bluuebunny/crossref_metadata_2025 huggingface dataset:
Diffuse X-Ray Scattering Study of Defects Created by KeV Ion Implants In Si
Authors: Partyka P. J. , Averback R. S. , Nordlund K. , Robinson I. K. , Walko D. , Ehrhart P. , Diaz de la Rubia T. , Tang M.
Published: April 2011

Diffuse x-ray scattering (DXS) and computer simulation techniques were employed to investigate the defect structure produced in Si by low keV ion and MeV electron irradiations. DXS measurements were performed for keV Ga and He implants, demonstrating the ability of the technique to provide both bulk and near-surface measurements at defect concentrations of about 1000 ppm. A rigorous analysis of these results is complicated due to the complex nature of the ion damage in Si. A computer simulation framework is developed to aid in the analysis of this data. In this technique, defects are simulated and their strain fields are calculated by simply relaxing the atoms around the defect to their equilibrium positions. The diffuse scattering is then calculated from the strain field, and the results are compared to the experimental measurements. Computer simulations are presented here only for the case of electron irradiation damage and compared to published measurements. Application of the technique to more complicated structures is planned and should pose no serious problems in the computational framework already developed.
Fluorescence Imaging of the Aluminum Oxide Transformation on the Surface of Single Crystal (111) NiAl
Authors: Schaffer H. E. , Lipkin D. M. , Adar F. , Clarke D. R.
Published: April 2011

Microscopic examination of the surface of single crystal (111) NiAl during various stages of oxidation at 1100 C in air shows the development of islands composed of rings of different colors.These islands appear to grow in size and eventually impinge with increased exposure. Microscopic fluorescence mapping of the surfaces of three single crystals subjected to varied exposure times provides an identification of the composition of the islands and the surrounding area as two different allotropes of alurninum oxide.Additionally, analysis of the map spectra demonstrates the decrease of intensity of their characteristic fluorescence bands in the island centers with increasing island size, which we refer to as “volcanic” intensity topography. Thus, the observed color variation is an interference effect, due to varied films thicknesses through the islands. Finally, the energies of the fluorescent bands are seen to shift as a function of distance from the island center, indicating the development of strain gradients across the islands.
Nucleation on Defects in Heteroepitaxy
Authors: Venables J. A.
Published: April 2011

The rate equation treatment of nucleation and growth on perfect substrates has been extended to cover nucleation on random defect sites, and problems involving 1-dimensional (1D) diffusion to sinks. This paper recaps the results of rate equation treatments on perfect terraces, and sumnarises some new models, including: 1) nucleation on point defects, with application to nm-sized Fe and Co particles grown on various CaF2substrates; 2) nucleation and diffusion in finite 1D deposits, with application to diffusion over, and the break-up of, multilayer deposits of Ag/Ge(111) and Ag/Fe(110); 3) 1D models developed for nucleation in competition with step capture. Comparison of rate-diffusion equations with experiment can result in values for, or bounds on, the controlling energies, in a way which illuminates the main features of interatomic forces at surfaces. The use of defects to grow thin film arrays for practical application presents some interesting challenges at both the nucleation and growth stages, which are discussed briefly.
Effects of Hydrogen on Nucleation of Islands During Si(001) Mbe Growth
Authors: Mizushima Kazuki , Šmilauer Pavel , Vvedensky Dimitri D.
Published: April 2011

Kinetic Monte Carlo simulations with two species (Si and H) have been performed to identify the mechanism behind the H-induced creation of a strongly temperature-dependent high density of Si islands in the temperature range of 300–550 K during molecular-beam epitaxy on Si(001) surface. A model is proposed to explain this effect as a result of an activated exchange between H and Si at Si island edges.
The As-Grown Microtopologies of Modified-Lely SiC(0001) Terraced Vicinal Surfaces
Authors: Marek T. , Heindl J. , Strunk H.P. , Eckstein R. , Müller St.G. , Hofmann D.
Published: April 2011

Risers and treads on terraced surfaces of modified-Lely (M-Lely) grown 6H-SiC(0001) bulk crystals are investigated by reflection electron microscopy (REM). On risers we find parallel steps, with a height of one or two unit cells. On treads we find in addition to growth spirals island formation. We take these observations to conclude that two competitive processes operate in parallel, the step-flow mode and the two-dimensional nucleation.
Structural and Morphological Characterization of Ultrathin Films of an Asymmetric Polydiacetylene
Authors: Wang H. C. , Cheong D. W. , Kumar J. , Sung C. , Tripathy S. K.
Published: April 2011

A soluble, asymmetrically substituted polydiacetylene, poly(BPOD), has been reported to form stable monolayers at the air-water interface by the Langmuir-Blodgett (LB) technique [2]. Preformed polydiacetylene has been deposited onto hydrophobic substrates as multilayers to form second order nonlinear optical thin films. Second harmonic generation was found to increase with the number of layers. From previous atomic force microscopy (AFM) studies backbone orientation along the dipping direction with an interchain spacing of about 5 A° was indicated [2].The film morphology and preferential molecular orientation of these LB films are further investigated by transmission electron microscopy (TEM). A specifically tailored sample preparation method for the ultrathin LB films was used. Multilayer films were deposited on hydrophobic collodion covered glass substrates for this purpose. Electron diffraction was employed to study the crystalline organization of mono and multilayers of LB films as well as cast films.
Exact Scaling Form for the Island Size Distribution in Submonolayer Epitaxial Growth
Authors: Bartelt M. C. , Evans J. W.
Published: April 2011

The exact scaling form is determined for the size distribution of islands created via irreversible nucleation and growth during submonolayer deposition. This form is controlled by a dependence on size of the propensity for islands to “capture” diffusing adatoms. This sizedependence is determined directly from simulations. It reflects a complex relationship between the size of an island, and the area of its cell in a tessellation of the surface based on the island locations. The relationship corresponds to a correlation between island size and separation.
Step Contours in the Development of Periodically Modulated Vicinal Surfaces
Authors: Tanaka S. , Umbach C. C. , Blakely J. M. , Tromp R. M. , Mankos M.
Published: April 2011

The connection between the atomic step distributions and decay modes of modulated surfaces is the focus of this paper. We have examined the arrangements of atomic steps on real 1- and 2-D periodic structures by scanning tunneling microscopy(STM) and low energy electron microscopy(LEEM) and have followed their development at temperature by LEEM. The steps present on the surface due to small ‘miscuts’ from exact singular planes can have major effects on both the mechanisms of shape development and the actual shapes that result. Major differences exist in the modes of development between 1- and 2-D periodic step arrays. Some of these observations have led us to a method for producing arrays of step-free Si(001) regions that may have application in device processing.
Surface Morphology of Si1−x−y GexCy Epitaxial Films Deposited by Low Temperature UHV-CVD
Authors: John S. , Quinones E. J. , Ferguson B. , Ray S. K. , Mullins C. B. , Banerjee S. K.
Published: April 2011

Si1−x−y GexCy epitaxial films offer wider control of strain and bandgap. In such films the morphology is an important indication of the crystalline quality of the material. We report on the morphology of Si1−x−y GexCy epitaxial thin films deposited by Ultra High Vacuum Chemical Vapor Deposition at a temperature of 550° C and deposition pressures ranging from 1 to 10 mTorr. The precursors used were Si2H6, GeH4 and CH3SiH3. Germanium mole fractions ranging from 0% to 40% were studied with carbon concentrations varying from 2×1019 to 2×1021 atoms/cm3. AFM analysis of the surface indicates that the roughness is a function of both the carbon concentration and the film thickness. For high germanium concentrations with thickness beyond the critical thickness (of Si1−xGex), carbon is found to decrease the surface roughness of the film. Thus the surface morphology confirms the strain compensation provided by carbon which is also observed using XRD. For films below the critical thickness, as the carbon concentration is increased, three dimensional islanding is observed by RHEED and AFM, degrading the epitaxial quality of the material.
The Formation and Evolution of InAs 3D Islands on GaAs(001) and a Comparative C-AFM and NC-AFM Study of InAs 3D Islands
Authors: Ramachandran T. R. , Kobayashi N. P. , Heitz R. , Chen P. , Madhukar A.
Published: April 2011

The two-dimensional (2D) to three-dimensional (3D) morphology change in the highly strained growth of InAs on GaAs(001) is examined via in-situ, ultra-high vacuum (UHV) scanning tunneling microscopy (STM) and contact-mode atomic force microscopy (C-AFM). The formation of 3D InAs islands (˜2–4nm high) at an InAs delivery, θ˜1.57ML is found to be preceded by the appearance of small quasi-3D clusters (˜0.6–1.2nm high). The 2D to 3D transition is found to occur over a range of θ from ˜1.45ML to 1.74ML, with a varying and gradual mass transfer from 2D to 3D features with increasing θ. The InAs 3D islands are also examined in this study using non-contact AFM (NC-AFM) in order to assess the usefulness of this technique for imaging 3D features. Unlike the constancy observed in the C-AFM images, the NC-AFM images exhibit a marked imaging condition dependence. The variability observed in the NC-AFM images is qualitatively compared to the outcome of the simplest, force-gradient model of NC-AFM in order to extract a guideline for NC-AFM imaging of 3D features.
The Morphological Stability of Strained Epitaxial Layers
Authors: Wessels B. W.
Published: April 2011

The morphological stability of strained-layer thin films is analyzed using classical nucleation theory. For the case where strain relaxation occurs by formation of coherent islands, the model predicts that the critical thickness for transition from two-dimensional (2D) to three dimensional (3D) growth depends inversely on the square of the misfit. The predicted dependence of critical thickness on misfit is in agreement with recent experimental studies on the heteropitaxy of III-V compounds.
A 3-D Kinetic Monte Carlo Study of the Growth of Si Thin Films Using Beams With Varying Angle of Incidence
Authors: Levine S.W. , Engstrom J.R. , Clancy P.
Published: April 2011

Three-dimensional Kinetic Monte Carlo simulations were used to model the deposition of a hyperthermal molecular beam at varying angles of incidence. The simulations incorporate incident atom-substrate interactions, many layer growth, and attempt to mimic deposition and growth of Si on a Si(100) substrate. At high angles of incidence, the formation of “flake”-like structures are seen. The growth of the flakes follow the same general trends as previous two-dimensional simulations where non-local shadowing produces a porous thin film and the columns grow into the incident beam. Increased substrate temperature increased the widths of the flakes perpendicular to the path of the beam and allowed the grown film to remain defect-free for a time before columnar structure begins.
Roughening and Preroughening of Diamond-Cubic {111} Surfaces
Authors: Woodraska Donald L. , Jaszczak John A.
Published: April 2011

Using a new solid-on-solid model that correctly takes into account the diamond-cubic crystal structure, both a roughening transition at temperature TR and a distinct preroughening transition at TPR≈0.43TR are found to exist on {111}surfaces of diamond-cubic materials. Results are presented for height-difference correlation functions, surface specific heats, step energies, etch rates, and a preroughening order parameter. Preroughening appears to arise naturally in our nearest-neighbor bond model from the entropic freedom available in the non-trivial crystal structure suggesting that preroughening may be more common than previously anticipated. Preroughening is shown to dramatically lower step energies and step-energy anisotropy on the {111} surface.
Preroughening of Si{111} may have been seen in experiments by Noh et al. [Phys. Rev. B 48, 1612 (1993)].
Characterization Of Grown-In Defects In CZ-SI Crystals By Bright Field IR Laser Interferometer
Authors: Nakai Katsuhiko , Hasebe Masami , Iwasaki Toshio , Tsumori Yasuo
Published: April 2011

We have developed a quantitative measurement method for the number density, size and morphology of grown-in defects in czochralski-grown silicon (CZ-Si) crystals with a bright-field infrared-laser interferometer (known as Oxygen Precipitate Profiler; OPP). Using this method we investigated the effect of crystal cooling condition during crystal growth on the formation of grown-in defects by growth holding experiments. The relation between gate oxide integrity (GOI) and grown-in defects was studied. It was revealed that the grown-in defects have octahedral shape and degrade the GOI performance. We estimate the density as well as cumulative volume of the grown-in defects and discuss the formation mechanism of them.
Tem Observation Of Grown-In Defects In CZ-Si Crystals And Their Secco Etching Properties
Authors: Kato Masahiro , Takeno Hiroshi , Kitagawara Yutaka
Published: April 2011

Grown-in defects detected by IR laser scattering tomography (LSTDs) in Czochralski-grown Si crystals were identified by transmission electron microscopy (TEM) with a special defect positioning technique. The basic structure of the LSTD was revealed to be a composite of two or three incomplete octahedral voids with the 100–300nm total size. The TEM images of the defect showed existence of 2∼4nm-thick walls surrounding the voids. These thin-walls are considered to be made of oxide, SiOx. These LSTDs are indeed dominant grown-in defect species in most of the commercial CZ-Si walers. The LSTD after 1200°C oxidation was also observed by TEM. The resulting image shows that the defect changed from void to filled oxide precipitate by the high temperature heat treatment. On the other hand, in very slowly pulled crystals with ∼0.4mm/min rate, interstitial type dislocation loops were observed as major defect species. Non-agitated Secco etching of these grown-in defects delineates “flow patterns” (FPs) or pits without the flow patterns. The FP forming property is shown to disappear by oxidation at temperature above 1150°C, while the defect itself remains stable. This implies that the grown-in defects lose their chemical properties to form FPs by the high-temperature oxidation. It is further revealed that the grown-in defects, which once lost the FP forming property by the high-temperature oxidation, can form FPs again by an intentional Cu contamination. Thus a possible FP formation factor is Cu decoration at the grown-in defect site. Defect formation model of the as-grown twin-type LSTD is also proposed.
Crystallographic Analysis Of Flow Pattern Defects In Dislocated Czochralski Silicon Crystals
Authors: Ikematsu Y. , Iwasaki T. , Harada H. , Tanaka K. , Fujinami M. , Hasebe M.
Published: April 2011

In dislocated Cz-Si crystals, rows of flow patterns (FP) and Secco etch pits (SEP) (2–3 mm in length, along <110> direction) can be revealed by Secco etch without agitation. In this study, the crystal defects forming FP-SEP rows in dislocated Cz-Si crystals are investigated by transmission electron microscopy. Microdefects, 0.1 μm in size, are observed in a row along a FP-SEP row, <110> direction. These defects were identified as oxygen precipitates with or without dislocation loops (interstitial-type), and voids with oxidized interiors. We conclude that FP originate from interstitial-type dislocation loops, and SEP are due to oxygen precipitates or voids.
Enhanced Dissolution Of Extrinsic Dislocation Loops In Silicon Annealed In NH3
Authors: Herner S. B. , Krishnamoorthy V. , Jones K. S. , Mogi T. K. , Gossmann H.-J.
Published: April 2011

The behavior of extrinsic dislocation loops in silicon was investigated by transmission electron microscopy. Loops were formed by an amorphizing implant and recrystallization anneal of Si wafers. Wafers were further annealed in either Ar or NH3. Wafers annealed in NH3 formed a thin (∼4 nm) SiNx film. The loops in samples in Ar showed a constant net number of interstitials bound by the loops, while those in samples annealed in NH3 showed a marked decrease. The results are explained by a supersaturation of vacancies recombining with the interstitials in loops. By integrating the measured difference between interstitials bound by the loops in samples annealed in Ar vs. NH3 over the distance from the surface to the loop layer, an estimate for the relative vacancy supersaturation is extracted. Comparison with estimates of vacancy supersaturations with nitridation from the change in Sb diffusivity show good agreement between the two methods.
Cooperative Chemical Rebonding In The Segregation Of Impurities In Silicon Grain Boundaries
Authors: Maiti A. , Chisholm M. F. , Pennycook S. J. , Pantelides S. T.
Published: April 2011

With ab initio calculations we show that the experimentally observed large segregation energies of As at Si grain boundaries can be explained by the formation of isolated dimers or ordered chains of dimers of threefold-coordinated As along the cores of grain boundary dislocations. We also find the intriguing possibility that As segregation may drive structural transformation of certain grain boundaries. Recently we have obtained the first atomic-resolution STEM images of As in a Si grain boundary, consistent with the formation of As dimers. Segregation energy of As dimers was found to be significantly higher in isolated dislocation cores, where larger site-variation in strain than in grain boundaries lead to further lowering of the electronic levels of As deep into the bandgap.
Formation Of Hydrogen Molecules In Crystalline Silicon Treated With Atomic Hydrogen
Authors: Murakami K. , Fukata N. , Sasaki S. , Ishioka K. , Nakamura K. G. , Kitajima M. , Fujimura S. , Kikuchi J. , Haneda H.
Published: April 2011

Hydrogen molecules have been formed in crystalline silicon at various temperatures by a hydrogen-atom remote treatment. The Raman spectrum of the vibrational lines of hydrogen molecules in crystalline silicon is detected for silicon samples treated at temperatures between 250 and 500° C. The maximum production is obtained at 400° C. The Raman spectrum of hydrogen molecules in silicon observed at room temperature exhibits a frequency shift of around 4158 cm−1 and a very broad half-width of approximately 34 cm−1. Isotope shift also can be observed at around 2990 cm−1 in silicon treated with deuterium atoms at 400° C. The frequency shifts of the observed lines are in close agreement with those reported for molecular hydrogen and deuterium in gas, liquid, and solid phases. We discuss a model for the hydrogen molecule configuration and rule out the possibility of high-pressure hydrogen molecular gas in microvoids in crystalline silicon. These results indicate that hydrogen molecules exist at the tetrahedral interstitial sites in crystalline silicon.
Dislocation Velocities In Gesi Bulk Alloys
Authors: Yonenaga I.
Published: April 2011

The mechanical strength and dislocation velocities in single crystal Ge1−xSix alloys grown by the Czochralski method were investigated by compressive deformation and by the etch pit technique, respectively. In the temperature range 450 – 700 °C and the stress range 3 – 20 MPa, the dislocation velocity in the GeSi alloys with x = 0.004 – 0.053 decreases monotonously with an increase in the Si content, reaching about a quarter of that in Ge at x = 0.053, and can be expressed as a function of the stress and the temperature. The yield stress of the GeSi alloy increases with increasing Si content from x = 0 to 0.4 and is temperature-insensitive at high temperatures, showing that the flow stress of alloy has an athermal component which is absent in elemental or compound semiconductors.
Influence Of Substrate Off-Cut On The Defect Structure In Relaxed Graded Si-Ge/Si Layers
Authors: Samavedam Srikanth B. , Romanato F. , Goorsky M. S. , Fitzgerald E. A.
Published: April 2011

Relaxed graded Si-Ge/Si layers can be used in a variety of micro-electronics applications such as templates for III-V/Si integration, in high speed field effect transistor (FET) structures and as detectors in optical communication. Each of these applications requires a different final Ge concentration in the graded Si-Ge layer. With increasing Ge content in the graded layer, some of the materials concerns that need to be addressed are- (i) a high surface roughness, (ii) the formation of dislocation pile-ups, and (iii) an increase in the threading dislocation density. We have shown that there is a substantial improvement in the surface roughness and the dislocation pile-up density of the graded Si-Ge layers by depositing on (001) 6° off-cut substrates. The substrate miscut also facilitates favorable intersections of {111} planes that aid reactions between the 60° dislocations to form edge dislocations with Burgers vectors of the type 1/2<110> and <100> resulting in a novel hexagonal dislocation structure. Such reactions occurred more readily in the Ge-rich regions of the graded layers where the growth temperature was high enough to aid dislocation climb. The edge dislocations with in-plane Burgers vectors lack a tilt component and the decreased rate of tilting in the Ge-rich regions is confirmed by triple crystal X-ray reciprocal space maps. This novel dislocation structure offers opportunities to explore new processes which may eliminate spatially variant strain fields in relaxed epitaxial layers.
Defects In Low Temperature Mbe-Grown Si And Sige/Si Structures
Authors: Chen W. M. , Buyanova I. A. , Monemar B.
Published: April 2011

We review our recent experimental results on important grown-in non-radiative defects in Si and SiGe/Si heterostructures grown by molecular beam epitaxy (MBE) at low temperature. Several types of such defects have been revealed by the optically detected magnetic resonance technique and were shown to play an important role in carrier recombination. Among them a dominant defect is identified to be the vacancy-oxygen (V-O) complex. Experimental evidence on the formation mechanisms of these non-radiative defects points at a low surface adatom mobility during low temperature growth as a major cause, and also ion bombardment as occurs e.g. during potential enhanced doping. Based on the gained knowledge, educated attempts by post-growth hydrogen and thermal treatments have been made to remove these harmful defects and to improve the radiative efficiency of the material.
EL2-Induced Upconversion Luminescence In GaAs
Authors: Alex V. , Iino T.
Published: April 2011

Near band gap luminescence in bulk-grown semi-insulating GaAs is excited in a two step process via the EL2 defect. While the conventionally excited photoluminescence of our samples is dominated by conduction band to acceptor transitions, the upconversion process selectively excites donor acceptor pair transitions. Illumination near the maximum of the EL2- photoquenching band at 1064 nm leads to a complete disappearance of the so called upconversion photoluminescence (UPL). Excitation with light of shorter wavelengths however only partially quenches the UPL. Excitation between 850nm and 900nm completely regenerates the UPL. The characteristic photorecovery transients of the UPL are described by the EL2 regeneration mechanism via the population of the acceptor level of the metastable EL2 by hot electrons. The recovery of the EL2 by simultaneous illumination with above and below band gap light enables the observation of UPL at wavelengths, where the EL2-defect would otherwise be rapidly quenched. Under these conditions we observe a remarkable increase of the UPL-efficiency.
Relationship Between Hydrogen-Related Metastable Defect And EL2-Level In GaAs Crystals
Authors: Shinagawa Tatsuyuki , Okumura Tsugunori
Published: April 2011

The relationship between the hydrogen-related metastable defect (M3/M4) and the EL2 level in n-GaAs crystals has been investigated. We found with various kinds of GaAs crystals that the hydrogen-related metastable couple (M3/M4), first reported by Buchwald et al., has been observed only in the crystals containing the EL2 defect. This fact was further confirmed by using LT-MBE GaAs crystals before and after rapid thermal annealing (RTA). Only in the n-LT-n sample annealed at 900°C, in which the EL2 defect was formed, the metastable couple (M3/M4) appeared upon hydrogenation. As hydrogenated, the EL2 level was passivated or dissociated. From bias-annealing experiments, the M4 level was completely annihilated by annealing at 573K, where the EL2 level was restored to its original concentration. We speculated from these results that both diffused hydrogen and preexisting arsenic antisite defect (AsGa) are responsible for the formation of the metastable defect(M3/M4).
Inspection Of Recombination Active Defects For Sige And Solar Cells
Authors: Astafiev O.V. , Kalinushkin V.P. , Abrosimov N.V.
Published: April 2011

Mapping Low Angle Light Scattering method (MLALS) is proposed to study defect structure in materials used for solar cell production. Several types of defects are observed in Czochralski Si1−xGex (0.022<x<0.047) single crystals. Recombination activity of these defects is investigated. The possibility of contactless visualisation of grain boundary recombination in polysilicon is also demonstrated.
Structural And Optical Characterization Of AlxGa1−xAs Grown At Low Temperatures By Organometallic Vapor Phase Epitaxy
Authors: Wankerl A. , Emerson D. T. , Cook M. J. , Shealy J. R.
Published: April 2011

We report on the low temperature growth of AlxGa1−xAs by conventional Organometallic Vapor Phase Epitaxy OMVPE for a substrate temperature of 500°C and V/III ratios extending to subunity. Optical, structural and electrical qualities are assessed with double crystal X-ray diffraction, Nomarski and atomic force microscopy, 1.6K and 300K photoluminescence, Rutherford backscattering and Hall measurements. Although our low temperature grown films are of good structural and optical quality, they exhibit high background p-doping (carbon) and high levels of hydrogen passivation. A method for extracting the carbon doping levels from lattice contraction measurements is suggested. The dependence of layer composition, free carrier concentration and hydrogen passivation on growth parameters are investigated. Moreover, the effects of post-growth annealing on free carrier concentration, lattice parameter and optical qualities are studied. The influence on the bandgap of bandtail states and compressive strain due to carbon are compared.
Electrically Detected Magnetic Resonance On GaAs/AIGaAs Heterostructures
Authors: Wimbauer T. , Hofmann D. M. , Meyer B. K. , Brandt M. S. , Brandl T. , Bayerl M. W. , Reinacher N. M. , Stutzmann M. , Mochizuki Y. , Mizuta M.
Published: April 2011

Electrically detected magnetic resonance (EDMR) has been used to study carrier recombination in GaAs/AlGaAs quantum well structures grown by molecular beam epitaxy. The spin dependent photoconductivity signals depend strongly on the electrical contact properties. Using silver paste contacts a narrow (18 G) resonance located at g = 2.001 is observed. It has been previously attributed to surface defects on GaAs. Using alloyed In-contacts other signals are detected. The dominant resonance observed at 9 GHz has an isotropic g-value of g = 1.99 with a halfwidth of 200 G and is therefore assigned to Cr4+. Other signals of considerably lower intensity are explained by the well known electron paramagnetic resonance (EPR) properties of the Gai-interstitial and the AsGa-antisite defects. EDMR performed at 34 GHz allows the experimental separation of the two sets of hyperfine lines.
Defects In 4H Silicon Carbide CVD Epilayers
Authors: Zhou L. , Pirouz P. , Powell J. A.
Published: April 2011

The characteristic defects of 4H-SiC homoepitaxial thin films grown on bulk substrates using chemical vapor deposition (CVD) are described based on transmission electron microscopy (TEM), atomic force microscopy (AFM) and surface decoration studies. Emphasis is placed on understanding the formation mechanism of surface triangular defects. Cross-sectional TEM observations revealed the existence of two variants of 3C-SiC inclusions in 4H epitaxial films. In the plan-view orientation, g4H = 3304 type reflections were found useful for distinguishing the two variants of 3C-SiC platelets that are present in the 4H epilayer. A decoration technique was employed to reveal the relationship between the 3C platelets and surface features, e.g., surface steps. A formation mechanism for surface triangular defects is proposed, which is partially confirmed by the etch pit patterns obtained on the epilayer surfaces after a molten KOH etch.
Charge Transient Spectroscopy Study Of Deep Centers In Cvd Diamond And Diamond-Like Films
Authors: Polyakov V.I. , Rukovishnikov A.I. , Rossukanyi N.M. , Varnin V.P. , Teremetskaya I.G. , Druz B.L. , Ostan E. , Hayes A.
Published: April 2011

The parameters of trapping centers in CVD diamond and Diamond-Like Carbon (DLC) films were studied by Charge Deep Level Transient Spectroscopy (Q-DLTS). The concentrations, activation energies, captures cross-section and location of the trapping centers were determined. The influence of post deposition heat treatment on the defect center parameters was studied. The Q-DLTS measurements showed that micro defects are acting as point trapping centers and have the continuous energy spectrum with one or two maximums at different energies. The nature of the trapping centers is discussed.
Field Drift Of Plasma-Induced Defects In Phosphorus Doped Si By Reverse Bias Annealing (RBA)
Authors: Takeuchi J. , Zaitsu Y. , Shimizu T. , Matsumoto S. , Wada K.
Published: April 2011

The property of plasma induced defects in phosphorus doped CZ silicon has been investigated by reverse bias annealing (RBA). After CF4 plasma exposure, charge density at the surface decreased since plasma induced negatively charged defects inactivated phosphorus. With the increase of annealing time, inactivated phosphorus area moved into the bulk with reverse bias of −3V. Thus it is clearly observed that negatively charged defects drifted from the surface into the bulk. The thermal dissociation energy for phosphorus-defect complexes is estimated to be 1.22eV from the Arrhenius plot of dissociation rate. These defects are likely to be Si self interstitials or vacancies.
Chemical Bonding of Fluorine Atoms in Siof Alloys: Microscopic Mechanisms for Reductions in the Dielectric Constant Relative to SiO2
Authors: Lucovsky G. , Yang H.
Published: April 2011

Si-O-F alloys have static dielectric constants (εs) significantly lower than SiO2. Infrared absorption spectra provide the basis modeling the molecular structure of these alloys. Contributions of electronic and vibrational transitions to εs are discussed in terms of an empirical chemical bonding model. Ab initio calculations are then used to identify inductive effects of Si- F bonds on the properties of Si-O-Si groups that are back-bonded to the Si atom of the Si-F group. These calculations provide a theoretical framework for understanding how relatively low concentrations of F atoms produce the significant decreases in εs reported for Si-O-F alloys.
The Thermal Stability of Fluorine Doped Silicon Oxide Films Formed by Ecrcvd With SiF4 and O2 Gases
Authors: Lee Seoghyeong , Yoo Jae-Yoon , Park Jong-Wan
Published: April 2011

The reliability of SiOF films for intermetal dielectrics in multilevel interconnections of ULSIs is investigated. SiOF films were deposited by ECRCVD using H-free source gases, i.e., SiF4 and O2. The effect of post plasma treatment on the moisture absorption and dielectric properties of SiOF films were carried out in terms of air exposure time. The reliability test of Cu / TiN / SiOF / Si specimen was carried out in terms of temperatures by RTA in N2 ambient. After O2 plasma treatment, no appreciable peak directly related to moisture absorption was detected. The C-V characteristics of the O2 plasma treated SiOF film showed that the film remained to hold the sound dielectric properties even after boiling treatment. The Cu / TiN / SiOF / Si system was found to be reliable up to 600 °C.
Thermal Stability of Fluorinated SiO2 Films: Effects of Hydration and Film-Substrate Interaction
Authors: Sullivan J. P. , Denison D. R. , Barbour J. C. , Newcomer P. P. , Apblett C. A. , Seager C. H. , Baca A. G.
Published: April 2011

The thermal stability of fluorinated SiO2 films (SiOF) was found to be dependent on F content and the type of substrate upon which the film was deposited. SiOF films with a range of F concentrations were deposited using an electron cyclotron resonance (ECR) plasma upon Si, Al/Si, TiN/Al/Si, and Al/SiO2/Si substrates. Following deposition, the films were deliberately hydrated and/or annealed and their stability assessed. Hydration was found to only affect the high F content films. Capacitance changes with annealing in the high F content films were found to occur beginning at 200°C. These changes, which were independent of substrate type, likely occurred due to desorption of H2O in the films. After annealing of the high F content films up to 400°C, a reduction in F content was found for SiOF films on some substrates. Significant reductions were found for SiOF films on Al/Si substrates, while little or no change was found for films on TiN/Al/Si, Al/SiO2/Si, or Si substrates. Local chemical analysis of those films which showed F reduction indicated that the F profile was approximately uniform throughout the layer and did not pile-up at the interface. The substrate-dependent thermal instability exhibited by these films suggests the chemical nature or qualities of the substrate may play a role in the F reduction reaction.
Fluorinated Heteroaromatic Polyethers for Low Dielectric Constant/High Temperature Applications
Authors: Maier G. , Schneider J. M. , Hecht R.
Published: April 2011

Synthesis and characterization of three classes of poly(arylene ether oxazole)s and poly(arylene ether thiazole)s with trifluoromethyl substituents in various positions is described. Based on these examples, the influence of the chemical structure of the polymers on properties such as glass transition temperature, solubility, and thermal stability will be discussed. Structural parameters studied are the number and nature of the heteroaromatic rings, the number and position of the trifluoromethyl groups, and the structure (flexibility, polarity) of various linking groups.
Properties of CAT-CVD Silicon Nitride Films and Their Application as Passivation Films
Authors: Okada Shinya , Matsumura Hideki
Published: April 2011

Silicon nitride (SiNx) films have been successfully synthesized by the catalytic chemical vapor deposition (cat-CVD) method using a gaseous mixture of silane (SiH4) and ammonia (NH3). In the method, the deposition gases are decomposed by catalytic cracking reactions with a high temperature (1700°C) catalyzer near the substrates, and SiNx films can be deposited at substrate temperatures lower than 400°C without using plasma or photochemical excitation. Nearly stoichiometric Si3N4 films are formed when the flow ratio of NH3 exceeds over 100 times of that of SiH4. These cat-CVD SiNx films show excellent properties. That is, the resistivity, the breakdown voltage, the chemical etch resistance and hydrogen content in the films are almost equivalent to those of high-temperature thermal CVD films. In addition, the surface diffusion length of depositing species is about several-tens μπι and step-coverage itself is conformai. Thus, the cat-CVD SiNx films are regarded not only as a new device passivation films superior to the conventional plasma-CVD films but as a gate insulator for electon devices due to their high quality.
The Applicability of Fluorinated Silicon Nitride Film As Bottom Antireflective Layer In Deep Ultraviolet Lithography
Authors: Byung-Hyuk Jun , Sang-Soo Han , Dong-Wan Kim , Ho-Young Kang , Young-Bum Koh , Byeong-Soo Bae , Kwangsoo No
Published: April 2011

This study describes the use of fluorinated silicon nitride film as a bottom antireflective layer (BARL) material suitable for line-patterning in quarter-micron KrF excimer laser lithography. For the structures of photoresist/BARL (300Å)/c-Si and photoresist/BARL (300 Å )/W-Si at a wavelength of 248nm, 0% reflectance could be achieved when the refractive index (n) and extinction coefficient (k) values of the film are 2.11 and 0.68 or 2.05 and 0.59, respectively. The fluorinated silicon nitride thin films on p-type (100) Si substrates obtained by inductively coupled plasma enhanced CVD have been evaluated with the variations of NF3 flow rates under the two conditions of SiH4:N2=2:15 and 3:20 (seem). The films optical constants and reflectance were investigated by spectroscopic ellipsometry combined with a reflectance simulation program. The film n and k values at 248nm vary in the ranges of 1.67~2.35 and 0.01~0.69, respectively, depending on gas flow ratio of SiH4:N2:NF3. Low reflectance of below 5% can be obtained from reflectance simulation for two deposition conditions with a BARL thickness of 300Å. In addition, the reflectance could be reduced to almost 0% by controlling film thickness. Finally, the antireflective layer performance was investigated using KrF excimer laser lithography.
Oxidation Kinetics Of Crystalline Silicon Oxynitride
Authors: Manessis D. , Du H.
Published: April 2011

Oxidation stability of silicon oxynitride is a property of great technological significance. In this study, the oxidation behavior of stoichiometric polycrystalline Si2N2O was investigated in 1 and 0.5 atm flowing dry oxygen at 1000°‐1300°C. The oxidized Si2N2O samples were characterized using transmission and scanning electron microscopy. The oxidation kinetics were determined using profilometry in conjunction with patterned etching. Oxidation of Si2N2O resulted in the formation of amorphous SiO2. The SiO2‐Si2N2O interface was chemically and structurally abrupt. A parabolic rate law was followed during oxidation with apparent activation energies ranging from 43 to 52 kcal/mol. The relatively high activation energy values compared to that for silicon oxidation suggest that oxidation of Si2N2O is rate‐controlled by a more complex process than molecular oxygen diffusion in amorphous SiO2.
Molecular Dynamics Study Of Si/Si3N4 Interface
Authors: Bachlechner Martina E. , Ebbsjö Ingvar , Kalia Rajiv K. , Vashishta Priya
Published: April 2011

Structural correlations at the Si(111)/Si3N4(0001) interface are studied using the molecular dynamics (MD) method. In the bulk, Si is described by the Stillinger-Weber potential and Si3N4 by an interaction potential which contains two-body (steric, Coulomb, electronic polarizabilities) and three-body (bond bending and stretching) terms. At the interface, the charge transfer from silicon to nitrogen is taken from LCAO electronic structure calculations. Using these Si, Si3N4 and interface interactions in MD simulations, the interface structure (atomic positions, bond lengths, and bond angles) is determined. Results for fracture in silicon are also presented.
Fracture in Silicon Nitride and Alumina thin Films: a Molecular Dynamics Study
Authors: Campbell Timothy J. , Nakano Aiichiro , Omeltchenko Andrey , Kalia Rajiv K. , Vashishta Priya
Published: April 2011

Fracture in thin films of silicon nitride and alumina is investigated with large-scale multiresolution molecular-dynamics (MD) simulations on parallel computers. The simulations for alumina include dynamic charge transfer effects based on electronegativity equalization. Results for structural and dynamic correlations and the effects of temperature and orientation of film on fracture dynamics and morphology of fracture surfaces are presented.
Smart‐Cut® : The Basic Fabrication Process for Unibond® Soi Wafers
Authors: Auberton‐Hervé A.J. , Barge T. , Metral F. , Bruel M. , Aspar B. , Maleville C. , Moriceau H. , Poumeyrol T.
Published: April 2011

The advantage of SOI wafers for device manufacture has been widely studied. To be a real challenger to bulk silicon, SOI producers have to offer SOI wafers in large volume and at low cost. The new Smart‐Cut® SOI process used for the manufacture of the Unibond® SOI wafers answers most of the SOI wafer manufacturability issues. The use of Hydrogen implantation and wafer bonding technology is the best combination to get good uniformity and high quality for both the SOI and buried oxide layer. In this paper, the Smart‐Cut® process is described in detail and material characteristics of Unibond® wafers such as crystalline quality, surface roughness, thin film thickness homogeneity, and electric behavior.
Optical Characterization of Silicon-On-Insulator
Authors: Li G. G. , Forouhi A. R. , Bloomer I. , Auberton-Herve A. , Wittkower A.
Published: April 2011

A new technique, referred to as the “n&k Method”, is used to characterize the thin films comprising Silicon-on-Insulator (SOI). With the “n&k Method”, a non-destructive robust measurement of the thickness of both the crystalline silicon top-layer and the buried oxide under-layer, the spectra of refractive index (n), and extinction coefficient (k), and the smoothness of the interfaces is established. The “n&k Method” determines these quantities simultaneously and without multiple solutions for thickness. The non-destructive measurement of interface roughness between the buried oxide under-layer and the silicon substrate is associated with the presence of silicon islands. The native oxide that forms on SOI is also detected and measured. No initial user's input for thickness and optical constants are required in order to obtain these results. The spectra of optical constants are measured accurately and reliably.
Electron Induced Depassivation Of H And D Terminated Si/Si02 Interfaces
Authors: Devine R. A. B. , Warren W. L. , Vanheusden K. , Mourrain C. , Bouzid M‐J.
Published: April 2011

We have performed electron spin resonance and electrical measurements on SiO2/Si structures subjected to anneals in 5% H2/N2 or 5% D2/N2 gases and subsequently injected with electrons using corona ions and ultra‐violet radiation. Threshold voltage and transconductance measurements have also been made on 0.25 μm metal‐oxide‐semiconductor transistors subjected to 400 °C anneals in the same gases and subsequently aged by hot electron injection. The electrical data on SiO2/Si structures indicates that the density of interface states increases as a result of electron injection but that there are only minor differences between H and D passivated interfaces. The data on Pb, trivalent Si dangling bond, centers at the same interfaces observed by electron spin resonance is insufficiently accurate to enable us to observe any significant differences. The hot electron injection experiments on transistors, consistent with other authors, indicate that, for the limited number of measurements we have made, the transistor ageing resulting from the generation of interface states is significantly reduced for devices annealed in the D containing gas as compared to those annealed in the H containing gas. The origins of some potential differences in annealing behaviour between the SiO2/Si structures and the 0.25 μm transistors are suggested.
Structure of Thermally Grown SiO2 on Crystalline 6H‐SíC
Authors: Tsuchida H. , Kamata I. , Izumi K.
Published: April 2011

The structure of a thermally grown SiO2 film on a crystalline 6H‐SiC substrate was investigated using X‐ray reflectivity and fourier‐transformed infrared attenuated total reflection (FTIR‐ATR). The density, surface roughness and interface roughness of thermal oxide on 6H‐SiC were obtained by X‐ray reflectivity. The TO mode and the LO mode of Si‐O‐Si stretching vibration from the thermal oxide film on 6H‐SiC were obtained from polarized ATR spectra. The local structure of SiO2 film near the SiO2 /SiC interface was discussed from the measurements, and the thermally grown SiO2 film on a 6H‐SiC substrate was found to have a structural transition layer with thickness below 10 nm near the SiO2/SiC interface.
Preparation And Characterization Of Pzt Thin Films On Ruox/Pt Multilayered Electrode By Mocvd
Authors: Kim Tae‐Young , Km Daesig , Chung Chee Won , Lee June Key , Song Inyong
Published: April 2011

Ferroelectric lead zirconate titanate (PZT) thin films have been successfully prepared on a RuOx/Pt multilayered electrode by Metal Organic Chemical Vapor Deposition (MOCVD). The multilayered electrode was introduced to enhance device reliability for FRAM and DRAM applications. The variations in the microstructure and ferroelectric properties of the PZT thin films were investigated as a function of substrate thickness. The microstructure of the PZT thin films was found to have a strong dependence on the surface morphology of the substrate. The control of microstructure resulted in improved ferroelectric properties. The endurance of the Pt/RuOx/PZT/RuOx/Pt capacitor was also maintained up to 1010 cycles without any serious degradation. The ferroelectric capacitors on 4” wafer were integrated by using Inductively Coupled Plasma Reactive Ion Etching (ICP RIE) system and the fully processed MOCVD PZT capacitors showed good ferroelectric properties (Vc=0.57V, ργ=22μC/cm2 respectively).
Structural characterization of different insulating films by spectroscopic ellipsometry and grazing x‐ray reflectance
Authors: Boher P. , Stehle J.L. , Hennet L.
Published: April 2011

Spectroscopic Ellipsometry (SE) and Grazing X‐ray Reflectance (GXR) techniques are applied for different insulating films to determine precisely the thickness and optical indices of the layers. Antireflective coatings for microlithography in the DUV range are first analyzed. In the infrared range the layers are transparent and one can take into account the optical index of the layers by a simple dispersion law. Thicknesses obtained by this method are checked by the GXR technique. Extraction of the optical indices from UV to IR is made very accurately taking into account different SE measurements at various incident angles simultaneously. Amorphous carbon thin films are also analyzed in the same way. The main difference is that the layer is absorbant in the entire wavelength range. In this case, a first characterization by the GXR technique is essential to extract the thickness of the layer. Then the optical indices of the layer can be extracted very accurately by SE.
Nitrided Silicon Oxide Gate Dielectrics for Submicron Device Technology
Authors: Lucovsky G.
Published: April 2011

The research in this paper is based on an approach to low‐temperature/low‐thermal budget device fabrication that combines plasma and rapid thermal processing, and which has been customized to control separately: (i) the N‐atom bonding chemistry and composition profiles, and (ii) the structural and chemical relaxations necessary for device‐quality performance and reliability for stacked gate structures. Control of N‐atom incorporation at the monolayer level at the crystalline‐Si and polycrystalline‐Si interfaces of field effect transistors, and at alloy levels within the bulk dielectrics has been achieved by combining low‐temperature (∼300°C) plasma‐assisted processes to generate the N‐atom concentration profiles, with low‐thermal‐budget rapid thermal annealing (RTA) to promote chemical and structural relaxations that minimize defects and defect precursors.