bluuebunny/crossref_metadata_2025 huggingface dataset:
Ion Beam Self Annealing in Thin Silicon Films
Authors: Rubio J. D. , Vijay R. P. , Hart R. R. , Pearce J. D.
Published: March 2011

Residual lattice disorder in lμm-thick silicon films as a function of the dose rate of 120 keV Ar+ ion implantations has been investigated. At a fluence of l×1 014 ions/cm2, low dose rates produced a highly damaged surface layer as expected; however, at a dose rate sufficient to locally heat the implanted film to a temperature of approximately 700°K, essentially complete annealing of the lattice disorder was observed. This temperature is significantly less than that normally required for post-implant thermal annealing. Measurements of lattice disorder were based on medium energy Rutherford backscattering and channeling analyses.
Furnace Anneal of A–Axis Sapphire Amorphised by Indium Ion Implantation
Authors: Sood D. K. , Cao D. X.
Published: March 2011

Indium implantation at 77°K into a–axis sapphire to peak concentrations of 6–45 mol % In produces amorphous surface layers. Isothermal annealing in Ar at temperatures between 600–900°C shows effects strongly dependent on ion dose. At lower doses <2×1016 In/cm2, the amorphous layer undergoes epitaxial regrowth as the amorphous to crystalline interface advances out towards the surface. Regrowth velocity is high in about the first half hour of the anneal. Regrowth obeys Arrhenius behaviour with an activation energy of 0.7eV for initial faster growth and 1.28eV for further anneal times. The amorphous phase transforms directly to ⊥-A12O3 without any evidence of an intermediary γ-phase. At higher doses, epitaxial regrowth is substantially retarded and rapid diffusion of In within the amorphous phase dominates.
Radiation Damage of SiO2/Si By Energetic Neutral Beam and Vjuv Photons
Authors: Mizutani Tatsumi , Nishimatsu Shigeru , Yunogami Takashi
Published: March 2011

To clarify the generation mechanism of radiation damage induced in SiO2/Si by plasma processes, effects of three different beams, i.e., ions, neutrals and vacuum ultraviolet (VUV) photons have been evaluated independently. The radiation damage caused by these energetic bombardments has been measured by capacitance-voltage (C-V) measurements. These reveal that bombardments with a 250 eV Neo neutral beam generate + far less flat-band voltage shifts ( ΔVFB) than those with a Ne+ ion beam of equal kinetic energy. This c n be interpreted in terms of the differences in charge build-up and in hole production upon the incidence of these particles. VUV photons produced in the plasma are also responsible for large ΔVFB.
Synthesis of Transition Metal Epitaxial Silicides on Silicon (100), (111)
Authors: Tokarev V. V. , Borisenko V. E. , Pyatkova T. M.
Published: March 2011

Epitaxial silicide growth is of great interest to many researchers and process engineers working in the field of microelectronics. The interest towards epitaxial silicides is due, firstly to the fact that these structures are suitable for systematic investigation of physics of a metal-semiconductor interface, and secondly that epitaxial intermetallic structures on silicon allow development of new devices such as threedimensional ones. At present, however, one can successfully form layers with epitaxial structure with thickness of no more than 150 nm using solid-state reaction in the metal layersilicon substrate system. Such values satisfy researchers dealing with problems of epitaxial growth because main processes occur in the range of 10–20 Å [1]From a technological point of view, however, it is desirable to form layers with thickness up to 1 μm.
Interband Optical Properties of the Microcrystalline Component within the Damage Layer of Be+ - Implanted GaAs
Authors: Feng G. F. , Zallen R.
Published: March 2011

The damage layer in unannealed Be+-implanted GaAs samples (45-keV Be+ ions, 1013 to 5 × 1014 ions/cm2) consists of a fine-grain mixture of amorphous GaAs and GaAs microcrystals, with the characteristic microcrystal size L of the microcrystalline component decreasing with increasing fluence. We have carried out reflectivity measurements on these samples for photon energies from 2.0 to 5.6 eV, in the electronic interband regime. Using Lorentz oscillator analysis and the effective medium approximation, we have extracted the dielectric function of the microcrystalline component (μ-GaAs) within the damage layer. The optical properties of μ-GaAs deviate appreciably from those of the bulk crystal near the interband absorption peaks. The linevidths of these peaks are found to increase over the bulk-crystal value by an amount proportional to (l/L), the increase being about 0.2 eV when L =100 Å. These finite-size effects can be understood in terms of a lifetime reduction caused by the short time it takes for electrons to reach the microcrystal boundaries.
Characteristics of Si-Implanted (211) Versus (100) GaAs
Authors: Epp J. , Dillard J. G. , Siochi A. , Zallen R. , Cole E. D. , Sen S. , Vaseashta A. , Burton L. C.
Published: March 2011

Transport, Raman and XPS measurements were made on SI-implanted (1.7×1013cm−2, 50keV) and rapid-thermal annealed (100) and (211) GaAs substrates In an effort to distinguish differences between the two orientations. With these techniques, no significant differences were found. The implant-damage depth was about 1200Å for both orientations, with slightly higher near-surface damage (and lower mobility) apparent for (211). No unusual features in the (211) carrier concentration profile, as was previously reported, were evident.
Ion Implantation and Ion Beam Analysis of Lithium Niobate
Authors: Arnold G. W.
Published: March 2011

Implantations of He and Ti were made into LiNbO3 and the H and Li profiles determined by elastic recoil detection (ERD) techniques. The loss of Li and gain of H depends upon the supply of surface H (surface contaminants or ambient atmosphere). For 50 keV He implants into LiNbO3 through a 200 Å Al film, the small Li loss is governed by the interface H. This is also the case for He implants into uncoated LiNbO3 in a beam line with low hydrocarbon surface contamination; similar implants under conditions of greater hydrocarbon deposition result in proportionally larger Li loss and H gain in the implant damage region. The exchange is possible only for those He energies, i.e., 50 keV, where the damage profile intersects the surface. For Ti implants Li is lost with little H gain. For this case the Li loss is believed to result from radiation-enhanced diffusion. Where He implantation is used to establish waveguiding in LiNbO3, the presence or absence of H in the implanted region is crucial with regard to refractive index stability, due to the replacement of H by Li from the bulk.
Ion Implantation of KnbO3 and LiNbO3 at Elevated Temperatures
Authors: Buchal C H. , Irmscher R. , Günter P.
Published: March 2011

Ion implantation, annealing and channeling of single crystalline samples of KnbO3 and LiNbO3 have been studied. Raising the substrate temperature above 600 K, greatly increases the tolerance of the crystals for high-dose implantation. In LiNbO3 dynamic recrystallization has been observed for the first time.
Effect of Ion Bombardment on the Dopant Diffusion During Reactive Ion Etching (RIE) of Dielectric Films Deposited on Silicon
Authors: Shenai K. , Lewis N. , Smith C. A. , Baliga B. J.
Published: March 2011

We report on the results obtained from a study conducted to understand the effect of reactive ion etching (RIE) of oxide films on the dopant diffusion in ion-implanted silicon. Thermally grown oxide films on silicon were plasma etched in a CHF3/CO2 plasma. The residual silicon surface damage created during plasma etching was removed by employing a low ion-bombardment, two-step surface plasma cleaning process. The samples with oxide films etched in a wet chemical etchant provided the control for evaluating the effect of the RIE process. The samples were implanted with boron and boron was activated under various conditions to form p-n junctions to obtain a range of boron doping profiles and junction depths. Some boron doped samples were implanted with arsenic to form a heavily doped n+ region at the silicon surface. The resulting doping profiles were analysed using spreading resistance profiling (SRP), four-point probe measurements, and secondary ion-mass spectrometry (SIMS) to understand the activation, diffusion, and precipitation of various dopants. Detailed transmission electron microscopy (TEM) analysis was used to study the microstructural effects. It was observed that plasma etching of the oxide films prior to the formation of boron diffused surface regions in silicon resulted in significant changes in boron diffusion. For low boron implant doses, plasma etched silicon surfaces resulted in retarded boron diffusion. For high boron implant doses, plasma etched silicon surfaces lead to enhanced boron diffusion.
Laser Cladding with a Ni-Fe-Cr-Al Alloy
Authors: Jasim K. Mohammed , West D.R.F.
Published: March 2011

An investigation is reported of the laser surface.cladding of an alloy of nominal composition Ni-4Fe-30Cr-6A1 (wt%) on a mild steel substrate, using a continuous powder feed of the elemental powder mixture into the melt pool. The effect of laser processing conditions has been investigated in relation to clad dimensions, bonding, dilution level, hardness and microstructural features. A 2 kW CW C02laser was used working at 1.6 kW power and 2.5 mm beam diameter at different traverse speeds ranging from 1.8 to 25 mm/s: clad layers were produced in the range of 0.15-3 mm thick. Fine microstructures were obtained (corresponding to the rapid solidification rates). Good metallurgical bonding was observed between the clad layer and substrate within the range of specific energies, 50-130 J/mm2. For all the conditions studied, no cracking was observed in single tracks; low specific energy conditions gave little porosity.
Selected Area Growth of GaAs by Laser Induced Pyrolysis of Adsorbed Ga-Alkyls
Authors: Donnelly V. M. , McCaulley J. A. , McCrary V. R. , Tu C. W.
Published: March 2011

We compare three approaches to excimer laser assisted growth of GaAs: 1) Film growth is dominated by gas phase photolysis of deposition precursor gases at 193 nm under low pressure metal organic chemical vapor deposition (MOCVD) conditions. This approach leads to rapid deposition at low substrate temperature, but with very low spatial resolution (∼1 cm). 2) Growth is controlled by laser induced pyrolysis of adsorbed triethylgallium (TEGa) at 193 nm under metal organic molecular beam epitaxy (MOMBE) conditions. Films grown under these conditions have the potential for high spatial resolution (i.e. submicron), but geometric constraints in MBE conflict with the requirement of a short working distance between the lens and substrate, making it difficult to attain this limit. 3) Areaselective growth is controlled by laser induced pyrolysis of adsorbed TEGa at 351 nm (XeF excimer laser) under low pressure MOCVD conditions. This approach combines the advantage of laser controlled surface chemistry with the potential for much shorter working distances.

Selected area growth of GaAs occurs in this latter mode because TEGa dissociatively chemisorbs at 400°C to form a stable layer which decomposes further under laser irradiation to liberate hydrocarbon products. The Ga left behind on the surface reacts with As2 and As4 (formed by pyrolysis of trimethlyarsine or triethylarsine in a side tube) to grow GaAs in irradiated areas. Since the gas does not absorb at 351 nm the process is highly areaselective. Patterned films with feature sizes of ∼70µm (limited by the mask dimensions) were grown by this method. Interference between the incident beam and light scattered along the surface also causes a substructure of parallel lines to form on the features with a line spacing about equal to the laser wavelength 0.35µm. This indicates that the ultimate spatial resolution is comparable to that predicted by thermal diffusion calculations (∼0.3µm).
Low Temperature Deposition of Hard, Amorphous Diamondlike Films by Laser Evaporation
Authors: Krishnaswamy J. , Rengan A. , Srivatsa A. , Narayan J. , Cong Y. , Collins R. , Vedam K.
Published: March 2011

Substrate temperature during deposition of hard carbon films by short pulse (40 nsec, FWHM) eximer (308 nm) laser ablation (∼1.25 × 108 W/cm2) of solid carbon affects the optical and mechnical properties of deposited films. Films deposited at 25° C are superior to those deposited at 500° C. Deposited films were charaterized by spectroscopic ellipsometry, microhardness, TEM, Raman and FT-IR techniques.
Atomic-Scale Modeling of Low-Energy Ion-Solid Processes
Authors: Dodson Brian W.
Published: March 2011

Various techniques which have been applied to modeling low-energy (≪ 1 keV) ion-solid interactions on an atomistic scale are described. In addition to their individual strengths, all such methods also have a number of drawbacks, both fundamental and practical. The range of validity, and the problems encountered external to this range, will be outlined for the different approaches. Finally, examples of molecular dynamics simulations of low-energy ion-solid interactions will be presented.
Angle Resolved Time-of-Flight Measurements of the Excimer Laser Induced Etching of Silicon in a Chlorine Environment
Authors: Baller T.S. , van Zwol J. , de Zwart S.T. , van Veen G.N.A. , Fell H. , Dieleman J.
Published: March 2011

Si (100) samples have been irradiated with excimer laser pulses (λ = 308nm, pulsewidth =28ns) in a low pressure chlorine environment, at a fluence just enough to melt the surface. Time-of-flight spectra of the particles desorbed due to the laser irradiation have been measured as a function of effective chlorine pressure and desorption angle. Maxwell- Boltzmann distributions have been used to fit the measurements. The mean kinetic energy per particle increases with increasing chlorine pressure. Angular distributions of the desorbed particles are found to be cosine like at a chlorine coverage much less than a monolayer and sharply peaked along the surface normal at coverages on the order of a monolayer. Monte-Carlo simulations of the desorption process show that due to collisions between the desorbed particles the change in angular distribution can be explained. The increase in mean energy with increasing chlorine coverage however cannot be explained by gas phase collisions. A possible desorption process is suggested.
Reactions of Photogenerated CF2 and CF3 on Silicon and Silicon Oxide Surfaces
Authors: Langan John , Shorter J.A. , Xin Xu , Steinfeld J.I.
Published: March 2011

We have investigated the reactions of neutral fluorocarbon fragments, generated by laser photolysis of suitable precursors, with single-crystal silicon and thermally deposited silicon oxide surfaces. CF3 free radicals are generated by infrared multiple-photon dissociation of C2F6. While CF3 undergoes dissociative chemisorption on Si, it adsorbs very little on annealed SiO2 surfaces, and even on ion-damaged oxide surfaces, CF3 adsorbs but does not undergo transfer of fluorine from the fluorocarbon to surface silicon atoms. CF2, produced by excimer-laser photolysis of C2F4, is adsorbed on SiO2 surfaces. As with CF3, no transfer of fluorine from carbon to silicon is observed, even after argon-ion sputtering or ultraviolet irradiation of the surface. These measurements have been extended to NF3; this species chemisorbs and dissociates on a silicon surface, but even a monolayer of oxide is sufficient to block this process. A simple model based on the relative strengths of C-F, N-F, Si-F, Si-C, Si-O, and Si-N bonds appears to account for the observed behavior of CF3, CF2, and NF3 species on silicon and silicon oxide surfaces. In other cases, however, a barrier appears to be implicated in the chemisorption process.
Space/Time Resolved Analysis in μm/nsec Scale of Laser Beam-Solid Surface Interaction in Group IV Elements
Authors: Kasuya A. , Nishina Y.
Published: March 2011

Dynamical characteristics of laser desorption and chemical processes in Group IV elements have been investigated by means of space/time resolved optical spectrometry in micrometers and nanoseconds scale on the light emitted from desorbed particles. The results suggest that desorbed atoms are coagulated in the form of large size clusters in a few ns after laser excitation. These clusters subsequently decompose into their ultimate forms of monomers. This interpretation is consistent with the conclusion drawn from our time-of-flight analysis of decomposition in 100 ns time scale.
Mass and Energy Analysis of Ionic Fragments from Photoablation of Polyimide
Authors: Ulmer G. , Bues K. , Campbell E.E.B.
Published: March 2011

The ionic products from excimer laser photoablation (λ = 308 nm) of polyimide (Kapton) film have been studied as a function of fluence. Large ion masses up to about 900 a.m.u. are easily observed, the mass distribution depending strongly on the fluence. Velocities of the emitted particles lie between 1400 and 10000 ms−1, again dependent on the fluence. A mechanism to explain the high velocities is suggested consisting of ionisation of the surface polymer molecules followed by a Coulomb explosion combined with expansion of the high density gas formed by the photoablation.
Pulsed Laser Cleaning of Antimony Single Crystal <111> Surface
Authors: Petit Etienne J. , Caudano Roland
Published: March 2011

The<111> face of an antimony single crystal was irradiated under ultra-high-vacuum conditions by the 193 rn radiation of a high-power excimer laser. The effects of the laser beam on the sample as a function of the light Energy Density (ED) and of theannealing Repetition Number are presented.

Surface studies by Auger electron spectroscopy, scanning electron microscopy and low energy electron diffraction show that an atomically clean and well ordered surface can be produced by t is method. A strong chemical reduction is induced by pulsed aser annealing above 100 to 130 mI/cm2. Surface analysis shows that, for an ED less than 500 mJ/cm2 the surface evaporates without melting deeper than 200 rim. Evidences for oxide modification and for organic molecule desorption were observed even after irradiations with an ED as low as 45 mJ/cm2.

The surface reduction is described by a thermal model involving surface heating and subsequent evaporation of the oxide layer. The desorption and diffusion processes may involve both thermal and photolytic mechanisms.
Boron Doping of Silicon Using Excimer Lasers
Authors: Slaoui A. , Foulon F. , Bianconi M. , Correra L. , Nipoti R. , Stuck R. , Unamuno S. , Fogarassy E. , Nicoletyi S.
Published: March 2011

The use of lasers in the doping of semiconductors has been investigated extensively these last years both for photovoltaic and microelectronic applications. In this work, doping of single-crystal silicon in BCl3 ambients using a pulsed UV laser has been studied as a function of laser wavelength and fluence in order to investigate the effects of photochemical decomposition of the BCl3 gas and the effects of thermal decomposition of adsorbed layers on the doping process. Different parameters involved in the process (laser energy density, number of pulses per frame, BCl3 gas pressure) were investigated. The electrical characteristics of the doped layers were discussed.
Laser Trim Revisited in the Light of an Excimer Laser
Authors: Gauthier Michel , Bourret Richard , Gavrel Gerard , Carnegie Richard
Published: March 2011

In the Laser Chemistry Group's program aimed at understanding the basic mechanisms involved in the fabrication and characterization of integrated circuits, we have converted an infrared laser-based, thick film trimming technique, which is over 15 years old, to UV light. It is known that excimer lasers can be used for microfabrication of semiconductors and ceramics. Much cleaner ablations than those obtainable with the infrared lasers have been demonstrated in a large variety of materials. This, together with the fact that excimers with repetition rates over 1 kHz are presently on the market, leads us to propose that better accuracies and smaller drifts, should be achievable using excimer laser-based thick film hybrid circuit trimming. Results of XeCl laser trimming of over four hundred resistors, including temperature coefficient of resistance measurements and life tests at elevated temperatures, demonstrate that UV trimming is a factor of 10 better than the presently used infrared process.
Mechanistic Study of Laser Chemical Vapor Deposition of Trimethylindium
Authors: Kawasaki Masahiro , Kasatani Kazuo , Sato Akihiko , Sato Hiroyasu , Nishi Nobuyuki
Published: March 2011

Laser photodissociation of trimethylindium on a quartz substrate has been studied by the laser-induced fluorescence and photofragment mass-spectrometric techniques. Translational energy distributions of photofragments are measured.
The Stability of Si-Si1-xGex Strained Layer Heterostructures.
Authors: Houghton D. C. , Baribeau J-M. , Song K. , Perovic D. D.
Published: March 2011

The structural stability of strained layer superlattices (SLS's) is addressed using an equilibrium model and then compared to the stability of single strained layers. Relaxation mechanisms are described for various superlattice geometries. The application of a critical thickness/strain criterion to define stability limits was found to be very useful in predicting the detailed relaxation process. The competition between relaxation by misfit accommodation at the base of the SLS and at individual strained interfaces is considered for the initial condition of full coherency and after partial relaxation. Experimental data for the Si-Ge strained layer system are presented; as-grown by MBE and after annealing in the temperature range 500°C – 900°C. The extent of relaxation and the detailed dislocation structure within the SLS's were determined by X-ray rocking curve analysis, Nomarski interference microscopy and transmission electron microscopy. The abrupt changes in relaxation behaviour indicate that rigid boundaries between stable and metastable structures do exist, as predicted by the equilibrium models.
Mismatch Dislocation Nucleation and Propagation in Si/Si1−xGex Heterostructures
Authors: Tuppen C G , Gibbings C J , Hockly M
Published: March 2011

Mismatch dislocation nucleation mechanisms have been studied in the Si/Si1−xGex materials system using the simple application of a selective, defect revealing chemical etch, followed by standard Nomarski optical microscopy. The onset of mismatch dislocation formation was found to occur at a point just above the equilibrium critical thickness limit set by Matthews and Blakeslee (he). However, the bulk of the material remained coherently strained until it reached a metastable critical thickness (hm), where hm >> he. Nomarski micrographs clearly show the initiation of the mismatch dislocation network and the major dislocation multiplication processes that occur at hm. At low levels of relaxation the individual mismatch dislocation half loops can be identified, and we show, for the first time, the evolution and propagation of these dislocations from nucleation sites in the epilayer. A dramatic decrease in hm has been observed for epilayers that contain a large number of intrinsic dislocations.

The mismatch dislocations were found to nucleate at extended defects and further relaxation occurred by dislocation multiplication at these sites. This gave rise to a non-uniform distribution of mismatch dislocations, with patches of highly relaxed material surrounded by material that was still coherently strained.
Interfacial Shear Strength of Thin Polymeric Coatings on Glass
Authors: Ritter J. E. , Rosenfeld L. , Lin M. R. , Lardner T. J.
Published: March 2011

The interfacial adhesive shear strengths of epoxy and acrylate coatings on glass substrates were measured by the indentation and lap shear tests. The lap shear strengths were about an order of magnitude less and exhibited considerably more variability than those measured by indentation. It is believed that the lap shear strength is controlled by large processing flaws (pores in this study); whereas, the indentation test measures the “intrinsic” strength of the coating.
Nanomechanics of Thin Films: Emphasis: Tensile Properties
Authors: Hoffman R. W.
Published: March 2011

Tensile properties of thin films may be interpreted as a structure sensitive plastic region superposed on an elastic background in a manner similar to bulk specimen tensile testing. However, the limitations of both the material and tensile instrument have not usually been tested in detail.

We report our experience with aluminum and alumina films some 100 nm thick prepared by evaporation of Al followed by anodization for the alumina film. Self-supporting films are glued to glass “jaws” of the nanotensilometer and force-elongation data recorded. Mounting thickness, glue slip-page, instrument calibration, and other possible artifacts will be examined in detail. A typical Al stress-strain curve has an initial small curved region interpreted as a mounting artifact, followed by a primarily elastic (near linear) region and increasing plastic deformation until failure occurs. Alumina films fail in a brittle manner. Characterization techniques include TEM, RBS, and other surface spectroscopies; selected examples will be reported. Strain rate and preliminary annealing data are presented with a microscopic interpretation.

In general, thin metal films are less ductile than their bulk counterparts, grain sizes are much smaller, and they may possess large stresses and unexpected impurities, but have mechanical properties that can be modelled.
Stress in Titanium Disilicide Layers, During and After Formation.
Authors: Jongste J. F. , Prins F. E. , Janssen G. C. A. M. , Radelaar S.
Published: March 2011

During and after formation of a thin layer of titanium disilicide (TiSi2) on a silicon substrate stress is caused in several ways: Intrinsic stresses are due to the deposition process or to phase transformations and grain growth of the deposited material. Extrinsic stresses are caused by thermal effects: the difference in linear thermal expansion coefficients of the layer and the substrate respectively. Problems related to stresses can occur in semiconductor device fabrication. Stresses can deteriorate gate oxides in MOSFETs and can cause cracks in interconnect lines. Also, focusing problems in lithographic steps can occur because of wafer warpage. In this paper some examples of the different types of stress that can occur are shown and discussed. Both multilayer and self aligned Ti-Si samples have been studied: The advantage of the use of Ti-Si multilayers to produce TiSi2 is that diffusion has to proceed only over a short distance i.e., the multilayer period. So the annealing time can be short. In the self aligned silicidation process, where a layer of a titanium layer on top of a silicon substrate is annealed, the diffusion length is equal to the thickness of the Ti layer. Because longer annealing times are needed, the latter type is used to monitor stress during formation.
The Behavior of Polysilicon Thin Film Stress and Structure Under Rapid Thermal Processing Conditions
Authors: Huber Walter , Borionetti G. , Villani C.
Published: March 2011

Undoped polysilicon layers deposited at 620 °C onto a silicon wafer induce a compressive stress of approximately 1 × 109 dynes/cm2 resulting in a bow of the wafer. This stress can be relieved by rapid annealing at temperatures above 1000 °C. A comparison with conventional furnace annealing reveals that the stress relaxation is a weak function of time and strongly depends on temperature. Rapid thermal processing also causes immediate rearrangement of the film structure, as observed by X-ray diffraction. Although both stress and film texture change with annealing, no conclusive relationship is observed.
Principles and Applications of Wafer Curvature Techniques for Stress Measurements in Thin Films
Authors: Flinn Paul A.
Published: March 2011

Measurement of the curvature induced in a wafer (or other flat plate) by the stress in a thin film has long been used as a convenient and accurate technique for the determination of the stress. Numerous improvements over the years have led to instruments that provide simple and rapid measurements of stress as a function of the time and temperature for any desired thermal history. A computer controlled instrument using laser scanning will be briefly described and its capabilities and limitations discussed.

Applications of the technique to a variety of thin film materials will be discussed. In addition to the effects of differences in thermal expansion, stresses associated with various deposition techniques, gain or loss of material, phase transformations and flow will be considered. In aluminum based systems, themal expansion, plastic flow and phase transformation play major roles. Refractory metals show, in addition, large stresses associated with the deposition process. In inorganic dielectric systems thermal expansion effects are usually relatively small; deposition effects and the gain or loss of material are the dominant effects. Silica based glasses formed by chemical vapor deposition, for example, show large stress changes due to gain or loss of water, and plasma deposited silicon nitride films show large effects associated with hydrogen. Overall, determination of the stress as a function of time and temperature is a valuable part of the evaluation of a thin film material for use in a VLSI device.
Measurement of the Sound Velocity in AlAs by Picosecond Ultrasonics
Authors: Young D. A. , Grahn H. T. , Maris H. J. , Tauc J. , Hong J. M. , Smith T. P.
Published: March 2011

Picosecond ultrasonics have been used to measure the sound velocity and index of refraction in a thin film of AlAs. The AlAs layer was grown by molecular-beam epitaxy on a buffer layer of GaAs which was deposited on a semi-insulating GaAs wafer. The AlAs film was capped by a thin layer of GaAs, and a very thin film of InSb. To generate a sound wave effectively a picosecond light pulse was absorbed in the InSb film. As the sound wave propagates through the microstructure it changes the optical properties in the various films, and this produces a change in the optical reflectivity, which is measured. From the round trip time of the acoustic wave we have determined the sound velocity in the AlAs film.
Measuring the Strength and Stiffness of Thin Film Materials by Mechanically Deflecting Cantilever Microbeams
Authors: Weihs T. P. , Hong S. , Bravman J. C. , Nix W. D.
Published: March 2011

The present authors recently introduced the mechanical deflection of cantilever microbeams as an experimental technique for measuring the strength and stiffness of thin films.[1] The technique utilizes conventional integrated circuit (IC) fabrication to process the samples, a Nanoindenter to deflect the cantilever beams mechanically, and simple elastic beam theory to analyze the data. This paper will review the technique and describe some of its current applications.
The Determination of Mechanical Parameters and Residual Stresses for Thin Films Using Micro-Cantilever Beams
Authors: Hong S. , Weihs T. P. , Bravman J. C. , Nix W. D.
Published: March 2011

A method for determining mechanical parameters and residual stresses for thin films is described. Multi-layer cantilever beams (LPCVD SiNx/thermal SiO2) are fabricated utilizing standard IC processing technologies and micromachining of silicon. The elastic response of the beams to imposed deflections is then measured using a Nanoindenter, a sub-micron hardness testing machine. The elastic constants of the nitride films are calculated from the force vs. deflection slope and known elastic constants of the thermal SiO2 and silicon. By measuring the curvature of the multi-layer cantilever beams with a scanning electron microscope after successive etching of the LPCVD nitride films, average and differential stresses in the films were calculated.
A Kinetic Model for Metalorganic Chemical Vapor Deposition of GaAs from Trimethylgallium and Arsine
Authors: Mountziaris Triantafillos J. , Jensen Klavs F.
Published: March 2011

A kinetic model for metalorganic chemical vapor deposition (MOCVD) of GaAs from trimethylgallium and arsine is presented. The proposed mechanism includes 15 gas-phase species, 17 gas-phase reactions, 9 surface species and 29 surface reactions. The surface reactions take into account different crystallographic orientations of the GaAs substrate. Sensitivity analysis and existing experimental observations have been used to develop the reduced mechanism from the large number of reactions that might in principle occur. Rate constants are estimated by using thermochemical methods and reported experimental data. The kinetic mechanism is combined with a two-dimensional transport model of a hot-wall tubular reactor used in experimental studies. Model predictions of gas-phase composition and GaAs growth rates show good agreement with published experimental studies. In addition, the model predicts reported trends in carbon incorporation.
Adsorption and Decomposition of Trimethylarsenic on GaAs(100)
Authors: Creighton J. R.
Published: March 2011

Alkylated arsenic compounds have shown some promise as alternatives to arsine as the group-V source gas for GaAs MOCVD. However, little is known about the fundamental chemical interactions of these compounds with the GaAs surface. We have investigated the adsorption and reactivity of trimethylarsenic (TMAs) on GaAs(100) using temperature programmed desorption (TPD), Auger electron spectroscopy, and LEED. For the exposures and temperatures studied, TMAs did not pyrolytically decompose on the GaAs(100). TPD results indicate that TMAs chemisorbs, apparently non-dissociatively, and desorbs ≅330 K. Multilayers of TMAs desorb ≅140–160 K. Exposure of adsorbed TMAs to 70 eV electrons results in irreversible decomposition of the molecule. After electron irradiation, TPD shows that methyl radicals desorb at 660 K, which corresponds to a desorption activation energy of ≅40 kcal/mol. At higher temperatures, As2, H2, C2H2, and a smaller amount of methyl radicals desorb, and a small coverage of carbon remains on the surface.
Electrochemical Photovoltaic Cell with 6.9% Efficiency using Polycrystalline CdSe Grown by a Simple Liquid Metal-Vapour Reaction
Authors: Lawrence Marcus F. , Deng Zhitsing , Gastonguay Louis
Published: March 2011

Research on II–VI semiconducting compounds during the last two decades has been motivated by possible device applications such as thin film transistors, photodetectors and solar energy converters. In particular, the direct gap n-type semiconductor CdSe, has remained the subject of studies aimed at developing efficient photovoltaic and photoelectrochemical cells. For the low-cost production of polycrystalline CdSe layers, many noteworthy methods have been employed, such as: vacuum deposition, spray pyrolysis, chemical bath deposition and electrodeposition [1–5]. The best reported performances of photoelectro-chemical cells using CdSe films obtained by these methods, in contact with an aqueous polysulfide electrolyte and under solar or simulated solar radiation, have varied between 5 and 7% [6,7].
Catalytic Oxidation of Silicon Nitride thin films Using Potassium*
Authors: Rogers J. W. , Blair D. S. , Peden C. H. F.
Published: March 2011

Thin silicon nitride films on a Si(100) substrate have been oxidized using potassium in a low thermal budget process. The presence of potassium on the SisN4 surface greatly lowers the temperature-time requirements for oxidation as compared with direct thermal oxidation.
Gas-Surface Reaction Studies Relevant to SiC Chemical Vapor Deposition
Authors: Stinespring C. D. , Freedman A. , Wormhoudt J. C.
Published: March 2011

Reactions of C2H4, C3H8, and CH4 on Si(111) and C2H4 on Si(100) have been investigated for surface temperatures in the range of 1062 K to 1495 K. These studies used x-ray photoelectron spectroscopy to identify the reaction products, characterize the solid state transport process, determine the nucleation mechanism and growth kinetics, and assess orienta-tion effects. The results are used to provide insight into the mechanisms of SiC CVD processes.
Chemistry of Nitrogen-Silane Plasmas
Authors: Smith Donald L. , Alimonda Andrew S. , Preissig Frederick J. Von
Published: March 2011

The N2-SiH4 rf glow-discharge plasma has been analyzed by line-of-sight mass spectrometry of species impinging on the deposition electrode, including N atoms. Properties of SixNyHz films deposited from this plasma have been examined. At high rf power and low SiH4/N2, almost all of the SiH4 is consumed by reaction with N atoms at the film surface and becomes incorporated into the film. No Si-N precursor species are seen in the gas phase. This is in contrast to the NH3-SiH4 plasma, where the Si(NH2)3 radical is the key precursor. If power is insufficient or SiH4 flow is excessive, Si2Hm species are generated in the plasma. Under optimized conditions, films slightly N-rich with no Si-H bonding and only 7% H (as N-H) can be deposited at high rate. The film tensile stress of the NH3 process is absent in the N2 process due to the lesser amount of condensation that takes place during deposition. However, trench coverage is much better in the NH3 process.
A Comparison Between Energetics of Decomposition and Photo-Deposition of Pd and Pt from Pd(C5 H5 )(C3 H5) and Pt(C5H5)(C3 H5)
Authors: Emrich Karl-Heinz , Stauf G. T. , Hirschwald W. , Barfuss S. , Dowben P. A. , Birge R. R. , Boag N. M.
Published: March 2011

The energetics of decomposition of a variety of organometallic compounds have been determined from photoionization mass spectroscopy and electron impact mass spectroscopy. In particular, Pd(C5H5)(C3H5) and Pt(C5H5)(C3H5) have been studied in this fashion, and the information used to make patterned Pd/Ni/Si heterostructures by laser induced photolysis of the palladium compound and nickelocene in vacuum (MOCVD). Contamination in the thin films was determined by Auger electron spectroscopy, and compared with that found by other researchers for photo-deposition of Pt from the cyclopentadiene allyl [1].Thermodynamic data is used to explain differing contamination levels in the Pd and the Pt coatings.
Alloy Thin Films from Discrete Metallaborane Clusters
Authors: Fehlner T. P. , Amini M. M. , Zeller M. V. , Stickle W. F. , PRINGLE O. A. , Long G. J. , Fehlner F. P.
Published: March 2011

The ferraborane HFe4 (CO)12 BH2 sublimes at 50 °C and decomposes by loss of H2 and CO on various substrate surfaces at 160–180 °C to yield films having metallic appearances with typical thicknesses of 4000Å. These films are amorphous by X-ray, conduct electricity and adhere well to glass, metal and silicon substrates. The composition was determined by ESCA and Auger spectroscopies. The films exhibit highly uniform composition and the Fe/B ratio is 4 showing that film stoichiometry is defined by the cluster core. The ESCA chemical shifts show the presence of boride and metallic iron. At present the bulk film contains a high level of oxygen in the form of iron and boron oxides. No ax-iron is present by X-ray or Mössbauer spectroscopies. Some carbon and hydrogen (SIMS) are present. Mössbauer spectra show the presence of magnetic iron similar to that exhibited by authentic Fe80 B20 samples but the films also contain substantial paramagnetic iron.
Dynamics of the KrF* Laser Multiphoton Dissociation of a Series of Arene Chromium Tricarbonyls
Authors: Tyndall George W. , Jackson Robert L.
Published: March 2011

The KrF* (248 nim) laser multiphoton dissociation (MPD) of a series of (arene)chromium tricarbonyls has been investigated in the gas-phase using emission spectroscopy to detect the excited state photoproducts. In the MPD of all compounds studied, chromium atoms are formed in a variety of electronically excited states via a two-channel dissociation mechanism. The predominant pathway for formation of the ground electronic state and the lowest excited states is by a sequential absorption/fragmentation process, where the product of the one-photon dissociation of the parent molecule absorbs an additional photon and dissociates to Cr(I). The higher energy Cr(I) states are formed exclusively by a direct dissociation process, where the parent absorbs multiple photons prior to dissociation. The distribution of excited chromium atoms formed in the direct channel is statistical for all compounds studied and is independent of the nature of the arene ligand. In contrast, the distribution of Cr(I) states formed via the sequential dissociation channel is strongly dependent on the vibrational density of states in the arene ligand.
Laser CVD of A-Si:H: Film Properties and Mechanism
Authors: Hesch K. , Hess P. , Oetzmann H. , Schmidt C.
Published: March 2011

Films of a- Si: Hwere deposited from Sill4 in a parallel configuration employing acw CO2 laser. Infrared spectra, photoconductivities and dark conductivities of the films were studied as a function of surface temperature between 250°C and400° C. The results are compared with data obtained from deposition experiments using Si2H6 and an ArF laser. Implications for the mechanism of LICVD are discussed.
Proximity Effect in the Low Pressure Chemical Vapor Deposition of Tungsten.
Authors: Lifshitz N.
Published: March 2011

The self-limiting effect during Low Pressure Chemical Vapor Deposition of tungsten is manifested by a sudden interruption of the reduction of tungsten hexafluoride WF6 by silicon, so that only very thin (self-limited) films of silicon-reduced tungsten can be grown. It has been shown that the self-limiting effect is caused by formation of the non-volatile subfluoride WF4. The temperature dependence of the self-limiting thickness of the tungsten films grown in a hot-wall reactor exhibits a characteristic maximum at temperatures near 350°C, which indicates that at this temperature the rate of formation of WF4 is lower than at temperatures above and below. In the present paper we attempt to explain this peculiar dependence. We suggest a mechanism responsible for formation of the blocking agent WF4. We demonstrate that the presence of a hot tungsten surface is essential for the strong self-limiting effect. This leads us to the discussion of the proper selection of the reactor type (hot-wall vs. cold-wall) for different process requirements.
Assessment of Organotellurium Compounds for Use as Movpe Precursors
Authors: Hails J. E. , Irvine S. J. C. , Mullin J. B. , Shenai-Khatkhate D. V. , Cole-Hamilton D.
Published: March 2011

In order to reduce the growth temperature of (Hg,Cd)Te by MOVPE below 350–400°C, alternative organometallic precursors will be required which either decompose at a lower temperature than existing precursors or which absorb strongly at a suitable wavelength in the ultraviolet. The features required for a programme of assessment of organometallics are discussed. UV absorption spectra for dimethyltelluride, dimethylditelluride, diethyltelluride, di-iso-propyltelluride and diallyltelluride are presented and their usefulness as photolytic MOVPE precursors discussed.
Gas Phase Interactions between Triethylindium and Trimethylgallium
Authors: Agnello P. D. , Ghandhi S. K.
Published: March 2011

A study of the room temperature gas-phase interactions between gallium and indium alkyls was undertaken using a mass spectrometer sampling system, mounted on a low pressure organometallic vapor phase epitaxial reactor. Mixtures of triethylindium with triethylgallium or trimethylgallium were investigated. Both combinations formed addition compounds; moreover, the triethylindium-trimethylgallium mixture underwent alkyl exchange. Both admixtures showed reduced reactivity towards arsine. A structure for the addition compound is proposed.
A New Look At Amorphous Vs Microcrystalline Structure
Authors: Spaepen Frans
Published: March 2011

Historically, non-periodic models have usually found preference over microcrystalline ones for describing the structure of amorphous materials. Nevertheless, truly microcrystalline materials do exist, and the characteristic, monotonically decreasing isothermal calorimetric signal associated with the growth of the grains, can sometimes be used to identify them unambiguously. An example of the identification of the micro-quasicrystalline structure of some sputtered aluminum-transition metal alloys is discussed.
Mechanism of Achieving Nanocrystalline AIRu By Ball Milling
Authors: Hellstern E. , Fecht H. J. , Garland C. , Johnson W. L. , Keck W. M.
Published: March 2011

We investigated through X- ray diffraction and transmission electron microscopy the crystal refinement of the intermetallic compound AIRu by high- energy ball milling. The deformation process causes a decrease of crystal size to 5–7 rum and an increase of atomic level strain. This deformation is localized in shear bands with a thickness of 0.5 to 1 micron. Within these bands the crystal lattice breaks into small grains with a typical size of 8–14 rum. Further deformation leads to a final nanocrystalline structure with randomly oriented crystallite grains separated by high- angle grain boundaries.
Preparation and Structure of Cu-W Multilayers
Authors: Unruh K. M. , Patterson B. M. , Shah S. I. , Jones G. A. , Kim Y.-W. , Greene J. E.
Published: March 2011

Sputtered multilayer samples of W and Cu have been prepared on a variety of substrates with nominal individual layer thicknesses ranging from about 5 to about 100 A. High angle X-Ray Diffraction (XRD) data have been obtained at room temperature on all of these samples. In addition, selected samples have been studied by Transmission Electron Microscopy (TEM) and by low and high angle XRD from room temperature to above the melting point of bulk Cu. XRD and TEM data indicate that the as-deposited multilayer samples are comprised of well-defined individual layers due, in part, to the very small mutual solubility of W and Cu. At high temperatures the existence of low angle scattering peaks as well as satellites about Bragg peaks indicates that the layered structure is not lost. As a result, the W-Cu multilayer system seems to be an interesting candidate for the study of the melting behavior of thin Cu layers.
Physical-Chemical Properties of TiO2 Membranes Controlled By Sol-Gel Processing
Authors: Xu Qunyin , Anderson Marc A.
Published: March 2011

Particulate TiO2 membranes have been prepared by sol-gel techniques from alkoxide precursors. The degree of aggregation, which is controlled by physical chemical processes during sol preparation influences the gelling volume and gel structure. While three types of gel structures have been proposed, the porosity of the final membrane seems to be little affected by these hydrogel structures. Firing temperature is a much more critical parameter. It is concluded that the primary particle size determines the final membrane porosity in this TiO2 system.
Infrared Properties of Thin Pt/Al2O3 Granular Metal-Insulator Composite Films
Authors: MacMillan M. F. , Devaty R. P. , Mantese J. V.
Published: March 2011

The reflection of mid- and near-infrared radiation (400-15000 cm−1 by thin Pt/Al2O3 cermet films was measured using a Fourier transform spectrometer. The data were compared with predictions of three models for the effective optical constants of heterogeneous materials: Maxwell-Garnett, Bruggeman, and a simplified version of a probabilistic growth model due to Sheng. Sheng's model provides the best description of the data over the complete range of metallic volume fraction. This result is expected based on the most likely topology of the films and is in agreement with other work on similar systems at higher frequencies.
Transmission Electron Microscope Observation of Dislocations in Ordered Intermetallic Alloys and the Flow Stress Anomaly
Authors: Veyssière Patrick
Published: March 2011

It is only within the last five years that, with the increasing interest of several specialized groups, the amount of accurate TEM information on dislocations in ordered alloys, and in particular in theL12structure, has become significant. Our knowledge on superdislocation cores related todeformation under various temperature and deformation modes, is now sufficiently documented in order to be critically reviewed and this is the object of the present contribution.