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Comparison of F(2)-Based Gases for High-Rate Dry Etching of Si

Description: Four different F{sub 2}-based gases (SF{sub 6}, NF{sub 3}, PF{sub 5}, and BF{sub 3}) were examined for high rate Inductively Coupled Plasma etching of Si. Etch rates up to {approximately}8 {micro}m/min were achieved with pure SF{sub 6} discharges at high source power (1500W) and pressure (35mTorr). A direct comparison of the four feedstock gases under the same plasma conditions showed the Si etch rate to increase in the order BF{sub 3} < NF{sub 3} < PF{sub 5} < SF{sub 6}. This is in good correlation with the average bond energies of the gases, except for NF{sub 3}, which is the least strongly bound. Optical emission spectroscopy showed that the ICP source efficiently dissociated NF{sub 3}, but the etched Si surface morphologies were significantly worse with this gas than with the other 3 gases.
Date: March 31, 1999
Creator: Donahue, J.; Hahn, Y.B.; Hays, D.C.; Johnson, D.; Jung, K.B.; Lambers, E.S. et al.
Partner: UNT Libraries Government Documents Department

Selective, deep Si trench etching with dimensional control

Description: The recent development of a high-aspect ratio Si etch (HARSE) process has enabled the fabrication of a variety of Si structures where deep trench etching is necessary. The HARSE process relies on the formation of a sidewall etch inhibitor to prevent lateral etching of the Si structures during exposure to an aggressive SF{sub 6}/Ar plasma etch chemistry. The process yields highly anisotropic profiles with excellent dimensional control for high aspect ratio features. In this study, Si etch rates and etch selectivities to photoresist are reported as a function of chamber pressure, cathode rf-power, ICP source power, and gas flow. Si etch rates > 3 {micro}m/min with etch selectivities to resist > 75:1 were obtained. Lateral dimensional control, etch selectivities to SiO{sub 2} and Si{sub 3}N{sub 4}, and aspect ratio dependent etching (ARDE) will also be discussed.
Date: August 1, 1998
Creator: Shul, R.J.; Willison, C.G. & Zhang, L.
Partner: UNT Libraries Government Documents Department

Fluid Dynamics of Pressurized, Entrained Coal Gasifiers

Description: Pressurized, entrained gasification is a promising new technology for the clean and efficient combustion of coal. Its principle is to operate a coal gasifier at a high inlet gas velocity to increase the inflow of reactants, and at an elevated pressure to raise the overall efficiency of the process. Unfortunately, because of the extraordinary difficulties involved in performing measurements in hot, pressurized, high-velocity pilot plants, its fluid dynamics are largely unknown. Thus the designer cannot predict with certainty crucial phenomena like erosion, heat transfer and solid capture. In this context, we are conducting a study of the fluid dynamics of Pressurized Entrained Coal Gasifiers (PECGs). The idea is to simulate the flows in generic industrial PECGs using dimensional similitude. To this end, we employ a unique entrained gas-solid flow facility with the flexibility to recycle -rather than discard- gases other than air. By matching five dimensionless parameters, suspensions in mixtures of helium, carbon dioxide and sulfur hexafluoride simulate the effects of pressure and scale-up on the fluid dynamics of PECGS. Because it operates under cold, atmospheric conditions, the laboratory facility is ideal for detailed measurements. These activities are conducted with Air Products & Chemicals, Inc., which is a member of a consortium that includes Foster Wheeler and Deutsche Babcock Energie- und Umwelttechnik AG.
Date: December 31, 1997
Partner: UNT Libraries Government Documents Department

Moisture Sensor for Sulfur Hexafluoride (SF6)-filled Circuit Breakers

Description: Measurements at ORNL were made on the Kahn moisture sensor which Doble Engineering wants to evaluate for use in SF{sub 6} circuit breakers. Test conducted at ORNL indicate that vacuum conditions, as might be found in SF{sub 6} circuit breakers prior to filling with SF{sub 6}, could lead to significant changes in calibration, resulting in erroneous readings of moisture content. Similar effects might also be observed in cases where SF{sub 6} byproducts are present, due the reactivity of some of these byproducts with water.
Date: April 27, 2001
Creator: Sauers, I.
Partner: UNT Libraries Government Documents Department

Characterization of SF6/Argon Plasmas for Microelectronics Applications

Description: This report documents measurements in inductively driven plasmas containing SF{sub 6}/Argon gas mixtures. The data in this report is presented in a series of appendices with a minimum of interpretation. During the course of this work we investigated: the electron and negative ion density using microwave interferometry and laser photodetachment; the optical emission; plasma species using mass spectrometry, and the ion energy distributions at the surface of the rf biased electrode in several configurations. The goal of this work was to assemble a consistent set of data to understand the important chemical mechanisms in SF{sub 6} based processing of materials and to validate models of the gas and surface processes.
Date: March 1, 2002
Creator: HEBNER, GREGORY A.; ABRAHAM, ION C. & WOODWORTH, JOSEPH R.
Partner: UNT Libraries Government Documents Department

High-speed flow visualization of fluid instabilities

Description: The fluid instability resulting from the impulsive acceleration a thin, heavy gas layer embedded in a lighter gas is characterized through high-speed flow visualization. The shock-accelerated event occurs over the course of 1 ms. A laser sheet illuminates a plane of the gas layer and its evolution is recorded by a camera observing high-angle scattered light. Two sets of diagnostics were evaluated. These derived their time resolution either from gating the camera or pulsing the illumination source. The arbitrary inter-exposure timing associated with the gated camera was found to be significantly advantageous over the fixed intervals of the pulsed laser. The intensified, gated camera also placed more manageable requirements on the light source and provided sufficient data to measure the instability growth rates. However, the pulsed laser arrangement produced superior spatial resolution primarily due to the lack of an intensifier.
Date: December 1, 1996
Creator: Rightley, P.M. & Benjamin, R.F.
Partner: UNT Libraries Government Documents Department

Comparison of ARAC calculations with surface and airborne measurements for the ACE field trials

Description: These Atmospheric Collection Equipment (ACE) trials were sponsored by the Air Force Technical Applications Center (AFTAC) for the purpose of investigating specific tracer monitoring methods and equipment. Three different tracers (sulfur hexafluoride and two particulate tracers) were released simultaneously for each experiment. This document provides a brief summary of the sulfur hexafluoride modeling results for three of the remaining four ACE trials (the tracer plume from the fifth trial was not located by the monitoring teams and provided no tracer measurements for model comparison). This summary is followed by a discussion of model results for the two particulate tracers which were co-released with sulfur hexafluoride.
Date: November 1, 1996
Creator: Foster, K.T. & Pobanz, B.
Partner: UNT Libraries Government Documents Department

Verification of the integrity of barriers using gas diffusion

Description: In-situ barrier materials and designs are being developed for containment of high risk contamination as an alternative to immediate removal or remediation. The intent of these designs is to prevent the movement of contaminants in either the liquid or vapor phase by long-term containment, essentially buying time until the contaminant depletes naturally or a remediation can be implemented. The integrity of the resultant soil-binder mixture is typically assessed by a number of destructive laboratory tests (leaching, compressive strength, mechanical stability with respect to wetting and freeze-thaw cycles) which as a group are used to infer the likelihood of favorable long-term performance of the barrier. The need exists for a minimally intrusive yet quantifiable methods for assessment of a barrier`s integrity after emplacement, and monitoring of the barrier`s performance over its lifetime. Here, the authors evaluate non-destructive measurements of inert-gas diffusion (specifically, SF{sub 6}) as an indicator of waste-form integrity. The goals of this project are to show that diffusivity can be measured in core samples of soil jet-grouted with Portland cement, validate the experimental method through measurements on samples, and to calculate aqueous diffusivities from a series of diffusion measurements. This study shows that it is practical to measure SF{sub 6} diffusion rates in the laboratory on samples of grout (Portland cement and soil) typical of what might be used in a barrier. Diffusion of SF{sub 6} through grout (Portland cement and soil) is at least an order of magnitude slower than through air. The use of this tracer should be sensitive to the presence of fractures, voids, or other discontinuities in the grout/soil structure. Field-scale measurements should be practical on time-scales of a few days.
Date: June 1, 1997
Creator: Ward, D.B. & Williams, C.V.
Partner: UNT Libraries Government Documents Department

A field study evaluation of short-term refined Gaussian dispersion models

Description: A tracer study was conducted at the Duke Forest Site in Chapel Hill, North Carolina in January, 1995 to evaluate the ability of three short-term refined Gaussian dispersion models to predict the fate of volume source emissions under field study conditions. Study participants included the American Petroleum Institute (API), the US Environmental Protection Agency (EPA), the US Department of Energy (DOE), the University of North Carolina at Chapel Hill (UNC), and private consulting firms. The models evaluated were Industrial Source Complex--Short Term versions 2 and 3 (ISC2, ISC3) and the American Meteorological Society (AMS) Environmental Protection Agency (EPA) Regulatory Model Improvement Committee (AERMIC) model, AERMOD. All three models are based on the steady-state Gaussian plume dispersion equation, which predicts concentrations at downwind receptor locations when integrated over the distance between the source and receptor. Chemicals were released at known rates and measurements were taken at various points in the study field using Tedlar bag point sampling and open-path Fourier Transform infrared (OP-FTIR) monitoring. The study found that ISC and AERMOD underpredicted the measured concentrations for each dataset collected in the field study. ISC and AERMOD each underpredicted the OPFTIR dataset by a factor of approximately 1.6. ISC underpredicted the Tedlar{reg_sign} dataset by approximately 2.1, while AERMOD underpredicted by a factor of approximately 2.6. Regardless of source configuration or measurement technique used, under-prediction with respect to the measured concentration was consistently observed. This indicates that safety factors or other corrections may be necessary in predicting contaminant concentrations over the distances examined in this study, i.e., in the near field of less than 200 meters.
Date: December 31, 1996
Creator: Piper, A.
Partner: UNT Libraries Government Documents Department

Effects of numerical methods on comparisons between experiments and simulations of shock-accelerated mixing.

Description: We consider the detailed structures of mixing flows for Richtmyer-Meshkov experiments of Prestridge et al. [PRE 00] and Tomkins et al. [TOM 01] and examine the most recent measurements from the experimental apparatus. Numerical simulations of these experiments are performed with three different versions of high resolution finite volume Godunov methods. We compare experimental data with simulations for configurations of one and two diffuse cylinders of SF{sub 6} in air using integral measures as well as fractal analysis and continuous wavelet transforms. The details of the initial conditions have a significant effect on the computed results, especially in the case of the double cylinder. Additionally, these comparisons reveal sensitive dependence of the computed solution on the numerical method.
Date: January 1, 2002
Creator: Rider, William; Kamm, J. R. (James R.); Tomkins, C. D. (Chris D.); Zoldi, C. A. (Cindy A.); Prestridge, K. P. (Katherine P.); Marr-Lyon, M. (Mark) et al.
Partner: UNT Libraries Government Documents Department

Statistical comparison between experiments and numerical simulations of shock-accelerated gas cylinders

Description: We present detailed spatial analysis comparing experimental data and numerical simulation results for Richtmyer-Meshkov instability experiments of Prestridge et al. and Tomkins et al. These experiments consist, respectively, of one and two diffuse cylinders of sulphur hexafluoride (SF{sub 6}) impulsively accelerated by a Mach 1.2 shockwave in air. The subsequent fluid evolution and mixing is driven by the deposition of baroclinic vorticity at the interface between the two fluids. Numerical simulations of these experiments are performed with three different versions of high resolution finite volume Godunov methods, including a new weighted adaptive Runge-Kutta (WARK) scheme. We quantify the nature of the mixing using using integral measures as well as fractal analysis and continuous wavelet transforms. Our investigation of the gas cylinder configurations follows the path of our earlier studies of the geometrically and dynamically more complex gas 'curtain' experiment. In those studies, we found significant discrepancies in the details of the experimentally measured mixing and the details of the numerical simulations. Here we evaluate the effects of these hydrodynamic integration techniques on the diffuse gas cylinder simulations, which we quantitatively compare with experimental data.
Date: January 1, 2002
Creator: Rider, William; Kamm, J. R. (James R.); Zoldi, C. A. (Cindy A.) & Tomkins, C. D. (Chris D.)
Partner: UNT Libraries Government Documents Department

Sulfur isotope relative ratios determined by mass spectrometry

Description: BS>The ratio of the sulfur isotope ratio, /sup 34/S/(/sup 32/S + /sup 32/ S), in a sample of sulfur hexafluoride to that in an isotopically different sample (relative ratio) is determined to plus or minus 0.00003 (standard deviation) at relative ratios of 1.003-1.007 and near-natural isotopic abundances. (auth)
Date: December 1, 1973
Creator: Howard, O.H.
Partner: UNT Libraries Government Documents Department

Development of the SEAtrace{trademark} barrier verification and validation technology. Final report

Description: In-situ barrier emplacement techniques and materials for the containment of high-risk contaminants in soils are currently being developed by the Department of Energy (DOE). Because of their relatively high cost, the barriers are intended to be used in cases where the risk is too great to remove the contaminants, the contaminants are too difficult to remove with current technologies, or the potential movement of the contaminants to the water table is so high that immediate action needs to be taken to reduce health risks. Assessing the integrity of the barrier once it is emplaced, and during its anticipated life, is a very difficult but necessary requirement. Science and Engineering Associates, Inc., (SEA) and Sandia National Laboratories (SNL) have developed a quantitative subsurface barrier assessment system using gaseous tracers in support of the Subsurface Contaminants Focus Area barrier technology program. Called SEAtrace{trademark}, this system integrates an autonomous, multi-point soil vapor sampling and analysis system with a global optimization modeling methodology to locate and size barrier breaches in real time. The methodology for the global optimization code was completed and a prototype code written using simplifying assumptions. Preliminary modeling work to validate the code assumptions were performed using the T2VOC numerical code. A multi-point field sampling system was built to take soil gas samples and analyze for tracer gas concentration. The tracer concentration histories were used in the global optimization code to locate and size barrier breaches. SEAtrace{trademark} was consistently able to detect and locate leaks, even under very adverse conditions. The system was able to locate the leak to within 0.75 m of the actual value, and was able to determine the size of the leak to within 0.15 m.
Date: August 1, 1998
Creator: Dunn, S.D.; Lowry, W.; Walsh, R.; Rao, D.V. & Williams, C.
Partner: UNT Libraries Government Documents Department

Fluid dynamics of pressurized, entrained coal gasifiers. Tenth quarterly technical progress report, April 1, 1996--June 30, 1996

Description: Pressurized, entrained gasification is a promising new technology for the clean and efficient combustion of coal. Its principle is to operate a coal gasifier at a high inlet gas velocity to increase the inflow of reactants, and at an elevated pressure to raise the overall efficiency of the process. Unfortunately, because of the extraordinary difficulties involved in performing measurements in hot, pressurized, high-velocity pilot plants, its fluid dynamics are largely unknown. Thus the designer cannot predict with certainty crucial phenomena Re erosion, heat transfer and solid capture. In this context, we are conducting a study of the fluid dynamics of Pressurized Entrained Coal Gasifiers (PECGs). The idea is to simulate the flows in generic industrial PECGs using dimensional similitude. To this end, we employ a unique entrained gas-solid flow facility with the flexibility to recycle -rather than discard- gases other than air. By matching five dimensionless parameters, suspensions in mixtures of helium, carbon dioxide and sulfur hexafluoride simulate the effects of pressure and scale-up on the fluid dynamics of PECGs. Because it operates under cold, atmospheric conditions, the laboratory facility is ideal for detailed measurements.
Date: October 1, 1996
Creator: Louge, M.Y.
Partner: UNT Libraries Government Documents Department

Investigation of S{sub 2}F{sub 10} production and mitigation in compressed SF{sub 6}-insulated power systems. Final report, Volume 1: Executive summary

Description: A CRADA was established in 1991 to study the production and mitigation of S{sub 2}F{sub 10}, one of a number of toxic by-products formed by electrical discharges in the insulating gas SF{sub 6}. Since compressed SF{sub 6} is extensively used as an insulation and current interruption medium in electric power equipment, ensuring the safe operation and maintenance of this equipment is an important issue for utilities, government agencies, and manufacturers. Each of the three research laboratories developed a highly sensitive detection method for S{sub 2}F{sub 10}: (1) Oak Ridge National Laboratory, gas chromatography/cryogenic enrichment (less than 10 ppbv sensitivity); (2) National Institute of Standards and Technology, gas chromatography/mass spectrometry/thermal conversion (less than 10 ppbv); (3) Ontario Hydro Technologies, Fourier transform infrared spectrometry (FTIR) (less than 100 ppbv). Studies showed that S{sub 2}F{sub 10} can be produced in the laboratory by corona, spark, and power arc discharges and that the production rates for each type of discharge decrease in that same respective order. In power arcs, SOF{sub 2} is by far the dominant species. The field survey provided baseline data and demonstrated the feasibility of taking and analyzing field samples using the techniques developed under this CRADA. It was found that in power arcs the amount of S{sub 2}F{sub 10} produced is relatively insignificant compared to the amount of the SOF{sub 2} produced. The knowledge gained from this CRADA should also be beneficial for the development of routine procedures for gas analysis, so that analysis of the decomposition products of SF{sub 6} will become a standard method for addressing the issues of health and safety, equipment reliability and aging, and diagnostics for GIS (Gas-Insulated Substations).
Date: October 1, 1995
Creator: Sauers, I.; Griffin, G.D.; James, D.R.; Brunt, R.J. Van; Olthoff, J.K.; Stricklett, K.L. et al.
Partner: UNT Libraries Government Documents Department

Plasma cleaning techniques and future applications in environmentally conscious manufacturing

Description: Plasmas have frequently been used in industry as a last step surface preparation technique in an otherwise predominantly wet-etch process. The limiting factor in the usefulness of plasma cleaning techniques has been the rate at which organic materials are removed. Recent research in the field of plasma chemistry has provided some understanding of plasma processes. By controlling plasma conditions and gas mixtures, ultra-fast plasma cleaning and etching is possible. With enhanced organic removal rates, plasma processes become more desirable as an environmentally sound alternative to traditional solvent or acid dominated process, not only as a cleaning tool, but also as a patterning and machining tool. In this paper, innovations in plasma processes are discussed including enhanced plasma etch rates via plasma environment control and aggressive gas mixtures. Applications that have not been possible with the limited usefulness of past plasma processes are now approaching the realm of possibility. Some of these possible applications will be discussed along with their impact to environmentally conscious manufacturing.
Date: July 1, 1995
Creator: Ward, P.P.
Partner: UNT Libraries Government Documents Department

Engineering task plan for determining breathing rates in singleshell tanks using tracer gas

Description: The testing of single shell tanks to determine breathing rates. Inert tracer gases helium, and sulfur hexafluoride will be injected into the tanks AX-103, BY-105, C-107 and U-103. Periodic samples will be taken over a three month interval to determine actual headspace breathing rates.
Date: April 2, 1997
Creator: Andersen, J.A.
Partner: UNT Libraries Government Documents Department

LDRD 93-ERP-166 Final report

Description: In this article, recent measurements made with LIFTIRS, the Livermore Imaging Fourier Transform Infrared Spectrometer, are presented. The experience gained with this instrument has produced a variety of insights into the tradeoffs-between signal to noise ratio (SNR), spectral resolution and temporal resolution for time multiplexed Fourier transform imaging spectrometers. This experience has also clarified the practical advantages and disadvantages of Fourier transform hyperspectral imaging spectrometers regarding adaptation to varying measurement requirements on SNR vs spectral resolution, spatial resolution and temporal resolution.
Date: July 1, 1995
Creator: Bennett, C.L.; Carter, M.R.; Fields, D.J. & Lee, F.D.
Partner: UNT Libraries Government Documents Department

Evaluation of possible biological effects from exposure to gaseous SF{sub 6} breakdown products

Description: A variety of chemical byproducts including SOF{sub 2}, SO{sub 2}F{sub 2}, SF{sub 4}, HF, SO{sub 2}, etc. are produced at varying concentrations by electrical arcs, sparks or corona discharge in SF{sub 6}; most of the byproducts are toxic to some degree. Using a cell culture system, we have studied the toxicity of individual byproduct gases, as well as electrically decomposed SF{sub 6}. The toxic potency of various byproducts can be compared, using this cellular assay. The animal toxicological data for these gases, although sparse, is also reviewed. The rationale for selection of various byproduct gases as monitors for evaluating the hazard potential of decomposed SF{sub 6} is discussed.
Date: June 1, 1993
Creator: Griffin, G.D.; Sauers, I. & James, D.R.
Partner: UNT Libraries Government Documents Department

Reactor Room Experimental SF6 Tests to Determine Probable Stack Activity Response to Radioactive Releases

Description: This study was performed to obtain information that could be useful for obtaining an early estimate of the probable total stack activity monitor response in the event of an accidental release of radioactive activity in the process room.
Date: August 19, 2002
Creator: Cooper, R. E.
Partner: UNT Libraries Government Documents Department

Simulations of the ASCOT Brush Creek data by a nested-grid, second-moment turbulence-closure model and a kernel concentration estimator

Description: Yamade and Bunker (1986) demonstrated that a three-dimensional hydrodynamic model, HOTMAC (Higher Order Turbulence Model for Atmospheric Circulations) reproduced nocturnal drainage flows, morning transition and convective upvalley and upslope flows observed during the 1982 ASCOT (Atmospheric Studies in COmplex Terrain) field campaign in Brush Creek, Colorado. We also showed that a Monte Carlo statistical diffusion model, RAPTAD (RAndom Particle Transport And Diffusion) driven by the outputs (mean and turbulence variables) from HOTMAC simulated well the structure of an SF6 tracer plume and obtained a vertical profile of concentration similar to the one observed. A ''Kernel'' density estimator is used in this study where each particle represents a center of a puff. In this study, the concentration was recomputed by applying the Gaussian kernel estimator. A total of only 900 particles were released. The vertical profile of the modeled SF6 concentration averaged over one hour between 6 and 7 a.m. at a site near the mouth of Brush Creek was compared with observation. The modeled and observed concentrations agreed well although the modeled values were slightly smaller than the observations for the first 250 m above the ground.
Date: January 1, 1987
Creator: Yamada, Tetsuji; Bunker, S. & Niccum, E.
Partner: UNT Libraries Government Documents Department

Perforated monolayers. Progress report, July 1, 1990--December 31, 1992

Description: Goal of this research program is to create ultrathin organic membranes that possess uniform and adjustable pores ( < 7{angstrom} diameter). Such membranes are expected to possess high permeation selectivity (permselectivity) and high permeability, and to provide the basis for energy-efficient methods of molecular separation. Work carried out has demonstrated feasibility of using ``perforated monolayer``-based composites as molecular sieve membranes. Specifically, composite membranes derived from Langmuir-Blodgett multilayers of the calix[6]arene-based surfactant shown below plus poly[l-(trimethylsilyl)-l-propyne] (PTMSP) were found to exhibit sieving behavior towards He, N{sub 2} and SF{sub 6}. Results of derivative studies that have also been completed are also described in this report.
Date: December 1, 1992
Creator: Regen, S. L.
Partner: UNT Libraries Government Documents Department