bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Engineering of Silicon Wafer Material Properties Through Vacancy Concentration Profile Control and the Achievement of Ideal Oxygen Precipitation Behavior
Authors: Falster R. , Gambaro D. , Olmo M. , Cornara M. , Korb H. 
Published: April 2011

AbstractA new kind of silicon wafer and a new class of materials engineering techniques for silicon wafers is described. This wafer, called the “Magic Denuded Zone” or MDZ wafer, is produced through the manipulation of the vacancy concentration and, in particular, vacancy concentration depth profiles in the wafer prior to the development of oxygen precipitates in subsequent heat treatments. The result is a wafer with ideal oxygen precipitation behavior for use in all types of integrated circuit applications. The methods used to prepare such wafers combine Frenkel pair generation with injection and the use of surface sinks. Simulations of the vacancy profiles produced by these techniques are presented and discussed. It is shown that within the range of vacancy concentration accessible by these techniques (up to ca. 1013 cm−3) the rate and oxygen concentration dependence of oxygen clustering can be substantially modified. Such techniques can be used to precisely engineer unique and desirable oxygen-related defect performance in silicon wafers both in terms of distribution and rate of defect formation. One result of the application of such techniques is an ideally precipitating silicon wafer in which the resulting oxygen precipitate profile (denuded zone depth and bulk density of precipitates) is independent of the concentration of oxygen of the wafer, the details of the crystal growth process used to prepare the wafer and, to a very large extent, the details of thermal cycles used to process the wafer into an electronic device. Optimal, generic and reliable internal gettering performance is achieved in such a wafer
Systematic Analyses of Practical Problems Related to Defects and Metallic Impurities in Silicon
Authors: Kitagawara Y. , Takeno H. , Tobe S. , Hayam Izu Y. , Koide T. , Takenaka T. 
Published: April 2011

AbstractSystematic approaches are introduced for (i) oxygen precipitation behavior, which is important for internal gettering, and (ii) segregation induced gettering behaviors of p/p+ epitaxial wafers and Poly-Si Back Seal (PBS) wafers. (i) Oxygen precipitation behavior during a whole sequence of a thermal process is predicted by a practical computer simulation technique involving a novel empirical function. The predicted oxygen precipitation behavior agrees with the corresponding experimental results reasonably well. (ii) For a systematic description of Fe segregation gettering, explicit expressions of the Fe segregation coefficients are obtained as functions of temperature and time. Using the determined expressions of the segregation coefficients and introducing diffusion dynamics, one can predict [Fe] behavior as a function of process time during a whole sequence of a thermal process. For both behaviors of(i) oxygen precipitation and (ii) segregation induced gettering, experimentally observed characteristics of a high-temperature process and a low-temperature process are well understood by aids of those simulations. (iii) For a high-sensitivity detection of an important heavy metal impurity Cu, we present a novel bulk impurity collection technique using a room-temperature Cu drift phenomenon accelerated by Corona charge showering on a Si wafer surface
Deep-Level Traps in CCD Image Sensors
Authors: Mccolgin William C. , Lavine James P. , Stancampiano Charles V. , Russell Jeffrey B. 
Published: April 2011

AbstractWe have extended by five the number of deep-level traps known to create dark current in charge-coupled device (CCD) image sensors. These include Mn, Pt, and three much weaker traps that are as yet unidentified. Using dark current spectroscopy (DCS) we show that the generation rates at 55°C range from 6400 electrons/s for Mn to only 2 electrons/s for the weakest trap, which lies 0.27 eV off mid-gap. These weak traps determine the bandwidths and resolution of the trap peaks seen in the dark current spectra.
Influence of Defect Clusters on the Performance of Silicon Solar Cells
Authors: Sopori Bhushan , Chen Wei , Nemire Karen 
Published: April 2011

AbstractImprovements in the techniques for the growth of Si substrates, used for commercial solar cells, have yielded wafers that exhibit low average defect density × typically less than 105 cm−2. We have observed that low defect density leads to the formation of defect clusters. This defect configuration influences the device performance in a unique way × by primarily degrading the voltage-related parameters. We discuss the nature of the defect clusters and show that they constitute regions of high carrier recombination. Network modeling is used to show that, in a device, these regions act as shunts that dissipate power generated within the cell.
Evaluating the Denuded Zone Depth by Measurements of the Recombination Activity of Bulk Defects
Authors: Polignano M. L. , Brambilla M. , Cazzaniga F. , Pavia G. , Zanderigo F. , Spiga S. , Moro L. , Castaldini A. , Cavallini A. 
Published: April 2011

AbstractA method for measuring denuded zone depth from lifetime measurements is proposed and compared to observations by microscopy techniques and to Electron Beam Induced Current (EBIC) analyses. The surface photovoltage (SPV) method is chosen for measuring lifetime, as it is found to be extremely sensitive to oxygen precipitation. Samples prepared according to three typical thermal hystories are used as test vehicles.Correlating the results given by the different techniques, this study points out a few relevant features from the point of view of wafer processing. For instance, processes starting with a low temperature treatment are poorly reproducible for what concerns oxygen precipitation and denuding, as shown by SPV data, and do not guarantee a defect-free denuded zone, as seen in EBIC images. Additional high temperature treatments during the process increase the denuded zone depth and improve uniformity.Techniques which rely on a selective etching for defect detection, such as the Secondary Electron method of Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM), are limited by etching sensitivy. On the other hand, the Transmission Electron Microscopy (TEM) statistics is too poor for this sort of observations. Instead, as a technique based on the recombination activity of defects, EBIC has roughly the same sensitivity as SPV. Both these techniques detect the formation of a denuded zone even when other methods fail, and can be considered as complementary tools.
Measurement of the Temperature Dependence of Silicon Recombination Lifetimes
Authors: Johnston S. , Ahrenkiel R. K. 
Published: April 2011

AbstractLifetime spectroscopy is a valuable tool in a number of silicon-based technologies. Currently, lifetime measurement is the most sensitive diagnostic for identification of lowlevel metal impurities in silicon by using the ratio of high-injection to low-injection lifetime. When a single impurity dominates recombination, the lifetime as a function of injection level provides a measure of the defect concentration. Another measurement parameter, that has not been commonly used, is the lifetime as a function of temperature. Temperaturedependent lifetime analysis leads to a better understanding of trapping-delayed recombination rates, trapping and recombination center energy levels and activation energies, temperaturedependent capture cross sections, and surface or grain boundary recombination or trapping effects. A contactless measurement technique has been developed that provides the sample's recombination lifetime over a temperature range from 80 K to 300 K. A sample is coupled to the measurement circuitry that is placed into a Dewar where it is cooled by liquid nitrogen. Lifetimes are then measured as the sample is allowed to warm to room temperature. Data will be shown on these variable-temperature lifetime measurements, which have been made on silicon wafer material ranging from high-quality float-zone-grown wafers to low-cost polycrystalline materials used in photovoltaics.
Point Defects in Relaxed Si1-xGex Alloy Layers
Authors: Mesli A. , Nylandsted Larsen A. 
Published: April 2011

AbstractThe use of compositionally graded buffer layers in the growth of fully relaxed epitaxial Si1−xGex alloy layers has led to a major improvement in crystalline quality. A considerable reduction in the density of the threading dislocations has become possible, facilitating point defect studies in these materials. The issues addressed in this review are inherent to the coupling between band gap engineering and defect-related levels. Among them, the pinning behaviour, charge state effects and their consequence upon the thermal stability of point defects are discussed together with the impact of the fluctuation in Ge distribution
High-Density, High-Thermal Dissipation Substrates Fabricated Using a Conductive Composite Material
Authors: Brandt Lutz , Matijasevic Goran , Gandhi Pradeep , Gallagher Catherine 
Published: April 2011

ABSTRACTThermal performance of conventional printed circuit materials can be increased with the use of heat sinks. Even better thermal dissipation can be achieved with the use of insulated metal boards as substrates. However, this technology is limited in the number of circuit layers and the circuit density. A novel material based on transient liquid phase sintering (TLPS) was developed and used to make additive multilayer circuits on metal substrates. The partial sintering operation of the polymer-based conductive composite is akin to that of Cermet materials, but processing is at temperatures of < 250° C. A metallurgically alloyed web is formed by TLPS, providing good conductivity and stability with respect to humidity and heat exposure. An interpenetrating polymer network provides adhesion to a variety of substrates.Photoimageable dielectrics have been used to image circuit traces (as fine as 50 μm) and vias (down to 75 μm). The conductive composite is filled into the grooves and cured to form circuits. Sequential building of circuit and via layers yields the desired planarized circuit with blind and buried solid vias throughout the multilayer structure. Metal substrates have been chosen to achieve high thermal dissipation. The thermal conductivity of the polymer-based conductive composite itself was measured to be 25 W/mK, comparable to that of solder materials. Thermally resistive adhesive interfaces have been minimized in the fabricating the structure, resulting in a high thermal dissipation, as well as high density substrate.
On The Influence Of Titanium Alloy Composition And Layer Thickness On The Mechanical Properties Of A Polyimide Substrate
Authors: Muralidharan G. , Narayanan B. , Wong C. C. , Manoharan M. 
Published: April 2011

ABSTRACTMetal-polymer bilayers and multilayers are being increasingly used in the microelectronics industry. In many cases, the reliability of the device or the package is determined by the mechanical behavior of these composite layers. Finite element analyses are being widely used to model these systems. An accurate experimental understanding of the mechanical behavior of these systems would further enhance the usefulness of such analyses. The present study focuses on the mechanical behavior of composite bilayers consisting of polyimide and sputtered Ti and Ti alloy thin films. Tensile tests and stretch-deformation tests have been performed on bilayers consisting of a polyimide substrate sputter-coated individually with a 50 nm and a 500 nm Ti layer, a 500 nm Ti-Cu layer, and a 500 nm Ti-Ni layer. Tensile moduli, stresses for 0.2%, 2% and 15% offset strains, and strains to failure have been obtained and compared. These values are discussed with reference to the known mechanical properties of the individual layers in the composite material.
Alloy Joints for High Temperature Electronic Packaging
Authors: So William W. , Lee Chin C. 
Published: April 2011

ABSTRACTHigh temperature joints are required for packaging and assembling the emerging high temperature semiconductor devices. A technique of producing high temperature joints at relatively low process temperature is presented. The technique uses liquid-solid interdiffusion to formulate the joint and subsequent solid-state diffusion and interaction to convert the joint material into high temperature alloy. Processes have been developed using the indium-silver binary material system. Joint melting temperature higher than 700°C has been achieved while the process temperature stays below 210°C. In this development effort, the constituent element materials are deposited in multilayer structure in high vacuum to prevent oxidation. As a result, no flux is used and no scrubbing action is applied. The joints produced are examined with a scanning acoustic microscope (SAM) to evaluate the bonding quality. The joint cross-sections are studied using SEM and EDX to find the microstructure and composition. In conventional processes, the process temperature needs to exceed the alloy melting temperature in order to produce a joint. High stresses can develop due to thermal expansion mismatch among materials involved. In the present technique, the relatively low process temperature can significantly reduce the stresses. The multilayer bonding method also facilitates control of the alloy composition and the joint thickness.
In-Plane Anisotropy In CoCr(Ta,Pt)/Cr Films Deposited onto Substrates with Controlled Topography
Authors: Twisselmann D.J. , Adekor B.T. , Farhoud M. , Smith Henry I. , Dorsey P.C. , Ross C.A. 
Published: April 2011

AbstractIn-plane magnetic anisotropy can be induced in Cr-underlayer/Co-alloy thin films by grooves or scratches in the substrate. To quantify this effect, silica substrates have been prepared with large areas of submicron grooves using interferometric lithography. The growth of Cr films and Cr/Co-alloy bilayer films on these substrates has been investigated, and in-plane magnetic anisotropy has been observed.
Compositional Microstructure and Micromagnetics of Co-Based Thin Film Media
Authors: Futamoto M. , Inaba N. , Hirayama Y. , Ito K. , Honda Y. 
Published: April 2011

AbstractElemental segregation of CoCrTa and CoCrPt thin films for longitudinal and perpendicular media is investigated using high spacial resolution transmission electron microscopes equipped with compositional analysis facilities. Strong Cr segregation exceeding 20 at% within 1.5-2 nm width is observed along the grain boundaries for both types of CoCrTa films prepared at elevated substrate temperatures. Weaker Cr segregation is observed along the grain boundaries of the longitudinal and the perpendicular CoCrPt films. The strong Cr segregation at grain boundaries is related with the small magnetic cluster size and the low media noise characteristics of CoCrTa thin film media. The Cr content inside the grain is several % lower than the average composition of the CoCrTa films. The magnetocrystalline anisotropy constants(Ku) for different Cr compositions are determined using single crystalline thin film technology to discuss the thermal stability of recorded information.
Effects of DC Bias on the Thermal Stability of DC In-Line Sputtered CoCrTa/Cr Thin Film Media
Authors: Wang J. P. , Tan L. P. , Liew T. Y. F. , Low T. S. , Wong H. L. , Lee Y. K. 
Published: April 2011

AbstractThe effects of DC bias on the thermal stability and magnetic anisotropy of CoCrTa/Cr thin film media fabricated by using a DC in-line sputtering machine is presented in this paper. In sputtering, a negative DC bias voltage, varying from 0 to 400 V, was applied for the CoCrTa layer. The coercivity was observed to increase almost linearly from 1800 to 2300 Oe for negative bias voltage from 0 to 400V. The thermal stability of these media was studied by measuring the time decay of remanent magnetization under various reverse magnetic fields. The maximum value of the magnetic viscosity coefficient, which happens around remanent coercivity of each samples, decreases with increasing substrate bias voltage. This implies an improvement in the thermal stability of the CoCrTa/Cr thin film media. The magnetic anisotropy constants were measured using both a torque magnetometer and a vibrating sample magnetometer. The magnetic anisotropy measured using torque magnetometer decreases, while that measured using the method of the law of approach to saturation was found to be almost constant, with increasing bias voltage. The activation volumes decreased with increasing bias voltage. The magnetic hardness coefficient determined using the law of approach to saturation, indicating the number of in-depth defects in the CoCrTa layer, increased with increasing bias voltage. The internal stress in these films measured using X-ray diffractometer also supported the existence of in-depth defects. The pinning of the rotation of magnetization by these defects in the magnetic grains maybe responsible for the improvement of thermal stability.
A Simulation of Rotational Hysteresis Energy Loss in Longitudinal Thin-Film Media
Authors: Yang Wei , Lambeth David N. 
Published: April 2011

AbstractThe field dependence of the rotational hysteresis energy loss was simulated for longitudinal thin-film media with the purpose of examining the validity of this method for measuring the anisotropy field. The field at which the rotational hysteresis vanishes, which is usually taken as the experimentally measured anisotropy field, was found to be smaller than the real anisotropy field when intergranular magnetostatic and exchange interactions are included in the simulations. Hence the rotational hysteresis method may result in an underestimation of the anisotropy field for the films with non-negligible grain interactions. To confirm this experimentally, two CoCrTa films, one with strong in-plane easy axis texture and the other with uniaxially aligned grain easy axes, were prepared under the same conditions. The anisotropy field determined by the rotational hysteresis of the first sample was found to be smaller than the more accurate value obtained from the hard axis hysteresis loop of the second sample.
Structural and Magnetic Properties of Co50 ± x Pt50 ± x Thin Films Prepared by Mbe Co-Evaporation on (001) MgO Substrate at Various Temperatures
Authors: Parasote V. , Cadevwlle M.-C. , Pierron-Bohnes V. , Grange W. 
Published: April 2011

AbstractStructural and magnetic properties of Co50 ± x Pt50± x films 25-50 nm thick, prepared by molecular beam epitaxy onto a Pt buffer grown on MgO (001) substrate have been investigated. A series of 3 samples with different compositions (x = 6, 0, -6) was grown at 800 K on a 10 nm thick Pt buffer and another series of 5 samples of equiatomic composition was prepared at various growth temperatures (390 K≤ TG≤ 780 K) on a Pt buffer 4 nm thick. X-ray diffraction and TEM studies show the presence of grains with [111] and [002] orientations, the [002] grains being a mixture of the tetragonal L10 ordered phase and of the fcc disordered one. Both the thickness of the buffer layer and the deposition temperature are determinant parameters of the structural quality of the films and of the degree of long range order (LRO). An apparent LRO parameter (ηapp) is deduced from the superstructure and main peak intensity ratio. Its increase with the growth temperature is described through a thermally activated model that yields a small activation energy of 0.28 eV, illustrating the role played by both surface diffusion and surface interactions in building the L10 compound in agreement with theoretical predictions. An average uniaxial magnetocrystalline anisotropy energy (Kuav) is deduced from the magnetization curves measured by a SQUID. The anisotropy energy of the [002] grains (Ku002) is deduced, assuming a linear relationship between the anisotropies and the phase percentages. One observes a continuous but not linear increase of Ku002 with ηapp.
Characterization of Thin DLC Films Using Film Stress and Raman Techniques
Authors: Turlo J. E. , Gan Danny , Gopinathan Niranjan 
Published: April 2011

AbstractDiamond like carbon (DLC) films are deposited on thin film heads in the magnetic recording industry to reduce friction and “stiction” and to provide a durable, abrasion resistant coating. The films are a mixture of graphitic phases with sp2 bonding and diamond phases with sp3 bonding. The present work provides the results of thin film stress measurements and Raman tests performed on 10 rim DLC films deposited on 75 mm silicon test wafers using standard optical lever techniques. Stress is measured after deposition and in-situ during thermal cycling. Isothermal relaxation data is also obtained. Raman is performed before and after annealing.The deposited stress of 10 nrm films was over 2000 MPa. The stress relaxed entirely to zero during thermal cycling to 500°C. Isothermal relaxation at 300°C also resulted in complete relaxation of an initial 1500 MPa stress to zero in less than 24 hours. The Raman data is consistent with prior results in the literature. The position of the G band shifts from 1513 to 1581 cm-1 during annealing, and the intensity ratio of the D band to the G band rises from 0.201 to 0.814 during annealing.The decrease of the film stress to zero during thermal processing implies that the entire thickness of the film is undergoing a structural change while the stress relaxation data implies that the stress is relaxing by a fast diffusive process. The Raman data implies that the film is becoming more graphitic and the crystallites are growing in number and size during thermal processing. We suggest that the structure of the extremely thin carbon film is modified by a surface diffusion mechanism.
Integrated Optical Isolator Employing Nonreciprocal Phase Shift by Wafer Direct Bonding
Authors: Yokoi H. , Mizumoto T. 
Published: April 2011

AbstractA novel configuration of an integrated optical isolator employing a nonreciprocal phase shift is proposed. The isolator is equipped with a cladding layer of magnetic garnets by means of wafer direct bonding technique. This device has a semiconductor guiding layer, so high compatibility in integrating with other semiconductor optical devices is expected.
Radiatively Coupled Waveguide Concept for an Integrated Magneto-Optic Circulator
Authors: Lohmeyer M. , Shamonin M. , Bahlmann N. , Hertel P. , Dotsch H. 
Published: April 2011

AbstractThree-guide couplers with multimode central waveguides allow for remote coupling between optical channels. A simple three mode approximation turns out to be sufficient for the description of the main features of the power transfer behavior. The specific form of the relevant modes suggests the design of integrated optical isolators and circulators based on magnetic garnet materials. These novel devices are superior to conventional nonreciprocal couplers with respect to the total length and admissible fabrication tolerances. We characterize the isolation performance and the transmission loss for the proposed devices by propagating mode simulations and estimate the influence of geometry parameter deviations.
The Precipitation of the Nanoparticles by the Thermophoresis at the Cryogenic Temperatures
Authors: Khasanov O.L. , Pokholkov Yu.P , Krivobokov V.P. , Milovanova T.V. 
Published: April 2011

ABSTRACTThe conditions of nanodispersed particles precipitation from a gas flow on the surface cooled to cryogenic temperatures are analyzed. The range of allowable values of precipitation surface temperature has been defined in dependence of dispersed flow characteristics. The method can be used both for catching of nanopowders, and for gas cleaning from aerosol and dust particles for ecological purposes.