bluuebunny/crossref_metadata_2025 huggingface dataset:
On The Origin of The Coarse and Fine Contrast Modulation in Epitaxial InGaAs Strained Layers Grown On InP Substrates.
Authors: PeirÓ F. , Cornet A. , Roura P. , Morante J.R.
Published: April 2011

In this paper we summarise the TEM observations carried out on InxGa1-xAs strained layers grown by Molecular Beam Epitaxy on (100) InP substrates (xIn in the range 54.3%-62.5%). The evolution of the modulation wavelength with the epilayer thickness, growth temperature (Tg) and layer-substrate strain is reported. The quantification of the amplitude of the composition variation linked to the coarse contrast modulation from the theoretical fitting of the Optical Absorption spectra is also presented. In view of these results we suggest a model for the appearance of the contrast modulations in ternary and quaternary III-V alloys according to the different structural configurations driven by the alloy stabilisation inside the miscibility gap due to the minimization of the free Gibbs energy as Tg increases.
InAs Island Quantum Box Formation and Vertical Self-Organization on GaAs (100) Via Molecular Beam Epitaxy
Authors: Xie Qianghua , Kobayashi N. P. , Ramachandran T. R. , Kalburge A. , Chen P. , Madhukar A.
Published: April 2011

In-situ, ultra high vacuum combined scanning tunneling microscope/atomic force microscope (STM/AFM) studies were undertaken to examine the initiation of 3D InAs islands on GaAs (100) and their density and size distribution as a function of growth conditions. A decreasing island density with increasing As4 pressure is observed and points to the significance of strain in affecting In migration and As4 incorporation. A stack of InAs islands separated by GaAs spacer layers exhibit a vertically self-organized growth. Through analysis of a phenomenological model, this is shown to be a consequence of a directional In adatom migration caused by the islandinduced nonuniform strain fields.
Phase Stability and Electronic Structure of GaAs1–xNx Alloys
Authors: Neugebauer JÖrg , Van De Walle Chris G.
Published: April 2011

We investigate the electronic structure and stability of GaAs1–xNx alloys for several compositions, using state-of-the-art first-principles total-energy calculations. We consider several ordered structures, and in addition we address the case of low-dimensional structures, such as zero-dimensional point defects (NAs in GaAs). Our results reveal two rem ark-able features of this alloy system: (i) a very large bowing of the band gap (the system may even become metallic for compositions around x = 0.5) and (ii) a very limited miscibility. Both properties are related to a distinctive property of this alloy system: a more than 20% lattice mismatch between GaAs and GaN.
Asymmetric Mosaic Spread During Relaxation in SiGe/ Si Strained Layer Superlattices Grown on Miscut Substrates
Authors: Nam S. , Goorsky M. S.
Published: April 2011

The evolution of defects in SiGe/Si strained layer superlattices (SLS)-with thickness and composition near the critical thickness -was investigated. The structures were grown on 2° miscut (001) substrates by ultrahigh vacuum chemical vapor deposition. The samples were then annealed between 700 °C and 900 °C. After annealing, the satellite peak intensity from double axis diffraction decreased and triple axis diffraction showed that this decreased intensity was due to increased mosaic structure. Interestingly, for some of the annealed samples, the (004) reciprocal space maps showed an asymmetric mosaic spread, indicating a preferential tilt. This result stems from a preferential propagation of certain types of misfit dislocations due to the substrate miscut.
Deep Photoluminescence Bands in Mbe Grown Si and Sige.
Authors: Buyanova I.A. , Henry A. , Chen W.M , Ni W.X. , Hansson G.V. , Monemar B.
Published: April 2011

Broad photoluminescence (PL) bands with energy position ranging from 0.70 to 1.03 eV, are shown to appear in Si epilayers and Sil−xGex/Si heterostructures grown by molecular beam epitaxy under non-optimized conditions. The presence of a particular broad band (BB) is found to be determined by the growth conditions, in particular by the bias applied to the substrate during the growth. Ion bombardment during the growth is shown to be a main factor enhancing the formation of BB-related defects. To clarify their origin, the effects of post-growth hydrogen treatments and of an external magnetic field are investigated. The BBs are shown to be related to various types of radiative centres, either point or extended defects. A correlation between X-ray diffraction and PL measurements is also observed. The spatial location of the BB-related defects is inferred by results from optically detected cyclotron resonance (ODCR) and PL excitation studies.
Effects of Lateral Limited Area and Substrate Compliance on Strain Distribution and Critical Thickness of Sige Film on Si Mesa Substrates
Authors: Rong Zhang , Hongbin Huang , Yi Shi , Kai Yang , Shulin Gu , Ronghua Wang , Shunming Zhu , Youdou Zheng
Published: April 2011

In this paper, we calculated theoretically the strain distribution and the critical thickness of the SiGe epilayers on Si(100) mesa structural substrates by considering the effect of the compliance of substrates, along with the effect of the limited area, and found that the compliance of substrates was relevant not only to its thickness, but also to their lateral size. The introduction of substrate compliance significantly reduced the total strain energy in the epilayers, and increased the critical thickness. That approach was realized by growth on the mesa substrates. The TEM observations confirmed the results of calculations.
Sil−xGex/Si Multiple Quantum Well Wires Fabricated Using Selective Etching
Authors: Yi Shi , Feng Wang , Jianlin Liu , Rong Zhang , Shulin Gu , Shunming Zhu , Lique Hu , Youdou Zheng
Published: April 2011

Using lithography, and selective etching the Si1-xGex/Si multiple quantum well wires are fabricated. The characteristics of the selective chemical etching of Si1-xGex and Si are investigated, and high-performance etchants are developed. The etchant composed of HF:NH4F:H202:NH4OH is used for the etching of the epitaxial Si1-xGex films, the selectivity is better than 250 for Si0.76Ge0.24, and increases with the increase of the mole fraction x of Ge. Another etchant composed of NH4NO3:NH4OH is used for the etching of Si, the selectivity is higher than 1000 ( x ≥ 0.1 ). A preliminary photoluminescence (PL) result obtained from the Si0.76Ge0.24 multiple quantum well wires is presented. As the linewidth of the wires is reduced down to 50 nm, an intense complicated PL spectrum in the wavelength range of 500∼800 nm is observed at liquid nitrogen temperature. The origin of such spectrum is unclear.
Ion-Enhanced Chemical Reaction of XeF2 with Silicon by Modulated Molecular Beam Mass Spectrometry
Authors: Balooch M. , Olander D. R. , Siekhaus W. J.
Published: April 2011

The reaction of XeF2 with the Si(100) surface was studied by modulated (10–1000 Hz) molecular beam-mass spectrometry in the temperature range 300–1300K and equivalent XeF2 pressure of 5×10−6 to 10−4 Torr. Simultaneous bombardment of the reacting surface by Ar+ was used to determine the extent of ion-enhancement of the reaction.

In the absence of the ion beam, the main reaction product was SiF4, which was formed with a reaction probability of ˜5×10−2 at room temperature. In the presence of the ion beam three products, SiF4, SiF2 and F2 (or F), were detected with formation probabilities of ˜1×10−1, 6×10−2 and 7×10−2 respectively. Increasing surface temperature reduced the ion-enhanced reactivity.
New Devices for the Production of Intense Pulsed Jets of CF2: Laser Spectroscopic Characterization
Authors: Knickelbein Mark B. , Webb Douglas A. , Grant Edward R.
Published: April 2011

We report the development of two new sources for the production of intense pulsed jets of atomic and molecular free radicals. The present work applies these sources to the generation of the widely used semiconductor etchant, CF2, in each case characterizing the yield and internal energy distribution of this diradical by laser induced fluorescence. The methods employed modify a commercial high-vacuum compatible pulsed molecular beam valve to accept either a glow discharge or pyrolysis nozzle. The source compound for both systems is hexafluoropropylene oxide (HFPO). In each case measured yields of CF2 are high: For pyrolysis we find intensities as great as 5×1017 sr−1sec−1 representing nearly complete conversion of HFPO to CF2 + CF3CFO. The discharge source yields about an order of magnitude less CF2 intensity in a shorter beam-pulse which also contains ions and other atomic and molecular radicals. The vibrational energy distribution of the CF2 varies with source conditions, with the hottest CF2 produced by the pyrolysis source at high temperature.
X-Ray Photoelectron Spectroscopy Analysis of Silicon Oxide Deposited by a Nitrous Oxide/Silane Glow Discharge
Authors: Thomas J. H. , Kaganowicz G.
Published: April 2011

Thin layers (100Å) of SiO were deposited at room temperature in a RF glow discharge in a nitrous oxige – silane ambient. Surface properties of the deposit were studied using quantitative and qualitative XPS and AES. Abrupt changes in the energy difference between the O 1s and Si 2p photoelectron peaks, the O/Si stoichiometric ratio, and nitrogen incorporation are observed with varying amounts of silane in the gas ambient (for a fixed nitrous oxide flow). The abrupt change in binding energy difference correlates with the presence of free oxygen in the glow discharge as measured by in-situ mass spectrometry. At silane flows below the abrupt change, nitrogen is excluded from the deposit and the surfaces appear to be chemically silicon dioxide with a O/Si ratio of 2.1 as determined from quantitative XPS analysis. Above the abrupt change, the films exhibit a surface composition of less than 2.0.
Temperature, Velocity, and Species Mapping in an Induction Plasma
Authors: Donaldson A. D. , Batdorf J. A. , Fincke J. R. , Varacalle D. J. , Richardson L. S.
Published: April 2011

As part of an effort to determine the feasibility of carbothermic reduction of alumina in plasmas, spatial distributions of temperature, velocity and species in the plume of an argon radio-frequency plasma with alumina and carbon additions were estimated using a two dimensional theoretical model of the flow field and a thermochemical model based on equilibrium conditions. Experimentally determined boundary conditions were input to the models. Using a 30 kW inductively coupled plasma, experimental measurements were made to allow comparison with predictions. A practical process for carbothermic reduction will require prevention of back reactions, either by separation of the aluminum species or by some kind of quenching of the process. The significance of the experimental results and comparisons with predictions are discussed.
Crystallization, Doping, Orientation and Grain-Size of Microcrystalline Silicon and Germanium
Authors: Tsu Raphael , Brazil S. P.
Published: April 2011

Preparation and characterization of microcrystalline silicon are discussed. In addition to the usual characterization techniques using TEM,X-ray, Auger, etc., Raman scattering and electro-reflectance measurements have been extensively incorporated into routine analyses. In particular, conductivity percolation, detection of trace crystallites in an amorphous matrix, measurements of grain-size, doping as well as preferred orientation are fully discussed. The single most important effect on the properties of microcrystalline Si and Ge is the presence of impurities. Thus better technical performances must be preceded by an improvement in vacuum and purer gases used in deposition systems.
Plasma Deposition of Wide Gap, Highly Photoconductive a-Si:H Thin Films from Disilane-Helium Mixtures
Authors: Rajeswaran G. , Vanier P. E. , Corderman R. R. , Kampas F. J.
Published: April 2011

Wide gap (>1.9 eV), photoconductive, intrinsic amorphous silicon films were made in a UHV system from Si2H6 -He mixtures. The hydrogen concentrations, optical gaps and photoconductivities were measured. Unlike films made from SiH4, Si2H6-produced films exhibit excellent electronic properties even at low deposition temperatures. The ratio of AM1 photoconductivity to dark conductivity was as high as 107.
Modeling Thermal Plasma Material Processing Experiments
Authors: Varacalle D. J. , Richardson L. S. , Mc Ilwain M. E.
Published: April 2011

Arstract

Spatial distributions of plasma variables (concentration, temperature, and velocity) were calculated for alumina and carbon species injected in an argon thermal plasma. The plasma behavior was modeled from arc initiation through free plume expansion by combining a plasma code with a plume code. The model assumed a direct current, constrictor type, arc heater. This research, supported by the U.S. Bureau of Mines under the Strategic and Critical Materials Program, is examining the feasibility of using thermal plasmas for ore reduction. The process investigated in this paper is the carbothermic reduction of alumina.
Plasma Enhancement in Direct Nitridation of Silicon and Silicon-Dioxide
Authors: Ito T. , Kato I. , Ishikawa H.
Published: April 2011

Effects of plasma on direct nitridation of Si and SiO2 have been investigated. The reactor consisted of a quartz tube, SiC-coated carbon-susceptors and an RF-induction coil. The electrical probe technique was used to detect floating potential of the susceptor having Si substrates. The voltage distribution between the susceptor and plasma is influenced by nitridation ambient, pressure, reactor geometry and RF power. The predominant species in NH3 plasma is NH radicals which are thought to be negatively charged in an ion sheath formed around the susceptor. The Cabrera-Mott model has been successfully applied to analyze the nitridation mechanism. Plasma enhancement is mainly caused by activation of characteristic velocity of nitridation species rather than by an increase in the electric field appearing in a film. Enhancement due to fluorine incorporation is also explained with the model. Bombardment of ionic species causes sputtering and deposition resulting in damage, contamination and thickness nonuniformity. Optimizing the plasma conditions, decrease in nitridation temperature, increase in growth rate, and improvements in film composition and interfacial structure have been obtained. It has been found that the further nitridation proceeds, the lower Nss becomes. This technique offers various advantages to the VLSI dielectric process.
Studies of Plasma O Atom Concentration by Two-Photon Laser Induced Fluorescence and Optical Emission Spectroscopy
Authors: Walkup R. , Saenger K. , Selwyn G. S.
Published: April 2011

We report quantitative measurements of the concentration of atomic oxygen in RF plasmas determined by two-photon laser induced fluorescence. The results are compared with concurrent measurements of spatially resolved plasma induced optical emission. These measurements establish: (1) the O atom concentration as a function of plasma parameters, (2) a semi-quantitative relationship between O* emission intensity normalized by Ar* in-tensity and O atom concentration, and (3) an understanding of the mechanisms for pro-duction of excited atoms in the plasma.
Laser Diagnostics of Semiconductor Processing Systems
Authors: Wormhoudt Joda C. , Stanton Alan C. , Silver Joel A.
Published: April 2011

Two processes of great importance in the semiconductor industry are vapor deposition and plasma etching. This paper presents a review of laser techniques for spectroscopic characterization of the gas phase species involved in these processes. Band strength and other spectroscopic data for selected molecules are used to give estimates of the detection sensitivity in vibrational and electronic bands. Preliminary results are given from work presently in progress in our laboratory on the detection of such species. The discussion includes examples of the application of these techniques to a number of laboratory deposition and etching devices.
Scanning Tunneling Spectroscopy of Photoexcitations on a Nanosecond Time-Scale
Authors: Ruskell Todd G. , Chen Dong , Sarid Dror
Published: April 2011

Scanning tunneling spectroscopy of the high frequency response of photoexcited carriers in the layered structure semiconductors n–type MoS2 and p–type Wse2 is demonstrated using the beat frequency of the longitudinal modes of a HeNe laser at the tunneling junction. We analyze the optical response taking into account the effects of tip-induced band bending and surface states.
Does 0.1 Micron = MACH 1?
Authors: Pease R. Fabian
Published: April 2011

The drive to increasingly higher density ultra-large-scale-integration (ULSI) (of electronic circuits) is fuelled primarily by cost; on-chip interconnects are far cheaper than the less dense offchip interconnects. At the same time the escalating cost of an IC factory (‘fab’) is making headlines as it goes through $1B and a large part of this escalation is the cost of high performance lithography tools. The lithographic technology to go below 0.1μm will almost certainly be very different from an extension of today's optical projection and the cost of replacing today's technology will be enormous. A second drawback to higher density is the resistance of narrow interconnects. As a result some people have suggested that this situation is analogous to that of airliner speed which increased over a period of thirty years from about 100 mph to close to 600 mph but has not increased in the last 35 years. Still faster speed was technically possible, and hence was pursued by the military, but is uneconomical for most commercial use. Current technology might take us to 0.1μm which will probably be state of the art 10 years hence so technologies for replacing optical lithography e.g. scanned arrays of proximal probes should be researched now. Other challenges include how to achieve useful interconnect networks employing 50 nm features.
Self-Assembled Monolayer Films for Nanofabrication
Authors: Dobisz Elizabeth A. , Perkins F. Keith , Brandow Susan L. , Calvert Jeffrey M. , Marrian Christie R.K.
Published: April 2011

Central to nanofabrication is the ability to transfer a pattern from an imaging layer to a device or structure. At the smallest dimensions (<20 nm), thin resists or imaging layers have been used exclusively. The transfer of a pattern that is formed in a thin layer resist presents severe technological challenges to resist materials development. A novel approach based on self-assembling monomolecular layer resists is demonstrated with two organosilane films, formed from (aminoethylaminomethyl)phenethyltrimethoxysilane (PEDA) and 4-chloromethylphenyltrichlorosilane (CMPTS). The molecules have separate chemical functionalities for binding to a Si substrate and for promoting chemistry leading to catalysis and the growth of an electroless plated metal film. STM lithographic exposure destroys the ability of the molecule to bind to a catalyst, which initiates an electroless metallization. This forms the basis for a selective imaging and the pattern transfer process. A 25 nm thick Ni layer acts as a very robust etch mask, even as the unmasked regions of Si are etched as deep as 5 μm by reactive ion etching with SF6. With our process 15 nm lines with 3.3 nm edge roughness have been fabricated in the plated Ni and etched into the underlying Si. The development of the resist process and the STM lithography will be described and the resolution of the approach will be discussed.
Nanoscale Structures by Laser Direct Writing in Silicon
Authors: Dirac H. , Müllenborn M. , Petersen J. W.
Published: April 2011

Laser-induced pyrolytic etching of silicon by chlorine has been used to process structures with nanoscale resolution. A direct write system has been designed, based on an Ar ion laser with a UV-option, on-axis optics, acousto-optic beam modulation, and high resolution translation stages for sample displacement and for focusing.

The resolution of the process is determined by the size of the melt generated by the focused laser beam. The melt size is a function of optical power, and resolutions better than the focused laser spot diameter are achieved by reducing the power onto the silicon sample. In this way we have etched trenches with a resolution better than 150 nm. We demonstrate feature sizes of about 40 nm by closely spacing etched trenches. The minimum width of these features is determined by the etch selectivity. The feature width depends on the trench geometry, line spacing, and on scan speed, due to heat flow confinement.
Nanolithography Developed Through Electron Beam Induced Surface Reaction
Authors: Matsui S. , Ochiai Y. , Baba M. , Fujita J. , Watanabe H. , Manako S. , Ohnishi Y. , Ogai K. , Kimura Y. , Shimizu R.
Published: April 2011

Nanolithography has been studied by using electron beam technology. Ten-nm linewidth PMMA resist patterns have been demonstrated by 50 kV scanning electron beam. The self-developing properties of a AlF3 doped LiF inorganic resist under a scanning electron beam irradiation with energy of 20–50 keV have been studied for sub-10 nm lithography. By optimizing the inorganic resist film quality, 5 nm linewidth patterns with 60 nm periodicity were directly delineated under a 30 keV electron beam. Another approach for nanolithography using electron beam holography has been proposed. Line and dot patterns with 100 nm periodicity were exposed on PMMA resist by electron beam holography with thermal field emitter gun and an electron biprism. Subsequent atomic force microscope observation has confirmed that both patterns are successfully fabricated. This technique allows us to produce nanoscale periodic patterns simultaneously. The selective atomic desorption of Cl atoms adsorbed on a Si (111) 7×7 surface has been studied by field evaporation using a scanning tunneling microscope (STM). The STM tip is placed on the adsorbed Cl on the surface, and pulse voltage was applied. This results in selective atomic desorption of Cl.
Manufacture of Submicron Light-Emitting Porous Silicon Areas for Miniature LEDs
Authors: Duttagupta S. P. , Peng C. , Tsybeskov L. , Fauchet P. M.
Published: April 2011

We have investigated several methods to form submicron-size porous silicon regions. Porous silicon can emit light from the violet to past 1.5 μm with high photoluminescence efficiency at room temperature. It is composed of a high density of nanometer-scale crystalline silicon wires or dots. To integrate light-emitting porous silicon (LEPSi) LEDs with conventional Si microelectronics, it is necessary to produce miniature LEPSi regions adjacent to fully protected crystalline silicon regions. These techniques can be divided into two groups. In the first group formation of LEPSi is prevented during electrochemistry. Using optical and electron beam lithography, and a trilayer process with silicon nitride or amorphization by ion-implantation, we have made LEPSi patterns as small as 100 nm. In the second group, the formation of LEPSi during electrochemistry is enhanced by ion-milling or reactive ion-etching which we have found to help the pore nucleation. We have used a variety of mapping techniques, such as photoluminescence, atomic force and electron beam microscopies, to characterize the sharpness of the interface between the porous silicon and crystalline silicon regions.
Microstructure of Agglomerates of Nanometer Particles
Authors: Weber Alfred P. , Thorne James D. , Friedlander Sheldon K.
Published: April 2011

The microstructure of an agglomerate can be characterized by the coordination number. The relationship between the fractal dimension and the coordination number of agglomerates of nanometer particles was investigated in experiments and computer simulations. The results for silver agglomerates formed by laser ablation agreed well with the simulations. The coordination number is low for low density fractals because of the large fraction of surface particles which have fewer bonds. The sensitivity of the coordination number to the fractal dimension increases with increasing fractal dimension.
Dielectric Properties Of Low Dielectric Constant Polymeric Materials
Authors: Ip Flora S. , Ting Chiu
Published: April 2011

Multilevel interconnects for high performance ULSI need low dielectric constant materials for inter-metal layer dielectric, or ILD, to reduce signal propagation delay, power consumption and cross talk noises. We have studied the physical, dielectric and processing properties of a wide variety of promising low dielectric polymeric materials for ILD applications. This paper presents capacitance values measured over a wide range of temperature, and a summary of the measured dielectric properties. The anisotropy 1,2 of dielectric properties were determined experimentally, the vertical (out-of-plane) dielectric properties were determined by MIM (Metal-Insulator-Metal) measurements, and the horizontal (in-plane) dielectric properties were determined by intra-line measurements of sub-half micron serpentine and comb test structures.
Glass Transition Temperature Of Ultrathin Polymer Films On Silicon
Authors: Wu Wen-Li , Wallace William E , Zanten John Van
Published: April 2011

The glass transition temperature, Tg, of polystyrene (PS) thin films on silicon wafers with different surface preparations was determined in order to explore the effect of interfacial interaction energy on local chain dynamics. To enhance interface behavior, the film thickness included in this work was as low as 50 Å. PS with monodisperse molecular weights was chosen as a model polymer. Two different silicon surfaces were prepared: sulfuric acid-clean and hydrogen passivated. Tg of thin films was determined by monitoring the film thickness as a function of temperature. Tgwas identified as the temperature where the thermal expansion coefficient underwent an abrupt change. X-ray reflectivity was used to determine film thickness with a precision of a few angstroms. Tg of PS was found to depend strongly on the initial film thickness, as well as the substrate surface.
Preparation And Properties Of Fluorinated Amorphous Carbon Thin Films By Plasma Enhanced Chemical Vapor Deposition
Authors: Endo Kazuhiko , Tatsumi Toru
Published: April 2011

Fluorinated amorphous carbon films are proposed as low dielectric constant interlayer dielectrics for ULSI circuits. The films are deposited by plasma enhanced chemical vapor deposition with CH4, CF4 and C2F6 in a parallel-plate rf (13.56 MHz) reactor and a helicon wave reactor. In a parallel-plate reactor, the dielectric constant of the amorphous carbon films deposited with CH4 increases with increase in rf power. Addition of CF4 to CH4 reduces the dielectric constant to 2.1 and raises the deposition rate. However etching reaction occurs with high CF4/CH4 ratios. No film grows with only CF4. XPS measurement reveals that the F atoms are introduced into the amorphous carbon films. Helicon reactor has higher plasma density and is expected to achieve higher deposition rate for productive use. In this reactor, fluorinated amorphous carbon films without hydrogen content can be obtained with only CF4 and C2F6 gases. The growth rate of the films reaches 0.3 μ/min with C2F6 and 0.15 μ/min with CF4 at a source power of 2 kW and a gas flow rate of 100 sccm. With heating up to 300°C in a vacuum for 1 hour, the thickness of the films deposited with C2F6 does not shrink while that of films with CF4 shrinks.
Material Characterization Of Methyl Siloxane Sogs
Authors: Numata Ken , Seha Thomas R. , Jeng Shin-Puu , Tanaka Tsuyoshi
Published: April 2011

Methyl siloxane spin-on-glass (SOG) is a conventional gap-filling material. In accordance with the requirement of low permittivity, many of major SOG suppliers are developing new types of methyl siloxane SOGs.

The most interesting property of these SOGs is their permittivity, which we measured by making stack structures of Al-0.5%Cu / TEOS CVD SiO2 / SOG / n+ Si. We also studied I-V characteristics, refractive indices, FT-IR spectra, stress, and moisture resistance.

All of the SOGs showed small stress and fair moisture resistance. Leakage currents were less than 2.5E-10 A/cm2 for bias voltages up to 5V. Permittivities ranged from 2.9 to 3.6. We observed a correlation between permittivity and FT-IR spectral features associated with Si-O-Si bonds. Reducing the number density of Si-O-Si bonds may be an effective way to lower the permittivity of this class of SOGs
Silica Aerogel: An Intrinsically Low Dielectric Constant Material
Authors: Hrubesh Lawrence W.
Published: April 2011

Silica aerogels are highly porous solids having unique morphologies in which both the pores and particles have sizes less than the wavelength of visible light. This fine nanostructure modifies the normal transport mechanisms within aerogels and endows them with a variety of exceptional physical properties. For example, aerogels have the lowest measured thermal conductivity and dielectric constant for any solid material. The intrinsically low dielectric properties of silica aerogels are the direct result of the extremely high achievable porosities, which are controllable over a range from 75% to more than 99.8%, and which result in measured dielectric constants from 2.0 to less than 1.01. This paper discusses the synthesis of silica aerogels, processing them as thin films, and characterizing their dielectric properties. Existing data and other physical characteristics of bulk aerogels (e.g., thermal stablity, thermal expansion, moisture adsorption, modulus, dielectric strength, etc.), which are useful for evaluating them as potential dielectrics for microelectronics, are also given.
Methods And Needs For Low K Material Research
Authors: Ting Chiu H. , Seidel Thomas E.
Published: April 2011

For several years the industry has recognized the need of developing low k dielectric material and high conductivity metal for high performance interconnect. Low k dielectric will impact both power and delay favorably, while higher conductivity metal will reduce delay time. In order to be useful, new low k dielectric materials must be carefully characterized for their electrical, chemical, thermal and mechanical properties. In addition, their impact on process integration, fabrication cost and device reliability must also be considered. Since the gestation period for introducing a new material is very long, a set of standard testing methodologies are required to speed up the development process. This review will discuss various material options and the progress of material development and characterization methodologies. Example results will be provided for assessing these parameters.
Vapor Deposition Of Very Low K Polymer Films, Poly(Naphthalene), Poly(Fluorinated Naphthalene)
Authors: Lang C. -I. , Yang G. -R. , Moore J. A. , Lu T. -M.
Published: April 2011

Several novel processes have been developed in our lab to synthesize and deposit polymers that have extremely low dielectric constants (below 2.5) as thin films. These reactive intermediates are condensed onto wafers in a vacuum chamber and no chemical waste is produced. Furthermore, cold traps can be used to recover uncondensed monomers through the pumping system. Because of the extremely low dielectric constant, very low moisture uptake and high temperature stability of these vapor depositable materials, these environmentally friendly polymers are very attractive for future electronic applications as interlayer dielectrics. Examples are Parylene-F(fluorinated), poly(naphthalene) (PNT-N), poly(fluorinated naphthalene) (PNT-F), and Teflon AF 1600 (amorphous). These films were deposited at substrate temperatures between −20 and 350 °C and at deposition pressure was 10−4−2.5 Torr. The film thicknesses were between 0.1–10 μ. and dielectric constants were between 1.9–2.5. The thermal stabilities of these films were between 360–590 °C. Among them, poly(fluorinated naphthalene) dissociates at about 590 °C. Poly(naphthalene) and poly(fluorinated naphthalene) are obtained as films by vaporizing monomers in vacuo and transporting the vapor to a hot surface.
Substrate Effects on The Nucleation and Growth of GaSe Layers by Van Der Waals Epitaxy
Authors: Rumaner Lee E. , Gray J.L. , Ohuchi F.S. , Ueno K. , Koma A.
Published: April 2011

Epitaxial thin film multilayers are limited by the need for both lattice and thermal expansion matching. Recently, a new deposition technique, known as van der Waals epitaxy, has been developed to overcome these limitations. Van der Waals Epitaxy (VDWE)promises the ability to deposit multilayers based on the property of interest without being limited by lattice and thermal expansion mismatch. The crystallographic two dimensional metal chalcogenides are characterized by strong covalent bonding within a layer and weak van der Waals bonds between layers. By combining the layered nature of the metal chalcogenides with other layered materials as well as crystallographic 3D materials, oriented single crystal layers can be deposited, resulting in novel structures with atomically abrupt interfaces. However, even with the weak van der Waals bond, substrate/film interactions play a large role in the final structure.

To study the substrate/film interaction occurring during van der Waals Epitaxy growth on 3D surfaces, the metal chalcogenide GaSe has been systematically deposited on GaAs(1 11) substrates. To develop an understanding of the interaction of the substratewith the growing film, growth of GaSe on both atomically rough and smooth substrates was studied. Comparison of the information developed through RHEED, TEM and AFM have been used to understand the basic nucleation and growth process as well as the observation and formation of film defects.
Aluminum/Copper Nanocomposites Fabricated by The Jet Vapor Depositiontm Process
Authors: Lankey Rebecca L. , Hsiung L.M. , Wadley H.N.G. , Karecki S.M. , Smith D.T. , Halpern B.L. , Schmitt J.J.
Published: April 2011

Aluminum and copper nanolaminates have been fabricated at Jet Process Corporation using the novel, proprietary Jet Vapor DepositionTM (JVD)TM process. Laminates with a total thickness of 10 μm were made by depositing alternating layers ofapproximately equal thicknesses of copper and aluminum onto preheated silicon wafers at asubstrate temperature of ∼140 °C. The layer thicknesses were systematicallyvaried between 20 nm and 1 μm. The microstructure and properties of the laminates were investigated using transmission electron microscopy (TEM), scanning electron microscopy (SEM), and nanoindentation methods. TEM has shown that the laminates have a strong {111} texture. The hardness results show that above a critical layer thickness of approximately 50 nm, the yield strength of the composites varies inversely with thelayer thickness, while the strength of nanolaminates with layer thicknesses smaller than the critical thickness is better explained by the Koehler model. An alternative model recently proposed by Embury and Hirth fits the data equally well.
Effect of Magnetic CoZrNb Seed Layers on Pd/Co Multilayers
Authors: Morris Jonathan C. , Liu Wenhong , Lairson Bruce M.
Published: April 2011

Pd/Co multilayers are candidates as perpendicular magnetic recording media. A softmagnetic underlayer can both improve crystallographic orientation and reduce the magnetostatic energy of recorded domains. Pd/Co multilayers have been deposited onto silicon nitride by DC magnetron sputtering with and without CoZrNb (CZN) seed layers. Cross-sectional transmission electron microscopy shows that the CZN layer imposes a columnar grain structure on the multilayer film through epitaxy. Seeded multilayers have columnar 200Å grains that begin at the CZN interface and extend through the film thickness. In contrast, the grains in unseeded multilayers are not columnar. X-ray rocking curves on the (111) Pd/Co peak show that the CZN seed layer improves the (111) crystallographic texture of the multilayer film. We observe a correspondence between FWHM rocking curve widths in the CZN and the subsequently deposited multilayer. The CZN seeding produces changes in perpendicular hysteresis loops, which are attributed to an exchange interaction and a change in the multilayer amicrostructure due to seeding.
Structural and Chemical Characterisation of Ni/Ti Multilayers with TEM
Authors: Leifer K. , Buffat P.A. , Böni P. , Clemens D. , Friedli H.P. , Grimmer H. , Anderson I.S.
Published: April 2011

Ni/Ti multilayers were prepared by argon sputtering. We observe changes of latticeparameter, strain, grain size and texture depending on the single layer thickness and thepressure of the sputter gas. Moreover the quality of the layers can be improved by including impurities during the growth of the Ni and the Ti layers. Generally the results show that such additions lead to more planar layers and to structural changes within the individual layers. Although we observe hexagonal Titanium in the as-deposited films, some of the specimens which were prepared for TEM observation reveal an fcc-Ti structure.The chemical composition of the layers has been investigated in a field emission microscope using a probe diameter of nmmC. omposition profiles were determined by evaluating EELS spectra taken at each point in an automated scan, In this way it was possible to determine residual concentrations of Ni in Ti layers lower than 0.5%. In the samples studied the interface width appears to be of the order of 4-5nm and the concentration profiles of Ni—Ti interfaces appear to be different from those of the Ti—Ni interfaces.
Measuring Enthalpies of Formation Using Thick Multilayer Foils and Differential Scanning Calorimetry
Authors: Weihs T.P. , Barbee T.W. , Wall M.A.
Published: April 2011

The exothermic, solid state reaction of Al and Zr has been studied in thick AL/Zr multilayers using Differential Scanning Calorimetry and X-ray diffraction. The multilayersamples were magnetron sputter deposited into highly textured alternate layers of Al and Zr with nominal composition A13Zr. The samples used in this study were 47μm thick with a 427Å period. When samples were isochronally scanned from 25º to 725ºC, a large exotherm at ˜350ºC was followed by one or two smaller exotherms at ˜650ºC. The first exotherm is dominated by a diffusionbased reaction of Al and Zr that produces two phases in isochronal scans: amorphous AI-Zrand cubic A13Zr, and two additional phases in isothermal anneals: A12Zr and tetragonal AI3Zr. The exothermic heat from this multi-phase reaction is measured using isochronal scans and isothermal anneals, and the heat flow is analyzed using a l-D diffusion based model. An average activation energy and a diffusion constant are determined. In the isothermal scans, the total exothermic heat increases linearly with √ime, and layer thicknesses vary linearly with heat.
A Model of Superlattice Yield Stress and Hardness Enhancements
Authors: Chu XI , Barnett Scott A.
Published: April 2011

A model is presented that explains the yield stress and hardness enhancements that have been observed in superlattice thin films. The predicted strength/hardness enhancement increased with increasing superlattice period, Λ, before reaching a saturation value that depended on interface widths. The results indicate that superlattice strength/hardness depends strongly on interface widths and the difference in shear moduli of the two components for Λ values below the maximum, and on the average shear modulus for larger Λ.
Enhanced Hardness and Stress-Driven Delamination in Fe/Pt Multilayers
Authors: Daniels B.J. , Nix W.D. , Clemens B.M.
Published: April 2011

Polycrystalline Fe/Pt multilayers of varying bilayer period, Λ, were sputter deposited onto SiO2 at room temperature. Film structure was characterized by x-ray diffraction, hardness was determined using nanoindentation, and stresses were examined with wafer curvature. The Fe layers were shown to be predominantly {110} oriented while the Pt layers were mostly {111} oriented. The hardnesses of these multilayer films were enhanced over the rule of mixtures value by a factor of almost 3 and exhibited a dependence on Λ which was similar to that previously observed in epitaxial Fe(001)/Pt(001) multilayers. The hardnesses of the polycrystalline multilayers were higher than those of the epitaxial multilayers, presumably due to grain boundary strengthening in these films. Film stress was large (∼1.5 GPa) and compressive, resulting in buckling-driven delamination of the film from the substrate for films with 40≤Λ≤100 Å. Delamination occurred in the “telephone cord” morphology and was observed in real time. A qualitative discussion of our observations of this delamination mechanism is presented.
Beryllium-Based Multilayer Structures
Authors: Stearns D. G. , Skulina K. M. , Wall M. , Alford C. S. , Bionta R. M. , Makowiecki D. M. , Gullikson E. M. , Soufli R. , Kortright J. B. , Underwood J. H.
Published: April 2011

Multilayer (ML) structures composed of Mo-Be, Ru-Be and Rh-Be with bilayer periods of - 6 nm have been grown using dc magnetron sputter deposition. The ML microstructure has been characterized using x-ray diffraction and high-resolution transmission electron microscopy, and the normal incidence reflectivity has been measured at soft x-ray wavelengths.
Tem Study of Crystallization of a-SiC in Contact With Silver
Authors: Zh Nanchang , Sinclair Robert
Published: April 2011

Metal mediated crystallization of an amorphous phase has been found in many systems, in which eutectic phase diagrams are formed. It is interesting to know if an amorphous phase containing two elements, which can form compound, can react and form a crystalline compound at a low temperature in contact with metals. In this paper we studied the Ag/Sil−xCx system by transmission electron microscopy(TEM). It was foundthat amorphous silicon carbide was crystallized into cubic SiC at about 800°C in areas containing Ag. The silver diffused and segregated into the a-SiC phase upon annealing. The silver grains in the original deposited layer as well as those segregated act as nucleation sites for the crystallization of β-SiC. A nucleation temperature as low as 800°C was observed.
XPS, AES and Leed Studies of The Interaction Between The Si(100) 2×1 Surface and Cadmium Deposited at Room Temperature
Authors: Santucci S. , Nardo S. Di , Lozzi L. , Passacantando M. , Picozzi P.
Published: April 2011

Very thin films of cadmium, with a mean thickness between 1 Å and 500 Å, were deposited by thermal evaporation in ultra-high-vacuum on a Si(100) 2×1 surface held at room temperature. In situ X-ray Photoelectron Spectroscopy and Auger Electron Spectroscopy were performed in order to investigate the interaction between the silicon substrate and the deposited cadmium. In samples with deposited mean thickness up to 3 Å, cadmium and silicon are found to be strongly interacting. In fact both XPS and AES spectra show evident changes in shape and energy position leading to the conclusion that a chemical compound between Cd and Si is formed. No diffusion between cadmium and silicon is observed, so the cadmium atoms deposited after the first 3 Å show a bulk character. The analysis of the first derivative intensity of the Si L23VV and Cd M5N45N45 Auger signals, varying the amount of deposited Cd, indicates the formation of islands in the early stage of the Cd growth. These islands show an amorphous structure as observed by using the LEED spectroscopy.
Electrical Properties of (Zn, Mn) Containing Multilayer Metallizations to p-Type InGaAs/InP
Authors: Leec Patrick W. , Reeves Geoffrey K. , Zhou Wei
Published: April 2011

The specific contact resistance, pc, of Au/Zn/Au, Ni/Zn/Ni/Au, Pd/Zn/Pt/Au and Pd/Mln/Sb/Pd/Au contacts to p-In0.47Ga0.53As/ InP has been measured as a function of layer thickness of Zn or Mn. All of the as-deposited contacts were ohmic, with pc = 1−2 × 10−5 Ω cm2. Increasing thickness of the Zn layer above 200 Å in the Au/Zn/Au contacts resulted in a minor decrease in pc while producing no change in the Ni/Zn/Ni/Au metallization. For the as-deposited Pd/Mn/Pd/Au contacts, the value of pc was independent of thickness of the Mn layer but differences in pc emerged at annealing temperatures of ≥ 250°. The analysis of these structures by RBS has shown an extensive intermixing of the metal layers at an annealing temperature of 450 °. In the Pd/Zn/Pt/Au contacts, the value of pc was reduced to a minimum value of 8 × 10−6 Ω cm2 by annealing at a temperature of 500 °. An examination of the Pd/Zn/Pt/Au configuration by RBS has shown that the Pt layer acted as a barrier for the indiffusion of the Au.
The Influence of a-Si:H/Substrate Interface on Electronic Properties Of Me-a-Si:H - Substrate Structures
Authors: Budaguan B.G. , Aivazov A.A. , Meytin M.N.
Published: April 2011

We have performed the investigations of temperature dependencies of dark conductivity σd(T) in a-Si:H films deposited on different substrates (glass, oxynitride, polyimide film) at the temperature range of 20 °C to 250 °C. The temperature dependence of dark conductivity of a-Si:H on glass and oxynitride demonstrates the “kink” at 80 –160 °C. This “kink” wasn't observed in σd(T) measurements of a-Si:H on polyimide. It has been shown that the appearance of “kink” is connected with substrate material, value of applied electric field and its polarity. The relaxation nature of the “kink” is also suggested. Two transport mechanisms of charge carriers are proposed - transport via material bulk and transport via a-Si:H/substrate interface. It is shown that “kink” occurs when transport via interface becomes predominant. The mathematical simulation of this process is also presented.
The Preparation of Crystalline NbSe2/TiSe2 Superlattices from Modulated Elemental Reactants
Authors: Noh Myungkeun , Thiel James , Johnson David C.
Published: April 2011

Three new crystalline NbSe2/TiSe2 superlattice compounds with 43.472±0.005A, 80.66±0.03A and 117.9±0.1Å unit cells in thec direction were prepared through controlled crystallization of Ti/Se/Nb/Se superlattice reactants with different compositional layer thicknesses. Theta-theta and rocking curve data were collected using a theta-theta diffractometer to study the evolution of the initially layered reactants into the crystalline superlattices as a function of temperature. Low angle diffraction data demonstrates that the initial layered reactant contracts in the c-axis direction upon initial annealing and suggests that the interfaces become smoother during this initial interdiffusion. High angle rocking curve diffraction data shows the development of caxis oriented NbSe2fTiSe2 crystal growth perpendicular to the substrate surface. Theta-theta scans show a gradual decrease of the (001) diffraction linewidths of the growing compound as a function of annealing time and temperature indicating an increase in the c-axis domain size. High quality caxis oriented TiSe2/NbSe2 crystalline superlattices result from annealing at the relatively low temperature of 500ºC. The rational synthesis of intergrowth compounds from superlattice reactants as described herein will permit the tailoring of physical properties as a function of compositional layer thicknesses and nativeproperties of the parent compounds.
Some Characteristics of X-Ray Multilayered Thin Films Made with A Plasma Controlled System
Authors: Cilia M. , Yakshin A. , Trambly H. , Vidal B.
Published: April 2011

Multilayered structures with small periods were fabricated using RF-magnetron sputtering device. The conditions of deposition and small changes in the plasma during all deposition period was investigated by optical emission spectroscopy. We studied influence of different parameters (pressure, power, sputtered material) to emission lines corresponding to the working gas Ar and W or Si. Structure and properties of multilayers were estimated, using transmission electron microscopy (TEM) and small-angle x-ray (1.54 Å) scattering techniques. The results was compared with emission line intensities of Ar, W and Si and self-bias data written for each layer with computer during multilayer fabrication. Wediscuss X-ray reflection properties of multilayers fabricated under our conditions and correlation of emission spectroscopy analysis data with another parameters of plasma (self-bias).