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Presents a study which compared two processes of ultraviolet laser incorporation of dopants into silicon. Method of the study; Results and discussion; Conclusion.

Deals with a study which deposited silicon oxide, oxynitride and nitride films at low temperature by pulsed argon fluoride excimer laser ablation from silicon, silicon monoxide, fused silica and silicon nitride targets, performed under vacuum and in an oxygen atmosphere. Experiment; Influence of laser fluence; Optimization of the process conditions to deposit good quality silicon oxide and silicon nitride thin films.

Investigates the effects of deposition temperature on silicon dioxide film properties. Information on high-purity bulk silicon monoxide; Method used to measure film thickness; Infrared absorptions for laser ablation-deposited silicon dioxide.

Reports the deposition of yttrium barium copper oxide and bismuth strontium calcium copper oxide superconducting thin films performed using the single-laser pulse-induced forward transfer technique. Information on the optical absorption of the amorphous films as a function of wavelength; Measurement of the film thickness; Analysis of the superconducting properties of the laser transferred layers.

Abstract: In this study, nanofiltration (NF) and reverse osmosis (RO) were used in laboratory scale to concentrate As containing wastewater. Cross flow membrane filtration apparatus was applied in batch mode with recycling the retentate. Then the retentate of membrane filtration was treated with lime (Ca(OH)2) and sulfur hydrogen (H2S) to help the precipitation for producing clean water and a low volume, highly concentrated As waste. [Copyright &y& Elsevier]

Abstract: In this work was investigated numerically and experimentally a simple laser doping method employing borosilicate (BSG) glass films as dopant sources which are deposited onto Si by the spin-coating technique. Both short (20ns) and long (200ns) pulse duration Excimer laser beams were used to deposit a large amount of energy in short time onto the near-surface region. Under suitable conditions, the irradiation leads to surface melting and dopant incorporation by liquid phase diffusion from the surface. Boron distribution profiles in the two-pulse duration regimes were studied as well as their electrical properties, and the junction formation of less than 25nm in depth was demonstrated. [Copyright &y& Elsevier]

Abstract: As of today, several lead-free soldering pastes have been qualified for currently used soldering process. Regarding the new potential of laser-assisted soldering processes, the behaviour of the SnAgCu soldering paste requires, however, new investigations. In the first part of this study, the specific temperature profile of a laser soldering process is investigated using a high power diode laser (HPDL). These experimental results are compared to a thermal simulation developed for this specific application. The second part of this work deals with the diffusion of the tin-based filler material through the nickel barrier using the information extracted from the temperature simulations. [Copyright &y& Elsevier]

Carbon nitride films have been deposited by ArF excimer laser ablation of a graphite target in the 10−2 to 100 Pa N2 pressure range. Arrival rates of the constituting elements, mass densities and apparent growth rates have been derived from areal densities of both carbon and nitrogen atoms, determined by ion beam techniques, and film thicknesses, measured by a mechanical stylus. Below 5 Pa the film building blocks are atoms and molecules while above ∼50 Pa the formation and interaction of clusters and particles determine the film growth. The results reveal that the formation, composition and microstructure of carbon nitride films fabricated in this process window is governed by gas-phase processes. [Copyright &y& Elsevier]

As an alternative to classical thermal heating, laser annealing (LA) was recently demonstrated to be suitable for the electrical activation of ion-implanted dopants in SiC. In this work, we demonstrate the possibility to anneal the Al+ ion-implantation induced damage into 4H-SiC by solid phase laser processing using a XeCl excimer source of 200 ns-pulse duration. The electrical activation of the Al dopant was confirmed by I–V measurements performed directly on mesa pn junction diodes. [Copyright &y& Elsevier]

Amorphous carbon nitride (a-CN[sub x] ) films were grown on silicon substrates by ArF excimer laser ablation of a graphite target in the presence of nitrogen at various gas pressures. By working at elevated pressures (up to 100 Pa), large amounts of nitrogen can be incorporated into the films (up to 40 at. %, which leads to a strong enhancement of their field emission properties. This behaviour was demonstrated to be mainly related to changes in the surface morphology of the samples, in connection with the development of graphite-like structures. [ABSTRACT FROM AUTHOR]

Amorphous carbon nitride (a-CNx) films were grown on silicon substrates by ArF excimer laser ablation of a graphite target in the presence of nitrogen at various gas pressures. By working at elevated pressures (up to 100 Pa), high amounts of nitrogen can be incorporated into the films (N/C≤0.4) which lead to strong enhancement of their field emission properties. This behaviour was demonstrated to be mainly related to changes in the surface roughness of the samples, in connection with the development of graphite-like structures. [Copyright &y& Elsevier]

Amorphous carbon nitride (CNx) films were grown on silicon substrates by ArF laser ablation (PLD) of a graphite target in presence of nitrogen at various gas pressures. These films have been measured by spectroscopic ellipsometry in the UV–vis and IR wavelength range. In the UV–vis range, the optical indices of the CNx films have been extracted accurately using a model including surface roughness. The optical indices of the films are modelized by a Forouhi dispersion law model and the thickness and roughness are adjusted at the same time. The optical gap is extracted from the extinction coefficient. In the IR spectral range, the conductivity of the films is extracted from the Drude tale model. These structural and optical results are compared to the physico-chemical results provided by Rutherford backscattering (RBS) and elastic recoil detection analysis (ERDA). [Copyright &y& Elsevier]

Abstract. An ArF excimer laser (22 ns, 193 nm) and a hybrid dye/excimer laser system (500 fs, 248 nm) are used to deposit amorphous carbon nitride films at room temperature by ablation of a graphite target in nitrogen atmosphere. The chemical composition and structure of the films is characterized by X-ray photoelectron spectroscopy. In the nanosecond case, the nitrogen content increases with reactive gas pressure up to 45 atomic %, while in the subpicosecond case it remains below 7 at. %. When processed with nanosecond pulses, the films' nitrogen content steeply increases with fluence up to a maximum. The target-to-substrate distance has only minor influence on the amount of nitrogen incorporated into the films. The dependence of the carbon-carbon and carbon-nitrogen bond configurations on the processing parameters is also given. [ABSTRACT FROM AUTHOR]

Abstract. In this work, the excimer-laser-induced crystallization of a-Si films on SiO[sub 2] was investigated using a long-pulse-duration (200 ns) XeCl source. The microstructural analysis of the laser-irradiated area, for incident energy densities comprised between the thresholds corresponding to the surface and full melting, respectively, of the Si layer, was performed by scanning electron microscopy and Raman spectroscopy. A super-lateral-growth regime was evidenced quite comparable to that which occurs when classical excimer laser pulses of short duration (is approximately equal to 20 ns) are used. A numerical simulation of the surface melt dynamics was also performed and compared to the experimental observations. [ABSTRACT FROM AUTHOR]

Silicon dioxide thin films are deposited, for the first time, by reactive laser ablation from a silicon monoxide target in oxygen atmosphere, with a high-power pulsed ArF (λ=193 nm) excimer laser. The specific influence of oxygen in the chamber during the laser processing on the stoichiometry and final properties of the oxide films deposited at ambient temperature is demonstrated. [ABSTRACT FROM AUTHOR]

Oxygen incorporation and subsequent oxidation of ion-implanted silicon have been performed using repetitive pulsed excimer laser irradiation working in the liquid phase regime. The kinetics of the oxidation and the characterization of the grown SiO2 were investigated by infrared spectroscopy. The origin of the broadening of the Si-O stretching band of these oxides grown from the liquid phase is discussed. [ABSTRACT FROM AUTHOR]

We have investigated laser-induced oxidation of ion-implanted Si using a repetitively pulsed ArF laser, working at low-energy density (100–500 mJ/cm2). Oxidation is observed at energy densities between the melt threshold and that required for epitaxial recrystallization of the amorphous layer. At these energy densities, oxidation is not observed on virgin silicon. The factors that influence the oxidation process are discussed. [ABSTRACT FROM AUTHOR]

Silicon monoxide and silicon dioxide form insulating films that are commonly used in microelectronic devices. In the technology of devices containing silicon, the insulating silicon dioxide films are formed on the silicon wafers using conventional methods of thermal oxidation. This technique, which requires long periods of annealing (30–60 min) and high temperature ([bar_over_tilde:_approx._equal_to]1000 °C), is known to induce different types of physical degradation in the device. In this letter, we demonstrate the possibility of converting silicon monoxide deposited at room temperature to silicon dioxide by rapid thermal annealing. Although the annealing temperature is high (700–1100 °C) the time is very short (within seconds), so that this process may still be compatible with the requirements of low-temperature processing. [ABSTRACT FROM AUTHOR]

Formation of epitaxial Si1-yCy substitutional alloy layers on monocrystalline silicon surfaces with y≊1 at. % is reported. The preparation method was carbon ion implantation, followed by KrF excimer laser annealing. Results of Rutherford backscattering (RBS), secondary ion mass spectrometry (SIMS) and infrared absorption analyses are compared. The authors concluded that, up to ∼1 at. % carbon content, the dominant process is nonequilibrium trapping of carbon in substitutional lattice sites upon fast resolidification. Above this concentration the complex carbon redistribution processes are influenced by silicon carbide precipitation in the melt and segregation effects in the near-surface region. © 1996 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Investigates the ability of Si[sub 1-x]Ge[sub x] thin films to grow on single crystal silicon by pulsed excimer laser ablation. Dependence of the stoichiometry of the deposits on the Ge enrichment of the ablated target surface; Derivation of crystalline layers for substrate temperatures; Optimization of laser irradiation conditions.

Investigates optical emission characteristics of vacuum ultraviolet light from large area electrical gas discharges. Illustration of the reactor assembly used; Deposition of a-Si:H and Si[subx]N[subx]; Emission spectra from photo-chemical vapor deposition induced in argon-silane mixtures.

The rapid control of laser crystallisation during in-line large area flat panel display fabrication using polysilicon (poly-Si) thin-film transistors (TFT’s) is of growing importance.In this work, the microstructural analysis of the laser irradiated area has been studied with atomic force microscopy (AFM) and phase stepping microscopy (PSM), the latter being an automated mode of interference microscopy that allows the rapid and non-destructive measurement of nanometric surface morphology. The evolution of the crystallisation process in amorphous silicon (a-Si) thin films irradiated using large and long duration (200 ns) excimer laser (308 nm) pulses as a function of different key parameters such as the laser fluence, the beam homogeneity and the number of laser shots has been studied. We show that PSM, although having a lower lateral resolution than AFM, is capable of detecting the important super lateral growth (SLG) region.From the comparison of the results obtained by interference microscopy and AFM, the PSM technique has been shown to be an interesting alternative way that could be used for the quantitative calibration of the laser annealing process in an industrial environment. [Copyright &y& Elsevier]

Interference microscopy is a useful analytical tool for studying the surface morphology of semiconductors. Surface roughness from nanometres to many microns can be measured rapidly and non-destructively, making it possible to analyse fragile materials. Blue–violet illumination gives submicron lateral resolution and a large field size can be achieved using sample scanning and image ‘stitching’. Some of these new developments in interference microscopy are presented and applied to the optimisation of laser annealing of a-Si layers for flat panel displays, and to the analysis of surface morphology of HgI2 and PbI2 for nuclear detectors. [Copyright &y& Elsevier]

Abstract: This work presents the Continuous Wave (CW) laser crystallization of thin amorphous silicon (a-Si) films deposited by Plasma Enhanced Chemical Vapor Deposition (PECVD) and by Electron Beam Evaporation (EBE) on low cost glass substrate. The films are characterized by Elastic Recoil Detection Analysis (ERDA) and by Fourier-Transform Infrared (FTIR) spectroscopy to evaluate the hydrogen content. Analysis shows that the PECVD films contain a high hydrogen concentration (∼10at.%) while the EBE films are almost hydrogen-free. It is found that the hydrogen is in a bonding configuration with the a-Si network and in a free form, requiring a long thermal annealing for exodiffusion before the laser treatment to avoid explosive effusion. The CW laser crystallization process of the amorphous silicon films was operated in liquid phase regime. We show by Electron Backscatter Diffraction (EBSD) that polysilicon films with large grains can be obtained with EBE as well as for the PECVD amorphous silicon provided that for the latest the hydrogen content is lower than 2at.%. [Copyright &y& Elsevier]

We present a study of the temperature non-homogeneities induced by millisecond laser annealing in advanced CMOS technologies at die level. Because of the design, the device layout at the wafer surface introduces during this anneal significant spatial variations of optical absorption and heat transfer that can induce temperature non-uniformities over the die, often called 'pattern effects'. These temperature variations are becoming a major issue, since they are the origin of significant device properties dispersion. A complete optical and thermal simulation set has been developed to estimate the temperature variations induced by the topologies at the wafer surface during the laser anneal process. The modelling has been validated by either a comparison with another software or reflectometry and electrical measurements on real structures. This work demonstrates that the temperature variations are caused either by optical coupling or by thermal properties dispersion present at the wafer surface at the anneal step. Finally, we demonstrate that the impact of the thin-film interferences and diffraction phenomena is the critical issue for these pattern effects. [ABSTRACT FROM AUTHOR]

Abstract: The purpose of this work is to determine the optimal parameters required to crystallize thin amorphous silicon films on glass substrate with a continuous wave (CW) laser diode (λ =808nm), using a numerical model developed in COMSOL Multiphysics. The numerical simulation of the laser crystallization process takes into account the solid–liquid phase change and the difference between the melting temperature of amorphous (Tma-Si =1420K) and that of crystalline silicon (Tmc-Si =1690K). We have varied the main parameters controlling the crystallization process, namely the power and the scan speed of the laser beam. Furthermore the initial temperature as well as the thickness of the a-Si:H layer were also taken as a parameter to optimize the process. We have determined the melting, crystallization and ablation energy threshold versus the different operational parameters. [Copyright &y& Elsevier]

Abstract: Lithium niobate thin films were deposited on sapphire substrate by radio-frequency magnetron sputtering technique. One and two dimensional structures have been made using a KrF excimer laser at 248nm and 6ns pulse width, under various conditions of ablation, in order to assess the applicability of laser direct-writing of photonic waveguides. The optical and waveguiding properties of LiNbO3 thin films were studied by prism-coupling technique, while micro-Raman spectroscopy was used for structural and composition characterization, as well as laser processing mechanism investigation. The surface morphology of the processed structures was obtained by a Nomarski optical microscope, an atomic force microscope and a White Light Interferometer Microscope. [ABSTRACT FROM AUTHOR]

Abstract: Due to the continuous CMOS transistor scaling requirements, highly doped shallow junctions with improved activation have been widely investigated in recent CMOS technologies. In this scope, sub-melt millisecond laser annealing has been introduced in the integration flows to enhance dopant activation, without any additional detrimental diffusion. This MSA step impacts not only the transistor junction properties, but also the polysilicon gate depletion. This paper is devoted to the study of the MSA influence on boron and germanium co-implanted polysilicon films. A sensitive boron diffusion occurring during the laser anneal step, with or without an initial spike annealing step, has been observed. The activation energy of the boron diffusivity extracted from SIMS profiles in the laser only sequence has been found equal to 4.05eV. In addition, it was shown that either a high temperature laser anneal sequence or a spike anneal followed by a laser anneal sequence can reach the same activation levels. [Copyright &y& Elsevier]

Abstract: Due to the continuous CMOS transistor scaling requirements, sub-melt millisecond laser annealing has been introduced in 45nm CMOS technology to enhance dopant activation without any additional diffusion. Because of the design, the device layout at the wafer surface introduces during this process significant variations of optical absorption and heat transfer that can induce temperature non-uniformities over the die, detrimental to the device and often called “pattern effects”. The introduction of an absorbent layer above the wafer reduces the optical properties dispersion, but the temperature variations generated by the thermal properties non-homogeneities cannot be suppressed. The impossibility to measure directly this local transient temperature effects on complex transistors layout requires simulation. A thermal simulation has been developed and calibrated to model with accuracy the laser annealing with the real process parameters. This model is used to obtain the transient temperature distribution over the devices, which is needed to understand the laser impact on the transistors performance. We demonstrate that the shallow trench isolation (STI) filled with silicon oxide is critical for these thermal pattern effects. Depending on the STI layout density, temperature variations up to 50°C over a die are observed. [Copyright &y& Elsevier]

Abstract: In this work, we report on the fabrication and characterization of surface microstructures in lithium niobate thin films and single crystal by using KrF excimer laser ablation technique at 248nm with 6ns pulse width. Ablation is carried out through a mask projection set-up. Various experimental conditions are used in order to evaluate the potential of laser direct writing for photonic waveguides fabrication in lithium niobate. The surface morphology of the processed structures was studied by optical and atomic force microscopy. Laser processing mechanism is investigated by using micro-Raman spectroscopy. [Copyright &y& Elsevier]

Abstract: This paper contributes to the old problem of droplet formation by providing detailed quantitative data on the population statistics of particulates deteriorating the surface of boron carbide films produced by PLD. Films of 180±30nm thicknesses have been fabricated by KrF excimer laser ablation of a sintered B4C target in high vacuum. Number densities and size distributions of the particulates are given for 14 films, deposited at laser fluences tuned between 2 and 14Jcm−2, as a result of evaluating SEM images of the same magnification taken from minimum five different areas (altogether (2–4)×10−2 mm2) of each film. The overwhelming majority of the droplets is small with diameters, d ≤1μm. The number density of those with d ≤0.5μm ranges from (1 to 7)×104 mm−2. The effect of gradual deterioration of the target surface as a result of prolonged irradiation screens practically totally the effect of changing fluence. The number of droplets of diameters in excess of 1μm increases linearly with increasing number of shots/site resulting in maximum surface coverage values as high as 36%. [Copyright &y& Elsevier]

A series of boron carbide films of 180±30 nm thickness has been deposited by KrF excimer laser ablation of a sintered B4C target in high vacuum. Rutherford backscattering spectroscopy revealed that the chemical composition of the films grown on Si substrates, at room temperature, at laser fluences tuned between 2 and 14.3 J cm−2 varied depending not only on the actual laser fluence but also on the past record of the B4C target. Parallel SEM mapping of both film and target surfaces pointed to a correlation between changes in film composition, droplet density and target surface deterioration. This correlation is discussed in detail. [Copyright &y& Elsevier]

We propose a low cost technique for the production of diffractive optical elements (DOE). These elements are devoted to high power lasers beam shaping in the mid-infrared wavelengths. This process called laser ablation lithography (LAL), may seem similar to laser beam writing (LBW) in the way the whole DOE’s design is reproduced pixel by pixel on the substrate placed on a computer controlled XY translation stage. A first difference is that the photoresist is not exposed with UV light but is directly ablated with short excimer laser pulses. Furthermore, with LAL technique the size of the smallest pixel (5 μm×5 μm) is more than 10 times greater than those produced by LBW. We discuss in details the experimental set-up for LAL and demonstrate that it gives a resolution up to 10 times greater than photolithography with flexible masks. This makes LAL a promising solution for the production of DOE for use with Nd:YAG lasers. New applications of DOEs are finally introduced with high power lasers sources, such as laser marking or multi-point brazing. [Copyright &y& Elsevier]

Carbon films have been deposited by ArF excimer laser ablation of a graphite target in argon ambient of pressures between 10−4 and 200 Pa. Besides carbon, ex situ RBS and ERDA measurements reveal the presence of argon, hydrogen and oxygen in the films. Below 0.5 Pa the apparent growth rate, defined as the measured thickness per number of pulses, is almost constant at around 0.30 A˚ per pulse. Between 0.5 and 5 Pa it drops to 0.15 A˚ per pulse. The most salient feature of the pressure dependence is the unexpected increase in the apparent growth rate between 5 and 100 Pa. Above 100 Pa the growth rate further decreases below 0.07 A˚ per pulse. Parallel AFM measurements reveal characteristic differences in the surface morphology in each domain. Comparative analysis of the dependence of parameters characteristic of film growth and the evolution of microstructure on argon pressure provides information on the growth mechanism up to 200 Pa. [Copyright &y& Elsevier]

Carbon nitride films deposited by ArF excimer laser ablation of a graphite target in the 1–100-Pa N2 pressure and 1.0–10-J cm−2 fluence domains differ not only in their nitrogen but also in their oxygen content. The (surface) oxygen content correlates well with the compactness of the films. Oxygen contents below approximately 8 at.%, smooth surface, and mass densities above 2.2 g cm−3 are typical of films deposited at low N2 pressures (and high fluences) while deposition at/above 50 Pa results in films of oxygen contents exceeding 12 at.%, rough surface consisting of loosely connected cluster agglomerates, and density values at approximately 1.4 g cm−3. At medium pressures high fluence processing is advantageous in terms of both nitrogen content and film morphology. [Copyright &y& Elsevier]

Results of a comparative XPS study on 26 carbon nitride samples of different chemical composition fabricated by ablating a graphite target with an ArF excimer laser in N2 atmosphere while systematically varying the pressure in the 1–100-Pa and the laser fluence in the 1.0–10-J cm−2 domains are reported. N1s core level spectra recorded on all samples are consistently fitted by four components at 398.2, 399.4, 400.7 and 402.1 eV, respectively. Changes in the relative abundance of the individual spectral components of the N1s lines as a function of laser fluence and nitrogen pressure are interpreted in terms of changes in the chemical environment around nitrogen atoms. When present in low concentration, nitrogen atoms prefer sites allowing pyramidal configuration. With increasing concentration more and more atoms form C&z.sbnd;N&z.dbnd6;C type bonds, nevertheless, in all films the majority of the nitrogen atoms occupies pyramidal configurations. [Copyright &y& Elsevier]

Carbon nitride films deposited onto room temperature silicon substrates by ArF excimer laser ablation of a graphite target in nitrogen atmosphere have been investigated after floating off in transmission electron microscope (TEM). All films fabricated in the 1–100 Pa N2 pressure and 1–10 J cm−2 fluence domain are amorphous. It is the nitrogen pressure that governs both the composition and the morphology of the films, the effect of the laser fluence being weaker. The morphologies range from dense films grown in 1–5 Pa N2, to structures composed of carbon nitride clusters and voids between them, obtained at and above 50 Pa N2. Ablation with pulses of high fluence (10 J cm−2) results in more compact films. The oxygen content determined by energy dispersive X-ray spectrometry well correlates with the compactness of the films, being significantly higher in those fabricated at higher pressures and composed of clusters. [Copyright &y& Elsevier]

Abstract. Diamond-like carbon (DLC) films have been grown on Si substrates at ambient temperature by the pulsed-laser ablation technique, using pulses of different durations both in the nano- and picosecond ranges and at various energy fluences. The stability of these films was investigated as a function of thermal anneals performed in UHV conditions up to 1273 K. Their physico-chemical properties have been characterized by different techniques including X-ray photoemission, Auger electron and electron-energy-loss spectroscopies, Raman scattering, spectroscopic ellipsometry and atomic-force microscopy. The thermal stability of the films has been demonstrated to be related to their initial structural (sp[sup 3]/sp[sup 2] ratio) and chemical (contaminant) properties. DLC layers prepared under optimized conditions have been found to show a very good thermal stability up to 900 K. [ABSTRACT FROM AUTHOR]

Abstract. Silicon-based thin films have been obtained by the direct photodissociation of mono- or disilane gases in a windowless CVD reactor using the vacuum ultraviolet (VUV) argon emission generated by electrical discharges. Atomic force microscopy, Raman scattering and elastic recoil detection analysis techniques were applied to characterize the surface morphology, the structural properties, and the hydrogen content of the deposits, respectively, as a function of the silicon hydride concentration in the feed gas and, to a lesser extent, of the substrate temperature. Independent of the hydride concentration, it is found that the layers have a low hydrogen content of the order of 5% to 10%. On the other hand, their surface roughness is limited to a few nanometers providing that the partial hydride gas pressure in the reactor does not exceed 10 Pa. Raman investigations show that two different types of material can be obtained: either a purely amorphous one for hydride concentrations not exceeding 10% or a mixture of Si submicrocrystals embedded in an amorphous medium for the higher concentrations. Given the conditions of the growth technique used and the photodissociation mechanisms involved, it is concluded that a homogeneous nucleation process occurs already within the gas phase, leading to the formation of nanosized Si grains, that may agglomerate before reaching the substrate where a further growing step eventually takes place. [ABSTRACT FROM AUTHOR]