bluuebunny/crossref_metadata_2025_split huggingface dataset:
Science Issues Related to Wafer Cleaning in Silicon Technology
Authors: Liehr M. 
Published: March 2011

ABSTRACTThis paper highlights a number of basic science issues related to wafer cleaning in silicon technology. Particle removal techniques, metal contamination, surface passivation, and integrated processing are used as key examples of areas of active research related to wafer cleaning. It is highlighted that wafer cleaning plays a far more significant role in device processing than just for contamination removal. However, even contamination removal faces formidable challenges such as the determination of safe contamination limits and the detection of trace amounts of contamination, all of which go well beyond the traditional realm of contamination control.
SHG(Second Harmonic Generation) in Reflection from GaAs Surfaces during Sulfur Passivation and Photochemical Washing Processes
Authors: Yamada Chikashi , Kimura Takahiro , Fuqua Peter 
Published: March 2011

ABSTRACTA passivation processes using Na2S and photochemical washing of GaAs (100) surfaces was studied in real time by a second-harmonic generation (SHG) technique. The intensities of surface-specific SHG signals were compared with those of photoluminescence (PL) signals. We found a remarkable similarity between the SHG and PL intensity changes during these processes. A band-bending model due to Fermi-level pinning at the surface has been applied in order to account for both the SHG and the PL intensity changes.
Texturing of InP Surfaces for Device Applications
Authors: Bailey Sheila G. , Fatemi Navid S. , Landis Geoffrey A. 
Published: March 2011

ABSTRACTA unique process for texturing InP (100) wafers by anisotropic etching has been developed. The process produces irregular V-grooves on the surface, which reduce the surface reflectivity. The process does not require photolithography or masking. The etching characteristics depend on doping, with etching tending to proceed more rapidly on the more heavily doped samples. Reduced reflectivity surfaces formed using this process can be applied to solar cells, photodetectors, and other optoelectronic devices.
Etching of Silicon (111) and (100) Surfaces in HF Solutions: H-Termination, Atomic Structure and Overall Morphology
Authors: Chabal Y. J. 
Published: March 2011

ABSTRACTHF etches silicon oxide, removes metal impurities and completely terminates the silicon surface with hydrogen. The H-passivated Si surfaces are stable, but can be slowly and selectively etched in buffered HF solutions or in hot water, changing the initial morphology of the interface. Si(111) surfaces flatten, forming large, ideally H-terminated (111) planes. Si(100) surfaces roughen, ultimately developing H-terminated (111) facets.
First-Principles Investigations of Hydrogen and Fluorine on Silicon Surfaces
Authors: Walle Chris G. Van De 
Published: March 2011

ABSTRACTState-of-the-art first-principles calculations allow detailed studies of the mechanisms by which hydrogen and fluorine interact with silicon. The results for hydrogen are presented in the form of an energy diagram which includes many different configurations. The theoretical values allow a discussion of issues such as hydrogen solubility, and desorption from a Si surface. For fluorine, we investigate the behavior as an interstitial impurity in the bulk, as well as Si-F interactions at or near the surface. A study of the insertion of F atoms into Si-Si bonds elucidates the microscopic mechanisms of etching, and the dependence of etch rate on doping. Thermodynamic aspects of HF etching are briefly discussed.
Scanning Tunneling Microscopy of HF-Controlled Si(111) Surfaces
Authors: Tokumoto Hiroshi , Morita Yukinori , Miki Kazushi 
Published: March 2011

ABSTRACTScanning tunneling microscopy (STM) was made in order to examine the surface structure and roughness in an atomic scale. The surfaces were prepared by several ways: NH4F (pH = 8) dipping just after RCA cleaning or after keeping in dry air for a few weeks; dipping into NH4F (pH = 8) solution or dipping into solutions with pH=10 just after boiling in HNO3. The STM images clearly showed that the surface structure and roughness are dependent on the sample treatments. The smooth surfaces with less defects were obtained for surfaces prepared by removing the HNO3-oxidized layer by NH4F (pH = 8) dipping.
Surface Conditioning Issues Related to Patiterning and Etching
Authors: Fonash S.J. , Ditizio R.A. , Gu T. , Mikulan P.I. , Awadelkarim O.O. , Collins R.W. , Rembetski J.F. , Reinhardt K.A. , Chan Y.D. 
Published: March 2011

ABSTRACTSurface conditioning issues arising from pattern transfer utilizing plasma etching are discussed. Two situations are considered: one in which an oxide on a silicon substrate is exposed to a plasma etching environment and one in which a silicon substrate is exposed to a plasma etching environment. Both situations can lead to the need for surface conditioning and, in some cases, even 950°C, 30 min. furnace anneals or 1050°C, 26 sec. rapid thermal anneals can fail to restore surface and near-surface properties.
Silicon Surface Morphology and the Reaction of Silicon with Oxygen
Authors: Ross Frances M. , Gibson J. Murray 
Published: March 2011

ABSTRACTWe discuss the measurement of the morphology of exposed surfaces and buried interfaces using plan view transmission electron microscopy techniques. We have observed the evolution of the silicon/oxide interface during both oxidation and oxygen etching of the Si (111) surface. We describe the interface morphology, the mechanisms of these oxidation reactions and the implications of these results for the processing of silicon surfaces.
Preliminary Post-Emplacement Safety Analysis of the Subseabed Disposal of High-Level Radioactive Waste
Authors: Kaplan Maureen F. , Koplik Charles M. 
Published: March 2011

ABSTRACTThe radiological hazard from the disposal of high-level nuclear waste deep within the ocean sediments is evaluated, on a preliminary basis, for locations in the central North Pacific and in the northwestern Atlantic. Radionuclide transport in the sediment and water column and by marine organisms is considered. Peak doses to an individual are approximately five orders of magnitude below background levels for both places. Sensitivity analyses for several imporLant aspects of the post-emplacement systems model are described.
Gamma Radiolysis Effects on Grande Ronde Basalt Groundwater
Authors: Gray W.J. 
Published: March 2011

ABSTRACTGamma radiolysis of reference Grande Ronde Basalt groundwater containing 700 mg/L methane produces a milky liquid that is a suspension of fine particles of organic polymers similar to polyethylene. The amount and nature of these polymers does not vary much over the range of conditions tested. Differences in the radiolytic products that are formed may occur when host rock and engineered-barrier materials are present. This possibility is currently being investigated as is the potential for interactions between radionuclides and the products of radiolysis.
Numerical Analysis of Radionuclide Migration Through Engineered Barriers
Authors: Cheung S.C.H. , Chan T. , Lopez R.S. 
Published: March 2011

ABSTRACTA finite-element simulation has been performed to study the effects on the radionuclide flux, of the failure characteristics of a nuclear fuel disposal waste container, the buffer configuration, and the backfill properties, assuming an intact borehole rock wall. The results show that the total integrated flux from a failed container, through the buffer to a backfill with a diffusion coefficient and hydraulic conductivity higher than that of the buffer, increases as the radial buffer thickness increases, and the vertical buffer thickness decreases. The total flux can be estimated by a one-dimensional diffusion equation. If the backfill has the same diffusion coefficient and hydraulic conductivity as the buffer, the total flux will be reduced by approximately 30% compared with the situation when crushed rock or sand is used as backfill. For localized failure of the waste container, the total flux is mainly dependent on the failure location regardless of the area of the failed surface.
Diffusion in the Matrix of Granitic Rock Field Test in the Stripa Mine Part 2.
Authors: Birgersson Lars , Neretnieks Ivars 
Published: March 2011

ABSTRACTA migration experiment in the rock matrix is presented. The experiment has been carried out in “undisturbed” rock, that is in rock under its natural stress environment. Since the experiment was performed at the 360 m-level (in the Stripa mine), the rock was subject to nearly the same conditions as the rock surrounding a nuclear waste repository as proposed in the Swedish concept (KBS).The results show that all three tracers (Cr-EDTA, Uranine and 1-) have passed the zone disturbed by the presence of the injection hole and migrated some distance into “undisturbed” rock.These results indicate the existence of a connected micro fissure system in undisturbed rock, in which tracers (and therefore radionuclides) can migrate. Diffusivities obtained in this experiment are comparable to those obtained in laboratory experiments.
Corrosion Test Plan to Guide Canister Material Selection and Design for a Tuff Repository.
Authors: McCright R. D. , Van Konynenburg R. A. , Ballou L. B. 
Published: March 2011

ABSTRACTCorrosion rates and the mode of corrosion attack form a most important basis for selection of canister materials and design of a nuclear waste package. Type 304L stainless steel was selected as the reference material for canister fabrication because of its generally excellent corrosion resistance in water, steam and air. However, 304L may be susceptible to localized and stress-assisted forms of corrosion under certain conditions. Alternative alloys are also investigated; these alloys were chosen because of their improved resistance to these forms of corrosion. The fabrication and welding processes, as well as the glass pouring operation for defense and commercial high-level wastes, may influence the susceptibility of the canister to localized and stress forms of corrosion.
Relationship of Engineering Geology to Conceptual Repository Design in the Gibson Dome Area, Utah.
Authors: Helgerson Ronald , Henderson Norman , Memorial Battelle 
Published: March 2011

ABSTRACTThe Paradox Basin in Southeastern Utah is being investigated as a potential site for development of a high-level nuclear waste repository. Geologic considerations are key areas of concern and influence repository design from a number of aspects: depth to the host rock, thickness of the host rock, and hydrologic conditions surrounding the proposed repository are of primary concern. Surface and subsurface investigations have provided data on these key geologic factors for input to the repository design.A repository design concept, based on the surface and subsurface geologic investigations conducted at Gibson Dome, was synthesized to provide needed information on technical feasibility and cost for repository siting decision purposes. Significant features of the surface and subsurface repository facilities are presented.
Performance Analysis of Conceptual Waste Package Designs in Salt Repositories
Authors: Jansen George , Raines Gilbert E. , Kircher John F. 
Published: March 2011

ABSTRACTA performance analysis of commercial high-level waste and spent fuel conceptual package designs in reference repositories in three salt formations was conducted with the WAPPA waste package code. Expected conditions for temperature, stress, brine composition, radiation level, and brine flow rate were used as boundary conditions to compute expected corrosion of a thick-walled overpack of 1025 wrought steel. In all salt formations corrosion by low Mg salt-dissolution brines typical of intrusion scenarios was too slow to cause the package to fail for thousands of years after burial. In high Mg brines judged typical of thermally migrating brines in bedded salt formations, corrosion rates which would otherwise have caused the packages to fail within a few hundred years were limited by brine availability. All of the brine reaching the package was consumed by reaction with the iron in the overpack, thus preventing further corrosion. Uniform brine distribution over the package surface was an important factor in predicting long package lifetimes for the high Mg brines.
Very Rough Preliminary Estimate of the Colloidal Sodium Induced in Rock Salt by Radioactive Waste Canister Radiation
Authors: Levy P. W. , Kierstead J. A. 
Published: March 2011

ABSTRACTVery rough estimates have been made of the total amount, the formation rate and spatial distribution of the Na metal colloid particles induced in rock salt adjacent to four types of radioactive waste canisters. A number of extrapolations were required. Salt immediately adjacent to a lightly shielded, 2.16 kW, high level waste canister could be converted entirely to colloidal Na (and presumably chlorine gas) in 200-400 years. The total Na metal formed will be 250-300 kg. A heavily shielded, 3.3 kW, spent fuel canister will convert roughly 0.3 percent of the salt at the canister surface to colloidal Na and the total sodium metal will be roughly 0.5 kg. Even at the lowest colloid levels the Na metal formed should greatly influence interactions between canisters and the surrounding salt, particularly if brine enters.
Selection of Barrier Metals for a Waste Package in Tuff
Authors: yyRussell E. W. , McCright R. D. , O'Neal W. C. 
Published: March 2011

ABSTRACTThe Nevada Nuclear Waste Storage Investigations (NNWSI) project under the Civilian Radioactive Waste Management Program is planning a repository at Yucca Mountain at the Nevada Test Site for isolation of high-level nuclear waste. Lawrence Livermore National Laboratory is developing designs for an engineered barrier system containing several barriers such as the waste form, a canister and/or an overpack, packing, and near field host rock. In this paper we address the selection of metal containment barriers.
Leaching Behavior of Simulated Radioactive Waste Glass by Neutron Activation Method
Authors: Sato Seichi , Furuya Hirotaka , Ohta Kazuaki , Sugisaki Masayasu , Tanai Tadaharu 
Published: March 2011

ABSTRACTSimulated radioactive waste glass was irradiated in a nuclear reactor and radiation damage was induced by 10B(n,0)7Li reaction up to 0.14 displacement per atom. Static leach tests of the activated waste glass were carried out at 40°C, up to 38 days. Concentration of elements in leachate was determined by gamma-spectrometry. The leach test of non-irradiated glass was also performed at 40°C up to 82 days in which the solution concentration of elements was determined by an atomic absorption analysis. Leach results are given in terms of normalized elemental mass loss for the seven elements Na, K, Cs, Ca, Zn, La and Ce. Normalized elemental mass loss of alkali ions was proportional to square root of time and then, was proportional to time. Normalized elemental mass loss of alkali earth ions did not show such a simple tendency. Build up of zinc on the waste glass surface was observed following its initial leaching. It was also found that theleach rate of Cs, Zn and Ce decreased with increase of irradiation exposure of waste glass.
Radiatio Damaae Growth Models for the Interpretation of Radiation Effects on Nuclear Waste Form Leaching
Authors: Ougouag A. M. , Machiels A. J. 
Published: March 2011

ABSTRACTTwo approaches for modeling radiation damage growth are presented and evaluated in the light of existing data. It results that purely geometric and statistical considerations about the distribution and overlap of damage are insufficient for accounting for the differences observed in leaching data from ion implantation and actinide doping experiments. It is shown, however, that the incorporation of effects such as those induced by the proximity of a free surface and the directionality of the irradiation into the kinetics of radiation damage ingrowth has the capability for accounting for the differences.
Conclusions from an Nea Workshop: The Role of Phenomenological Sorption Modelling in Performance Assessment of RadioactiveWaste Disposal Systems
Authors: Muller A.B. , Langmuir D. , Neretnieks I. 
Published: March 2011

ABSTRACTTo give due credit to the barrier of the far field geologic environment in many host media it is necessary to account for sorption processes. The ultimate impact of sorption modelling will be in helping to define the degree of confidence that may be placed on geochemical retardation occurring in this barrier. For those involved in site characterisation, systems' design, design implementation and regulation, this confidence is best derived from a combination of a fundamental phenomenological understanding of the sorption process with empirical observations of sorption in natural environments. Neither alone is adequate. By performing a few additional measurements during classical Ko experiments, the data necessary for the more fundamental models, such as that of double-layer or surface ionization and complexation, may also be provided. The basis of these models and their integration into broader performance analysis are outlined in the context of how this maximises confidence in the geologic barrier of critically concerned groups.
Verification and Validation of the Swift Model
Authors: Ward David S. , Reeves Mark , Duda Leonard E. 
Published: March 2011

ABSTRACTA number of tests have been performed, under controlled conditions, with the SWIFT model in order to complete its quality-assurance records. Some of these tests verify the numerical algorithms employed by the code implementation through comparison with analytical data. Other tests validate the processes addressed by the model through comparison with field data. These tests show good agreement between SWIFT and the reference data. In this paper several of the tests are highlighted.
Kinetics of Chemical Vapor Deposition of Copper from (β-diketonate)CuL Precursors
Authors: Jain Ajay , Chi K. M. , Kodas T. T. , Hampden-Smith M. J. 
Published: March 2011

ABSTRACTThe reaction kinetics of (hfac)CuL were examined in a warm-wall differential reactor. The data are consistent with neutral ligand L dissociation as rate limiting for (hfac)CuVTMS. A strong dependence of film resistivity on (hfac)CuVTMS pressure was observed. Selectivity for tungsten (W) surfaces in the presence of PECVD SiO2 was not observed for (hfac)CuVTMS under the conditions employed.
Interactions and Stability of Cu on CoSi2
Authors: Shy Y. -T. , Murarka S. P. , Sitaram A. R. , Ding P.-J. , Lanford W. A. 
Published: March 2011

ABSTRACTCopper is being investigated for application as multi-level interconnection metal in silicon ultra-large-scale integration (ULSI). On the other hand, COSi2 is being tested for application as contacts in sub-half micron ULSI circuits. Copper will thus be used on COSi2 to bring the electrical connection to the outside world. In this investigation we have therefore studied the interactions of copper with CoSi2 employing sheet resistance measurements (four-point probe), Rutherford back scattering (RBS), and X-ray diffraction (XRD). In addition the stability of the Schottky diodes, n-Si/CoS2/Cu, has been investigated as a function of the heat treatment in the range of room temperature to 600° C in argon-3% hydrogen mixture gas ambient. Both the measurements of the analytical and electrical characteristics show that Cu on n-Si/CoSi2 is stable at least up to a 30 minutes anneal at 600°C in argon-3% hydrogen medium. These results will be presented and discussed.
Thermal Stability of Cobalt Disilicide for Self-Aligned Silicide Applications
Authors: Chen W. , Lin J. , Banerjee S. , Lee J. 
Published: March 2011

ABSTRACTThe thermal stability of COSi2 for thermal budgets suitable for a self-aligned P+ gate MOSFET process using rapid thermal processing was studied. The substrate underlying the suicide has a major impact on suicide degradation. Suicides formed on as-deposited amorphous silicon films and on single crystal Si were found to be stable at least up to 1000°C, whereas suicides formed on as-deposited polysilicon (i.e. conventional polycide) began to degrade at annealing temperatures greater than 800°C. BF2-implant dosages of 1×1015 cm-2 to 2×1016 cm-2 at 20keV in the suicide were found to affect the conventional polycide significantly. With higher implant dosages, the degradation of the conventional polycide is retarded for a 900°C anneal. However, for thermally stable suicides i.e., suicides formed on as-deposited amorphous Si and on single crystal Si, a high dose 2×1016 cm-2 implant increases the sheet resistance slightly from 1.4 Ω/square to 1.6 Ω/square for suicides on as-deposited amorphous Si substrate, and from 1.3 Ω/square to 1.6 Ω/square for suicides on single crystal substrates. A model which involves spheroidization of the suicide, silicon incursion, and indiffusion of Co into polysilicon is proposed to explain the degradation behavior.
Nucleation and Morphology of TiSi2 on Si
Authors: Nemanich R. J. , Jeon Hyeongtag , Sukow C. A. , Honeycutt J. W. , Rozgonyi G. A. 
Published: March 2011

ABSTRACTThis study explores the nucleation and surface and interface morphology of TiSi2 films formed on Si (100) and (111) surfaces. Titanium suicide films were formed on atomically clean Si(111) and (100) surfaces by UHV deposition of Ti followed by in situ anneals. The TiSi2 formation process was characterized is itu using AES and LEED, and the interface structure was determined post preparation by HRTEM. The metastable C49 and stable C54 TiSi2 phases have been identified from Raman spectroscopy measurements. The islands were partially recessed into the substrate, and the shape and degree of recession was different for the islands on (111) and (100) substrates. On (111) substrates epitaxial islands were observed which exhibited different interface structures and epitaxial alignments. The contact angles of the islands were measured and the surface and interface energies of the different configurations were deduced. The mechanisms pertaining to island formation and interface morphology are described in terms of the wetting properties of a liquid-liquid system, with the effects of interface structures causing deviations from the model.
The Ideality of Spatially Inhomogeneous Schottky Contacts
Authors: Rau Uwe , Güttler Herbert H. , Werner Jürgen H. 
Published: March 2011

ABSTRACTWe present a new analytical theory of electronic transport for inhomogeneous Schottky contacts. Our model combines a novel method to solve Poisson's equation for the space charge region of an inhomogeneous contact with thermionic emission theory. We explain quantitatively the temperature and voltage dependences of the ideality factor n of current/voltage characteristics, and we are able to extract from experimental data information on the characteristic size of the inhomogeneities. Our measurements on polycrystalline and epitaxial Schottky contacts yield values in the range of 200–500nm as the typical size of inhomogeneities, covering a fraction of 0.1–1% of the total interface area.
Comparison of the Interface and Surface Morphologies of Zirconium and Titanium Silicides on Silicon
Authors: Sukow C. A. , Nemanich R. J. 
Published: March 2011

ABSTRACTThe morphology of zirconium suicide grown on Si(111) is investigated and compared to that of titanium suicide on Si(111) and (100). Zirconium was deposited on atomically clean silicon in UHV, and the suicide was formed by postdeposition annealing. ZrSi2 films formed from ≤100 Å of Zr deposited on Si(111) remained continuous for anneals of 400°C to 700°C. A film formed from 50 Å of Zr on Si(111) remained continuous for anneals up to 800°C, at which point the reappearance of a partial 7×7 LEED pattern indicated island formation. The interfaces of the films, studied by TME, show roughening after suicide formation. These results are compared and contrasted with the islanding behavior of titanium suicides, and analyzed in terms of a liquid-liquid model previously used with TiSi2.