale structure-controlled membranes involves (i) the swift heavy ion irradiation of polyvinylidene fluoride (PVDF) films and subsequent chemical etching to obtain cylindrical pores with a diameter of 100 nm, and (ii) the filling of proton-conducting polymer chains into the etched pores by gamma-ray-induced graft polymerization. The proton transport only in the thickness direction was observed for the resulting membranes with controlled ion exchange capacities, indicating the formation of one-dimensional straight proton-conducting pathways parallel to the ion-beam incident axis. The membranes exhibited a lower water uptake and reduced methanol permeability compared to commercially-available Nafion probably due to the restricted structures.