bluuebunny/crossref_metadata_2025_split huggingface dataset:
Gettering Processes for Sub-Micron VLSI
Authors: Andrews John 
Published: March 2011

ABSTRACTGettering by the dislocation network caused by P-diffusion into the back surface of Si wafers at 950° C for 1 hr. is often used for VLSI. However, transistors with sub-micron gates are jeopardized at 950°C because of possible source-drain punch through by lateral P-diffusion. The temperature dependence of gettering by P-diffusion has been investigated at 950, 900, and 850°C. Gettering by P-diffusion was found to be marginal at 900°C and totally ineffective at 850°C.Recently published data on the solubility and diffusivity of interstitial oxygen in Czochralski-grown Si has been used to develop a simple out-diffusion model for denuded zone formation during thermal oxidation. Comparison with experimental observations on samples with high interstitial SiO2 concentration [Oi]0, exposed to dry oxidation at 1100° C for various times up to 8 hrs. and followed by 24 hr. anneals in N2 at 700°C and 1050°C, reveal that SiO2 precipitation occurs when the supersaturation ratio exceeds 4.7. The model implies an optimum denuding temperature near 100° C for a dry oxidation time of 4 hrs. The bulk defect density was also observed to decrease more than a factor of 5 as the denuding time was increased from 0 to 8 hrs.Intrinsic gettering by SiO2 precipitates in Czochralski-grown silicon has been evaluated over a wide range of initial interstitial oxygen concentrations 15 < [Oi]0 < 22 ppma with and without a HI-LO-HI pre-process annealing cycle. Among samples of approximately 100 p-n junctions per wafer, reductions of 1–3 orders of magnitude in reverse leakage at 5 volts were achieved in the worst 10% of 500 μm square devices on wafers that were exposed to the HI-LO-HI heat treatment. Intrinsic gettering is most effective when [Oi]0 22 ppma, but leakage reduction among the worst diodes is achieved at the expense of a 2 or 3-fold increase in median leakage.
Inside Submicron MOSFETS
Authors: Skocpol W. J. 
Published: March 2011

ABSTRACTNanofabrication techniques allow us to carve out narrow (40 nm) conducting channels and multiple voltage probes inside a submicron portion of a “conventional” silicon MOSFET. The repeated capture and emission of single electrons at a particular interface trap can be observed, because this changes the number of scatterers, producing sudden switching of the conductance. The dependence of capture and emission rates on lattice temperature, electron temperature, and gate voltage are consistent with a simple “configuration coordinate” model of the coupling between the trapped electron and the surrounding lattice. At low temperatures, the electrons being scattered diffuse considerable distances Lϕ before losing quantum phase information. When measured at scale Lϕ, random quantum interference causes a typical (rms) conductance change of e2/h = (25.8 kΩ)−1 (“universal conductance fluctuations”). From this, the resistance fluctions at longer and shorter voltage probe spacings can be predicted. Each scatterer substantially affects the quantum interference throughout a region of size Lϕ.
Electron Bean Induced Defects in Silicon/Indium Oxide Heterojunctions and Interfacial Reactions During Annealing
Authors: Kar S. , Pandey A. , Dwivedi R. K. 
Published: March 2011

ABSTRACTSi/In203 diodes have been prepared by e-beam evaporation of In203 tablets. Annealing of these devices was carried out in N2 and H2 /N2 mixture at 1 atm. in the temperature range of 400–800°C. Experimental data indicated a large increase in the Schottky barrier height and growth of interfacial oxide during annealing. The interface state density was reduced by a factor of 2, but the results indicated the increase in the barrier height to be mainly due to reduction of positive fixed charge density.
A Soluble Polydiacetylene, P4BCMU, As a Negative Electron Beam Resist
Authors: Marrian C. R. K. , Colton R. J. , Snow A. , Taylor C. J. 
Published: March 2011

ABSTRACTThe polydiacetylene with urethane substituents, P4BCMU, has been investigated under e-beam irradiation. A thin, ∼ (100nm), coating can be applied to a silicon wafer by spin coating from a solution in chloroform. E-beam exposure of around 20μC/cm2 renders the polymer insoluble and resistant to a CF4 /O2 plasma etch and a RIE with freon 112. Features down to .2μm have been drawn and etched in this way. X-ray Photoelectron Spectroscopy indicates only a slight change in stoichiometry and suggests the irradiated polymer has tertiary amide characteristics. Fourier Transform Infra Red and Raman spectroscopies indicate that the unsaturated carbon bonds in the backbone of the polymer are not destroyed by e-beam irradiation. Rather the main changes occur in the N-H and the C=O (carbonyl) bonds of the urethane group.
Thermal and Mechanical Properties of Cyclized Polybutadiene Dielectrics
Authors: Wilkins C. W. , Bair H. E. , Chan M. G. , Hutton R. S. 
Published: March 2011

ABSTRACTWe have studied some of the physical and mechanical properties of cyclized polybutadiene (CBR) dielectrics by dynamic mechanical analysis, thermal mechanical analysis, thermogravimetry, infrared analysis, and differential scanning calorimetry. Of interest is the difference in properties between thin (<30 μm) films which have been cured under vacuum and those which have been cured in air. Our results indicate that curing under vacuum prevents oxidation and reduces crosslinking. Vacuum cured films have 20% smaller moduli and 200 lower glass transition temperature than do films produced in air.
Microfabrication Technologies for Advanced VLSI Devices
Authors: Horiike Y. , Yoshikawa R. , Okano H. , Nakase M. , Komano H. , Takigawa T. 
Published: March 2011

ABSTRACTRecent progress in microfabrication technologies for advanced VLSI devices, such as 16M and 64MDRAM, is presented. First, an EB delineator with a vector-scanned VSB on a moving stage has been developed for printing 0.25 μm patterns employing PMMA, high dose exposure, and 50 KeV EB. Optical lithography also has been extended toward lower submicron geometry. A Krf excimer laser reduction projection system, using a quartz/CaF2 lens, resolves successfully 0.35 μm patterns. Ga field ion beam technology has been developed with new applications in fuse-cutting of redundancy and in optimizing sense amplifier by cutting transistor gates in the SRAM device. For fine line etching technology, collimated reactive ions produced by 10−3 Torr magnetron discharge achieves deep Si trench etching and tapered Al etching by using a polymer deposition process in addition to the original thin sidewall film. Finally, a damage-free excimer laser etching process has been developed which can etch n+ poly-Si with resist mask and with pattern transfer using an optics down to 0.5 μm and 0.9 μm resolutions respectively.
Imaging of III-V Compound Superlattices by Hrem and Rem
Authors: De Cooman B. C. , Conner J. R. , Summerfelt S. R. , McKernan S. , Carter C. B. , Shealy J. R. 
Published: March 2011

ABSTRACTTwo techniques for the analysis of III-V compound superlattices are examined. It has been proposed that high-resolution TEM of [100]-oriented thin foils would give an improvement in layer contrast compared with [110]-oriented thin foils; it is shown here that the contrast of [100]-oriented superlattices is not necessarily better. Moreover, both high resolution and conventional dark-field imaging may be subject to significant diffraction contrast effects resulting from the bending of the reflecting planes near the surface of the sample. Reflection electron microscopy (REM) of cross-sectional (110) cleavage planes can also yield dark-field superlattice images and selected area RHEED patterns can in principle be used to determine reliably the superlattice strain as surface effects are minimized.
Effects of Self-Ion Bombardment on Al/Si(n) Schottky Barrier Formation
Authors: Wong J. , Mei S.-N. , Lu T.-M. 
Published: March 2011

ABSTRACTWe have employed a nozzle jet expansion technique to deposit Al thin film on chemically cleaned Si(n) surface. Pure Al is evaporated in a graphite crucible at a temperature of 15 50°C and is then ejected through a small nozzle into a vacuum region of 10-6 Torr. The Schottky barrier height of the as-deposited films is measured (using the J-V technique) to be 0.77eV, which is substantially higher than that obtained by conventional evaporation-deposition techniques(≤0.68eV). Our result suggests that an intimate Al/Si(n) contact has been formed during the jet expansion deposition of Al films.During the deposition, the Al jet beam can be partially ionized by electron bombardment. It is shown that the Schottky barrier height remain unchanged if a bias potential of V s0.5KeV is applied to the substrate during deposition. For Va >0.5 KeV, the diode became leaky and the barrier height was reduced. The energetic of the jet beam, with and without post ionization and acceleration, is discussed with respect to thin film and interface formation.
The Structure of Al/GaAs Interfaces
Authors: Liliental-Weber Zuzanna , Nelson C. , Gronsky R. , Washburn J. , Ludeke R. 
Published: March 2011

ABSTRACTThe structure of Al/GaAs interfaces was investigated by high resolution electron microscopy. The Al layers Were deposited in a molecular beam epitaxy chamber with a vacuum base pressure of <1×10∼8 Pa. The GaAs substrate temperature varied during Al deposition from -30°C to 400°C. Deposition of Al on cold substrates £25°C resulted in epitaxial growth of (001) Al on (001) GaAs. Droplets of Ga were observed in samples with the substrate temperature at -30°C (1×2) and 0°C (c(2×8)). Postannealing of the last sample caused formation of the AlGaAs phase. Deposition of Al on hot substrates (150°C and 400°C) resulted in the formation of the AlGaAs phase, which separated (110) oriented Al from (001)GaAs.
High-Resolution Core Level Studies of Interdiffusion and Reaction at Metal-Semiconductor Interfaces
Authors: Del Giudice M. , Joyce J. J. , Boscherini F. , Capasso C. , Weaver J. H. 
Published: March 2011

ABSTRACTWe present a detailed microscopic investigation of interactions and reactions occurring at refractory-metal silicon interfaces at room temperature. High resolution core level photoemission results for Ti coverages in the range 0.2–16 monolayers on cleaved Si(111)2×1 show that three new distinct Si environments are created by semiconductor surface disruption. In agreement with heats of formation or electronegativity differences, all the chemical shifts are at lower binding energy. Each of them represents a different metal-Si coordination or configuration. Analogous results for Sc overlayers indicate that at least two reacted species are present. For both Ti and Sc, the reaction is started at submonolayer coverages. Analysis of the Si 2p intensity attenuation curves shows an evolution characterized by the sequential growth of the different species. Indeed, each species grows, reaches saturation, and is then attenuated. This is associated with the competition between diffusion and reaction at the interface.
Atomic Registry at the Pt-Si Interface Studied by Transmission Channeling RBS
Authors: Abelson John R. , Sigmon Thomas W. 
Published: March 2011

ABSTRACTTransmission channeling Rutherford scattering of MeV ions is one of the only techniques which can probe the atomic registry at a “buried” internal interface between a thin film and single-crystal substrate. Interfacial intermixing, dislocations, and reconstruction can be observed at concentrations above ∼ 3×1015 atoms/cm. The physical basis for this measurement is the “flux-peaking” effect, which is well known in conventional ion channeling as a method to determine the lattice location of dilute impurities. Transmission channeling is conceptually similar, but the scattering arises from the interface at the exit side of a thin single crystal sample rather than from a volume effect.In this work, we apply transmission channeling to measure the low temperature intermixing between Pt and Si. In a previous study, we suggested that a disordered interface forms prior to crystalline suicide formation. The present results are a quantitative measurement of the area density of Si which intermixes with Pt at 150°C. Experiments are performed using 80A Pt layers e-béam deposited onto 1–2μm thick single crystals of Si(100) and (111) following various interfacial cleaning procedures. We find that >1×1016 Si atoms/cm2 are displaced from their lattice sites after Pt deposition, increasing to ∼2×1016/cm2 upon annealing to 150°C. The room temperature intermixing of >6 monolayers of Si is large, but not inconsistent with existing studies of the Pt - Si reaction. The transmission channeling measurement includes any Si segregated at grain boundaries or the free surface as well as the interface. No systematic differences are observed as a function of substrate orientation or cleaning procedure.
Studies of MZS and MZOS Structures with Zinc Oxide Deposited by Conventional Rf Diode and Magnetron Sputtering Techniques
Authors: Venkatesh S. N. , Ramakrishnan E. S. , Jungling K. C. , Krupanidhi S. B. 
Published: March 2011

ABSTRACTHighly crystalline and c-axis oriented zinc oxide thin films were sputter deposited from a ceramic target using rf diode and magnetron sputtering techniques. A comparative evaluation of structure and electrical characteristics of ZnO films in the MZS and MZOS configurations is presented and the results are discussed. The physical and electrical properties were significantly influenced by highly energetic particles originating from the presence of oxygen neutrals in the plasma during the growth process and the behavior differed between the diode and magnetron sputtering processes.
Metallurgical Reactions in Au/Ge/Au Contact to Gallium Arsenide
Authors: Kim Taeil , Chung DDL , Mahajan S 
Published: March 2011

ABSTRACTTransmission electron microscopy (TEM), was used to study the interfacial structure resulting from the alloying reaction of a Au/Ge/Au film on (100) GaAs. The metallurgical reaction at 400°C results in the previously unknown hexagonal Au3Ga phase. The crystal structure of the AuoGa phase is proposed based on the observed diffraction patterns and the lattice image The well-known fcchcp coherent jnterface is observed between Au and Au3Ga such that (111)Au // (0001)Au3Ga and [110]. // [1120]Au2Ga. In addition to Au3Ga, other Au-Ga compounds (Au7Ga2, Au2Ge), a Au-Ge metastabil phase, and a Au-Ge-As ternary phase were observed after annealing. After annealing above 400°C, epitaxially regrown GaAs crystallites on the underlying GaAs substrate were revealed by cross-section TEM. The current flows through these Ge-doped regrown GaAs regions and the contact becomes ohmic The size and density of the regrown GaAs crystallite increase with increasing annealing temperature between 400 and 500°C; this explains the decreasing tendency of contact resistance with increasing annealing temperature.
Silicon Membrane Studies of Point Defect Transport Kinetics During Thermal Oxidation
Authors: Ahn S. T. , Shott J. D. , Tiller W. A. 
Published: March 2011

ABSTRACTSelf-interstitial transport kinetics in float-zone and Czochralski silicon was studied during thermal oxidation of silicon membranes. Bulk recombination of interstitials is higher in the CZ than in the FZ silicon. The low apparent interstitial diffusivity obtained in this study is explained by a bulk effect.
Growth and Characterization of Chemically Vapor Deposited Beta-Sic Epilayers on 6H Alpha-Sic Substrates
Authors: Kong H. S. , Glass J. T. , Davis R. F. , Nutt S. R. 
Published: March 2011

ABSTRACTHigh quality, β-SiC (111) monocrystalline films have been epitaxially grown via chemical vapor deposition at 1683K on hexagonal 6H αc-SiC (0001) using a (SiH4 + C2H4)/(H2) gas flow rate ratio of 1:3000. Cross-sectional transmission electron microscopy showed almost no line or planar defects at the film/substrate interface and a low density within the bulk of the film. Furthermore, high resolution transmission electron microscopy revealed a coherent β-SiC/α-SiC interface. Secondary ion mass spectrometry indicated that the diffusion of the Al in the substrate into the as-grown film was negligible. Unintentionally doped films are n-type with the carrier concentrations virtually always in the range of 1016-1017cm3, as determined by capacitance-voltage measurements. A gold-β-SiC Schottky diode having an ideality constant of approximately 1.6 was fabricated on the β-SiC epilayer.
Doping Effects in GaAs/AlGaAs Superlattices
Authors: Chambers Frank A. , Vojak Bruce A. 
Published: March 2011

ABSTRACTWe present the results of a study we have done to explore the effects of high levels of Be dopant, >1×1019 /cm3, in GaAs/AlGaAs superlattice structures. The materials were grown using Molecular Beam Epitaxy (MBE) at 680 C using standard growth conditions. The samples were studied using a variety of structural, optical and electrical probes. Structural data obtained from Auger and SIMS profiling is presented as well as optical data from photoluminescence and Raman scattering. We also present the results of electrochemical profiling of the samples. The results of these studies provide evidence of intermixing of the superlattice during growth with sufficiently high Be levels. We have found evidence for a concentration threshold in the diffusivity of Be in these structures. We also find that the dominant mechanism for Be redistribution in these samples appears to be diffusive in nature rather than due to surface riding.
Stress Release in Ion Implanted Lattice Mismatched Semiconductor Heterostructures
Authors: Arnold G. W. , Picraux S. T. , Myers D. R. , Doyle B. L. , Peercy P. S. , Biefeld R. M. , Dawson L. R. 
Published: March 2011

ABSTRACTCantilever-beam measurements of ion-implantation induced stress in (InGa)As/GaAs, Ga(AsP)/GaP, and Ga(AsP)/GaAs strained layer superlattices (SLSs), grown either by molecular-beam epitaxy (MBE) or metalorganic chemical vapor deposition (MOCVD), have shown that a mechanism for precipitous stress-relief can be operative, f or room-temperature damage -energy deposition values above - 2 × 10 keV/cm. This phenomenon is correlated with the initial residual compressive stress on the composite structure and is determined by the differences in lattice parameter between the substrate and the buffer alloy-layer.
Effects of Implant Temperature on Disordering of AlAs-GaAs Superlattices
Authors: Dobisz E. A. , Tell B. , Craighead H. G. , Schwarz S. A. , Tamargo M. C. , Harbison J. P. 
Published: March 2011

ABSTRACTThe effect of implant temperature, superlattice period, and directional diffusion has been studied for silicon impurity-enhanced compositional disordering of GaAs-AlAs superlattices (SL) of 9 ran and 16 nm period. The SL were implanted with Si at temperatures of 483 K, 293 K, and 77 K, with an energy of 100 keV and dose of 2.5 × 1014 cm-2. These were examined by cross-sectional transmission electron microscopy and secondary ion mass spectro-scopy for structural and compositional information. The damage due to implantation prior to annealing is strikingly less for superlattices than for bulk GaAs. All annealed samples exhibited disordering, with the 9 nm period SL exhibiting a deeper disordered region than the 16 nm SL. The greatest enhancement was found in the 9 nm period SL implanted at 77 K, in which the disordering extended from a depth of 25 nm to =300 nm. The mixing was found to be anisotropie, with the SL mixing propagating greater in depth than in the lateral directions. The result has important implications for high resolution patterning possibilities with this method.
Photoemission Study of the Physical Nature of the InP Near-Surface Defect States
Authors: Chin K. K. , Cao R. , Kendelewicz T. , Miyano K. , Yeh J. J. , Doniach S. , Lindau I. , Spicer W. E. 
Published: March 2011

ABSTRACTThe physical nature of the InP near-surface defect acceptor and donor states are studied by using photoemission spectroscopy. It is found that the In/n-InP(110) interface band bending does not start until the In coverage reaches about 0.3 monolayer (ML), while the In/p-InP(110) band bending is almost saturated at 0.3 ML. The annealing effect on the band bending of clean cleaved n-and p-type InP(llO) surfaces is also studied. It is found that annealing of the clean surface creates an irreversible band bending effect on the p-InP(110), but the n-InP(110) almost does not show any band bending after low temperature annealing. Based on these two striking differences in the band bending behavior of n- and p-type InP, it is proposed that the physical nature of InP near-surface defect acceptor and donor levels may be different and that phosphorus vacancies are the cause of p-InP surface Fermi level pinning.
Atomistic Calculation of Stability and Metastability of Coherently Strained Silicon-Like Structures
Authors: Dodson Brian W. , Taylor Paul A. 
Published: March 2011

ABSTRACTMonte Carlo based microscopic techniques were used to study the stability and metastability of thin coherently strained layers of mismatched siliconlike semiconductor material grown on the (111) silicon surface. The structural energy was calculated using three-body empirical potentials. For layers greater than about 20 Å thickness, the critical layer thickness associated with thermodynamic stability agrees quantitatively with continuum theory. For thinner layers, however, considerable variations from the continuum theory are found. For a strained layer six monolayers thick, the test system is found to be metastable against the nucleation of misfit dislocations to a lattice mismatch of about 11%, compared to the 4% equilibrium stability limit.
Theoretical and Experimental Description of Interface Structure
Authors: Hull R. , Carey K. W. , Reid G. A. 
Published: March 2011

ABSTRACTWe define the Interface between two dissimilar materials by two functions, g(z) and f(x,y), representing the diffuseness along the interface normal and the distribution of interface non-planarities respectively. We show how these functions may be measured for the case of epitaxial interfaces between dissimilar crystals by quantitative analysis of lattice structure images obtained by high resolution transmission electron microscopy. Experimental examples are drawn from the GeSi/Si, InGaAs/InAlAs and InGaAs/InP systems. Correlations between interface structure and optical and electronic properties of these systems are discussed.
Compositional Studies of Semiconductor Alloys by Bright Field Electron Microscope Imaging of Wedged Crystals
Authors: Eaglesham D. J. , Hetherington C. J. D. , Humphreys C. J. 
Published: March 2011

ABSTRACTThe use of a cleaved 90 degree wedge as a cross section sample for transmission electron microscopy allows the composition of III/V semiconductor alloys to be measured by studying the thickness fringes of the on-axis [010] bright field image. The effect is explained in terms of the incident electron Bloch states and is illustrated by reference to GaAs/AlGaAs. The technique has an accuracy of about 5% and a spatial resolution of a few Å. The range of materials that can be analysed in this way is discussed.
Grain Growth in Vapor Deposited Aluminium Alloys
Authors: Köster Uwe , Ho Paul S. 
Published: March 2011

ABSTRACTIn a number of vapor deposited aluminium alloys grain growth has been investigated systematically by means of quantitative electron microscopy and found to proceed not by grain boundary migration, but by grain coalescence. Parameters influencing the observed mode of grain growth will be discussed with respect to the formation of microstructures with optimal resistance to electromigration, i.e. microstructures with large grain size, high homogeneity in the grain size distribution as well as a strong texture.Analyses of grain size distribution after annealing indicate a strong retardation in grain growth by the solute in all aluminium alloys except Al(Cu). Relative large grain sizes and very small lognormal standard deviations have been observed in Al-l%Cu as well as ternary Al(Cu,Hf) thin films.