bluuebunny/crossref_metadata_2025 huggingface dataset:
Linker Insertion Mutations in the Herpes Simplex Virus Type 1 UL28 Gene: Effects on UL28 Interaction with UL15 and UL33 and Identification of a Second-Site Mutation in the UL15 Gene That Suppresses a Lethal UL28 Mutation
Authors: Jacobson Jennie G. , Yang Kui , Baines Joel D. , Homa Fred L.
Published: November 2006

The UL28 protein of herpes simplex virus type 1 (HSV-1) is one of seven viral proteins required for the cleavage and packaging of viral DNA. Previous results indicated that UL28 interacts with UL15 and UL33 to form a protein complex (terminase) that is presumed to cleave concatemeric DNA into genome lengths. In order to define the functional domains of UL28 that are important for DNA cleavage/packaging, we constructed a series of HSV-1 mutants with linker insertion and nonsense mutations in UL28. Insertions that blocked DNA cleavage and packaging were found to be located in two regions of UL28: the first between amino acids 200 to 400 and the second between amino acids 600 to 740. Insertions located in the N terminus or in a region located between amino acids 400 and 600 did not affect virus replication. Insertions in the carboxyl terminus of the UL28 protein were found to interfere with the interaction of UL28 with UL33. In contrast, all of the UL28 insertion mutants were found to interact with UL15 but the interaction was reduced with mutants that failed to react with UL33. Together, these observations were consistent with previous conclusions that UL15 and UL33 interact directly with UL28 but interact only indirectly with each other. Revertant viruses that formed plaques on Vero cells were detected for one of the lethal UL28 insertion mutants. DNA sequence analysis, in combination with genetic complementation assays, demonstrated that a second-site mutation in the UL15 gene restored the ability of the revertant to cleave and package viral DNA. The isolation of an intergenic suppressor mutant provides direct genetic evidence of an association between the UL28 and UL15 proteins and demonstrates that this association is essential for DNA cleavage and packaging.
Human Papillomavirus Type 5 E6 Oncoprotein Represses the Transforming Growth Factor β Signaling Pathway by Binding to SMAD3
Authors: Mendoza Jose-Andres , Jacob Yves , Cassonnet Patricia , Favre Michel
Published: November 2006

Mechanisms of cellular transformation associated with human papillomavirus type 5 (HPV5), which is responsible for skin carcinomas in epidermodysplasia verruciformis (EV) patients, are poorly understood. Using a yeast two-hybrid screening and molecular and cellular biology experiments, we found that HPV5 oncoprotein E6 interacts with SMAD3, a key component in the transforming growth factor β1 (TGF-β1) signaling pathway. HPV5 E6 inhibits SMAD3 transactivation by destabilizing the SMAD3/SMAD4 complex and inducing the degradation of both proteins. Interestingly, the E6 protein of nononcogenic EV HPV9 failed to interact with SMAD3, suggesting that downregulation of the TGF-β1 signaling pathway could be a determinant in HPV5 skin carcinogenesis.
Paleocene–Eocene high-grade metamorphism, anatexis, and deformation in the Thor–Odin dome, Monashee complex, southeastern British Columbia
Authors: Hinchey Alana M , Carr Sharon D , McNeill Paul D , Rayner Nicole
Published: November 2006

The Thor–Odin dome of the Monashee complex, in the southeastern Canadian Cordillera, comprises Paleoproterozoic basement gneiss with infolds of unconformably overlying rocks of a supracrustal cover sequence and is the deepest exposed structural level in the Omineca belt. Orthogneiss and paragneiss of the basement are migmatitic and contain ubiquitous stromatic leucosome and discrete phenocrystic and pegmatitic vein-type leucosome, which are all interpreted to have formed as a result of in situ melting. The stromatic leucosome is infolded with the country rock (F2), contains a weakly developed foliation, and has a biotite-rich melanosome. The phenocrystic and pegmatitic vein-type leucosome crosscut the stromatic leucosome and the transposition foliation (S2). Evidence to support an igneous and anatectic source for the leucosome includes (i) petrography, (ii) major and trace element chemistry, (iii) zircon morphology, and (iv) peak pressure–temperature (P–T) conditions. Sensitive high-resolution ion microprobe (SHRIMP) 206Pb/238U zircon dates range from ca. 56 to 54 Ma and are interpreted to represent the age of leucosome crystallization. Zircon commonly contains discrete ca. 2.6-1.8 Ga cores that are interpreted as detrital grains inherited from the host paragneiss. Anatexis was ongoing by ca. 56 Ma, as a result of regional prograde metamorphism, and was coincident, at least in part, with the formation of the penetrative S2 transposition foliation and large recumbent F2 tight to isoclinal folds. Anatexis continued during F3 and F4 folding. Melting may have continued until ca. 51 Ma, driven by decompression reactions, and was concomitant with the D5 extensional deformation.
Locomotion in derived dicynodonts (Synapsida, Anomodontia): a functional analysis of the pelvic girdle and hind limb ofTetragonias njalilus
Authors: Fröbisch Jörg
Published: November 2006

A general locomotor model for derived dicynodont anomodonts is proposed on the basis of a functional analysis of the pelvic girdle and entire hind limb of the medium-sized Middle Triassic dicynodont Tetragonias njalilus. The joint mobility of the hind limb is examined, and a hind limb step cycle is reconstructed. The data provided in this case study indicate that Tetragonias adopted a highly adducted (upright) hind limb posture during stance and most of its stride. Nevertheless, lateral undulation of the vertebral column must also have contributed to the locomotion of dicynodonts. Character optimization of the traits associated with an upright posture of the hind limb shows a gradual evolution of dicynodont locomotion. The evolution of an upright hind limb posture has occurred several times independently in a number of amniote clades. Within synapsids, the Anomodontia, Dinocephalia, and Theriodontia acquired a parasagittal hind limb gait already as early as the late Paleozoic and early Mesozoic, prior to its evolution in mammals. This phenomenon has previously been explained as being related to an increase in body size as a response to increased biomechanical stress on the limb. This scenario appears plausible with respect to dicynodonts because of the occurrence of megaherbivore-sized taxa in the Triassic, but this study shows that a parasagittal gait had already evolved in the medium-sized basal kannemeyeriiform Tetragonias. Therefore, the vertical support of the body by the hind limbs in medium-sized dicynodonts could have allowed the evolution of the large Triassic taxa in the first place.
THE DYNAMIC RELATIONSHIP BETWEEN STOCK PRICES AND EXCHANGE RATES: EVIDENCE FOR BRAZIL
Authors: TABAK BENJAMIN M.
Published: November 2006

This paper studies the dynamic relationship between stock prices and exchange rates in the Brazilian economy. We use recently developed unit root and cointegration tests, which allow endogenous breaks, to test for a long run relationship between these variables. We performed linear, and nonlinear causality tests after considering both volatility and linear dependence. We found that there is no long run relationship, but there is linear Granger causality from stock prices to exchange rates, in line with the portfolio approach: stock prices lead exchange rates with a negative correlation. Furthermore, we found evidence of nonlinear Granger causality from exchange rates to stock prices, in line with the traditional approach: exchange rates lead stock prices. We believe these findings have practical applications for international investors and in the design of exchange rate policies.
MINIMAL VARIANCE HEDGING FOR INSIDER TRADING
Authors: BIAGINI FRANCESCA , ØKSENDAL BERNT
Published: November 2006

In this paper, we first study the problem of minimal hedging for an insider trader in incomplete markets. We use the forward integral in order to model the insider portfolio and consider a general larger filtration. We characterize the optimal strategy in terms of a martingale condition. In the second part we focus on a problem of mean-variance hedging where the insider tries to minimize the variance of his wealth at time T given that this wealth has a fixed expected value A. We solve this problem for an initial enlargement of filtration by providing an explicit solution.
OPTIMAL MULTIPLE STOPPING AND VALUATION OF SWING OPTIONS IN LÉVY MODELS
Authors: ZEGHAL AMINA BOUZGUENDA , MNIF MOHAMED
Published: November 2006

In this paper, we extend the results of Carmona and Touzi [6] for an optimal multiple stopping problem to a market where the price process is allowed to jump. We also generalize the problem of valuation swing options to the context of a Lévy market. We prove the existence of multiple exercise policies under an additional condition on Snell envelops. This condition emerges naturally in the case of Lévy processes. Then, we give a constructive solution for perpetual put swing options when the price process has no negative jumps. We use the Monte Carlo approximation method based on Malliavin calculus in order to solve the finite horizon case. Numerical results are given in the last two sections. We illustrate the theoretical results of the perpetual case and give the numerical solution for the finite horizon case.
TSLP: An Epithelial Cell Cytokine that Regulates T Cell Differentiation by Conditioning Dendritic Cell Maturation
Authors: Liu Yong-Jun , Soumelis Vassili , Watanabe Norihiko , Ito Tomoki , Wang Yui-Hsi , de Waal Malefyt Rene , Omori Miyuki , Zhou Baohua , Ziegler Steven F.
Published: November 2006

Dendritic cells (DCs) are professional antigen-presenting cells that have the ability to sense infection and tissue stress, sample and present antigen to T lymphocytes, and induce different forms of immunity and tolerance. The functional versatility of DCs depends on their remarkable ability to translate collectively the information from both the invading microbes and their resident tissue microenvironments and then make an appropriate immune response. Recent progress in understanding TLR biology has illuminated the mechanisms by which DCs link innate and adaptive antimicrobial immune responses. However, how tissue microenvironments shape the function of DCs has remained elusive. Recent studies of TSLP (thymic stromal lymphopoietin), an epithelial cell–derived cytokine that strongly activates DCs, provide evidence at a molecular level that epithelial cells/tissue microenvironments directly communicate with DCs. We review recent progress on how TSLP expressed within thymus and peripheral lymphoid and nonlymphoid tissues regulates DC-mediated central tolerance, peripheral T cell homeostasis, and inflammatory Th2 responses.
Assessing Public Health Emergency Preparedness: Concepts, Tools, and Challenges
Authors: Nelson Christopher , Lurie Nicole , Wasserman Jeffrey
Published: November 2006

Policymakers are increasingly seeking to determine whether the federal government's recent investments in public health preparedness have left the public health system better prepared to respond to large-scale public health emergencies. Yet, there remain questions about how to define “public health emergency preparedness,” how much preparedness is enough, and how preparedness can be measured and assessed. This chapter identifies the key challenges associated with measuring public health preparedness and reviews approaches currently in use. We also identify some emerging measurement techniques that might help address some of these challenges.
Building Nano-Composite Dielectric Materials from the Bottom Up: Carbon Nanotubes Based Nanostructures
Authors: Luna-Sánchez Rosa María , González-Martínez Ignacio
Published: November 2006

We offer to fabricate nanocomposite dielectric materials by nano-structured templates. Such technique is used to fabricate organic semiconductor/carbon nanotube nanocomposites and distributed three dimensional p-n junctions.
New Theory of Effective Workfunctions at Metal/High-k Dielectric Interfaces -Application to Metal/High-k HfO2 and La2O3 Dielectric Interfaces
Authors: Luna-Sánchez Rosa María , González-Martínez Ignacio
Published: November 2006

We have constructed a universal theory of the work functions at metal/high-k HfO2 and La2O3 dielectric interfaces by introducing a new concept of generalized charge neutrality levels. Our theory systematically reproduces the experimentally observed work functions of various gate metals on Hf-based high-k dielectrics, including the hitherto unpredictable behaviors of the work functions of p-metals. Our new concept provides effective guiding principles to achieving near-band-edge work functions of gate metals. Moreover, we discuss the potential of the new high-k dielectrics of La2O3 based on this new concept.
Combinatorial Fabrication and Characterization of Oxide and Metal Thin Film Composition Spreads
Authors: Luna-Sánchez Rosa María , González-Martínez Ignacio
Published: November 2006

A combinatorial fabrication method for binary composition spread and three-component composition spread thin films was developed. Any desired specific part or a complete binary/ternary diagram can be deposited onto a single substrate by sequentially ablating /sputtering target materials using a pulsed laser or an ion beam sputter. The developed deposition technique is useful for accurate determination of the structural and physical properties relations with composition in a film. The deposition technique also enables us to rapid establishing phase diagrams of binary/ternary oxide and metal thin films.
Product Level Reliability Challenges for 65 nm Technologies
Authors: Luna-Sánchez Rosa María , González-Martínez Ignacio
Published: November 2006

We present a comprehensive review of product level reliability challenges for the 65nm technology node. The major reliability degradation mechanisms are analyzed for CMOS technologies. Historical data shows that hot carrier degradation has lost importance and that negative bias temperature instability (NBTI) is the leading reliability concern for the 65nm technology node. Additionally, dielectric breakdown as well as gate leakage currents pose an important limitation to the maximum applicable voltage across the gate oxide. Product standby currents and regulator design are highly influenced by transistor reliability. We will present product reliability data ensuring sufficient product level reliability as well as their correlation attempts to transistor level data.
High-k/Si Interface Engineering Using a Valence-Mending Technique
Authors: Luna-Sánchez Rosa María , González-Martínez Ignacio
Published: November 2006

A monolayer of Se is deposited on Si(100) before high-k deposition. HfO2 and Al2O3 are deposited by 'gentle' methods of evaporation/oxidation, CVD and ALD. Significant improvement in interface and high-k properties are observed with Se, including suppression of interfacial oxide above 400C, reduction in leakage current by over an order of magnitude, reduction in C-V hysteresis by a factor of 2 and reduction in interface trap density by a factor of 5. Further improvement in thermal stability above 1,000C and EOT below 1 nm requires 1) a non-oxide high-k dielectric to prevent interfacial oxide and 2) an in-situ ultrahigh vacuum process for surface preparation and high-k deposition to prevent surface contamination.
Recent Progress of SiGe Heterostructure Technologies for Novel Devices
Authors: Luna-Sánchez Rosa María , González-Martínez Ignacio
Published: November 2006

The recent progress of SiGe hetrostructure technologies is reviewed by using the authors' results. Low temperature (<550oC) methods to achieve SiGe crystals on insulating films are developed by the combination of metal induced lateral crystallization and electric field application. In addition, epitaxial growth of ferromagnetic silicide on Si and Ge substrates becomes possible at 60-300oC. These results will be the key techniques to open new era of SiGe-based thin film transistors and spintronics devices.
Copper Diffusion and Corrosion Behavior Through the Hillock Defect Found Beneath the Weak SiN Dielectric Barrier in Dual Damascene Process
Authors: Luna-Sánchez Rosa María , González-Martínez Ignacio
Published: November 2006

Adopting copper as an interconnect metal, many issues related to copper process have happened. Copper hillock is one of those issues. Copper hillock is generated usually during copper dual damascene process. Many researchers had studied the root-cause of copper hillock and various results have been reported. However, the effect of hillock to the actual device is not that much researched yet. Moreover, copper hillock is considered that it does not influence device functioning seriously. The purpose of this work is to clarify the effect of copper hillock to device and provide a solution for reducing it. According to the test results, copper hillock generates the particle of copper-oxide on via hole. Therefore, it is needed that the particle should be removed because it generates copper void by blocking the barrier metal and copper deposition in via hole. From the result of copper hillock reducing test, it can be decreased dramatically by adding anneal and touch up copper CMP processes.
An Easy Method to Measure the Damaged Thickness of Low-k Film after Ash Process
Authors: Luna-Sánchez Rosa María , González-Martínez Ignacio
Published: November 2006

A carbon loss of low-k film occurs when O2-contained gas is used for stripping of photo-resist (PR). A modified SiO2-like layer of low-k film after ash process is called as a damaged or modified layer, indicating deterioration of device performance. Auger electron spectroscopy (AES), secondary ion mass spectroscopy (SIMS) and so on are used for measuring the degree of low-k damage. These analyses, however, have a disadvantage which is difficult to do in-line monitoring, and should have a wafer broken. The key point in this study is that low-k film containing carbon species is not etched by selective SiO2 etching solution. We used wet process such as dilute HF(100:1) and NE14 to remove a damaged layer, that is, SiO2-like layer. Wet- clean method of low-k material after ash process was found to be a powerful and simple method to evaluate the thickness of the damaged layer numerically with small deviation, compared to FTIR, AES and SIMS analyses.
Electrical Characteristics of Erbium Oxide Films on Silicon Substrate by Reactive RF Sputtering for Different Metal Gate
Authors: Luna-Sánchez Rosa María , González-Martínez Ignacio
Published: November 2006

Erbium oxide film was deposited on Si substrate by reactive RF- sputtering from an erbium target for TaN and Al gate electrode. We found that Er2O3 dielectric with TaN electrode exhibits excellent electrical properties such as significantly a lower leakage current, higher capacitance value and thermal stability. This Er2O3 gate dielectric appears to be very promising for future ULSI devices.
Degradation in Hafnium Oxynitride (HfNO) High-k Dielectric under Nanoscaled Ramped Voltage Stress by Using Conductive Atomic Force Microscopy
Authors: Luna-Sánchez Rosa María , González-Martínez Ignacio
Published: November 2006

In this work, we used conductive atomic force microscopy (C-AFM) to study the degradation and post-breakdown characteristics of reactive sputter deposited hafnium oxynitride (HfNO) high-k dielectric by applying repetitive ramped voltage stress (RVS) to the oxynitride films. From the power-law fitting of the post-breakdown I-V characteristics, we found three different types of conduction modes are possible in the high-k oxynitride films. Conduction mechanism based on conductivity switching in conjunction with charge trapping and detrapping was given to explain these different post-breakdown conduction modes.
Angle-Resolved Photoelectron Spectroscopy Study on Gate Insulators
Authors: Luna-Sánchez Rosa María , González-Martínez Ignacio
Published: November 2006

As a typical example of angle-resolved photoelectron spectroscopy studies, our detailed study on the composition and the chemical structure of oxynitride films was reviewed. The structure of oxynitride/Si interface was determined from the nearest neighbors of a nitrogen atom and those of a silicon atom detected by X-ray photoelectron spectroscopy. The roughness of interface measured by non-contact mode AFM was found to increase if the amount of nitrogen atoms at the interface exceeds a threshold value of 0.37 monolayers. This increase in interface roughness above this threshold can be attributed to the incorporation of nitrogen atoms in the silicon oxide layer next to the interface.
High-k Gate Stack Engineering and Low Frequency Noise Performance
Authors: Luna-Sánchez Rosa María , González-Martínez Ignacio
Published: November 2006

Gate stack engineering for deep submicron CMOS has been extensively studied, so that high-k dielectrics in combination with metal gate or FUSI electrodes are implemented in research lines. Much effort concentrated on the optimization of gate stacks from a viewpoint of dielectric properties and reliability. Less information is available on the low frequency noise performance of these gate stacks. This review demonstrates the necessity of gate stack engineering for achieving a low 1/f noise performance. The impact of processing parameters, such as thickness of the interfacial layer and the high-k oxide, bulk properties of the high-k layer, post deposition anneals, choice of gate electrode material will be addressed. Such a systematic study forms the basis for noise modeling as for these gate-dielectrics the standard noise models are no longer applicable. The impact on the noise of strain engineering to boost up the carrier mobility is also briefly discussed.
Advanced Gate Stacks with Fully Silicided (FUSI) Gates and High-k Dielectrics for Low Power CMOS
Authors: Luna-Sánchez Rosa María , González-Martínez Ignacio
Published: November 2006

We present a new threshold-voltage (Vth) control technique for fully-silicided metal/high-k gate stacks which are suitable for 45nm-node LOP and LSTP CMOS. The key is the phase control of FUSI Ni-silicide (PC-FUSI) by changing Ni film thickness prior to silicidation anneal. As a result, Ni3Si and NiSi2 are formed whose effective workfunctions (WFs) on HfSiON are found to be 4.8eV and 4.4eV, respectively, being largely displaced from Si-midgap by {plus minus}0.2eV. Meanwhile, the dopant segregation method, known to be successful in Vth-control of NiSi on SiO2, did not work on HfSiON. With Ni3Si-PFET and NiSi2-NFET transistors, a wide range of Vth-tuning is achieved coping with both LSTP and LOP requirements. At the same time, leakage suppression merit is better than the 45nm-node targets at electrical thickness (Tinv) around 2.0nm. Also, our PC-FUSI devices show performance improvement and sufficient long term reliability.
Present and Future of Si-Based Transistor Technology for Memories
Authors: Park Donggun , Ryu Byung-Il
Published: November 2006

Nanotechnology is named as a promising research area for the semiconductor technology to be extended or replaced by it. Since the silicon based devices such as NAND Flash memory, DRAM, SRAM, and CPUs are scaled down below 100 nm entering into the nanoscale regime late 1990s, in the middle of 2005, we are already facing the appearance of sub 50 nm technology in production. In this paper, we introduce recent technology development activities in Samsung to realize the sub 50 nm technologies into the devices such as SRAM, DRAM, and Flash memories as well as the high performance logic devices. RCAT (Recessed Cell Array Transistor), PiFET (Partially-insulated MOSFET) and FinFET, McFET (Multi channel FET), MBCFET (Multi- Bridge Channel MOSFET), and Twin Silicon Nanowire MOSFET (TSNWFET) are the 3-dimensional structure CMOS transistors to be introduced for nanoscale applications.
Front-End Process Technology for hp65/45 CMOS Devices
Authors: Nara Yasuo , Ootsuka Fumio , Nakamura Kunio
Published: November 2006

In order to obtain high performance CMOS devices, introduction of new technologies into the front-end fabrication process are required and therefore so-called technology boosters such as strained channel, metal gate, high-k gate dielectrics, thin body SOI, and multi-gate transistor, are proposed so far. Among these technologies, gate stack technology is common key issue for scaled CMOS devices. In this proceeding, we will discuss on high-k gate dielectrics and metal gate technology, and recent achievements of these technologies are reviewed.
Trends in European R&D - Advanced Process Control Down to Atomic Scale for Micro- and Nanotechnologies
Authors: Pfitzner Lothar , Schellenberger M. , Oechsner R. , Roeder G. , Pfeffer M.
Published: November 2006

Manufacturing of semiconductor devices continues to follow Moore{section sign}s Law. Key challenge of future manufacturing of microand nanotechnologies will be a much tighter process control. This paper will describe some trends in advanced process control (APC). Definitions of APC, current status of basic principles, elements and future requirements will be given. Three methods of advanced process control are presented, which have to be adapted to further challenges in micro- and nanotechnologies: integrated metrology, run-to-run control (feed-forward / feedback control) and fault detection and classification (FDC). Integrated process and metrology tools have to provide relevant data. The data may be tool data, process data and/or wafer data. An engine analyzes the data for SPC, application of run-to-run control loops and fault detection in order to initiate necessary control actions. Examples from 20 years of own R&D embedded in European activities related to these focal fields will be given.
An Atomically Accurate Model for Point Defect Aggregation in Silicon
Authors: Sinno Talid , Haeckl Walter , von Ammon Wilfried
Published: November 2006

An atomically accurate model for vacancy aggregation is presented. The model is based on two recently developed elements: (1) an accurate set of point defect properties derived from extensive model regression to multiple types of experimental data, and (2) a new description of point defect clusters at elevated temperature, which includes previously neglected entropic contributions. The latter are found to substantially alter both the cluster thermodynamics and the cluster structures, leading to modified clustering dynamics during crystal growth and wafer annealing. The model is tested extensively against experimental measurements of void densities, sizes, and aggregation temperatures, and is found to provide excellent agreement with experimental data across a wide range of crystal growth conditions.
Wafer Strength and Slip Generation Behavior in 300 mm Wafers
Authors: Ono Toshiaki , Sugimura Wataru , Kihara Takayuki , Hourai Masataka
Published: November 2006

Dependence of mechanical strength of large diameter wafers as a function of impurity concentration and density of oxide precipitates has been studied in terms of brittle fracture and slip dislocation propagation.
Discussion on Issues Toward 450 mm Wafer
Authors: Watanabe Masaharu , Fukuda Tetsuo , Ogura Atsushi , Kirino Yoshio , Kohno Mitsuo
Published: November 2006

This reports a present status of recent technical discussions on 450mm wafer. Discussions are focusing on mechanical wafer specification, especially, wafer thickness based on thermal stress and other factors, which may determine correct, wafer thickness.
300 mm SOI for High Volume Manufacturing
Authors: Pfeiffer Gerd , Haag M. , Schmidt M. , Krause R. , Tsai P. , Lee J.D.
Published: November 2006

300 mm SOI for leading edge CMOS applications has been moving into high volume manufacturing recently but little information on the quality of these wafers is available. This paper reviews key characteristics of 300 mm SOI and how they compare to the status from several years ago. For physical characteristics, Si layer thickness and uniformity, surface quality and defects, flatness, surface roughness, metal contamination and slip are surveyed. Electron mobility, buried oxide charge and interface state density data obtained from pseudo MOSFET measurements are employed to monitor the electrical characteristics of the SOI structure.
Growth Kinetics and Electrical Properties of Ultrathin Silicon Dioxide Layers
Authors: Massoud Hisham Z.
Published: November 2006

In this paper, the growth kinetics and electrical properties of ultrathin silicon-dioxide layers are reviewed. Topics discussed here include the onset of oxide growth, the effects of temperature, substrate orientation, dopant type and concentration, and stress on oxide growth kinetics. The use of in situ real-time ellipsometry to control the rapid- thermal oxidation of silicon will be presented. The electrical properties of the ultrathin silicon-dioxide layers will be discussed, especially the contact potential difference in MOS devices and its dependence on the processing history and substrate orientation which will be explained in terms of the role of partial-charge-transfer dipoles at the oxide/silicon interface. Finally, gate tunneling considerations in MOSFET design, modeling, characterization, and circuit performance will be briefly presented.
Scaled CMOS with SiON and High-k
Authors: Ishimaru Kazunari , Takayanagi M. , Watanabe T. , Inaba S. , Fujiwara M. , Matsushita D.
Published: November 2006

A MOSFET dimension is continuously scaled down to improve its performance. Gate insulator thickness reaches, however, almost its physical limitation in the case of SiON film. Recently, fabrication process of SiON film for less than 1nm EOT was presented. This technology can extend applicability of SiON film beyond 65 nm node. High-k film is a promising candidate to replace SiON film with lower leakage current. HfSiON is one of the candidates for high-k materials. Despite the intensive studies by many researchers, pMOS Vth shift caused by Fermi-level pinning is still the biggest problem when combined with poly-Si gate electrode. This paper addresses issues for scaled CMOS with SiON and high- k. Process optimization method with device characteristics is demonstrated for 45 nm node and beyond.
Mobility Enhancement and Strain Integration in Advanced CMOS
Authors: Diaz C. H.
Published: November 2006

Mobility enhancement techniques have become pervasive in advanced CMOS technologies. Non-scalable and scalable approaches to mobility enhancement are widely used in various application segments (high-speed, low-operating power, and low- standby power). Non-scalable techniques rely on preferential channel directions having fundamentally higher carrier mobility than the conventional <110> directions of (100) substrates. On the other hand, scalable techniques rely on process built-in mechanical strain to boost mobility as a result of band- structure response impacting both carrier-effective mass and scattering rates. Scalable techniques are based on the channel strain induced by contact-etch stop layers or Si(1-x)Ge(x) structures primarily. This paper will review both non-scalable and scalable mobility enhancement approaches from two angles, namely fundamental device physics and overall device integration schemes. The paper will also review and discuss issues related to superposition of process built-in strain for performance enhancement.
Impact of Defects in Silicon Substrate on Flash Memory Characteristics
Authors: Hirano Yori , Yamazaki Ken , Inoue Fumihiko , Imaoka Kazunori , Tanahashi Katsuto , Yamada-Kaneta Hiroshi
Published: November 2006

Floating-gate type Flash memories are fabricated on Czochralski (CZ) silicon wafers. A large amount of residual misalignment in reticle shots at photolithography process step and the programming failure are observed in the low oxygen concentration wafer. The above are explained by the plastic deformation of wafer by the relaxation of internal stress during the processes.
SOI Low Frequency Noise and Interface Trap Density Measurements with the Pseudo MOSFET
Authors: Kushner Vadim A. , Yang Jinman , Choi Joon , Thornton Trevor , Schroder Dieter
Published: November 2006

Low frequency noise (LFN) is important in analog and digital circuits. In analog circuits it affects the performance of low- noise amplifiers and the phase noise of voltage-controlled oscillators. In digital circuits it becomes more important as the supply voltage is reduced and it degrades substrate noise coupling. Low-frequency noise is due to interactions of the channel carriers with oxide/semiconductor interface traps and oxide charges and is very dependent on the quality of the oxide/semiconductor interface and noise measurements can give important information about such interfaces and defects (1). Silicon-on-insulator devices have two oxide/semiconductor interfaces and the bottom interface is generally worse than the top interface. Most LFN measurements are made after MOSFET fabrication, but it is desirable to characterize such materials without fabricating devices. In this paper we discuss silicon- on-insulator (SOI) low-frequency noise and interface trap density measurements using a Ground-Signal-Ground (GSG) pseudo- MOSFET structure with minimum fabrication.
Study of Inhibition Characteristics of Slurry Additives in Copper CMP Using Force Spectroscopy
Authors: Keswani Manish K. , Lee Hyosang , Babu Suryadevara , Patri Udaya , Hong Youngki , Economikos Laertis , Goldstein Michael , Borucki Len , Philipossian Ara , Zhuang Y.
Published: November 2006

Using a reference slurry, ammonium dodecyl sulfate (ADS), an anionic and environmentally friendly surfactant, was investigated as an alternative to BTA for its inhibition and lubrication characteristics. Results demonstrated that the inhibition efficiency of ADS was superior to that of BTA. Coefficient of friction (COF) was the lowest when the slurry contained ADS. This suggested that adsorbed ADS on the surface provided lubricating action thereby reducing the wear between the contacting surfaces. Temperature results were consistent with the COF and removal rate data. ADS showed the lowest temperature rise again confirming the softening effect of the adsorbed surfactant layer and less energy dissipation due to friction. Spectral analysis of shear force showed that increasing the pad-wafer sliding velocity at constant wafer pressure shifted the high frequency spectral peaks to lower frequencies while increasing the variance of the frictional force. Addition of ADS reduced the fluctuating component of the shear force and the extent of the pre-existing stick-slip phenomena caused by the kinematics of the process and collision event between pad asperities with the wafer. By contrast, in the case of BTA, there were no such observed benefits but instead undesirable effects were seen at some polishing conditions. This work underscored the importance of real-time force spectroscopy in elucidating the adsorption, lubrication and inhibition of additives in slurries in CMP.
Probing Nanoscale Local Lattice Strains in Advanced Si CMOS Devices by CBED: A Tutorial with Recent Results
Authors: Kim Moon , Huang Jiang , Chidambaram P.R. , Irwin Richard , Jones Patrick , Weijtmans J.W. , Koontz Elisabeth Marley , Wang Yuguo , Tang Shaoping , Wise Rick
Published: November 2006

The experimental methodology to characterize the nanoscale local lattice strain in advanced Si CMOS devices by using Focused Ion Beam (FIB) system and Convergent Beam Electron Diffraction (CBED) is discussed. Through both high spatial resolution of Transmission Electron Microscopy (TEM) and high strain sensitivity of the CBED technique, compressive lattice strains in the order of 0.001 from the nanoscale Si PMOS channel region are detected. The one-dimensional quantitative strain-mapping is performed by obtaining and simulating high quality CBED patterns with different zone axes such as <230> and <340>.
Analysis of Nanoscale Stress in Strained Silicon Materials and Microelectronics Devices by Energy-Filtered Convergent Beam Electron Diffraction
Authors: Zhang Peng , Istratov Andrei , He Haifeng , Ager Joel , Nelson Chris , Stach Eric , Mardinly John , Kisielowski Christian , Weber Eicke , Spence John
Published: November 2006

The convergent beam electron diffraction (CBED) technique of transmission electron microscopy (TEM) has excellent capabilities for strain detection at high spatial resolution. Here we report strain measurements in a bulk s-Si/SiGe/Si wafer and in a strained 35nm PMOS device in which SiGe acts as the source and drain. CBED measurements of the composition of the relaxed SiGe buffer are in quantitative agreement with Raman spectroscopy. For the PMOS device, CBED measured a uniaxial compressive stress of 1.12GPa in the channel. However, it was found that even in the cross-sectional TEM samples with thicknesses greater than 300nm, the intrinsic surface strain relaxation was often so severe that no recognizable high-order Laue zone lines in the CBED patterns could be collected. The amorphorization of both free surfaces of the TEM sample to a range of about 80nm is proposed to minimize the impact of surface strain relaxation for future study.
Electrochemical Studies on Heazlewoodite Flotation from Inco Matte
Authors: Rao Ramachandra , Finch James
Published: November 2006

Electrochemical and flotation studies were conducted on Inco matte, composed of chalcocite (Cc), heazelwoodite (Hz) and Cu- Ni alloy. After magnetic removal of the alloy, the Cc is floated using diphenyl guanidine. There is some flotation of heazelwoodite due to inadvertent activation by Cu ions. This was investigated by rest potential measurements on matte components and mild steel, detection of Cu ions by EDTA extraction, and flotation. Rest potentials at pH 11.9 showed the order: Cc>mild steel>Cu-Ni alloy>Hz. Along with Cc, the Cu- Ni alloy is potentially galvanically active, releasing Cu ions. Sodium dithionite proved the most effective, reducing the rest potential and Cu ion release. Subsequent flotation, however, required aeration to restore Cc floatability. The need for aeration is compatible with the proposed surface product formed by reaction between Cu and DPG.
Single Particle Microelectrodes for Electrochemical Analysis of Sulfide Flotation Processes
Authors: Miller Jan D. , Vermaak Thys , Moats Michael
Published: November 2006

The true electrochemical characteristics of sulfides found in industrial processes are of interest and as a result a relatively simple technique has been developed to study fundamental electrochemical interactions of individual particles measuring less than 100 microns in diameter. Cyclic voltammetry with sulphide mineral microelectrodes has been carried out on sulphide particles hand-picked from the concentrate and tailings products of an auriferous sulfide ore floated in air and nitrogen. These particles were found to be exclusively pyrite for the +53 micron fraction. Experimental results show no prominent differences in the electrochemical response of these pyrite particles from different flotation products but it appears that particle shape effects can contribute to pyrite losses in the tailings product.
Electrochemical Study of the Interaction Galvanic Between Pyrite and Arsenopyrite Through Measurements of Electrode Potentials and Determinations of Contact Angle
Authors: Monte Marisa , Albuquerque C. R. F. , Dutra A. J. B.
Published: November 2006

The galvanic interaction between two minerals leads to redox reactions that change the surface of minerals, affecting their floatabilities. In the present work, the galvanic interaction between pyrite and arsenopyrite was studied through measurements of electrode potentials with and without electrical contact allied to contact angle between these sulfides, indicating that the interaction inhibited the pyrite oxidation and caused an increase of its contact angle. In the case of arsenopyrite, the galvanic interaction caused a decrease of about 50% on its contact angle, without interation, indicating a surface oxidation with the formation of FEOOH. Nitrogen bubbling leads to higher contact angles and lower potentials values for both minerals with and without interation between each other.
Use of an Evaporated Gold SERS Substrate to Detect 2-Mercaptobenzothiazole on Sulfide Mineral Surfaces
Authors: Hope Gregory A. , Buckley Fionnuala , Woods R. , Watling Kym
Published: November 2006

The interaction of 2-mercaptobenzothiazole (MBT) with the sulfide mineral surfaces, chalcopyrite (CuFeS2), chalcocite (Cu2S) and synthetic copper sulfide (CuxS) thin films, was investigated by Raman spectroscopy. Gold was evaporated onto the sulfide surface to facilitate surface enhancement of Raman scattering. Raman and gold-induced SERS spectra from mineral surfaces exposed for various times to solutions of different MBT concentrations, recorded before and after gold decoration, were used to elucidate the mechanism of collector adsorption. Spectra were identified with MBT bonded to copper atoms in the mineral surface and not to bonding to the gold overlayer. Spectra obtained from each sulfide surface displayed the band arising from the NCS ring stretch vibration of MBT downshifted from its position from CuMBT. The shift was similar to that found previously for MBT chemisorbed on a copper metal electrode. MBT chemisorbs to copper atoms in the mineral surfaces through the exocyclic sulfur atom.
A SERS Investigation of the Interactionof Sulfur with Gold
Authors: Watling Kym , Parker Gretel , Hope Gregory A. , Woods Ronald
Published: November 2006

The interaction of S-II solution species with gold has been studied using surface-enhanced Raman spectroelectrochemical techniques to provide a basis for understanding sulfur layers formed during the oxidation of sulfide minerals and the leaching of gold in thiosulfate. Underpotential deposition in acid and basic media is characterized by a nu(Au-S) band. This is explained by a monoatomic S layer bonded to gold atoms in the electrode surface as in the sqrt 3 x sqrt 3 R30{degree sign} lattice reported from STM studies. The surface coverage in this potential region is limited to 0.35 ML. At potentials above the S-II/S0 reversible value, surface coverage increases and nu(S-S) bands are observed indicating the formation of Sn species. As coverage increases further, d(S-S-S) bands develop that are characteristic of the stable S8 structure. Bands were found to be absent that would have indicated the adsorption of SH species as reported in the literature.
Surface Stoichiometry of Lead Sulfide and the Sorption of Xanthates
Authors: Nowak Pawee
Published: November 2006

The measurements of the free charge carrier (FCC) absorption of the infra-red (IR) radiation during the oxidation of lead sulfide surface both in air and in aqueous solutions, either by dissolved oxygen or by anodic polarization, shows that the oxidation of PbS is always accompanied by the formation of metal-depleted layer at the surface. However the attained degree of non-stoichiometry is limited and the sulfur-enriched layer at the surface relaxes spontaneously with the formation of stoichiometric PbS and sulfur species. Oxidized PbS surfaces adsorb xanthate from deoxidized solutions easily and fast, even if the oxidized lead species have been removed from the surface. The electrosorption of xanthate radicals driven by the oxidation of xanthate ions by the sulfur species present at the surface seems to be the most probable explanation of that behavior.
XPS, Static SIMS and NEXAFS Spectroscopic Investigation of Thiol Adsorption on Metals and Metal Sulfides
Authors: Buckley Alan N. , Goh Siew Wei , Lamb Robert , Fan Liang-Jen , Yang Yaw-Wen
Published: November 2006

Examples are presented of the complementary nature of conventional XPS, synchrotron XPS, ToF-SIMS and NEXAFS spectroscopy when applied to the adsorption of MBT on metals and metal sulfides. Conventional XPS could detect chemisorption via S 2p spectra, detect the onset of multilayer formation via the relevant metal Auger or core level photoelectron spectra, and determine metal thiolate stoichiometry from thick multilayers. Surface-optimised synchrotron XPS allowed precise chemisorbed MBT S 2p binding energies to be obtained. Angle-dependent N and C NEXAFS spectra revealed adsorbate orientation, even for an abraded but relatively smooth surface. Cu L3-edge spectra detected some Cu(II) and hence Cu(MBT)2 in multilayers on chalcocite. Static SIMS data confirmed the interaction of both N and exocyclic S with surface metal atoms for silver metal and chalcocite.
Surface Products on Gold Leached in Ammoniacal Copper(II) Thiosulfate Solution
Authors: Watling Kym , Hope Gregory A. , Jeffrey Matthew I. , Woods R.
Published: November 2006

Surface-enhanced Raman scattering (SERS) spectroscopy has been applied in situ to identify species formed during gold leaching in copper(II) ammoniacal thiosulfate media. Species containing copper and sulfur develop on the gold surface and the coverage of these species was determined electrochemically. Vibrational modes due to sulfur-sulfur stretching at 382 cm-1 and symmetric sulfur-oxygen stretching at 1017 cm-1 develop during leaching. These modes diminish and are replaced by a single band at 255 cm-1, assigned to a M-S stretch, when rinsed and examined in water. In typical leach solutions, sulfur and copper coverages showed a 2:1 atomic ratio after leaching for 16 h. Ex situ ATR- FTIR and XPS studies show that ammonia is adsorbed to a surface copper sulfide.
Electrochemical Behavior of the Oxidation and Reduction Processes for Pyrargyrite (Ag3SbS3) in Acidic Media
Authors: Luna-Sánchez Rosa María , González-Martínez Ignacio
Published: November 2006

The refractory nature of a mineral phase is an indication of the difficulty to leach its component precious metals. In this study, the electrochemical behavior of the silver contained in pyrargyrite (Ag3SbS3), a very refractory phase, was determined in order to better understand the oxidation and reduction processes involved in the leaching of the metallic species from sulfide concentrates. A voltammetric characterization was performed in 25 mM sulfuric acid solution, using as the working electrode a mineral species-carbon paste, agglomerated with silicon oil (CPE). A comparative study between pyrargyrite (Ag3SbS3, pure), acanthite (Ag2S) and antimony sulfide (Sb2S3), was carried out. The formation of some metallic species, corresponding to antimony and silver contained in pyragyrite, were observed in the voltammetric curves. This study shows in a qualitative manner the reason for the refractory nature of this mineralogical phase for oxidation in acid media.
Reductive Leaching of Chalcopyrite by Aluminum
Authors: Doyle F. , Lapidus Gretchen
Published: November 2006

The reductive leaching of chalcopyrite to chalcocite was achieved by contact with metallic aluminum in acidic solutions at near ambient temperatures. It was shown that increased aluminum surface area, temperature and chloride concentrations lead to larger reduction velocities and aluminum consumption. The controlling mechanism appears to be related to hydrogen generation.
The Electrochemistry of the Leaching Reactions in the Caron Process. I. Anodic Processes
Authors: Nikoloski Aleksandar N. , Nicol Michael
Published: November 2006

The Caron process involves the oxidative dissolution of pre-reduced iron alloys containing nickel, cobalt and copper in ammoniacal carbonate solutions. This study has demonstrated that passivation is exhibited by nickel and cobalt at higher potentials than previously established for iron. It is shown that alloys of iron with nickel and cobalt also undergo passivation at low potentials resulting in inhibition of the dissolution of the valuable metals. The potential regions of active dissolution of each of these metals in ammonia-ammonium carbonate solutions have been established. The effect of thiosulphate and cobaltammine complex ions on the dissolution of iron and nickel was found to be significant in that thiosulphate appears to partially prevent the passivation of nickel while the presence of cobaltammine ions leads to lower apparent anodic current densities. Possible mechanisms for the passivation processes and for the effects of thiosulfate and cobaltammines on the dissolution are presented.