Showing papers on "Annealing (metallurgy) published in 1982"

Conductivity behavior in polycrystalline semiconductor thin film transistors

Abstract: CdSe thin film transistor (TFT) structures which have been ion implanted with 50 keV 52Cr, 50 keV 27Al, or 15 keV 11B have a very steeply rising conductivity above some threshold dose and exhibit modulated transistor characteristics over certain ranges of implant dose, even though there is no thermal annealing during or after ion implantation. These results are interpreted using a model based on grain boundary trapping theory. The dependence of leakage current on implant dose, and of drain current (at a fixed dose) on gate voltage are described very well by this model, when the drain voltage is very small. Using this simple model, the important parameters of the polycrystalline CdSe film, namely the trap density per unit area in the grain boundary, the donor density, grain size, and electron mobility can be deduced. The effect of thermal annealing on implanted and unimplanted CdSe TFT’s has also been studied and the model appears to give a general description of the conductivity behavior in polycrystallin...

Effects of annealing and prior history on enthalpy relaxation in glassy polymers. 2. Mathematical modeling

Abstract: A simple four-parameter model reproduces DSC data on the effects of annealing conditions, and thermal history before annealing, on the heat capacity of glassy polymers. The model is an application of the successful treatment of glass transition kinetics, due to Moynihan and co-workers, to thermal histories which include annealing. It is found that a nonexponential relaxation function is essential for the development of sub-T, heat capacity peaks with annealing and that nonlinearity is important in accelerating their development to experimentally accessible aging times. Numerical integration allows accurate predictions of the effects of quench rate, annealing temperature, annealing time, and reheating rate on the magnitude and temperature of heat capacity peaks observed in DSC scans of annealed PVC (part 1) and other polymeric glasses.

Magnetomechanical properties of amorphous metals

Abstract: Amorphous metals have magnetomechanical properties superior to those of crystalline magnetostrictive materials, and are therefore being considered for a variety of transducer and sensor applications. A simplified model is presented of magnetomechanical coupling in amorphous metal ribbons, showing the relation between magnetomechanical behavior and fundamental material parameters. Although high values of magnetization and magnetostriction are important, it is primarily the low values of magnetic anisotropy achievable that give amorphous metals their outstanding magnetomechanical coupling. The magnitude and homogeneity of this anisotropy is controllable through choice of alloy composition and annealing conditions. Amorphe Metalle haben bessere magnetomechanische Eigenschaften als kristalline Werkstoffe, und werden deshalb fur Anwendungen als Energieumwandler und Kraftubertrager betrachtet. Ein vereinfachtes Modell der magnetomechanischen Kopplung in amorphen metallischen Bandern wird gegeben, das die Beziehung zwischen magnetomechanischem Verhalten und grundlegenden Parametern des Werkstoffes erkart. Obwohl hohe Werte der Magnetisierung und Magnetostriktion wichtig sind, stammen die hervorragenden magnetomechanischen Kopplungseigenschaften in amorphen Metallen hauptsachlich von den niedrigen Werten der magnetischen Anisotropie. Die Werte und die Homogenitat der Anisotropie werden durch die Legierungszusammensetzung und die Anlasbedingungen kontrolliert.

Temperature profiles induced by a scanning cw laser beam

Abstract: We present calculations of the temperature profiles induced by a moving cw elliptical laser beam with a Gaussian intensity distribution in a semi‐infinite material. Temperature‐dependent thermal diffusivity, conductivity, and surface reflectivity are incorporated in our model, and some aspects of melting are discussed. As an example, we apply the calculations to silicon. For a comparison of stationary elliptical spots of varying eccentricities, we present material‐independent normalized linear temperature profiles. We find that highly elliptical beams can be used to rapidly scan and anneal large areas.

Theory of the peroxy-radical defect in a -Si O 2

Abstract: We have investigated the peroxy-radical defect in glassy Si${\mathrm{O}}_{2}$ by means of MOPN, a semiempirical molecular-orbital program, applied to a cluster of atoms chosen to simulate the defect. Our calculations are consistent with important features of Griscom's model of the defect as a perturbed ${\mathrm{O}}_{2}^{\ensuremath{-}}$ ion substituted for a single-bridging ${\mathrm{O}}^{2\ensuremath{-}}$ ion in Si${\mathrm{O}}_{2}$ and attached to a single silicon, and they place geometrical constraints on the defect structure for this model to be valid. We predict the existence of a related defect (the small peroxy radical, or SPR) wherein the peroxy radical is strongly bonded to two silicons. We have also investigated the formation of the peroxy radical. Griscom and co-workers envision peroxy linkages substituting for single-bridging oxygens during the growth process. They suggest that upon annealing these linkages readily give up an electron to form the observed radical. Our calculations lead us to argue against this process; rather, capture of a free hole seems more likely. We suggest that the SPR could form via a process in which neutral oxygen molecules diffuse through the solid and combine with ${E}_{1}^{\ensuremath{'}}$ centers to form peroxy radicals.

TiN formed by evaporation as a diffusion barrier between Al and Si

Abstract: The formation of TiN thin films by doping Ti with N2 during evaporation at room temperature and by following with high‐temperature (700–900 °C) annealing was confirmed by x‐ray analysis This is different from conventional reactive sputtering and is compatible with lift‐off processes in pattern delineation It has been observed that when Ti is heavily doped with N on a silicon substrate, the reaction between Ti and Si which forms TiSi2 is totally suppressed during high‐temperature annealing and forms TiN only On the other hand, if a thin layer of pure Ti was evaporated on a Si substrate before the introduction of N2, then a composite film of TiN/TiSi2 was formed with a clear boundary between them after high‐temperature annealing The thickness of each layer can be well controlled by the initial evaporation thickness In both cases, Al was deposited on top Rutherford backscattering studies showed that TiN is an effective diffusion barrier up to 550 °C for 30 min of annealing and forms an ideal contact barrier between Al and Si

Synchrotron x-ray diffraction study of silicon during pulsed laser annealing

Abstract: Time-resolved x-ray diffraction measurements of lattice strain in silicon during pulsed-laser annealing have been made with nanosecond resolution by using synchrotron radiation. Analyses of the strain in pure and boron-implanted silicon in terms of temperature indicate high temperatures and evidence for near-surface melting, in qualitative agreement with the melting model of laser annealing.

Precipitation as the phenomenon responsible for the electrically inactive phosphorus in silicon

Abstract: The physical nature of the electrically inactive phosphorus in silicon was investigated by annealing experiments performed on laser annealed specimens doped by ion implantation up to 5×1021 at/cm3. The hypothesis of point defects, which compensate or make the excess dopant electrically inactive, is contradicted by the experimental results. It was verified that phosphorus solubility corresponds to the electrically active concentration in equilibrium with the inactive dopant, and that the latter is precipitated phase. This was confirmed by transmission electron microscopy (TEM) examinations with the weak beam technique, which detected a high density of very small coherent precipitates. This method allowed us to observe particles of the same kind even on specimens thermally predeposited in conditions typical of device technology. In both cases the amount of precipitates was consistent with the inactive dopant concentration. In addition these experiments show that precipitation is associated with a high enhan...

Interstitial iron and iron-acceptor pairs in silicon

Abstract: Deep levels in iron-dopedp-type silicon are investigated by means of Deep Level Transient Spectroscopy (DLTS) and the Hall effect. Pairs of Fe with the acceptors B, Al, and Ga are observed at 0.1, 0.19, and 0.24 eV above the valence band edgeEv. For interstitial iron, (Fei), a level energy ofEv+0.39+-0.02 eV is obtained with DLTS after correction with a measured temperature dependence of the capture cross section. The Hall effect yieldsEv+0.37 eV for Fei. The annealing behavior of levels related to Fe is investigated up to 160 °C. Iron participates in at least four different types of impurity states: Fei, Fe-acceptor pairs, precipitations (formed above 120 °C) and an additional electrically inactive state, which is formed at room temperature.

Structure–property relationships in dual-phase steels

Abstract: A study has been made of the formation of the dual-phase structure in intercritically annealed steels. The effects of annealing temperature, time, and cooling rate on the formation of the M–A (martensite and/or retained austenite) constituent have been described, and a discussion given of the factors affecting its development. It has been shown that nitrogen refines the M–A constituent particle size, and possible reasons for this have been discussed. The flow stresses and work-hardening rates have been analysed in terms of established dispersion-strengthening models, with excellent agreement between the theoretical predictions and the experimental results. Both the flow stress and work-hardening rate increase with increasing volume fraction and decreasing particle size of the M–A constituent, but particle size has more effect on the work-hardening rate than on the flow stress. Hence a fine particle size is required to optimize the formability. On the basis of the results obtained, the optimum micr...

Characterization of damage in ion implanted Ge

Abstract: It has been observed that ion implantation into Ge at room temperature creates severe surface craters extending several thousand angstroms into the surface, and results in the incorporation of large quantities of C and O impurities (∼50 impurities/ion). This effect has a strong temperature dependence and essentially disappears for implantations performed at liquid nitrogen temperature. The systematics of this effect are presented, preliminary annealing results are cited, and possible mechanisms are discussed.

Use of selective annealing for growing very large grain silicon on insulator films

Abstract: The selective annealing technique (laser annealing under a patterned antireflecting coating) has been successfully applied to the growth of very large (20×400 μm) silicon single crystals on SiO2. The grain boundary location is controlled by a conventional lithography step, and the grains obtained have a nearly perfect rectangular shape.

Diffusion of arsenic in polycrystalline silicon

Abstract: The diffusion of arsenic in polycrystalline silicon films has been studied over the temperature range 750–950 °C and for grain sizes 210–510 nm. Rutherford backscattering spectrometry was used to measure the concentration profiles of arsenic, initially introduced into the polysilicon by ion implantation, after various annealing steps. The concentration profiles were found to be determined by a combination of two factors—the low diffusivity in the bulk of the rains and the much higher diffusivity in the grain boundaries. The diffusivity of arsenic in the grain boundaries was independent of concentration, with an activation energy of 3.9 eV, very close to that of the low‐concentration arsenic diffusivity in single‐crystal silicon. However, the value of the diffusivity was 8.6×104 exp(−3.9/kT)cm2/s, four orders of magnitude higher than the single‐crystal value. The diffusivity in the interior of the grains was the same as that in single‐crystal silicon.

Effects of annealing on the electrical properties of CdxHg1−xTe

Abstract: CdxHg1−xTe with 0.17

Defects and impurities in thermal oxides on silicon

Abstract: Oxides grown at 1100 °C in dry oxygen for 60 min to a thickness of 1350 A on silicon with and without subsequent forming gas anneals were 60Co γ irradiated at 4 K with doses up to 106 rad (Si). In situ electron paramagnetic resonance measurements at 10 K revealed ≊3×1017 atomic hydrogen/cm3 and ∼1017 oxygen‐hole centers/cm3 in the oxide. The paramagnetic dangling bond on the silicon side of the Si/SiO2 interface (Pb center) was also observed. The (relative) concentration of these centers was measured as a function of isochronal annealing between 10 and 300 K.

Effects of thermal annealing on the refractive index of amorphous silicon produced by ion implantation

Abstract: Precise infrared reflection measurements of the refractive index of silicon show that there are two well‐defined optical states of amorphous silicon produced by ion implantation One is the as‐implanted amorphous state which is the high refractive index state produced by high fluence implantation of Si or P ions into Si samples The other state, which has a refractive index intermediate between the as‐implanted and crystalline values, is induced by thermal annealing and is thermally stable until epitaxial recrystallization occurs

Deep radiative levels in InP

Abstract: Results of a detailed photoluminescence study of deep radiative transitions in InP crystals prepared by the bulk and epitaxial techniques are reported. In order to understand the origin of the photoluminescence (PL) spectra, bulk samples were subjected to isothermal anneals at different partial pressures of phosphorus. Similarly, the liquid phase epitaxy (LPE) wafers were grown with and without phosphorus in the gas stream. The electrical nature of some of the species responsible for the PL emission was inferred by a study of Cd diffused bulk samples. Based on these experiments the following tentative assignments are proposed. The photoluminescence band at 0.99 eV, common to all samples, is due to emission from a donorlike level related to the P vacancy. Bands at 1.21 and 1.14 eV appear to be due to emission to native acceptor levels associated with the In vacancy. The 1.08‐eV band is attributed to emission to a complex of the donor (0.99 eV) and acceptor (1.21 eV) species. The relationship between these bands and residual impurities is discussed.

Modeling of cw laser annealing of multilayer structures

Abstract: Careful computer modeling can accurately represent the temperature distribution created during laser annealing. In this way a better understanding of the physical processes that contribute to thin film crystallization is achieved, and precise predictions of the effects of various sample geometries on laser annealing are possible. Models of cw laser annealing have always assumed a single homogeneous medium, but practical structures usually consist of several layers of semiconductors, insulators and metals of widely varying thermal and optical properties. This treatment can model an arbitrary number of layers of various thicknesses, each with its characteristic thermal and optical properties. The problem is solved under steady state conditions without phase transitions. A general analytic expression cannot be obtained, but a simple procedure is presented for obtaining the temperature distribution in a given system. Explicit integral expressions are developed for the cases of two and three layers; numerical results are calculated for the Si/glass and Si/SiO2/Si systems.

Sputtering of amorphous Co‐Zr and Co‐Hf films with soft magnetic properties

Abstract: Amorphous Co‐Zr and Co‐Hf films produced by sputtering have been investigated. The fundamental magnetic properties, sputtering conditions for the soft magnetic properties, and annealing to obtain high permeability films have been studied. The saturation magnetization, magnetostriction of the sputtered films, and range of composition of amorphous phase have been determined. Sensitive dependence of the soft magnetic properties on Ar gas pressure has been found. Sputtering in low Ar gas pressure suppresses the formation of microcrystals in the amorphous matrix and columnar structure in the films which deteriorates the soft magnetic properties. High permeability films have been obtained by annealing and their thermal stability was studied.

Novel low‐temperature recrystallization of amorphous silicon by high‐energy ion beam

Abstract: An entirely new beam annealing method that employs a high‐energy (∼2.5 MeV) heavy ion (As75, Kr84) beam is presented. With this technology, an amorphous Si layer is recrystallized at below ∼300 °C substrate temperature (much lower than the ordinary solid phase epitaxial growth temperature of ∼600 °C). The temperature just under the beam spot is estimated to be at most ∼20° C higher than that in the surrounding region, because of the large beam spot size (∼10 mmφ) and rapid scan speed (∼104 cm/s). This low‐temperature annealing feature is quite different from the case for conventional furnace, laser, electron, and low‐energy ion beam annealing. After recrystallization, impurity As atoms are located at substitutional sites with no tetrahedral interstitial components, and are scarcely redistributed.

Substitutional solid solubility limits during solid phase epitaxy of ion implanted (100) silicon

Abstract: High resolution channeling techniques have been used to investigate the maximum nonequilibrium solid solubility which can be achieved during low‐temperature (⩽600 °C) epitaxial regrowth of high‐dose antimony and indium implanted (100) silicon. The substitutional impurity concentration is observed to increase with implant dose and saturate at a limiting concentration well above the maximum equilibrium solid solubility for antimony or indium in silicon. Observed correlations between the measured solubility limits, epitaxial regrowth rates, and intriguing impurity redistribution effects suggest that impurity size and attendant lattice strain at the crystal‐amorphous interface may determine the substitutional solubility limit for low‐temperature annealing, where impurity diffusion lengths are negligible during the time of epitaxial recrystallization.