bluuebunny/crossref_metadata_2025 huggingface dataset:
Surface Structure and Morphology of SrBi2Ta2O9 (SBT) Thin Films
Authors: Li Tingkai , Zawadzki Pete , Stall Richard A. , Peng Chien-Hsiung , Zhu Yongfei , Desu Seshu B.
Published: April 2011

SrBi2Ta2O9 (SBT) films have been prepared by MOCVD processes. The phase formation, surface structure, morphology and surface roughness of SBT films on Pt/Ti/SiO2/Si wafers were measured by XRD, SEM, AFM and ellipsometry. It was found that amorphous SBT formed below 500°C, amorphous and polycrystalline growth occurred successively between 500°C and 650°C. The surface roughness of the SBT thin films also increased with increasing deposition temperature. The AFM results showed the nucleation of SBT started by island formation, then continued across the surface of substrates at lower deposition temperatures. When the SBT film was deposited at higher temperatures, the nucleation and grain growth occurred at the same time, resulting in an inhomogencous structure and much higher surface roughness. Therefore, a two step process is used to improve surface roughness and interface mismatch between film and substrate. In addition, the relationships between surface structure, morphology and the electric properties of SBT thin films were also investigated.
AFM Methodology for the Measurement of Silicon Wafer Microroughness
Authors: Gilicinski A.G. , Beck S.E. , Rynders R.M. , Moniot D.A.
Published: April 2011

Despite the growing use of atomic force microscopy (AFM) for the measurement of silicon wafer microroughness, no generally accepted method has been developed to deal with issues around accuracy and reproducibility. We review problems that affect these AFM studies and demonstrate the effect of probe tip size on AFM microroughness data. Without knowledge of AFM probe tip geometry, it is impossible to quantitatively compare Ra or RMS microroughness data between different measurements. An experimental solution is to characterize tip sizes during imaging and compare data taken with similar size tips. While this will significantly improve quantitation, it is restrictive in that data taken with different size tips cannot be easily compared. We propose a solution to this problem in the use of power spectral density (PSD) to evaluate microroughness with a “cutoff frequency” at the lateral wavelength where tip effects begin to affect the accuracy of the microroughness measurement. An example of this approach is described
Structure Of The Defects Responsible For B-Mode Breakdown Of Gate Oxide Grown On The Surface Of Silicon Wafers
Authors: Mera T. , Jablonski J. , Danbata M. , Nagai K. , Watanabe M.
Published: April 2011

Crystal-originated pits are known as the defects responsible for B-mode Time Zero Dielectric Break-down (TZDB) of the gate oxide grown on the surface of Si wafers. In order to clarify the breakdown mechanism, we have analyzed the structure of those defects formed at the surface of bare and oxidized wafers. In the latter case the analysis has been done both before and after gate oxide breakdown. Electric breakdown has been accomplished by Cu decoration method, recognized as an effective tool for unambiguous detection and positioning of the defects causing B-mode TZDB. As revealed by cross-sectional transmission electron microscopy (XTEM), crystal-originated pits at the bare wafer surface are polyhedral pits having about 5-nm-thick oxide layer on the inner walls. During gate oxidation the thermal oxide is growing faster on the pit walls than on the wafer surface, except for the pit comers where the oxide thinning has been observed. Resulting concave comers of the oxidized pits are suggested to be the weak spots where B-mode TZDB occurs.
Behavior Of Point Defects In CZ Silicon Crystal Growth-Formation Of Polyhedral Cavities And Oxidation-Induced Stacking Fault Nuclei
Authors: Tanahashi K , Inoue N. , Mizokawa Y.
Published: April 2011

The origin of oxidation–induced stacking faults (OSF) and polyhedral cavities in as–grown Czochralski silicon (CZ–Si) crystals is discussed with comparison to the behavior of previously investigated grown–in oxide precipitates. The incorporation, diffusion and reaction in the vacancy, self–interstitial and oxygen ternary system are considered to discuss the origin of grown–in defects.
Positron Beam Technique For The Study Of Defects At The Si/SiO2 Interface Of A Polysilicon Gated MOS System
Authors: Clement M. , Nijs J. M. M. De , Schut H. , Veen A. Van , Mallee R. , Balk P.
Published: April 2011

This work demonstrates that positrons implanted into a 60 nm n-type polysilicon layer with large grains, can be pushed out of this layer by an externally induced electric field. In the case of a metal-oxide-silicon (MOS) system with a such a polysilicon gate, polysilicon-implanted positrons can be efficiently transported towards the SiO2/Si interface where they all are collected. This technique offers new and interesting possibilities to study defects at the SiO2/Si interface of technologically important MOS systems.
True Atomic Resolution Imaging on Semiconductor Surfaces with Noncontact Atomic Force Microscopy
Authors: Sugawara Y. , Ueyama H. , Uchihashi T. , Ohta M. , Yanase Y. , Shigematsu T. , Suzuki M. , Morita S.
Published: April 2011

The constant vibration mode and the constant excitation mode in noncontact atomic force microscopy were compared to investigate the force interaction between tip and surface. As a result, we found that the constant excitation mode is much more gentle than the constant vibration mode. We also succeeded in atomic resolution imaging on InP(110) surface not only in the noncontact region but in the contact region for the first time. Furthermore, we found the discontinuity of the force gradient curve on reactive Si(111)7×7 reconstructed surface. We proposed a model to explain the discontinuity with the crossover between the physical and chemical bonding interaction.
Formation Of Er-Related Donor Centers During Postimplantation Annealing Of Si:Er
Authors: Sobolev N.A. , Aleksandrov O.V. , Shek E.I.
Published: April 2011

Dependence of the donor center concentration, the Er activation coefficient and the nlayer thickness on the implantation and subsequent annealing conditions was studied. A model of formation of donor centers has been developed. The model is based on the interaction of Er atoms with self-interstitials. It describes the dependence of electrical parameters of Er-doped layers on temperature and time of postimplantation annealing.
Cubo-Octahedral B12 Clusters In Silicon Crystal
Authors: Okamoto M. , Hashimoto K. , Takayanagi K.
Published: April 2011

A new stable structure and the electronic structure of boron clusters in silicon crystal have been calculated using the first-principles local density functional approach for Si54B12H60 clusters. According to our calculation, the cubo-octahedral B12 cluster was found to be more stable than the icosahedral one proposed previously. The total energy difference was about 4.6 eV. The analysis of the partial density of states showed that the cubo-octahedral B12 cluster should act as a double acceptor.
Interactions Of Structural Defects With Metallic Impurities In Multicrystalline Silicon
Authors: McHugo S. A. , Hieslmair H. , Weber E. R. , Rosenblum M. D. , Kalejs J. P.
Published: April 2011

Interactions between structural defects and metallic impurities were studied in multicrystalline silicon for solar cell applications. The objective was to gain insight into the relationship between solar cell processing, metallic impurity behavior and the resultant effect on material/device performance. With an intense synchrotron x-ray source, high sensitivity x-ray fluorescence measurements were utilized to determine impurity distributions with a spatial resolution of ≈ lμm. Diffusion length mapping and final solar cell characteristics gauged material/device performance. The materials were tested in both the as-grown state and after full solar cell processing. Iron and nickel metal impurities were located at structural defects in asgrown material, while after solar cell processing, both impurities were still observed in low performance regions. These results indicate that multicrystalline silicon solar cell performance is directly related to metal impurities which are not completely removed during typical processing treatments. A discussion of possible mechanisms for this incomplete removal is presented.
EPR Study Of Defect Formation In H Implanted And Annealed CZ Si
Authors: Pivac B. , Rakvin B. , Corni F. , Tonini R. , Ottaviani G.
Published: April 2011

Structural defects produced in single crystal silicon after hydrogen ion implantation were studied by electron paramagnetic resonance spectroscopy. Samples implanted at 77K show the presence of vacancy clusters that serve as precursors for nanoblister formation upon subsequent thermal treatment. Evolution of vacancy clusters at various stages of thermal annealing show the influence of implanted hydrogen redistribution that passivates the paramagnetic activity in the intermediate temparature range. At still higher temperatures hydrogen outdifluses from the bulk activating remaining structural defects. At these temperatures, formed vacancy clusters gettered oxygen present in the bulk forming, therefore, VxOy complexes. Finally, at temperatures above 700°C vacancy clusters disintegrate completely.
Hrtem Study Of Dislocations In Gesi/Si Heterostructures Grown By VPE
Authors: Liang Jijnwu , Wan Xueyuan
Published: April 2011

GeSi/Si heterostructures grown by atmospheric chemical vapor epitaxy have been studied by cross sectional high resolution transmission electron microscopy (HRTEM). For the first time we have observed an interstitial-type dislocation loop which is located near to a 60° misfit dislocation in the initially prepared GeSi/Si sample. After 30 minutes observation, the interstitial-type dislocation loop disappeared and the 60° dislocation climbed. Moreover, we have observed dissociated 60° dislocations with about 9 nm width of stacking fault existing in silicon substrate.
A New Measurement Method Of Micro Defects Near The Surface Of Si Wafers; Optical Shallow Defect Analyzer (Osda)
Authors: Takeda Kazuo , lshida Hidetsugu , Hiraiwa Atsushi
Published: April 2011

To inspect quality of the surface region (the depth < 0.5μm) of Si wafer, where devices are to be fabricated, a new measurement method named Optical Shallow Defect Analyzer (OSDA) is developed. This method is based on light scattering at two wavelengths having different penetration depths in silicon. The system measures the depth distribution and the size distribution of defects near the surface by comparing intensities of the two scattered lights. The depth resolution of 0.1 μm, the high measuring throughput (total 6“Φ surface area/1hr) and the minimum detectable defect size of 20 nm are achieved. The OSDA is a powerful measurement system for nondestructive quality check of silicon wafers. We first present the data of epitaxial grown-in defects in μm order thickness epitaxial layers about the defect densities, the size distribution and the depth distribution.
Nonradiative Investigation Of Hole Photoionization Spectrum Of EL2 In Semi-Insulating GaAs
Authors: Ikari T. , Fukuyama A. , Morooka Y. , Yoshino K. , Maeda K. , Akashi Y.
Published: April 2011

The piezoelectric photoacoustic (PPA) measurements before and after the secondary light illumination for 3 minutes were carried out at 85 K to investigate the electron and hole photoionization processes of EL2 in carbon concentration controlled semi-insulating (SI) GaAs. The result showed a broad peak around 1.0 eV and a hump up to the band gap energy. These were due to hole and electron photoionization processes of EL2, respectively, and these processes were clearly observed from a nonradiative recombination point of view for the first time. In addition, we found that the hole photoionization process of EL2 is not influenced by the secondary light illumination at low temperature. Although the electron photoionization underwent photoquenching effect upon an illumination of 1.12 eV, the hole photoionization process did not change even after a long period of illumination. The positively charged EL2 donor state may not transform to the metastable state.
Evidence For Non-Correlation Between The 0.15 eV And 0.44 eV Cu-Related Acceptor Levels In GaAs
Authors: Leosson K. , Gislason H. P.
Published: April 2011

We present investigations on the two dominating acceptor levels observed in Cu-diffused GaAs which have frequently been attributed to the two ionization levels of a double CuGa acceptor. We employed plasma hydrogenation and lithium diffusion followed by reverse-bias and zero-bias annealing to passivate and subsequently reactivate the Cu-related acceptor levels. Deep-level current-transient spectroscopy measurements reveal that the two levels are independently reactivated, strongly indicating that they arise from different defects.
Defect Characterization Of InAs Wafers Using Positron Lifetime Spectroscopy
Authors: Mahony J. , Mascher P.
Published: April 2011

Positron lifetime measurements on InAs wafers have shown that the positron bulk lifetime in InAs is 246±2 ps. Most samples exhibit a defect lifetime of 287±6 ps, which is attributable to monovacancy-impurity complexes with a concentration of 7±2×10 16 cm-3. Very heavily doped n-type samples exhibit a defect lifetime of 332–340 ps, characteristic of divacancies. The concentration of these defects is also close to 1017 cm−3. Both types of defects are stable for rapid thermal annealing up to 850 °C, and both defects are neutral. The formation of the divacancytype defects may be correlated with a discrepancy between the carrier concentration and the total
Theory Of 3d Transition Metal Defects In 3C SiC
Authors: Overhof Harald
Published: April 2011

The electronic properties of 3d transition metal (TM) defects located on one of the four different tetrahedral positions in 3C SiC are shown to be quite site-dependent. We explain the differences for the 3d TMs on the two substitutional sites within the vacancy model: the difference of the electronic structure between the carbon vacancy VC and the silicon vacancy VSi is responsible for the differences of the 3d TMs. The electronic properties of 3d TMs on the two tetrahedral interstitial sites differ even more: the TMs surrounded tetrahedrally by four Si atoms experience a large crystal field splitting while the tetrahedral C environment does not give rise to a significant crystal field splitting at all. It is only in the latter case that high-spin configurations are predicted.
Donor Reactivation In Plasma-Irradiated GaAs Under Laser Illumination
Authors: Wada K. , Nakanishi H.
Published: April 2011

Reactivation of Si donors in Ar plasma-irradiated GaAs under reverse bias annealing (RBA) is substantially enhanced by Ar laser illumination. Reactivation occurs only in the surface layer and charge density overshoots its original donor density. These are identical to those observed by high temperature RBA without laser illumination. The activation energy of the reactivation rates is about 0.1 eV, whereas it is about 0.7 eV without laser illumination. The energy reduction is explained by charge state change of deactivators in terms of two hole capturing under minority carrier injection. These findings suggest that deep levels induced by complexes of Si donors with point defects should be present above midgap. The deep penetration mechanism of plasma-induced point defects is discussed, based on the present findings.
Octahedral Void Defects Causing Gate-Oxide Defects In Moslsis
Authors: Itsumi Manabu
Published: April 2011

We found oxide defects originating in standard Czochralski silicon and proposed the sacrificial oxidation method to eliminate these defects in about 1979. Later, N2 annealing and H2 annealing methods were proposed successively, and these three elimination methods have been successfully introduced into actual fabrication lines for highly reliable integrated circuits. However, the origin of the defect was not clarified until recently. We combined copper decoration and TEM in order to observe the origin of the oxide defects and for the first time, observed octahedral void defects systematically at the oxide defects with standard Czochralski silicon. The sizes of the defects are typically 0.1–0.2 microns. These Si-crystalline defects are the origin of oxide defects and, at the same time, may be the origin of crystal originated particles. Recently, we have observed octahedral void defects in the bulk of the standard Czochralski silicon too. Some experimental findings suggest that some impurities on the side wall of the octahedral void defect induce dielectric breakdown of the gate-oxides.
Effect of Fluorine Addition to Plasma-Enhanced Chemical Vapor Deposition Silicon Oxide Film
Authors: Lim S. W. , Miyata M. , Naito T. , Shimogaki Y. , Nakano Y. , Tada K. , Komiyama H.
Published: April 2011

One solution to reduce the time constant of ultra large scale integrated circuit (ULSI) is the use of a low dielectric constant intermetal film like fluorinated silicon oxide (SiOF). We could obtain SiOF films with low dielectric constant as low as 2.6 and good step coverage by adding CF4 to SiH4 and N2O in plasma-enhanced chemical vapor deposition (PECVD) process. To investigate the dielectric constants due to each polarization and the reason for the decrease in the dielectric constant, we used capacitance-voltage (C-V) and ellipsometry measurements, and Kramers-Kronig transformation. The decrease in dielectric constant could not be completely explained by the reduction in ionic and electronic polarization. We could detect silanol groups, Si-OH in the films and their decrease with increasing CF4 flow rate. It is suggested that the main polarization component to decrease dielectric constant is such as orientational polarization. The step coverage of film was improved by adding CF4. It is suggested that the reduction in the sticking probability of films forming species due to the change in surface state improved the step coverage.
Parylene AF-4: A Low εR Material Candidate For ULSI Multilevel Interconnect Applications
Authors: Harrus A.S. , Plano M.A. , Kumar D. , Kelly J.
Published: April 2011

Parylene VIPTM AF-4 dielectric is a potential low εR candidate for ULSI manufacture. The search for new IMD materials with low dielectric constant (k ≤ 2.5) to enable sub 0.18 micron technologies is focusing on new polymers, deposited by either spinning or CVD methods. Two classes of requirements have to be satisfied for a material to be successful, i.e., used in volume device manufacturing. First, a set of physical characteristics have to be met, among the most important are thermal stability above 400 °C, mechanical stability, and good adhesion to a variety of substrates. Then, a second set of more stringent requirements have to be met related to device integration. For example, electrical performance in a device and dry etching for via formation. We report results on the evaluation of Parylene AF-4, deposited by vapor-deposition polymerization of tetrafluoro-p-xylylene. We present data on deposition characteristics, film composition and purity, thermal stability as well as preliminary electrical data.
Low Dielectric Constant Materials for IC Intermetal Dielectric Applications: A Status Report on the Leading Candidates
Authors: Hendricks Neil H.
Published: April 2011

For over two years, intensive efforts at SEMATECH and elsewhere have focused on identifying low dielectric constant (low ε) materials which possess all of the required properties and processing characteristics needed for integration into standard IC fabrication lines. To date, no material candidate has been shown to satisfy this impressive list of requirements. For some candidates, drawbacks related to material properties such as poor thermal stability or electrical performance have been identified; in other cases, problems in process integration, for example difficulties in patterning have stalled progress.

In this paper, most of the current leading candidates for the low ε IC IMC application are identified and discussed. An attempt is made to correlate structure/property relationships in these materials with their relative attributes and deficiencies as they relate to the IMD application. Key differences in chemistry and property/processing characteristics are contrasted for low c silicon-oxygen polymers and for purely organic polymers. Novel dielectrics such as porous organic and inorganic thin films are also discussed in terms of their properties and associated process integration challenges. Since the needs for global planarization and low c IMD are occurring within roughly the same generation of minimum feature size (˜ 0.25 μm), the chemical mechanical polishing (CMP) of low dielectric constant thin films and/or of SiO2 layers deposited above them is briefly discussed. Both subtractive metalization and damascene processes are included, and the required low dielectric constant film properties and processing characteristics are contrasted for each process. Finally, the author's views on future trends in low dielectric constant materials development are presented, with an emphasis on identifying the types of chemical structures which may prove viable for this most demanding of all polymer film applications.
Thermal Curing Conditions for Low K-Fluorinated Polyimide Film for Use as the Interlayer Dielectric in ULSI
Authors: Lee Y.K. , Murarka S.P. , Auman B.
Published: April 2011

The thermal curing (imidization) of the polyimide film has been investigated using DSC and FTIR spectroscopy. The rate and the degree of imidization of the film was found to be dependent on curing temperature, time and thickness. The degree of imidization of the film rapidly increased between 200°C and 350°C and then remained constant for curing above 350°C, indicating that the imidization reaction is complete at 350°C. Also, it was found that imidization proceeds in two stages under isothermal condition, which was characterized by an initial fast imidization step that changes into a second, slower imidization process. The slower imidization rate at the second stage is discussed and explained. Higher degree of imidization was obtained with thicker films because of the higher retention of the solvent in the thicker film. Depolymerization process during thermal curing has also been studied with FTIR. The highest degree of the depolymerization is reached with thermal curing between 225 and 275°C.
Low‐temperature low‐stress silicon nitride for optoelectronic Applications prepared by electron cyclotron resonance plasma Chemical‐vapor deposition
Authors: Belkouch S. , Landheer D. , Taylor R. , Rajesh K. , Sproule G. I.
Published: April 2011

Silicon nitride films have been deposited with a single‐magnet electron‐resonance deposition system using nitrogen and silane as the reaction gases at substrate temperatures of 110°C and 300°C. The films are slightly nitrogen‐rich with no measurable Si‐H bonds measurable by Fourier Transform infrared spectroscopy and the concentration of hydrogen present as N‐H bonds increases with increasing SiH4/N2. The stress levels in the films can be controlled from tensile to compressive by decreasing the SiH4/N2 flow ratio and very low stress can be obtained with N‐H bond concentrations of 4 at. %. The optical bandgap for the layer with the lowest stress value (‐11.5 MPa), deposited at 300°C was 4.9 eV, as determined from a taue plot, and the waveguide loss at 632.8 nm was 2.3 dB/cm for 500 nm thick film deposited on fused silica.
Influence of Nitrogen or Argon Anneals on the Properties of Simox Wafers And Devices
Authors: Cristoloveanu S. , Ionescu A. , Wetteroth T. , Shin H. , Munteanu D. , Gentil P. , Hong S. , Wilson S.R.
Published: April 2011

SIMOX wafers annealed at high temperature in argon or nitrogen ambient are compared in terms of film, oxide, interface, and device properties. This evaluation is conducted by correlating pseudo-MOSFET data in unprocessed wafers with the performance of n- and p-channel transistors. Characterization with the Ψ-MOSFET technique reveals a pile-up of nitrogen near the buried Si -SiO2 interface, where the electron mobility is degraded. MOSFET characteristics are dramatically affected by annealing in nitrogen with large shifts of front and back channel threshold voltages, enhanced leakage currents, and channel doping modification. Nitrogen-induced donors are suspected to be responsible for doping compensation in n-channels (leading to full-depletion mode operation) and overdoping in p-channels. By contrast to argon ambient, which has no major drawbacks, nitrogen ambient can be unsuitable for annealing of SIMOX wafers.
Low Temperature Synthesis of Plasma Teos SiO2
Authors: Itani T. , Fukuyama S.
Published: April 2011

In this study, we investigated the deposition temperature's affect on TEOS based Si02 properties and reaction mechanisms while changing the excitation frequency. We used a parallel-plate plasma reactor, and either 100 kHz or 13.56 MHz radio frequency to generate plasma. We found that 100 kHz plasma promotes SiO formation and improves the film properties at low deposition temperatures. We assume this to be due to the supplement of higher energy ions to the substrate surface in 100 kHz plasma. This in turn promotes the elimination reaction (condensation reaction) of OH that links to Si atoms as a terminator of surface SiO networks or precursor molecules.
In-situ Measurement of Viscous Flow of Thermal Silicon Dioxide Thin Films at High Temperature
Authors: Yu Chia-Liang , Flinn Paul A. , Bravman John C.
Published: April 2011

With a newly constructed high temperature wafer curvature system, we measured significant viscous flow of thermal oxides at temperatures as low as 800°C. In-situ measurements were performed at temperatures between 800°C and 1100°C for wet and dry thermal oxide films of various thicknesses. We found that dry oxides have higher stresses and slower stress relaxation compared to wet oxides grown at higher temperatures. The viscosity of thermal oxide thin films was found to increase with time during relaxation and a structural relaxation process is suggested to explain this phenomenon.
Sol‐Gel Processing and Characterization of Silica Thin Films for on Chip Humidity Sensors
Authors: Kokan J.R. , Gerhardt R.A.
Published: April 2011

Silica thin films have been processed via a colloidal sol‐gel method which involves the hydrolyzing of potassium silicate and colloidal silica sol using formamide[l]. The resulting films are highly porous. The processing leaves residual potassium and sodium in the films which can then be removed through leaching in water. The dielectric properties of films which have been leached for twenty minutes are nearly insensitive to humidity. However, partially leached films, or films which have been doped with LiCl, KC1, or NaCl, are highly sensitive to humidity changes. The range of humidities over which these films have high sensitivity can be modified by changing the dopant type or varying the doping level. Films can be made to sense humidities ranging from 20% to 80% reproducibly. These films are ideal for microelectronic applications because they can be processed via dipping as well as spin coating and can also be easily etched.
Diamond-Like Carbon Film Propertffis From Optical and Electrical Measurements
Authors: Dalton A. , Kosel P.B. , Monreal R. , Frees-carr S. , Weimer J. , Wu R.L.C. , Lanter W.
Published: April 2011

High resistivity diamond-like carbon films have been grown on a variety of substrate surfaces using RF generated high-current hydrocarbon ion beams at low pressures. Stable films have been obtained in the thickness range of 0.3 to 1.2 �m with resistivities exceeding 1013 O-cm. These films have been deposited on smooth surfaces such as oxidized silicon, glass, quartz, aluminum and plastics. The films have smooth surfaces, great hardness and moderate dielectric constant (2.2 to 3.5). Optical absorption measurements show that these films are highly absorbing in the ultraviolet region of the spectrum and in the visible range their absorption coefficients exceed 104 cm-1 and the refractive indices fall in the range 1.75 to 2.17 at 632.8 nm.
Organic Insulating Films at Nanometer Scale
Authors: Vuillaume D.
Published: April 2011

We discuss the electrical and photo-electrical properties of monolayers of long hydrocarbon chains (alkyltrichlorosilane molecules) self-assembled on a silicon substrate. It is shown that these monolayers (<3 nm thick) act as high quality insulators : DC conductivity through the monolayers are in the 10-15 S/cm range, energy barrier heights at the silicon/monolayer interface are in the 45 eV range. Chemical surface modifications of these monolayers are reported in order to tailor their surface as well as electrical (dielectric constant) properties. Possible sub-01 μηι device applications are presented.
Effectiveness of an Inwardly Fired Burner on Abatement of PFCs
Authors: Pierce A.M. , Van Gompel J.
Published: April 2011

A successful method for abating PFC (perfluorinated compounds) emissions from semiconductor manufacture is presented. The method involves use of a novel thermal technique combining an inwardly fired burner with a built-in wet scrubber for removal of combustion products. The Edwards High Vacuum Thermal Processor Unit (TPU) is a Point of Use abatement device designed to destroy PFC and process gases.
An Integrated Approach for the Safe Handling of Hydrides
Authors: Shealy J.R. , Butterfield B. , Emerson D.T. , Whittingham K.L. , Pitts B.L. , Bland R.R.
Published: April 2011

Many semiconductor processes, Organometallic Vapor Phase Epitaxy (OMVPE) in this case, require the use of concentrated hydride sources. The toxicity of many of these compounds (e.g. arsine, diborane) and the pyrophoric nature of others (phosphine and silane) demand that the facility provide both environmental protection and a safe work place. A facility is described which meets stringent environmental emission standards from NY State's Department of Environmental Conservation. The outlined approach also sets new standards for hydride storage and containment, laboratory alarm systems, exhaust gas treatment and dilution, and process integration into the facility. Under normal operation, we demonstrate hydride emissions of less than 10−5 ppb at the exhaust stack.
Anhydrous Hf Processing as an Alternative to Hf/Water Processes
Authors: Staffa J. , Roman P. , Chang K. , Torek K. , Ruzyllo J.
Published: April 2011

The HF/water treatment of silicon surfaces is among the most frequently applied steps in surface cleaning processes. It is utilized for clearing oxides from the silicon surface. Large amounts of ultrapure water are necessary to carry out this operation, both in the HF/water solution itself and the thorough rinse which must follow HF/water processes. Therefore, a gas‐phase alternative to this process would significantly reduce deionized (DI) water consumption. The focus of this paper is the anhydrous hydrofluoric acid (AHF)/alcoholic solvent process which has shown promise as an alternative to the aqueous HF process. In particular, the AHF/methanol process has been studied extensively. This paper presents a comparison between properties of silicon surfaces prepared through the dilute HF/water (dHF) process and those of surfaces prepared through AHF/alcoholic solvent processes.
Growth and Characterization of InAsxP1−x/InP Strained Multiple Quantum Wells by Gas Source Molecular Beam Expitaxy
Authors: Kuo H. C. , Thomas S. , Curtis A. P. , Stillman G. E. , Lin C. H. , Chen H.
Published: April 2011

InAsxPi.x/InP (10 period 50/100Å with x=0.25–0.79) pseudomorphically strained multiple quantum wells (SMQWs) were grown by gas source molecular beam expitaxy (GSMBE) at 470°C and characterized by cross-sectional transmission electron microscope (XTEM), double crystal x-ray diffraction (DCXRD), and optical spectroscopy. The structural analysis demonstrates that excellent control of the sharp interface and limited As-P interdiffusion can be achieved by GSMBE growth. XTEM images of these SMQWs display no misfit dislocations, and DCXRD scans reveal high order superlattice satellite peaks. Photoluminescence (PL) and transmission measurements were performed for all SMQWs to evaluate crystal quality. Only slight degradation in luminescence was observed as the As composition increased. Based on the three-band Kane model which includes the lattice strain, the transition energies of SMQWs were calculated using the conduction-band offset (Qc=δEc/δEg) as an adjustable parameter. The best fit of measured and calculated interband transition energies suggests that Qc is independent of As composition and is 0.70±0.05. Finally, a growth kinetics model based on the Langmuir equation was derived to realize the As/P incorporation ratio in the InAsP materials. Theoretical results show good agreement with experimental data.
Dark Current Reduction in Near Infrared P-I-N Detector Diodes Fabricated from In.75Ga.25As Grown by Molecular Beam Epitaxy on InP Substrates
Authors: Micovic M. , Cai W. Z. , Ren Y. , Neal J. , Nelson S. F. , Mayer T. S. , Miller D. L.
Published: April 2011

We have investigated several approaches to improve the material quality of lattice-mismatched In.75Ga.25As grown by Molecular Beam Epitaxy (MBE) on (100) InP substrates. They include linear grading of In composition from lattice matched In.53Ga.47As to In.75Ga.25As in a 1 μm buffer layer grown at reduced substrate temperature, in combination with various in situ annealing and material regrowth steps. The material was used for fabrication of mesa-structure p-i-n photodetectors with 2.2 μm cutoff wavelength. The room temperature dark current density at 1 V reverse bias was approximately 2 mA/cm2 in all structures that were subjected to anneal and regrowth process, a factor of three improvement over reference samples which were not subjected to annealing and regrowth. The dark current density at 15 V reverse bias (10 mA/cm2 for the best devices) was at least two orders of magnitude lower in all annealed samples than in reference samples. These results suggest that the MBE grown material can be an attractive alternative to the vapor phase epitaxy (VPE) grown material which is commonly used for fabrication of these detectors.
Growth and Characterization of Interfaces in P-Type InGaAs/InP Quantum-Well Infrared Photodetectors with Ultra-Thin Quantum Wells
Authors: Sengupta D. K. , Kim S. , Horton T. , Kuo H. C. , Thomas S. , Jackson S. L. , Curtis A. P. , Bishop S. G. , Feng M. , Stillman G. E. , Chang Y. C. , Liu H. C.
Published: April 2011

P-type InGaAs/InP quantum-well infrared photodetectors operated at 4.55 μm require the growth of ultra-thin (10 Å) quantum wells. We report a study of interfaces in QWIPs grown by gas-source molecular beam epitaxy in which we optimized the group V source supply sequence so that a 6 K photoluminescence linewidth as narrow as 8.4 meV was observed from a structure with 10 Å wells. Analysis of the PL suggests that interface roughness was minimized. Cross-sectional scanning tunneling microscopy, double crystal x-ray diffraction, and cross-sectional tunneling electron microscopy confirmed that high-quality interfaces and uniform layers were obtained. Using the derived structural parameters, photocurrent spectral response was theoretically predicted for these QWIPs and then experimentally verified.
Novel Mid-Infrared Lasers with Compressively Strained InAsSb Active Regions
Authors: Kurtz S. R. , Biefeld R. M. , Allerman A. A.
Published: April 2011

Mid-infrared lasers grown by MOCVD with ALAsSb claddings and strained InAsSb active regions are reported. A 3.8–3.9 μm injection laser with a pseudomorphic InAsSb multiple quantum well active region lased at 210 K under pulsed operation. A semi-metal layer acts as an internal electron source for the injection laser. An optically pumped laser with an InAsSb/InAsP strained-layer superlattice active region was demonstrated at 3.7 μm, 240 K.
Characterization of the CH4/H2/Ar High Density Plasma Etch Process for HgCdTe
Authors: Eddy C. R. , Leonhardt D. , Shamamian V. A. , Holm R. T. , Glembocki O. J. , Meyer J. R. , Hoffman C. A. , Butler J. E.
Published: April 2011

High density plasma etching of Hg1−xCdxTe in CH4/H2/Ar chemistry is examined using mass spectroscopy with careful surface temperature monitoring. The dominant etch products are monitored as a function of surface temperature (15–200°C), ion energy (20–200 eV), total pressure (0.5–5 mTorr), microwave power (200–400 W), and flow fraction of methane in the etch gas mixture (0–30%). In addition, observations are made regarding the regions of parameter space which are best suited to anisotropie, low damage etch processing. These observations are compared with previous results in the form of scanning electron micrographs of etched features for anisotropy evaluation and Hall effect measurements for residual damage. Insights to the overall etch mechanism are given.
Multiple Cations Interdiffusion in In0.53Ga0.47As/In0.52Al0.48As Quantum Well
Authors: Chan Y. , Shiu W. C. , Tsui W. K. , Herbert Li E.
Published: April 2011

Multiple cations interdiffusion in In0.53Ga0.47As/In0.52Al0.48As quantum well (QW) structure is investigated by using the model of expanded form of Fick's second law. The model is fitted to the measured concentration data in order to determine their diffusion coefficients. Once the concentration distribution is obtained, the types of strain and their variation across the QW can be determined, thus the subbands and transitions can be gathered. Result shows interesting phenomena due to this three species interdiffusion.
Phase Modulator Defined by Impurities Induced Disordering
Authors: Lo K. M. , Choy W. C. H. , Li E. H.
Published: April 2011

Optical waveguide type phase modulators defined by impurities induced disordering (IID) are investigated. To achieve a better optical confinement, a two steps ion implantation process is carried out to introduce additional impurities with respect to depth in the cladding region. A more uniform refractive index profile in deeper lateral confined region is obtained after thermal annealing. The refractive index different between the core and cladding can be adjusted by controlling the extension of interdiffusion in the cladding. This provide tuning of single mode operating region. For present IID phase modulator with 25 period of 100Å/100Å Al0.3Ga0.7As/GaAs multiple quantum wells single mode operating at 0.88//m, a normalized phase shift of 362°/Vmm. chirping parameter of 47, and absorption loss less than 120cm−1 are achieved theoretically.
Advances in Ir-Led Technology
Authors: Hovel R. , Woelk E. , Deschler M. , Schmitz D. , Jürgensen H.
Published: April 2011

Due to the world wide demand for IR emitting devices like IR-LED, printhead for laser printers, readout of optical storage devices, serial and parallel fibber/guided wave optical links and free space optical interconnects for remote controllers there is a great interest in multi wafer technology. In this paper we present growth results with respect to IR applications with the Planetary Reactor® system using AlGaAs/GaAs and longer wavelength material. For the mass production of LEDs the Planetary Reactor® system fulfills not only to grow high quality films with excellent uniformities, which results on high yield on wafer, but also to grow with high precursor utilization efficiency and wafer tliroughput. This is proven for thick layers by an excellent growth stability and a thickness uniformity better than ±2%. These high uniformities are achieved at conditions of growth efficiency in the range of 30–50% for group III materials and a comparatively low V-III ratio. To increase the intensity of LEDs GaAs/AlAs Bragg reflectors were grown. Reflectivity characteristics measurement and high resolution X-ray diffractometer measurements confirmed the thickness uniformity in the order of ±1% on 4″ wafers. The excellent thickness uniformity is also achieved on a 9×6″ configuration. For the first time in this study also the 7 × 2″ performance of InP based materials is reported.
No-Phonon and Phonon-Assisted Indirect Transitions in Si1−xGex Single Crystals
Authors: Gerhardt A.
Published: April 2011

The absorption properties of high quality bulk Si1−xGex single crystals (0 ≤ × ≤ 0.16) are studied. Transmission measurements were performed at the indirect absorption edge. The shape of the absorption edge is characterized by structures attributed to the onset of no-phonon and phonon-assisted indirect optical transitions. Threshold energies have been determined using a differential method. A corrected calibration function for the dependence of the excitonic energy gap on composition is presented for the compositions, where x ranges from 0 to 0.16. The presented calibration function can be used for the composition analysis by an optical method. The analysis is independent of absolute transmission values.

A simulation of the absorption spectra by calculations based on second order perturbation theory was used to fit the experimental data This procedure allows to estimate the oscillator strength of the no-phonon transition in dependence on x.
Surface Charge Grating in the Transverse Geometry Holographic Recording Thin Film Devices
Authors: Wang Qingnan , Temple Doyle A.
Published: April 2011

We have used a two-dimensional charge transport model to study edge effects in photorefractive thin films. Our result shows that in addition to the bulk space charges, the large surface charges near the edges make a significant contribution to the space charge field. Quadratic electro-optic material were used as an example to study the surface-charge-layer-field quantitatively. The conditions for the device performance be dominated by either surface charge or bulk trap charges are clearly demonstrated.
GalnAsSb Materials for Thermophotovoltaics
Authors: Wang C. A. , Turner G. W. , Manfra M. J. , Choi H. K. , Spears D. L.
Published: April 2011

Gai1−xInxASySb1-y (0.06 < x < 0.18, 0.05 < y < 0.14) epilayers were grown lattice-matched to GaSb substrates by low-pressure organometallic vapor phase epitaxy (OMVPE) using triethylgallium, trimethylindium, tertiarybutylarsine, and trimethylantimony. These epilayers have a mirror-like surface morphology, and exhibit room temperature photoluminescence (PL) with peak emission wavelengths (λP,300K) out to 2.4 μm. 4K PL spectra have a full width at half-maximum of 11 meV or less for λP,4K < 2.1 μm (λP,300K = 2.3 μm). Nominally undoped layers are p-type with typical 300K hole concentration of 9 × 1015 cm−3 and mobility ∼ 450 to 580 cm2/V-s for layers grown at 575°C. Doping studies are reported for the first time for GalnAsSb layers doped n type with diethyltellurium and p type with dimethylzinc. Test diodes of p-GalnAsSb/n-GaSb have an ideality factor that ranges from 1.1 to 1.3. A comparison of electrical, optical, and structural properties of epilayers grown by molecular beam epitaxy indicates OMVPE-grown layers are of comparable quality.
Formation of Double-Channel Mesa Structure for GaSb-BASED MID-Infrared Laser
Authors: Piotrowska Anna , Guziewicz Marek , Kamińska Ieliana , Papis Ewa
Published: April 2011

Semiconducting antimonide compounds have received increasing attention as the alternative materials for mid-infrared photonic devices, with a variety of applications such as remote sensing, pollution monitoring, and molecular spectroscopy. For many, if not all these devices it is necessary to pattern antimonide films into mesa or line structures. While plasma etching techniques have played an increasing role in producing such features, little was reported until now on dry etching of GaSb- and AlSb-containing alloys. In this paper we present the results of our recent work towards the development of the technology for GaSb-based ridge wave-guide laser emitting at 2–2.3 μm at RT. Specifically, we discuss the fabrication of double-channel mesa structure in AlxGai1−xAsySb1−y/GaSb (x=0.2–0.5) heterostructure materials by RIE technique. The effects of gas and material composition, rf power, pressure and temperature on etching characteristics were studied with special attention paid to surface quality, etching rate and etching profile, which are crucial for obtaining a single mode waveguide. CCI2F2/H2 and CCI4/H2 process chemistries were investigated which shows the latter to provide vertical sidewalls and residue free etch surfaces at controllable etch rates.
MBE Growth and Characterization of InSb/AlxIn1−xSb Strained Layer Structures
Authors: Goldammer K. J. , Liu W. K. , Ma W. , Santos M. B. , Hauenstein R. J. , O'steen M. L.
Published: April 2011

Three types of structures were fabricated using molecular beam epitaxy. High-resolution x-ray diffraction measurements demonstrated the high structural quality of InSb/AlxIn1−xSb superlattices grown on InSb and GaAs substrates. Hall effect data revealed the effect of substrate temperature on autocompensation in InSb δ-doped with Si. Two-dimensional electron systems with a high mobility were realized in InSb quantum wells with AlxIn1−xSb barriers δ-doped with Si.
High Pressure Synthesis of Solid State Materials
Authors: Mcmillan Paul F.
Published: April 2011

Within the ASU MRSEC, we are using a combination of high pressure synthesis techniques (multi-anvil, piston cylinder), combined with in situ studies in diamond anvil cells, and ab initio calculations, to prepare a range of new materials at high pressure, and to study their physical properties under extreme conditions of pressure and temperature. Work in progress includes experiments on nitrides, particularly glasses and crystalline materials based in the P3N5-HPN2-PON system, silicate and germanate perovskites and related vanadates and niobates, and high hardness materials in the B-C-N-0 system. Some of our recent results are presented.
New One-Dimensional Commensurate and Incommensurate Structural Forms of Sr-Co Oxide
Authors: Christoffersen R. , Jacobson A. J. , Hegwood S. L. , Liu L.
Published: April 2011

New forms of Sr-Co oxide with one-dimensional structures related to mixed-layer hexagonal perovskites have been synthesized and characterized by TEM. Crystals of Sr5Co2O12 grown from molten KOH flux and oxidized under slow cooling have structures based on a 3/2 ratio of mixed [Sr3CoO6] and [Sr3O9] layers. This is the first known structure with layers of this type stacked in a non-integer ratio, yielding chains of face-sharing octahedral and trigonal prismatic Co-sites with a 3 + 1 sequence along the c-axis. In oxygen-deficient Sr5Co2O12−x, the {110} structural modulation of the stoichiometric 5:4 phase becomes rotated to an irrational orientation, possibly in association with vacancy ordering, forming an incommensurate superstructure. For the compound Sr6Co5O15, previously known to have a 1/1 ratio of [Sr3CoO6] and [Sr3O9] layers with a 4 + 1 octahedral/trigonal prismatic site sequence, introduction of excess oxygen atoms leads to formation of a commensurate rhombohedral superlattice in which c is doubled relative to the stoichiometric 6:5 phase.
Synthesis of GaSr2Can−1CunO2n+3(n = 2 − 5) Prepared by Solid-State Reaction Method
Authors: Chavira E. , Aguila E. , Baños L. , Navarro O.
Published: April 2011

We present some experimental results of the family of compounds with a general formula GaSr2Can−1CunO2n+3(n = 2,3, 4, 5). This system has been synthesized using the solid-state reaction method at ambient pressure. We have found that the reaction temperature for these compounds is 930±3°C; the samples melt just above this temperature. The powder diffraction data were analyzed assuming a single-phase and the obtained structure is different to the one prepared at high pressure [1,2]. However, comparing the powder patterns we found that the compounds are isostructural to the Al — Sr — Ca — Cu — O system prepared at high pressure [3]. For n = 2,3,4 and 5 a shift of the (105) peak has been observed, which is due to the increases in the number of Ca and Cu — O2 planes in the crystalline structure. Notice that to obtain a single-phase for the above compounds, high pressure is not necessary.