bluuebunny/crossref_metadata_2025 huggingface dataset:
Room Temperature Electron Mobility Enhancement in a Strained Si Channel
Authors: Garchery L. , Warren P. , Sagnes I. , Badoz P. A.
Published: April 2011

During the last few years, Si/SiGe heterostructures have been used by several groups worldwide in order to achieve high-mobility two-dimensional electron gases.1-3 To confine high-mobility electrons, these heterosystems are grown in such a way that the Si channel, epitaxially grown on a relaxed SixGe1−x buffer, undergoes a tensile strain. As such structures have a significant conduction band offset, the spatial separation of ionized dopant atoms from mobile carriers can be exploited. The confined electrons in the Si channel are then provided by a doped SiGe supply layer. The significant improvement in SiGe buffer quality has led to low temperature mobilities exceeding 100 000 cm2/Vs with best values above 350 000 cm2/Vs.2-5 However, for MOS applications, the most interesting point is the room temperature (RT) mobility of confined electrons in the Si channel. With this aim in view, RT-mobilities between 2000 and 2600 cm2/Vs have been reported.6 These values are more than twice larger than these of commercial MOSFETs and are also higher than the bulk mobility of intrinsic Si. However, these relatively high values are still lower than the predicted ones (3000 cm2/Vs).7 This is partially due to the fact that the RT-mobility measured on modulation doped heterostructures (MDHs) is never exactly that of the confined electrons in the Si channel. The conduction electrons are in fact not completely transferred from the supply layer to the channel. The latter is the primary and desired path for conduction, but the supply layer can become a second, parallel path, with a lower mobility because of donor impurities. Different methods can be used to reduce the contribution of this parallel path. First, the supply layer can be designed with the lowest possible doping level so as to ensure an almost complete electron transfer at room temperature.8 Secondly, gated Hall devices can be fabricated using Schottky or Metal-Insulator-Semiconductor gates.9-11 These devices allow both the electron density and electron mobility in the strained Si channel to be measured for low gate voltage.
Correlation Between Photoluminescence Spectral Features and Crystal Growth Temperature for Sige Single Quantum Wells
Authors: Gerling M. , Nilsson S. , Zeindl H. P. , Jagdhold U.
Published: April 2011

Sample temperature dependence and excitation power dependence of the photoluminescence intensity were investigated with respect to growth temperature for SiGe single quantum wells grown pseudomorphically to (100)-oriented Si by molecular beam epitaxy. The determined excitation power exponents and thermal activation energies show unambiguously that defect incorporation is effectively reduced at higher growth temperatures. However, at higher growth temperatures the SiGe-related spectral distribution is found to be shifted to higher photon energy which is attributed to intermixing of Ge and Si at the heterointerfaces, governed by diffusion as well as Ge surface segregation during growth. The diffusion process is studied separately by photoluminescence measurements upon thermal annealing at different temperatures and a diffusion model is presented where the diffusion process is assumed to be composed of two different mechanisms, interdiffusion, i.e. lattice-site-exchange diffusion, and point-defectinduced diffusion. The determined activation energies for the two diffusion mechanisms are in good agreement with previous results which confirm that the model gives a realistic picture of the diffusion process.
Solid-Phase Epitaxial Regrowth and Dopant Activation of Arsenic. Implanted Metastable Pseudomorphic Ge0.08Si0.92 AND GeO.16SiO.84 ON Si(100)
Authors: Lie D.Y.C. , Song J.H. , Nicolet M.-A. , Theodore N.D. , Candelaria J. , Thomas S.G. , Tanner M.O. , Wang K.L.
Published: April 2011

Metastable pseudomorphic GexSi1−x (x=8%,16%) films were deposited on p-Si(100) substrates by chemical-vapor-deposition and then implanted at room temperature with 90 keV arsenic ions to a dose of 1.5×1015/cm2. The implantation amorphizes approximately the top 125 nm of the 145 nm-thick GeSi layers. The Si-GeSi interfaces remain sharp after implantation. Implanted and non-implanted GeSi samples, together with implanted Si control samples, were subsequently annealed simultaneously by rapid thermal annealing in a nitrogen ambient at 600,700,800 × for 10,20,40s at each temperature. The implanted samples undergo layer-by-layer solid-phase epitaxial regrowth during annealing at or above 600 ×C. The amorphized and regrown GeSi layers are always fully relaxed with a very high density of dislocations (1010-1011/cm2). At a fixed annealing temperature, strain relaxation of an implanted GeSi film is substantially more extensive than that of a non-implanted one. About 50-90% of the implanted arsenic ions become electrically active after the completion of solid-phase epitaxy. The percentages of arsenic ions that are activated in the Si control samples are generally higher than those in GeSi. The room-temperature sheet electron mobility in GeSi is roughly 30% lower than that in Si for a given sheet electron concentration. We conclude that metastable GeSi on Si(100) amorphized by arsenic ions and recrystallized by solid-phase epitaxy cannot recover both its crystallinity and its pseudomorphic strain under rapid thermal annealing.
Formation of Amorphous Interlayers by Solid–State Diffusion in Ti Thin Films on Si–ge Layers on Silicon and Germanium
Authors: Lai J.B. , Liu C.S. , Chen L.J. , Cheng J.Y.
Published: April 2011

The formation of amorphous interlayers (a–interlayers) by solid–state diffusion in ultrahigh vacuum deposited polycrystalline Ti thin film on germanium and Sil-xGex alloys grown on (001)Si has been investigated by transmission electron microscopy and Auger electron spectroscopy.

Amorphous interlayers, less than 2 nm in thickness, were observed to form in all as–deposited samples. The growth of a–interlayers was found to vary non–monotonically with the composition of Si–Ge alloys in annealed samples. On the other hand, the formation temperature of crystalline phase was found to decrease with the Ge content. The results are compared with that of the Ti/Si system. The formation mechanism are discussed in terms of thermodynamic and kinetic factors.
Strain Balanced InGaAs/GaAsP Multiple Quantum Well Modulators at 1.06 µm
Authors: Cunningham J.E.
Published: April 2011

We review growth and optical properties of strain balanced, InGaAs/GaAsP Multiple Quantum Well structures on GaAs in order to make defect free, 1.06 µm modulators. Here, we implement strain balancing near the elastic limit on a length scale of strong size quantization so as to open up a special class of semiconductors materials. In this system we find the in-plane electron mass is strain-enhanced by 30 %. This preserves both excitonic binding energy and excitonic oscillator strength. Consequently, quantum well absorption at 1.06 pan can be nearly comparable to that of a GaAs qw. Also, strain balanced materials show an improved capacity over 850 nm MQW to optically modulate light signals through the Quantum Confined Stark Effect. This is attributed to a light -heavy hole splitting of 140 meV that is caused by a large component of shear strain in these systems. Growth of strain balanced materials is challenging because the strain energy can be comparable to the surface energy that bonds atoms to the crystal. In order to accurately predict the critical layer thicknesses for strain relief as well as the reorganized surface topology, we develop a 2D-3D growth mode model.
Incorporation of Thallium in IN1−xTIxP Grown by Metal Organic Molecular Beam Epitaxy
Authors: Antonell M.J. , Abernathy C.R.
Published: April 2011

InxTll−xP has been proposed as a potential narrow bandgap material for the fabrication of IR detectors. 1 It is expected to exist in a zincblende structure with a lattice constant approximately 2% larger than aInP for x=0. In this paper we will discuss attempts to grow this alloy on InP using various combinations of elemental and gaseous sources including In, Tl, trimethylindium (TMI), triethylindium (TEI) and phosphine. The sticking coefficient of Tl was found to decrease rapidly for temperatures above 350°C, mandating the use of low temperatures. Attempts to grow TIP resulted in the formation of Tl droplets which oxidized rapidly upon removal from the vacuum system. Auger analysis of the surface shows the oxide composition to be Tl2O, indicative of a monovalent Tl oxidation state. InTlP grown under similar conditions shows an initial tendency to form structural defects, as observed by cross-sectional TEM, suggesting lattice mismatch due to incorporation of small amounts of Tl. As the Tl concentration at the growth surface is increased, a two-phase material is obtained consisting of Tl-rich droplets and InP. In addition, Auger depth profiling shows clear evidence of Tl segregation.
Spatial Resolution of Small Particles in Silane Discharge
Authors: Spears K. G. , Roth R. M.
Published: April 2011

A capacitively coupled, rf glow discharge of silane in argon was studied with laser light scattering to determine the spatial concentration of small particles. Multi-wavelength scattering profiles have been obtained and are being analyzed to obtain size distributions as a function of spatial location. Very sharply defined particle zones can be found under some plasma conditions that are spatially related to the silicon atom profiles. We will report our results and attempt to qualitatively describe how these zones relate to plasma chemistry and film deposition processes.
Studies of the Etching of Si, SiO2 and Mo by Carbon Fluorine Compounds Using Real Time Auger Spectroscopy
Authors: Thomson D. , Helms C. R.
Published: April 2011

The ion etching of Si, SiO2 and Mo by fluorocarbon ions was studied using real time Auger electron spectroscopy. The carbon in the CF3+ ions was found to react rapidly with SiO2 to form volatile products, resulting in a very low carbon concentration on the SiO2 surface. Both Si and Mo formed carbides when bombarded with CF3+ ions. This resulted in a high carbon concentration on these surfaces.
Mechanism of Dry Etching of Silicon Dioxide: a Case of Direct Reactive Ion Etching
Authors: Steinbruchel Ch. , Lehmann H. W. , Frick K.
Published: April 2011

Reactive sputter etching of SiO2 with CHF3-O2 plasmas has been investigated in a parallel plate reactor by combining etch rate measurements with concurrent determination of ion densities (using a Langmuir probe) and the composition of neutral plasma species (using a mass spectrometer). Etch rates are found to follow the ion density and to be fairly independent of the plasma chemistry under most experimental conditions. Moreover, a comparison of reactive sputter etching and reactive ion beam etching of SiO2 with CHF3 and CF4 shows that etch yields per incoming ion are essentially independent of the flux of neutral radicals to the substrate. This strongly suggests as the dominant etch mechanism for SiO2 direct reactive ion etching, where ions themselves are the main reactants in the etch reaction. Measured values of etch yields are consistent with this picture.
Silicon Etching Mechanisms - Doping Effect
Authors: Lee Young H. , Chen Mao-Min , Bright A. A.
Published: April 2011

Etch rates of heavily doped silicon films (n- and p-type) and undoped polysilicon film were studied during plasma etching and also during reactive ion etching in a CF4/O2 plasma. The etch rate of undoped Si was lower than the n+ Si etch rate, but higher than the p+ Si etch rate, when the RF inductive heating by the eddy current was minimized by using thermal backing to the water-cooled electrode. The thermal activation energy for spontaneous chemical etching was measured to be 0.10 eV, independent of the doping characteristics. This doping effect may be explained by the opposite polarity of the space charge present in the depletion layer of n+ Si and p+ Si during reactive plasma etching.
Cluster Model Theoretical Study of the Interaction and Penetration of F on a Si Surface
Authors: Bagus Paul S.
Published: April 2011

The interaction of fluorine with a three-fold open site of the Si(111) surface has been examined using a cluster model. The site considered is taken as representative of one where penetration of the surface may occur. New analyses are used to show that the interaction is ionic with F having essentially a full negative charge for all distances near the surface, both above and below. The bonding is shown to be almost entirely electrostatic between the polarized charges of the positive Si surface and F-. The F-Si binding energy is estimated taking proper account of the electron affinity of F and the ionization potential, work function, of Si. When this is done, it is shown that there is no barrier for the penetration of the Si surface by F; hence, this penetration should not be a rate limiting step in the F-Si etching reaction.
Simulation of Spatially Dependent Excitation Rates and Power Deposition in RF Discharges for Plasma Processing
Authors: Kushner M. J. , Anderson H. N. , Hargis P. J.
Published: April 2011

In low pressure, radio frequency (RF) discharges of the type used in plasma processing of semiconductor materials, the rate of electron impact excitation and energy transfer processes depends upon both the phase of the RF excitation and position in the discharge. Electron impact collisions create radicals that diffuse or drift to the surfaces of interest where they are adsorbed or otherwise react. To the extent that these radicals have a finite lifetime, their transport time from point of creation to surface of interest is an important parameter. The spatial dependence of the rate of the initial electron impact collisions is therefore also an important parameter. The power that sustains the discharge is coupled into the system by two mechanisms: a high energy “e-beam” component of the electron distribution resulting from electrons falling through or being accelerated by the sheaths, and by “joule heating” in the body of the plasma. In this paper, we will discuss the spatial dependence of excitation rates and the method of power deposition in RF discharges of the type used for plasma processing. The basis of that discussion will be results from a Monte-Carlo plasma simulation code for RF discharges. Preliminary results from a model for the etching of silicon in SF6 /O2 plasmas will be presented and evidence for long term changes in the manner of energy deposition will be discussed.
Kinetic Analysis of Chlorofluorocarbon Discharges
Authors: Sawin Herbert H. , Yokozeki Akimichi , Owens Aaron J. , Allen Kenneth D.
Published: April 2011

The fundamental plasma kinetics of chlorofluorocarbon discharges have been studied experimentally and modeled. Electrical impedance analysis of the plasma discharge during the etching process was used to estimate the average electron energy and the electron concentration. Assuming the electron-impact generation of reactant species is the rate limiting step, the etching rate of polysilicon etching was modeled using a simplified expression for the electron-impact rate coefficient for dissociation and the experimentally estimated electron densities and electron energies. Dissociative electron attachment should play a significant role in the production of etchant species at low electron energies. The lower threshold energy and the larger cross-section (σ) for dissociative attachment of chlorofluorocarbons (σmax,∼6×10-18 cm2 at ∼ 3 eV for CF3Cl) in coomprpsanrtison to that of fluorocarbons (σmax ∼0.8×10-18 cm2 at ∼7 eV for CF4 ), increases the significance of this machanism in chlorofluorocarbon discharges. In addition, the production of appreciable concentrations of C1- could influence the transport of positive ions to the electrode surfaces.
A Dual Frequency Tri-Electrode System for Etching Polysilicon
Authors: Keller J. , Giffen L. , Uchimura D. , Corn G.
Published: April 2011

The etching of polysilicon and polycide films requires both profile control and selectivity control. The use of a dual frequency tri-electrode system combined with a chlorine based chemistry have produced useful results.
Process Characterization of a Load-Locked, Reactive Ion Etching System
Authors: Hendriks Margaret M. , Shanfield S.
Published: April 2011

We report on process characterization of contact hole etching in a load-locked, hexa-gonal reactive ion etching system. Contact holes were etched in silicon dioxide and phos-phosilicate glass (PSG) with emphasis on wall profile control and selectivity to the underlayer of either single crystal silicon, polysilicon, or aluminum.

To achieve these requirements, a two stage etch process was developed. In the first stage, controlled wall taper is obtained with a mixture of CHF3 and O2. The second stage utilizes a mixture of CHF3 and a small amount of CO2 to obtain high selectivity to the underlying material. Evaluation of the effects of chamber pressure, RF power, and gas mixture on taper angle, selectivity, resist erosion, and etch rates is presented.

In addition, evidence which suggests that the reproducibility of optimum etch condi-tions can be enhanced by the use of a continuously pumped process chamber will be dis-cussed.
Replication Lithography
Authors: Deckman H. W. , Dunsmuir J. H.
Published: April 2011

A new method has been developed which allows submicron patterns to be rapidly copied from a master into an inorganic substrate. Physical repli-cation and lithographic pattern transfer are combined to produce a wide variety of surface textures on large area substrates. Physical replication techniques are used to create a polymeric intermediate transfer mask which is then used as an etch mask on the substrate. Both positive and negative copies of the original pattern can be created using this process. Final pattern transfer is accomplished by dry processing, allowing precisely controlled alterations of the aspect ratios in the original pattern. Using this process it is possible to fabricate extremely large area submicron sized surface textures (such as diffraction gratings) which are useful in many areas of science and technology.
Structural Studies of Microcrystalline Silicon Films Produced by Sputtering
Authors: Moustakas T. D. , Weitz D. A. , Prestridge E. B. , Friedman R.
Published: April 2011

A number of microcrystalline silicon films have been deposited by RF sputtering and their structure was investigated by Raman spectroscopy, X-ray scattering, SEM, TEM and IR spectroscopy. The interpretation of these results suggests that the film growth proceeds initially via amorphous island formation and that the degree of crystallization of the final film depends on subsequent solid phase crystallization during the time of growth. The size and the preferred orientation of the crystallites correlates with the columnar growth habit of the films while the rest of the amorphous matrix is shown to exhibit a considerable degree of order.
Mechanisms of Plasma Oxidation of Si
Authors: Siejka J. , Perriere J.
Published: April 2011

Fundamental aspects of the interaction between non equilibrium, low pressure oxygen plasma and Si (silicides) are described. The kinetics of oxide growth in oxygen atmosphere, in plasma at low pressure (p<∼ 1 Torr) and low temperature (T < 1 800°C) regimes are reviewed and the Cabrera-Mott mechanism is postulated i.e. the oxidation process is controlled by ion injection at the plasma/oxide interface. The mechanism of electron injection and conduction during plasma anodization is reviewed and discussed in the frame of theory of high current injection in MIS structure. Enhancement of oxide growth rate due to the irradiation (laser), bombardment by electrons or ions is reviewed and compared to the plasma oxidation. Spectacular enhancement of the anodization rate of Si covered by a thin deposited layer of zirconia or hafnia oxide is analyzed. The anodization rate of Si deposit through ∼’ 0.5 mm YSZ single crystal substrate is evoked as an example of potentiality of plasma anodization process. The mechanism of movement of oxygen ions and of cations deduced from 160/180 experiments is discussed. A few examples of applications of Si plasma oxidation processes are presented.
Quantitative Studies of Glow-Discharge Deposition Using Optical Emission Spectroscopy
Authors: Kampas F. J.
Published: April 2011

Intensities of CH optical emission and electrical properties of methane rf discharges as a function of pressure are presented and discussed. The results are consistent with a model in which the properties of the discharge are dominated by secondary electrons traversing the gap between the electrodes.
Formation of Sub-100 NM GE Wires on Si by E-Beam Evaporation/Lithography
Authors: Deng C. , Wu J. C. , Barbero C. J. , Sigmon T. W. , Wybourne M. N.
Published: April 2011

A fabrication process for sub-100 nm Ge wires on Si substrates is reported for the first time. Wires with a cross section of 6 × 57 nm2 are demonstrated. The wire structures are analyzed by atomic force (AFM), scanning electron (SEM), and transmission electron microscopy (TEM). Sample preparation for TEM is performed using a novel technique using both pre and in situ deposition of multiple protection layers using a Focused Ion Beam (FIB) micromachining system.
Atomic Diffusion and Strain Measurement on Si Grating Structures by X-Ray Diffraction
Authors: Tanaka So , Umbach Christopher C. , Shen Qun , Blakely Jack M.
Published: April 2011

We have applied high resolution synchrotron X-ray diffraction to two-dimensional (2D) Si gratings with wavelengths of 300 and 400nm. We show that this method is very sensitive to both the geometry (grating wavelength, height, and angle of inclined sidewall) and the state of strain. Morphology changes produced by vacuum annealing can be detected so that the mass transport rates on Si surfaces can be measured. Strain measurements show that grating pillars covered with 1 lnm of thermal oxide were under tension (ε = 3.7 × 10−4). This strain was elastically relaxed by removing the oxide.
TiO2 Nanophases Formed Using the Sol-Gel Technique
Authors: López T. , Gómez R. , Boldú J. L. , Muñoz E. , Bokhimi  , Novaro O.
Published: April 2011

We have prepared nanoparticles of titania using the sol-gel technique. The samples were characterized by FTIR, DTA, TGA, EPR and XRD. The properties observed with these techniques are correlated in the temperature region between 200 and 800°C. The Ti-OH bonds are basic to interpret this correlation.
Surface Structure of A Liquid Perfluoropolyether Examined by Reactive Ion/Surface Scattering
Authors: Pradeep T. , Miller S. A. , Rohrs H. W. , Feng B. , Cooks R. G.
Published: April 2011

This study shows that reactive ion/surface collisions can provide information on the surface structure of molecular systems. The microscopic structures of perfluorinated polyether (PFPE) liquid surfaces are characterized by ion/surface collision experiments in a mass spectrometer and the results are compared to those obtained with a fluorinated self-assembled monolayer (F-SAM) surface. Low energy (< 100 eV) beams of W+ and W(CO)6+ ions are used for surface-induced dissociation (SID) and ion/surface reactive scattering, while Xe+ and Kr+ beams are used for chemical sputtering experiments. Both the PFPE and F-SAM surfaces show similar SID fragments while reactions with W+ and W(CO)6+ lead to the scattered metal ion with multiple fluorine atoms attached. The main peaks in chemical sputtering spectra are similar for both surfaces as well. Both hydrogen probe beams and chemical sputtering confirm that the liquid PFPE surface is nearly free of impurities. Our results on both surfaces also suggest that the CF3 group of the monomer units is most likely projected outward from the bulk of the liquid surface.
Low Dielectric Constant Thermosetting Resins For Microelectronics
Authors: Buckley Leonard J. , Snow Arthur , Griffith James , Hu Henry S.-W. , Ray Mark
Published: April 2011

Material technology for future microelectronics will require advances in all facets of materials and processing. Low dielectric constant resins that exhibit facile processing and good thermal and mechanical behavior represent one area of needed research and development. The dielectric constant must be lower than that of amorphous silicon dioxide and possess the right properties for integration with future metallurgies such as copper. Several thermoset resins that were predicted to possess the necessary characteristics have been synthesized and studied. These include a copolymer of 1,3,5-tris(2-allyloxy-hexafluoro-2-propyl) benzene with polymethylhydrosiloxane and several cyanate ester resins. Thermal gravimetric analysis indicated significant degradation between 300 and 400 degrees C depending upon the resin. Dielectric constants were measured up to 40 GHz and ranged from 2.25 to 2.75. Compatibility with copper multilevel processing was addressed. The processability of the dielectric resins was investigated to address the integration issues associated with the fabrication process.
Dielectric Measurements On Printed-Wiring And Circuit Boards, Thin Films, And Substrates: An Overview
Authors: Baker-Jarvis James , Jones Chriss A.
Published: April 2011

A review of the most common methods of permittivity measurements on thin films, printed-wiring and circuit boards, and substrates is presented. Transmission-line techniques, coaxial apertures, open resonators, surface-wave modes, and dielectric resonators methods are examined. The frequency range of applicability and typical uncertainties associated with the methods are summarized.
Digital Optical Imaging Of Benzocyclobutene (Bcb) Thin Films On Silicon Wafers
Authors: DeVries Robert A. , Shick Reed A. , Johnson Bethany K.
Published: April 2011

A practical, low-cost research system for the fluorescent optical imaging of BCB (DVS-bisBCB) thin films has been used for the first time to evaluate coating quality on spin coated silicon wafers. In general, DVS-bisBCB thin films are easily produced defect free with a high degree of planarization. Various features of the coating are enhanced visually by the fluorescence making detection, digital storage, and quantification easier. Examples of features found in defective coatings made intentionally by a process to generate several common thin film defects are variations in film thickness, foreign particles, pinholes, and residual polymer in vias. The fluorescent bands of the normally transparent resin are easily excited in the near UV with a mercury lamp, causing a semi-opaque visible emission which could be observed by conventional imaging hardware. The BCB fluorescent quantum yield, or efficiency, is similar to fluorescent dyes so that only a small amount of BCB need be present in a substrate to allow optical inspection.

This strong fluorescent property of DVS-bisBCB polymer, not possessed by many polyimide resins, could reduce labor costs of manual inspections and improve multichip module (MCM) processing yields. This digital imaging technique has potential for further development as a cost-effective automated optical inspection (AOI) method.
Integration Of BPDA-PDA Polyimide With Two Levels Of Al(Cu) Interconnects
Authors: Wetzel J. T. , Lii Y. T. , Filipiak S. M. , Nguyen B.-Y. , Travis E. O. , Fiordalice R. W. , Winkler M. E. , Lee C. C. , Peschke J.
Published: April 2011

As device geometries continue to scale down, a larger portion of the circuit delay is contributed by interconnects, and the majority of this delay is due to capacitive loading. The replacement of plasma-deposited SiO2 as an intermetal dielectric with an insulator of lower dielectric constant can provide performance improvement through the reduction of capacitance.

A commercially available polyimide, BiPhenylene DiAnhydride – Phenylene DiAmine, BPDA-PDA, with an out-of-plane dielectric constant 3.0, is evaluated by integration with AI(Cu) in a double level metal, BiCMOS 4MB SRAM device, with 0.5μm groundrules. Process challenges unique to integration of an organic rather than inorganic insulator are described and experimental features concerning process integration, particularly via etch, Al(Cu) deposition, adhesion and moisture management are presented.
Investigations of The Low Dielectric Constant Fluorinated Polyimide for Use as The Interlayer Dielectric in ULSI
Authors: Lee Y.K. , Murarka S.P. , Jeng S. -P. , Auman B.
Published: April 2011

Low dielectric constant interlayer dielectric ( ILD) materials are required for the advanced silicon integrated electronics such as those in the ULSI era[3, 10]. We have investigated several such materials. In this paper the results of our investigations of the materials and electrical properties, processing ( to form ILD ), and applicability of a DuPont fluorinated polyimide are described and discussed. Weight loss, FTIR, and ellipsometric measurements have been carried out. The DuPont fluorinated polyimide thin film was observed to be thermally stable up to 450°C, which is monitored by using dynamic TGA with a ramping rate of 10°C/min or 5°C/min in N2 Ambient. Also MIPOS capacitor characterization, effect of temperature and moisture on these properties have been determined. The dielectric constant was observed to be as low as 2.5 and the refractive index is around 1.63, both being stable up to 450°C. However, the DuPont Fluorinated polyimide exhibited a flat band voltage shift on C-V curve after 400°C annealing in vacuum environments for 1 hr. Compatibility with copper as the interconnecting metal has been determined and discussed[8]. It is concluded that this polymer is a possible candidate for ILD application.
Novel Photocurable Materials For Spinon Dielectric Films
Authors: Crivello James V.
Published: April 2011

Poly(indanes) can be prepared by the photoinduced cationic polymerization of a variety of diisopropenyl aromatic monomers. Typically, polymerization proceeds rapidly under UV irradiation catalyzed by diaryliodonium salt photoinitiators to give hard, transparent films. Investigations have shown that the polymerization proceeds mainly by a dimerization followed by a ringclosure process to yield indane structures along the polymer backbone. Film-forming mixtures containing either pure monomer or mixtures of monomers together with a poly(indane) prepolymer can be spin coated onto silicon wafers. Measurements made on the photopolymerized coatings give low dielectric constants. These coatings also display excellent thermal stability.
Epitaxial Growth of Metastable Facf—Centered Cubic Co on (111)Si with A Thin Intermediate Cu Layer
Authors: Liu C.S. , Chen L.J.
Published: April 2011

Metastable face—centered cubic (fcc) Co was grown epitaxially on (111)Si with an intermediate Cu layer in an ultrahigh vacuum chamber at room temperature. The metastable fcc—Co was grown to extend to a thickness of 30 nm. Polycrystalline and epitaxial hexagonal close—packed (hcp) Co was grown on (111)Si without and with 3 nm or thicker intermediate Cu layer, respectively. The key to the successful growth of fcc—Co is to deposit Co directly onto a thin (2 nm or thinner) interface compound (—Cu, which is of hcp structure and consisting of 11.2 to 14.0 at.% Si. The growth of the metastable phase is attributed to the attainment of an appropriate electron/atomratio at the interface to favor the formation of the fcc—Co.
Structural Characterisation of Fe-Cu Multilayers of Differing Fe Thicknesses Using Transmission Electron Microscopy
Authors: Lloyd S. J. , Somekh R. E. , Stobbs W. M.
Published: April 2011

In-plane and out-of-plane lattice parameters were measured in a series of coherent Fe-Cu multilayers using non-axial high resolution electron microscopy (HREM). The results indicate that the multilayers are tetragonally distorted with the magnitude of the distortion varying with the thickness of the Fe component. These distortions preclude an understanding of the multilayer structure in terms of conventional elasticity theory. The breakdown of epitaxy for thicker Fe layers was also investigated and it was found that the b.c.c. Fe grew with [110] parallel to [001] of the coherent f.c.c. multilayer.
The Magneto-Optical Quantum Size Effect in bcc-Fe(001) and (110) Ultrathin Films
Authors: Suzuki Y. , Katayama T. , Geerts W. , Bruno P. , Sawada H.
Published: April 2011

Recently, the oscillation of the magneto-optical effect with respect to the ferromagnetic layer thickness was observed for bcc-Fe(001) ultrathin films. The oscillation periods have been explained by the theory concerning the formation of quantum well states in the ferromagnetic layer. In this paper, a physical picture how the electron confinement produces the quantum size effect of the magneto-optical responses is introduced, and experimental results on the magnetooptical effects of the bcc-Fe films of different orientations are presented. The (001) oriented films show clear oscillation. On the other hand, the (110) oriented films does not show any oscillation. The reason is discussed from the band structure and growth modes.
Magnetic Phase Transition in the Csci Fesi Spacer in Fe/FeSi Multilayers
Authors: Dekoster J. , Vantomme A. , Degroote S. , Moons R. , Langouche G.
Published: April 2011

We report the formation of the CsCI FeSi phase in Fe/FeSi multilayers with constant Fe thickness and varying FeSi layer thickness. The crystallographic and magnetic properties of this metastable FeSi phase are determined in thick (62 nm) epitaxial silicide layers with ion channeling, X-ray diffraction and Mossbauer spectroscopy measurements which clearly show that the CsCl phase becomes increasingly magnetic upon cooling down to 4.2 K. These results indicate that the transition from antiferromagnetic to ferromagnetic coupling observed at low temperatures in such multilayers is controlled by a magnetic phase transition in the FeSi spacer layer.
Fabrication and Structural and Optical Properties of Amorphous Si/SiO2 Superlattices on (100) Si
Authors: Baribeau J.-M. , Lockwood D.J. , Lu Z.-H.
Published: April 2011

We report the growth and characterization of amorphous Si (a-Si)/SiO2 superlattices on (100) Si. The a-Si layers (thickness varying from 1 to 10 nm) were vacuum-deposited at room temperature by molecular beam epitaxy while the SiO2 layers (1 nm) were grown by an ex-situ UV-ozone treatment. This procedure was repeated six times to produce periodic multilayer structures. The chemical modulation of these structures was confirmed by transmission electron microscopy and depth profiling using Auger electron spectroscopy. X-ray specular reflectivity showed that the structures have a well defined periodicity. The a-Si layers have a density approaching (>95 %) that of c-Si and an interfacial roughness that increases with the a-Si layer thickness. The Raman spectrum from the Si layers of all samples shows broad peaks near 150, 310 and 470 cm−1 that are typical of a-Si. On annealing at high temperatures, the three Raman bands decrease in intensity, while the 470 cm−1 band also shifts to higher frequency and becomes narrower. After annealing for 30 s at 1100 °C, the a-Si bands are weak and the 470 cm−1 band is merging with the c-Si 520 cm−1 line, indicating that partial re-crystallization of the Si layers has occurred. The room temperature light emission properties of these nanostructures in the green to red wavelength region is reported. The luminescence shifts to longer wavelength with increasing a-Si layer thickness, consistent with a quantum confinement mechanism.
Structure and Novel Electrical Effects in A-Si:H Based Multilayers Containing Discontinuous Metal Sublayers
Authors: Panckow A.N. , DrÜsedau T.P. , Klabunde F. , SchrÖder B.
Published: April 2011

Multilayer systems (MLS) were prepared by alternating deposition of hydrogenated amorphous silicon (a-Si:H) and transition metal (Mo,Ti,V) sublayers. The thickness of the a-Si:H sublayers deposited by either dc-magnetron sputtering or rf-glow discharge deposition is in the range from 65 nm to 85 nm. The nanodisperse structure of the metal sublayers with a nominal thickness below 4 nm was verified by transmission electron microscopy, scanning force microscopy and spectroscopic ellipsometry. The discontinuous metal sublayers were formed by chains of metal clusters. The appearance of novel electrical phenomena was observed. These are a reversible switching effect in conduction and giant current fluctuations. The validity of the T−1/2 -law for the temperature dependent conductivity was confirmed. In this study explanations for some of these effects are given considering the structural peculiarities of the nanodisperse multilayers.
In Situ Stress Measurements of Co-Based Multilayer Films
Authors: Kim Young-Suk , Shin Sung-Chul
Published: April 2011

We have constructed an apparatus for in situ measurement of stress of the film prepared by sputtering using an optical non-contact displacement detector. A change of the gap distance between the detector and the substrate, caused by stress of a deposited film, was detected by a corresponding change of the reflectivity. The sensitivity of the displacement detector was 5.9 µV/Å and thus, it was turned out to be good enough to detect stress caused by deposition of a monoatomic layer. The apparatus was applied to in situ stress measurements of Co/X(X=Pd or Pt) multilayer thin films prepared on the glass substrates by dc magnetron sputtering. At the very beginning of the deposition, both Co and X sublayers have subjected to their own intrinsic stresses. However, when the film was thicker than about 100 Å, constant tensile stress in the Co sublayer and compressive stress in the X sublayer were observed, which is believed to be related to a lattice mismatch between the matching planes of Co and X.
Role of Crystallinity In Roughness of Ru/c Multilayers -An Amorphization Study
Authors: Walton C. C. , Kortright J. B.
Published: April 2011

Single Ru films and Ru/C multilayers were sputtered on silicon substrates, in 2.5 mtorr Ar/O2 atmospheres with oxygen mole fractions from 0 to 5%. Reflectivities of the films were measured near 100eV and at 8048eV (CuKα). Critical angle measurements of the single films showed a loss of optical density consistent with full oxidation in the Ar/5%O2 sputtering atmosphere. Soft x-ray reflectivity of the multilayers was reduced from 24% with no added oxygen to < 1% for Ar/5%O2. Diffraction of CuKα x-rays and plan-view TEM showed that the added oxygen reduced Ru crystal size in all films but did not fully amorphize the Ru layers.
Thermal Degradation of Tantalum-Nickel Thin Film Couples
Authors: Tabacniks M. H. , Kellock A.J. , Baglin J.E.E. , Coffey K.R. , Howard J.K. , Parker M.A.
Published: April 2011

Multilayered metal films including such couples as Ta-Permalloy (Ni80Fe20) play a key role in magnetic recording sensors, where it is important to preserve the integrity of the thin permalloy layer under thermal conditions during processing and subsequent service. Earlier work1 has indicated a fast grain boundary diffusion of Ta in Ni films at temperatures as low as 250°C. In this paper, we report measurements of the kinetics of this diffusion, in the temperature range 300–400°C. For this work, layered Ni/Ta systems were prepared under controlled conditions, annealed in a helium-flow furnace, and characterized by RBS, AES, XRD and SEM. The possible consequences of diffusion on magnetic performance are also discussed.
Characterization of The Nucleation and Growth Process of CVD-W On TiN Substrates
Authors: Nanda Arun K. , Merchant Sailesh M. , Roy Pradip K.
Published: April 2011

The nucleation and growth characteristics of CVD-W on Ti/TiN barrier layers with SiH4 and H2 reduction chemistries are presented. In particular, the reaction between WF6 (precursor used for depositing W) and the underlying Ti of the barrier stack was studied to better understand the chemistry of ‘volcano’ formation - a phenomena that causes severe defects in the deposited W film. Ti/TiN processing parameters and stack thicknesses were varied, along with the CVD-W deposition chemistry (gas flows, pressures, temperatures and times), to evaluate film properties and characteristics after SiH4 passivation, nucleation and full W plug deposition. The analysis was augmented with cross-sectional Scanning Electron Microscopy (SEM) on short-loop testers and films were characterized using Rutherford Backscattering Spectroscopy (RBS), Secondary Ion Mass Spectroscopy (SIMS), X-ray Diffraction (XRD) and Auger Electron Spectroscopy (AES) techniques. Several processing conditions are recommended for ‘volcano-free’ and ‘defect-free’ CVD-W films.
The Effects of Thermal Processing on Interfacial Microstructure for Thin Multilayered Metal Ohmic Contacts to p+-AlGaAs
Authors: Cole M.W. , Han W.Y. , Jones K.A.
Published: April 2011

Interfacial microstructure and phase composition of PtTiGePd ohmic contacts to heavily C doped AlGaAs were investigated as a function of annealing temperature. Results of the material analyses were used to explain the specific contact resistances measured for each thermal treatment. Evidence of interdiffusion and compound formation between AIGaAs and Pd was visible in a Ga rich Pd-Ga-As reaction zone prior to heat treatment. This phase is critical for the formation of Ga vacancies, which upon heating are occupied by in-diffusing Ge. As the annealing temperature was elevated, from 530 - 600°C, As began to out-diffuse. This As out-diffusion, which is critical to the formation of good p-type ohmic contacts, contributed to the creation and development of the two phase TiAs/Pd12Ga2Ge5 interfacial region overlying the AlGaAs substrate. In response to the enhanced As out-diffusion at 600°C, the interfacial region became laterally continuous, compositionally uniform, and the specific contact resistance achieved its minimum value. Athigher annealing temperatures, ∼650°C, the electrical measurements degraded in response to intensive chemical diffusion and development of a broad, non-uniform multi-phased interfacial region.
Use of A New High Speed Acrylate Deposition Process to Make Novel Multilayer Structures
Authors: Shaw David G. , Langlois Marc G.
Published: April 2011

A new process has been developed to deposit acrylate thin films at speeds of 1500 ft/minute or higher. These films range in thickness from a few hundred Angstroms to a fewmicrons and are uniform in thickness to within 5%. They can vary in refractive index from 1.35 to 1.60 and have mechanical properties from very hard and abrasion resistantto very soft and flexible.

The acrylate deposition process was originally developed for multilayer acrylate/aluminum capacitors where over 10,000 layer structures were produced[l]. The process is compatible with other vapor deposition processes such as sputtering, evaporation, and CVD. Both processes can take place at the same time in the same vacuum chamber toproduce various multilayer structures.

This paper will discuss some of the features of this process and the associated equipment. It will present examples of the wide range of acrylate/acrylate, acrylate/metal, and acrylate/inorganic material structures that can be made. It will discuss various applications for these structures.
Large-Area Pulsed Laser Deposition (PLD)
Authors: Dietsc R. , Holzs Th. , Mai H. , Panzner M. , Völlmar S.
Published: April 2011

PLD of uniform thin films on 4”-wafers has been realized by the integration of a PLD-source into a commercial MBE-system. Thickness homogeneity over the total substrate area is obtained by precise spatial control of the plasma plumes excited simultaneously at 4 adjacent target locations. Computer controlled motion of a cylindrical target with respect to the stationary focal spots of the laser beams, has to provide (a) a suitable deflection of the plume axis and (b) a uniform target erosion. Process control was investigated by computer simulations. The efficiency of the developed technique for large area coating is illustrated by the preparation of DLC thin film specimens and their ellipsometric characterization
Diffusion in Metallic Multilayers
Authors: Greer A. L.
Published: April 2011

The use of metallic multilayers for diffusion measurements is reviewed. Experiments on epitaxial Ag/Au multilayers show that microstructural evolution can affect the measurements, but that nonetheless accurate determinations of lattice interdiffusivity can be made down to exceptionally low temperatures. Experiments on amorphous Ni-Zr multilayers show that with diffusional symmetry there can significant diffusion-induced stresses. Analysis of the interdiffusion kinetics as influenced by stress permits the determination of a range of materials parameters, including the diffusivities of individual species and plastic flow behaviour.
The mechanical Properties of CVD Diamond Films, and Diamond Coated Fibres and Wires
Authors: Nicholson E D , Field J E , Partridge P G , Ashfold M N R
Published: April 2011

Two areas of thin film property measurement are addressed. The first is that of flat films, either on a substrate or free-standing. The film properties only are of interest. Therefore, when the film remains attached to a substrate during testing, an appropriate analysis is used to subtract the effect of the substrate. The films under test are prospective protective coatings and ‘window’ materials for infrared applications, namely CVD diamond (Hot filament Assisted, HFACVD and Microwave plasma assisted, MPACVD) and Germanium carbide (Ge:C). The mechanical properties under investigation are the Young's modulus and the internal film stress.

In the second case the substrates are small diameter fibres and wires coated with CVD diamond. The mechanical properties measured were composite, containing contributions from both the substrate and the film. These coated fibres and wires, have possible applications as reinforcement phases in the production of composites. They are silicon carbide (SiC) and Tungsten (W) of diameters varying between 10 and 125μm. A technique has been developed to measure the Young's modulus of individual coated fibres.
Measurement of Stress In CVD Diamond Films
Authors: Gray K. J. , Olson J. M. , Windischmann H.
Published: April 2011

Measurement of stress in CVD diamond by Raman spectroscopy and by the substrate curvature method is discussed. A correction to the commonly applied Stoney thin-film equation for the substrate curvature technique is presented for coatings with a large stiffness mismatch with the substrate. Stress measurement by Raman spectroscopy is complicated by factors such as temperature, domain size, non-hydrostatic stress, and degeneracy lifting. With proper consideration of these complicating factors, substrate curvature and Raman spectroscopy stress measurement results can be reconciled with the predictions based on thermal modeling.
Brazing Characteristics of Diamond on Various Substrates With Differient Brazing Alloys
Authors: Kuo Cheng Tzu , Lin Chii Ruey , Lien How Min
Published: April 2011

The commercial diamond grits and the diamond films deposited by a microwave plasma chemical vapor deposition system were used to study the wetting characteristics of few commercial brazing alloys, e.g., Cu, Ni, Ag-Cu-Zn-Cd-Ni and Ag-Cu-In. The substrates for brazing experiments include AISI-304 stainless steel, AISI-1045 steel and cemented WC insert. The results shows that the wettability of the brazing alloys and the bonding strength between diamond and substrate are strongly influenced by the compositions of the brazing alloys and the surface conditions of diamond and substrate. The wettability of Cu with diamond grit or diamond film depends on the brazing substrate, and is in order of AISI-304 > WC > AISI-1045. The brazing alloys with Cu or Ag as the main component often show a poor brazing strength for diamond/plain carbon steel or diamond/WC.