bluuebunny/crossref_metadata_2025 huggingface dataset:
A Study of Step Coverage Morphologies of SiH4-WSix, and SiH2Cl2-WSix for Ulsi Technologies
Authors: Ozkan Cengiz S. , Moinpour Mansour , Li Jian
Published: April 2011

Ultrathin refractory metal silicide films, such as tungsten silicide (WSix) offer a wide range of applications in VLSI and ULSI circuits such as local interconnects, bit lines and wordlines. One practical way of depositing WSix is by a CVD technique in which WF6, is reduced by either silane (SiH4) or dichlorosilane (SiH2 Cl2 ). In this investigation, step coverage characteristics of silane based and dichlorosilane based tungsten silicide films, deposited by low pressure chemical vapour deposition method will be compared. WSix films of various thicknesses (1200–2000 Å) were deposited on topographies created by patterning poly-Si layers. WSix, step coverage was evaluated as a function of deposition temperature, poly-Si layer thickness and poly-Si line spacing. Field emisssion scanning electron microscopy was used to characterize step coverage profiles. It is clearly shown that, silane based WSix films deposited on poly-Si lines with sub 0.5 micron spacings result in poor step coverage which could lead to higher localized stress, cracking and higher line resistance. Dichlorosilane based WSix, on the other hand showed more conformal step coverage, which results in better process marhin for subsequent patterning steps. Finally, it was also observed that, the final silicide profile is highly dependent on the thickness of the underlying poly-Si layer, as well as poly patterning process margin.
Initial Growth and Interface Structure of CdTe Thin Films Grown by MBE on 4° Miscut Si Substrates
Authors: Tsen S.-C. Y. , Smith David J. , Rujirawat S. , Sivananthan S.
Published: April 2011

CdTe thin films with thicknesses in the range of 60˜100 nm have been grown on miscut (001) Si surfaces under different precursors, such as Te and As, with one cycle annealing. The thin-film microstructure was studied in cross section using high-resolution electron microscopy. Atomicresolution images revealed several interesting features of the initial growth of the heteroepitaxial CdTe thin films. With As as the precursor, the films initially grew in three different orientation variants (commonly referred to as domains): (A) CdTe (111)//Si (001) with CdTe (1–10)//Si(110); (B) CdTe (111)//Si (001) with CdTe (11–2)//Si(110), and (C) CdTe (001) // Si (001) with CdTe (110) // Si (110). Each variant has demonstrated its own characteristic defects such as twinning, interface Lomer dislocations and {111} stacking faults. With the [001] growth direction, the CdTe film became defect-free by having about 13° tilt relative to Si [001] such that CdTe (1–11) and Si(−111) planes aligned sideways at the interface. With Te as the precursor, A- and B-type variants were mainly observed. The interfaces were sharper, especially for the A-type interface, but the film adhesion was weaker than when As was the precursor.
Faceting of Stepped Silicon (113) Surfaces: Step Unbinding, Dynamic Scaling, and Nano-Scale Grooves
Authors: Mochrie S. G. J. , Song S. , Yoon Mirang
Published: April 2011

X-ray scattering studies are reviewed of the faceting kinetics of stepped silicon (113) surfaces misoriented towards [001]. Following a quench from the one-phase region of the orientational phase diagram into the coexistence region, initially-uniformly-distributed steps rearrange to form a grooved superstructure. Our measurements reveal the behavior of the grooved surface morphology as a function of time. The surface is found to be self-similar in time, with a characteristic groove size (L) varying as a power-law versus time (t): L = L0tøwith a coarsening exponent of ø = 0.164 ± 0.021 ≃ 1/6, consistent with a theory for the kinetics of faceting which focuses on thermally fluctuating step bunches and their collisions. At later times, the groove size approaches a limiting value which depends on the stepped phase misorientation angle, as expected for faceted surfaces in the case that elastic effects are important.
Atomistic Study of Surface Polarization in Superconducting Perovskites
Authors: Fuks David , Dorfman Simon , Heifets Eugene , Kotomin Eugene , Gordon Alex
Published: April 2011

We simulated the surface relaxation of the cubic perovskite paraelectric SrTiO3 crystal. The atomic positions in ten near-surface layers placed into the electrostatic field of the remainder of the crystal were calculated. Two-dimensional, periodic slab model was combined with the pair potentials treated in terms of the shell-model. Our calculations show that Ti+4, Sr+2 and O−2 ions shift differently from their crystal sites. This leads to a creation of a dipole moment near the surface which might give the paraelectric crystal the ferroelectric properties.
Surface Morphology of Nb Films by Ion Beam Assisted Deposition
Authors: Ji Hong , Was Gary S. , Wayne J. , Moody Neville R.
Published: April 2011

Niobium films of thickness 50 nm to 1000 nm were deposited by ion beam assisted deposition (IBAD) using ion energies of 0, 500 and 1000 eV, and R ratios (ion-to-atom arrival rate ratio) of 0, 0.1, and 0.4 on (100) silicon and (0001) sapphire substrates. The films have columnar structures and the column width increases with normalized energy (En = E × R). The surface morphology depends on both the normalized energy of the ion beam, En, and the film thickness. All films have dome-like surface features that are oriented along the ion beam incident direction. The dimension of these features increases with normalized energy and film thickness. Surface roughness also increases with normalized energy and film thickness, with the root mean square (rms) roughness increasing from 1.6 nm for the PVD sample (100 nm thick) to 36.7 nm for the IBAD film (1000 eV, R = 0.4, 800 nm thick). The surface morphology of IBAD films is the result of a combination of channeling and shadowing effects.
Dark Current Spectroscopy Of Metals In Silicon
Authors: Mccolgin William C. , Lavine James P. , Stancampiano Charles V.
Published: April 2011

Dark current spectroscopy (DCS) is used to identify the signature of metals that generate dark or leakage current in silicon image sensors. Individual metal atoms or defects are detected by DCS on a pixel-by-pixel basis. DCS is applied here to show how the number of electrically active iron atoms in a pixel changes with light and with low-temperature anneals. The measurements explore the dissociation and association of iron-boron pairs and the diffusion of iron near room temperature.
Influence of Si Substrate Crystallinity on Device Performance
Authors: Iwamoto T. , Takano J. , Makihara K. , Ohmi T.
Published: April 2011

We have demonstrated the influence of surface microroughness on the electrical characteristics of MOS devices and investigated the influence of wafer's manufacturing methods, such as Czochralski(Cz), floating-zone(FZ), and epitaxial(Epi) silicon wafers, on the susceptibility to the surface microroughness when some chemical treatment was performed. As a result, it was found that Cz and FZ wafers are very susceptible to the surface microroughness and the amount of the vacancy of Epi wafer is much smaller than that of another wafers. It was also demonstrated that the electrical characteristics of very thin gate oxide films are strongly influenced by the silicon substrate quality. Epi wafer is a strong candidate for fablication of highly-reliable devices on 300mm wafers.
Mechanism Of Defect Reactions In Semiconductors
Authors: Shinozuka Yuzo
Published: April 2011

An overview is presented on mechanisms of electronically induced (enhanced) defect reactions in semiconductors, which are classified into the local heating, the structural instability, and the recombination enhanced. A mechanism for the annihilation of a hydrogen-carbon complex in silicon is given as an example of the second one. The last two mechanisms can be treated in a unified scheme by using the correct configuration coordinate diagram, which enable us to treat correctly the correlation in successive captures of an electron and a hole. The energy conversion mechanism during the reaction is precisely discussed paying attention to the relation between the lattice relaxation mode and the symmetry breaking reaction coordinate.
Defects In Erbium/Oxygen Implanted Silicon
Authors: Duan X. , Palm J. , Zheng B. , Morse M. , Michel J. , Kimerling L. C.
Published: April 2011

A systematic study of defects in the Er/O implanted silicon was conducted using TEM, HRTEM and SIMS. Defect-free material was obtained after the annealing of 400 keV Er+ implanted (100)Si. In sharp contrast, several forms of secondary defects consisting of dislocations, dislocation loops and precipitates were induced upon annealing at different temperatures in the 4.5 MeV implanted (100)Si sample. The isothermal evolution of the defects and reactions between dopants and defects were studied. Oxygen tends to segregate into the dislocation loop zones, where platelet precipitates with habit planes of {111} were found. Following dissociation of oxygen and erbium, plate-like Er precipitates were generated, which are most likely ErSi2 with a habit plane of {111}
Room Temperature Electroluminescence From D1 Dislocation Centers In Silicon
Authors: Sveinbjörnsson Einar Ö , Weber Jörg
Published: April 2011

We report on electroluminescence at room temperature from forward biased n+-p silicon diodes containing high densities (108-109 cm−2) of dislocations at the junction interface. In addition to electroluminescence from band-to-band transitions, we observe a signal arising from the well known dislocation center Dl peaked at ∼1.6 μm (0.78 eV). The Dl electroluminescence intensity at room temperature increases linearly with current density with no observable saturation as long as sample heating is avoided. The quenching of the D l luminescence between 4 K and room temperature is highly sensitive to metal impurities which introduce competitive non-radiative recombination centers. The external power efficiency of the DI electroluminescence was estimated to be of the order of 10−6.
Hall Effect Measurements On SixGe1−x Bulk Alloys
Authors: Mchedlidze T. , Yonenaga I.
Published: April 2011

Carrier transport measurement results for SixGe1−x bulk alloys with 0.03≤x≤0.9, grown by the Czochralski method are presented. Both monocrystalline (x=0.03 and x=0.23) and polycrystalline (x=0.12, 0.25, 0.4, 0.5, 0.75, 0.9) samples were analyzed. In all samples additional charge carriers were created during growth or/and cooling of crystals. With n-type starting materials only alloy with x=0.9 revealed n-type conductivity, all other alloys were of ptype. Creation of acceptors in the SixGe1−x alloy grown by Czochralski method is maximal for 0.4≤x≤0.75.
Residual Impurities And Transport Properties of High Purity Movpe Gaas
Authors: Steude G. , Hofmann D. M. , Drechsler M. , Meyer B. K. , Hardtdegen H. , Hollfelder M.
Published: April 2011

High purity GaAs grown by metal organic vapor phase epitaxy (MOVPE) using nitrogen as a carrier gas has been studied by optically detected cyclotron resonance (ODCR) at microwave and far infrared frequencies. Upon variation of the experimental parameters such as sample temperature, optical excitation density and microwave power the residual ionized (donor) and neutral (acceptor) impurity concentrations can be estimated, they are 2×1012 cm−3 and 5×1013 cm−3, respectively. The luminescence results indicate C to be the dominant residual acceptor. The residual donors were identified as S, Se, Sn from the observation of the internal 1s - 3p×105 cm2/Vs.
Influence Of The Temperature And The Light Intensity On The Metastable Transformation Of EL2
Authors: Alvarez A. , Jimenez J. , Gonzalez M. A. , Chafai M.
Published: April 2011

The temperature dependence of the metastable transformation of EL2 is explained in terms of the thermal emission of holes from the actuator level, VA. A model including the thermal release of holes from this level is presented. The numerical solution allows to account for the low photoquenching efficiency above 80 K in an accurate way. The existence of this level was postulated on the bases of the electric compensation and the temperature dependence of the metastable transformation of EL2 in semiinsulating GaAs. This level allows a complete description of the driving mechanism of the metastable transformation of EL2.
Diffusion Process Of Interstitial Atoms In Inp Studied By Transmission Electron Microscopy
Authors: Ohno Y. , Takeda S. , Hirata M.
Published: April 2011

It is found that interstitial agglomerates are formed uniformly in an irradiated area of InP by annealing at the temperature above 700 K after 200 keV-electron irradiation. TEM observation shows that the number density of interstitial atoms in the agglomerates reached a maximum value when the growth of all the agglomerates stopped. The final density did not depend on annealing temperature but on electron dose, and it increased quadratically with electron dose up to 2×1022 cm−2. In order to explain the experimental results, we have proposed a new model that the agglomerates are formed by thermal diffusion and agglomeration of interstitial-pairs, i.e. Ini-Pi interstitial-pairs. From the analysis, the migration energies for the pairs are estimated to be 1.52 eV. The onset temperature for the diffusion of the pairs is estimated as 550 K.
Electrical And Structural Properties Of LT-GaAs: Influence Of As/Ga Flux Ratio And Growth Temperature
Authors: Luysberg M. , Sohn H. , Prasad A. , Specht P. , Fujioka H. , Klockenbrink R. , Weber E. R.
Published: April 2011

Abstrac

The deposition of GaAs by MBE at low temperatures results in a material of unique properties. However, up to now the control and understanding of the electrical and structural properties are unsatisfactory. To investigate the influence of growth parameters on the formation of point defects and electrical properties, the substrate temperature and the As/Ga flux ratio were systematically varied. In a well defined parameter range the lattice expansion was found to be dominated by the formation of As antisite defects. After annealing a high resistivity is obtained independent of the growth conditions. A strong influence of the growth temperature on the band conduction mechanism is observed, whereas a variation of the As/Ga flux ratio induces only slight changes of the temperature dependence of the conductivity.
Influence Of Donor, Acceptor, And Isovalent Impurity Doping On Arsenic Excess And Point Defects In Low Temperature Grown GaAs
Authors: Chaldyshev V. V. , Kunitsyn A. E. , Faleev N. N. , Preobrazhenskii V. V. , Putyato M. A. , Semyagin B. R. , Tretyakov V. V.
Published: April 2011

We show that in contrast to Si donor and Be acceptor doping, isovalent In impurity doping enhances arsenic excess in the GaAs films grown by molecular beam epitaxy at low temperature. This effect is due to an increase in the concentration of arsenic antisite defects. Gallium vacancy related defects are detected only in the samples annealed at high temperature. Their concentration is found to be higher in the indium-free material than in the indium doped one
S-Doped GaInAs Grown By Chemical Beam Epitaxy: Electrical And Structural Characterization
Authors: Paloura E. C. , Petkos G. , Goodhew P. J. , Theys B. , Chevallier J.
Published: April 2011

We report on the electrical and structural characterization of sulfur (S) doped Ga0.73In0.27As layers, grown on SI (001) GaAs substrates by chemical beam epitaxy. The room temperature free electron concentration is 2×1017cm−3 while the corresponding value of mobility is 3400 cm2V−1 s−1. The epilayer is characterized by a deep trap, which could be attributed to the electrical activity of dislocations, with an activation energy of 0.59 eV and a capture cross section 6×10−15 cm2. TEM analysis shows that the GaInAs/GaAs interface is characterized by dislocation lines and loop-like configurations which could be attributed to climb movement by point defect absorption or emission. Annealing at 420°C (Ar ambient for 5 min) does not alter the carrier concentration (n) and mobility (μ) significantly. The invariance of n and μ, even though the temperature should be high enough to dissociate any Satomic hydrogen complexes, indicates that the number of hydrogen-S donor complexes in the as-grown material is small compared with the donor concentration. Finally, the effect of intentional atomic hydrogen diffusion is discussed.
Deep Centers Influence On Photoresponse Characteristics In High-Resistivity ZnSe
Authors: Korotkov V.A. , Bruk L.I. , Simashkevich A.V. , Gorea O.S. , Kovalev L.E. , Malikova L.V.
Published: April 2011

The photocurrent peak after preliminary optical excitation with specific wavelength in high resistivity (ρ≍1012 Ω∗cm), unintentionally doped ZnSe monocrystals was observed. To study photocurrent “flash” phenomenon, the photocurrent relaxation spectra, photon-capture crosssection (PCCS) spectra and photo-electron paramagnetic resonance (photo-EPR) were investigated. Two-levels model involving the recombination of an S-center and an acceptor A has been developed to obtain the relation between recombination probability and instantaneous photocurrent value. The S-centers ionization energies (1.06eV and 1.14eV from the bottom of the conduction band) and charge carriers life times were determined. The acceptor's positions in ZnSe band gap are equal to 2.05, 2.11, 2.16 and 2.21eV from the bottom of the conduction band. The photocurrent and PCCS “flash” nature as well as complicated photo-EPR are associated with the relaxation of S-centers attributed to Fe ion in the band gap of semi-insulated ZnSe.
The Microscopic Structure Of Shallow Donors In Silicon Carbide
Authors: Spaeth J.-M. , Greulich-Weber S. , März M. , Kalabukhova E. N. , Lukin S. N.
Published: April 2011

The electronic structure of nitrogen donors in 6H-, 4H- and 3C-SiC is investigated by measuring the nitrogen hyperfine (hf) interactions with electron nuclear double resonance (ENDOR) and the temperature dependence of the hf split electron paramagnetic resonance (EPR) spectra. Superhyperfine (shf) interactions with many shells of 13C and 29Si were measured in 6H-SiC. The hf and shf interactions are discussed in the framework of effective mass theory. The temperature dependence is explained with the thermal occupation of the lowest valley-orbit split A1 and E states. It is proposed that the EPR spectra of P donors observed previously in neutron transmuted 6H-SiC at low temperature (<10K) and high temperature (>60K) are all due to substitutional P donors on the two quasi-cubic and hexagonal Si sites, whereby at low temperature the E state is occupied and at high temperature the A1 state. The low temperature spectra are thus thought not to be due to P-vacancy pair defects as proposed previously.
Fluorinated Amorphous Carbon Thin Films Grown from C4F8 for Multilevel Interconnections of Integrated Circuits
Authors: Endo Kazuhiko , Tatsumi Toru , Matsubara Yoshihisa , Horiuchi Tadahiko
Published: April 2011

Fluorinated amorphous carbon thin films (a-C:F) for use as low-dielectric-constant interlayer dielectrics were deposited by helicon-wave plasma-enhanced chemical vapor deposition using fluorocarbon compounds as a source material. The a-C:F films could be grown from C4F8 at a high deposition rate (above 400 nm/min) and they were thermally stable up to 300°C. The addition of bias power to the substrate made it possible to completely fill gaps in the wiring (space 0.35 μm, height 0.65 μm) with the a-C:F film. To protect the a-C:F film during further processing, we deposited a SiO2 film to add mechanical strength and resistance to the oxygen plasma used to remove resist materials. The adhesion between the a-C:F and SiO2 films was dramatically improved by inserting an adhesion promoter consisting of a-C:H and Si-rich SiO2.
Properties of Plasma Oxynitride Films On Strained Sige
Authors: Mukhopadhyay M. , Bera L.K. , Ray S.K. , Maiti C.K.
Published: April 2011

The electrical properties of oxynitride films on strained SiGe grown and deposited, respectively, using a N2O and a combination of N2O and hexamethyldisilazane (HMDS) plasma are reported. X-ray photoelectron spectroscopy (XPS) analysis of the N2O grown films have shown the incorporation of N at the oxide interface without any Ge segregation. The hole confinement in accumulation in SiGe/Si heterostructure with 90 Å N2O oxynitride film has been observed by C-V measurements. Plasma reoxidation of N2O grown dielectric films has resulted in significant improvement of electrical properties. Oxynitride films deposited using PECVD of HMDS have shown comparatively inferior properties. Films deposited from a mixture of N2O and HMDS, exhibit the highest value of Dit (1x1012 cm-2eV-1), probably due to higher amount of nitrogen incorporation at the interface. The charge trapping behavior of both the grown and deposited films have been studied. The effect of addition of NH3 in HMDS plasma and N2O oxidation prior to HMDS PECVD on the charge trapping behavior has been studied.
Characterization of Pecvd Sin Films by Spectroscopic Ellipsometry
Authors: Brierley Steven K. , Nguyen Lan
Published: April 2011

Plasma-enhanced chemical vapor deposition (PECVD) silicon nitride films deposited on both GaAs and Si substrates have been characterized by spectroscopic ellipsometry. The results indicate that such films consist of three constituents: Si3N4, voids, and amorphous silicon (α-Si). In addition, it is also observed that for typical deposition conditions there is an intervening layer of α-Si (on the order of 50–100 Å) between the nitride film and the semiconductor substrate. The thickness of this a-Si layer is found to depend on both the stoichiometry and the growth time of the nitride layer, leading to the conclusion that it is a result of excess Si diffusing from the growth surface through the nitride layer.
Chloroethane Physisorbed on Hydrogenated Si(111): A Test System for the Evaluation of Core Level XPS Assignment Rules at Si/SiO2 Interfaces
Authors: McFeely F. R. , Zhang K. Z. , Banaszak Holl Mark M.
Published: April 2011

We briefly review the controversy concerning the proper methodology for the assignment of soft x‐ray photoemission Si 2p core levels at Si/SiO2 interfaces. Evidence for Second nearest neighbor effects in the photoemission spectra of analogous free molecules in the gas phase are surveyed for the purpose of placing this controversy within a wider context. Physisorption experiments have been performed to inquire whether the second nearest neighbor effects found in free molecules are in any way reduced in their magnitude owing to the proximity to the highly polarizable Si surface. No evidence for such a diminution have been found.
Simulation of Wiring Capacitance For Sub-Quarter-Micron Ulsi Devices and Its Application
Authors: Hasegawa T. , Kobayashi T. , Kadomura S. , Aoyama J.
Published: April 2011

Wiring capacitance in a multilevel interconnecting structure for sub-quarter-micron ULSI devices has been studied using a simulator called SENECA1), which is developed by the Technical University of Vienna and Sony corporation, for optimizing the structure with low dielectric constant materials as interlevel dielectric layers. The simulation results suggest that an optimized structure model should have an ILD(Inter-Level Dielectrics) thickness of 0.7μm and a metal thickness of 0.4μm for sub-quarter-micron ULSI devices. The application of the low dielectric constant materials to the ULSI devices is examined and also discussed with focusing on feasibility and reliability issues. Calculated wiring capacitance is compared with actual capacitance based on the optimized structure. The 33.2% reduction of capacitance is obtained with using an organic film with dielectric constant of 2.4 in excellent accordance with the simulation.
Evidence for Cooperative Oxidation of Mocvd Precursors Used in BaxSr1‐x TiO3 Film Growth
Authors: Glassman Timothy E. , Bhandari Gautam , Baum Thomas H.
Published: April 2011

Metal ß‐diketonate complexes are common precursors for chemical vapor deposition (CVD) of a wide variety of thin‐film materials. Liquid delivery CVD has been used to deposit high dielectric constant materials, such as BaxSr1‐xTiO3.[1] This method relies upon volumetric metering of organic soluble precursors, “flash” vaporization to transport the reactants into the gas‐phase and subsequent thermal decomposition onto the heated substrate. This approach enables the precise control of deposited film stoichiometry. In this study, simultaneous thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) were used to examine the transport and thermal decomposition properties of M(thd)2 (M = Sr, Ba) and Ti(O‐i‐Pr)2(thd)2. In an argon atmosphere, vaporization and transport are observed below 400 °C. In oxidizing atmospheres, such as nitrous oxide and oxygen, decomposition leads to metal carbonate formation as evidenced by both the mass balance and x‐ray diffraction patterns of the residual solids. In the presence of an equimolar amount of the Ti precursor, the formation of carbonates is not observed and oxides are produced at greatly reduced temperatures. Based upon this data, a cooperative oxidation mechanism is proposed which results in “clean” precursor decomposition and BST oxide formation at temperatures near 500 °C.
Comparison of (L)M(thd)2 (M = Mg, Ca, Sr, Ba; L = Tetraglyme, Pmdeta) Precursors for High K Dielectric Mocvd
Authors: Bhandari G. , Glassman T. E. , Studebaker D. B. , Stauf G. , Baum T. H.
Published: April 2011

High-purity alkaline earth ß-diketonate compounds such as [M(thd)2]x (M = Mg, Ca, Sr, Ba) have been utilized for liquid delivery MOCVD.[1] The “parent” compounds are oligomeric species with bridging ß-diketonate ligands and display both limited volatility and thermal instability. To enhance the precursor transport and film growth rates, Lewis base ligands are used to produce mononuclear precursors.[2] Lewis base coordinated metal (ß-diketonates) also exhibit increased solubilities in organic solvents. In this study, two classes of Group II ß-diketonates were compared; thermal stability and transport were evaluated by simultaneous thermal analyses, using both thermogravimetric (TGA) and differential scanning calorimetry (DSC). Liquid delivery and vaporization were evaluated in an “experimental” liquid delivery system and preliminary film growth, including electrical film properties were measured. The identity of the Lewis base and Group II precursor molecular structure as relates to liquid delivery vaporization and CVD film growth of BaxSr1–xTiO3 are described.
Atomic Bonding in Amorphous Alloys Based on Carbon, Nitrogen, and Hydrogen: A Thermodynamic Approach
Authors: Efstathiadis H. , Akkerman Z. , Smith F. W.
Published: April 2011

A thermodynamic model previously outlined for the prediction of the bonding in amorphous hydrogenated carbon-nitrogen alloy films (a-CxNyHz), is extended here to include the effects of enthalpy and entropy. Predictions are presented for the bonding of tetrahedral C(sp3), trigonal C(sp2), pyramidal N(sp3), and trigonal N(sp2) atoms in the alloy as well as the bonding of H to these atoms. When bond energies alone are considered, it is predicted that typical a-CxNyHz films will undergo a phase separation into graphitic regions containing C(sp2) atoms, and C(sp2)-N(sp3)-H groups, and diamond-like or polymeric regions containing only C(sp3) and H atoms. When the effects of entropy are also included, phase separation is eliminated and C(sp3)-C(sp2), C(sp2)=N(sp2), and C(sp2)-N(sp2), bonds are also predicted to be present. The model predictions are compared with experimental results for typical amorphous a-CxNyHz alloys that have been prepared via plasma-enhanced chemical vapor deposition from mixtures of nitrogen and acetylene. In a film with y=0.07 the carbon atoms sp3/sp2 ratio is predicted to be 0.7, while 80% of N atoms are predicted to be trigonal N(sp2) atoms.
Comparison of Gate Oxide Processing Techniques for Thin Dielectric Films
Authors: Schay Pat , Lin Fuyu , Ajuria Sergio , Stih John
Published: April 2011

This paper focuses on establishing a baseline for thin dielectric processes including: low temperature, dilute, stacked (TEOS), oxynitride, and high temperature annealed (grow‐anneal‐grow) oxidation. 105Å (total thickness) gate dielectrics were grown or deposited for this study. The stack oxide showed the highest Vbd yields for both large‐area and edge‐intensive capacitors, but the poorest Qbd. The N2O oxide yielded mediocre Vbd and Qbd. The low temperature and dilute oxides showed early breakdowns, but acceptable Qbd. 900°C thermal gate oxide showed slightly better average Vbd than low temperature and dilute oxides but comparable Qbd. The high temperature annealed oxide appears to have the best electrical performance, but the worst uniformity.
Measurement of Arsenic Emission from Doped Czochralski Silicon Crystal Growing Operation
Authors: Sinha D. , Carlson C. , Homyak Andy , Hunter Elias
Published: April 2011

The level of arsenic from the effluent of a crystal grower was measured at different phases of the silicon crystal growth operation which includes arsenic doping, crystal body growth, burn‐in, and post burn‐in periods. Measurement of arsenic levels were made in the discharge water used as the sealing liquid for the liquid ring vacuum pump used for process effluent discharge. Gas phase measurements were also performed for both particulate arsenic as As2O3 as well as for compounds of arsenic in vapor phase as AsH3. Results of these analyses provided important information for developing strategy for emission treatment and control, reducing arsenic exposure to personnel and evaluating the feasibility for recycling argon used in the crystal growing process.
An Integrated Chemical-Microbiological Approach for the Disposal of Waste thin Film Cadmium Telluride Photovoltaic Modules
Authors: Paknikar K. M. , Rajwade J.M. , Pethkar A. V. , Goyal D. J. , Bilurkar P.G. , Mate N. V.
Published: April 2011

The paper describes a novel chemical-microbiological method for the selective removal of cadmium, tellurium and silver from the thin film CdTe photovoltaic modules. The chemical component of the process utilizes dissolution of metals with nitric acid. The metal solution is subjected to selective biosorption of silver and cadmium by passing through biosorbent columns. The adsorbed cadmium and silver are desorbed and recovered by chemical precipitation. Tellurium in solution coming out of the biosorbent columns is converted microbiologically to its metallic form in a bioreactor. The combined chemical-microbiological treatment ensures recovery of silver, cadmium and tellurium with 86%, 80% and 99% efficiency, respectively. The treated waste can be discharged safely in the environment.
Next Generation Processes and Equipment that Lead to Positive Environment, Safety, and Health Impacts
Authors: Pei Phyllis , Kerby H. Ray
Published: April 2011

The technology development needed to support the continuous improvement of Environment, Safety, and Health (ESH) characteristics of semiconductor manufacturing facilities is changing as strategies for source reduction and incident prevention and more refined schemes for assessing ESH improvement emerge. This paper summarizes the changes taking place in ESH management structure and focuses on examples of current technology development to satisfy the new model of ESH execution.
Infra-Red Tunneling Absorption in Semiconductor Double Quantum Wells in Tilted Magnetic Fields
Authors: Lyo S. K.
Published: April 2011

Using a linear response theory, interwell-tunneling absorption of infra-red photons is calculated in a double-quantum-well structure with a wide center barrier in tilted magnetic fields. Tunneling occurs between the ground sublevels of the two quantum wells, with an energy difference that is tunable. The absorption intensity depends strongly on the temperature and the carrier densities. The resonance width is narrow even at high temperatures due to the two-dimensional phase restriction for tunneling. In magnetic fields, both the in-plane and perpendicular components of the field sensitively control and tune the absorption lineshape in very different ways, affecting the absorption threshold, the resonance energy of absorption, and the linewidth.
Resonant-Cavity Infrared Devices
Authors: Pautrat J. L. , Hadji E. , Mula G. , Bleuse J. , Magnea N.
Published: April 2011

The CdxHg1−x Te compounds are well suited to the design of semiconducting devices incorporating an optical microresonator since they display a wide variation of bandgap and refractive index with composition x, while the lattice parameter remains practically unchanged. It is then possible to create a specific optical function by stacking high quality pseudomorphic layers on a crystalline substrate.

Microcavities resonating in the 3–5 μm range have been made by growing a lower Bragg mirror (10.5 periods) and a nominally undoped cavity medium containing a 50 nm active layer (CdTe-HgTe pseudo-alloy). The upper mirror is a gold layer deposited on the cavity. The emission of these Resonant Cavity Light Emitting Diodes has been observed in the 3–4.5 μm range up to room temperature. It coincides with the cavity resonance mode (linewidth 8 meV). With the addition of a ZnS/YF3 upper mirror, a Vertical Cavity Surface Emitting Laser at 3.06 μm has also been demonstrated.

The microcavity concept appears to be very useful for designing new devices for the 3–5 μm range.
Spectroscopic Ellipsometry Study of HgCdTe Epilayer Surfaces During Electron Cyclotron Resonance Plasma Etching
Authors: Johnson J. N. , Dinan J. H. , Singley K. M. , Martinka M. , Johs B.
Published: April 2011

Spectroscopie ellipsometry has been used to monitor optical characteristics of HgCdTe surfaces during plasma etching in an electron cyclotron resonance reactor. Commonly used process conditions were found to induce changes in the ellipsometric parameters Δ and φ. A model was constructed to account for these changes in terms of process-induced roughness and mercury depleted sub-surface layers An independent characterization of the near-surface region was earned out ex situ after etching using Auger spectroscopy and x-ray photoelectron spectroscopy. Plasma process parameters were varied to isolate their influence on surface conditions and a set of parameters is given for which changes are minimized.
InAsSb/InAlAsSb Quantum-Well Diode Lasers Emitting Between 3 and 4 μm
Authors: Turner G. W. , Choi H. K. , Manfra M. J. , Connors M. K.
Published: April 2011

Recently, mid-infrared diode lasers fabricated from the antimonide-based III-V compounds have been receiving increased attention for potential applications in trace gas detection, spectroscopy, pollution monitoring, and military systems. In this paper we will report the growth, fabrication, and modeling of high performance diode lasers with wavelengths longer than 3 μm. Molecular beam epitaxy (MBE) has been employed for the growth of these Type-I, strained quantum-well (QW) laser structures on GaSb and InAs substrates. The lasers consist of compressively strained InAsSb wells, tensile-strained InAlAsSb barriers, and lattice-matched AlAsSb cladding layers. QW lasers grown on GaSb substrates, with emission wavelengths of ∼3.9 μm, have operated pulsed up to 165 K. At 80 K, cw power of 30 mW/Facet has been obtained. Ridge-waveguide lasers have operated cw up to 128K. QW lasers grown on InAs substrates have emission wavelengths between 3.2 and 3.55 μm. Broad-stripe lasers on InAs have exhibited cw power of 215 mW/facet at 80 K, pulsed threshold current density as low as 30 A/cm2 at 80 K, characteristic temperatures (TO) between 30 and 40 K, and maximum pulsed operating temperature of 225 K. Ridge-waveguide lasers on InAs have cw threshold current of 12 mA at 100 K, and a maximum cw operating temperature of 175 K. In this paper we will present some of the key issues regarding the MBE growth, fabrication, and modeling of such lasers and discuss future directions for improved device performance.
Composition of the Equilibrium Vapor Phase Over ZnGeP2 and Thermal Stability
Authors: Rechter S. , Kurzweil A. , Castleberry R. H. , Bachmann K. J.
Published: April 2011

ZnGeP2 can be transported by chemical vapor transport (CVT) using phosphorus or ZnP2 as transporting agent. Since germanium has a seven order of magnitude smaller partial pressure than zinc and phosphorus solely the formation of a volatile GePy (y≥l) species can explain the CVT-growth which was observed in a temperature range from 973 to 1573 K. To stabilize this species phosphorus pressures in the bar range are needed. Using absorption spectroscopy to analyze the equilibrium vapor phase composition over P, GeP and ZnGeP2, absorption lines were found adjacent to P2 band heads in the wavelength range from 180 to 260 nm which were addressed as band heads of an unknown GePy species. Quadrupole mass spectroscopy (QMS) measurements revealed that this species is not stable at lower pressures decomposing presynthesized GeP and ZnGeP2 in a Knudsen cell. In the temperature range from 550 to 800 K at total pressures of 10−7 to 10−6 mbar, ZnGeP2 decomposes into Zn and P4 whereas Zn is the dominant gas phase species. Under vacuum ZnGeP2 starts to decompose at 600 K while in a N2 atmosphere decomposition occurs at 923 K. By adding ZnP2 (5mg/cm3) to polycrystalline ZnGeP2, which was placed in an evacuated and closed quartz glass ampoule, red transparent crystals were yielded in a temperature gradient ΔT= 1073–1023 K.
Integrated All-Optical Devices Fabricated Using Area-Selective Disordering of Multiple Quantum Well Structures
Authors: LiKamWa Patrick , Kan'an Ayman , Dutta Mitra , Pamulapati Jagadeesh
Published: April 2011

We describe a method of silicon oxide capped disordering of GaAs /AlGaAs multiple quantum wells (MQW) and its application to the fabrication of passive waveguides integrated with nonlinear switching sections. The silicon oxide cap in this work was formed by spinning a solution of glass forming compound and curing it. The characteristics of the disordering process has been studied by monitoring the shift of the photoluminescence as a function of rapid thermal annealing temperature and fitting the n=1 electron heavy-hole level to that calculated from an error function diffusion profile. Our results indicate a Ga-Al inter-diffusion constant of 8×10−16 cm2s−1 at 980°C and an activation energy of 4.4eV which is similar to values reported by other researchers.

The disordering process is then used to define selected areas of disordered and non-disordered MQWs and ridge waveguide structures were fabricated by conventional photolithography and wet chemical etching. Two structures have been studied. One is the nonlinear zero-gap directional coupler with disordered input and output branching waveguides, and the other is the symmetric nonlinear integrated Mach-Zehnder interferometer with one arm containing a non-intermixed MQW section. The devices investigated using a pump-probe set-up, exhibited strong all-optical switching behavior with a contrast ratio of 15:1.
LPE Growth of Mixed Composition HI-V “Virtual Substrates” for MID-Infrared Optoelectronic Devices
Authors: Mao Y. , Krier A.
Published: April 2011

Liquid phase epitaxy can be effectively used to grow a thick graded ternary or quaternary buffer layer to provide a “virtual substrate” for subsequent device epitaxy. Grading characteristics of InGaAs, InAsSb and InAsSbP epitaxial layers grown by LPE are discussed. The effects of the principal LPE growth parameters on epiiayer thickness, surface morphology and composition, lattice-mismatch and photoluminescence efficiency were investigated and are described.
Optical Characterization and Mapping of Four INCH InSb Epitaxial thin Films Grown on GaAs by Turbo Disk Metalorganic Chemical Vapor Deposition
Authors: Feng Z. C. , Beckham C. , Schumaker P. , Ferguson I. , Stall R. A. , Schumaker N. , Povioski M. , Whitley A.
Published: April 2011

A large number of 4 inch (100 mm) diameter 1–2 μm thick InSb films have been grown on GaAs by low pressure metalorganic chemical vapor deposition (MOCVD) turbo disk technology. Raman scattering microscopy was used to study the effects of III-V source ratios on the film crystalline quality and to optimize the growth parameters. Multi-point Raman measurements over the entire 4” wafer were performed to exhibit the uniformity distribution of the film crystalline quality. A FTIR reflectance mapping system has been established to map the film thickness distribution. Good uniformity of the film thickness and crystalline perfection was obtained. Raman and FTIR are showing useful tools for non-destructive characterization of large area wafers for industrial mass production.
Hydrothermal Synthesis of Novel Vanadium Oxides
Authors: Stanley Whittingham M. , Boylan Elizabeth , Chen Rongji , Chirayil Thomas , Zhang Fan , Zavalij Peter Y.
Published: April 2011

Extending our prior work on tungsten and molybdenum oxides, we have found that a wide variety of vanadium oxides can be prepared using hydrothermal methods. These include a number of layer compounds as well as cluster complexes. The starting reaction medium usually contained vanadium pentoxide, an alkali containing compound such as LiOH, an organic template such as tetramethylammonium, and the pH of the whole was controlled by the addition of acid. Reaction temperature was 150°C to 200°C, and time was up to 3 days. A new lithium vanadium oxide, which has the simplest structure of any layered vanadium oxide, was formed. The lithium could be readily removed leading to a new form of vanadium dioxide. This vanadium oxide was also capable of intercalating a variety of other ionic and molecular species. Several other new vanadium oxides containing the TMA cation were also formed; one of these TMAV3O7 readily absorbed oxygen to form TMAV3O8. Addition of zinc or iron to the reaction medium caused the formation of layer structures containing double V2O5 layers; for iron the TMA was retained in the structure whereas for zinc the TMA was excluded. Changing the organic entity resulted in other new structures, for example methylamine and dimethylamine gave tetragonal structures.
Synthesis and Structure of a Metal-Organic Solid Having the Cadmium(II) Sulfate Net
Authors: Yaghi O. M. , Li Hailian , O'Keeffe M.
Published: April 2011

Reaction of silver(I) nitrate and hexamethylenetetramine (HMTA) gives crystals of Ag2(HMTA)(NO3)2, which was formulated by elemental microanalysis and a single crystal x-ray study. Its Ag2(HMTA) open-framework is the first example of a decorated CdSO4net. The relative orientation of the tetrahedral HMTA building blocks in this structure point to numerous opportunities toward constructing novel chiral and polar porous frameworks.
Hydrothermal Synthesis of Vanadium Oxides
Authors: Chirayil Thomas , Zavalij Peter , Stanley Whittingham M.
Published: April 2011

The pH of the reaction media is a critical factor in the formation of new vanadium oxides with the tetramethylammonium (TMA) ion via the conventional hydrothermal method. New vanadium oxides; TMAV3O7, Li0.6V2−δO4−δ·H2O and Li0.6V2−δO4−δ, TMAV4O10, and two more new vanadium phases with d spacings of 11.5Å and 19.1Å are formed as the pH is varied with acetic acid. The synthesis and characterization of TMAV3O7, a new vanadium oxide with tetramethylammonium ions residing between its layers is discussed. The intercalation of alkylamines, DMSO, and water into Li0.6V2−δO4−δ·H2O is described. Microwave hydrothermal synthesis is a new and alternate soft chemistry technique used to accelerate the synthesis of TMAV4O10. This method also aided in the formation of a new cluster compound, [Li(H2O)4]2TMA(V10O28)·4H2O.
Nonstoichiometry and Doping of Zinc Oxide
Authors: Sleight Arthur W. , Wang Ruiping
Published: April 2011

Contrary to the commonly accepted model, we conclude that the zinc interstitials in Zn1+xO are not ionized. Instead, the electron pair associated with the interstitial zinc is trapped in a metal—metal bond. The increase in conductivity on initial reduction of zinc oxide is associated with impurities such as silicon which are compensated by extra oxygen unless removed by reduction. Zinc oxide powders and thin films were prepared with the dopants B, Al, Ga, In, and Ge. By using high temperatures and highly reducing conditions, conductivities 1000 times higher than previously reported for powders were obtained for some of our powders.
Layered CMR Manganites: Structure, Properties, and Unconventional Magnetism
Authors: Mitchell J. F. , Argyriou D. N. , Potter C. D. , Jorgensen J. D. , Hinks D. G. , Bader S. D.
Published: April 2011

Neutron powder diffraction studies of the layered compounds R1.2Sr1.8Mn2O7, (R = La,Pr, Nd), RSr2Mn2O7 (R = Pr,Nd),and La1.4Sr1.6Mn2O7 show that the degree of distortion of the MnO6 octahcdra do not correlate with the appearance of a metal-insulator (MI) transition in these compounds. Instead, the in-plane Mn-O bond length appears to be a better indicator of the electronic behavior. Detailed bulk magnetization studies on single crystal La1.2Sr1.8Mn2O7 show thai there are three magnetic regimes as a function of temperature: paramagnetic insulator, short-range ordered (SRO) fcrrromangct, and long-range ordered (LRO) fcrromagnct. Scaling analysis indicates that a 2D finite-size XY model is an appropriate description of the magnetic state in the SRO regime.
Lithium Doping in La2CuO4 and La2NiO4
Authors: Sarrao J. L. , Torelli M. E. , Fisk Z.
Published: April 2011

We have studied the effect of hole doping via Li substitution in La2CuO4 and La2NiO4. The response to hole doping of the Ni (S=1) sublattice is distinct from that of the Cu (S=1/2) sublattice. These effects are seen most clearly for La2Cu0.5Li0.5O4 and La2Ni0.5Li0.5O4 in which the Li ions form an ordered superlattice. It appears that Ni is in a low-spin d7 configuration whereas Cu is in a d9-ligand “Zhang-Rice” configuration. Despite this difference, the response of both La2CuO4 and La2NiO4 to hole doping is surprisingly independent of whether Sr (which substitutes out of plane for La) or Li (which substitutes in the plane for Cu/Ni) is used as the dopant.
Layered 3-D Ferromagnets and Antiferromagnets, M2+(ReO4)2 (M = Mn, Fe, Co, Ni, Cu): Importance of Dipolar Interactions
Authors: Torardi C. C. , Reiff W. M. , Dodrill B. C. , Vogt T.
Published: April 2011

Powder samples of the anhydrous compounds M2+(ReO4)2 (M = Mn, Fe, Co, Ni, and Cu) were prepared. All have trigonal symmetry, except M = Cu which is Jahn-Teller distorted to monoclinic symmetry, I2/m. Single crystals of the Fe and Cu compounds were grown by vapor transport and their layered structures determined. Ferromagnetism, deduced from ac susceptibility and dc magnetization studies, is exhibited by the Fe (TCurie = 8.5 K), Co (TCurie = 4.7 K), and Ni (TCurie = 12.5 K) phases. They show 2-D ferromagnetic (intralayer) interactions as well as a 3-D ferromagnetic (interlayer) ground state with both of these effects obvious in the heat capacity of Ni(ReO4)2. Low-temperature powder neutron diffraction confirms the ferromagnetism of Ni(ReO4)2 below 12 K, and also reveals a structural phase transition occurring between room temperature and 77 K. The origin of the 3-D ferromagnetic ground states of the Fe, Co, and Ni perrhenates is the result of dipolar interlay er interactions, as opposed to superexchange between the layers. Susceptibility results of the Cu perrhenate indicate intralayer ferromagnetism and any long-range 3-D order occurring at T ≤ 1.5 K. The Mn compound is antiferromagnetic.
Consequences of Fluorine Atom Bridging and Increasing Metal Atom Spin Density for the Low Temperature Magnetism of the Series. Na3[FeF6],[NH4]3[FeF6], [Co(NH3)6][FeF6] and [NH4CoFeF6]
Authors: Reiff W. M. , Kweicien M. J. , Subramanian M. A.
Published: April 2011

Aspects of the low temperature magnetism of some distorted cryolite-like compounds of high-spin iron III, namely Na3[FeF6], [NH4]3[FeF6] are presented. The behavior of these systems is compared to iron-57 Mössbauer spectroscopy and ac-susceptibility results for the related [Co(NH3)6][FeF6] and the modified pyrochlore [NH4CoFeF6] obtained via thermolysis of [Co(NH3)6][FeF6] under nitrogen.