bluuebunny/crossref_metadata_2025 huggingface dataset:
The Effect of Layer Thickness on the Reaction Kinetics of Nickel/Silicon Multilayer Films
Authors: Clevenger L. A. , Thompson C. V. , Cammarata R. C. , Tu K. N.
Published: March 2011

Differential Scanning Calorimetry (DSC) and Debye-Scherrer X-ray diffraction have been used to characterize silicide formation in nickel/amorphous-silicon multilayer films. Two different Ni:Si layer thickness ratios were investigated, 3:11 and 1:1. Films with layer thickness ratio of 3:11 first formed Ni2Si followed by NiSi at a temperature 25°C higher. Multilayer films with 1:1 thickness ratios formed only Ni2Si. Activation energies for these reaction were determined and found to be in agreement with previous results on bilayer films. The temperature at which Ni 2Si formation was complete in the 1:1 films was found to decrease with decreasing layer thickness. Analysis of this phenomenon allowed determination of the interdiffusivity during silicide formation, also in agreement with previous results. Films with 1:1 layer thickness ratios and layer thickness of 125 Å or less were found to sometimes undergo explosive silicidation. This presumably occurs because the rate of heat generation at the reacting interfaces exceeds the rate of heat dissipation.
Fabrication and Evaluation of Transmissive Multilayer Optics for 8keVX Rays
Authors: Bionta R. M. , Jankowski A. F. , Makowiecki D. M.
Published: March 2011

We have made and tested several sliced multilayer structures which can function as transmissive x-ray optical elements (diffraction gratings, zone plates, and phase gratings) at 8 keV. Our automated multilayer sputtering system is optimized to sputter layers of arbitrary thickness for very large total deposits at high deposition rates. Diffraction patterns produced by the multilayer devices closely match theoretical predictions. Such transmissive optics have the potential for wide application in high resolution microscope and spectrometer systems.
Mon-Tin Superconducting Artificial Superstructure Film
Authors: Kawaguchi Kenji , Shin Shigemitsu
Published: March 2011

We succeeded in synthesizing MoN-TiN superconducting artificial superstructure film (SASF). The structure of MoN layers is estimated to be γ-Mo2 N. The behavior of Tc in SASFs is recognized by a proximity effect using adjustable parameters of bulk Tc. Calculated parameters are, however, different from Tc of single layered films.
Multilayered Interconnections for VLSI
Authors: Gardner Donald S. , Saraswat Krishna
Published: March 2011

Interconnections are predicted to become the limit in performance and reliability at submicron dimensions. Layered structures are one possible solution to the problems of electromigration and hillocks. Aluminum alloys can improve the properties of pure aluminum but with a consistent increase in resistivity due to lattice distortions introduced by the alloy in solid solution. The rise in resistivity is minimal in layered films because aluminum layers act as parallel conductors. Titanium is the most effective refractory metal for eliminating hillocks in layered films; however vanadium, tantalum, and tungsten also reduce hillocks to a manageable level although high resistivity, the inability to dry etch, or lateral hillocks can become a problem. Layered films of aluminum with TiSi2 encounter problems with hillocks. These differences are partially explained by the increased strength of the aluminide TiA13 that forms compared to the other compounds. Barrier metals are needed for aluminum layered with refractory metals because of the formation of ternary compounds, and several metals have proven to be satisfactory. Such barriers, however, are required for even aluminum at submicron dimensions for stable low-resistivity contacts.
MBE Growth of Compositionally Modulated Ceramics
Authors: Mckee R. A. , List F. A. , Walker F. J.
Published: March 2011

An ultra high vacuum system fitted with thermal effusion cells that heat 20cc of material to temperatures as high as 2000 °C is being used to synthesize thin film and multilayer ceramics from their constituent elements. A molecular source for oxygen used in conjunction with these effusion cells allows oxides of Al, Ti, Cu, and Y to be grown with compositional modulation controlling growth rate and stoichiometry.
Characterization of Interfacial Roughness in Semiconductor Heterostructures by X-Ray Reflectivity
Authors: Krol A. , Sher C. J. , Resat H. , Woronick S. C. , Ng W. , Kao Y. H. , Chang L. L. , Hong J. M.
Published: March 2011

The reflection of monochromatic x-rays by a layered heterostructure can be utilized as a nondestructive probe to obtain information on the interfacial roughness in the material. Interference between x-rays reflected from the top surface and the interfaces can give rise to pronounced oscillations in the reflectivity as a function of the grazing incidence angle. We have made use of this technique to investigate the interfacial roughness in semiconductor heterostructures grown by molecular beam epitaxy.
Forces on Dislocations in Multilayer Structures
Authors: Kamat Somir V. , Hirth J. P. , Carnahan B.
Published: March 2011

In multilayer structures, dislocation forces that arise from coherency strains are well understood in both the isotropic and anisotropic elastic cases. Image forces produced by elastic inhomogeneity have also been developed for single layers surrounded by extended phases. Image forces for the multilayers are shown to reduce to the simpler single embedded layer case to a good approximation. Image forces are shown to lead to a “stand-off” position of interface dislocations from the interface, with several implications for the properties of multilayer structures.
Structural Perfection of in GaAs/InP Superlattices Grown by Gas Source Molecular Beam Epitaxy: A High-Resolution X-Ray Diffraction Study
Authors: Vandenberg J. M. , Panish M. B. , Hamm R. A.
Published: March 2011

High-resolution X-ray diffraction (HRXRD) studies have been cardied out to determine the structural perfection and periodicity for a number of high-quality InGaAsfInP superlattices grown by gas source molecular beam epitaxy. X-ray scans were carried out with a compact four-crystal monochromator resulting in a resolution of one molecular layer (∼3,Å), which enables one to observe very small variations in the periodic structure. Sharp and strong higher-order satellite reflections in the XRD profiles were observed indicating smooth interfaces with well-defined modulated structures. Excellent computer simulated fits of the X-ray satellite pattern could be generated based on a kinematical XRD step model which assumes ideally sharp interfaces, and periodic structural parameters such as the strain in the well could be extracted. Our results3 demonstrate that HRXRD in conjunction with the kinematical step model is a very sensitive method to assess periodic structural modifications in superlattices as a result of the precise growth conditions in the gas source MBE system.
From Electronic Structure To Thermodynamics
Authors: Bachelet Giovanni B.
Published: March 2011

A simple way to extend the remarkable results of Density Functional calculations to finite-temperature properties of materials is the quasi-harmonic theory of Lattice Dynamics. In this framework a thermodynamically consistent theory needs the complete phonon spectrum for a large periodic system (30–100 atoms/cell) at many different volumes, which poses severe practical limitations. In this paper I present the application to a semiconducting system of a method recently proposed by Bachelet and De Lorenzi to overcome these limitations. Based on low-temperature Molecular-Dynamics trajectories (now possible from first principles for semiconducting systems according to the method of Car and Parrinello), the method is shown to provide accurate dynamical matrices for an 8-atom silicon supercell. Such a successful, preliminary test, together with the fact that for larger and/or lower-symmetry systems the computational effort required by the “trajectory approach” is lower than traditional frozen-phonon or force-constant techniques, suggests its use in the determination of dynamical matrices of larger defect or amorphous systems, and thus in the study of their thermodynamics from first principles.
Electrical Characterisation of Shallow Pre-Amorphised +n junctions in silicon
Authors: Brotherton S. D. , Ayres J. R. , Clegg J. B. , Goldsmith B. J.
Published: March 2011

An examination of Si+ pre-amorphised p+n structures as a function of Si+ implantation energy and solid phase epitaxial regrowth temperature has revealed three different classes of defect all of which may influence the characteristics of the junction. They are point defects responsible for high concentrations of deep level donors, and interstitial dislocation loops both causing leakage current degradation, and excess silicon interstitials leading to enhanced junction movement.
Effects of Carbon Concentration Upon Oxygen Precipitation in Cz Si
Authors: Hahn S. , Arst M. , Ritz K. N. , Shatas S. , Stein H. J. , Rek Z. U. , Tiller W. A.
Published: March 2011

Effects of high carbon concentration upon oxygen precipitate formation in Cz silicon have been investigated by combining various furnace and rapid thermal annneals. Even though oxide precipitate density increases with increasing carbon levels, Cs, synchrotron radiation section topographs of processed high carbon content wafers (Cs ∼ 4ppma) exhibit Pendellosung fringes, indicating a strain free bulk state. Our optical microscopic data have also shown very few defect etch features inside the bulk. A model based upon a direct coupling of both SiO2 and Si-C complex formation reactions is used to explain rather unique oxygen precipitation characteristics in the high carbon content Cz Si materials.
Microscopic Analysis of the Behavior of Interstitial and Precipitated Oxygen During Intrinsic Gettering in Si
Authors: Sun Qing , Lagowski J. , Gatos H. C.
Published: March 2011

We have used FTIR spectrum processing to analyze the behavior of interstitial and precipitated oxygen during the intrinsic gettering process. The kinetics of precipitation and the microscopic growth characteristics of precipitates were compared with a theoretical model based on diffusion controlled precipitation process. The annealing time dependence of precipitate size has been found to follow the relation of r = tn with n = 0.7.
Oxygen Aggregation Phenomena in Silicon
Authors: Newman Ronald C.
Published: March 2011

Oxygen precipitation in Czochralski silicon heated in the range 400–1050°C is reviewed. For T≥525° C, Si02 particles form at the normal diffusion rate and there is generation of self-interstitials. At the lower temperatures, the existence of the interfacial energy causes an apparent increase in the solid solubility as the agglomerates become very small: at 525° C they contain only an estimated 20–50 atoms. A critical analysis s then presented of possible oxygen aggregation reactions at even lower temperatures when thermal donors are generated. It is not yet possible to reconcile the kinetics of these two processes, even if self-interstitials and/or vacancy reactions are included. There is no evidence for enhanced diffusion of isolated oxygen atoms except as a transient process occurring during the relaxation of stress-induced dichroism. Oxygen aggregation at 450 ° C appears to be limited by the formation of dimers with an activation energy of 2.5eV, while thermal donors form with an activation energy of 1.7eV.
Effects in Silicon Explained by Atomic Hydrogen
Authors: Schnegg A. , Prigge H. , Grundner M. , Hahn P. O. , Jacob H.
Published: March 2011

The chemomechanical polishing mechanism is described as a corrosive attack of water forming Si-H and Si-OH groups. By adding ammonia or amines to the slurry we observe an irlfease of the resistivity corresponding to a neutralization of up to 1 × 1017 acceptor atoms cm−3 in the case of p-type silicon, whereas n-type silicon can show a slight reduction in resistivity due to the neutralization of the residual acceptor concentration.

SIMS measurements show the presence of hydrogen in the bulk. Using deuterium instead of hydrogen, a correlation could be established between the deuterium content of the wafer, measured by the effusion technique, and the degree of the acceptor compensation.

As can be shown by resistivity and C/V-measurements, under the conditions of polishing the supposed inactivator hydrogen migrates to a distance finally corresponding to the thickness of a wafer. This is contrary to the comm on method of plasma treatment, where a damaged silicon layer is supposed to act as a barrier to the hydrogen diffusion. Differences in the IR spectra can be explained this way.

Crystal imperfections in the bulk and on the surface influences the migration of hydrogen essentially.
Carrier Removal in n+ GaAs:Si by Proton Implantation. a Spectroscopic Study
Authors: Pajot B. , Chevallier J. , Chaumont A. , Azoulay R.
Published: March 2011

Protons and deuterons have been implanted in n+ GaAs:Si epilayers. Localized vibrational modes (LVM's) associated to H- and D-related defects are observed in the as-implanted samples and they account presumably for the carrier removal in the compensated region, but a small concentration of Si-H passivating centers is already present. LVM spectroscopy shows that after a 200° C annealing, passivation predominates over compensation while a 400° C annealing extends partial passivation throughout the layer.
Endor Spectroscopy on Deep Level Defects in Gaas
Authors: Spaeth J.-M. , Gorger A. , Hofmann D. M. , Meyer B. K.
Published: March 2011

With optically detected electron spin resonance (ODESR) and electron nuclear double resonance (ODENDOR) the following deep level defects in s.i. LEC-grown GaAs were investigated: EL2 defects in undoped GaAs and VGa2+ and VGa3+ defects in V-doped GaAs. This paper summarizes the major results: (i) the double donor defect EL2 in an (AsGa-Asi+) pair defect, which is distributed rather homogeneously across an as-grown wafer. After inverted thermal conversion treatment it is destroyed, and 3 new paramagnetic defects appear. EL2 is recovered after annealing at ca. 800 °C, while the 3 new defects disappear. (ii) A new ESR spectrum due to VGa2+ was measured. It is shown for the first time for a 3dn impurity in semiconductors that VGa3+(3d3)is in a low spin state (S = 1/2) in accordance with recent theoretical predictions. A deep level defect at Ev + (0.2–0.4) eV is discovered, which is probably the defect needed for explaining the s.i. properties of V-doped GaAs.
Space and Time Resolved Photoluminescence of Defects at Dislocations in In-Alloyed GaAs Substrate Material
Authors: Johnson Matthew B. , Hunter A. T. , McGill T. C.
Published: March 2011

We report a study of dislocations in In-alloyed GaAs substrate material using space and time resolved photoluminescence (PL). PL intensity maps show that an isolated dislocation cluster is in the center of a dark region with a 50μm radius surrounded by a bright region with an outer radius of 150μm. Lifetime measurements were made in the bright and dark regions. Values as long as 3.5 ns and as short as 250 psec were observed in adjacent bright and dark regions. These measurements indicate that the PL intensity contrast is explained by lifetime variations in these features. This supports the view that the dislocation cluster acts as a source and sink for defects which govern the lifetime in the surrounding material. Temperature dependence of the lifetime indicates two different defects may be involved. Both of these produce deep levels, neither one of which is EL2. A surface passivation technique is used to show that surface recombination is not important to the PL intensity contrast.
Vacancy Diffusion at Polysilicon Encapsulated GaAs Surfaces
Authors: Kavanagh K. L. , Magee C. W. , Sheets J.
Published: March 2011

The diffusivity of Si and P in GaAs encapsulated with heavily-doped polysilicon (poly-Si) is correlated to the flux of Ga and As diffusing from the substrate into the encapsulant. A model based on the diffusion of vacancies into the GaAs is proposed and used to simulate the data.
Site Occupation of Implanted Te in Gaas As a Function of Implantation Dose
Authors: Langouche G. , Schroyen D. , Bemelmans H. , Van Rossum M. , Deraedt W. , de Potter M.
Published: March 2011

Te atoms were implanted in GaAs with doses ranging from 1013 to 1016 atoms/cm2, and annealed with the rapid thermal annealing technique. The samples were studied by Mössbauer Spectroscopy, Rutherford Backscattering Spectroscopy – Channeling, and the Van der Pauw-method. While at the lowest implantation dose an unperturbed substitutional site is observed at all annealing temperatures, at the highest implantation dose a strong deviation from a central position in an unperturbed configuration is observed at all temperatures. At the intermediate doses a high degree of substitutionality is observed between annealing temperatures of 200°C and 500°C only.
Pressure-dependent DLTS Experiments on Si-DOPED AlGaAs
Authors: Farmer John W. , Hjalmarson Harold P. , Samara G. A.
Published: March 2011

Pressure dependent Deep Level Transient Spectroscopy (DLTS) experiments are used to measure the properties of the deep donors (DX-centers) responsible for the persistent photoconductivity effect in Si-doped AlGaAs. The sample dependence of the DLTS spectra shows evidence for a defect complex involved in the DX-center.
Identification of Interstitial Carbon Related Defects in Silicon
Authors: Benton J. L. , Asom M. T. , Sauer R. , Kimerling L. C.
Published: March 2011

DLTS measurements are used to detect and identify the interstitial related defects in n-type silicon. The materials dependences of the reactions of the [E(0.12), H(O.27)], [ME(0.30), ME(0.29), ME(0.23), ME(0.21)], ]ME(0.10), ME(0.17)] and [H(0.36)] spectral features lead to their identification as representing the two charge states of Ci, the multistable configurations of Ps-Ci, the bistable Cs-Sii-Cs, and the Ci-Oi defects, respectively. The branching ratios for the reactions of interstitial carbon with the impurities are given.
Photoassisted Deposition of Silicon Dioxide from Silane and Nitrogen Dioxide
Authors: Marks Jeffrey , Bowman Robert C. , Robertson Ruby E.
Published: March 2011

Three new reactions for depositing silicon dioxide at low temperatures using vacuum ultraviolet and ultraviolet radiation to initiate a reaction between silane and nitrogen dioxide have been developed. The optical and electrical properties of these films are reported. The effect of ion implantation on the infrared spectra of oxides grown by vacuum ultraviolet irradiation is also presented.
The Electrical Properties of Silicon Oxide Deposited By Remote Plasma Enhanced Chemical Vapor Deposition (Rpecvd).
Authors: Kim Sang S. , Tsu D. V. , Lucovsky G.
Published: March 2011

We have constructed an Ultra High Vacuum (UHV) multichamber system and have deposited ‘gate quality’ silicon dioxide by the remote plasma enhanced chemical vapor deposition (Remote PECVD) process at low substrate temperatures (Ts ≤400 °C). Native oxides and other surface contaminants are removed under ultra high vacuum (UHV) conditions and the character of the semiconductor surface is determined prior to film deposition using in-situ Reflection High Energy Electron Defraction (RHEED). Measurents made on MOS structures of capacitance-voltage, current-voltage, field break-down, hysteresis, and mobile ion drift indicate that these films are ‘comparable’ to thermally (Ts >1100 °C) grown oxides. The structural properties of the films arg studied by ir spectroscopy and ellipsometry.
The Chemical Interface of Microwave Plasma Deposited SiO2 Films
Authors: Parks C. C. , Robinson B. , Leary H. J. , Childs K. D. , Coyle G. J.
Published: March 2011

The bulk and interfacial chemistry of a microwave plasma deposited SiO2 film has been studied. The SiO2 was deposited on single crystal Si<100> using a plasma enhanced chemical vapor deposition (PECVD) technique. The deposition was accomplished by injecting 2% SiH4 in helium downstream of a N20 microwave-generated discharge. Materials properties of these films were characterized using a combination of surface analytical techniques: Auger electron spectroscopy (AES), X-ray photoelectron spectroscopy (XPS), and secondary ion mass spectroscopy (SIMS). The width of the interface was determined by AES-depth profiling to be less than 5.0 nm. Normal and grazing-angle XPS measurements indicated the presence of unique N and Si chemical species at the SiO2/Si interface. The SIMS data confirmed the presence of interfacial and bulk nitrogen, as well as detecting the presence of hydrogen and fluorine in the bulk oxide. The relationship between the analytical results and electrical data, obtained using MOS structures fabricated from the deposited oxide, will be discussed.
Thermal xidation of silicon in dry oxygen: - the role of crystallographic orientation -
Authors: Taniguchi K. , Hamaguchi C. , Kobayashit K. , Hirayamat M.
Published: March 2011

Based upon the linear-parabolic growth model of silicon oxidation, accurate kinetic rate constants are determined for various crystallographic orientation wafers in the 900 −1100°C range. The parabolic rate constant is independent of substrate orientation above 1000 °C, while, at 900°C, it depends on the orientation of the underlying substrate. The behavior of the parabolic rate constant at low temperature can be explained by accounting for Si-O bond-breaking due to stress during the oxide growth. The linear rate constant is observed to depend on the crystallographic orientation of the silicon surface in all temperature range. The orientation dependence of the linear rate constant is explained by both strain relaxation of the oxide film and areal atomic density of silicon at the silicon/oxide interface.
Structural Inhomogeneities Of SiO2 Quartz Gláss
Authors: Bochyński Zenon
Published: March 2011

Till now the only effective method of direct determination of structural parameters has been X-ray diffraction structural analysis. This method applied to crystalline materials has proved a great success and applied to noncrystalline substances like for example inorganic glasses, is becoming more and more successful.

Beginning with the W. Ostwald proposition /1913/ carried out by W. Friedrich /1913/ and P. Debye /1915/ through the papers by B.E. Warren et al. /1934–1942/ or by E.A. Poray-Koshits et al. /1934–1942/ till the most recently published papers devoted to structural studies of noncrystalline /amorphous/ materials we follow a significant progress in technology and methodology of these studies.

The resulting significant improvement to the accuracy of results yields much more accurate structural models of non-crystalline materials.
Formation and Passivation of New Paramagnetic Defects Associated With Thermal Oxides On Silicon
Authors: Brower Keith L.
Published: March 2011

A new spin resonance spectrum has been observed with electron paramagnetic resonance in thermal oxides grown on (111) silicon. Our analysis indicates that this new spectrum consists of two isotropic resonances. One resonance has a g-value of 2.0026 and a linewidth (FWHM) of 1.2 G (labeled SL8); the other resonance has a g-value of 2.0029 and a linewidth (FWHM) of 5 G (labeled SL9). These spectra might be due to impurity contamination resulting from the oxidation process and associated with defects at interior surfaces. The SL8 resonance in particular appears to be located within the as-grown thermal oxide. The effects of 60Co gamma irradiation and annealing in either hydrogen or ammonia on these spectra are also presented in this paper.
Submicron Roughness Determination at the Si-SiO2 Interface and Correlations to Prccessing Steps and Electronic Properties
Authors: Hahn Peter O. , Lampert I. , Schnegg A.
Published: March 2011

A newly developed optical surface characterization technique using the diffuse scattered light of two laser beams will be presented. The method determines root-mean-square roughness values (RMS) of surfaces down to 1 Å and corresponding correlation lengths in the submicron area.
Oxidation Kinetics of Ge+-Ion Implanted Si
Authors: Holland O. W. , White C. W. , Fathy D.
Published: March 2011

Kinetic data are provided for oxidation of Ge+-ion implanted Si over a range of temperature and oxidation ambient. Oxidation rates were enhanced in implanted Si and, over most of the range studied, found to be consistent with a modified reaction at the oxide/Si interface. However, this reaction is shown to be more complex than in virgin Si and could not be represented by a single activation energy. An anomalous behavior is exhibited at low-temperature for steam oxidation. This behavior is characterized and the mechanisms which are responsible are discussed.
Scanning Tunneling Microscopy Studies of the Initial Stages of Thin Film Growth: the Role of the Surface Dangling Bonds
Authors: Avouris Ph. , Wolkow R. , Bozso F. , Hamers R. J.
Published: March 2011

We present STM and photoemission studies of the reactions of Si(100)-(2×1) and Si(111)–(7×7) with NH3. STM allows us to image the occupied and unoccupied states of the reacting systems and to obtain electronic spectra with atomic lateral resolution. Thus, for the first time, a surface chemical reaction can be probed at the atomic level. We find that both surfaces are reactive even at 100K. However, both the extent of the reaction and the reaction products at 300K are different on the two surfaces. STM also shows that while surface dangling bonds are essential for low-temperature reactivity, not all triplycoordinated Si sites are chemically equivalent. On the 7×7 surface the rest-atoms are more reactive than center-adatoms which, in turn, are more reactive than corner-adatoms.
Coupled Diffusion of Ion-Implanted Arsenic in Silicon Dioxide
Authors: Lee S.- Tong , Lavine J. P. , Fellinger P. R.
Published: March 2011

A fast diffusing As species in ion-implanted SiO2 in N2 annealing ambient has been observed for the first time. This As diffuses 20X faster at 1100°C than the slow As found in oxidizing ambients. The activation energy of diffusion of this fast As is 0.71 eV, in sharp contrast to 4.3 and 4.0 eV for the slow As in O2 and O2 /H2O, respectively. The fast species is believed to be As occupying either the O-site or interstitial site in the SiO2 network. By assuming a fast and a slow species coupled together by transitions, we were able to obtain reasonable fits to the SINS diffusion profiles.
Grain Growth in Polycrystalline Silicon Films
Authors: Thompson C. V.
Published: March 2011

Experimental observations of recrystallization, normal grain growth and secondary grain growth in silicon films are reviewed. Normal grain growth leads to grain sizes which are approximately equal to the film thickness. Secondary grain growth can lead to larger grains with restricted crystallographic textures. These procesess are affected by the as-deposited or as-crystallized grain structures and orientations. The rate of grain growth has been shown to be higher in phosphorous or arsenic doped films. Ion bombardment, oxidation, and interactions with silicides also lead to increased grain growth rates. Grain growth enhancement has been related to increased point defect concentrations or dopant redistribution.
Dopant Diffusion and Grain Growth in Arsenic-Implanted Poly-Si
Authors: Zheng L. R. , Hung L. S. , Mayer J. W.
Published: March 2011

The diffusion behavior of arsenic and the grain growth of Si in arsenic doped poly-Si were investigated by MeV4 He2+ backscattering techniques and transmission electron microscopy. By implanting arsenic ions into poly-Si films the surface portion was made amorphous and crystallized upon annealing. In-situ mssurements showed crystal nucleation and growth at temperatures of 650 – 700° C with a dimension comparable to the thickness of the amorphous layer. Annealing at temperatures up to 850°C increased the number of the large grains, but the average grain size did not change significantly. In the unimplanted region grains retained their initial size until 885°C, although implanted arsenic was found to diffuse into this region along grain boundaries. At 885°C penetration of arsenic into the interior of grains caused significant grain growth. We also found that single implants of boron somewhat increased grain size, whereas boron codoped with arsenic appeared to reduce the effect of arsenic doping. These observations support the hypothesis that the enhanced growth rate and the electrical activity of Si near the grain boundary are closely interrelated.
Kinetic Modeling of Grain Growth in Polycrystalline Silicon Films Doped with Phosphorus and Boron
Authors: Kim H.-J. , Thompson C. V.
Published: March 2011

In previous work it has been shown that doping of silicon with P or As leads to enhanced rates of grain growth while doping with B has little effect, except in compensation of the effect of P or As. Here we report a detailed study of the effects of P doping on normal grain growth in silicon films. We also outline a kinetic model for grain growth which is consistent with the various observed effects of dopants. This model is based on the assumption that dopants primarily affect grain boundary mobilities and that grain boundary motion occurs through parallel diffusive and non-diffusive processes. It is further assumed that the rate of the diffusive process is proportional to the vacancy concentration which is a known function of the electron concentration.
Applications of Polysilicon Films in Microsensors and Microactuators
Authors: Howe Roger T.
Published: March 2011

This paper reviews the applications of polysilicon in microsensor technology and in the emerging field of microfabricated actuators. Polysilicon is an attractive material for thin-film strain gauges, and is also used to fabricate micromechanical structures. The need for better understanding of the non-electrical properties of polysilicon, such as Young's modulus, residual strain, ultimate strength, friction, and wear, is emphasized.
Structural and Electrical Properties of Heavily-Doped Rapid-thermal-Processed Polysilicon Emitters and Contacts on Silicon
Authors: Raicu Bruha , Christel L. A. , Huang K.-G. , Hashimoto Shin , Gibson W. M. , Ward I.
Published: March 2011

Supersaturated high-conductivity polycrystalline silicon (polysilicon) formed by rapid thermal processing (RTP) is a promising new material for emitters, contacts and diffusion sources in advanced high-speed bipolar and MOS IC technologies.

A matrix of processing conditions was used to evaluate the effect of polysilicon thickness, implant dose, RTP conditions and the nature of the substrate on the dopant diffusion in both the polysilicon and single crystal substrate and also on the interface properties.

Results of conductivity measurements, spreading resistance profiling (SRP), secondary ion mass spectroscopy (SIMS), transmission electron microscopy (TEM) and Rutherford backscattering spectroscopy (RBS)/channeling are presented. The results have proved the formation of shallow, defect-free junctions and epitaxial emitters with low series resistance and improved contact properties.
Characterization of Arsenic Implanted Epitaxially Aligned Polysilicon-on-Silicon Films
Authors: Hoyt J. L. , Crabbé E. F. , Pease R. F. W. , Gibbons J. F.
Published: March 2011

Nonuniformities in the polysilicon-to-silicon interface and in the polysilicon structure are expected to produce a nonuniform diffusion front when arsenic is diffused from polysilicon during epitaxial alignment. Using transmission electron microscopy, we find surprisingly uniform arsenic diffusion fronts in the underlying silicon substrate following high temperature annealing. Several explanations of this result are proposed. We also report new evidence of a strong reduction in the time to achieve complete epitaxial transformation of the polysilicon when the polysilicon thickness is reduced. A corresponding reduction in the associated arsenic penetration depth is demonstrated.
Picosecond Optical Determination of Carrier Lifetime in Polysilicon Films
Authors: Bambha N. K. , Nighan W. L. , Campbell I. H. , Fauchet P. M. , Johnson N. M.
Published: March 2011

The lifetime of optically injected carriers is determined in polySi/SiO2/Si structures grown by LPCVD at 625°C. These samples are as-grown, have undergone H diffusion or have been implanted by phosphorous ions, followed by various annealing schedules. The lifetime measurement is done in an all-optical, contactless fashion, using the tools of picosecond time-resolved spectroscopy. We find that the lifetime due to recombination at the grain boundaries (trapping time) increases after implantation only if subsequent annealing increases the grain size. The trapping time also increases after hydrogen diffusion. After trapping in relatively shallow grain boundary states, thermalization into deeper lying states is slow on a subnanosecond time scale.
Low Temperature Annealing of LPCVD Silicon Films
Authors: Aoyama T. , Konishi N. , Suzuki T. , Miyata K.
Published: March 2011

Low temperature, 600°C annealing of LPCVD films was investigated by x-ray diffraction, ESR, TEM, and carrier mobility measurements. An optimum deposition temperature of about 550°C was found to yield good crystallinity and large electron mobility for annealed films; large grain sizes, a maximum crystallite size, and a maximum electron spin density were also observed for films deposited at the optimum temperature. Electron spin density for as-deposited films correlated with the crystalline volume by x-ray diffraction measurements on the films after annealing. This implys that only those amorphous components with high electron spin density can be converted into the crystalline phase by 600°C annealing.
Effects of Hydrogenation on the Off-State of Polysilicon Thin Film Transistors
Authors: Khan Babar A. , Pandya Ranjana
Published: March 2011

We have carried out transient photoconductivity experiments on hydrogenated and unhydrogenated polysilicon Thin Film Transistors (TFTs) which indicate that the primary effect of plasma hydrogenation is the reduction by several orders of magnitude of the band tail trapping states. A smaller effect is a reduction of the dangling bond density by a factor of 2 or 3 as indicated by Electron Spin Resonance (ESR) measurements. Since the dangling bond is associated with the generation/recombination center, it may not be obvious how such a small reduction in generation/recombination center density leads to over 2 orders of magnitude reduction in off-state current of the TFTs. In this paper, we describe how the large reduction of band tail states can lead to significant reduction of carrier generation near the contacts despite the fact that the generation/recombination center density is not changed significantly. This reduction of carrier generation leads to the observed reduction in off-state currents.
Quantum Size Effect in Polysilicon Gates
Authors: Lifshitz N. , Laryi S. , Sheng T. T.
Published: March 2011

It has been observed by several authors that metal-oxide-semiconductor devices with polycrystalline Si (polySi) gates behave differently depending on the doping species in polySi: the work-function difference between the silicon substrate and the gate (øps) is higher when the gates are doped with arsenic than when they are doped with phosphorus.

We believe that the different behavior of øps. can be explained by different grain textures at the polySi/SiO2 interface. Our transmission electron microscoey of the films indicates that while P-doped material consists of large (≈3000Å) grains, As-doped polySi preserves its as-deposited columnar structure – even after a high temperature anneal. Moreover, at the interface with the gate oxide an as-deposited microstructure with very small (≈100Å) “embrionic” grains is preserved. On the basis of these observations, we suggest a model for the different behavior of ø ps. The model is based on a quantum-size effect which becomes important for such small grain dimensions at the interface in As-doped polySi. This effect drastically reduces the number of states available in the conduction band at low energies. The resulting shift of the Fermi level provides a qualitative explanation for the observed puzzling difference between the work-functions of Asand P- doped polySi.
Electrical and Electronic Properties of Grain Boundaries in Silicon
Authors: Queisser Hans J. , Werner Jorgen H.
Published: March 2011

The electronic states at silicon grain boundaries trap preferentially majority carriers, thus cause a potential barrier impeding current flow. We here summarize measurement techniques for the energy distribution of these grain boundary traps. The analysis reveals band tails due to disorder in the boundary plane as well as interface state continua at midgap. The spatial distribution of trapped charges results in significant electrostatic potential fluctuations which are observable in ac-admittance and noise experiments; the charge fluctuations cause in particular 1/f-like noise. The naive model of dangling bonds to describe grain boundary charges is insufficient, impurity atoms, especially oxygen, play essential roles in determining electronic behavior.
Structural and Electrical Properties of Molecular Beam Deposited Polycrystalline Silicon
Authors: Delage Sylvain L. , Jeng S.-J. , Jousse D. , Iyer S. S.
Published: March 2011

The structural and electrical properties have been investigated of antimony doped polycrystalline silicon films obtained by molecular beam deposition on oxidized silicon substrates. We show that low resistivity films with smooth morphology are obtained by Solid Phase Crystallization of antimony doped amorphous silicon layers deposited at 250°C. A resistivity of 4.3 mΩ cm is obtained by crystallizing the films at temperatures as low as 650°C for 15 minutes. Similar resistivities are typically obtained by Chemical Vapor Deposition at temperature of at least 850 °C. In-situ crystallization of the amorphous silicon is needed to obtain low resistivity polysilicon. We also show that direct deposition above 650 ° C gives rise to polycrystalline silicon with much higher resistivities.
Interaction of Deuterium with Buried Oxides in Silicon
Authors: Myers S. M.
Published: March 2011

Silicon with buried oxides formed by ion implantation (SIMOX) or zone-melt recrystallization (ZMR) was exposed to deuterium gas at temperatures from 773 K to 1273 K, and the depth profile of the D was then determined by nuclear-reaction analysis. The D was localized within the buried oxide, with no measurable quantity in the Si phase. Uptake was controlled by permeation through the Si overlayer, and the permeability of D in Si was determined at 873 K. The sample dependence of D uptake indicated substantially fewer defect-trap sites in SIMOX oxide annealed at 1678 K as opposed to 1548 K, with still smaller defect densities in the ZMR oxide. Hydrogen exposure at 1273 K substantially disrupted the SIMOX structures.
Zone-Melt-Recrystallization of Silicon-On-Insulator Films Using a Dual-Lamp Apparatus
Authors: Ramesh S.
Published: March 2011

We have studied the recrystallization of silicon films using a focused dual-lamp apparatus. By careful measurement and control of the power density profile (and focal-plane location) of the line-image and of the uniformity of the substrate temperature we have achieved recrystallization of SOI films on 4“silicon wafers. By taking advantage of the measured difference in power-density-profiles of an arc lamp and a tungsten lamp in the dual-lamp apparatus we have achieved low temperature-gradient, reduced-stress recrystallization yielding SOI films in which the usual branched pattern of subgrain-boundaries are replaced by individual dislocations. In situ study of the melt- and growth-fronts, was done using a viewing system with a resolution of - 10 ¼m. We have also done studies of stress-relief schemes.
Layered Structures Composed of Si, Ge, GaAs, and Fluorides
Authors: Ishiwara H. , Asano T. , Tsutsui K. , Lee H.C. , Furukawa S.
Published: March 2011

Recent progress in the heteroepitaxial growth of layered structures of Si, Ge, GaAs, and alkaline earth fluorides is reviewed. Effectiveness of the predeposition technique, in which a thin Si layer is deposited on the CaF2 surface at room temperature prior to the growth of a thick Si film at 800 °C, is shown for the growth of Si films on CaF2/Si structures. In case of the overgrowth of Ge and GaAs films on (111) substrates, modification of the fluoride surface by electron beam exposure is effective to increase the wet-tability between fluoride and semiconductor films and to improve the crystal -1 inity and surface morphology of the films. Finally, antiphase disorder in the GaAs(100) films grown on fluorides is experimentally studied and the generation mechanisms are discussed.
Formation of Buried Tisi2 Layers in Single Crystal Silicon by Ion Implantion
Authors: Madakson P. , Clark G.J. , Legoues F.K. , d'Heurle F.M. , Baglin J.E.E.
Published: March 2011

Buried TiSi2 layers, about 600Å thick and 900Å below the surface, were formed in < 111> silicon by ion implantation. The implantation was done with either 120 or 170 keV Ti+ to doses ranging from 5 x 1016 to 2 x 1017 ions/cm2, and at temperatures of between ambient and 650° C. Annealing was done at 600° C, 700°C and 1000°C. Continuous buried layers were achieved only with samples implanted with doses equal or greater than 1017 ions/cm2 and at temperatures above 450°C. Below this dose TiSi2, was present only as discrete precipitates. For room temperature implants, the TiSi2, layer is formed on the surface. The damage present consists of dispersed TiSi6 precipitates and microtwins.
Buried Oxide Soi: Materials, Devices, and VLSI Circuits
Authors: Chen C.-E. Daniel , Team Rad-Hard Soi Project
Published: March 2011

In the past couple of years, buried oxide SOI has emerged as the leading SOI approach. Significant advances have been made in the understanding and the preparation of the buried oxide substrates. Various VLSI circuits have been demonstrated with excellent results, proving the maturity and the manufacturability of this technology. In this paper, buried oxide material properties, device parameters and the implementation of a 2.5 urn 4K SRAM and a 1.25 pm 16K SRAM on the buried oxide substrates are reviewed.
Radiation-Induced Oxide Charge Distributions in Simox Buried Oxides
Authors: Hwang J. M. , Bartko J. , Rai-Choudhury P. , Bailey W. E.
Published: March 2011

In ionizing-radiation environments, oxide charge buildup in the buried oxide of SIMOX SOI material causes an increase in the back-channel leakage current, resulting in an instability in electronic circuits formed on SIMOX wafers. We report the measured distributions of radiation-induced oxide charge density in buried oxides formed by oxygen implantation. These are obtained by etch-back experiments including C-V measurements using a mercury probe and ellipsometer measurements. The results show a region of higher charge density about 1500A from the top interface with a lower density region within a few hundred angstroms of the top interface. The results also show that the oxide charge density decreases with annealing temperature. Some unusual optical properties of SIMOX oxide observed in ellipsometer measurements are discussed comparatively with thermal oxide.
Temperature Dependence of Rapid Thermal Annealing of Silicon on Sapphire
Authors: Richmond Eliezer Dovid , Campisi George , Twigg Mark
Published: March 2011

The material improvement of silicon on sapphire by rapid thermal annealing (RTA) is investigated as a function of the maximum temperature during the RTA cycle. Dramatic improvement of the crystalline quality throughout the silicon epilayer occurs for the lowest RTA temperature used (1160°C). The dechanneled fraction at the surface, Xo = 0.033, for the highest temperature anneal, gives bulk-like silicon values. Thus, at the surface, the crystalline quality is like bulk silicon. For the higher temperature anneals, transmission electron microscopy reveals that only a few microtwins extend to the surface. The defect microstructure in the region of the silicon/sapphire interface is substantially reduced. The RTA results in Al autodoping on the order of 1017 cm-3. The strain in the silicon epilayer is the same both before and after the RTA. The defect elimination can be explained in terms of the motion of the incoherent boundaries of the microtwins.
Porosity Determinations in Buried and Surface Layers of Porous Silicon
Authors: Guilinger Terry R. , Kelly Michael J. , Tsao Sylvia S.
Published: March 2011

Gravimetric techniques offer a convenient and accurate method of determining surface layer porosity in both n- and p-type porous silicon (PS). Porosity of the PS affects its volume expansion on oxidation and the insulating properties of the resulting oxide. Optimal porosity (ca. 55%) yields fully dense, insulating oxides with minimal expansion-induced stresses. Two factors affect the porosity: chemical dissolution of PS by the anodization electrolyte, and oxidation of the PS to produce a native oxide on the surface. Buried layer porosities cannot normally be measured by gravimetric techniques unless the volume of the buried layer is large enough to yield a measurable weight change on anodization. We therefore used a form of Faraday's Law to determine buried layer porosities and determined that they can be correlated with porosities of surface layers formed under identical conditions.
Dissolution and Disintegration of Uniform SiO2 Layers During Direct Silicon Wafer Bonding
Authors: Ahn Kun-Young , Gösele Ulrich , Smith Patrick
Published: March 2011

The conditions for the dissolution and disintegration of SiO2 layers between silicon wafers during direct wafer bonding are discussed in terms of two possible mechanisms. The calculated maximal thickness of a SiO2 layer which may be completely dissolved does not only depend on the bonding temperature and time but also on the starting concentration of interstitial oxygen in the silicon wafers. Finally, the influence of rotational misorientation of the two wafers on the behavior of the S1O2 layers is dealt with.
Molecular Beam Epitaxial Growth of Gaas on Silicon with Buried Implanted Oxides
Authors: Das K. , Humphreys T.P. , Posthill J.B. , Parikh N. , Tarn J. , El-Masry N. , Bedair S.M. , Chu W.K. , Wortman J.J.
Published: March 2011

We report the first results of direct growth of GaAs by molecular beam epitaxy on nominally (100) oriented silicon with buried implanted oxides. Rutherford backscattering and transmission electron microscopy techniques have been used to characterize these layers. The formation of hillocks and a uniform layer of GaAs in the intervening regions between hillocks have been observed. Microtwins, dislocations and antiphase domain boundaries are the predominant defects observed in these layers.
Rapid Thermal Processing of Multiple Low Dose Oxygen Implantations for SIMOX
Authors: Blake J. , Gelpey J. C. , Lee D. M. , Rowland L. , Rozgony G. A.
Published: March 2011

A cross-sectional transmission electron microscopy study has been performed on SIMOX wafers prepared using three sequential low dose (6 x 1017 cm2) oxygen implantations. After each implant the wafers were annealed using rapid thermal processing at temperatures up to 1360°C for times of 1 to 5 minutes. The TEM results show that, although low dislocation densities are obtained, oxygen precipitate dissolution is incomplete for these conditions. Therefore, longer annealing times will be required. In addition, lower increments of oxygen dose are recommended to approach dislocation-free superficial silicon layers.