Showing papers on "Silicon published in 1969"

The structure of vitreous silica

Abstract: A new study of the structure of vitreous silica has been made under greatly improved conditions. Using Rh Kα radiation with the method of fluorescence excitation, reliable intensity values were measured to 4π sinθ/λ = 20. The interpretation was in terms of pair functions, thereby eliminating the approximations in earlier work. Each silicon is tetrahedrally surrounded by 4 oxygen atoms, with a Si–O distance which is closely 1.62 A. Each oxygen atom is bonded to 2 silicon atoms. The Si–O–Si bond angle α shows a distribution V(α) extending all the way from 120° to 180°, with a maximum at α = 144°. This wide variation in α is an important distinction between the vitreous and the crystalline forms of silica, and it furnishes an important criterion for any proposed model of vitreous silica. Good agreement with the measured pair function distribution curve was obtained by assuming a random orientation about the Si–O bond directions. The interpretation leads to the familiar random network model, but with the new results the model is more precise.

Electromigration failure modes in aluminum metallization for semiconductor devices

Abstract: Two wear-out type failure modes involving aluminum metallization for semiconductor devices are described. Both modes involve mass transport by momentum exchange between conducting electrons and metal ions. The first failure mode is the formation of an electrically open circuit due to the condensation of vacancies in the aluminum to form voids. The second is the formation of etch pits into silicon by the dissolution of silicon into aluminum, and the transport of the solute ions down the aluminum conductor away from the silicon-aluminum interface by electron wind forces. The process continues until an etch pit grows into the silicon to a depth sufficient to short out an underlying junction.

Anisotropic Etching of Silicon

Abstract: A ternary liquid etchant solution for silicon, consisting of hydrazine, iso‐2‐propyl alcohol (IPA), and water has been studied in some detail. In common with other anisotropic etchants reported in the literature, marked dependence of dissolution rate on the crystal orientation of the etched surface has been observed with a low rate of attack on (111) planes. In contrast to other formulations, this etch attacks neither silicon dioxide nor aluminium vacuum‐deposited films, either of which may be used as a very convenient in‐contact masking medium for the engraving of intricate shapes on an appropriately oriented silicon substrate. The experimental study indicates that the etch velocity is a maximum for (211) planes, which accounts for the rounding of convex corners frequently observed when engraving regular shapes in silicon with anisotropic etches. The optimum etch solution is an equimolar mixture of NH2 and H2O.

Evidence of Voids Within the As-Deposited Structure of Glassy Silicon

Abstract: We present electron diffraction data from amorphous silicon which cannot be reconciled with the intensity profiles derived from small-crystallite models based on the diamond structure. Our diffraction patterns do reveal a pronounced low-angle scattering which anneals out on progressive heating and is indicative of actual void spaces, or regions of distinctly deficient density, in the films. These regions may be responsible for the recent observations of Brodsky and Title on surface states within the bulk of amorphous Si.

Charge Transport and Storage in Metal‐Nitride‐Oxide‐Silicon (MNOS) Structures

Abstract: A simple physical model that predicts charge accumulation at the dielectric interface of metal‐nitride‐oxide‐silicon (MNOS) structures is proposed and verified experimentally. The model is based on the presence of steady‐state current flow in the dielectric structure. Interface‐charge accumulation is shown to be determined by the requirement for continuity of current through the structure under steady‐state conditions. Continuity of current is established by accumulation of either positive or negative charge for a given polarity of charging voltage, depending on the relative current‐field characteristics of the silicon nitride and silicon dioxide layers. Due to the exponential nature of the current‐field characteristics, the time required to reach steady state is a strong function of the applied charging voltage. This leads to the observed charge storage property of MNOS devices. The hysteresis characteristic observed in MNOS structures is shown to be time‐dependent with a tendency to merge into a single‐...

Thermal Expansion of Silicon and Zinc Oxide (I)

Abstract: Coefficients of thermal expansion α‖c and α ⊥ c between 4 and 800°K have been measured for zinc oxide using an interferometric and a capacitance method. Thermal properties of wurtzite lattices (two coefficients of thermal expansion and a pyroelectric constant) can be described in terms of three thermal equations of state. Two mechanical and one electrical Gruneisen parameters are defined and their temperature dependence is calculated from experimental results. The high- and low-temperature limits of the Gruneisen parameters are compared with results obtained in other experiments. The values predicted from a rigid ion model are discussed.

Solid Solubility and Diffusion Coefficients of Boron in Silicon

Abstract: The solid solubility and diffusion coefficients of boron in silicon have been determined as a function of temperature over the range of 700°–1151°C, by anodically sectioning diffused layers. The solid solubility was found to vary from at 700°C to at 1151°C. The diffusion coefficients for impurity levels below 1018 atoms/cm3 may be represented by . The diffusion coefficients above 1018 atoms/cm3 were found to be dependent on the impurity level.

Implantation and Annealing Behavior of Group III and V Dopants in Silicon as Studied by the Channeling Technique

Abstract: The implantation and annealing behavior of several Group III (Ga, In, Tl) and Group V (As, Sb, Bi) dopants in silicon has been investigated by studying the orientation dependence of the scattering yield of a 1.0‐MeV He+ beam. This orientation dependence (``channeling'') provides quantitative information on the location of the foreign atoms in the lattice, and also on the amount of lattice disorder introduced by the implantation. The behavior of the Group V elements is relatively simple. In hot (350°–450°C) implants and also in annealed room‐temperature implants, the dopant atoms are located mostly on substitutional sites, even for implant doses exceeding equilibrium solubility values by 1–2 orders of magnitude. Upon subsequent anneal, no evidence of precipitation is observed below ∼900°C. The behavior of the Group III elements is much more complex. In addition to a substitutional component, a significant fraction of the implanted atoms are located in the regular interstitial holes along the (111) atomic rows. The substitutional/interstitial ratio in hot implants is usually 1:1, except in the case of Tl implants where, on annealing to ∼575°C, a pure interstitial component is observed. Furthermore, the subsequent annealing behavior is found to depend markedly not only on the particular Group III ion, but also on the implantation temperature. Various factors that may contribute to the Group III behavior are discussed. Preliminary ion implantation studies with other elements (Cd, Sn, Te, Xe, Cs, and Au) in silicon have been included.

AVALANCHE INJECTION CURRENTS AND CHARGING PHENOMENA IN THERMAL SiO2

Abstract: Injection of carriers into thermally grown SiO2 from an avalanche plasma in silicon is a new way of achieving high current densities in SiO2. Electron injection from p‐type silicon and hole injection from n‐type silicon by hot carrier emission have been observed. Average electron current densities as high as 10−2 A/cm2 have been observed to flow through 1000 A of SiO2. The oxide becomes negatively charged as a result of electron injection and positively charged as a result of hole injection. These charging effects appear to be related to the presence of water in the oxide.

Current gain and cutoff frequency falloff at high currents

Abstract: A theoretical and experimental study of the effects of high-level injection of carriers into a reverse-biased collector-base junction has been performed. Two models which describe the high-current behavior of the junction space-charge region are discussed. The first deals with the formation of a current-induced base region at space-charge-limited current densities. The second model assumes that two-dimensional effects are predominant; at current densities corresponding to the onset of space-charge-limited current, lateral injection of carriers takes place. These phenomena were studied experimentally using silicon double-diffused transistor structures. The existence of space-charge-limited current in the reverse-biased collector depletion layer manifests itself in significant changes in the ac and dc parameters of the transistor. In particular, it is shown that the cutoff frequency (f T ) and large-signal current gain (h FE ) begin to decrease rapidly with increasing current at the onset of the space-charge limitation. A comparison of experimental results with predictions of the above theories indicates that, while both the formation of a current-induced base region and lateral injection do take place, the latter mechanism controls conventional device performance.

Electrical Behavior of Group III and V Implanted Dopants in Silicon

Abstract: The anneal behavior of layers implanted with dopants from column III (B, Al, Ga, and Tl) and column V (As, Sb, and Bi) in silicon substrates has been investigated. The ranges of implant conditions were energy 20–50 keV, dose 1013–1015/cm2, and substrate temperature 23°–500°C. Hall‐effect and sheet resistivity measurements were used to determine the effective number of carriers/cm2 (Ns)eff and the effective mobility μeff. Analysis of nonuniform distributions of carrier densities and mobilities on these measurements shows that the values of (Ns)eff and μeff can be misleading unless the effect of the depth distributions is allowed for. These distributions have been determined in some cases by the use of layer removal techniques combined with Hall‐effect and sheet resistivity measurements. We find in well‐annealed implanted samples that the dependence of the mobility on carrier density follows that determined for bulk silicon. In many cases deviation from this relation can be accounted for on the basis of com...

Divalent Silicon Intermediates

Abstract: Like carbenes, silylenes are assumed to occur as intermediates in many reactions. A detailed account of the reactivity of the silylenes is given and the reductive and thermolytic methods used for their preparation are discussed. Insertion and interception reactions emphasize the formal relationship between these species and the carbenes. Silacyclopropenes and silacyclopropanes have not, as yet, been isolated.

Bi-layer insulation structure including polycrystalline semiconductor material for integrated circuit isolation

Abstract: THIS SPECIFICATION DISCLOSES A METHOD OF FABRICATING AN INTEGRATED CIRCUIT CHARACTERIZED BY ELECTRONIC COMPONENTS BEING FORMED IN A POLYCRYSTALLINE SEMICONDUCTOR, SUCH AS SILICON OR GERMANIUM, DEPOSITED AT LESS THAN 900*C. AND AT A RATE OF LESS THAN ONE MICRON PER MINUTE AND OVERLYING AN ISOLATION LAYER COVERING COMPONENTS FORMED IN A BASE REGION OF MONOCRYSTALLINE SEMICONDUCTOR MATERIAL. THE COMPONENTS IN THE POLYCRYSTALLINE SEMICONDUCTOR MAY EMPLOY JUNCTIONS AND MAY BE ACTIVE OR PASSIVE. MORE THAN ONE LAYER OF POLYCRYUSTALLINE SEMICONDUCTOR AND MORE THAN ONE ISOLATION LAYER MAY BE EMPLOYED.

Minority Carrier Recombination in Neutron Irradiated Silicon

Abstract: Measurements are reported which provide extensive data on the resistivity, temperature, and injection level dependences of the minority carrier lifetime in neutron irradiated p- and n-type silicon. The lifetime damage constants are observed to be quite dependent on the injected minority carrier density, in both conductivity types, over the temperature range from 76°K to 300°K. The low injection level damage constants have been measured and found to be dependent on material resistivity in p-type silicon, but only slightly dependent on resistivity in n-type silicon. The results of the experimental studies are compared to the predictions of two alternate models for recombination at defect clusters. For defect clusters of approximately 250 A radius, as expected from range calculations, these comparisons indicate that each contains a relatively small number of deep defects (30 - 40). The defects are individually characterized by a deep donor level near Ev + 0.35 eV and a deep acceptor level near Ec - 0.50 eV. Since these levels correspond approximately to the known energy levels of the silicon divacancy, it is suggested that the divacancy may be the active recombination center within the defect clusters.

Atomically Clean Surfaces by Pulsed Laser Bombardment

Abstract: It is shown that high power, Q‐spoiled lasers offer an interesting method for obtaining clean surfaces in vacuum. However, complete removal of oxygen and sulfur contamination from nickel surfaces by laser bombardment at 100 MW/cm2 produced irreparable surface damage that is attributed to filamentizing of the laser beam and/or to nonuniform surface reflectivity. On the other hand, application of the technique at 30 MW/cm2 successfully removed the (7×7) satellite structure from (111) silicon surfaces without surface damage.

Bipolar and field-effect transistor using polycrystalline epitaxial deposited silicon

Abstract: Adjacent layers of single crystalline and polycrystalline semiconductor material are located upon a semiconductor substrate. The single crystalline layer provides for the active regions of a semiconductor device while the adjacent polycrystalline layers provide for lateral contacts to the active regions.

Arsenic Isoconcentration Diffusion Studies in Silicon

Abstract: Arsenic radiotracer diffusions have been performed both in intrinsic and in homogeneously doped extrinsic silicon single crystals. Under intrinsic conditions, the tracer diffusion coefficient may be represented by the expression Di=60 exp (−4.20 eV/kT) cm2/sec. Measured in extrinsic silicon, in the absence of a concentration gradient, the tracer diffusion coefficient conforms with the relationship D=Di(n/ni), in which (n/ni) in the ratio of the free electron concentration in the extrinsic sample to that of intrinsic silicon at the diffusion temperature.

Calculations of ionization equilibria for oxygen, neon, silicon, and iron.

Abstract: O, Ne, Si and Fe ionization equilibria in low density plasma, including dielectronic recombination and autoionization processes in calculations

The thermal conductivity of sintered semiconductor alloys

Abstract: The thermal conductivity of sintered semiconductor alloys is calculated using the Klemens-Callaway model assuming that the boundary scattering can be adequately described by a mean free path. It is shown that the relative increase in thermal resistance increases with the amount of alloy disorder scattering and should be substantial in sintered germanium silicon alloys with particle sizes of the order of one micron.

X‐Ray Investigation of Lattice Deformations in Silicon Induced through High‐Energy Ion Implantation

Abstract: X-ray interference fringes observed in X-ray topographs of silicon crystals bombarded with high energy ions (dose > 1015 ions/cm2) are described. The X-ray fringes are used to analyze the deformation state of the crystal. It is shown that the bombarded crystal is a special kind of bicrystal composed of a thick perfect bulk crystal topped by a thin practically perfect layer crystal. Both crystals have the same crystallographic orientation and the same lattice constant but are separated by a small rigid body displacement. Contrast and geometry of the observed X-ray patterns agree with the theoretical patterns calculated by Bonse and Hart [1] on the basis of a layer/bulk bicrystal model, and are also supported through transmission electron microscopy results. The ion range calculated from the interference fringes is in good agreement with the experimentally determined range. Rontgeninterferenzen, beobachtet in Rontgentopogrammen von Siliziumkristallen, die mit monoenergetischen Ionen (Dosis > 1015 Ionen/cm2) beschossen wurden, werden beschrieben. Mit Hilfe der Interferenzstreifen wird der Deformationszustand des Kristalls analysiert. Es wird gezeigt, das der bombardierte Kristall einen Doppelkristall darstellt, der aus einem dicken und einem dunnen Teil besteht. Beide Kristalle haben dieselbe kristallographische Orientierung und dieselbe Gitterkonstante, sind aber gegeneinander als starre Korper verschoben. Der Kontrast und die Geometrie der beobachteten Interferenzstreifen ist mit den von Bonse und Hart [1] auf Grund des Doppelkristallmodells berechneten Interferenzmustern in guter Ubereinstimmung. Die experimentellen und theoretischen Ergebnisse sind auch mit den Ergebnissen der Elektronenmikroskopie in Ubereinstimmung. Die Eindringtiefe der Ionen kann mit Hilfe der Interferenzstreifen berechnet werden und stimmt mit den experimentellen Ergebnissen uberein.

Multielement self-scanned mosaic sensors

Abstract: Self-scanned image sensors are making possible new types of television cameras and imaging devices based entirely upon solid-state components. Research on integrated image sensors has followed two experimental approaches: monolithic silicon and thin-film photoconductors. This article reviews the operation of the most common types of self-scanned sensors, indicating their relative advantages and disadvantages. Two new developments are a 256 × 256 element photoconductive sensor with integrated thin-film scanning decoders and a novel silicon photodiode sensor that may permit considerable reduction in element spacings.

The Interactions of Point Defects with Impurities in Silicon

Abstract: The minority carrier lifetime in gamma-irradiated silicon crystals was studied. In F. Z. n type crystals containing phosphorous, arsenic, antimony or bismuth, there are two annealing stages in the temperature range 100–280°C and in both stages there is strong dependency of activation energies E a and frequency factors on the atomic size of the impurity. The relationship between E a and covalent radii of the impurity atom can be experimentally expressed in linear functions. The defect which anneals in the lower temperature stage is a complex of donor atoms associated with a vacancy type defect. Si-E center anneals in the higher temperature stage and the values of activation energies completely agree with those obtained by Watkins et al. in their experiments of reorientation of donor-vacancy axis. The defects of both stages are considered to migrate to the sinks of oxygen after jumps of about 10 5 . It is very interesting to note that this study shows only one example of an impurity atom which moves with a ...