bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Crystallization and Amorphization of Si from the Melt at Interface Velocities Approaching 20 m/sec
Authors: Poate J. M. 
Published: March 2011

ABSTRACTLaser melting has been used to controllably vary the Si solidification velocity in the range 1–20 m/sec. The segregation of implanted impurities is found to be critically dependent on the liquid-solid interface velocity and substrate orientation for velocities <10 m/sec. This behavior can be understood in terms of different degrees of undercooling of the melt. While the (100) epitaxy is generally excellent up to velocities ∼10 m/sec, twins are observed for (111) epitaxy in the range ∼5–10 m/sec. Amorphous Si is produced from the melt for velocities in the vicinity of 20 m/sec. The amorphous phase forms at lower velocities on the (111) interface than on the (100) interface. These estimates of interface velocities come from heat flow calculations which do not include undercooling of the melt. Undercooling does not affect interface velocities ∼3 m/sec but significant lowering of the higher velocities could result from such effects.
Calculation of Carrier and Lattice Temperatures Induced in Si and GaAs By Picosecond Laser Pulses
Authors: Lietoila A. , Gibbons J. F. 
Published: March 2011

ABSTRACTA previously presented computer model was used to calculate melt thresholds and carrier temperatures in crystalline silicon and gallium arsenide subjected to picosecond laser pulses at 532 nm. The energy relaxation time of hot carriers was a variable parameter. For Si, a thermalization time of 1 ps yields results which are in very satisfactory agreement with published experimental data: the melt threshold is 0.19 J/cm2, and the maximum carrier temperature for the threshold pulse is 5500 K. The melt threshold in GaAs is substantially less, 0.03 J/cm2 for a thermalization time of 1 ps.
Amorphous Germanium Crystallization Processes in Multi-Pulse Low Power Laser Irradiation
Authors: Bertolotti M. , Vitali G. , Zammit U. , Marinelli M. 
Published: March 2011

ABSTRACTThe regrowing features of disordered germanium under low power multi-pulse irradiation are discussed. It is shown that implanted amorphous germanium starts the regrowth from the specimen surface while glow-discharge amorphous material starts from the amorphous-single crystal interface. Evidence against a melting mechanism in the case of multi-pulse irradiation are also presented.
In Situ Laser Recrystallization of CVD Silicon Films
Authors: van der Leeden G. A. , Young R. T. , Appleton B. R. , Narayan J. 
Published: March 2011

ABSTRACTPolycrystalline silicon films were deposited on singlecrystal silicon substrates from a SiH4 –H2 mixture at 660°C and epitaxially recrystallized with ruby laser pulses during the deposition. The surface morphology was found to depend critically on the surface conditions of the substrate. Using appropriate cleaning procedures, 0.5 and 1.0 micron thick layers were deposited and laser recrystallized during the deposition. Ion scattering/channeling analysis showed that the layers were single crystalline with a high degree of perfection. Using TEM, dislocation densities of 103–104 cm−2 were found, but some areas were dislocation free.
Zone Refining Of Nonsubstitutional Impurities During Pulsed Laser Annealing
Authors: White C. W. , Naramoto H. , Williams J. M. , Narayan J. , Appleton B. R. , Wilson S. R. 
Published: March 2011

ABSTRACTA large number of impurities which do not form covalent bonds with silicon cannot be incorporated into the lattice at measurable (by RBS) concentrations by pulsed laser annealing. At low concentrations the impurities can be zone refined to the surface, while at high concentrations the interface becomes unstable during regrowth leading to a cell structure. For each impurity there is a critical concentration required for interfacial instability to develop. The results are in qualitative agreement with a simple model for solute trapping and zone refining which assumes that the impurity diffusivity in the interfacial region is intermediate between that of the liquid and the solid.
An Ion-Scattering Study of Oxygen Indiffusion During Pulsed Laser Annealing/Cleaning of Silicon
Authors: Westendorp J.F.M. , Wang Z.L. , Saris F.W. 
Published: March 2011

ABSTRACTOxygen indiffusion during pulsed laser annealing of silicon has been studied using the 186 O(α,α) 186 O resonance at 3.045 MeV. Anneals were carried out with a Q–switched ruby laser, energy density of the pulses 1.5 J/cm2 , pulse width 20 ns. No evidence for oxygen indiffusion was found, neither for ion–implanted single pulse air–annealed silicon nor for a silicon wafer, cleaned with 8 laser shots in a UHV environment. In the latter case, the upper limit of the oxygen concentration was found to be 3.1 * 1018 at/cm3 , which is lower than the solid solubility limit of oxygen in silicon. The non–occurrence of indiffusion is consistent with the dissolution time of SiO2 in Si, which is orders of magnitude longer than the melt duration of the Si–substrate.
Photoemission Results for Laser-Annealed Si(111) and Ge(111) Surfaces
Authors: Himpsel F.J. , Eastman D.E. , Heimann P. , Reihl B. , White C.W. , Zehner D.M. 
Published: March 2011

ABSTRACTWe have studied the valence band and surface-core-level states for laser-annealed, thermally-annealed, and cleaved Ge(111) and Si(l11) surfaces with high resolution photoelectronspectroscopy using synchrotron radiation. For the annealed surfaces we find two surface states near the top of the valence band as well as characteristic surface core level spectra. These indicate the existence of a common local bonding geometry for all these surfaces. We observe that the (1 × 1) and cleaved (2 × 1) surfaces are not related as recently reported for Si.
Emission of Charged Particles from Laser Irradiated Silicon
Authors: Liu J.M. , Yen R. , Kurz H. , Bloembergen N. 
Published: March 2011

ABSTRACTEmission of charged particles from (111) and (100) crystalline silicon surfaces during and following picosecond pulsed laser irradiation in vacuo has been investigated.No thermionic electron emission is observable, setting an upper limit of 5000°K on the electron temperature during the laser pulses at 532 nm and at 266 nm. Equal number of positive and negative particles are emitted when the laser energy fluence is sufficient to cause vaporization of a few surface layers. Significantly larger amount of electrons than that of positive particles are emitted under irradiation with UV pulses at low energy fluences. This phenomenon can be tentatively explained by thermally enhanced photoelectric emission from a molten silicon surface.The presence or absence of the emission of charged particles sets important lower or upper limits on the temperature of the electrons and of the lattice. Our data are fully consistent with a model of complete thermalization between carriers and lattice on a time scale of 10–11 sec.
The Characterisation of Laser and Electron Beam Annealed Silicon by Infrared Spectrophotometry
Authors: Pawlik Marek 
Published: March 2011

ABSTRACTAn exact model of the IR reflectance and transmission spectra of inhomogeneously doped silicon has been developed. By comparing theoretically and experimentally generated spectra in the range 1.2 to 25 μm, information about the doping profile may be deduced. The technique has been applied to laser and electron beam annealed silicon (as well as furnace annealed) and comparisons made with theoretical profiles and SIMS analysis in the latter case. No values consistent with other published data have been found for the optical properties of silicon at high doping levels (>1020 cm−3).
Quenched-In Defects in CW Laser-Annealed Si
Authors: Sheng N.H. , Merz J.L. 
Published: March 2011

ABSTRACTDLTS has been used to investigate the nature of CW laser-induced defects in ion-implanted Si. A dominant hole trap (∼Ev + 0.45 eV), whose concentration depends on laser power, was observed immediately after sample preparation. This defect is not stable at room temperature; instead, it decays as a function of time, transmuting to a shallow level at Ev + 0.10 eV. The recovery of the Ev + 0.45 eV level can be stimulated by low temperature thermal annealing or by minority carrier injection. By comparing these defects in laser-annealed samples with defects produced by furnace annealing followed by rapid cooling, and with other published results, the laser-induced defects have beenidentified as interstitial Fe and Fe-B pairs. Experiments suggest that elevated substrate temperature during laser annealing may inhibit the formation of these deep hole traps.
Correlated Electrical and Microstructural Studies of Recrystallized Silicon Thin Films on Bulk Glass Substrates
Authors: Biegelsen D. K. , Johnson N. M. , Nemanich R. J. , Moyer M. D. , Fennell L. E. 
Published: March 2011

ABSTRACTTo determine the nature and effect of defects which occur in the growth of crystalline semiconductor films on amorphous substrates, one must carry out microstructural and electrical studies on the same material regions. In previous publications we have demonstrated that by controlling optical absorption in and around delineated silicon areas, the nucleation and growth processes can be controlled. In this way we have been able to produce single crystal islands >20 μm on a side. Using a simple, novel parylene lift –off technique we can now routinely study the material crystallized on bulk glass using transmission electron microscopy. We report here preliminary results of correlated electrical and structural studies on pre – patterned silicon films crystallized under various conditions. Electrical characterization consists mainly of I – V measurements on diodes and MOSFETS fabricated in the crystallized material by conventional silicon IC processing techniques. For microstructural characterization of the same devices we rely on TEM, EBIC and spatially– resolved Raman scattering.
Defect Formation in CW CO2 Laser Annealed Silicon
Authors: Baumgart H. , Phillipp F. , Leamy H. J. 
Published: March 2011

ABSTRACTThe EBIC mode of the SEM has been used to investigate the perfection of cw CO2 laser annealed Si. Even in material that contains no slip lines, non-uniform charge collection is found. A combined X-ray and electron microscopy (TEM, SEM) study identified the residual defects responsible for the EBIC contrast as interstitial submicron dislocation loops. Scanning cw laser annealing independent of the wavelength (10.6μm or 0.514μm) always introduces residual defects which act as recombination centers and reduce minority carrier lifetime.
Metallurgy and Microstructures of Pulse Melted Alloys
Authors: Follstaedt D. M. 
Published: March 2011

ABSTRACTThe microstructures found in pulse melted metals are reviewed. Epitaxial resolidification and the defects found in pure metals are discussed. Pulse melted alloys are then examined in order of increasing complexity. First, single phase alloys which solidify into metastable solid solutions are discussed. For higher concentrations and liquid-insoluble species, phase separation can occur, and the requirements for such separation are identified. If precipitation does not reduce the impurity concentration of the liquid, the liquid may be quenched to an amorphous solid. Comparisons of ion-implantation and pulse-melt produced amorphous alloys are given.
Pulsed Laser Annealing of Al, Ni, and MgO Containing Nickel Precipitates
Authors: Narayan J. 
Published: March 2011

ABSTRACTWe have investigated the generation of point defects and dislocations, and the formation of dislocation loops as a function of pulse energy density in laser annealed Al, Ni, and MgO containing nickel precipitates. In the case of Al where vacancies are mobile above 200 K, mostly vacancy loops were observed at room temperature in laser melted layers. Dislocations are formed below the laser-melted layers as well as in specimens treated with pulses below the melting threshold, due to thermal stresses. In the case of Ni (where vacancies are mobile above 373 K) the microstructure in room temperature laser annealed specimens consists of primarily dislocations and their tangles. In MgO:Ni crystals, enough laser energy was absorbed to melt nickel precipitates. The dislocation structure around the precipitates and the transformation of nickel precipitates from coherent into incoherent, provided information on melting and crystal growth of these precipitates.
Defects and AlSb Precipitate Nucleation in Laser Irradiated Aluminum
Authors: Peercy P. S. , Follstaedt D. M. , Picraux S. T. , Wampler W. R. 
Published: March 2011

ABSTRACTLattice defects and precipitates induced in unimplanted and Sb-implanted <110> single crystal Al by single pulse irradiation with a Q-switched ruby laser were studied using ion beam analysis and electron microscopy. The absorbed laser energy during irradiation is directly measured in these studies to allow precise numerical modeling of the melt times and temperature profiles. For unimplanted Al, slip deformation gives rise to increased channeled yields throughout the analyzed depth and occurs for energies well below the melt threshold energy of 3.5 J/cm2. Slip deformation is also observed for irradiation energies above the melt threshold energy, and melting is accompanied by a discontinuous increase in the minimum channeling yield, X min- Implanted Sb (to ∼2 at.% peak concentrations) is found to impede epitaxial regrowth and result in polycrystalline Al formation for laser energies such that the melt front is believed not to penetrate through the Sb-containing region. For deeper melt depths, a metastable alloy is formed with up to 35% of the Sb located in substitutional sites. AlSb precipitate formation in the melt was not observed for room temperature irradiations; however, randomly oriented AlSb precipitates are observed for irradiation at substrate temperatures of 100 and 200 °C These measurements yield an estimated time for nucleation of AlSb precipitates in molten Al of 5 nsec < tnuc < 25 nsec.
Pulsed Electron Beam Melting of Fe
Authors: Knapp A. , Follstaedt D. M. 
Published: March 2011

ABSTRACTPulsed (50 nsec) electron beams with deposited energies of 1.1 ­ 2.4 J/cm2 have been used to rapidly melt a surface layer of Fe. Calculations show that this range of energies produces melt depths from 0.4–1.2 μm and melt times of 100–500 nsec. Optical microscopy and SEM of pulse treated polycrystalline foils show slip traces, as well as a general smoothing of surface features which shows that melting has occurred. TEM shows that the resolidified material is bcc, and that the material within a grain is epitaxial with the substrate. TEM also shows slip traces of {110} planes, as well as a high density of dislocations, both extended and loop. At the highest energy, subgrain boundaries are observed. Some samples were implanted with 1×1016 Sn/cm2 at 150 keV. After pulse treatment, the Sn depth profile was observed to have broadened, consistent with liquid phase diffusion. The Sn had the unexpected effect of suppressing slip at the sample surface.
Epitaxial Silicide Formation by Scanning Electron Beam Annealing
Authors: Ishiwara Hiroshi , Yamamoto Hiroshi 
Published: March 2011

ABSTRACTEpitaxial growth of Pd2Si films on Si(lll) substrates by scanning cw electron beam annealing is investigated theoretically and experimentally. First, the nonlinear heat conduction equation is solved in a substrate with finite thickness to estimate the surface temperature during annealing. Then, the optimum growth conditions are experimentally determined, in which annealing parameters such as the beam current intensity, the scan speed, and the overlap width are changed. It has been shown by Rutherford backscattering and channeling techniques that the crystalline quality of the e-beam annealed Pd2Si films is somewhat worse than that of the furnace-annealed films.
Study of Titanium and Nickel Silicide Formation By Q-Switched Laser and Multiscanning E-Beam
Authors: Bentini G.G. , Nipoti R. , Berti M. , Drigo A.V. , Cohen C. 
Published: March 2011

ABSTRACTThe use of Q-switched ruby laser and multiscanning electron beam annealing (MEBA) to produce the reaction of thin Ti and Ni films deposited onto single crystal Si has been studied. Laser annealing produces a reaction at the interface between the metal and the semiconductor; the reacted layers are not uniform in composition and more similar to a mixture than to a well-defined phase. The silicide layers produced by MEBA results from the solid state reaction of whole metal layer and have well-defined compositions and sharp interfaces between phases and the underlying crystal. The observed thicknesses of the silicides produced by MEBA cannot be accounted for by the parabolic volume diffusion mechanism operating in the standard furnace annealing. Post annealing treatments in furnace showed that e-beam produced silicides have the same thermal stability as those produced by conventional heat treatments. The presence of a critical temperature for silicide formation in Ti/Si MEBA annealed samples has been confirmed and studied in detail.
Laser Fabrication of Silicon on Dielectric Substrates
Authors: Leamy H. J. 
Published: March 2011

ABSTRACTThe growth of device-worthy silicon crystals on insulating substrates would have a revolutionary impact upon microelectronics, and is consequently the object of intense effort. This article reviews recent progress in the application of laser and electron beams and incoherent light to this end. In every case, radiant energy is employed to melt a precursor material, from which device-worthy layers are produced during resolidification. Techniques include seeded and unseeded growth, partial and complete encapsulation of the liquid layer, and oscillation of the solid-liquid interface. Considerations of liquid zone stability, temperature gradient control, and interface morphological stability are central to each technique. Progress in this field has been rapid and several techniques have been successfully demonstrated.
Optical Characterization of Chemically Vapor Deposited and Laser-Annealed Polysilicon
Authors: Bagley B. G. , Aspnes D. E. , Celler G. K. , Adams A. C. 
Published: March 2011

ABSTRACTThe optical properties of polysilicon on insulating SiO2 were measured by spectroscopic ellipsometry over the energy range 3.0 to 6.0 eV. Spectra were obtained for films as-deposited and after irradiation with an Ar ion laser (focused to a 50μm spot diameter) at 6.0, 7.0 or 7.5 watts. We observed monotonic changes in both ε1 and ε2 with increasing incident power even though the power density was high enough to completely melt the silicon surface in all cases. The changes observed are caused by changes in microstructure; with increasing power the amorphous component decreases and the density increases. Approximate values of the microstructural components are estimated by comparing measured spectra to those synthesized from constituent spectra in the Bruggeman effective medium approximation.
A Model for Laser Beam Induced Solid-State Crystal Growth in Silicon On Sapphire
Authors: Burgener M. L. , Reedy R. E. , Csanadi O. 
Published: March 2011

ABSTRACTAn analytic model is presented for laser beam induced solid-state crystal growth in silicon on sapphire. The model, which assumes a single activation energy, utilizes temperature profiles calculated from a Green's function solution to the heat equation. Calculated crystal growth in silicon on sapphire is compared to experimentally measured values.
Fast Scan Laser Annealing
Authors: Schott John T. 
Published: March 2011

ABSTRACTLaser-annealing phenomena have typically been divided into two distinct realms. Pulsed lasers involved very short anneal times and small deposited energy densities. Slowly scanned cw lasers involved intermediate times (ms range) and larger energy densities. Repetitively scanned electron beams have extended the range of anneal time and energy density toward conventional thermal processing. This paper examines the regime between pulsed laser annealing and conventional cw laser annealing. By greatly increasing the scan speed of the laser, annealing times and deposited energy densities are reduced and approach those of pulsed laser annealing. Applications are discussed in the areas of silicon-on-insulator recrystallization, low resistivity poly, vertical integration, local lateral seeding, explosive crystallization, and line-source simulation.
Optical, Structural and Electrical Characteristics of Explosively Crystallized Si Thin Films on Glass Substrates
Authors: Auvert G. , Bensahel D. , Perio A. , Morin F. , Rozgonyi G.A. , Nguyen V.T. 
Published: March 2011

ABSTRACTExplosive Crystallization occurs in cw laser annealing on a-Si films deposited on glass substrates at laser scan speeds higher than 30 cm/sec. Optical, structural and electrical properties of the crystallized films at various laser scan speeds confirm the existence of two kinds of explosive growth depending on the state of crystallinity of the starting material.
Shaping of Dopant Concentration Profiles in Silicon by Multiple–Pulse Laser Processing
Authors: Hill C , Butler A L , Daly J A 
Published: March 2011

ABSTRACTOver the past ten years, the performance of bipolar transistors in high speed integrated circuits has been steadily improved by fully exploiting the complex solid state diffusion behaviour of dopants in silicon to make successively closer approaches to the ideal dopant profiles in the emitter and base regions of the transistor. Further optimisation requires a new approach, and in this paper an entirely new method of shaping the dopant profiles by exploiting the large ratio (about 108) of diffusion coefficients in liquid and solid silicon near the melting point is described Melting is effected by irradiation with a homogenised pulse from a Q-switched ruby laser. Completely new features of the technique are the controllable fabrication of both quasi–Gaussian and quasi-rectangular dopant profiles independent of dopant (arsenic or boron), dopant concentration (1013−1016atom cm−2) or presence of other dopants. This allows for the first time independent optimisation of emitter profile shape, emitter doping level, and base profile in bipolar transistor structures.
Characteristics of Interpoly Oxides Optimized by Conventional Processing and Laser Annealing
Authors: Eggermont G.E.J. , Rodeen H.D. , Brors D.L. 
Published: March 2011

ABSTRACTTo improve the dielectric properties of thin oxides grown on polysilicon, a matrix of conventional process variables such as phosphorus doping level and oxide growth temperature, and the inclusion of laser recrystallization of the polysilicon have been investigated. For conventionally processed wafers, highest dielectric strengths were obtained at the highest oxidation temperature (1150°C) and a simultaneous low doping level in the polysilicon. Similarly high dielectric strengths were obtained after cw-Ar laser recrystallization of the polysilicon at much lower temperatures (900°C), independent of the doping level in the polysilicon.
Pulsed–Raman Measurements of Temperature When Large Temperature Variations and Gradients are Present
Authors: Wood R. F. , Rasolt M. , Jellison G. E. 
Published: March 2011

ABSTRACTPulsed Raman temperature measurements by Lo and Compaan on Si samples have been interpreted as proving that the surface region does not melt during intense pulsed laser irradiation. In this paper, it is shown by detailed calculations with the melting model that the choice of experimental parameters in the Raman measurements can severely compromise a straightforward interpretation of the data. Moreover, it is demonstrated that temperatures extracted from Raman measurements are highly sensitive to the temperature-dependent optical properties of the material. Finally, it is pointed out that the very large temperature gradients present during pulsed laser annealing may entirely invalidate the Stokes/anti-Stokes ratio as an accurate temperature probe.