bluuebunny/crossref_metadata_2025 huggingface dataset:
Microstructural Characterization of Submerged Arc Weld Metals
Authors: Lawless KR , Pavinich WA , Lowe AL
Published: December 2008

This paper presents the results of a detailed microstructural evaluation of Linde 80 submerged arc weld metals typically found in Babcock and Wilcox 177FA Class reactor vessels. Optical metallography was performed on Linde 80 weld metals to characterize the grain structure, and scanning electron microscopy (SEM) was used to characterize the fracture surfaces. These weld metals have a tempered bainitic structure with large amounts of manganese rich inclusions.

Analytical transmission electron microscopy (TEM) was used to characterize the carbides, coarse (0.1- to 2.0-μm) inclusions, and fine (2- to 50-nm) precipitates. Thin foil and extraction techniques were used to characterize particle morphology while convergent beam electron diffraction (CBED) and energy dispersive X-ray (EDS) techniques were carried out to identify the particle chemical composition and crystal structure. These results are compared with published results from simulated reactor vessel welds found in the in-situ annealing program sponsored by the Electric Power Research Institute (EPRI).
Irradiation Embrittlement of Advanced Pressure Vessel Steels
Authors: Sivaramakrishnan KS , Chatterjee S , Anantharaman S , Viswanathan UK , Balakrishnan KS , Roy PR
Published: December 2008

Seven commercial steels in the form of plate, forging, or weldments supplied by Japan, France, and the Federal Republic of Germany to the International Atomic Energy Agency (IAEA) Co-ordinated Research Programme on “Analysis of the Behaviour of Advanced Reactor Pressure Vessel Steels under Neutron Irradiation” were irradiated at 290°C to a nominal fast fluence of 1 × 1019 n/cm2 (>1 MeV) to evaluate the embrittlement sensitivity of these steels under neutron irradiation. These steels were basically of ASTM Types A533 and A508 (Unified Numbering System [UNI] K12521 and K13502) and their weldments, which had extra low copper and phosphorous contents. The copper and phosphorous contents in these individual steels varied from 0.01 to 0.07 wt% and 0.007 to 0.015 wt%, respectively. The nickel contents in these steels varied from 0.56 to 0.93 wt%.

The scope of this study was mainly to evaluate the changes in the notch ductility, tensile properties, and hardness as caused by fast neutron irradiation. This paper reports the results obtained on these advanced pressure vessel steels in the form of base metal, weldments, and weld heat affected zones. The results indicated that these advanced steels were practically insensitive to fast neutron induced embrittlement. The relative embrittlement of these steels were further analyzed to examine the contribution of nickel in presence of copper in causing embrittlement. The impact test results indicated that threshold amounts of 0.04-wt% copper and 0.7-wt% nickel would perhaps be required to cause relatively enhanced embrittlement in these steels, confirming thereby that nickel in presence of copper can cause enhanced fast neutron induced embrittlement.
A Study of Radiation Induced Voids and Precipitates and Their Annealing Behavior by Small-Angle Neutron Scattering
Authors: Ukpong IE , Krawitz AD , Mildner DFR , Leighly HP
Published: December 2008

We have studied the annealing response of an irradiated pressure vessel steel, ASTM A302B, using small-angle neutron scattering. We have used two sets of specimens in this study, one irradiated to a fluence of 3 to 4 × 1019 n/cm2 at 288°C, and the other a parallel set of the same steel in the unirradiated condition. We have annealed specimens from each set isothermally at 300, 350, 400, and 450°C for increasing periods of time up to five h, and have observed the variations in the SANS spectra in both irradiated and unirradiated specimens. Changes in the small-angle neutron scattering (SANS) spectra commence at 300°C for the unirradiated material and at 400°C in the irradiated material. The observed response suggests that the changes are caused basically by the precipitation of copper out of solid solution in α-iron during the annealing of unirradiated and irradiated specimens; in the case of the irradiated specimens, the release of damage-induced defects enhances the precipitation of the copper.
Damage Rate and Spectrum Effects in Ferritic Steel ΔNDTT Data
Authors: Simons RL
Published: December 2008

A model was developed for irradiation-induced hardening in pressure vessel steels by cascade-induced nucleation and free defect diffusion of copper to coherent copper clusters. The model was used as a functional framework for fitting data on macroscopic property change (ΔNDTT) as a function of damage dose and dose rate. Several defect cross sections having different neutron energy dependences were tried. The cross section for Frenkel pair production, based on resistivity measurements at 4 K, was found to give a comparable or slightly better fit to the data than dpa. Damage rate is an important parameter to consider in correlation of ΔNDTT data, and damage rate can affect the nucleation as well as the growth of the copper precipitation.
Current Limitations of Trend Curve Analysis for the Prediction of Reactor PV Embrittlement
Authors: Gold R , McElroy WN
Published: December 2008

In operating light water reactor (LWR) commercial power plants, neutron radiation induces embrittlement of the pressure vessel (PV) and its support structures. As a consequence, LWR-PV integrity is a primary safety consideration. LWR-PV integrity is a significant economic consideration, since the PV and its support structures are nonreplaceable power plant components and embrittlement of these components can, therefore, limit the effective operating lifetime of the plant.

To define the effects of neutron radiation damage on LWR pressure-temperature operating limits and to assess fracture toughness of power reactor PV, trend curves for the prediction of PV embrittlement have been developed. These trend curves are very general PV embrittlement curves that are used to evaluate current PV status as well as to predict the future state of the PV. In such trend curves, the two main measures of radiation damage are the adjusted reference nil-ductility temperature ARTNDT(RTNDT initial + ΔRTNDT) and the decrease in upper-shelf energy level determined from Charpy V notch impact tests. Current measures of neutron exposure most commonly used in trend curve analyses are fluence >1 MeV and displacements per atom (dpa) in iron.

Since trend curves play such a crucial role in the assessment of PV embrittlement of operating commercial LWR power plants, a critical appraisal of trend curve analysis is essential. To this end, current limitations in trend curve analysis for the prediction of reactor PV embrittlement are examined. It is concluded that a number of systematic effects can arise because environmental differences exist between test reactors, surveillance capsule locations, and the actual irradiation conditions that accure within the PV of an operating LWR commercial power plant. An irradiation test program is advanced to investigate these systematic effects and to produce the requisite data needed to correct for such systematic biases in trend curve analysis.
Fission Fragment Damage in Ceramic Nuclear Fuels
Authors: Matsui H , Horiki M , Tamaki M , Kirihara T
Published: December 2008

Post-irradiation examinations of several ceramic nuclear fuels are summarized, emphasizing the identification and characterization of fission induced defects. The lattice parameter and electrical resistivity were significantly altered with fission damage in all fuels. A remarkable reduction, however, was found in the irradiation induced changes of both physical properties in uranium dioxide (UO2), uranium nitrite (UN), and uranium sesquicarbide (U2C3) at high fission doses, probably because of a preferential annihilation of extended defects in the damage process. An effect of the extended defects in irradiated single crystalline UC was a greater increased resistivity at low temperature, indicating a contribution of interstitial-type defects. The irradiation induced physical properties, on the other hand, were annealed out, within a few recovery steps in all the fuels, exhibiting some dependence on the extent of the fission damage. It was of great interest that a drastic change was observed in the magnetic property changes in some magnetic substances, such as uranium monosulfide (US) and UN. All the magnetic parameters changed with fission damage and recovered to the original values in successive annealing processes.
Hydrogen Control in the Handling, Shipping, and Storage of Wet Radioactive Waste
Authors: Henrie JO , Flesher DJ
Published: December 2008

Under contract with the Department of Energy, Rockwell Hanford Operations (Rockwell) conducted a series of studies related to Three Mile Island (TMI) post loss of coolant accident (LOCA) waste handling safety. The key factor in these studies was the control of radiolytic gases, specifically hydrogen and oxygen.

Success was achieved in the prediction of gas generation rates and in the development and application of gas control technologies. That success led to the publication of a “lessons learned” document, providing (1) a step-by-step guide in evaluating potential radiolysis hazards in waste storage and shipment activities and (2) a set of corrective options for preventing or controlling the hazards. The evaluation steps developed in the document are outlined in a functional logic diagram. Several procedures are described which provide safe and effective controls for hydrogen and oxygen levels in containers scheduled for shipment or interim storage. A method is provided to pre-evaluate each control option and select the most cost effective procedure for each case.
Photobleaching Effects on Radiation-Induced Loss for Silica Glass Image Fiber
Authors: Hayashi S , Wada Y , Chigusa Y , Fujiwara K , Hattori Y , Matsuda Y
Published: December 2008

The photobleaching effect (annealing effect on light absorption by light energy) on silica glass image fiber was investigated. We evaluated photobleaching characteristics using He-Cd laser, a xenon lamp, and a D2 lamp as photobleaching light sources. Fibers were irradiated at two levels of dosage, 300 rad/h and 104 rad/h. The thermal effect on photobleaching was also evaluated by comparing the effect at 28°C and that at 70°C. The investigations demonstrated the superiority of the xenon lamp and thermal dependency of photobleaching. Furthermore through xenon lamp bleaching, we have succeeded in elongating the usable life span of image fiber in a 300-rad/h gammaray environment to more than five times that for nonbleached fiber.
Irradiation Devices for Reactor Materials: Results Obtained from Irradiated Lithium Aluminate at the OSIRIS Reactor
Authors: Lefevre F , Thevenot G , Rasneur B , Botter F
Published: December 2008

The study of radiation behavior is of prime importance in the investigation of fusion reactor materials. With this purpose, the “Services des Piles de Saclay” (SPS) has been using the experimental OSIRIS pool reactor, having a nominal power of 70 MW, to develop irradiation devices. The devices enable (1) the study of the crack growth on a sample under alternative stress in a neutron flux, (2) the study of stress relaxation on materials under irradiation, (3) the study of creep and growth of cylindrical test pieces in a neutron flux, (4) the irradiation of large amounts of protection ceramics of fusion reactors so as to characterize their mechanical properties, and (5) the irradiation of lithium containing ceramics, which are possible materials for the breeding blanket of a fusion reactor. The last device was used in the ALICE 1 experiment, carried out in collaboration with the “Division d'Etudes de Séparation Isotopique et de Chimie Physique” (DESICP), for the irradiation of 130 specimens of γ LiAlO2, of natural lithium 6 abundance and of various textures. The unclad samples were irradiated at 400 and 600°C, in a maximum fast flux of 2 × 1014 n · cm−2 · s−1 (E > 1 MeV) and maximum perturbed thermal flux 6 × 1013 n · cm−2 · s−1 for 26 days (from 16 Oct. to 13 Nov. 1984). The amount of tritium generated was 330 Ci. The 6Li burnup could amount to 15 to 20%. The first post irradiation examinations showed general good behavior of the samples. There were no changes in the dimensions of the samples, nor significant thermal conductivity variations. Retained tritium and helium amounts varied depending on the ceramic texture and irradiation temperature. Small variations in the sound velocity and cracks were observed only in two 600°C levels, corresponding to containers that received mechanical shocks during the dismantling of the experimental device.
Changes in Surface Morphology and Microcrack Initiation in Polymers Under Simultaneous Exposure to Stress and Fast Atom Bombardment
Authors: Michael RS , Frank S , Stulik D , Dickinson JT
Published: December 2008

We present studies of the changes in surface morphology due to simultaneous exposure of polymers to stress and fast atom bombardment. The polymers examined were Teflon,3 Kapton,3 Nylon,3 and Kevlar-49.3 The incident particles were 6 keV xenon atoms. We show that in the presence of mechanical stress these polymers show topographical changes at particle doses considerably lower than similar changes produced on unstressed material. Applied stress also promotes the formation of surface microcracks which could greatly reduce the mechanical strength of the material.
Operating Experience at the Los Alamos Spallation Radiation Effects Facility at LAMPF
Authors: Sommer WF , Lohmann W , Graf K , Taylor IK , Chavez RM
Published: December 2008

Operation of a new irradiation facility at the beam stop (Target Station A-6) at the Clinton P. Anderson Los Alamos Meson Physics Facility (LAMPF) began in May 1985. The facility is now fully operational. A closed-loop water system, a closed-loop helium system, remote handling procedures for activated materials, experiment change-out procedures, and experiment control equipment are all in place.

Experience dictated a change in irradiation capsules from a system that used metal seals to a system that is completely welded. The seals were found to be unreliable and difficult to replace by remote means.

Several materials have been irradiated in the direct 760-MeV proton beam. Material property changes as well as helium production in a variety of materials are being investigated.

A special sample holder that can accommodate transmission electron microscopy (TEM) specimens, isolate them from the cooling medium, maintain fixed temperature, and retain essentially a stressfree state has been developed. Remote handling retrieval of these specimens is being developed.

Activation foil measurements are being made to determine the secondary particle flux and spectrum (charged particles and neutrons) that result from interaction of the direct proton beam with targets at the beam stop. Twelve independent irradiation ports, each with an irradiation volume of 0.12 by 0.25 by 0.50 m, are available for exposing material to this particle flux, primarily neutrons. Two irradiations were completed in this area during the period May through December 1985. The neutron spectrum here resembles a fission spectrum with the addition of neutrons in the MeV energy range (high-energy tail). The maximum neutron flux is about 6 × 1017 n/m2 s at one of the 12 ports and drops by a factor of about 10 as a minimum at another of the 12 ports.

Three independent ports for proton irradiations are in place. Each has an irradiation volume of about 150 cm3. The proton beam has a Gaussian intensity profile; the maximum proton flux at the center of the beam is 1.2 × 1014 protons/cm2 · s. The beam spot has a diameter of approximately 5 cm at 2σ. Four irradiations were completed in this area during the period May through December 1985.
Additional Measurements of the Radiation Environment at the Los Alamos Spallation Radiation Effects Facility at LAMPF
Authors: Davidson DR , Reedy RC , Greenwood LR , Sommer WF , Wechsler MS
Published: December 2008

Foil activation dosimetry experiments were conducted in a “rabbit” system at the completed Los Alamos Spallation Radiation Effects Facility (LASREF). The “rabbit” system contains four tubes spaced radially outward 0.12, 0.18, 0.27, and 0.38 m off beam centerline. Foils were irradiated for 3 to 62 h to measure the neutron flux and energy spectrum radially from beam centerline, along the beamline, and the effect of the isotope production (IP) target loadings on the neutron flux in the neutron irradiation locations. Irradiations showed a decrease in the radial flux by a factor of 6 in 0.15 m of iron outside the IP targets. An enhancement was seen in the 24-keV energy region outside 0.15 m. There was little difference in the shape of the spectra outside the IP targets and the beam stop with the exception of the high energy tail (energies above 20 MeV). The decrease in the high energy tail outside the beam stop is due to the degradation of the energy of the proton beam in the IP targets. Irradiations outside the beam stop with zero and eight IP targets gave the same spectral shape with the exception of the high energy tail. The magnitude of the integral flux decreased by a factor of two when eight IP targets were present. Irradiations with five “rabbits” stacked on top of each other showed no difference in the integral flux below, on and above beam centerline.
Measurements of 10B(n,He) Reaction Rates in a Mockup Control Rod in ZPPR
Authors: Brumbach SB , Collins PJ , Oliver BM
Published: December 2008

Results are reported for 10B(n,He) reaction rate measurements inside B4C pellets contained in a mockup control rod in the Zero Power Plutonium Reactor (ZPPR). The helium accumulation fluence monitor (HAFM) technique was used, with absolute amounts of helium determined by isotope-dilution mass spectrometry. Rates of 235U fission were measured in foils irradiated between B4C pellets. Fission rate measurements used gamma ray counting techniques. Both helium production and fission rates were calculated using three-dimensional nodal transport methods. Measured helium production rates decreased about 18% within the first 63 mm of the pins, and decreased 10 to 12% going from outer to inner pins in this small, 16-pin control assembly. The calculated and measured reaction rate profiles agreed within the 1 to 2% measurement uncertainties. Helium production rates were underestimated by calculations by about 8%.
General Principles of Sampling
Authors: Kratochvil B
Published: December 2008

In atmospheric measurements, the sampling operation is often a major source of error. This error may be reduced by consideration of the distribution pattern of the substance being measured, and the statistical principles of that pattern. From this information, guidelines as to the number, size, and location of the samples can be formulated. These guidelines should be tempered, however, with judgment and experience.
Indoor Air Quality Measurements
Authors: Fortmann RC , Nagda NL , Koontz MD
Published: December 2008

Measurements of contaminants and other parameters in indoor environments present unique challenges to researchers because of the variety of building types to be monitored, the presence of occupants, the large number of potential contaminant sources, and the high degree of temporal and spatial variation of contaminant concentrations.

Selection of monitors and sampling methods for indoor air quality monitoring requires careful consideration of numerous factors. Considerations related to the design of the indoor monitoring program as well as factors related to monitor and sampler performance must be evaluated. Practical considerations related to sampling in occupied environments play an important role in the selection of measurement devices.

This paper discusses general concepts that should be considered in the selection of instrumentation for monitoring indoor air quality. Specific instrumentation and methods are not reviewed, but examples of instrumentation and monitoring approaches are provided for researchers unfamiliar with indoor air quality monitoring.
Precision and Accuracy Assessment Derived from Calibration Data
Authors: Rook HL
Published: December 2008

During the past ten years, the importance of assessing the precision and the accuracy of data derived from standard methods has become recognized. Both the American Society for Testing and Materials (ASTM) and the U.S. Environmental Protection Agency (EPA) have developed policies requiring precision and accuracy assessment for methods before they are designated as standard methods or reference methods. The difficulty in implementing these policies is not in developing a meaningful uncertainty estimate for a given method, it is in separating the random from the systematic components of the error. In this paper, a method of separating error components into precision and bias is given. The method uses calibration data taken repeatedly at a fixed point using a standard whose total uncertainty is small compared to the uncertainty of the measurement method.
The EPA's Role in the Quality Assurance of Ambient Air Pollutant Measurements
Authors: Puzak JC , McElroy FF
Published: December 2008

Ensuring the quality and integrity of ambient air pollution measurements encompasses a wide variety of activities and procedures. The U.S. Environmental Protection Agency's (EPA's) roll in the quality assurance of monitoring data is to assist monitoring agencies by providing those quality assurance services or functions that (1) are common to most monitoring agencies and would be uneconomical to duplicate in each agency's program; (2) are too costly for individual monitoring agencies to carry out; (3) need to be uniform across the nation's monitoring agencies to facilitate universal data interpretation, comparison, evaluation, and common analysis; or (4) are more appropriately derived from a source independent from the monitoring agency. These functions are focused in three principle areas: (1) standardized and validated monitoring methods, (2) air monitoring guidance and technical assistance, and (3) assessment of the quality of monitoring data being obtained. These functions are discussed along with overview descriptions and summaries of results of specific EPA quality assurance programs including reference and equivalent methods, the Quality Assurance Handbook and other guidance documents, availability of various pollutant concentration standards, and assessment and reporting of the precision and accuracy of air monitoring data.
Parts-Per-Billion Gaseous Mixtures: A New Challenge
Authors: Denyszyn RB , Sassaman T
Published: December 2008

Specialty gas manufacturers are being driven by regulatory requirements to manufacture low concentration gaseous mixtures of various air pollutants. This paper describes some of the basic difficulties incurred in preparing parts-per-billion (ppb) concentrations of various volatile organics such as pyridine, Freon® 113, Freon® 114, vinylidene chloride, toluene, 1,4 dioxane, acetone, chlorobenzene, acetonitrile, and methylethyl ketone. Concentrations range from 10 to 150 ppb. During the manufacturing and certification of these mixtures, several problems were encountered, including:

1. Ghost peaks due to gas chromatographic system background.

2. Adsorption of compounds in the analytical system as well as on cylinder walls.

3. Difficulties in preparation of primary standards for calibration.

4. Contamination of cylinders, even after special cleaning and preparation.

It is therefore imperative that when purchasing such mixtures, a certificate of analysis as well as a copy of the chromatographs be provided to the user.
The U. S. Army's New Industrial Hygiene Sampling Guide
Authors: Belkin F , Bishop RW
Published: December 2008

A new Industrial Hygiene (IH) Sampling Guide has been developed at the U. S. Army Environmental Hygiene Agency (USAEHA). Sampling procedures for over 100 compounds are described. The Guide contains minimum and maximum air volumes, recommended sampling rates and times for time weighted average (TWA), ceiling and short-term exposures, and the proper collection media for air sampling. It also addresses the types of containers and amount of sample required for bulk samples. This IH Sampling Guide is used by all Army industrial hygienists and industrial hygiene technicians involved in workplace monitoring. It enables the field personnel to sample using methods that are compatible with the Agency's state-of-the-art laboratory procedures.
Recent Developments in the Sampling and Analysis of Isocyanates in Air
Authors: Dharmarajan V , Lingg RD , Booth KS , Hackathorn DR
Published: December 2008

In the past decade (1975 to 1985) there has been a considerable amount of research activity in the field of sampling and analysis of isocyanates in air. The general trend has been to move away from impinger sampling to solid sorbent or coated filter techniques or both, and the method of analysis has shifted from spectrophotometric to chromatographic techniques.

Dynamic atmospheres of various isocyanates were generated in the laboratory and several sampling and analysis methods for isocyanates were evaluated. The sampling media tested include impingers containing p-nitrobenzyl propylamine (nitroreagent) and Marcali solutions, nitroreagent coated glasswool and glassifiber filters coated with nitroreagent, 1-(2-pyridyl)piperazine (PP), and sulfuric acid. The particle size distribution of the 4,41 diphenylmethane diisocyanate (MDI) atmosphere was also determined.

The studies show that isocyanates having significant vapor pressure such as toluene diisocyanate (TDI), hexamethylene diisocyanate (HDI), and phenyl isocyanate (PI), are usually present as a vapor in the ambient atmosphere and generally the impinger, the solid sorbent, and the coated filter methods sample them efficiently. However, it has been found in the laboratory generated airborne atmospheres of nonvolatile isocyanates such as MDI and 4,4′ dicyclohexylmethane diisocyanate (Des W or hydrogenated MDI) that the coated filter methods have better collection efficiency than the impingers. Nevertheless, a study from a Swedish team has found quite the opposite results in the field for MDI. In an MDI based polyurethane insulation spraying operation, the impingers collected more than the coated filters in simultaneous sampling.

This paper summarizes our evaluations of the various methods for the sampling and analysis of isocyanates and propose a hypothesis to explain the apparently contradictory finding of the collection efficiency of the filter and impinger method for MDI in the laboratory-generated atmosphere and in the field.
The Role of Research in the Standards Development Process
Authors: Cullen WC
Published: December 2008

Roofing research activities in the United States are currently at a minimal level, although the roofing industry is a $7.5 billion industry employing over four million people. Since the products of research provide the technical basis for the standards develelopment process, it is not surprising that the roofing community has failed in the timely production of standards for the newer materials and in the modernization and updating of standards for the conventional materials. The available standards are mostly prescriptive in nature and are deficient in defining the performance to be expected of a material, composite, and system under actual service conditions. This paper reports on the experience of several European countries in conducting research and using the results as a means to produce assessment directives for evaluating and certifying the performance quality of roofing materials and systems. The directives are described as to their contents and use. In light of the European experiences, some research and standards needs of the United States are identified and a direction is presented for consideration.
Tests of Adhesive-Bonded Seams of Single-Ply Rubber Membranes
Authors: Rossiter WJ
Published: December 2008

Commercially-available ethylene propylene diene terpolymer (EPDM), neoprene, and chlorosulphonated polyethylene (CSME) roofing membrane specimens with adhesive-bonded seams were tested in tension in a lap-shear configuration. Some T-peel tests of an EPDM material were also conducted. The lap-shear tests were conducted at temperatures ranging from −20 to 75°C (−4 to 167°F), and at rates of loading from 0.05 to 50 cm/min (0.02 to 20 in./min). In most cases, the EPDM and neoprene specimens failed by seam delamination; otherwise, they failed by membrane rupture with partial delamination of the seam. The CSME specimens always failed by membrane rupture without seam delamination. In general, the results indicated that, as the temperature of the test increased, the ultimate load and elongation at failure decreased. Also, at a given temperature, the ultimate load and elongation generally decreased, for most specimens, as the rate of loading decreased. For stress relaxation experiments, specimens strained to 15% remained intact for over 15 months, whereas other specimens strained to 30% failed in about five weeks. The results of the tests are discussed with regard to the development of tests for seams in single-ply membranes.
Silicon Epitaxial Growth on N+ Substrate for CMOS Products
Authors: Swaroop RB
Published: December 2008

An N-type epitaxial layers were grown over low resisitivity N-type substrate with and without pre-epi internal gettering (IG) cycle. Epitaxy was grown using either Silicon tetrachloride (SIL) or Silicon dichloride (DCS) at 1200° and 1100°C respectively. The epitaxial structures were characterized for as-grown microdefects and electrical characteristics (minority carrier lifetimes, breakdown voltage and C-t holdtime). The results indicate that epitaxial layers grown at a low growth rate and high temperature produced a minimum density of microdefects. These defects may further be reduced during subsequent thermal cycles especially with pre-epi IG-cycle. Consequently, electrical characteristics of epi layer were also improved.
The Electrical Properties of MOS Transistors Fabricated with Direct Ion Beam Nitridation
Authors: Lee H-S
Published: December 2008

Direct ion beam nitridation was used to form a thin masking layer in the field oxide growth step. The resulting field oxide encroachment per device edge was reduced from 1.0 µm found in LOCOS devices to 0.33 µm. However, the transistors fabricated with the ion beam nitridation step displayed poor device characteristics. We found that with the growth of 50 nm of sacrificial oxide at 950°C and then subsequent removal of the oxide before the gate oxide growth, the adverse side effects, such as; low electron field effect mobility, high junction leakage current and low gate oxide breakdown strength can be drastically improved.
Quality Control and Optimization During Plasma Deposition of a-Si:H
Authors: Kunst M , Werner A , Beck G , Kuppers U , Tributsch H
Published: December 2008

It is shown that contactless time-resolved microwave conductivity (TRMC) measurements permit an in-process quality control during the plasma deposition of amorphous hydrogenated silicon (a-Si:H) films. The relation between the transient photoconductivity of the amorphous semiconductor and its quality is discussed. The influence of various parameters, such as the substrate temperature and chemical composition on the shape of the signals is explained in terms of charge carrier kinetics. An automated production process to yield quality films is presented to demonstrate the use of these measurements.
Characterization of Silicon Surface Defects by the Laser Scanning Technique
Authors: Liaw HM , Rose JW , Nguyen HT
Published: December 2008

The increase of circuit complexity in an IC chip has greatly increased the cost of processed wafers. The cost can be reduced if the defective wafers which cause the poor process yields can be screened prior to the wafer processing. Recent advanced in laser optics and data processing have made automatic laser scanners available. The laser scanners can be potentially used for 100% of the screening of incoming wafers and as a process control tool for certain steps of wafer processing. This paper reports (1) the correlation of defects detected by the laser scanner with the physical nature of defects, (2) utilization of the laser scanner for the characterization of process-induced defects, and (3) utilization of the laser scanner for monitoring substrate cleaning and epitaxial growth processes.
Damage Aspects of Ingot-to-Wafer Processing
Authors: Dyer LD
Published: December 2008

Intensive efforts have been put into the growth of silicon crystals to suit today's solar cell and integrated circuit requirements. Each step of processing the crystal must also receive concentrated attention to preserve the grown-in perfection and to provide a suitable device-ready wafer at reasonable cost.

A comparison is made between solar cell and I.C. requirements on the mechanical processing of silicon from ingot to wafer. Specific defects are described that can ruin wafers or can possibly lead to device degradation. These include grinding cracks, saw exit chips, crow's-foot fractures, edge cracks, and handling scratches.
Hydrogen in silicon and generation of haze on silicon surface in aging
Authors: Shiraiwa T , Inenaga S
Published: December 2008

Hydrogen in silicon wafers was analysed by the gas analysis method of metals. Silicon wafers made by routine process contain a few ppm hydrogen. Diffusive hydrogen was observed in p-type silicon. It was proved that these hydrogen is absorbed into the wafer from water containing acid. The present results agree with current reports that hydrogen diffuses into p-type silicon and acts as a compensator of an acceptor.

Haze which is observed on mirror polished surface of p-type silicon was investigated by SEM and ESCA, and they revealed that haze is due to scattering of light by nodules of silicon oxide which grow on the wafer sarface in density of 104/cm2. The present anthors suggest that oxidation is due to water formed by hydrogen which diffused out to the surface of wafer as well as moisture in the atmosphere.
Identifying Gettered Impurities in Silicon by LIMA Analysis
Authors: Arst MC
Published: December 2008

LIMA — Laser Induced Mass Analysis — was used to identify impurities captured in defect structures formed by three different backsurface damage systems. Analysis data indicate that a poly layer and wet sandblast damage provide greater getter efficiency than abrasive SVG backsurface damage.

In this study oxidized CZ and FZ silicon samples were evaluated. Impurities such as Na, K, Al, Cr, Cu as well as H, C, O and Cl could be identified in the backsurface structures and the oxide layer, but not in the silicon bulk beyond the getter related defects. The so identified gettered impurities were directly correlated to the defect density observed on the front surface, while also considering the impact of the interstitial oxygen concentration in the CZ wafer samples.

The LIMA technique uses a Nd:Yag laser to vaporize and ionize portions of the sample. The generated ions are then injected into a “time of flight” mass spectrometer, which displays a complete mass spectrum within microseconds. This capability to vaporize and characterize microvolumes of sample materials in relatively short times make this an attractive technique for bulk analysis.
High Reliability Infrared Measurements of Oxygen and Carbon in Silicon
Authors: Inoue N , Arai T , Nozaki T , Endo K , Mizuma K
Published: December 2008

High reliability infrared measurements of oxygen and carbon in silicon single crystals are presented. One is the preparation and distribution of standard sample sets with known oxygen contents. Oxygen content range is 5 to 11×1017 atoms/cm3 and the accuracy is estimated to be within 4×1016 atoms/cm3. The other is the establishment of a standard infrared measurement procedure for carbon performed by round robin infrared measurement and charged particle activation analysis. From the procedure the conversion coefficient is determined to be (8.5±0.9)×1016 atoms·cm−3/cm−1.
Nature of Process-Induced Si-SiO2 Defects and Their Interaction with Illumination
Authors: Kar S , Tewari M
Published: December 2008

Transparent gate structures were fabricated by electron beam evaporation of Sn-doped In2O3 on oxidized p-Si substrates. The samples were oxidized at 1100°C in dry oxygen. No post-oxidation or post-electrode-deposition annealig was carried out. Admittance-voltage-frequency measurements were made under optical illumination. Interface state density distributions and hole and electron capture cross-sections were obtained using the recently developed optical metal-oxide-semiconductor (MOS) admittance technique. The experimental interface state density profile contained two peaked distributions, one near the valence band-edge Ev, and the other near the conduction band-edge Ec, overlying a concave background. The peak near Ec was sharper and the peak density was higher than in the case of the peak near Ev. The capture cross-section vs band-gap energy profile also displayed a peaked distribution for interface states under each of the peaks. With increasing illumination, the state density at the peak increased, the peak energy location moved closer to the respective band-edge, and the capture cross-section decreased. The experimental results show the presence of defects at unpassivated Si-SiO2 interfaces, which exchange electrons/holes with silicon bands under illumination.
A Strategy for Reducing Variability in a Production Semiconductor Fabrication Area Using the Generation of System Moments Method
Authors: Maass EC
Published: December 2008

Tightening the distributions of key device parameters is increasingly important in the enhancement and prediction of yields, and in improving the quality of the products of a semiconductor fabrication area. Extensive experimentation is not always feasible in a production area. Statistical tools and knowledge of the effects of processing factors on the device characteristics are used to help identify the most significant causes of variability with the fewest experiments. The Generation of System Moments method, combined with reliable mathematical models or simulation programs which relate device parameters to processing factors partitions the device parameter variance to the causes according to partial derivatives obtained from the model. In identifying the most significant factor, this method is an effective tool in evaluating methods and tradeoffs in efforts to improve process control. The most significant factors involved in threshold and breakdown voltage variability were identified using this approach.
Computerized Yield Modeling
Authors: Beck CH
Published: December 2008

A computer program has been developed which extends the existing technique for calculating global circuit yield factor of lateral geometric design rules by process simulation. The current paper describes the inclusion of resistor limits as part of the general yield model. The program depends upon a reliable data base including: 1) geometric tolerances, 2) skews or offsets of critical dimensions during processing, 3) tolerable minimum separation of circuit element edges, 4) film tolerances of resistivity and thickness, and 5) resistor design limits.

The program incorporates conventional means of original design rule creation.
Particle and Material Control Automation System for VLSI Manufacturing
Authors: Brain MD
Published: December 2008

This paper describes a practical automation system for integrated circuit fabrication combining the SMIF (Standard Mechanical InterFace) concept with a new approach to material control. SMIF implementation is shown to provide a cost effective clean environment and a unique opportunity for information management automation. Each SMIF port acts as a material “gateway”, controlling lot processing via data attached directly to the SMIF pod. Misprocessing is eliminated, particulate contamination is reduced, and productivity is improved.
Semiconductor Yield Enhancement Through Particle Control
Authors: Casper ND , Soren BW
Published: December 2008

Contamination control has always been an important part of semiconductor processing. Until recently, it has been fairly easy to control particles at the level necessary to obtain satisfactory LSI device yields, by requiring personnel to wear protective clothing and by filtering the room air. However, device geometries have shrunk to the point where a more sophisticated means of identifying and controlling particles is needed in order to fabricate working VLSI devices. We have developed a method for identifying, measuring, monitoring, and controlling particles in a cleanroom. This method involves the characterization of wafer fabrication defects with respect to process equipment, measurement of particles with an automatic wafer inspection system, defect monitoring over time through control charts, and the establishment of regular cleaning procedures.
Particulate Control in VLSI Gases
Authors: Davidson JM , Ruane TP
Published: December 2008

Semiconductor device miniaturization has required continually decreasing levels of particulate contamination in process gases. This paper briefly reviews existing technologies for analyzing and for minimizing particles in VLSI gas streams. Recent advances and research topics in both areas are also addressed. Examples from laboratory and field evaluations of VLSI and non-VLSI systems are discussed.
Spreading Resistance : A Comparison of Sampling Volume Correction Factors in High Resolution Quantitative Spreading Resistance
Authors: Pawlik M
Published: December 2008

The development of fine geometry devices requires a greater depth of understanding of dopant incorporation mechanisms and the subsequent location of carriers. Spreading resistance is an accepted method for determining carrier concentration profiles. The deconvolution of these profiles from the raw spreading resistance data is a crucial step which uses so called sampling volume correction factors. These are complex and difficult to evaluate but a number of algorithms are available which attempt the necessary integrations and iterations. Five of these algorithms are reviewed and their accuracy and performance are evaluated on real (as opposed to model) data. The need for new methods of data smoothing is highlighted and it is concluded that the so called Berkowitz-Lux algorithm is currently the most successful available.
A Comparative Study of Carrier Concentration Profiling Techniques in Silicon: Spreading Resistance and Electrochemical CV
Authors: Pawlik M , Groves RD , Kubiak RA , Leong WY , Parker EHC
Published: December 2008

The need to be able to measure carrier concentration profiles in silicon has led to the improvements in well known techniques e.g. spreading resistance (SR) and the development of new techniques e.g. electrochemical CV profiling (ECV). Both of these techniques have demonstrated features such as depth resolution, sensitivity and dynamic range but each show some limitations and problems in practical implementation. This paper demonstrates the use of both techniques on a number of samples, in particular silicon grown by MBE showing rapid dopant transitions. The profiles obtained by both techniques are compared and reasons for differences are discussed.

It is concluded that both techniques offer certain advantages in carrier concentration profiling e.g. dynamic range with SR and speed of data acquisition with ECV but both have limitations e.g. the need for correction factors with SR and limited dynamic range in ECV. As a consequence, both techniques should be viewed as being complementary and not competing.
Qualification of GaAs and AlGaAs by Optical and Surface Analysis Techniques
Authors: Black JF , Berak JM , Peterson GG
Published: December 2008

Optical techniques, including photoluminescence and infrared spectroscopies, have been investigated as a means of evaluating GaAs and AlGaAs wafers. Methods of surface analysis such as Auger Electron Spectroscopy and X-Ray Photoelectron Spectroscopy were used to support the optical measurements, as well as provide additional information, in the following areas: (1) evaluation of semi-insulating GaAs (a) by room temperature photoluminescence that showed strong intensity variations on a microscopic scale, suggestive of corresponding variations in semi-insulating properties, and (b) by low temperature photoluminescence that revealed substantial differences in carbon content in wafers with essentially the same resistivity; (2) self-quenching of the band-gap photoluminescence in GaAs at room temperature that appears to be connected with the formation and thickening of native oxide layers; (3) monitoring the course of post-implant annealing of Be-implanted GaAs and AlGaAs by measurements of photoluminescence at room temperature; (4) qualification of photoluminescence as an accurate means for determining composition in AlGaAs layers with aluminum content up to 0.58 mole fraction.
Industry Considerations in Determining Equipment Reliability
Authors: Greiner JC
Published: December 2008

Automation and Mechanization are essential to the future of our industry. The key to success is understanding not only the raw capability of each component of a system but also the capability of each component with human factors integrated. The SEMI Uptime Document (1) isolates and defines components of real factory time and formulates them in two distinct ways: with and without human interfacing. Part one, Equipment Dependent Uptime, has passed balloting and is nearing implementation as an official standard. The second, which will utilize the same components arranged in a manner to account for human interfacing, is being readied for initial balloting.
Application of CCRL Data in the Development of Cement Standards
Authors: Pielert JH , Spring CB
Published: December 2008

The Cement and Concrete Reference Laboratory (CCRL) through its Laboratory inspection and proficiency sample programs collects data which are useful in the development of cement and concrete standards. This paper outlines the scope of CCRL activities, discusses specific examples of technical studies which support standard development, and outlines areas of potential CCRL support to standards committees. CCRL inspections are conducted in laboratories equipped to perform tests on cement, concrete, concrete aggregate, and steel reinforcing bars. The program for the distribution of proficiency samples includes portland cement, portland cement concrete, blended cement, and masonry cement. Data from these programs have over the years been made available to the appropriate ASTM committees. CCRL also studies technical problems of interest to ASTM Committee C-1 on Cement and Committee C-9 on Concrete and Concrete Aggregates. Several activities are presented to illustrate the application of CCRL data.
Quality of Cements in India—Results of Three Decadal Surveys
Authors: Visvesvaraya HC , Mullick AK
Published: December 2008

Increases in cement production in India over the years have been achieved with due considerations to the quality requirements. Systematic data on the quality characteristics of the cement produced in the last three decades indicate the compressive strength of cements to exceed the minimum requirements with sufficient margins. The overall coefficient of variation on the entire production from different plants has remained steady at a level of about 18%. The in-plant coefficient of variation ranges from 4 to 19%.