Showing papers on "Pulsed laser deposition published in 1987"

Preparation of Y‐Ba‐Cu oxide superconductor thin films using pulsed laser evaporation from high Tc bulk material

Abstract: We report the first successful preparation of thin films of Y‐Ba‐Cu‐O superconductors using pulsed excimer laser evaporation of a single bulk material target in vacuum. Rutherford backscattering spectrometry showed the composition of these films to be close to that of the bulk material. Growth rates were typically 0.1 nm per laser shot. After an annealing treatment in oxygen the films exhibited superconductivity with an onset at 95 K and zero resistance at 85 and 75 K on SrTiO3 and Al2O3 substrates, respectively. This new deposition method is relatively simple, very versatile, and does not require the use of ultrahigh vacuum techniques.

Formation of thin superconducting films by the laser processing method

Abstract: We have prepared thin films of Y‐Ba‐Cu‐O superconductors using a pulsed laser evaporation technique. Thin films were formed on (100) Si, (100) MgO, (1102) sapphire, (100) SrTiO3, and amorphous SiO2 substrates using a XeCl excimer laser (λ=0.308 μm, τ=45×10−9 s). The depositions were done in an ultrahigh vacuum chamber with pressure of about 10−6 Torr during thin‐film formation. The deposition by pulsed nanosecond laser irradiation results in stoichiometry close to that of the target. The thickness of the film was controlled by varying the pulse energy density and the number of pulses. The substrate temperature was kept at 470 °C during deposition. Subsequent annealing treatments were carried out at 900 and 650 °C in oxygen atmosphere to recover the superconducting properties of these thin films. The resistance of these films was measured as a function of temperature using the four‐point probe method. These thin films were analyzed using cross‐section transmission electron microscopy, Rutherford backscatt...

Method for forming a pattern of a film on a substrate with a laser beam

Abstract: An improved method for forming a pattern on a substrate coated with a film is shown The substrate is irradiated with a laser beam which is shaped through a mask, and a portion of the film is removed by the energy of the laser beam to produce the desired pattern The laser beam is emitted from an exmer laser

Kinetics of laser‐induced chemical vapor deposition of gold

Abstract: Rates of photothermal gold deposition onto alumina substrates heated by a focused argon‐ion laser beam were measured by determining the time required for deposits to grow through the focal spot of a HeNe laser probe beam directed parallel to the substrate. Deposition rates from 0.25 to 6 μm/s were measured for deposits with heights ranging from 5 to 100 μm. Rates of gold deposition using dimethyl gold hexafluoroacetylacetonate as a precursor depend linearly on the gold precursor partial pressure and for a wide variety of conditions do not depend on the laser power or focal spot diameter. A theory is presented to describe reactant mass transfer‐controlled deposition with and without buffer gas. Comparison of measured with calculated growth rates showed that gold deposition rates using dimethyl gold hexafluoroacetylacetonate as a precursor were transport limited for the conditions studied. Theory and experiment also showed that the deposition rate decreases inversely with increasing buffer gas pressure abov...

Photon, beam, and plasma stimulated chemical processes at surfaces

Abstract: These proceedings collect papers on beam/materials interactions. Topics include: ion beam processing, laser chemical processing, ion interactions during crystal growth, direct-laser writing, laser-driven thin film deposition, laser induced growth of insulators, low temperature epitaxy, ion damage, dry etching, the interaction of UV laser radiation with polymers, laser microfabrication techniques, and plasma deposition of tungsten.

Synchrotron radiation‐excited chemical vapor deposition of SixNyHz film

Abstract: The photochemical vapor deposition of SixNyHz films (y/x≤11) is demonstrated, using the vacuum UV (VUV) from synchrotron radiation (SR) for the first time In the configuration with the beam axis parallel to the substrate surface, the deposition rate achieved is about 005 nm/min for a 100 mA ring current and a 27/133 Pa SiH4/N2 pressure Values of about nine times larger are obtained in the perpendicular configuration It is shown that decomposition of adsorbed molecules by SR irradiation is the primary process involved in deposition in the perpendicular configuration

Growth rates and electrical conductivity of microscopic ohmic contacts fabricated by laser chemical vapor deposition of platinum

Abstract: The laser chemical vapor deposition of platinum from its bishexafluoroacetylacetonate derivative is studied with a cw argon ion laser at 458 and 514 nm. The height, the width, as well as the electrical conductivity of the deposited stripes are reported as a function of the vapor pressure of the metalorganic precurser, the laser intensity, and the writing speed.

The role of ion/surface interactions and photo-induced reactions during film growth from the vapor phase

Abstract: Recent progress in the understanding of mechanisms associated with low-energy (often during vapor-phase crystal growth are reviewed. Ion/surface interactions play an important role in a variety of deposition technologies including sputtering, plasma-assisted chemical vapor deposition, and, more recently, molecular beam epitaxy. Effects such as trapping, preferential sputtering, and collisional mixing are used to interpret and, in some cases, model experimental results concerning the effects of low-energy ion bombardment on nucleation and film growth kinetics, the evolution of film microstructure, elemental incorporation probabilities, surface segregation rates, and dopant depth distributions. The role of photo-stimulated gas-phase and surface reactions during laser-assisted chemical vapor deposition, including single, multiple, and multiphoton-initiated processes, radical production, and adlayer photochemistry, are also discussed together with newly developed laser-processing techniques during deposition. The focus of this review is on the development of an understanding of the controlling mechanisms in both ion/surface and photo-stimulated processes.

Apparatus for the formation of a functional deposited film using microwave plasma chemical vapor deposition process

Abstract: An improved apparatus for the formation of a functional deposited film using microwave plasma chemical vapor deposition process is characterized in that an opening and shutting member to form an opening for taking a substrate in or out a deposition chamber and the circumferential wall of the deposition chamber are sealed by an electromagnetic wave shielding means and a vacuum sealing means being arranged in this order from the side of the microwave plasma generating space, which prevent deterioration of the vacuum sealing means and makes it possible to repeatedly form a desired functional deposited film of high quality at a high deposition rate.

Excimer laser initiated chemical vapor deposition of tungsten films on silicon dioxide

Abstract: Photochemical vapor deposition technique using an ArF excimer laser has been employed to deposit W films on SiO2 and Si from a WF6 and H2 system Adhesion characteristics of the film to SiO2 are found to depend both on substrate temperature and on H2/WF6 gas flow ratio: good adhesion is obtained with an increase in the temperature or the ratio Film formation has reaction orders of 1, 1/2 , and 1 with respect to deposition time, and WF6 and H2 partial pressures, respectively An activation energy of 036 eV is estimated for this film formation on both SiO2 and Si; this energy is plausibly due to H atom diffusion on the W surface These findings are different from conventional thermal chemical vapor deposition Film resistivities as low as about 2× the value of bulk W have been observed in the substrate temperature range 250–500 °C The crystalline structure of the film deposited in this temperature range is uniquely of the α phase The crystal orientation of the film depends both on substrate temperature

Method for vapor phase deposition of gallium nitride film

Abstract: A process for depositing a gallium nitride film on a substrate. A source compound is provided which has the formula: H.sub.3 GaNR.sub.3 Each R is independently selected from alkyl groups having from 1 to about 4 carbon atoms. The source compound is conveyed into a deposition chamber containing a substrate. The source compound, maintained in the gaseous phase, decomposes in the deposition chamber and optionally reacts with other materals in the deposition chamber. Gallium nitride is deposited on the substrate as a result.

Apparatus for the formation of a functional deposited film using microwave plasma chemical vapor deposition process

Abstract: An improved apparatus for the formation of a functional deposited film using a microwave plasma chemical vapor deposition process comprising a substantially enclosed deposition chamber having a deposition space, a supporting means for a substrate on which a functional deposited film is to be formed being placed in the deposition space, a means for supplying a raw material gas, a means for evacuating the inside of the deposition chamber, a microwave introducing means being provided with the wall of the deposition chamber and a waveguide being extended from a microwave power source, characterized in that said microwave introducing means is comprised of laminated two or more microwave transmissive plates made of a dielectric material and the surface of the outermost transmissive plate to become faced to the deposition space is of a roughened surface having a roughness of 1.5 μm to about 1 cm for the height between the projection and the depression by the arithmetic mean for at least selected ten points.

Nucleation effects in visible‐laser chemical vapor deposition

Abstract: A low power, focused, argon ion laser beam ∼514.5 nm has been used to controllably and reproducibly deposit micron‐size metallic films on transparent glass and quartz substrates. Film growth proceeds via the pyrolytic decomposition of organometallic molecules on nucleation sites. The nucleation sites can be created over the entire substrate by flood exposure with deep ultraviolet light in the presence of organometallic vapor or in micron size areas by forming an initial deposit and then scanning the substrate across the focused laser beam. The latter nucleation technique has been extended to the deposition of metal on chrome‐on‐glass photomasks. Here metal deposition proceeds in three distinct time periods: surface modification (fast), nucleation (slow), and film growth (fast). The visible‐laser chemical vapor deposition technique has been used to demonstrate the repair of defects in photomasks with a resolution approaching 1 μm.

Multi-pulse laser nitridation of titanium, zirconium and hafnium in a nitrogen atmosphere containing oxygen

Abstract: Quantitative data are reported on the surface nitridation of titanium, zirconium and hafnium samples by multi-pulse microsecond-pulsed high-intensity TEA CO2 laser irradiation in nitrogen atmospheres containing oxygen impurities. The possibility of controlling the competition between oxidation/nitridation processes by recording the reflectivity of the pulsed laser action zone in the light of a supplementary, low-power CW CO2 laser source is revealed.

Localized laser chemical processing of tungsten films

Abstract: A focused argon‐ion laser beam at 514 nm was used to thermally induce localized tungsten deposition from a WF6:H2 mixture. Tungsten lines were deposited on silicon wafers coated with either boron nitride (BN) or polyimide. Typical linewidths range from 0.5 to 10 μm, and the thicknesses from 0.1 to over 1 μm. Linewidth correlated most strongly with laser power, while the thickness correlated best with the laser fluence delivered to the sample. A minimum threshold laser power is needed to attain the temperature for deposition. The process is self‐limiting since the deposited metal increases the surface reflectivity and thermal conductivity, thus increasing the threshold laser power. A feedback system based on measuring the reflected laser power during deposition was used to modulate the incident power and defeat the self‐limiting nature of the process, thus allowing tungsten lines to be connected. Tungsten deposition and etching using other gases are reported for contrast with the deposition using WF6:H2 mi...

Method for selective deposition of metal thin film

Abstract: A metal thin film is deposited on predetermined portions of an underlayer of a substrate by a chemical deposition method with good selectivity, good reproducibility and high deposition rate by preventing hydrogen atoms from the adhesion to portions of the substrate not to be deposited with a metal using a special means for heating only the substrate or a special gas flow controlling means.

Apparatus for the formation of a functional deposited film using microwave plasma chemical vapor deposition process

Abstract: An improved apparatus for the formation of a functional deposited film using microwave plasma chemical vapor deposition process is characterized in that the relative setting angle between waveguides confronting each other is set to be 60° or 240° in the counterclockwise direction, which makes it possible to stably introduce the microwave energy into the vacuum chamber simultaneously from the plural microwave power sources without any interference among them.

Laser Photochemical Growth of Amorphous Silicon at Low Temperatures and Comparison with Thermal Chemical Vapor Deposition

Abstract: Pulsed ArF (193 nm) excimer laser radiation has been used to dissociate disilane (Si/sub 2/H/sub 6/, resulting in photochemically controlled deposition of amorphous Si thin films. A high stability HeNe (6328 A) laser was used for precise in situ monitoring of film deposition rates, under varying deposition conditions. A helium window purge nearly eliminated Si film deposition on the chamber windows. With the excimer laser beam parallel to the substrate, deposition of amorphous Si can be controlled entirely by the photon fluence (negligible background thermal growth) at temperatures from room temperature up to /approximately/400/degree/C. Reasonable photolytic deposition rate (>1 A/sec) are combined with 'digital' control of film thickness (/approx gt/0.02 A/laser pulse). Activation energies of 1.50 (+-0.1) eV and 0.09 (+-0.02) eV were found for pyrolytic and photolytic deposition, respectively. 15 refs., 3 figs.

Real time optical profilometry as a probe of rates of laser‐induced chemical vapor deposition

Abstract: An optical method for the measurement of rates of laser induced chemical vapor deposition processes is described. Vertical growth rates are obtained from measurements of the power attenuation by a growing deposit of a probe beam of known diameter directed parallel to the substrate and intersecting the axis of the deposit. A theoretical analysis is presented that relates the growth rate of deposits with various geometries to the attenuation of the probe beam as a function of time and the probe laser beam diameter. The method can be used to obtain growth rates for deposits as small as a few μm in height, as long as the surface of the deposit is smooth relative to the diameter of the probe beam. The method is used to determine rates of photothermal gold deposition as a function of gold precursor partial pressure. Measured deposition rates ranged from 0.2 to 5.5 μm/s for dimethyl gold hexafluoroacetylacetonate partial pressures from 0.03 to 0.62 Torr.An optical method for the measurement of rates of laser induced chemical vapor deposition processes is described. Vertical growth rates are obtained from measurements of the power attenuation by a growing deposit of a probe beam of known diameter directed parallel to the substrate and intersecting the axis of the deposit. A theoretical analysis is presented that relates the growth rate of deposits with various geometries to the attenuation of the probe beam as a function of time and the probe laser beam diameter. The method can be used to obtain growth rates for deposits as small as a few μm in height, as long as the surface of the deposit is smooth relative to the diameter of the probe beam. The method is used to determine rates of photothermal gold deposition as a function of gold precursor partial pressure. Measured deposition rates ranged from 0.2 to 5.5 μm/s for dimethyl gold hexafluoroacetylacetonate partial pressures from 0.03 to 0.62 Torr.

Compact Laser Source for Metal Deposition

Abstract: For the past few years, there has been considerable interest in using lasers for the directed deposition of metal [1,2,3,4]. Part of this interest is driven by technological applications in microelectronics. In particular, this includes the rapid interconnection of gate arrays [5] and the repair of defects in photomasks [6]. The techniques used for the laser patterning of metal include Laser Chemical Vapor Deposition (LCVD) [7], and the decomposition of spin-coated organometallic inks [8]. In the first process, LCVD, a laser with a power of several hundred milliwatts or more is used to irradiate a substrate in the presence of an organometallic vapor. The substrate is chosen so that it absorbs the the incident laser radiation while, in general, the organometallic vapor is transparent at the laser wavelength. The absorption of the laser energy by the substrate results in a temperature rise which depends on the thermal properties of the substrate. If the temperature rise is sufficient, organometallic molecules impinging on the irradiated area decompose. Non-volatile components (such as metal fragments) remain on the surface and form a deposit. In the second process, decomposition of organometallic films, a substrate which was previously spin coated with an organometallic ink is irradiated wherever metal patterns are desired. The ink decomposes in these areas leaving a film of metal. The unirradiated areas of the ink are then washed away with a suitable solvent. Such processes have been extensively studied and developed using primarily argon, krypton, and CO 2 lasers [1,2,3,4]. In general these lasers are large, expensive, require maintenance, and raise reliability concerns. These characteristics add to the challenge of introducing laser deposition processes into the manufacturing environment.

Laser plasma deposition and film structure of covalently bound materials

Abstract: The pulsed laser plasma method has been applied for deposition of thin films. Peculiarities of the technique in relation to the kinetics of layer growth are investigated.

Initial Stage of Laser-Induced Selective Chemical Vapor Deposition of Silicon

Abstract: Spatially selective chemical vapor deposition has been achieved by ArF excimer laser (193 nm) irradiation through a metal mask in a Si2H6 + He gas mixture. The selective deposition kinetics has been found to be controlled by a nonthermal process and has been explained in terms of the Langmuir-Hinshelwood mechanism. Both surface migration of adsorbed radicals and desorption of reaction products appear to be enhanced with the laser irradiation, leading to a selective nucleation of silicon.

Bonded Hydrogen in Silicon Oxide Thin Films Deposited By Remote Plasma Enhanced Chemical Vapor Deposition

Abstract: We have deposited a range of silicon oxides by the Remote Plasma Enhanced CVD method. By varying gas mixtures and/or substrate temperature, it is possible to deposit films that are essentially stoichiometric SiO_, Si-deficient oxides which have OH groups but no SiH and Si-rich oxides which have SiH groups and no OH. This paper addresses three issues : (1) the nature of the infrared vibrations associated with the SiH and SiOH groups; (2) the use of D for H substitutions to study the vibrations in (1); and (3) the chemical origin of the SiOH group in the Si-deficient films.

Superconducting thin Films of (RE)Ba 2 Cu 3 (Ag)O 7 x Prepared by Pulsed Laser Ablation

Abstract: Thin films of (RE)-Ba-Cu-O perovkites containing silver were prepared by pulsed Nd:YAG (wavelength 1064 nm) laser ablation. Presence of the 1:2:3 phase was verified by scanning Auger microscopy. Onset of the d.c. resistive superconducting transition of 85 K was observed. Films with and without silver were compared and the potential benefits of silver inclusion are discussed.