bluuebunny/crossref_metadata_2025 huggingface dataset:
Structure and Growth of N2O Gate Oxynitrides
Authors: Ellis K. A. , Carr E. C. , Buhrman R. A.
Published: April 2011

A series of investigations have been conducted into the properties of N2O silicon oxynitride gate dielectrics, and the various methods of their growth. One of the principle advantages of these oxides is their resistance to interface state generation. This is linked to the presense of nitrogen near the substrate interface, where it is triply bonded to silicon. It is also demonstrated that during N2O-based furnace growth, the total concentration of NOx species varies strongly with the flow rate of N2O. This has been correlated to the temperature profile of the furnace, which can be affected by the exothermic decomposition of N2O. This property has been exploited to controllably adjust the rate of nitrogen incorporation by up to a factor of three. Although nitrogen incorporation during furnace processing is generally stable, it is shown that atomic oxygen is capable of removing previously incorporated nitrogen. Sources of atomic oxygen include the decomposition of N2O during RTP treatment, N2O processing in a high flow rate furnace, or from ozone annealing.
A Two-Step, Lightly Nitrided Gate Oxidation Process For Sub-0.5 μm Cmos Technology
Authors: Roy P. K. , Ma Y. , Flemming M. T.
Published: April 2011

This work describes a two-step, lightly nitrided gate oxidation process for sub-0.5 jtm CMOS technology. This process is a simple extension of conventional oxidation using an in-situ N2O post oxidation anneal for nitrogen incorporation. Light nitrogen incorporation (∼3%) near the Si/SiO2 interface has improved oxide characteristics such as defect density (Do.), wear-out (Nbd), breakdown (Vbd) and tunneling (VFN) without altering its charge trapping behavior. Impacts of nitridation are more significant for thinner (<65Å) gate oxides (GOX).
Trapping Behavior of Thin Siliconoxynitride Layers Prepared by Rapid Thermal Processing
Authors: Beyer R. , Burghardt H. , Reich R. , Thomas E. , Grambole D. , Herrmann F. , Scholz T. , Albrecht J. , Zahn D. R. T. , Gessner T.
Published: April 2011

Siliconoxynitride layers with thicknesses between 5 and 10 nm were grown on (100) oriented silicon by rapid thermal processing (RTP) using either N2O or NH3 as nitridant. In order to study the trapping behaviour at the interface and in the insulator bulk, capacitance-voltage (CV) and current-voltage (IV) measurements have been performed combined with different magnitudes of Fowler-Nordheim stress. In addition, Deep Level Transient Spectroscopy (DLTS) has been applied for interface state detection. Auger Electron Spectroscopy (AES) has been used to obtain depth profiles for Si, N, O and C. The deconvolution of the AES signal displays significant peak contributions related to intermedium oxidation states. Nuclear Reaction Analysis (NRA) was successfully applied for hydrogen detection in buried SiOxNy thin films.
An Optical Approach to Evaluating the Effects of Chlorine on the Quality Of Si/SiO2 Interfaces
Authors: Sherry Julia , Lowell John , Hossain Tim , Debusk Damon
Published: April 2011

In CMOS, the addition of chlorine particularly in TCA form to the growth of thermal oxides in logic technologies is well-known and pervasive. In addition to the increasing environmental concerns of chlorine use, one of the important parameters is the amount of metallic contamination due to transition metals such as Fe in the Si, and alkali metals like Na in the oxide since these phenomena effect both device performance and quality. However, the ability to measure this parameter on product material is not generally available due to inherent problems with most known methods. In this paper we report on the application of high-injection, frequency based optical surface photovoltage (SPV) and a more recent technique known as a contact potential difference (CPD) to both quantify and qualify as-grown oxides on CZ P-type silicon.
Adhesion Reliability of Cu-Cr Alloy Films to Polyimide
Authors: Ahn E. C. , Yu Jin , Oh T. C. , Park I. S.
Published: April 2011

CuCr alloys with varying Cr content were sputter deposited on polyimide films, and the metal/polyimide films were maintained under 350°C/N2 environment up to 10 hours for reliability measurements. Before exposure to 350°C, the peel strength increased proportionally with the Cr content in the alloy layer up to 17% and saturated. After exposure to 350°C, the peel strength dropped for all the specimens due to the formation of Cr2O3 at the metal/polyimide interface, and the effect was most drastic for the specimen with the lowest Cr content, which failed along the Cr-oxide/polyimide interface. Depletion of carbidic bonds at the metal/polyimide interface accompanied the oxide formation, and the result was quite devastating for the specimens with low Cr content in the alloy layer.
Effect of the Finite Source Material on Electromigration Performance of a Novel Interconnect Test Structure
Authors: Bui Nguyen D.
Published: April 2011

Effects of finite source material, in multilevel interconnect systems, on reliability has been investigated. Two types of novel test structures were used in this study: 1] asymmetrical design structure in width and thickness for the top and bottom conductor layers, 2] symmetrical design structure in width and thickness for the top and bottom conductor layers. The results of the asymmetric contact and via chains studies showed that the electromigration lifetimes were not effected by the difference in the magnitude of the finite source material. The electromigration lifetimes of the symmetrical via structure, in width and thickness for the top and bottom conductor layers, exhibited a strong dependence on the finite source material. A failure model is proposed to explain the effect of finite source material on electromigration performance in such interconnect systems.
RTA Processing of W-Polycide Dual-Gate Sub-Micron Structures for Low-Voltage CMOS Technology
Authors: Bevk J. , Furtsch M. , Georgiou G. E. , Hillenius S. J. , Schielein D. , Schiml T. , Silverman P. J. , Luftman H. S.
Published: April 2011

Deep submicron CMOS technology for low-power, low-voltage applications requires the use of symmetric n+/p+ poly gate structures. This requirement introduces a number of processing challenges, involving fundamental issues of atomic diffusion over distances of 1Å to ∼30μm. Two of the critical issues are dopant cross-diffusion between P- and NMOS devices with connected gates, resulting in large threshold voltage shifts, and boron penetration through the gate oxide. We show that in devices with W-polycide dual-gat:e structure most of these problems can be alleviated by using rapid thermal annealing, RTA, in combination with a few additional, simple processing steps (e. g., low-temperature recrystallization of a-Si layer and selective nitrogen coimplants). The RTA step, in particular, ensures thai: the boron activation in the p+ poly-Si remains high and negates any effects of arsenic cross-diffusion. CMOS devices with properly processed gates have low gate stack profiles, small threshold voltage shifts (<30mV), and excellent device characteristics.
Evaluation of Applied Materials' Rapid Thermal Processor Using SEMATECH Methodologies for 0.25 m Technology Thermal Applications-Part I
Authors: Riley Terrence J. , Nanda Arun K. , Miner Gary , Pas Michael F. , Hossain-Pas Sylvia , Velo Lino A.
Published: April 2011

Under a joint development contract with Applied Materials (AMAT) and Texas Instruments (TI), SEMATECH undertook a project (Joint Development Project J100) with a goal of delivering a cost effective, technically advanced Rapid Thermal Processor (RTP). The RTP tool was specified to meet the present and future manufacturing needs of SEMATECH's member companies. The J100 results contained here will focus on the temperature and control performance of the AMAT RTP tool. The evaluation methodology included passive data collection (PDC) to check the tool stability, screening experiments to isolate the variable interaction and to define the process window, broad range and narrow range sensitivity studies to determine the sheet resistance dependence on thermal budget for small increments in temperature set point, perturbation experiments to determine localized control, and stability experiments to check for drift and process repeatability. The impact of wafer emissivity on source/drain rapidthermal annealing was evaluated by processing wafers with varying backside films. The PDC experiments demonstrated the tool to be stable. Screening experiments revealed the strong effect of temperature, followed by time, and time-temperature interaction on sheet resistance. Boron implanted (p+/n) wafers were found to be sensitive at a temperature of 1025 °C or less for a 10 second anneal whereas arsenic implanted wafers (n+/p) showed greater sensitivity at temperatures ranging from 1025 °C to 1100 °C for a 10 second anneal.
Studies of the Effect of Various Gas Species on Si-SiO2 Interface Charges and Surface Roughness for Rapid Thermal Deposited Gate Oxides
Authors: Bayoumi A. M. , Hauser J. R.
Published: April 2011

The formation of Si-SiO2 interfaces for 40–60Å rapid thermal CVD (RTCVD) MOS gate oxides has been studied, using cluster tool technology. SiH4/N2O chemistry is used to deposit stoichiometric oxides. In-situ thermal treatments, prior to oxide deposition, typically at 800–900°C, 30–60 sec, and 50 Torr. are conducted using O2, N2O, SiH4, NH3, HCl/N2 and HCl/O2. The effect of gas flow ratios during temperature ramp-up for RTCVD interface formation is also studied. This paper presents a new quick-turnaround approach for non-destructive evaluation of Si-SiO2 interface quality for fully fabricated devices, in terms of interface charges and surface roughness.
Thin Nitride Films: Pushing the Limits Using Rapid Thermal Processing
Authors: DeBoer S. J. , Thakur R. P. S.
Published: April 2011

Silicon nitride, a celebrated dielectric material in semiconductor processing, is used extensively in almost all of today's key technologies (DRAM, microprocessor, SRAM, Flash memories, etc.). The physical and electrical properties of this material are well understood, and integration of silicon nitride in a given process is simple. As a result of these benefits, alternate dielectric material technologies have found limited acceptance. As feature sizes shrink, the formation of reliable thin nitride films is critical and the performance of these nitride films is very dependent on the technology used for their preparation. In this paper, we show that an incremental and overall improvement in the physical and electrical properties of nitride films can be attained by using rapid thermal processing technology.

We present the nucleation behavior of the <100 Å nitride films on polysilicon surfaces. We investigate the integrity of these films as a function of predeposition environment and discuss the oxidation and punch-through resistance of cluster tool-deposited films. The results of our studies of the conduction mechanism in thin silicon nitride films and scaling limits for these films are shown. We also discuss the structural and electrical changes these films undergo during the subsequent reoxidation process performed for leakage current reduction.
GOI Impact of Cu, Ni and Al Atoms on the Wafer Surface Prior to RTP and Furnace Oxidations
Authors: Aderhold W. R. , Shah N. , Bogen S. , Bauer A. , Burte E. P.
Published: April 2011

The effects of Al, Cu, and Ni on Gate Oxide Integrity (GOI) are evaluated in a critical process sequence relevant for current CMOS technology. The test process is designed to evaluate the GOI effect of these metals after multiple oxide growth and strip steps. This work compares oxide growth in a furnace and Rapid Thermal Processing (RTP). Wearout and E ramp measurements show that Ni contamination is detrimental for GOI only after multiple oxidations. Atomic Force Measurement (AFM) showed that precipitates (presumably NiSi2) form at the interface during the first oxidation. These precipitates are oxidized during the next oxidation and lead to oxide surface roughness and local Fowler Nordheim (FN) current enhancements. RTP results in a higher density of these defects as compared to furnace oxidation. Cu is fast-diffusing into the substrate and leads to defects only during the n+-poly process. Therefore, no influence of the oxide process variations on the Cu defect formation was found. In addition, no difference for furnace or RTP processes was observed. Cu precipitates that form at the poly/oxide interface lead to very pronounced FN current enhancements. As Al is built in the oxide structure, no electrode roughness occurs that leads to FN current enhancement. RTP grown oxides are less affected by Al contamination. Al can be removed by stripping the oxide, whereas Ni and Cu cannot.
Effects of Reflective Surfaces on Silicon Emissivity and Temperature Measurements
Authors: Xu H. , Sturm J. C.
Published: April 2011

The effects of front-side reflective surfaces on the emissivity and temperature measurement of silicon wafers in a Rapid Thermal Processing chamber with backside heating are examined through optics modeling. Two schemes are contrasted. In (1), the pyrometry detector looks at the back-side of the wafer; in (2), it looks at the front-side of the wafer. In both cases, the temperature errors occur when the reflector's reflectivity deviates from unity. However, the error dependence on the reflector reflectivity exhibits interesting differences in these two schemes. Under the working conditions proposed in this paper, a non-ideal reflector introduces a bigger temperature error in the “backside-detector” scheme than in the “front-detector” scheme. Practical implications of these results are also discussed.
Emissivity Independent Process Control in a Short Wavelength ARC Lamp RTP Chamber
Authors: Lefrançois Marcel E. , Camm David M. , Hickson Brendon J.
Published: April 2011

Two dimensional temperature measurements of patterned wafers are presented. The measurements are made using a commercially available CCD camera operating at λ=900nm, yielding a spatial resolution of 1 pixel per mm2 and a relative accuracy of ±0.25 °C. The emissivity is determined using a reflectivity measurement made possible by the unique properties of a short wavelength arc lamp RTP chamber. The use of this measurement system for closed loop control is discussed and the application to maintaining accurate time temperature profiles independent of emissivity is described.
Memory Effect in RTCVD Epitaxy of Si and SiGe
Authors: Rittier G. , Tillack B , Wolansky D.
Published: April 2011

In the paper presented the memory effect of boron (B), phosphorus (P), and germanium (Ge) have been studied during the chemical vapor deposition of homoepitaxial Sifilms and heteroepitaxial SiGe- layers in different RTCVD equipment. The CVDprocesses were controlled by surface kinetics on Si substrates from H2, SiH4, GeH4, PH3, and B2H6 at the pressure of 2 mbar in the temperature range of 500°cC–700°C. T1e aufodoping effect from the wafer has been separated from the loading effect of the reactor. The memory effect has been shown to be small for Ge in Si and for B in Si and SiGe. However, a remarkable high memory effect has been found for P, especially in SiGe-films. There are different methods reducing the memory effect in RTCVD-reactors. In-situ gas phase etching by HCI or NF3 gives the best results in the reactors studied here. Based on the obtained results the opportunities and limitations of integrated processing of different Si and SiGe-films (e.g. complete stacks for Si/SiGe-HBT) in the same reaction chamber have been discussed.
Microwave Processing Applied to Ceramic Reactions
Authors: Gonzalez M. , Gomez I. , Aguilar J.
Published: April 2011

The necessary energy for processing ceramics usually comes from gas firing or electricity. With gas firing, ceramics processing is conducted at relative low temperatures. In the case of electric arc furnace, temperatures are high enough to smelt the material and the reaction takes place in a liquid state. In this work we use microwave radiation for conducting reactions between oxides to produce ceramic materials, mainly spinels. The microwave energy was supplied using an 800W magnetron operating at 2.45 GHz. The microstructure and the mineral composition were studied by means of SEM and X-Ray diffractometer respectively.
Continuous Processing of Sheet-Like Materials by Microwave Energy
Authors: Lewis David A. , Whitehair Stanley J. , Viehbeck Alfred , Shaw Jane M.
Published: April 2011

Initial results for the continuous microwave processing of wide webs using a new microwave applicator are presented. The results show that acceptable uniformity can be obtained using this system and that with the appropriate controls, a very tight process window can be maintained to produce preimpregnated glass cloth (prepreg) for use in circuit board manufacture.
Microwave Sintering of Large Products
Authors: Saji Tasaburo
Published: April 2011

A practical microwave ceramic sintering technology has been developed. To achieve the highest merit from microwave sintering, susceptors were not used. In this paper, the ceramic sintering process using the 28GHz mm-wave energy generated by a Gyrotron oscillator is described. Large sized (Φ 200 × 200 ) and complex shaped material of Si3N4, A12O3, and ZrO2 were successfully and reproducibly sintered. The sintered bodies exhibited high density and fine crystalline structure. The processed materials were found to have exceptional strength and toughness.

The critical processing technology developed dealt with the means by which uniform and defect free sintered bodies are obtained. The processing stressed the importance of achieving a uniform electric field within the applicator and to decrease the sintering dependence on the materials’ temperature based dielectric loss properties. With the use of innovative support and thermal insulation structures, the processing system allowed for very precise temperature controls.
Processing and Characterization of Microwave and Conventionally Sintered Bulk YBCO High-Tc Superconductors
Authors: Al-Dawery I. A. H , Binner J. G. P. , Cross T. E.
Published: April 2011

The use of microwave energy for the sintering and annealing of high-Tc YBCO superconductors has been investigated with a view to taking advantage of the opportunities presented by this heating technique. It has been found to offer the possibility of sintering 'from the inside out' due to the nature of the temperature profile developed and as a result bulk YBCO bodies measuring 35 mm in diameter by 5 mm thick have been produced with completely uniform and high oxygen content (x = 7 in Yba2Cu3Ox) and densities of ≈ 98% of theoretical. These properties were achieved using processing times approximately one sixth of those required conventionally. A model for the microwave heating process is proposed.
Microwave Reaction Sintering of Tungsten Carbide Cobalt Hardmetals
Authors: Gerdes T. , Willert-Porada M. , Rödiger K. , Dreyer K.
Published: April 2011

Microwave reaction sintering of tungsten- carbon-, cobalt mixtures is described as a method that combines the liquid phase reaction sintering of tungsten carbide cobalt hardmetals with the enhanced densification behavior of hardmetals in the microwave field. Starting with green parts composed of W-, Co- powder, soot as carbon source and with varying amount of additives a dense and extremely fine grained hardmetal can be obtained in one pressureless microwave reaction sintering step.

By this method hardmetals with improved mechanical properties can be obtained in a drastically simplified processing cycle, without time consuming steps such as carburizing and milling.
Cavity Effects and Hot Spot Formulation Inmicrowave Heated Ceramic Fibers
Authors: Kriegsmann G. A.
Published: April 2011

Recently the heating of a thin ceramic cylinder in a single mode applicator was modeled and analyzed assuming a small Biot number and a known uniform electric field through out the sample. The resulting simplified mathematical equations explained the mechanism for the generation and growth of localized regions of high temperature. The results predicted that a hot-spot, once formed, will grow until it consumes the entire sample. Most experimental observations show that the hot-spot stabilizes and moves no further.

A new model is proposed which incorporates the effect of the cavity and the nlonuiniform character of the electric field along the axis of the sample. The resulting simplified mathematical equations indicate that these effects stabilize the growth of hot-spots.
Dielectric Measurement Of Multi-Layered Medium Using An Open-Ended Waveguide
Authors: Tantot O. , Chatard-Moulin M. , Guillon P.
Published: April 2011

The use of a circular waveguide radiating into a multi-layered media allows the characterization of heterogeneous and fluid subtances. Many microwave measurement devices, based on reflection coefficient measurements, are subjected to air gap problems that introduce some inaccuracy in the determination of the unknown complex permittivity of the materials. Our purpose is to try and take the air gap into account in these measurements.
Measurement Of The Dielectric Properties Of Polystyrene Particles In Electrolyte Solution
Authors: Grosse C. , Tirado M. C.
Published: April 2011

The permittivity and conductivity of suspensions of spherical sub micron size polystyrene particles were measured in the 10 kHz to 10 MHz frequency range using a HP 4192A Impedance Analyzer. Due to the high conductivity of the samples (0.1 to 0.6 S/m) every detail of the measurements had to be optimized. For each sample, the instrument was calibrated as an electric quadrupole, by means of short, open, and reference measurements, using for this last a standard electrolyte with a conductivity similar to that of the sample. The results obtained were combined with measurements in the 1 MNHz to 28 GHz range made in Goettingen, Germany, using precisely the same samples. The final spectra cover the broadest frequency range to date for these systems.
3-D Temperature Distributions Produced by a Microwave Spot Heating Applicator
Authors: Roos R. M. , Thomas J. R.
Published: April 2011

Numerical simulations were used to investigate the effectiveness for materials processing of recently announced microwave spot-heating applicators. These devices can produce heating in depth over a region a centimeter or two in diameter. Computed 3-D time-dependent temperature distributions for both stationary and moving samples suggest that such applicators could be very useful for joining of ceramics, such as alumina. Moving the beam relative to the workpiece at an appropriate rate avoids thermal runaway.
High-Frequency Field Effects on Ionic Defect Concentrations and Solid-State Diffusion Processes
Authors: Freeman S. A. , Booske J. H. , Cooper R. F.
Published: April 2011

We describe computer simulations of a microwave-induced driving force for ionic transport. The simulations are based on a model which predicts rectification of ionic fluxes at interfaces and a resulting depletion or accumulation of defects near the interface. Some details of the model are discussed, results of the simulations are presented, and the impact of these effects on sintering and diffusion is discussed.
Modifications on Bulk Crystallization of Glasses Belonging to M2O-CaO-SiO2-ZrO2 System in A 2.45 GHz Microwave Field
Authors: Siligardi C. , Leonelli C. , Fang Y. , Agrawal D.
Published: April 2011

The potential for microwave processing of a single phase material is often limited due to the dependence of dielectric losses upon the chemical bonding and temperature of the material. We will present results showing the effect of microwave absorption on bulk crystallization of glasses belonging to M2O-CaO-SiO2-ZrO2 system (where M+ Li, Na, K). The glass samples were devitrified using both microwave and conventional heating. The effect of Li+, Na+, K+ on crystallization is quite remarkable and is a function of ion size. This is true especially in the microwave heating where the important dielectric losses observed in silicate glasses are related to the motion of alkali cations throughout the glass matrix. X-ray diffraction analysis was performed on the powdered samples to determine crystalline phases. Results of microstructure and microanalysis on these glass-ceramic samples will also be presented.
Adhesive Bonding Via Exposure to Variable Frequency Microwave Radiation
Authors: Paulauskas Felix L. , McMillan April D. , Warren C. David
Published: April 2011

Adhesive bonding through the application of variable frequency microwave (VFM) radiation has been evaluated as an alternative curing method for joining composite materials. The studies showed that the required cure time of a thermosetting epoxy adhesive is substantially reduced by the use of VFM when compared to conventional (thermal) curing methods. Variable frequency microwave processing appeared to yield a slight reduction in the required adhesive cure time when compared to processing by the application of single frequency microwave radiation. In contrast to the single frequency processing, the variable frequency methodology does not readily produce localized overheating (burnt or brown spots) in the adhesive or the composite. This makes handling and location of the sample in the microwave oven less critical for producing high quality bonds and allows for a more homogeneous distribution of the cure energy. Variable frequency microwave processing is a valuable alternative method for rapidly curing thermoset adhesives at low input power levels.
Microwave Treatment of Emissions From Waste Materials
Authors: Schulz R. L. , Folz D. C. , Clark D. E. , Schmidt C. J. , Wicks G. G.
Published: April 2011

A microwave off-gas system has been designed and fabricated to destroy or decompose emissions that arise from microwave treatment of printed circuit boards (PCBs). Preliminary gas chromatography data on emissions that resulted from combustion of PCBs showed significant decreases in the concentration and number of hazardous compounds detected in the off-gases after treatment. Investigations have continued in this area to demonstrate the reproducibility of the initial results and to determine critical control parameters for optimization of the system. The results of these studies are presented.
Monitoring Resin Cure Of Medium Density Fiberboard Using Dielectric Sensors
Authors: King R. J. , Rice R. W.
Published: April 2011

Flush mounted, in-press microwave (600–800 MHz) sensors have been developed for monitoring the complex permittivity in real time during the cure of medium density fiberboard. The measured dielectric constant (ε')a nd loss factor (ε") are independent diagnostic indicators of dynamic cure events that are catalyzed by heat, pressure and moisture. In particular, with this technique the instantaneous effects of resin viscosity, rate and degree of adhesive cure, the wood density, the changes in phase of the moisture and the rate of moisture depletion can be monitored during the entire curing process.

The comparative roles of moisture and adhesive content are discussed, along with the comparative modulus of rupture with cure duration. Results are presented comparing the dynamics of phenol-formaldehyde and isocyanate resins.
Mapping the ε” of Conducting Solid Films in Situ
Authors: Werner M. J. , King R. J.
Published: April 2011

Two nondestructive microwave methods for sensing and mapping the local loss factor ε” of conducting solid films are described. Example results of both methods are compared to the low frequency sheet resistance as measured by two- and four-point probe methods. Specimens ranged from 26 to 10,000 ohms per square. Depending on the test frequency, spatial resolution of about 1 cm is achievable, as demonstrated by maps of ε”.
Transient Enhanced Diffusion of Boron in Silicon:The Interstitial Flux
Authors: Simpson T. W. , Goldberg R. D. , Mitchell I. V. , Baribeau J.-M.
Published: April 2011

Delta-doped boron marker layers in silicon have been used to test further the relationship between B transient enhanced diffusion (TED) and the flux of silicon interstitials released during the annealing stage following self implantation. We present new data which address a number of questions raised by the present models. We show that in our experiments bulk trapping of interstitials is significant only for low implant fluences (˜1012 cm2). The origin of the observed diffusion-like profiles for the interstitial flux is instead found to lie in local trapping within the δ-doped layers themselves. Boron trapped in immobile clusters may be associated with Si interstitials in approximately a 1:1 ratio; nevertheless this trapping contribution alone may not entirely account for the observed gradient. We suggest that some part of the observed TED response with depth is attributable to local trapping of silicon interstitials within the boron doped layers.
Investigations of Plasma Immersion Ion Implantation Hydrogenation for Poly-Si Tfts Using an Inductively Coupled Plasma Source
Authors: Zhou Yuanzhong , Qin Shu , Chan Chung
Published: April 2011

A plasma immersion ion implantation (Pill) hydrogenation process using an inductively-coupled plasma (ICP) source is implemented for defect passivation in polycrystalline silicon (poly-Si) thin film transistors (TFT's). Device parameter improvement saturates in 4 minutes, which is considerably shorter than for other reported hydrogenation methods. Stress test indicates that the devices hydrogenated by this novel technique have much better long-term reliability. The hydrogenation effects on two types of trap states are analyzed the current-voltage characteristics of the devices. The densities of deep states and tail states are significantly reduced after short time hydrogenation.
Cascade Defects Beyond the Primary Damage State
Authors: Heinisch H. L.
Published: April 2011

Atomic scale computer simulations are used to investigate the intracascade evolution of the defect distributions of cascades in copper over macroscopic times. Starting with cascades generated using molecular dynamics, the diffusive transport and interactions of the defects are followed for hundreds of seconds in stochastic annealing simulations. The temperature and energy dependencies of annihilation, clustering and free defect production are determined for individual cascades. The simulation results illustrate the strong influence on intracascade evolution of the defect configuration existing in the primary damage state. Other significant factors affecting the evolution of the defect distribution are the large differences in mobility and stability of vacancy and interstitial defects and the rapid one-dimensional diffusion of small, glissile interstitial loops produced directly in cascades. The latter factor introduces a cascade energy dependence of defect evolution that is apparent only beyond the primary damage state, amplifying the need for performing many more cascade simulations at higher energies.
Defect Cluster Structure and Tensile Properties of Copper Single Crystals Irradiated With 600 MeV Protons
Authors: Dai Yong , Victoria Max
Published: April 2011

The defect microstructures and tensile properties of high purity copper single crystals have been studied after irradiation at room temperature with 600 MeV protons in the dose range from 10-3to 10-1dpa. The defect number density N of clusters shows a linear dependence with dose up to a saturation value of 4×1023m-3, with a broad transition region between doses of 3×10-3and 10-1dpa. The increase in critical resolved shear stress (CRSS) induced by the irradiation is proportional to the square root of the dose, up to a dose of 7×10-3dpa. These results are compared to those of both fission and fusion neutron irradiations, showing that in room temperature irradiations at low fluences, no recoil spectra effects can be detected.
Effects of Heavy-Ion Irradiation on Microstructure of V-4Cr-4Ti Alloy at Moderate Temperatures
Authors: Gazda J. , Chung H. M. , Loomis B. A. , Meshii M.
Published: April 2011

V-4 wt.% Cr-4 wt.% Ti alloy is a promising candidate material for first-wall and structural applications in magnetic fusion reactors. In the past, fast neutron sources were used to evaluate postirradiation properties of fusion candidate materials. The recent shutdowns of the Fast Flux Test Facility (FFTF) and the Experimental Breeder Reactor (EBR-II) left U.S. researchers without local experimental facilities for such tests. Under such circumstances, ease of experimental control, availability, and relatively low cost make heavy-ion irradiation an attractive alternative, provided its limitations are appreciated. We selected 3-MeV V+ and 4.5-MeV Ni++ ions to investigate the effects of irradiation on the microstructure of V-4Cr-4Ti alloy in the temperature range of 200 – 420°C. The main interest is in the evaluation of this alloy's dimensional stability and susceptibility to irradiation embrittlement. In this paper, we report results of ion irradiation experiments and compare them with available data on fast-neutron irradiation. From transmission electron microscopy (TEM) analysis of ion-irradiated specimens, we found that the dominant feature of the postirradiation microstructure was a high density of dislocation loops and pointdefect clusters. Density and defect size depended on irradiation dose and temperature. Precipitates and voids/bubbles were not observed, even in specimens that were simultaneously injected with He and exposed to heavy-ion irradiation. Increased transport of point defects to internal interfaces was observed, as manifested by defect denuded zones along grain boundaries, Defect denuded zones along grain boundaries could lead to segregation of impurities and solutes and formation of precipitates on grain boundaries.
Defect Microstructures and Deformation Mechanisms in Irradiated Austenitic Stainless Steels
Authors: Bruemmer S. M. , Cole J. I. , Carter R. D. , Was G. S.
Published: April 2011

Microstructural evolution and deformation behavior of austenitic stainless steels are evaluated for neutron, heavy-ion and proton irradiated materials. Radiation hardening in austenitic stainless steels is shown to result from the evolution of small interstitial dislocation loops during lightwater-reactor (LWR) irradiation. Available data on stainless steels irradiated under LWR conditions have been analyzed and microstructural characteristics assessed for the critical fluence range (0.5 to 10 dpa) where irradiation-assisted stress corrosion cracking susceptibility is observed. Heavy-ion and proton irradiations are used to produce similar defect microstructures enabling the investigation of hardening and deformation mechanisms. Scanning electron, atomic force and transmission electron microscopies are employed to examine tensile test strain rate and temperature effects on deformation characteristics. Dislocation loop microstructures are found to promote inhomogeneous planar deformation within the matrix and regularly spaced steps at the surface during plastic deformation. Twinning is the dominant deformation mechanism at rapid strain rates and at low temperatures, while dislocation channeling is favored at slower strain rates and at higher temperatures. Both mechanisms produce highly localized deformation and large surface slip steps. Channeling, in particular, is capable of creating extensive dislocation pileups and high stresses at internal grain boundaries which may promote intergranular cracking.
Microstructure Evolution of Selected Ferriticmartensitic Steels under Dual-Beam Irradiation
Authors: Wanderka Nelja , Camus Eric , Wollenberger Heinrich
Published: April 2011

We present experimental results on the microstructure evolution of dual-beam irradiated (300 keV heavy ions plus 15 keV helium ions) ferritic-martensitic steels (Manet, DIN 1.4926, F82H mod). The helium bubble morphology as well as microchemistry of the alloys are investigated by means of transmission electron microscopy and field-ion microscopy with atom probe. The alloys were irradiated to fluences up to 50 dpa and implanted with helium up to a concentration of 1 at.% at the temperatures of 723 K and 773 K. The damage and implantation rates variied from 2.5 · 10−3 dpa/s to 2.5·10−2 dpals and from 0.5 appmls to 5 appm/s, respectively. Size and number density of helium bubbles is found to be rate dependent. Smaller implantation rates produce larger helium bubbles and smaller bubble number densities. Regions of local enrichment of alloy elements, typically 5 nm in size, containing chromium (up to 40 at.%), silicon, and nickel are detected. Number densities of helium bubbles and of regions of chromium enrichments are comparable and lie between 1023/m3 and 1024/m3. Possible extrapolation of the present ion irradiations to spallation source and fusion reactor conditions is shortly adressed.
Computer Simulation Study of the Effects of Copper Precipitates on Dislocation Core Structure in Ferritic Steels
Authors: Harry T. , Bacon D. J.
Published: April 2011

The small, coherent BCC precipitates of copper that form during fast neutron irradiation of ferritic steels are an important component of in-service irradiation hardening. Many-body interatomic potentials for the Fe-Cu alloy system have been developed and used to simulate the atomic structure of the ½<111> screw dislocation in both pure a-iron and the metastable BCC phase of copper. In iron, the core has the well-known 3-fold form of atomic disregistry. In BCC copper, however, the core structure depends on the lattice parameter. At the metastable equilibrium value, the core is similar to that in iron, but as the lattice parameter is reduced, as in a precipitate, the core becomes delocalised by transformation of the copper. Simulation of dislocated crystals containing precipitates shows that the extent of this effect depends on precipitate size. The energy changes indicate a significant dislocation pinning effect due to this dislocation-induced precipitate transformation process.
Computer Simulation Study of the Effects of Copper Solutes on Cascade Damage in Fe-Cu Alloys
Authors: Calder A. F. , Bacon D. J.
Published: April 2011

The production of small, coherent BCC precipitates of copper during fast neutron irradiation of ferritic steels and their apparent stability at peak hardening size are important phenomena governing in-service irradiation embrittlement. An MD model employing manybody interatomic potentials for the Fe-Cu alloy system has been developed and used to simulate the effect of displacement cascades on both dilute random solid solutions of copper and small coherent BCC copper precipitates in an oa-iron matrix. Within the timescales that can be modelled, cascades caused only small changes to the distribution of copper atoms in both the solid solution and the precipitate studies. Vacancies are observed to bind to copper solute atoms and also to accumulate in precipitates near the interface, where they are mobile. Interstitials are mobile in the solid solution matrix and two mechanisms of interstitial entrapment by precipitates are indicated.
A Comparison of Grain Boundary Monolayer Segregation Measurements Made Using Fegstem and Auger Spectroscopy
Authors: Fisher S. B. , Spellward P. , Scowen R. , Lee B.
Published: April 2011

The active electron optics suite at Magnox Electric's Berkeley Centre has a VG HB501 FEGSTEM and a FE-sourced Auger Microprobe (a Fisons Microlab-F) which are routinely used for grain boundary chemistry studies in a variety of highly active austenitic and ferritic steels and nickel base alloys.

In a number of investigations sufficient grain boundary data have been obtained to allow a meaningful comparison between the two instruments to be made. It has been established that for the overwhelming majority of materials and conditions there exists a reasonable correlation between the two sets of compositional (on-boundary) data.

This paper presents this correlation and gives a simple theoretical description justifying the relationship between the raw data from the instruments. Examples are given of materials and conditions for which the correlation cannot be established and this leads to a discussion of the usefulness of the availability of the correlation.
Effects of Ion Implantation and Temperature on Radiation-Induced Segregation In Ni-9Al Alloys
Authors: Giacobbe M. J. , Lam N. Q. , Okamoto P. R. , Zaluzec N. J. , Stubbins J. F.
Published: April 2011

The effects of Ne and Sc implantation on radiation-induced segregation (RIS) in Ni- 9at.%Al were studied in-situ utilizing the high-voltage electron microscopeffandem accelerator facility at Argonne National Laboratory. A highly-focused 900-keV electron beam generated radial defect fluxes which, in turn, induced the transport of Al atoms toward the center of the electronirradiated area via the inverse-Kirkendall effect. The radial segregation rate of Al atoms was monitored by measuring the diameter of the γ′-Ni3Al zone which formed in the Al-enriched area during irradiation. Ne and Sc implantation effects on RIS were investigated at 550°C, while Ne effects were also examined at 625°C to determine the influence of temperature on the ability of Ne to act as defect trapping sites, causing RIS suppression. It was found that the RIS suppression effect of Ne increased with increasing irradiation temperature, and that Sc had a small RIS suppression effect which increased with increasing Sc implantation dose. Ne bubbles which formed during implantation are believed to be responsible for its strong suppression effect.
Refinement of Irradiation and Analysis Techniques for Radiation-Induced Segregation
Authors: Allen T. R. , Cookson J. M. , Damcott D. L. , Was G. S.
Published: April 2011

Radiation-induced segregation (RIS) has been implicated as a potential contributor to irradiation assisted stress corrosion cracking in light water reactor core components. To better understand changes to grain boundary chemistry during irradiation, RIS was measured in ultra-high purity (UHP) 304 stainless steel using Auger electron spectroscopy (AES). Variations in measured grain boundary concentration, both within a sample and between samples, are reduced by refinements in both the radiation and the AES techniques. These refinements include improvements in temperature control, uniformity of sample-to-sample dose, grain boundary acceptance criteria, amount of intergranular fracture, and amount of beam current used in analysis. AES measurements on samples irradiated at 400°C to 1.0 dpa show how implementing the technique refinements reduces the variability in the measured concentrations. Additionally, measurements from regions of ductile tearing in samples irradiated to 0.1 and 1.0 dpa at 400°C, to 1.0 dpa at 200°C, and from unirradiated samples show that sensitivity factors must be determined to obtain the most accurate measurement of grain boundary composition.
Ab Initio Pseudopotential Calculations of Carbon Impurities In SI
Authors: Zhu Jing , Diaz De La Rubia T. , Mailhiot Christian
Published: April 2011

Ab initio planewave pseudopotential method is used to study carbon diffusion and pairing in crystalline silicon. The calculation is performed with a 40 Ry planewave cutoff and 2×2×2 special k-point sampling with a supercell of 64 atoms. It is found that substitutional carbon attracts interstitial Si forming a <001> C interstitial with a large binding energy of 1.45 eV. The interstitial carbon is mobile and can migrate with a migration energy of 0.5 eV. The interstitial carbon can bind further to another substitutional carbon forming a substitutional carbon-interstitutional carbon pair with a binding energy of 1.0 eV. This model is used to understand the effect of high C concentration on the transient enhanced diffusion in Si.
Behaviour of Zirconia Based Fuel Material Under Xe Irradiation
Authors: Degueldre C. , Heimgartner P. , Ledergerber G. , Sasajima N. , Hojou K. , Muromura T. , Wang L. , Gong W. , Ewing R.
Published: April 2011

The behaviour of ZrO2-10%YO1.5-5%ErO1.5-( 10%ThO2) (At %) cubic solid solutions under low and high energy Xe ion irradiation up to a fluence of 1.8·1016 Xe.cm−2 was investigated by TEM. Low energy (60 keV) Xe ions did not yield amorphization. From the observed bubble formation, swelling values of less than one volume per cent were estimated to be 0.19–0.72% during irradiation at room temperature or at high temperature (925 K). Furthermore, no amorphization was obtained by Xe irradiation under extreme conditions such as high energy (1.5 MeV) Xe ion and low temperature (20 K). This confirms the robustness of this material and argues in favour of the selection of zirconia based material as an advanced nuclear fuel for plutonium disposition.
Electron Beam Driven Disordering in Small Particles
Authors: Vanfleet Richard R. , Mochel Jack
Published: April 2011

Small metal particles in the range of a few nanometers in diameter are seen to progressively disorder when the 100 keV electron beam of a Scanning Transmission Electron Microscope (STEM) is held stationary on the particle. The diffraction pattern of the individual particle is seen to progress from an initial array of indexable diffraction spots to a mixture of diffraction spots and amorphous-like rings and finally to rings with no persistent diffraction spots. After the electron beam is removed, the particles will recrystallize after minutes or hours. Only particles below a critical size are seen to fully disorder. We have observed this in Platinum, Palladium, Rhodium, and Iridium and based on our model of disordering process believe it is a universal effect. It has also been observed with a Platinum Ruthenium alloy. We discuss the mechanism of this disordering and the structure of the resulting disordering particle for the case of Platinum clusters.
Determination of the Electron Beam-Induced Shrinkage Rates Of Isolated Amorphous Zones In Germanium
Authors: Jenčič I. , Robertson I. M. , Skvarč J.
Published: April 2011

Epitaxial regrowth of isolated amorphous zones, created in Ge by implantation with 50 keV Xe+ ions, was stimulated at room temperature by using electron beams with an energy below that required to create Frenkel pairs. The process was studied by using transmission electron microscopy combined with an automatic computer image analysis program, and the regrowth was characterized by determining the shrinkage rate of the effective radius of individual zones. The effective radius decreases approximately linearly with electron dose. The regrowth rate of irregular shaped amorphous zones is fast initially and slows as the shape of the amorphous zone becomes more regular. Only one regrowth rate is found for amorphous zones with a regular shape. The regrowth rate increased with decreasing energy below the threshold displacement voltage, suggesting that electronic excitations are able to induce epitaxial growth.
The Effect of Impurity Content and Ion Mass on the Depth Profiles of Vacancy-Type Defects in MeV Implanted Si
Authors: Libertino S. , Coffa S. , Privitera V. , Priolo F.
Published: April 2011

We used deep level transient spectroscopy to determine the concentration and depth profile of the defects introduced by MeV He and Si implants in n-type crystalline Si. We have found that only ˜ 16% of the Frenkel pairs generated by the ion escapes recombination and is stored into room temperature stable defects such as divacancies and oxygen vacancy complexes. For a light ion (He), the depth distribution of these defect complexes is strongly dependent on the O content of the substrate: it mirrors the initial distribution of I–V pairs, as calculated by TRIM (a Monte Carlo Code) when the O content is high (˜1018/cm3) while it can be much wider (up to 2 μm) in a highly pure (low O content) epitaxial substrate. This effect is due to a long range migration of vacancies before clustering or trapping at impurities. This migration is strongly inhibited for an ion of higher mass (such as Si) since in a denser collision cascade direct clustering is strongly favoured with respect to agglomeration of migrating defects.