bluuebunny/crossref_metadata_2025_split huggingface dataset:
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

ABSTRACTWe 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

ABSTRACTAn 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

ABSTRACTWe 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

ABSTRACTSubstrate 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

ABSTRACTVarious 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

ABSTRACTSi (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

ABSTRACTWe 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

ABSTRACTDynamical 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

ABSTRACTThe 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

ABSTRACTThe<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

ABSTRACTThe 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

ABSTRACTIn 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.
The Stability of Si-Si1-xGex Strained Layer Heterostructures.
Authors: Houghton D. C. , Baribeau J-M. , Song K. , Perovic D. D. 
Published: March 2011

AbstractThe 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

AbstractMismatch 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

AbstractThe 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

AbstractTensile 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

AbstractDuring 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

AbstractUndoped 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

AbstractMeasurement 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

AbstractPicosecond 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

AbstractThe 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.