Showing papers on "Sputtering published in 1987"

Ion beam modification of insulators

Abstract: 1. Ion Ranges and Energy Deposition in Insulators (J.P. Biersack). 2. The Sputtering of Insulators (R. Kelly). 3. Characterization Techniques for Ion Bombarded Insulators (J.A. Borders). 4. Defect Creation in Ion Bombarded Inorganic Insulators (A. Perez, P. Thevenard). 5. Ion Beam Modification of Glasses (G.W. Arnold, P. Mazzoldi). 6. The Mechanical and Tribological Properties of Ion Implanted Ceramics (C.J. McHargue). 7. Synthesis of Dielectric Layers in Silicon by Ion Implantation (I.H. Wilson). 8. Ion Beam Effects in Organic Molecular Solids and Polymers (T. Venkatesan, L. Calcagno, B.S. Elman, G. Foti). 9. Condensed Gases (W.L. Brown). 10. Optoelectronic Materials (G. Gotz). 11. Ferromagnetic Garnets (P. Gerard). 12. Nuclear Waste Materials (Hj. Matzke). 13. Role of Defects on the Aqueous Dissolution of Ion-Bombarded Insulators (G. Della Mea, J.-C. Dran, J.-C. Petit). 14. Chemical Effects of Ion Bombardment (G.K. Wolf, K. Roessler). 15. Ion Beam Effects on Thin Film Adhesion (J.E.E. Baglin). 16. Astrophysical Implications of Ions Incident on Insulators (L.J. Lanzerotti, R.E. Johnson). Subject Index. Appendix: Tables of Ion Ranges in Insulators.

An intrinsic stress scaling law for polycrystalline thin films prepared by ion beam sputtering

Abstract: The intrinsic stresses of Al, Ti, Fe, Ta, Mo, W, Ge, Si, AlN, TiN, and Si3N4 films prepared by ion beam sputtering were investigated at low Td/Tm values. The intrinsic stress is compressive and its origin is explained in terms of the ion peening model. Knock‐on linear cascade theory of forward sputtering is applied to derive a simple scaling law with the film’s physical properties. The results show that the stress is directly proportional to the elastic energy/mole, given by the quantity Q=EM/(1−ν)D, where E is Young’s modulus, M the atomic mass, D the density, and ν Poisson’s ratio. Stress data taken from the literature for a variety of materials deposited by low‐pressure magnetron sputtering, and rf and ion beam sputtering also fit the correlation with Q. Furthermore, the model predicts a square‐root dependence on the incident ion energy, suggesting that the stress is momentum rather than energy driven.

Modeling of reactive sputtering of compound materials

Abstract: An experimentally verified useful new model for reactive sputtering is presented. By considering the total system (target erosion, gas injection, chamber wall deposition, reactive gas gettering at all surfaces, etc.) during deposition it is possible to evaluate quite simple relationships between processing parameters. We have expanded earlier treatments to include these phenomena. The model involves that gettering of the reactive gas takes place at the target and at the walls opposite to the target. Arguments are also presented for how the sputtered materials (elemental target atoms and the formed compound) contribute to the formation of the surface composition of the walls opposite to the sputtering electrode. The mass flow of the reactive gas has been chosen as the independent parameter in this presentation. Results for partial pressure and sputter rate are presented. The theoretical values are compared with experimental results from reactive sputtering of TiN. It is also pointed out that the calculated...

Tribological and electrical properties of metal‐containing hydrogenated carbon films

Abstract: The formation of metal‐containing amorphous hydrogenated carbon films (a‐C:H) in a reactive sputtering process is reported. The layers were prepared at room temperature using various metals of different concentrations. According to tribological measurements the layers exhibit small friction values and an extremely low abrasive wear rate. The electrical conductivity depends on the metal concentration and could be varied over many orders of magnitude.

Dry etching of silicon carbide

Abstract: The invention comprises a method of etching silicon carbide targets. In one embodiment, a reactive ion plasma is formed from a gas which is easily dissociated into its elemental species in the plasma, for which all of the dissociated elemental species are volatile in the plasma, and for which at least one of the elemental species is reactive with silicon carbide. The silicon carbide target to be etched is positioned on one of the electrodes which is formed from a material with a low sputter yield and which material reacts with a dissociated species to thereby prevent contamination of the target with either sputtered materials from the electrode or polymerized species from the plasma.

Computer simulations of sputtering

Abstract: Monte Carlo simulations have become a useful tool for studying ion radiation effects at or near surfaces or interfaces, such as sputtering, reflection, mixing, etc. The principal advantage of Monte Carlo calculations is that any physical process can be included directly. Also multielement and multilayer targets, even complex geometries, can be treated exactly in order to simulate realistic cases. The present paper will concentrate mainly on sputtering calculations with the Monte Carlo code TRIM, which treats ion and recoil transport in amorphous matter. It is based — as are analytic theories and most other Monte Carlo codes — on binary collisions with target atoms initially at rest. Over the past few years, the basic physical input has been greatly improved. Both the interatomic potentials and the electronic stopping powers proved to be of crucial importance even for the lowest energies occurring in recoil cascades. With the Kr-C or universal potential and the recent ZBL electronic stopping, which includes the Z oscillations, and a planar surface binding energy set equal to the heat of sublimation, realistic sputtering predictions could be obtained for most metals — without the use of any adjustable parameters.

Stress and microstructure of sputter‐deposited thin films: Molecular dynamics investigations

Abstract: In magnetron sputter deposition the intrinsic mechanical stress of films of refractory metals passes a tensile stress maximum, decreases and then becomes compressive with decreasing working gas pressure. To elucidate the dependence of internal tensile stress on film growth and microstructure, a two‐dimensional molecular dynamics simulation is employed. The evolving structure is determined at an atomic level and the stress is calculated as a function of the kinetic energy of adatoms and fast neutralized inert gas atoms which arrive at the film surface. These energies are dependent on the deposition geometry and the working gas pressure. The theoretical results are in qualitative agreement with experiment and reveal that the initial increase in tensile stress with increasing adatom and neutral incident kinetic energy is caused by a microstructural change from microcolumnar growth to a more densely packed atomic network with closed micropores. Interatomic attractive forces producing tensile stress can act mo...

Preparation and substrate reactions of superconducting Y-Ba-Cu-O films

Abstract: Multiple metal‐target dc magnetron sputter deposition of a metallic YBa2Cu3 alloy in pure Ar followed by ex situ oxygen annealing was used to prepare superconducting films on various substrates. This work particularly examines film‐substrate reactions which are degrading to superconductivity. Better superconductors were obtained using predeposited buffer layers, notably on cubic zirconia and MgO substrates covered with Ag and Nb. Best films have Tc=80 K, metallic resistivities with resistance ratio≳2, and critical current density ≲10 kA cm−2 at 4.2 K. Normal‐state resistivity measurements were made for O2 furnace temperatures up to 850 °C. Procedures for lithographically patterning these films are also described.

Shock wave mechanism for cluster emission and organic molecule desorption under heavy ion bombardment

Abstract: Mechanism for large cluster emission during sputtering of solids and bioorganic molecule desorption under ion bombardment via formation and emergence of shock waves originating from some high density energy spikes due to collision cascades or Coulomb explosions on fast heavy ion paths is proposed. The peculiarities of large cluster emission and the dependence of the bioorganic molecule desorption yield on energy loss, angle of incidence, and charge state of the primary ions are compared with the available experimental data. The energy and the angular distributions of the desorbed molecules are discussed.

Pulsed laser etching of high Tc superconducting films

Abstract: Etching of Y‐Ba‐Cu‐O superconducting thin films has been accomplished using a pulsed excimer laser (248 nm, 30 ns). Etch depth as a function of the number of laser pulses was linear over a wide range of incident laser energy densities. An etch threshold energy density of 0.11 J/cm2 was observed and etch rate per pulse scaled linearly with the logarithm of the incident energy density. The dependence is adequately explained by a linear absorption model with an inverse absorption length of 2.3×105 cm−1.

Superconducting Y‐Ba‐Cu‐O oxide films by sputtering

Abstract: We have prepared superconducting thin films of Y‐Ba‐Cu‐O with Tc onsets above 95 K by both diode and magnetron sputtering. Films with full superconductivity (R=0) at 85 K have been produced by dc magnetron sputtering. The compositions of the films are fairly uniform across an area 50 mm in diameter and through the film thickness. Structural properties of the films were studied by x‐ray diffraction. Critical current densities in the range of 3000 to 104 A/cm2 have been measured at 4.2 K.

Characterization of reactively sputtered ruthenium dioxide for very large scale integrated metallization

Abstract: We have investigated reactively sputtered films of RuO2 for possible application in very large scale integrated circuits. Sputtering yields stoichiometric ruthenium dioxide in a large window of oxygen pressures and the films are reasonably low stressed in the 10−9 dyn cm−2 range. The resistivity of as deposited films is 40 μΩ cm. The films are excellent barriers against interdiffusion of Si and Al.

Structural and electrical properties of rf-sputtered amorphous barium titanate thin films

Abstract: Structural and electrical properties of rf‐sputtered amorphous BaTiO3 thin films grown on water‐cooled substrates have been investigated. The dielectric and electrical properties have been studied for films grown under varying sputtering gas composition (Ar+O2 gas mixtures) as a function of film thickness, frequency, and temperature. As‐grown films were amorphous in nature and highly transparent. Post‐deposition annealing had no discernible effect either on film structure or dielectric properties, and there was no evidence of ferroelectricity. Films sputtered in pure argon showed a dielectric constant e’∼12 with little dependence on frequency (0.1–100 kHz) over the temperature range 0–75 °C. The dielectric properties were a function of film thickness and the percentage of oxygen in the sputtering gas during growth. The thickness‐dependent dielectric properties of amorphous BaTiO3 thin films on conducting glass substrates could be satisfactorily explained by a model based on the existence of electrode barriers. The high breakdown voltage (106 V/cm), charge storage capacity (3.1 μC/cm2), and frequency‐ and temperature‐dependent dielectric properties of a‐BaTiO3 films sputtered in pure argon show promise for application as insulating layers in thin‐film electroluminescent display devices.

Methods of forming synthetic diamond coatings on particles using microwaves

Abstract: An apparatus and method for applying hard surface coatings to articles of manufacture such as particles, filaments, sphereoids, rollers, bearings, tools, and assemblies. In one form, coating of hard surface film, such as synthetic diamond, is effected while the objects fall freely through space in a coating chamber. In another form, coating is effected while particles are fluidized by gas containing molecules which are formed of matter to be deposited by gas or chemical vapor deposition employing high energy radiation, such as microwave energy and/or other form of radiation. In other forms, an ion beam or beams containing hot carbon ions is directed through a fluidized bed of particles to be coated or through a chamber in which small objects are made to continuously fall freely through space to coat same with carbon in the form of synthetic diamond. In another method, such small objects are caused to continuously tumble through a coating region of a coating chamber into which is directed gas and/or vapor containing molecules of a hydrocarbon, such as methane, and hydrogen, while microwave energy is directed through such region. Other forms of the invention include the selective deposition and coating of synthetic diamond onto substrates to form or protect microminiature electronic circuits and circuit elements such as transistors and interconnects and to protect bonds such as welds, or to form bonds between components joined together thereby. In yet another form, hard synthetic diamond coatings are deposited per se or in combination with other materials, by a hybrid process including chemical vapor deposition, ion deposition by beam(s), sputtering and the like.

Low‐temperature process for the preparation of high Tc superconducting thin films

Abstract: We have established the low‐temperature process for the preparation of high Tc superconducting films by rf magnetron sputtering. The films were deposited at a temperature (650 °C) lower than the tetragonal‐orthorhombic transition point with sufficient crystallizing and oxidizing conditions. The as‐deposited Er‐Ba‐Cu‐O film on MgO exhibited a sharp superconductive transition with zero resistance at 86 K. This process prevented diffusion at the film and substrate interface and reduced the porous structure in the films.

Acoustic investigation of the elastic properties of ZnO films

Abstract: The elastic properties of ZnO films deposited by rf magnetron sputtering on Al2O3 substrates have been analyzed by means of an acoustic investigation technique. The phase velocities of a spectrum of acoustic modes propagating along the layered structure have been measured and the results exploited for determining the complete set of elastic constants of the film. The effective constants of the film are lower than those of the bulk material by amounts which depend on the elastic constant considered and range from −1.2% for c33 to −24.8% for c11. The values obtained were used for determining the dispersion curves of acoustic modes propagating along ZnO layers deposited on fused quartz and silicon and showed good agreement with experimental results.

A gas-flow model for the sputtering of condensed gases

Abstract: The bombardment of condensed gases by low keV ions or atoms establishes a collision cascade in the solid. We argue that in cases where the deposited energy density surpasses the critical temperature of the medium, the gas formed expands into the vacuum, increasing the sputtering yield and shifting the energy spectrum to lower energies. A simple model, based on the assumption of a collision-free molecular flow, is developed to give analytical results for the sputtering yield and the axial energy spectrum. The effects of the expansion process, of energy dissipation and of recondensation on the crater walls are discussed. Good agreement with experimental sputtering yields and energy spectra is found.

Reactive magnetron sputtering of thin‐film superconductor YBa2Cu3O7−x

Abstract: Superconducting thin films of YBa2Cu3O7−x have been successfully made by co‐sputtering from the three targets in an Ar and O2 mixture atmosphere. After high‐temperature anneal films are superconducting with an onset temperature at 90 K, a full transition temperature as high as 88 K, and a critical current density in excess of 1×105 A/cm2 at 78 K and 2×106 A/cm2 at 4.2 K. Highly oriented thin films have been obtained on SrTiO3 {100} substrates.

Reactive d.c. high-rate sputtering as production technology

Abstract: We discuss process parameters that influence the deposition of layers with dedicated stoichiometry in terms of the fundamentals of reactive d.c. sputter processes with magnetron sources. We introduce the term “basic stability” of reactive sputter arrangements and describe their variants. To make the industrial production of films from chemical compounds profitable, however, it is necessary to work in the unstable transition mode. We discuss methods for process stabilization and present new approaches by using a plasma-emission monitor (PEM) and a self-stabilizing arrangement for the long-term deposition of insulating films. When working with the PEM control loop, the reactive d.c. sputter process can be stabilized even at close coupling between target and substrate. To exemplify various production techniques with different requirements, we compare indium-tin oxide (ITO), Cr-Si-O and TiN layers. The PEM control allows the deposition of ITO layers at a defined degree of oxidation to obtain minimum resistivities of ϱ

Sputter-Deposition of [111]-Axis Oriented Rhombohedral PZT Films and Their Dielectric, Ferroelectric and Pyroelectric Properties

Abstract: [111]-oriented PZT films have been successfully grown with good epitaxy onto epitaxial platinum film substrates by the rf-magnetron sputtering method using Pb enriched PZT(90/10) targets. The sputtering conditions for growing epitaxial films were investigated. Crystallographic identifications of the films were made by the X-ray and RHEED measurements. Dielectric, ferroelectric and pyroelectric properties of these films were measured. Pyroelectric coefficients at room temperature were determined as 45 and 3×10-9 C/cm2 K for epitaxial PZT films with poling and without poling treatments, respectively. Epitaxial PZT films sputtered on Pt/sapphire possess desirable properties for potential applications to pyroelectric devices.

Preparation of Co-N films by rf-sputtering

Abstract: Co-N films in the wide compositional range can be prepared by reactive sputtering. Co-N sputtered films consist of one or two phases, such as CoN, Co2N, Co3N, Co4N and α-Co. Co4N phase with a cubic unit cell is observed, and its lattice constant isa = 0.3586 nm. The preferred orientation is observed on the Co-N films, CoN (200) plane, Co4N (1 1 1) plane and α-Co (002) plane parallel to the film surface, respectively. Saturation magnetization σs of Co-N sputtered film decreases from 160 to 1.7 e.m.u. g−1 with increasing content of N from 0 to 21.7 at%, and coercive forceI H c is the range of 43 to 5000e at room temperature.

Method and apparatus for sputtering a dielectric target or for reactive sputtering

Abstract: A device and method for sputtering dielectric targets, for reactive sputtering, and for sputter etching, including a target, anode and auxiliary electrode where each of the foregoing elements is electrically isolated from a grounded chamber containing a plasma and during a sputtering cycle, the anode and target are connected across a first floating power supply which applies a first series of waveforms to the target to render the target positive with respect to the plasma and thus sputter it and during a charge removal cycle, the auxiliary electrode and target are connected across a second floating power supply which applies to the target a second series of waveforms during respective intervals between the first series of waveforms to render the target negative with respect to the plasma and thus remove any positive charge build up which may have occurred during the sputtering cycle.

Low‐energy ion irradiation during film growth for reducing defect densities in epitaxial TiN(100) films deposited by reactive‐magnetron sputtering

Abstract: Transmission electron microscopy has been used to study the defect structure in epitaxial TiN(100) films as a function of the growth temperature (Ts=550–850 °C) and negative substrate bias (Vs=0–500 V) applied during reactive‐magnetron sputter deposition onto cleaved MgO substrates. For the growth conditions used in these experiments, the energy per incident N ion (N+2 was the predominant ionic species) was ∼Vs/2 and the incident ion to thermal‐atom flux ratio was ∼2. The results showed that the primary defects were dislocation loops whose number density nd decreased with increasing Ts for a given Vs. However, nd decreased much more rapidly with increasing Vs at constant Ts until a minimum defect density was attained at Vs=V*s after which nd increased with further increases in Vs. Low‐energy ion irradiation during film growth played at least two primary roles: it resulted in the creation of additional point defects which then condensed into dislocation loops and it enhanced atomic mobilities thereby accel...

Nucleation of body-centered-cubic tantalum films with a thin niobium underlayer

Abstract: We discuss the structural and electrical properties of high‐quality Ta films prepared by ion beam sputter deposition. The Ta films grow in two different crystal structures, body‐centered‐cubic (bcc) or tetragonal (β‐Ta), depending on the substrate preparation and sputtering conditions. Ta films deposited on a thin (>0.3 nm) Nb underlayer grow in the bcc crystal structure with properties approaching those of clean bulk polycrystalline material. The bcc‐Ta films have a superconducting transition temperature of 4.3 K and a low‐temperature (10 K) resistivity ρ∼6 μΩ cm. Ta films deposited without a Nb underlayer on Si substrates always grow in the tetragonal (β‐Ta) structure. The β‐Ta films do not superconduct above 1 K and have a high resistivity ρ∼150 μΩ cm. X‐ray diffraction and transmission electron microscope studies of both Ta structures are presented. Both bcc‐Ta and β‐Ta films are deposited on room‐temperature substrates. This allows either type of film to be easily patterned by standard photoresist liftoff methods.

Degradation of tin‐doped indium‐oxide film in hydrogen and argon plasma

Abstract: The degradation of tin‐doped indium‐oxide (ITO) films in glow‐discharge plasmas of hydrogen and argon have been investigated. Parameters which have been varied for the study include the temperature of ITO under ion bombardment, the rf power density, the time of exposure to plasma, and the gas flow rate. After bombardment, scanning electron micrograph observation, measurement of sheet resistance, transmittance and reflectance, and Auger analysis have been carried out to decide the extent of degradation. Magnetron‐sputtered ITO films have been found to be more resistant to ion bombardment damage compared to electron‐beam evaporated films. The degradation of ITO under the plasma of the reducing species such as hydrogen has been found to take place at lower temperature and power density compared to argon plasma.