bluuebunny/crossref_metadata_2025 huggingface dataset:
Tunneling Current Through MIS Structures With Ultra-Thin Insulators
Authors: Fujioka H. , Wann H.-J. , Park D.-G. , King Y.-C. , Chyan Y.-F. , Oshima M. , Hu C.
Published: April 2011

Leakage currents through MIS (Metal Insulator Semiconductor) structures with several ultra-thin (14–30Å) insulators (silicon dioxide, silicon oxynitride, and silicon nitride) have been investigated. The leakage currents through both dioxide and oxynitride films sandwiched between n-type poly-Si gates and n-type substrates can be well fitted by the equation for the electron direct tunneling mechanism using the same effective mass and barrier height. This result indicates that incorporation of a minute amount of nitrogen atoms does not seriously affect the basic electrical properties of the oxide films. Leakage currents through ultra-thin nitride can te also fitted with the equation for the direct tunneling mechanism without assuming any extra conduction mechanisms such as hopping through defects.
Electromigration and Diffusion in Pure Cu And Cu(Sn) Alloys
Authors: Hu C.-K. , Lee K. L. , Gupta D. , Blauner P. , Watson T. J.
Published: April 2011

Atom movements of Cu in pure Cu and Cu(0.5 to 2 wt.% Sn) alloys have been investigated using drift velocity and radioactive tracer techniques. The void growth rate in pure Cu at the cathode end, as a result of electromigration driving force, linearly increases with the applied current density. A marked decrease in the Cu grain boundary diffusivity and electromigration drift velocity is attributed to Sn trapping of Cu atoms and/or binding defects at grain boundaries. The effect is more pronounced at lower temperatures. The activation energies for electromigration and diffusion of Cu in pure Cu grain boundaries were found to be in the range of 0.7 – 0.9 eV. Addition of about 0.5 to 2 wt.% Sn increased these energies to 1.1 – 1.3 eV, respectively which resulted in enhancement of electromigration resistance by several orders of magnitude over that in pure Cu at the field operation temperature.
Non-Contact Mapping of Fe Contamination in Oxidized Si Wafers with Sensitivity in Part-Per-Trillion Range
Authors: Lagowski Jacek , Edelman Piotr
Published: April 2011

Traces of iron contamination as minute as one part per trillion atom fraction can be detrimental to the gate oxide integrity of the very thin oxides, 10 nm or less, used in the most advanced ICs. Fe contamination monitoring discussed in this paper is done with the surface photovoltage (SPV) technique which measures the minority carrier diffusion length, L, before and after the recombination efficiency of iron is enhanced by optical splitting of the iron-boron
pairs. Wafer-scale mapping of iron gives fingerprints of contaminating tools and processes. In this paper, we also present an extension of SPV to oxidized wafers. In the past, such measurements were rendered impossible due to optical interference in the SiO2.

The apparatus incorporates a whole wafer, optical Fe activation station and it provides whole wafer maps of Fe in a total time of 6 to 20 minutes per wafer, depending on probing density.
The Mechanics of A Free-Standing Straitned Film/Compliant Substrate System
Authors: Freund L. B.
Published: April 2011

The deformation of film/substrate systems due to a through-the-thickness distribution of mismatch strain is discussed for cases when the layers are thin, compliant and freestanding. The connection between substrate curvature and mismatch strain is reviewed within the framework of small strains and small deflections. These results are applied to determine the second-order correction to the Stoney formula and to note the connection between mismatch strain distribution and curvature history. Then, for small strains but large deflections, it is observed that a symmetric system with equi-biaxial mismatch strain can undergo a bifurcation in deformation mode. It is also shown that the bifurcation response is sensitive to system imperfections. Finally, the critical condition for introduction of an interface misfit dislocation in an epitaxial system is established, thereby extending the Matthews-Blakeslee criterion to the case of free-standing compliant systems.
Relationship Between The Void And Hillock Formation And The Grain Growth In Thin Aluminum Films
Authors: Kononenko O. V. , Matveev V. N.
Published: April 2011

Void and hillock formation during annealing was studied depending on the deposition conditions. Aluminum films were deposited onto oxidized silicon substrates by the self-ion assisted technique. The bias 0 or 6 kV was applied to the substrate during deposition. The films were then annealed in vacuum for 1 hour in the temperature range from 1500 to 550°C. The structure of the films was investigated by transmission electron microscopy.

It was found that recrystallization and void and hillock formation in the films depend on the bias during deposition. Normal grain growth occurred in the films deposited without bias. Abnormal grain growth was observed in the 6 kV-films. It was also found that the mechanism of stress relaxation during thermal cycling depends on the self-ion bombardment. In the films prepared without bias, stress relaxation proceeds by diffusion creep. In the films deposited at the 6 kV bias, stress relaxation proceeds by plastic deformation.
Processing-Induced Stresses And Curvature In Patterned Lines On Silicon Wafers
Authors: Shen Y-L. , Suresh S. , Blech I. A.
Published: April 2011

The evolution of stresses due to the patterning and thermal loading of thin lines on Si wafers, and the consequent changes in the overall curvature of the wafer are studied theoretically and experimentally. The analysis involves finite element simulations within the context of generalized plane strain models. The analysis is capable of predicting the wafer curvature in directions parallel and perpendicular to the lines. These predictions compare reasonably well with experimental measurements of curvature made on model systems. The thickness, width and spacing of the patterned lines have been varied systematically, and the associated changes in the evolution of stresses and curvature have been determined. The non-uniform stress field within the fine lines is also analyzed.
Submicron Resolution X-Ray Strain Measurements On Patterned Films: Some Hows And Whys
Authors: Marcus M. A. , Macdowell A. A. , Isaacs E. D. , Evans-Lutterodt K. , Ice G. E.
Published: April 2011

As interconnect technology moves deeper into the submicron realm, the physics governing the mechanical behavior, hence the reliability of metal lines changes. Events at the level of individual grains become more important. One would like to be able to measure the strain and orientation of single grains, and the distribution of strain across a grain. Such data may help us understand such effects as sunken grains, the erratic occurrence of stress voiding and Blechlength effects in electromigration. To get this information, techniques involving X-ray diffraction with submicron beams are being developed. These experiments involve detecting Laue spots from selected areas and energy-analyzing them to find the strain tensor. Motivations for such measurements, the specifications for a useful instrument, some designs now being developed and the intrinsic limitations of these approaches will be discussed. Design issues in the choice of focussing optics and energy measurement will be highlighted with calculations of how the Laue spots would look for different conditions of crystal perfection.
General Kinetic Rules for Rapid Thermal Processing
Authors: Ditchfield R. , Seebauer E. G.
Published: April 2011

Up to now, kinetic effects in rapid thermal processing (RTP) have been assessed qualitatively and rather vaguely through the concept of thermal budget. We discuss the shortcomings associated with thermal budget and present an alternate conceptual framework that explicitly treats selectivity between desired and undesired physical phenomena. This framework is quite simple and is intended for rapidly assessing the qualitative effects of various heating programs. From a purely kinetic perspective, selecting the best program involves only comparing the activation energies for the desired and undesired rate phenomena. We cite examples where application of the thermal budget approach gives incorrect guidance for minimizing the undesired process. Such deficiencies are rectified by the framework presented here.
Modeling of Device Characteristics as Function of Ti Salicide Rapid Thermal Processing Parameters for Deep-Sub-Micron CMOS Technologies
Authors: Kittl J. A. , Prinslow D. A. , Misium G. , Pas M. F.
Published: April 2011

Rapid thermal processing is widely applied in self-aligned Ti silicide processes for deep-submicron devices. We investigated and modeled the effects of rapid thermal processing variables (silicide formation temperature and time, and anneal temperature and time) and Ti thickness on deep-sub-micron device characteristics. The effect of Ti thickness, formation temperature and time on diode leakage and bridging due to silicide lateral growth, and its correlation to silicide thickness was analyzed; as well as the effects of these and the anneal variables on n+ gate sheet resistance, silicide to source/drain contact resistance and transistor source-drain series resistance. An expression for n+ gate sheet resistance is given, as function of anneal temperature and time, silicide thickness, linewidth and TiSi2 C49 grain size after formation, based on a nucleation density model in agreement with measurements of TiSi2 C49 to C54 transformation kinetics. The tradeoffs and process window limits are discussed, as well as trends observed when scaling down lateral and vertical dimensions. We show that for advanced technologies, the scaling of silicide thickness and linewidth narrows the process window between full C49 to C54 transformation and agglomeration temperatures. Due to the high activation energy of the C49 to C54 transformation, a process window for low sheet resistance exists only for high temperature-short time processes.
Correlation Between the Standard Deviation of Sheet Resistance and the Temperature of Rapid Thermal Annealing
Authors: Lin X. W. , Pramanik D.
Published: April 2011

Rapid thermal annealing (RTA) induced reactions between Ti thin films and Si wafers were characterized by sheet resistance measurements. It was found that the standard deviation a of the measurements is RTA-temperature dependent, and strongly correlates with the mean sheet resistance R. A specific temperature was identified, corresponding to a sharp σ peak in the temperature regime associated with the C49-C54 TiSi2 phase transition. This temperature is characteristic of materials parameters such as Ti thickness and substrate doping species, and can be used to accurately monitor or compare the calibration of RTA systems.
In Situ Rapid Thermal Hydrogenation Pretreatment of Ti for Salicide RTA
Authors: Ando K. , Ishigami T. , Matsubara Y. , Horiuchi T. , Nishimoto S.
Published: April 2011

An in situ rapid thermal hydrogenation (RTH) pretreatment of titanium prior to rapid thermal annealing (RTA), or RTH/RTA, is proposed as a silicide formation annealing in a CMOS self-aligned silicide (salicide) process. The in situ RTH is found to enhance silicidation, to reduce nitridation, and even to lower the resultant sheet resistance of titanium silicide.

During in situ RTH (e.g., at 550°C), amorphous Ti silicide (e.g., 15-nm thick) grows selectively on Si. Furthermore, Ti nitridation during subsequent RTA (690°C, N2, 10 Torr, 30 s) is reduced depending on RTH (H2, 10 Torr, 30 s) temperature. Accordingly, for 550°C RTH and an initial Ti thickness of 15 nm, the sheet resistance obtained at the 0.27-μm-wide n+ poly-Si gate after a phase transition annealing (800°C, Ar, 10 s) was lower (11.7 Ω /□, st. dev. = 6%) than that of conventional Ti silicide (15.8 Ω/□, st. dev. = 10%). The silicidation enhancement and nitridation reduction are related to crystal structure metamorphosis or to hydrogen interstitial incorporation in the Ti layer during RTH as observed by x-ray diffraction analysis. It is concluded that in situ RTH pretreatment before RTA is very promising as a sub-quarter-micron CMOS salicide process.
UV Photoannealing and RTP of Thin Sol-Gel Films
Authors: Leest R. E.Van de , Roozeboom F.
Published: April 2011

Various annealing methods for sol-gel films have been investigated. Thermal, photothermal, RTP and excimer laser annealing have been used to convert sol-gel precursor films into oxidic films. RTP annealing of sol-gel films yields better results than classical thermal annealing or excimer laser irradiation. Photochemical effects during RTP annealing contribute to obtain high-quality oxide films. The various annealing methods are illustrated by the annealing of alkoxide precursor films of tantalum, iron, nickel and yttrium.
Nitrided Gate Dielectrics and Charge-to-Breakdown Test
Authors: Dimitrijev S. , Tanner P. , Harrison H. B. , Sweatman D.
Published: April 2011

In this paper, the applicability of the charge-to-breakdown test for characterisation and comparison of differently grown ultra-thin gate dielectric films is considered. It is shown that the charge-to-breakdown parameter cannot be reliably used, because it is related to the electrons tunneling through the film, and not to the mechanism of positive charge accumulation which leads to time-dependent breakdown. It is found that the constant-voltage stress provides a consistent set of stress field vs time-to-breakdown data. Nitrided gate dielectrics show improved breakdown characteristics, compared to standard silicon-dioxide films.
Characterisation of Dielectric Damage in MOS Capacitors by a New Current Transient Measurement Technique
Authors: Tanner P. G. , Dimitrijev Sima , Yeow Y-T. , Harrison H. B.
Published: April 2011

With the requirement for reduced dielectric thickness and improved durability in silicon MOS devices, new growth techniques and material composition are constantly being developed. An important part of this development is the electrical characterisation of the dielectric material and in particular the properties of the dielectric-semiconductor interface.

This paper presents a study of damage caused to the dielectrics of MOS capacitors which have been subjected to either constant current stressing or RF plasma etching. The density and energy position of fast interface states and fixed oxide charges were measured using standard capacitance-voltage techniques. These results are then compared with a new current transient technique, which has been developed to measure slow interface states having a range of response times. This new technique steps the surface Fermi level through the silicon bandgap and the resulting current transients provide information on trap response times at each energy position. The response time can then be related to the tunneling distance from the trap to the bulk silicon. This technique has provided important information about the energies and response times of traps generated in damaged dielectrics, and should prove to be a useful tool for damage evaluation in the future.
Temperature Monitoring by Ripple Pyrometry in Rapid Thermal Processing
Authors: Nguyenphu Binh , Oh Minseok , Fiory Anthony T.
Published: April 2011

Current trends of silicon integrated circuit manufacturing demand better temperature control in various thermal processing steps. Rapid thermal processing (RTP) has become a key technique because its single wafer process can accommodate the reduced thermal budget requirements arising from shrinking the dimensions of devices and the trend to larger wafers. However, temperature control by conventional infrared pyrometry, which is highly dependent on wafer back side conditions, is insufficiently accurate for upcoming technologies. Lucent Technologies Inc., formerly known as AT&T Microelectronics and AT&T Bell Laboratories, has developed a powerful real-time pyrometry technique using the A/C ripple signal from heating lamps for in-situ temperature measurement. Temperature and electrical data from device wafers have been passively collected by ripple pyrometers in three RTP systems and analyzed. In this paper we report the statistical analysis of ripple temperature and electrical data from device wafers for a typical implant anneal process temperature range of 900 to 1000 °C.
Estimation of Emissivity of a Wafer in an RTP Chamber by a Dynamic Observer
Authors: Belikov Sergey , Hur David , Friedl Bernard , Ravindra N. M.
Published: April 2011

A method of estimation of wavelength-dependent emissivity of silicon wafers using thermocouple measurements is presented here. A dynamic observer and a persistent excitation of the lamps are required for convergence of the observer's estimates to the actual values of parameters for emissivity approximation. A TI designed RTP equipment and adaptive close-loop temperature control have been used to generate the required persistent excitation. Theory of emissivity estimation by this method has been developed and illustrated by experiment with this 3- zone RTP system.
Numerical Modeling of Radiative Properties of Patterned Wafers with Sub-Micron Features
Authors: Hoppert Jeffrey B. , Miaoulis Ioannis N. , Wong Peter Y.
Published: April 2011

Decreasing feature sizes in the microelectronics industry have led to numerous processing problems with thin film semiconductors. Non-uniform temperature distributions, due to microscale radiation effects on the radiative properties of the thin film structures, are responsible for wafer defects. These microscale radiation effects become significant as pattern spacing and film thicknesses reach the same order of magnitude as the wavelengths of the heat-source radiation. A numerical model has been developed in which normal emissivities for patterned wafers are calculated, using an effective index of refraction technique. In this study various patterns at temperatures critical to the thermal processing are examined.
Application of Ridged Waveguide in Microwave Sintering
Authors: Jian Zhou , Jiping Cheng , Xianjun Liu , Yuling Tang , Lei Chen
Published: April 2011

In this paper, a ridge rectangular waveguide is designed, and its cutoff frequency, impedance and electric field intensity are given by formulas or curves. A few ceramic samples are sintered in it by microwave energy. It is concluded that the device can be as a satisfactory microwave sintering cavity.
Fdtd Simulations And Analysis Of Thin Sample Dielectric Properties Measurements Using Coaxial Probes
Authors: Bringhurst S. , Iskander M. F. , White M. J
Published: April 2011

A metallized ceramic probe has been designed for high temperature broadband dielectric properties measurements. The probe was fabricated out of an alumina tube and rod as the outer and inner conductors respectively. The alumina was metallized with a 3 mil layer of moly-manganese and then covered with a 0.5 mil protective layer of nickel plating. The probe has been used to make complex dielectric properties measurements over the complete frequency band from 500 MHz to 3 GHz, and for temperatures as high as 1000 °C.
Estimation Of Complex Permittivity Of Printed Circuit Board Material Using Waveguide Measurements
Authors: Reddy C. J. , Deshpande M. D. , Hanidu G. A.
Published: April 2011

A simple waveguide measurement technique is presented to determine the complex permittivity of printed circuit board material. The printed circuit board with metal coating removed from both sides and cut into size which is the same as the cross section of the waveguide is loaded in a short X-band rectangular waveguide. Using a network analyzer, the reflection coefficient of the shorted waveguide(loaded with the sample) is measured. Using the Finite Element Method(FEM) the exact reflection coefficient of the shorted wavguide(loaded with the sample) is determined as a function of dielectric constant. Matching the measured value of the reflection coefficient with the reflection value calculated using FEM and utilizing Newton-Raphson Method, an estimate of the dielectric constant of a printed circuit board material is obtained. A comparison of estimated values of permittivity constant obtained using the present approach with the available data.
Comparison Of Finite-Difference And Analytic Microwave Calculation Methods
Authors: Friedlander F. I. , Jackson H. W. , Barmatz M. , Wagner P.
Published: April 2011

Normal modes and power absorption distributions in microwave cavities containing lossy dielectric samples were calculated for problems of interest in materials processing. The calculations were performed both using a commercially available finite-difference electromagnetic solver and by numerical evaluation of exact analytic expressions. Results obtained by the two methods applied to identical physical situations were compared. Our studies validate the accuracy of the finite-difference electromagnetic solver. Relative advantages of the analytic and finitedifference methods are discussed.
Numerical Simulation of Resonant Cavity Microwave Systems for Materials Processing
Authors: Grotjohn Timothy A. , Asmussen Jes
Published: April 2011

A single mode microwave resonant cavity used for materials heating is simulated using the FDTD method. The simulation includes both the resonant cavity structure and the input microwave power coupling structure. An overlapping grid method with interpolation between the conformal grid systems developed for each section of the microwave system is used to simulate geometrically complex microwave structures. Comparisons of the FDTD solution for a simplified, lossy-loaded cavity is made with a known analytical solution.
FDTD Simulation of Induction Heating of Conducting Ceramic Ware
Authors: White Mikel J , Iskander Magdy F. , Bringhurst Shane
Published: April 2011

Induction heating for the treatment of metals has been in commercial use since the mid 1960's. Traditional advantages of induction heating over the convection or radiation processes include speed of heating, possible energy savings, and the ability to customize the coil design to optimize the heating process. In this paper we used the Finite-Difference Time-Domain (FDTD) technique to simulate and analyze the induction heating process for highly conducting ceramics. In order to analyze frequency effects, simulations were performed at 300 kHz, 2 MHz, and 25 MHz. It is found that at higher frequencies coils with a pitch of 2″ or greater became capacitive and generate a large, axial, electric-field component. This new axial electric field, in addition to the normally encountered azimuthal field, causes an improvement in the uniformity of the power deposition in the ceramic sample. If the sample occupies a large portion of the coil, uniformity may also be improved by using a variable-pitch coil, or by extending the length of the coil a few turns beyond the length of the sample. In a production-line arrangement, where multiple sample are place inside the coil, it is shown that maximum uniformity is achieved when the samples are placed coaxially.
Thermal Phenomena Under Microwave Field in the Organic Synthesis Processes: Application to the Diels Alder Reaction
Authors: Saillard R. , Poux M. , Audhuy-Peaudecerf M.
Published: April 2011

The influence of the microwave heating on chemical reactions were investigated. The kinetic of the Diels Alder reaction were studied under Microwave irradiation at a frequency of 2.45 GHz in a single mode cavity and were compared to the kinetic obtained by a conventional heating. Experiments were carried out in a liquid solvent in order to have a better control of the medium temperature measurement. In a second part, the presence of a catalytic solid phase was introduced. Some thermal fluctuations which are due to an heterogeneity of the electric field were detected in the medium. They reduce the precision of the results and cause problems of experimental reproducibility. A thermoluminescent material allow a good visualisation of these phenomena.

In addition, the profiles of the electric field intensity were modelled by a 2D finite elements method in our reactor in the presence of a solvent. Despite the small size of the sample and the use of a monomode cavity which both limited the heterogeneities of the medium temperature, we showed a great heterogeneity of the electric field intensity and as a result the heterogeneity of the temperature in our sample.

In order to avoid these phenomena which induce a lack of reproducibility, a stirring device was developed.

The values of the kinetics obtained under the 2 heating modes with the introduction of the stirring device. So, it induces a good control of the medium temperature.

All those investigations prompted us to the conclusion that there is no difference between microwave heating and a classical heating in the studied reaction.
Kinetics and Mechanism of the Microwave Synthesis of Barium Titanate
Authors: Zhang Hanlin , Ouyang Shixi , Liu Hanxing , Li Yongwei
Published: April 2011

The formation kinetics of BaTiO3from the solid-state BaCO3and TiO2powder in a microwave field was investigated. The quantitative XRD analysis and the model considered the volume change between reactant and product were used in this experiment. Results show that the formation rate of BaTiO3in a microwave field is much faster than upon conventional heating. The activation energy of the solid state reaction for BaTiO3was measured as 58 kJ/mol. This indicates the enhancement of diffusion by the microwave heating process.
Study Of Microwave-Driven Currents In Ionic Crystals
Authors: Rybakov K. I. , Semenov V. E. , Freeman S. A. , Booske J. H. , Cooper R. F.
Published: April 2011

The recent theory of averaged ponderomotive action of microwave E-field in solids is expanded to describe quasistationary ionic currents driven by that action. New experimental results on the dynamics of the microwave-induced currents in AgCl and NaCi are presented. Agreement between experiment and theory provides further and stronger evidence for general validity of the theoretical model.
Pulsed 35 Ghz Gyrotron with Overmoded Applicator for Sintering Experiments
Authors: Fliflet A. W. , Fischer R. P. , Kinkead A. K. , Bruce R. W.
Published: April 2011

The microwave sintering of nanocrystalline alumina compacts is currently under investigation at NRL. This paper will discuss an overmoded microwave furnace based on a 35 GHz pulsed gyrotron which is currently being set up to extend ongoing microwave sintering experiments at 2.45 GHz to 35 GHz. The gyrotron operates at 70 kV and currents up to 10 A. It is driven by a hard tube, variable pulse length (1–15 μs) modulator at repetition rates up to 1 kHz. The gyrotron can produce peak powers up to 100 kW at an efficiency of 20%, and average powers up to 200 W. The gyrotron output is transported via pressurized Ka-Band waveguide to an overmoded resonator containing the workpiece. In initial experiments, the resonator will consist of a piece of WR-284 waveguide. The operation of the system in preliminary sintering experiments is described.
Temperature Gradients and Residual Porosity in Microwave Sintered Zinc Oxide
Authors: Martin L. P. , Dadon D. , Rosen M. , Birman A. , Gershon D. , Calame J. P. , Levush B. , Carmel Y.
Published: April 2011

ZnO samples were sintered in an overmoded 2.45 GHz microwave applicator. In-situ differential temperature measurements were made to allow comparison of surface and core temperatures during heating. At intermediate temperatures, near 600°C, the sample core was measured to be more than 250°C hotter than the sample surface. As the core temperature approached 1100°C, however, the difference between the surface and core temperatures diminished. Post-sintering scanning electron microscopy (SEM) showed spatial variations in the residual porosity which were consistent with the measured temperature differential. For samples sintered to intermediate temperatures, where large temperature differences persisted, there were significant gradients in the residual porosity. For samples sintered to higher temperatures, there was little residual porosity and no observable porosity gradient. Local density versus temperature behavior was obtained by correlating porosity levels measured from the micrographs with temperature measurements made during sintering. These data demonstrate a significantly lower activation energy for microwave sintering than for conventional sintering.
High Frequency (27.12 MHz) Activation of the Radical Curing of Unsaturated Polyesters in Styrene Solution
Authors: Alazard P. , Gourdenne A.
Published: April 2011

The crosslinking reaction of a divinylester resin of epoxy-acrylic type in styrene solution is activated by high frequencies at 27.12 MHz. The samples to be cured are positionned betweeen two parallel steel plates used as electrodes and an electrical voltage is applied. A parametrical study is described, where the applied electrical voltage, or power, and the concentration of benzoyl peroxide, which is the radical initiator, are taken into account. The optimization of the electromagnetic curing is performed through the determination of the glassy transition temperature of the final products.
Comparative Study of Si3N4 - Based Ceramics Sintering at Frequencies 30 and 83GHz
Authors: Bykov Y. , Eremeev A. , Holoptsev V.
Published: April 2011

The study of microwave ceramics sintering at different frequencies of radiation has important implication for clarifying a specific effect inherent to microwave-based processes and determining the optimal conditions of sintering which yield a high-quality final product. Comparative study of Si3N4-based ceramics sintering at the frequencies of 30 and 83GHz was undertaken on retention of all the conditions but a frequency and microwave power. It is found that an increase in microwave frequency results in reduction in silicon nitride decomposition during sintering.
Microwave and Millimeter wave Processing of Polymer-Derived Silicon Nitride
Authors: Schwab S. T. , Timmons S. F. , Blanchard C. R. , Grimes M. D. , Graef R. C. , Katz J. D. , Rees D. E. , Hardek T. W.
Published: April 2011

Chemical methods of processing ceramics have the potential to overcome many of the processing-related obstacles that have hindered widespread commercialization. The Southwest Research Institute (SwRI) has focused on the development of polymeric precursors to silicon nitride (Si3N4). One such precursor, perhydropolysilazane (or PHPS), has been shown to be a useful binder for Si3N4 powder processing, a useful matrix precursor for the polymer infiltration/pyrolysis (PIP) processing of fiber-reinforced Si3N4, and a useful ceramic coating precursor for the repair of oxidation protection coatings on carbon-carbon composites. While conventional, thermal pyrolyses of these preceramnics has been sufficient to demonstrate their potential, substantial cost savings could be realized if the polymer-to-ceramic conversion could be instigated with electromagnetic energy. We have investigated the use of millimeter wave heating as a means of converting PHPS into Si3N4, and report here the results of our efforts to produce bulk compacts, coatings, and fiber-reinforced ceramics.
Microwave Plasma Sintering of Alumina
Authors: Johnson D. Lynn , Su Hunghai
Published: April 2011

Microwave induced plasma provides an effective heating source for sintering of ceramics without the thermal instability that occurs in microwave sintering of some materials. In the present study, small cylindrical tubes were sintered in a microwave induced oxygen plasma inside a single mode (TM012) cavity. A dilatometer and an optical fiber thermometer (OFT) black body sensor were employed to follow the changes of shrinkage and temperature during the sintering process. A similar specimen setup was built inside a conventional rapid heating furnace for comparison. The estimated activation energies were 468 ± 20 kJ/mol for plasma sintering and 488 ± 20 kJ/mol for conventional sintering. An athermal effect due to the plasma was observed. Sintering data were analyzed using the combined stage sintering model and the results suggest that the athermal effect may be ascribed to an increase of aluminum interstitial concentration during plasma sintering.
Kinetics of Intrinsic and Dopant-Enhanced Solid Phase Epitaxy in Buried Amorphous Si Layers
Authors: McCallum J. C.
Published: April 2011

The kinetics of intrinsic and dopant-enhanced solid phase epitaxy (SPE) have been measured in buried amorphous Si (a-Si) layers produced by ion implantation. Buried a-Si layers formed by self-ion implantation provide a suitable environment for studies of the intrinsic growth kinetics of amorphous Si, free from the rate-retarding effects of H. For the first time, dopant-enhanced SPE rates have been measured under these H-free conditions. Buried a-Si layers containing uniform As concentration profiles ranging from 1–16.1 × 1019 As.cm−3 were produced by multiple-energy ion implantation and time resolved reflectivity was used to measure SPE rates over the temperature range 480–660°C. In contrast to earlier studies, the dopant-enhanced SPE rate is found to depend linearly on the As concentration over the entire concentration range measured. The SPE rate can be expressed in the form, v/vi(T) = 1 + N/[No exp(-ΔE/kT)], where vi(T) is the intrinsic SPE rate, N is the dopant concentration and No = 1.2 × 1021 cm−3, ΔE = 0.21 eV.
Amorphization Mechanisms in AlxGa1-xAs
Authors: Lagow B. W. , Turkot B. A. , Robertson I. M. , Rehn L. E. , Baldo P. M. , Roh S. D. , Forbes D. V. , Coleman J. J.
Published: April 2011

Bulk ion implantations of AlxGa1-xAs (x = 0.6 or 0.85) were performed at 77 K with 1.5 MeV Kr+, 1 MeV Ar+ or 1.5 MeV++ ions, and the resulting damage state examined by using Rutherford backscattering spectrometry-channeling at 77 K and 293 K and transmission electron microscopy at 300 K. Amorphization of a portion of the AlxGa1-x As layer occurred at 77 K only for the 1.5 MeV Kr+ implantation, although the dose required to cause amorphization was higher for the higher Al content alloy. TRIM calculations[10–11 ] show that with this implantation the density of high energy density cascades varies as a function of depth through the layer and that these are superimposed on a high, uniform density of defects. Comparison of the ion channeling spectra at 77 K and 293 K shows that recovery occurs over a portion of the layer in the Al0.6Ga0.4As but is not detected in the Al0.85Ga0.15As layer. In both alloys, the room temperature microstructure consists of an amorphous and a crystalline region. The amorphous region extends from the deeper AlxGa1-xAs/GaAs interface into the layer, and is separated from the crystalline material by a crystalline region containing planar defects. The difference between the alloys is in the extent of this latter region, which decreases in width with increasing Al content. These results will be used to examine current models for amorphization in the AlxGa1-xAs system.
Germanium Redistribution Phenomena in the Synthesis of SiGe Layers
Authors: Patel C. J. , Butcher J. B.
Published: April 2011

A unique germanium redistribution phenomenon occurs in the synthesis of SiGe by 74Ge+, ion implantation. A number of silicon samples were implanted with 74Ge+ ion using a range of substrate temperatures (R.T. to 600°C) with different germanium fluences (1.5 × 1016 cm-2 to 4 × 1016 cm-2) and implantation energies (100keV - 180KeV). Samples were germanium profiled using Rutherford backscattering spectrometry (RBS) and secondary ion mass spectrometry (SIMS).The experimental results show that the peak range of the germanium implant increases progressively above 150°C and a shift of 40nm in the peak germanium range was measured for a sample implanted at 600°C. The ‘hot’ implants have an extended tail profile contrary to the Debye model for root-mean-square deviations of the lattice atoms from their equilibrium sites which should ideally contribute to dechanneling. The data suggest strongly that dynamic annealing related diffusion (DARD) processes exist, whereby mobile non-equilibrium point defects influence diffusion to take place at the elevated implantation temperature. The SIMS spectra of samples implanted with high Ge fluences at elevated temperature show “uphill” diffusion.
X-Ray Photoelectron Spectroscopy Investigation of the Interaction of NF3 with Silicon
Authors: Little T. W. , Ohuchi F. S.
Published: April 2011

The interaction of nitrogen trifluoride (NF3) with silicon (Si) surfaces has been investigated by x-ray photoelectron spectroscopy (XPS). Si (100) surfaces were subjected to NF3 ion bombardment as a means of approximating plasma processing under controlled conditions. Samples were also exposed to actual NF3 DC plasmas and the results compared to ion beam and plasma processing using nitrogen (N2). The results indicate that nitridation of silicon is possible using NF3 although it seems to be limited by simultaneous etching. Additionally, results suggest bonding between both Si-F and Si-N species and perhaps F-N-Si moieties. NF3 plasma processing has lead to curious results for F 1s spectra which are not fully understood at present.
Effect of Energy and Dose on Transient-Enhanced Diffusion and Defect Microstructure in Low Energy High Dose As+ Implanted Si
Authors: Krishnamoorthy V. , Venables D. , Moeller K. , Jones K. S. , Freer B.
Published: April 2011

(001) CZ silicon wafers were implanted with arsenic (As+) at energies of 10–50keV to doses of 2x 1014 to 5x1015/cm2. All implants were amorphizing in nature. The samples were annealed at 700°C for 16hrs. The resultant defect microstructures were analyzed by XTEM and PTEM and the As profiles were analyzed by SIMS. The As profiles showed significantly enhanced diffusion in all of the annealed specimens. The diffusion enhancement was both energy and dose dependent. The lowest dose implant/annealed samples did not show As clustering which translated to a lack of defects at the projected range. At higher doses, however, projected range defects were clearly observed, presumably due to interstitials generated during As clustering. The extent of enhancement in diffusion and its relation to the defect microstructure is explained by a combination of factors including surface recombination of point defects, As precipitation, As clustering and end of range damage.
In-Situ Irradiation Studies on the Effects of Helium on the Microstructural Evolution of V-3.8Cr-3.9Ti
Authors: Doraiswamy N. , Kestel B. , Alexander D. E.
Published: April 2011

The role of helium on the microstructural evolution of V-3.8Cr-3.9Ti has been investigated by in-situ transmission electron microscopy observations of as-prepared and He implanted (<10 appm) samples subjected to 200keV He irradiation at room temperature. Quantitative analysis of the defects showed an increase in the defect density and size with irradiation in both types of samples. The unimplanted sample showed a defect density consistent with electron irradiation experiments. In comparison, the He preimplanted sample had slightly larger defects and a substantially greater increase in the number density of defects. This result is consistent with a mechanism of He trapping by the formation of He-vacancy-X (X= C, N, O) complexes.
Microstructural Kinetics in Alloys Undergoing Transmutations: Application to Aic Neutron Absorbers
Authors: Desgranges C. , Martin G. , Defoort F.
Published: April 2011

Whenever an alloy changes composition because of metal to metal transmutations, as is the case in Ag-In-Cd alloys undergoing (n, −) actions in the control rods of Pressurised Water Reactors, unique features may develop.

A simple model shows that in a two components alloy more than two phases can coexist under appropriate irradiation conditions i.e. temperature, which scales diffusivities and solubilities, and flux, which scales the transmutations rate; because second phase precipitation occurs at the grain boundaries, the grain size in the underlying matrix is found to be one important parameter of the process.

The above ideas are illustrated on a multicomponent alloy, the thermodynamics and the kinetics of which are treated at the same level of sophistication in a mean field approximation.
Ion-Beam Mixing and Solid-State Reaction in Zr-Fe Multilayers
Authors: Paesano A. , Motta A. T. , Birtcher R. C. , Ryan E. A. , Teixeira S. R. , Bruckmann M. E. , Amaral L.
Published: April 2011

Vapor-deposited Zr-Fe multilayered thin films with various wavelengths and of overall composition either 50% Fe or Fe-rich up to 57 % Fe were either irradiated with 300 keV Kr ions at temperatures from 25K to 623 K to fluences up to 2 × 1016 cm−2, or simply annealed at 773K in-situ in the Intermediate Voltage Electron Microscope at Argonne National Laboratory. Under irradiation, the final reaction product is the amorphous phase in all cases studied, but the dose to amorphization depends on the temperature and on the wavelength. In the purely thermal case (annealing at 773 K), the 50–50 composition produces the amorphous phase but for the Fe-rich multilayers the reaction products depend on the multilayer wavelength. For small wavelength, the amorphous phase is still formed, but at large wavelength the Zr-Fe crystalline intermetallic compounds appear. These results are discussed in terms of existing models of irradiation kinetics and phase selection during solid state reaction.
Microstructure and Modelling of RPV Embrittlement
Authors: English C. A. , Phythian W. J. , McElroy R-J.
Published: April 2011

In this paper we review the advances in understanding ofmicrostructural evolution during irradiation in pressure vessel steels. A particular focus is the benefits that arise from combining microstructural techniques on characterising the microstructure, especially the copper clusters. In addition to experimental techniques the importance of developing microstructurally based models linking the microstructural features to mechanical properties behaviour will be demonstrated. This paper will consider the recent advances in understanding in this area, and highlight the potential benefits that can be gained from a thorough understanding of the materials response to irradiation.
Clustering of Point Defects Under Electron Irradiation in Dilute Iron Alloys and an Iron Manganese Nickel Alloy
Authors: Hardouin-Duparc A. , Barbu A.
Published: April 2011

In low copper steels for nuclear reactor pressure vessel, point defect clustering seems to play an important role in hardening. In order to study the hardening component which results from the clustering of freely migrating point defects, we irradiated, in a high voltage electron microscope, Fe, the alloys Fe0.13%Cu and Fe0.014%P, alloys and the alloy Fel.5%Mn0.8%Ni0.1%Cu0.01%P, the composition of which is close to the matrix of pressure vessel steels. We studied the nucleation of dislocation loops and their growth velocity. We find out that copper and phosphorus have no effect on the vacancy migration energy but that this parameter decreased significantly in the complex alloy. The main point is certainly that loops are nucleated in the complex model alloy up to 500°C while no loop appears above 300°C in Fe and in FeCu. FeP shows an intermediate behavior.
Influence of the Irradiation Temperature on the Formation of Defects in Reactor Pressure Vessel Steels
Authors: Große M. , Hempel A. , Böhmert J. , Brauer G. , Haggag F. M.
Published: April 2011

Two heats of reactor pressure vessel steel type A533-B-1 differing in their Cu content (0.07 and 0.14 wt.-%) were irradiated to a fluence of 1* 1018 neutrons/cm2 at temperatures of 60, 121, and 288 °C, respectively. Their microstructure has been studied by SANS, SAXS, and PAS in the asirradiated and post-irradiation annealed stages and compared to the behaviour of unirradiated material and the results are discussed.
Dose Dependence of Radiation Induced Segregation in Proton Irradiated Austen1tic Alloys
Authors: Busby J. T. , Allen T. R. , Carter R. D. , Kenik E. A. , Was G. S.
Published: April 2011

The dose dependence of radiation-induced segregation (RIS) is investigated for proton irradiated ultra high-purity (UHP) 304L stainless steel and Fe-20Cr-24Ni. Grain boundary compositions were measured in samples irradiated with 3.2 MeV protons at 400°C to doses ranging from 0.1 to 3.0 dpa. RIS measurements were made using scanning transmission electron microscopy with energy dispersive x-ray spectroscopy (STEM/EDS) and compared to results from Auger electron spectroscopy (AES). Comparison of the dose dependence for HP-304L and Fe- 20Cr-24Ni shows that RIS is alloy specific. The approach to steady-state Cr depletion was observed to be more rapid in the alloy with higher Ni content. Fe-2OCr-24Ni reaches a steady-state Cr depletion level by 0.5 dpa, and the amount of Cr depletion in HP-304L SS is still increasing between 1.0 and 3.0 dpa. RIS in the stainless steel alloys irradiated with 3.2 MeV protons is comparable to that in neutron irradiated steels of similar composition.
Amorphization of Ceramic Materials by Ion-Beam-Irradiation: Parallels to Glass Formation
Authors: Wang L. M. , Wang S. X. , Gong W. L. , Ewing R. C.
Published: April 2011

Ion-beam-induced amorphization of a wide variety of ceramic materials has been investigated using in situ TEM at the HVEM-Tandem Facility at Argonne National Laboratory with 1.5 MeV Kr+ or Xe+ ions at temperatures between 20 to 1000 K. The critical amorphization temperatures and the activation energies associated with the expitaxial recovery of displacement cascades during irradiation have been determined from the temperature dependence of the critical amorphization dose. The results for phases in the A12 O3-MgO-SiO2 system suggested a parallel in the kinetics between ion-beam-induced amorphization and glass formation. Based on a cascade quenching model, a semiempirical parameter, S, which can easily be calculated from both structural and chemical parameters of a material, has been developed to predict the susceptibility of ceramics to amorphization. The critical amorphization temperature, above which irradiationinduced amorphization cannot be completed, is closely related to the glass transition temperature. The ratio between glass transition and melting temperatures can also be used to predict the susceptibility of a ceramic material to amorphization, equivalent to the Debye temperature criterion.
Nondestructive Optical Characterization of Radiationhardened Polyimide Films
Authors: Logan Randy , Maznev A. A. , Nelson Keith A. , Megusar J.
Published: April 2011

A noncontact, nondestructive method is used to determine viscoelastic and thermal transport properties of a DuPont Kapton film before and after neutron irradiation to determine the changes that would be expected to occur in a nuclear reactor environment. The results demonstrate general capabilities for non-destructive evaluation (NDE) of radiation-induced material degradation. The specific application demonstrated is evaluation of insulation materials to be used in a superconducting magnet design in the International Thermonuclear Experimental Reactor (ITER).
Defects and Phase Change Induced by Giant Electronic Excitations With GeV Ions And 30MeV Cluster Beam
Authors: Thevenard P. , Beranger M. , Canut B. , Ramos S. M. M. , Bonardi N. , Fuchs G.
Published: April 2011

MgO and LiNbO 3 single crystals were bombarded with GeV swift heavy ions (Pb, Gd) and 30MeV C60 clusters to study the damage production induced by giant electronic processes at stopping power up to 100keV/nm. The defect creation was characterized by optical absorption, transmission electron microscopy (TEM) and Rutherford backscattering spectrometry in channeling geometry (RBS-C). In MgO point defects (F type centers) and extended defects (dislocation loops) were created by ionization processes in addition to those associated with nuclear collisions. The F-center concentration induced by electronic energy excitations was studied at different temperatures and as a function of the particle electronic energy losses. TEM revealed that dislocation loops were produced close to the particle trajectories and amorphization was never observed. On the opposite, in LiNbO3 continuous amorphous tracks were evidenced above a threshold near 5keV/nm. The dependance of this effects with various solid state parameters will be discussed.