bluuebunny/crossref_metadata_2025 huggingface dataset:
Surface Oxidation Mechanisms of Molybdenum Disilicide in High-Temperature Combustion Environments
Authors: Lin Wen-Yi , Speyer Robert F.
Published: March 2011

The stability of MoSi2 was studied at 1600°C in combustion products with an incoming gas to air ratio of 1:6.7 and compared to results in a 1:10 environment. Oxidation was investigated using periodic weight measurements and characterization using XRD, SEM, and EDS. Passive oxidation was observed; MoSi2 was oxidized by H2O and CO2 to form Mo5 Si3 and SiO2. The amorphous silica product formed a surface layer and reduced the oxidation rate as it coarsened. MoO3(g) did not form which was in agreement with the thermodynamic (SOLGASMIX-PV) prediction that it would only form in the presence of molecular oxygen. A good agreement was observed between the measured and calculated weight gains based on the surface layer thickness.
Characterization of Structure and Mechanical Properties of MoSi2-SiC Nanolayer Composites
Authors: Kung H. , Jervis T. R. , Hirvonen J-P. , Nastasi M. , Mitchell T. E.
Published: March 2011

A systematic study of the structure-mechanical properties relationship is reported for MoSi2-SiC nanolayer composites. Alternating layers of MoSi2 and SiC were synthesized by DCmagnetron and if-diode sputtering, respectively. Cross-sectional transmission electron microscopy was used to examine three distinct reactions in the specimens when exposed to different annealing conditions: crystallization and phase transformation of MoSi2, crystallization of SiC, and spheroidization of the layer structures. Nanoindentation was employed to characterize the mechanical response as a function of the structural changes. As-sputtered material exhibits amorphous structures in both types of layers and has a hardness of 11GPa and a modulus of 217GPa. Subsequent heat treatment induces crystallization of MoSi2 to form the C40 structure at 500°C and SiC to form the a structure at 700°C. The crystallization process is directly responsible for the hardness and modulus increase in the multilayers. A hardness of 24GPa and a modulus of 340GPa can be achieved through crystallizing both MoSi2 and SiC layers. Annealing at 900°C for 2h causes the transformation of MoSi2 into the Cllb structure, as well as spheroidization of the layering to form a nanocrystalline equiaxed microstructure. A slight degradation in hardness but not in modulus is observed accompanying the layer break-down.
Electrochemical Protection of Molybdenum and Molybdenum Disilicide in Molten Soda-Lime-Silicate Glass Environment
Authors: Sundaram S. Kamakshi , Speyer Robert F.
Published: March 2011

Electrochemical corrosion of Mo and MoSi2 in a molten soda-lime-silicate glass environment was studied using a two electrode cell with Pt as the counter electrode. XRD, SEM, and EDS were used to characterize the corroded specimens. When Mo was given a cathodic bias (∼ 0.8V), the specimen surface oxidized to MoO2(s). With reverse bias, Mo ions were interpreted to have been removed into the glass melt. For MoSi2, Mo5 Si3 interfacial layers were observed for both cathodic and anodic corrosion. Mo5 Si3 debris particles (∼4 µm) were seen floating into the glass en masse under a cathodic bias, but not when the bias was reversed. This was interpreted to be a result of an inherent negative charge of debris particles.
Microstructural Evolution in Compositionally Tailored MoSi2/SiC Composites
Authors: Riddle S.E. , Jayashankar S. , Kaufman M.J.
Published: March 2011

Compositionally tailored MoSi2/SiC composites with silicon carbide content ranging from 0 to 60 volume percent were synthesized through a novel processing scheme involving the mechanical alloying of elemental molybdenum, silicon, and carbon. The effects of important processing parameters such as the nominal powder composition and the processing temperature on the microstructural evolution during mechanical alloying and subsequent heating are described based on the results obtained from DTA and XRD.
Effect of Deformation Processing on Mechanical Properties of Nb-10 a/o Si In-Situ Composite
Authors: Weiss I. , Thirukkonda M. , Srinivasan R.
Published: March 2011

Nb-10 a/o Si alloy is an in-situ composite. The microstructure of the cast alloy consists of pro-eutectic Nb dendrites distributed in a matrix of eutectic Nb3Si + Nb phases. The microstructure of the as-cast alloy was modified by multiple hot extrusions producing an oriented composite. Extensive grain size refinement occurred in both the Nb and Nb3Si phases. The ductile primary (pro-eutectic) Nb particles were aligned along the extrusion direction. Bend strength and fracture toughness measured by three point bend and four point bend tests, respectively, showed that both the yield strength and fracture toughness of the alloy increases considerably following this thermomechanical processing. These improvements have been attributed to the changes in size, morphology and spacing of the constituent phases and their microstructural refinement.
Influence of Tungsten Alloying Additions on the Mechanical Properties and Texture of Tantalum
Authors: Gray G.T. , Bingert S.R. , Wright S.I. , Chen S.R.
Published: March 2011

Tantalum, like all bcc metals, exhibits deformation behavior which is substantially influenced by alloying, temperature, and strain rate. Recently, the mechanical response, in particular the highstrain- rate response, of tantalum and tantalum alloys has received increased interest for ballistic applications. In this paper, recent results on the influence of tungsten alloying additions on the mechanical response and starting crystallographic texture of tantalum-tungsten alloys are presented. The stress-strain behavior of three tantalum alloys containing 2.5, 5, and 10 wt.% W has been investigated as a function of loading path, tension and compression, and strain rate, 10−3 to 8000 s−l The yield strength and work-hardening rate were found to increase with increasing tungsten alloying content compared to unalloyed-Ta. Based on measurements of the surface and centerline textures of the Ta-W alloys, no systematic effect of tungsten content on texture was documented. However, due to variations in mechanical behavior between through-thickness and in-plane properties the need for complete through-thickness texture measurements is indicated.
The Effect of Deformation and Reinforcement Particles on the Grain Growth Behavior of MoSi2
Authors: Basu Ajoy , Ghosh Amit
Published: March 2011

The grain growth behavior of polycrystalline MoSi2 and composites containing SiC particulates has been studied in the temperature range of 1200-1800°C during static annealing as well as under concurrent deformation conditions. Monolithic MoSi2, with ∼ 26 μm grain size appears to be extremely resistant to grain growth up to 1500°C. However, the grain growth rate above this temperature is quite rapid. When particulate reinforcements are used to reduce the grain size of MoSi2 to 4.4 μm, a stable microstructure is maintained up to 1500°C. Accelerated grain growth kinetics are observed at 1800°C under conditions of large plastic strain. This enhanced grain boundary mobility is associated with particle sweeping and particle agglomeration effects. At lower temperatures, where dislocation creep is the more dominant deformation mechanism these effects are absent. In the presence of a Si concentration gradient extremely high growth rates of columnar MoSi2 grains have been observed during reaction synthesis of MoSi2.
The Effects of in-Situ Processing Methods on the Microstructure and Fracture Toughness of V-V3Si Composites
Authors: Strum M. J. , Henshall G. A. , Bewlay B. P. , Sutliff J. A. , Jackson M. R.
Published: March 2011

The present paper describes ductile-phase toughening in V-V3Si in-situ composites that were produced by conventional arc melting (AM), cold-crucible induction melting (IM), and coldcrucible directional solidification (DS). Notched three-point bending tests were performed to determine the effects of synthesis method on the room temperature fracture toughness of eutectic compositions, which contain nearly equal volume fractions of V3Si and the V(Si) solid solution phase. Fracture toughness values ranged from 10 MPa√m for the AM eutectic to over 20 MPa√m for the IM and DS eutectic alloys. SEM fractography, fracture surface profiling, and chemical analyses were performed to correlate the toughness values with the microstructures and interstitial concentrations produced by the three synthesis methods.
Processing, Properties and Applications of High-Temperature Niobium Alloys
Authors: Wojcik C. Craig
Published: March 2011

Niobium alloys are used in a variety of high-temperature applications ranging from light bulbs to rocket engines and nuclear reactors. The unique physical and chemical properties of these alloys have often dictated that only niobium alloys could fulfill certain application requirements. Compared to other refractory metals, niobium alloys have low density and are very ductile even at cryogenic temperatures. Most niobium alloys are also very resistant to corrosion by acids and liquid alkali metals; however, oxidation resistance at high temperatures is usually catastrophic unless protective coatings are used.

An overview of the commercial high-temperature alloys is presented. Some of the unique properties of these alloys, which require unusual processing methods and equipment, are highlighted. Important physical properties of these alloys are discussed with reference to specific applications. The needs and design restraints of these applications provide valuable insights for those developing other high-temperature materials.
Creep Characteristics of Tungsten Wires
Authors: Wang Wego
Published: March 2011

In this study heavily-drawn tungsten wires were tested for creep at a constant load of 115 MPa in a 10-3 torr nitrogen atmosphere. These fine wires had an elongated rectangular grain morphology with small average grain sizes, 1.6 to 2.2 µm. The typical test sample wire was about 2.54 m long and 130 µm in diameter. The test wire was heated to the test temperature by self-resistance. The creep elongation was monitored by a transducer. Steady state creep rates were determined from the creep curves for four specimens that were tested at 1673, 1553, 1453, and 1273K, respectively. Diffusional creep is the predominant deformation mode. The experimental data were analyzed and compared with several creep theories: Ashby's combined, Coble's grain boundary and Nabarro's lattice diffusional creep models. The effects of recrystallization, grain aspect ratio, grain growth, impurity contents, nitrification and oxygen contamination on creep behavior are discussed in detail. However, their influences on creep kinetics are minimized in this study by carefully controlled experimental conditions. At a stress of 115 MPa, the grain boundary diffusional creep model successfully predicts the creep behavior at temperatures below 1453K. The instantaneous creep rate is inversely proportional to the cube of grain size at 1453K. The lattice diffusional creep model becomes predominant when the test temperature rises to 1553K. It is concluded that the creep behavior is controlled by grain boundary diffusion at a temperature below 1453K, and lattice diffusion above this temperature. Diffusion controlled creep and grain boundary sliding with diffusional accommodation are coupled in tungsten wires.
In-Situ Processing of Mosi2-Base Composites
Authors: Patibandla N. , Hillig W.B. , Ramakrishnan M.R. , Alman D.E. , Stoloff N.S.
Published: March 2011

Three different methods of preparing Mosi2 and composites reinforced with ceramic fibers by reactive in-situ processing are described. Reactive powder sintering (co-synthesis) of elemental powders, chemical vapor infiltration/deposition and reactive vapor infiltration are examined. Monolithic Mosi2, SiC particle-reinforced Mosi2 or fibrous Mosi2 composites reinforced with Nicalon fiber were prepared. The advantages and disadvantages of these processes relative to more traditional processing techniques such as HIPing of prealloyed powders, mechanical alloying and a reported in-situ displacement reactions are discussed.
Fabrication and Testing of Plasma-Spray Formed MoSi2 and MoSi2 Composite Tubes
Authors: Castro R.G. , Hellmann J.R. , Segall A.E. , Shelleman D.L.
Published: March 2011

Plasma-spray forming has been used to fabricate thick-wall tubes of Mosi2 and Mosi2 containing concentric layers of A12O3. This process is being investigated as a potential fabrication method for producing tubular components of Mosi2 and Mosi2 composites for use in high temperature fuel-burner applications. Results will be reported on the spray forming method used to produce tubes of various sizes. The room temperature strength of pure Mosi2 tubes in the as-deposited condition, and after heat-treating at 1500 °C for 2 hours in vacuum, will also be reported. The strength of plasma sprayed Mosi2 tubes were measured via diametral compression of 0-ring and C-ring sections in air at room temperature. Qualification of the strength distribution was based on Weibull statistical theory.
Plastic Behavior and Deformation Structure of Silicide Single Crystals with Transition Metals at High Temperatures
Authors: Umakoshi Y. , Nakashima T. , Nakano T. , Yanagisawa E.
Published: March 2011

The mechanical and plastic behaviors of refractory silicide single crystals with Cllb (MoSi2), C40 (CrSi2, TaSi2 and NbSi2), D88 (Ti5Si3) and Cl (CoSi2 and (Co0.9Ni0.1)Si2) structures were investigated. The C40–type silicides were deformed by (0001)<1120> slip. Their yield stress decreased sharply with increasing temperature but NbSi2 and TaSi2 which were deformable even at low temperatures, exhibited anomalous strengthening around 1350°C. Deformation of Ti5Si3 whose ductile-brittle transition occurred around 1300°C was controlled by twins and the brittle fracture occurred on the basal plane. In CoSi2 the {001}<100> slip was only activated at ambient temperatures but addition of Ni activated {110}<110> slip as secondary slip system and improved the ductility. The creep behavior of MoSi2 and CrSi2 single crystals were also investigated and was found to be controlled by the viscous and glide motion of dislocations.
Amorphous Phase Transformation During Rapid Thermal Annealing of Ion-Implanted Si
Authors: Kirillov D. , Powell R. A. , Hodul D. T.
Published: March 2011

Variations in the local order of the amorphous phase of Si produced by ion implantation and subjected to rapid thermal annealing were studied using the Raman scattering technique. It was found that the low order amorphous phase was formed independently of implantation ion species for low dose, low energy implantation at room temperature. For high energy, high dose implantation with heavy ions, the ion beam annealing effects were apparent and the higher order amorphous phase was formed. Rapid thermal annealing produced transformation from the low order phase to the high order amorphous phase. The continuous transformation was completed when the detectable crystalline phase regrowth started.
Structural Changes During Transient Post-Annealing of Preannealed and Arsenic Implanted Polycrystalline Silicon Films
Authors: Krause S. J. , Wilson S. R. , Gregory R. B. , Paulson W. M. , Leavitt J. A. , McIntyre L. C. , Seerveld J. L. , Stoss P.
Published: March 2011

Polycrystalline silicon films were transient preannealed, As implanted, and transient post-annealed at peak temperatures up to 1250°C for times up to 17.5 seconds. Structural changes occurring during post-annealing were examined by transmission electron microscopy. These results were correlated to Rutherford Backscattering and sheet resistance results. The grain size, which increased from 5–20 to 150–300 nm during preannealing, did not increase during post-annealing. During early stages of post-annealing, As diffused along grain boundaries and generated dislocation sources at grain boundary surfaces. Subsequently, as annealing progressed, a fine, As-rich cellular network structure propagated into the grains until the structure of an entire grain was transformed into a fine cellular network at the longest annealing times. Residual stresses in the film were relieved during formation of the network structure. The sheet resistance of preannealed samples, in comparison with non-preannealed samples with similar implantation and final transient anneals, was lower at shorter annealing times due to the larger grain size, which increased mobility, and the reduced grain boundary area, which trapped less As. It was also lower at longer annealing times due to the formation of the cellular network structure. In subsequent furnace stability tests for 30 minutes at 700–900°C, the sheet resistance increased less for preannealed than for non-preannealed samples.
DLTS Characterization of N-Type Silicon After Rapid Thermal Annealing of Boron Implantation
Authors: Ransom C. M. , Sedgwick T. O. , Cohen S. A.
Published: March 2011

DLTS measurements show that majority-carrier traps exist after quartz-lamp, rapid-thermal annealing (RTA) activation of B+ and BF2+ ion implants in n-type silicon. Levels at Ec-0.17, 0.27, 0.44 and 0.57 eV annealed out with an additional 20 minute isochronal anneal at 550°C in argon. A stable defect at 0.37 eV existed at temperatures above 750°C. DLTS measurements of a Schottky diode on n-type silicon after only RTA indicated that electron traps could be introduced into n-type silicon by the RTA alone.
An Overview and Comparison of Rapid Thermal Processing Equipment: a Users Viewpoint
Authors: Wilson S. R. , Gregory R. B. , Paulson W. M.
Published: March 2011

Five different RTP units have been examined. These are the Varian RTP-800, the Eaton ROA-400, the A.G. Associates 2101/2106, the Tamarack 180A-C and the Varian IA-200. Each system is a cassette-to-cassette serial processor designed for use in a high volume semiconductor fabrication line. These units will heat a wafer from room temperature to 400–1400C in times on the order of a few seconds. Each unit uses radiation to heat and cool the wafer. The different radiation sources, wafer handling systems, temperature measurements and control computers are discussed. The control of slip and nonuniform temperatures is presented as well as information regarding the types of ambients that can be used in each system.
Process Control for a Rapid Optical Annealing System
Authors: Gelpey Jeffrey C. , Stump Paul O. , Smith John W.
Published: March 2011

When high temperature processes are being carried out in a diffusion furnace, temperature control is accomplished in a straight forward manner. By using thermocouples and a proportional controller, sufficient accuracy and control are available to the process engineer.

But with the current shift toward the more rapid annealing schemes, better control is a necessity. In order to achieve this accuracy, especially when the heat source is a 100 kilowatt arc lamp, more sophisticated control methods must be employed. By using an optical pyrometer tuned to operate at a wavelength where external interferences are minimized, wafer temperature may be monitored to a high degree of accuracy and with the fast response times needed.

Coupling the output of the pyrometer to a microprocessor based controller allows the engineer to create and use multi stepped time/temperature profiles which are highly repeatable.

This paper will describe such a system and how it is used in a production oriented rapid optical annealing system.
The Effect of Thin Dielectric Films on the Accuracy of Pyrometric Temperature Measurement
Authors: Pettibone D. W. , Suarez J. R. , Gat A.
Published: March 2011

Pyrometers are used to measure wafer temperature in rapid thermal processors. This paper focuses on the effect of thin dielectric films on the accuracy of pyrometric temperature measurement. The thin films affect the emissivity of the wafer, which in turn affects the radiation emitted by the wafer. Wafers with different oxide thicknesses were monitored by both pyrometer and thermocouple. Temperature errors of the order of 10°C to 50°C were found for wafers of differing oxide thicknesses. The chamber reflectivity was found to be an important factor in determining the ‘effective’ emissivity of the wafer. Pyrometer recalibration is necessary to accurately measure wafer temperature.
Characterization of PSG Films Reflowed in Steam Using Rapid Thermal Processing
Authors: Shah N. , Vittie J. M. C. , Sharif N. , Nulman J. , Gat A.
Published: March 2011

This study describes the use of a steam environment to reflow phosphosilicate glass (PSG) samples using a HEATPULSE® rapid thermal annealer. The samples comprised PSG over poly steps and of open contacts in PSG. It was observed that reflow occurs 50°C lower in steam than in dry O2. An acceptable flow cycle for 8 w/o P in PSG glass is 1050°C for 10 seconds in steam, while for 6 w/o P PSG it is 1100°C for 10 seconds. Steam is found to be an effective amibient for densification of the PSG film. The thermal oxide grown in the contact during opening reflow was determined to be near 140 A. The operating regime for a junction depth <0.4 um and a reflow angle < 75° is presented for 8 w/o P.
Rapid Isothermal Fusion of BPSG Films
Authors: Mercier J. S. , Madsen L. D. , Calder I. O.
Published: March 2011

A study on the rapid isothermal fusion (RIF) properties of borophosphosilicate glass (BPSG) films is presented. Conventional furnace fusion (FF) results are also reported for comparison purposes. The effects of varyinq the temperature (950°-1150°C for RIF, and 800°-1000°C for FF) and the cycle duration (5–60 s for RIF, and 7–60 min for FF) were investigated in a N2 ambient. Two deposition methods were used for the BPSG films, namely atmos- Dheric pressure CVD (APCVD) and low pressure CVD (LPCVD), both with the low temperature oxidation of SiH4, PH3 and B2H6 as a deposition reaction mechanism. The boron and phosphorus concentrations were maintained at 4 w/o for both species. Step coveraae fusion test structures were used to characterize the qlass flow. It was found that for both RIF and FF techniques, a considerable amount of fusion resulted from heating cycles which are compatible with the shallow Junctions required for VLSIC's. With BPSG, the choice between RIF and FF can thus be based on criteria other than olass fusion, such as shallow junction annealing. Also, more fusion was obtained for LPCVD films than for APCVD films.
Characterization of Tungsten Silicides Formed by Rapid Thermal Annealing.
Authors: Siegal M. , Santiago J. J. , Van der Spiegel J.
Published: March 2011

Tungsten silicide samples were formed by sputter depositing 80 nm W metal onto (100) oriented, 5 ohm-cm Si wafers. After deposition, the samples were fast radiatively processed in an RTA system using quartz-halogen tungsten lamps as radiation sources for time intervals ranging from 20 to 60s under high vacuum. Films processed at 22–25 W/cm2 radiation with the film side of the samples oriented away from the lamps result in films which are metallic or cloudy in color, and have mixed composition as evidenced by x-ray diffraction (W, W5 Si3 and WSi2). Films processed with the film side oriented toward the lamps show the occurrence of a phase transforF.ation clearly nucleated at the film edge. The new phase is grey and mostly composed of WSi2, with film resistivities 55–60 μΩ-cm. AES measurements show a uniformly distributed Si diffusion profile into the metal film, while SEM indicates a nucleation and growth of the phase once diffusion occurs.
Diffusion Modeling of the Redistribution of Ion Implanted Impurities
Authors: Michel Alwin E.
Published: March 2011

Transient enhanced diffusion during rapid thermal processing has been reported for most of the common dopants employed for silicon device fabrication. For arsenic a large amount of the available data is fit by a computational model based on accepted diffusion mechanisms. Ion implanted boron on the other hand exhibits anomalous tails and transient motiou. A time dependence of this displacement is demonstrated at lower temperatures. High temperature rapid anneals are shown to reduce some of the anomalous motion observed for low temperature furnace anneals. A model is described that links the electrical activation with the diffusion and describes both the transient diffusion of rapid thermal processing and the large anomalous diffusion reported many years ago for furnace anneals.
Silicon Oxidation by Rapid Thermal Processing (RTP)
Authors: Hodge A. M. , Pickering C. , Pidduck A. J. , Hardeman R. W.
Published: March 2011

Single crystal silicon wafers have been oxidised by exposure to an oxygen ambient at atmospheric pressure during RTP using an A G Associates Heatpulse 2101 Rapid Thermal Annealer. Wafers of the standard orientations used in silicon device processing <100>, <111> and <110> were studied. Oxidation was carried out in the temperature range 900 to 1250°C for times of RTP from 4 to 25U seconds producing oxides up to 60nm in thickness. Oxidation rates and their orientation and temperature dependence were derived from ellipsometric measurements of oxide thickness. X-ray photoelectron spectroscopy (XPS) and infra-red absorption spectrophotometry were also employed in the oxide characterisation. Preliminary electrical characterisation of the oxides, investigated using MOS C-V analyses, showed that the interface state densities were comparable to those in conventional furnace grown oxides.
Oxide Growth Using the Water-Wall Arc Lamp
Authors: Gelpey Jeffrey C. , Stump Paul O. , Capodilupo Ronald A.
Published: March 2011

The uses of Rapid Thermal Annealing or Rapid Thermal Processing (RTP) have been expanding beyond the original post implant annealing. RTP has been used to reflow low temperature oxides (PSG or BPSG), anneal silicides and to sinter contacts. One application of RTP which is beginning to receive attention is the growth of oxides or nitrides of silicon.

This paper will examine the use of a commercial rapid thermal processing system based on a very high power water-wall DC arc lamp to grow oxides on silicon wafers. The work includes a study of the growth rates of oxides at different temperatures. Direct feedback control of wafer temperature and high ramp-up and cool-down rates are used to minimize the effects of temperature errors or “tails” in the temperature/time profiles. Ellipsometry is used as the primary measurement tool to characterize the oxide films.

In addition to using a pure, dry oxygen atmosphere, several oxygen-argon mixtures are used. The effects of atmosphere on the growth rate of the oxide film are reported.

In order to become a practical application of RTP, oxide growth must be accomplished uniformly and reproducibly. These characteristics are machine-dependent. The uniformity of films grown in this system are discussed. The growth of oxide films and the uniformity measurements are used as an indirect technique to characterize the uniformity of the system. The reproducibility of film thickness is also examined.
Kinetic Studies of Silicon - Silicon Dioxide Interface Trap Annealing Using Rapid Thermal Processing
Authors: Reed Michael L. , Plummer James D.
Published: March 2011

Rapid thermal processing is a promising tool for studying the kinetics of interface state annealing and other process phenomena on short time scales. We have studied the decay of interface states with a variety of ambients, temperatures, and oxide thicknesses. Annealing kinetics appear to be controlled by a surface reaction process, and not hydrogen diffusion through the oxide. The annealing behavior depends strongly on temperature but less so on other process parameters. Our experimental methodology for temporal process modeling is discussed.
Damage Removal Processes in Ion Implanted, Rapidly Annealed GaAs
Authors: Jacobson D. C. , Pearton S. J. , Hull R. , Poate J. M. , Williams J. S.
Published: March 2011

The removal of lattice damage and consequent activation by rapid thermal annealing of implanted Si, Se, Zn and Be in GaAs was investigated by capacitance-voltage profiling, Hall measurements, transmission electron microscopy (TEM), secondary ion mass spectrometry and Rutherford backscattering. The lighter species show optimum electrical characteristics at lower annealing temperatures (˜850°C for Be, ˜950°C for Si) than the heavier species (˜900°C for Zn, ˜1000°C for Se), consistent with the amount of lattice damage remaining after annealing. TEM reveals the formation of high densities (107 cm−2) of dislocation loops after 800°C, 3s anneals of high dose (1×1015 cm−2) implanted GaAs, which are gradually reduced in density after higher temperatures anneals (˜1000°C). The remaining loops do not appear to effect the electrical activation or carrier mobility in the implanted layer, the latter being comparable to bulk values.
The Effect of Impurities in the SPE Kinetics in GaAs
Authors: Licoppe C. , Nissim Y. I. , Meriadec C.
Published: March 2011

Solid phase epitaxial (SPE) growth of ion implanted GaAs layers has been studied using the time resolved reflectivity technique. A series of implanted impurities have been selected to study the dependance of the nature of the impurity on the growth kinetics. It has been found that the activation energy and the kinetics of growth were independant on the choice of implanted substitutional impurity. Only impurities such as Argon were responsible of a large decrease in the regrowth rate. The same technique is shown to bring informations on the amorphous-crystal interface structure during growth. From these informations it has been possible to show that interface roughening occured during SPE in (100) GaAs. This interface evolution is an intrinsic property of the implanted GaAs material.
Rapid Annealing of GaAs: Uniformity and Temperature Dependence of Activation
Authors: Cummings K. D. , Pearton S. J. , Vella-Coleiro G. P.
Published: March 2011

Scanning microwave photoconductance, capacitance-voltage profiling and Hall effect measurements were used to investigate the uniformity of activation of Si, Be and Mg implanted 2″ and 3″ diameter, semi-insulating GaAs substrates after rapid thermal annealing in a commercial furnace. The results indicate that carrier lifetimes and mobilities for low dose (3−4 × 1012 cm−2) implants and carrier densities for high dose (1× 1015 cm−2) implants are comparable or superior in rapidly annealed substrates to those obtained in thermally annealed implanted layers. The uniformity of these parameters is not significantly different for wafers annealed by either method. The temperature dependence of damage removal and carrier activation in the implanted regions during both furnace and transient annealing was also investigated, and demonstrates that the microwave photoconductance technique gives results for donor implantation correlating well with conventional backscattering and electrical measurements respectively.
Rapid Themal Annealing of Shallow. Diffused Contact Regions in GaAs
Authors: Kepler N. J. , Cheung N. W. , Chu P. K.
Published: March 2011

Rapid thermal annealing (RTA) is used to form shallow and heavily-doped contact regions in undoped, semi-insulating GaAs. These layers are formed by using a high-intensity tungstenhalogen lamp to diffuse germanium and selenium from a deposited GeSe thin-film. RTA reduces surface degradation and permits better control of the diffusion profile than conventional furnace annealing. Optimal 20-second RTA occurs above a diffusion threshold at 950°C but below the failure of the SiO2 encapsulant at 1100°C. The n+ regions created have peak impurity concentrations over 1020/cm3 at depths under 750 Å with sheet resistances less than 60 Ω/▩. Non-alloyed ohmic contacts exhibit specific contact resistivites of 2.2 × 10−4 Ω · cm−2.
Rapid Thermal Processing: A Bibliography
Authors: Powell R. A. , Manion M. L.
Published: March 2011

This bibliography presents 342 references to work published on rapid thermal processing (RTP) from 1979 through mid-1985. A variety of broad-beam energy sources are represented, including: arc and quartz-halogen lamps, blackbody radiators, strip heaters, broadly rastered electron beams, and defocused CO2 lasers. Citations were obtained by both manual searching and searching of a commercially available computerized data base (I NSPEC). Entries are grouped under 13 topical headings: reviews, implanted dopant activation and diffusion in silicon, polycrystalline silicon, silicides and polycides, metals, dielectrics, compound semiconductors, defects and microstructure, device applications (silicon and compound semiconductors), miscellaneous applications, equipment, and modeling. Within each group, citations are arranged alphabetically by title. A full author index is provided.
Study of “Reverse Annealing” of Boron Under Low Temperature Lamp Anneals
Authors: Huang J. , Jaccodine R. J.
Published: March 2011

The reverse annealing of ion implanted boron, namely, the decrease in the concentration of electrically active boron as the isochronal annealing temperature increases, occurs in the temperature range from 550 to 650°C during conventional furnace heating. In this study, silicon crystals were boron implanted at 50 Kev to a dose of 1×1015 cm-2 followed by both furnace and tungsten-halogen lamp annealing in the reverse annealing temperature range. Cross-sectional Transmission electron microscopic (TEM) technique was used to examine the microstructural changes during annealing as a function of depth. Sheet resistance measurements gave a quick check of the electrical properties, while spreading resistance profiling with shallow angle lapping and Hall measurements reveals the mobility and carrier concentration as a function of depth. Czochralski and Float Zone crystals were studied to examine the effect of oxygen. Tungsten-halogen lamp thermal processing was found to have a more pronounced effect on the annealing of secondary defects than did furnace annealing. The reverse annealing of boron was eliminated completely for lamp annealing time as short as 60 seconds.
Diffusion and Activation During Rapid Thermal Annealing of Implanted Boron in Silicon
Authors: Cowern N E B , Yallup K J , Godfrey D J , Hasko D G , McMahon R A , Ahmed H , Stobbs W M , McPhail D S
Published: March 2011

The diffusion and activation of implanted boron in silicon during rapid thermal annealing (RTA) has been studied using the analytical techniques of SIMS, TEM, and sheet resistance measurements. Both crystalline and pre-amorphised silicon substrates were investigated. Data analysis in conjunction with a range of numerical models indicates some novel features of boron RTA, as well as accounting for previously observed features. In particular, a large transient diffusion enhancement coupled with an increase of electrical activity, are seen at short anneal times, in the case of crystalline silicon substrates. A non-equilibrium diffusion enhancement of a different type is also seen at much longer times, in both crystalline and pre-amorphised samples implanted to high doses. This second enhancement persists after all the precipitated boron formed on implantation has become substitutional. TEM studies show that the transient enhancement may be associated with the evolution of extended defect structures during the early stages of annealing. Both types of enhancement can be well represented by multiplying the ‘normal’ concentration-dependent diffusivity (with β=0.5) by a factor f>1.
A Simple, Non-Destructive Optical Technique to Characterize Ion-Implanted Semiconductor Wafers
Authors: Young Jeff F. , Jensen H. R. , Simard-Normandin Martine
Published: March 2011

A simple, non-destructive technique to characterize the properties of ion-implanted semiconductor wafers is described. The method consists of measuring the infrared attenuated total reflection (ATR) spectrum of the implanted layer/air interface and fitting it with a calculated spectrum which takes account of the free carrier density profile and any possible residual damage and/or amorphization. The results obtained on boron and implanted Si wafers, annealed at different temperatures in a rapid thermal annealer, are compared with their respective SIMS profiles.
GROWTH AND CHARACTERIZATION OF Hg1−xCdxTe ON CdTe SUBSTRATES, PREPARED BY ORGANOMETALLIC EPITAXY
Authors: Bhat I. B. , Ghandhi S. K.
Published: March 2011

Hgl−xCdxTe layers have been grown on CdTe substrates using dimethylcadmium, diethyltelluride and mercury in a horizontal reactor. Details of conditions for growth of these layers are presented in this paper. Specular surfaces of Hg1−xCdxTe with × ≥ 0.15 were obtained on (100) 3°, → (110) oriented CdTe substrates. Both n-type and p-type layers could be obtained. The mobility of these layers was measured over the temperature range of 10 K to 300 K. The mobility of n-type Hg.81Cd.19Te layers, measured at 2.1 kG, was 3.0 × 105cm2/V-sec at 60 K, falling to 2 × 105cm2/V-sec at 10 K. P-type layers were also grown, and are described in this paper.
LATTICE MATCHING IN HgCdTe-CdZnTe HETEROJUNCTIONS
Authors: Maekawa T. , Saito T. , Yoshikawa M. , Takigawa H.
Published: March 2011

An etch pit study has been made on misfit dislocations in (111) HgCdTe-CdZnTe heterojunctions grown by liquid phase epitaxy. It was shown that misfit dislocations were localized at the original surface of the substrate, because Zn diffused into the epilayer during epitaxial growth prevents movement of dislocations. For lattice matching between Hg0 7Cd0.3Te and Cd1−yZnyTe, the optimum ZnTe mole fraction of Cd1−yZnyTe was found to be 2.9%.
X-RAY MONITORING OF InGaAsP LAYERS GROWN BY VAPOR PHASE EPITAXY
Authors: MACRANDER A. T. , STREGE K.
Published: March 2011

X-ray double crystal diffractometry provides a means of rapidly characterizing epitaxial structures. Because the technique is rapid and nondestructive and because it yields a wealth of information, rocking curves have been routinely obtained and extensively studied by us. We present here selective results illustrating the typical progression in layer quality which occurs from the initial growth in a reactor to the growth of device quality material.
X-RAY DIFFRACTION ANALYSIS OF EPITAXIAL STRUCTURES
Authors: PAINE BRUCE M.
Published: March 2011

The technique is described for use of x-ray double crystal diffractometry for analysis of epitaxial structures. This method has been shown to be very useful for characterizing a wide variety of configurations, ranging from single epitaxial layers to damaged superlattices. It yields depth profiles of structure factors and strains relative to the substrate, which can be directly related to layer thicknesses and compositions. Information about dislocations and random atomic displacements is also present. The key to this technique is computer fitting of the x-ray data with a model for the diffraction process, utilizing trial profiles for the strain and structure factors of the epitaxial layers. In the work to be presented a kinematic model for the diffraction is used. The technique is demonstrated with analyses of an Alx Ga(1−x) As single layer on GaAs, an AlSb/GaSb superlattice on GaSb, epitaxial CoSi2 on Si, and ion-implanted and annealed AlxGa(1−x)As superlattices on GaAs.
INITIAL STAGES OF EPITAXY OF METALS ON Si(lll)-7x7 STUDIED BY UHV ELECTRON MICROSCOPY
Authors: TAKAYANAGI K.
Published: March 2011

Initial condensations of Cu, Ag and Au on Si(lll)-7x7 surface are seen continuously by video tape recording and intermittently by photographic films using an UHV electron microscope in reflection electron microscopy (REM). The growths of initial superlattice structures are found to relate with the steps of the 7x7 surface and the superlattice structures of a for Cu, for Ag and 5x2 for Au are nucleated at the upper side of the stepsand grow over the lower side terrace accompanied by the step movement. The growth of Au on Si(lll)-7x7 surface is seen in transmission electron microscopy (TEM) to supplement geometric information. It is found that the 5x2 domain of Au grows in the Si direction preferentially. The superlattice structures formed at submonolayer range are seen for the first time in TED pattern, which is useful to judge the previously proposed models from intensity distribution. REM-RHEED and TEM-TED allow us to study dynamic process of the initial growth stages of metals on Si(lll)-7x7 in real space and to analyse the geometrical structures of the superlattice structures at submonolayer.
The Structure and Composition of Interphase Boundaries in Ni/Ag-(001) Thin Films Doped with Au
Authors: Dregia S.A. , Bauer C.L. , Wynblatt P.
Published: March 2011

Computer simulations of the Ni/Ag-(001) interphase boundary have been performed with the Embedded Atom Method. The relaxed atomic configurations, the periodic interaction potential, the shear modulus of the interface, and the interaction of an Au impurity with the interface have been evaluated. In addition, experimental studies have been conducted on the same system; and the structure and composition of the interface have been simultaneously examined.
NEW SUPERLATTICE ARCHITECTURE IN III-V COMPOUND SEMICONDUCTORS VIA CONTROL OF EPITAXY ON AN ATOMIC SCALE
Authors: PETROFF P. M.
Published: March 2011

The perfection and compositional stability of alternate monolayer compounds (AMC) structures deposited by molecular beam epitaxy as a function of several crystal growth parameters are reviewed. By using the (GaAs)1 - (AlAs)1 AMC structure as a prototype system, the effects of substrate temperature, and orientation on the AMC ordering are presented. Conditions for producing new superlattice architectures are discussed.
STRUCTURAL AND MAGNETIC PROPERTIES OF SINGLE CRYSTAL RARE EARTH Gd-Y SUPERLATTICES
Authors: Kwo J. , McWhan D. B. , Hong M. , Gyorgy E. M. , DiSalvo F. J.
Published: March 2011

High quality single crystal rare earth Gd-Y superlattices with wavelength varying from 8to 42 atomic layers were grown by the recently developed metal molecular beam epitaxy technique. The crystallinity and coherence of the superlattices were examined by X-ray diffraction, and the profiles of composition modulation and strain modulation were determined from a quantitative analysis based on a simple diffusion model for the Gd-Y interfaces. The sharp boundaries achieved in these metallic superlattices are approaching those in semiconductor superlattices. The various in-plane magnetization behavior at low fieldsamong superlattices of different wavelengths suggests the possible presence of new magnetic ordering structures as caused by the artificial modulation.
CONDUCTION BAND ENERGY LEVELS IN SUPERLATTICES WITH COMPLEX UNIT CELLS
Authors: OSBOURN G. C.
Published: March 2011

The conduction band energy levels and wavefunctions in a number of superlattices with more than two layers per unit cell have been calculated using an effective mass model. Many of these structures exhibit energy levels which can be modeled as resulting from a conventional superlattice with a modified bulk conduction band minimum in the effective wells. These structures should be useful for extending the size of the superlattice periodsallowed in strained—layer superlattices.
QUANTUM CONFINEMENT EFFECTS IN ZnSe/ZnMnSe STRAINED-LAYER SUPERLATTICES
Authors: Bylsma R.B. , Frohne R. , Kossut J. , Becker W.M. , Kolodziejski LA. , Gunshor R.L.
Published: March 2011

Photoluminescence and photoluminescence excitation spectroscopy have been used to identify excited state energy levels in ZnSe/ZnMnSe strained-layer superlattices. Several ZnSe/ZnMnSe superlattices have been grown by MBE with different concentrationsof Mn in the barrier material and consequently with different degrees of lattice mismatch between the ZnSe well and ZnMnSe barrier materials. A strain-induced decrease of the band gap is observed in these structures. Photoluminescence excitation spectra reveal a strain dependent splitting of the heavy and light hole n=1 subbands. The magnitude of this splitting, as well as the observed photoluminescence red-shift, are compatible with expectations based on calculated strains and the deformation potentials of ZnSe.
MBE GROWTH OF NON-LATTICE MATCHED (BaCa)F2, (Pb,Sn)Se/(Ba,Ca)F 2 AND CdTe/(Ba,Ca)F2 ON Si SUBSTRATES
Authors: ZOGG H. , MAIER P. , NORTON P.
Published: March 2011

Graded (Ca,Ba)F2 layers consisting of near lattice matched CaF2 at the Si interface and of BaF2 with 14% increased lattice constant at the top surface were grown by molecular beam epitaxy (MBE) on Si(111). Smooth and crackfree layers exhibiting Rutherford backscattering (RBS) channeling minima below 5% were obtained. Device quality epitaxial layers of PbTe, PbSe and (Pb,Sn)Se were grown on top of these structures. Mechanical stress at 300K was relaxed by athermal mechanisms in the fluoride- as well as in the Pb-salt films. - In preliminary runs, epitaxial CdTe-layers were obtained on Si(111) using the same fluoride-buffer film technique and which showed clear SEM electron channeling patterns.
Theoretical Methods for Calculating Electronic Properties of Semiconductor Superlattices
Authors: SCHULMAN JOEL N.
Published: March 2011

A variety of theoretical models have been used to calculate the electronic properties of semiconductor superlattices. The methods vary in their ease of implementation, number of empirical parameters, and ability to incorporate physical effects. There is no “best” method; the choice of model is made on the basis of the desired property under investigation, such as subband energy levels, energy band dispersion and effective mass, strain effects, or optical spectra. The strength and limitations of the Kronig- Penney, envelope function, and tight-binding models will be reviewed, including one-, two-, and multi-band versions. The relationship of superlattice to bulk band structure, and the issue of dispersion in the growth and in-plane directions will be illustrated with the examples of the CaAs-GaAlAs and HgTe-CdTe superlattices.
PHOTOCONDUCTIVITY, PHOTOREFLECTANCE AND PHOTOLUMINESCENCE OF GaAs-AlAs MULTIPLE QUANTUM WELLS
Authors: NEFF H. , BACHMANN K. J. , LAIDIG W. D.
Published: March 2011

Employing temperature dependent photoconductivity, photoluminescence and photoreflectivity measurements, we have analyzed a GaAs-AlAs multiple quantum well. The above optical techniques clearly resolve the fundamental inter-subband transitions, including heavy hole-light hole splittings. At T < 60K an anomalously high photoconductivity was discovered below the direct inter-subband transitions and is attributed tentatively to the presence of extrinsic interface states within the bandgap. For T > l00K the fundamental indirect transition was discovered and associated with LO (L) - phonon absorption.
DIRECT OBSERVATION OF INTERFACE TRAPS IN OMVPE-GROWN SELECTIVELY AlGaAs/GaAs HETEROSTRUCTURE USING MODIFIED DLTS
Authors: TAKIKAWA M. , OOHORI T. , KASAI K. , KOMENO J. , SHIBATOMI A.
Published: March 2011

By using a DLTS technique, we measured the drain current transient from a gate bias pulse for a HEMT. Two negative peaks and one positive peak were observed. From the analysis of the spectra, we found that the positive peak was due to the interface trap. The density of the interface trap was determined from a DLTS fitting procedure. The effect of the interface traps on the electrical properties of the heterostructure are discussed.
INTERFACIAL DEFECTS AND EPITAXY
Authors: POND R.C.
Published: March 2011

It is shown that interfacial defects are characterised by combinations of symmetry operations, one from each of the adjacent crystals. This approach demonstrates that the variety of possible interfacial defects is broader than had been previously recognised, and includes disclinations and dispirations in addition to dislocations. The condition of the initial substrate surface is shown to have a very important influence on the character and stability of interfacial defects.