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Journal of Applied Physics

Issue 9 • Date Nov 1996

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Displaying Results 1 - 25 of 116
  • Issue Table of Contents

    Page(s): toc1
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    Freely Available from IEEE
  • Scattering of evanescent light by a finite‐size probe in near‐field scanning optical microscopy

    Page(s): 4799 - 4803
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    Scattering of the evanescent light by a finite‐size SiO2 probe is calculated using a point matching method in order to improve the efficiency collecting the near‐field optical signal. The scattered‐light patterns can be classified into three categories. Category 1 is where the probe tip radius is very small (≪λ/13). Category 3 is where the probe radius is very large (≳λ/6). Category 2 is the intermediate case (λ/13≪radius≪λ/6). When the radius is in category 1, the scattered light is able to be treated as a field radiated by the point dipole induced by the evanescent light at the probe tip. When the tip radius is in category 2 (λ/13≪radius≪λ/6), in order to obtain the angular distribution of the scattered light, the induced multipoles should be calculated, considering the probe radius and the incident angle. When the tip radius is in category 3 (radius ≳λ/6), the scattered light becomes larger in the parallel direction to a prism surface due to the forward scattering of the evanescent light. © 1996 American Institute of Physics. View full abstract»

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  • Melt‐drawn scanning near‐field optical microscopy probe profiles

    Page(s): 4804 - 4812
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    Consistently obtaining super‐resolution with scanning near‐field optical microscopy depends almost entirely on the ability to manufacture reproducibly probes with aperture sizes smaller than 100 nm. The probe fabrication process usually involves heating an optical fiber using a CO2 laser and melt‐drawing the glass to produce a taper. A number of variables ultimately define the taper shape but the actual effects these parameters have are still not clear. In this work, the physics behind the taper formation is examined in detail for the first time and equations describing the initial taper profile and the final aperture size are derived in terms of the experimental conditions. It is shown that the taper shape is primarily determined by the laser spot size. The pulling force, although important, has a lower significance. Continuum mechanics and Stefan’s law are used to show that the aperture size is closely related to the radius of the fiber at the start of the hard pull and the fiber temperature at that time. Further comparisons of experimental data with the expected taper profile exposes the heating effect of the CO2 laser. Further analysis is given using a form of Mie theory which describes the interaction of electromagnetic fields with cylindrical structures. These results give many significant insights into the fabrication process and the formation of the aperture. © 1996 American Institute of Physics. View full abstract»

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  • Diagnosis of high‐brightness ion beams produced in point pinch diodes

    Page(s): 4813 - 4818
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    Diagnosis and evaluation have been carried out of the ion beam and anode plasma produced in a ‘‘point pinch diode.’’ From the measurement of a highly resolved Thomson‐parabola mass spectrometer, the ions accelerated in the diode gap contain (a) protons, (b) highly ionized carbon and oxygen ions, and (c) singly ionized medium mass ions such as carbon, oxygen, CO+2, OH+, H2O+. Time‐integrated x‐ray and particle pinhole images show the spot size of the electron beam on the plasma to be less than 0.5 mm in diameter, in which fine structures are found with size less than 0.1 mm. A Kα satellite line of Al V is observed with a crystal spectrograph, which indicates the existence of Al4+ in the plasma. © 1996 American Institute of Physics. View full abstract»

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  • The frequency spectrum of a phase‐modulated interferometer illuminated by a Gaussian source

    Page(s): 4819 - 4830
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    A detailed theoretical analysis with numerical calculations was conducted to study the frequency spectrum resulting from the application of a sinusoidal phase modulation to a two‐beam interferometer illuminated by a low‐coherence source with a Gaussian spectral profile. Results of these calculations show behavior of the frequency components which was unexpected from earlier derivations of the frequency spectrum. The results of the calculations have been experimentally confirmed using an all‐fiber interferometer illuminated by a source with a Gaussian spectral profile. The results will be useful for the signal processing of tandem interferometers for ‘‘white light’’ interferometry in the field of optical sensing. © 1996 American Institute of Physics. View full abstract»

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  • Properties of a submicrometer x‐ray beam at the exit of a waveguide

    Page(s): 4831 - 4836
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    This report discusses the properties of a 13‐keV submicrometer x‐ray beam exiting from a waveguide. Waveguides for this spectral regime can be constructed by enclosing a low‐absorbing material between highly absorbant metals. Best performance is found for about 0.1 μm guiding layer thickness. Measurements of the photon beam size close to the exit and of the intensity distribution far from the exit will be presented. From these data one derives a beam size at the exit which is identical to the guiding layer thickness. This number being in the submicrometer range offers interesting perspectives for microscopy experiments in the hard x‐ray range. © 1996 American Institute of Physics. View full abstract»

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  • Effects of current spreading under oxide current aperture in vertical‐cavity surface‐emitting lasers

    Page(s): 4837 - 4840
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    We discuss a buried oxide layer forming a current aperture in a vertical‐cavity surface‐emitting laser. The current spreading under the oxide current aperture leads to high threshold and dual‐longitudinal‐wavelength characteristics. One is the as‐grown cavity resonance and the other is the resonance wavelength under the oxide layer. This structure exhibits ≳30 dB side‐mode suppression throughout its operating range. Meanwhile, a single‐longitudinal‐wavelength laser with a minimized current spreading has a low threshold current of 85 μA and several nonlasing modes. © 1996 American Institute of Physics. View full abstract»

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  • Precisely tuned emission from porous silicon vertical optical cavity in the visible region

    Page(s): 4841 - 4844
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    The operating peak energy of a porous silicon (PS) cavity can be completely controlled over a wide range of 1.5–2.2 eV, using a PS‐based Fabry–Perot resonator composed of a light‐emitting active PS layer and two high‐reflectivity mirrors. When the PS devices are excited by a uv laser, quite narrow spectra (10–40 meV in full width at half‐maximum) are observed without any significant signs of side mode. The central photon energy is precisely and continuously tuned simply by changing the anodization parameters. The key issues of the controlled device operation are adjustment of the optical thickness of the active PS layer to an appropriate value and fabrication of the quarter‐wavelength multilayered PS mirror with a high reflectivity. The spectral qualities of the emitted light are also discussed by theoretical analyses on the basis of a simplified model. These results suggest that the PS devices operate as sharp band‐pass optical filter and the PS materials are available for novel silicon‐based microphotonics. © 1996 American Institute of Physics. View full abstract»

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  • The fluorescence of Nd3+ in lead borate and bismuth borate glasses with large stimulated emission cross section

    Page(s): 4845 - 4853
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    The stimulated emission cross section σp for the 1060 nm transition of Nd3+ in lead borate and bismuth borate glasses has been determined from fluorescence measurements. The compositional dependence of σp, which has been evaluated using radiative transition probability, refractive index of the host glass, effective fluorescence linewidth, and position of the band, with PbO/Bi2O3 content is investigated. The σp values of the 1060 nm band of Nd3+ for lead borate and bismuth borate glasses are found to be in the range 2.6–5.7×10-20 cm2 at 298 K and 3.0–6.3×10-20 cm2 at 4.2 K. The σp values are comparatively large suggesting the possible utilization of these materials in laser applications. © 1996 American Institute of Physics. View full abstract»

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  • Influence of free carrier concentration on absorption and third‐order susceptibilities of n‐type ZnSe crystals

    Page(s): 4854 - 4858
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    This study analyzes the dependence of third‐order susceptibilities at 532 nm of n‐type ZnSe crystals in relation to free carrier concentration and annealing temperatures. The nonlinear optical absorption and the efficiency of degenerate four‐wave mixing of ZnSe are investigated. We find that the magnitude of the nonlinear absorption decreases with the electron concentration and annealing temperature increase, while the nonlinear refractive index increases slightly. © 1996 American Institute of Physics. View full abstract»

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  • Applications of the second‐order Bragg interaction in a thin‐film optical waveguide for the transverse electric mode

    Page(s): 4859 - 4866
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    The operation of output coupler, input coupler, surface emitting amplifier, and surface emitting distributed feedback laser formed on a thin‐film dielectric waveguide depends on guided–guided and guided–radiated wave couplings. The characteristics of these devices are treated for the transverse electric mode for wave interactions caused by a suitable relief grating formed on the film–cover interface. Design criteria are deduced and optimization procedures are indicated with illustrative numerical examples. The device characteristics are insensitive to small changes in the physical parameters. Surface emitting amplifier with a uniform near‐field pattern and surface emitting distributed feedback laser operating in a single mode are investigated. © 1996 American Institute of Physics. View full abstract»

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  • Surface acoustic waves on the (11n) cuts of gallium arsenide

    Page(s): 4867 - 4871
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    Surface acoustic waves (SAW) propagating on the (111), (112), and (113) cuts of gallium arsenide in the [11¯0] direction are studied both theoretically and experimentally. The possibility of propagation of both normal and leaky surface acoustic waves (NSAW and LSAW, respectively) is predicted. The acoustoelectrical activity predicted for LSAW is more than 100 times higher than that for NSAW. Three particle displacement components of comparable magnitudes for LSAW propagating on the three cuts are obtained. The lowest attenuation (4.94×10-5 dB per wavelength) is predicted for the LSAW at the (112), [11¯0] orientation of GaAs. Theoretical characteristics for the LSAW on the (112) cut are corroborated experimentally. Experimental values of the phase velocity (3.05×103 m/s), electromechanical coupling coefficient (8.1×10-4), attenuation (5.7×10-3 dB per wavelength), and temperature delay coefficient (5.2×10-5 deg-1) are presented. Characteristics of experimental delay lines fabricated on the (112) cut and the well‐known (001) cut are compared. © 1996 American Institute of Physics. View full abstract»

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  • A nonendoreversible model for wind energy as a solar‐driven heat engine

    Page(s): 4872 - 4876
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    We study the Gordon and Zarmi model [Am. J. Phys. 57, 995 (1989)] for dealing with the earth’s wind energy as a solar‐driven endoreversible heat engine under a nonendoreversible approach. We take into account the departure from an endoreversible regime through a parameter arising from the Clausius inequality. We use this approach for the Gordon–Zarmi maximum power criterion with two possible cold reservoirs: the 3 K surrounding universe and the 200 K isothermal tropopause shell. Our numerical results for the average extreme temperatures of the earth’s atmosphere and for the annual average energy of the earth’s winds are reasonable. We also use an ecological optimization criterion for the Gordon–Zarmi model. This criterion consists of an austere compromise between power and entropy production. With this model, we also obtain reasonable numerical results for extreme temperatures and the wind’s power. © 1996 American Institute of Physics. View full abstract»

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  • Destruction of carbon tetrachloride in a dielectric barrier/packed‐bed corona reactor

    Page(s): 4877 - 4886
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    The destruction of low concentrations (≪1000 ppm) of gas‐phase carbon tetrachloride (CCl4) using a low‐temperature, dielectric barrier/packed‐bed corona reactor was studied. We compare, in particular, the destruction efficiencies using either borosilicate or zirconia oxide (ZrO2) packing materials in dry and moist air, and nitrogen buffer gases. Measurements of contaminant removal in the effluent gas were made at atmospheric pressure as a function of energy dissipated in the reactor. In dry N2, destruction of CCl4 was most efficient using ZrO2 beads, whereas, in dry air, contaminant removal was approximately equal for borosilicate glass and ZrO2. The presence of water in the gas stream reduced the CCl4 destruction efficiency under all conditions. This reduction was likely a synergistic effect that involves changes in the plasma density, scavenging of low energy secondary electrons, and possible surface passivation. Assuming the primary step in CCl4 destruction is dissociative electron attachment, an estimate of the average density of low energy electrons as a function of input energy was made. We relate the enhancement in CCl4 destruction using the ZrO2 beads in N2 to a slight increase in the number density of low energy secondary electrons. A discussion of the importance of energy density measurements and a useful phenomenological kinetic model consistent with the observed results are presented. © 1996 American Institute of Physics. View full abstract»

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  • A high‐voltage triggered pseudospark discharge experiment

    Page(s): 4887 - 4895
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    The design and execution of a pulsed high‐voltage (350–400 keV) triggered pseudospark discharge experiment is reported. Experimental studies were carried out to obtain an optimal design for stable and reliable pseudospark operation in a high‐voltage regime (≳350 kV). Experiments were performed to determine the most suitable fill gas for electron‐beam formation. The pseudospark discharge is initiated by a trigger mechanism involving a flashover between the trigger electrode and hollow cathode housing. Experimental results characterizing the electron‐beam energy using the range‐energy method are reported. Source size imaging was carried out using an x‐ray pinhole camera and a novel technique using Mylar as a witness plate. It was experimentally determined that strong pinching occurred later in time and was associated with the lower‐energy electrons. © 1996 American Institute of Physics. View full abstract»

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  • A phenomenological theory of ion‐beam synthesis of ternary compound in silicon

    Page(s): 4896 - 4906
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    A model for the annealing stage of ion‐beam synthesis of a buried layer of a ternary phase in silicon coimplanted with a relatively low dose of chemically active ions is presented. Physically, the system under investigation is a mixture of precipitates of two binary phases which are formed in the subsurface region of silicon as a result of chemical reaction between each implanted impurity and matrix atoms. During annealing, the precipitates of each binary phase function as alternative sinks for the solutes. Therefore, the ensemble of new phase inclusions is regarded as a superposition of precipitate pairs. Each pair involves the nuclei of both binary phases. The incorporation of an impurity atom into a binary phase inclusion is assumed to be controlled by the corresponding kinetic parameter. During annealing, binary phase inclusions play the role of seeds for ternary phase formation. Mathematically, the redistribution and chemical segregation of implanted species are described by a set of diffusion equations. The sink terms of the equations have been derived in the two‐particle approximation which reflects the competitive growth of two phases. Generally, this set of equations is solved numerically; however, two assumptions allow the analytic solution: there are (i) chemical segregation of the reagent is a predominant mechanism of phase formation; (ii) the phases formed have a constant chemical composition. The model is successfully applied to the description of silicon oxynitride synthesis by silicon implantation with a substoichiometric dose of oxygen and nitrogen ions. The computer simulation showed that nitrogen atoms, collected on the oxide surface, change the interface mechanism of oxide growth into that of bulk diffusion, which eventually facilitates the ternary phase formation. © 1996 American Institute of Physics. View full abstract»

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  • Amphoteric behavior and precipitation of Ge dopants in InP

    Page(s): 4907 - 4915
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    We have directly correlated the electrical behavior, the impurity lattice site location, ion damage, and the local bonding environments of Ge‐dopant ions implanted into InP. We have found that after rapid thermal annealing the free electron concentration in the samples implanted at room temperature (RT) are always higher than those implanted at liquid nitrogen temperature (LNT). Although the macroscopic structure seems to be insensitive to the implantation temperature, significantly more local disorder is created in the LNT implanted amorphous layers. Moreover, the amphoteric bonding structure of the Ge atoms is found to be well established already in the as‐implanted amorphous InP. After high temperature annealing (≳800 °C), the Ge atoms rearrange locally with more of the Ge substituting the In site than the P site resulting in n‐type conductivity. The solid solubility of Ge in the InP is measured to be ∼1.4–1.6×1020/cm3 while the free electron concentration is estimated to saturate at ∼3.4×1019/cm3. The relatively low electron concentration can be explained by Ge precipitation and the compensation of GeIn donors by GeP acceptors in the RT implanted case. The further reduction in electron concentration in the LNT implanted samples is believed to be related to the high residual damage found in these samples. The high solubility of Ge in InP can be attributed to the availability of two possible sublattice sites for the dopant and the compensation of the local strains due to the amphoteric substitution of the Ge. The concentration ratio of the GeIn to GeP determined in the heavily implanted material has been used to estimate the difference in the formation energy of Ge substituting those two different sites. View full abstract»

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  • High‐energy and high‐fluence proton irradiation effects in silicon solar cells

    Page(s): 4916 - 4920
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    We have examined proton irradiation damage in high‐energy (1–10 MeV) and high‐fluence (≳1013 cm-2) Si n+‐p‐p+ structure space solar cells. Radiation testing has revealed an anomalous increase in short‐circuit current Isc followed by an abrupt decrease and cell failure, induced by high‐fluence proton irradiation. We propose a model to explain these phenomena by expressing the change in carrier concentration p of the base region as a function of the proton fluence in addition to the well‐known model where the short‐circuit current is decreased by minority‐carrier lifetime reduction after irradiation. The reduction in carrier concentration due to majority‐carrier trapping by radiation‐induced defects has two effects. First, broadening of the depletion layer increases both the generation–recombination current and also the contribution of the photocurrent generated in this region to the total photocurrent. Second, the resistivity of the base layer is increased, resulting in the abrupt decrease in the short circuit current and failure of the solar cells. © 1996 American Institute of Physics. View full abstract»

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  • Influence of phosphorus diffusion on the recombination strength of dislocations in float zone silicon wafers

    Page(s): 4921 - 4927
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    Dislocation arrays are investigated in float zone (FZ) grown silicon wafers by the light beam induced current (LBIC) mapping technique at various wavelengths and by deep level transient spectroscopy (DLTS). The LBIC technique allows us to recognize and detect these arrays and to evaluate their recombination strength. Dislocations are found to be less recombining in (100)‐oriented FZ samples than in (111) oriented ones. In FZ dislocated wafers, a phosphorus diffusion strongly attenuates the LBIC contrast of dislocations, depending on the duration and temperature of the treatment. Electrical activity of the defects, which are still physically present, as verified by x‐ray topography, seems to disappear. Simultaneously, the peak intensities of DLTS spectra related to dislocations are reduced and this reduction depends on the phosphorus diffusion temperature and duration. © 1996 American Institute of Physics. View full abstract»

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  • Charging phenomena in low‐voltage electron microscopy of laser‐fractured fluoride surfaces

    Page(s): 4928 - 4933
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    Surfaces of fluoride crystals, fractured by a single excimer laser pulse and then covered by a thin conductive layer, are imaged by scanning electron microscopy in the low‐voltage secondary electron mode. As a result of charging, at lower primary electron energies a contrast enhancement can be obtained for surface fragments that are no longer tightly attached to the crystal. This differs from high‐energy (≳10 keV) imaging which only yields topographic contrasts and allows the analysis of the fractured structure by edge and shadowing effects. Even contrast inversion from positive to negative charging of an entire fragment can be achieved, depending on the primary electron energy. It is shown that this effect can be utilized to discriminate between fragments with a good mechanical contact to the bulk and partially detached ones by systematically studying the contrast as a function of electron energy and specimen inclination. © 1996 American Institute of Physics. View full abstract»

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  • The theory of thermodynamic‐acoustoelastic stress gauge

    Page(s): 4934 - 4943
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    Combining the thermodynamics at finite deformation with the acoustoelasticity of a specimen, which is initially stressed in three principal directions and subsequently subjected to finite uniaxial loading, we present the methods of constructing an absolute stress (or force) gauge that may be used to determine residual stresses and serve as an alternative to dead weight for calibration of load cells. Formulas for the effective Young’s modulus and Poisson’s ratio, both evaluated at a current stress level, are derived in terms of thermodynamic elastic coefficients and stresses, which are generally equal to the initial stresses plus applied stresses. It is shown that the effective adiabatic Young’s modulus and Poisson’s ratio can be obtained from relevant wave speeds measured in various directions. The true principal stress under uniaxial loading can be calculated, if one measures directly the dimensional changes in three principal directions and relevant wave speeds in various directions and makes use of the adiabatic‐isothermal conversion of the Young’s modulus and Poisson’s ratio. If the applied stress is measured the initial or residual stress can be calculated. One the other hand, if the initial stresses are zero and the applied stress is unknown, one can calculate the applied stress, which may be used to calibrate a load cell in a wide range of forces exceeding 1000 tons. © 1996 American Institute of Physics. View full abstract»

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  • Diffusion parameters of indium for silicon process modeling

    Page(s): 4944 - 4947
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    The diffusion parameters of indium in silicon are investigated. Systematic diffusion experiments in dry oxidizing ambients at temperatures ranging from 800 to 1050 °C are conducted using silicon wafers implanted with indium. Secondary‐ion‐mass spectrometry (SIMS) is used to analyze the dopant distribution before and after heat treatment. The oxidation‐enhanced diffusion parameter [R. B. Fair, in Semiconductor Materials and Process Technology Handbook, edited by G. E. McGuire (Noyes, Park Ridge, NJ, 1988); A. M. R. Lin, D. A. Antoniadis, and R. W. Dutton, J. Electrochem. Soc. Solid‐State Sci. Technol. 128, 1131 (1981); D. A. Antoniadis and I. Moskowitz, J. Appl. Phys. 53, 9214 (1982)] and the segregation coefficient at the Si/SiO2 interface [R. B. Fair and J. C. C. Tsai, J. Electrochem. Soc. Solid‐State Sci. Technol. 125, 2050 (1978)] (ratio of indium concentration in silicon to that in silicon dioxide) are extracted as a function of temperature using SIMS depth profiles and the silicon process simulator PROPHET [M. Pinto, D. M. Boulin, C. S. Rafferty, R. K. Smith, W. M. Coughran, I. C. Kizilyalli, and M. J. Thoma, in IEDM Technical Digest, 1992, p. 923]. It is observed that the segregation coefficient of indium at the Si/SiO2 interface is mIn≪1, similar to boron; however, unlike boron, the segregation coefficient of indium at the Si/SiO2 interface decreases with increasing temperature. Extraction results are summarized in analytical forms suitable for incorporation into other silicon process simulators. Finally, the validity of the extracted parameters is verified by comparing the simulated and measured SIMS profiles for an indium implanted buried‐channel p‐channel metal–oxide–semiconductor field‐effect‐transistor [I. C. Kizilyalli, F. A. Stevie, and J. D. Bude, IEEE Electron Device Lett. (1996)] process that invol- ves a gate oxidation and various other thermal processes. © 1996 American Institute of Physics. View full abstract»

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  • Numerical solution of the electromigration boundary value problem under pulsed dc conditions

    Page(s): 4948 - 4951
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    The one‐dimensional electromigration boundary value problem under pulsed dc conditions is numerically investigated by utilizing the transmission‐line matrix modeling method. A perfectly blocking boundary, where void formation and failure occur, is assumed at one end of an interconnection line. At the other end, two physically plausible boundary conditions are considered. From the design‐rule point of view, an approach is proposed to convert conveniently the pulsed stress into an equivalent dc stress that would produce electromigration damage at a similar rate. Based on the fundamental diffusion‐drift model, we show that the vacancy buildup behavior under a pulsed dc stress γp can be described accurately by the dc stress γdc scaled according to the duty factor r of the current pulse, namely, γdc=rγp. This study also represents a theoretical confirmation for the (jr)-2 dependence of the pulsed electromigration failure (where j is the current density), which has been observed in a number of experimental studies. © 1996 American Institute of Physics. View full abstract»

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  • Effect of copper on the microstructure and electromigration lifetime of Ti–AlCu–Ti fine lines in the presence of tungsten diffusion barriers

    Page(s): 4952 - 4959
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    A systematic study was performed of the microstructural and electromigration characteristics of Ti–Al(Cu)–Ti laminate structures fabricated from two metal wiring levels 1 μm in width. The total Cu content in the Al(Cu) core layers was varied from 0.5 to 2.0 wt %. A high degree of 〈111〉 texture was found for all Cu concentrations except for the 0.5 wt % film. Grain size statistics were found to be independent of the Cu concentration. The Al grains were supersaturated with Cu which led to shifts in resistance during low temperature baking and electromigration testing. The electromigration lifetime of stripes connected to large reservoirs of Cu and Al was found to be linearly dependent on the total Cu content, whereas there was a ‘‘roll off’’ in the lifetime of two‐level W stud structures as the Cu content was increased. The activation energy for electromigration induced failure was found to be 0.78–0.93 eV. Resistance shifts during electromigration and temperature only stressing and the microstructural characteristics of failed structures were explained in terms of the distribution of Cu in the Al matrix and the geometry of the structures using a blocking boundary model. © 1996 American Institute of Physics. View full abstract»

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  • Formation and characterization of Si/SiO2 multilayer structures by oxygen ion implantation into silicon

    Page(s): 4960 - 4970
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    Buried double oxide structures in Si have been produced by the sequential high‐ and low‐energy implantation of oxygen ions at 2 MeV and 90 keV, respectively. Each implantation step was followed by a high‐temperature anneal at 1300 °C for 6 h. Fourier transform infrared reflection spectroscopy has been used in order to characterize the as‐implanted and annealed samples. Rutherford backscattering spectroscopy/channeling analysis was also carried out for selected samples. The morphology of the two buried layers is the same as for the single energy implants. No interaction or transport of oxygen between the two layers is observed. The in‐between buried Si layer as well as the Si overlayer are of high crystal quality and could be potentially used as waveguiding layers, in a Si‐based optical waveguiding structure. © 1996 American Institute of Physics. View full abstract»

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Aims & Scope

Journal of Applied Physics is the American Institute of Physics' (AIP) archival journal for significant new results in applied physics

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Editor
P. James Viccaro
Argonne National Laboratory