Showing papers on "Sputtering published in 1969"

Theory of Sputtering. I. Sputtering Yield of Amorphous and Polycrystalline Targets

Abstract: Sputtering of a target by energetic ions or recoil atoms is assumed to result from cascades of atomic collisions. The sputtering yield is calculated under the assumption of random slowing down in an infinite medium. An integrodifferential equation for the yield is developed from the general Boltzmann transport equation. Input quantities are the cross sections for ion-target and target-target collisions, and atomic binding energies. Solutions of the integral equation are given that are asymptotically exact in the limit of high ion energy as compared to atomic binding energies. Two main stages of the collision cascade have to be distinguished: first, the slowing down of the primary ion and all recoiling atoms that have comparable energies---these particles determine the spatial extent of the cascade; second, the creation and slowing down of low-energy recoils that constitute the major part of all atoms set in motion. The separation between the two stages is essentially complete in the limit of high ion energy, as far as the calculation of the sputtering yield is concerned. High-energy collisions are characterized by Thomas-Fermi-type cross sections, while a Born-Mayer-type cross section is applied in the low-energy region. Electronic stopping is included when necessary. The separation of the cascade into two distinct stages has the consequence that two characteristic depths are important for the qualitative understanding of the sputtering process. First, the scattering events that eventually lead to sputtering take place within a certain layer near the surface, the thickness of which depends on ion mass and energy and on ion-target geometry. In the elastic collision region, this thickness is a sizable fraction of the ion range. Second, the majority of sputtered particles originate from a very thin surface layer (\ensuremath{\sim}5 \AA{}), because small energies dominate. The general sputtering-yield formula is applied to specific situations that are of interest for comparison with experiment. These include backsputtering of thick targets by ion beams at perpendicular and oblique incidence and ion energies above \ensuremath{\sim}100 eV, transmission sputtering of thin foils, sputtering by recoil atoms from $\ensuremath{\alpha}$-active atoms distributed homogeneously or inhomogeneously in a thick target, sputtering of fissionable specimens by fission fragments, and sputtering of specimens that are irradiated in the core of a reactor or bombarded with a neutron beam. There is good agreement with experimental results on polycrystalline targets within the estimated accuracy of the data and the input parameters entering the theory. There is no need for adjustable parameters in the usual sense, but specific experimental setups are discussed that allow independent checks or accurate determination of some input quantities.

Microtopography of Surfaces Eroded by Ion-Bombardment

Abstract: Conical protrusions have been observed in the scanning electron microscope on surfaces that have been eroded by sputtering under 5 to 8 keV A+ ion bombardment. It is shown why these have a half-angle corresponding to the principal peak in the graph of sputtering rate versus angle of ion incidence. These lead to some general conclusions on the microtopography ofion-eroded surfaces.

The equilibrium topography of sputtered amorphous solids

Abstract: A theory is developed for the sputtering of amorphous solid by an ion beam and the changes in surface topography to which this sputtering leads. It is shown that surfaces which have pinning regions, such as vertical steps and included impurities, reach an equilibrium in which cones are developed on the surface. The theory is compared with several experimental observations of such conical development.

Magnetic oxide films

Abstract: Polycrystalline and epitaxial magnetic oxide films have been fabricated by several investigators. This paper deals predominantly with epitaxial films grown by chemical vapor deposition. The majority of the discussion is concerned with substrates, the deposition process, and film characterization. Where possible, comparisons are made with bulk crystals and with films produced by other fabrication techniques.

Ion bombardment and implantation

Abstract: The scope and importance of ion bombardment studies has in recent years been considerably extended by the realization that the surface properties of materials, and in particular the semiconductors, may be usefully modified by means of the implantation of suitable ions in the form of an accelerated beam. Whereas earlier studies of radiation damage and sputtering were confined mostly to low ion energies, interest has now grown in the behaviour at higher energies, up to the Mev region. Often the bombarded specimens are crystalline, and the so-called channelling phenomenon is important in determining the range distribution of implanted material and the degree of lattice disruption created. After a summary of the various commonly used approximations to the interatomic potential, the energy loss mechanisms of ions in solids are discussed and experimental results are compared with theoretical predictions for both the amorphous and crystalline cases. In the next section, attention is focused upon the radiation damage produced by ion bombardment of crystalline targets, and the migration and clustering of radiation-induced defects is discussed. The sputtering process is described and recent work is summarized. In this, and the following section on secondary electron emission, the behaviour of single-crystal targets has proved important in understanding the physical nature of the process. Modern developments in ultra-high vacuum technology have aided both these studies. A lengthy account is given, in the final section, of the physical processes involved in ion implantation. The advantages of this method of doping semiconductor crystals are discussed, as well as some attendant problems. Examples of the practical application which has already been made are given, and the equipment required for such work is described. A certain degree of speculation is hazarded regarding the future prospects of the ion-implantation technique in research and industrial applications.

Sputtering Yield Measurements with Low‐Energy Metal Ion Beams

Abstract: Sputtering yields of metal ion beams on polycrystalline films for energies below 1 keV were measured in situ using crystal microbalance techniques. Self‐sputtering yields were determined for Au, Cu, Ag, Cr, and Al for energies from 10 to 500 eV. These yields were consistent with some previous noble‐gas sputtering yields when only the difference in ionic mass was taken into account. Residual oxygen significantly lowered the self‐sputtering yields of Al and Cr for all energies from 0 to 1 keV and the collection rate of oxygen was apparently greater for ions of about 10 eV. Sputtering yields of films by dissimilar metal ions were most strongly influenced by the type of metal in the beam, rather than by the target material, even for high ion energies.

Dielectric Properties of Reactively Sputtered Films of Aluminum Nitride

Abstract: Resistivity, capacitance and dielectric loss measurements for diode reactive sputtering grown AlN films and film sandwich structures of Ta, Au and Al films

The formation of precipitate phases in aluminium by ion implantation

Abstract: The formation of precipitates of second phases during the ion implantation of thin metallic films is discussed in general terms. Observations from an electron microscope investigation of precipitation behaviour during the implantation of aluminium specimens with 70-80 kev Cu+, Sb+ and Pb+ ions are described in detail. Special reference is made to the effects of radiation-enhanced diffusion and surface sputtering on precipitate growth and distribution, and to the morphology and orientation relationships of the precipitates concerned, which include CuAl2 and AlSb, and Pb in both solid and liquid states.

RF sputtered strontium titanate films

Abstract: Two deposition parameters are important in rf sputtering of SrTiO3 films: the oxygen-argon content ratio, and the substrate temperature. More than 1% oxygen is needed to produce insulating films; the exact percentage required depends on system cleanliness. Both dielectric ccnstant and crystallite size increase with increasing substrate temperature. Films of 2400 A deposited at 500°C on gold have a dielectric constant of 200. The dc conductivity closely follows the Poole-Frenkel model. Two dielectric loss peaks are believed to be caused in part by an oxygen deficient region near one electrode. The variation in the dielectric constant K with electric field is similar to that observed in bulk material.

Crystallographic Orientation of Zinc Oxide Films Deposited by Triode Sputtering

Abstract: Zinc oxide films for thin film piezoelectric transducer applications have been deposited by triode sputtering onto gold film surfaces. Films sputtered under relatively hydrocarbon-free conditions showed the “normal” orientation with the c axis perpendicular to the substrate surface. The addition of hydrocarbon vapors to the sputtering gas at the beginning of the deposition resulted in films at least partly oriented with the c-axis parallel to the substrate surface, and the simultaneous application of a reverse bias to the substrate holder produced films essentially completely oriented with this parallel orientation. Under oblique deposition conditions the average c axis direction in the film plane was directed towards the target, yielding good piezoelectric shear mode transducers with a uniform polarization. It is suggested that the hydrocarbon vapors polymerize in the discharge, covering the substrate with an organic film on which zinc oxide grows with the parallel orientation, and that alignment of the ...

Electrical and Optical Properties of Sputtered CdO Films

Abstract: CdO films were prepared by a D–C reactive sputtering method with various sputtering voltages. The characters of the prepared films are compared with the reflection electron diffraction and X-ray diffraction patterns. Especially, the effects of the sputtering voltage and partial pressure of oxygen were investigated concerning the electron densities and the Hall mobilities. The observations on lattice parameters lead to the conclusion that CdO films with high carrier concentrations contain some amount of interstitial excess Cd atoms. The absorption edge variation of annealed films prepared by high voltage sputtering agrees with the theoretical curve which is accounted from the Fermi level shift caused by the change in carrier concentrations.

Deposition of MoS sub 2 films by physical sputtering and their lubrication properties in vacuum.

Abstract: Physical sputtering deposition of molybdenum disulfide films as solid lubricant on rotating and sliding components, discussing lubrication properties in vacuum

Low Pressure Sputtering System of the Magnetron Type

Abstract: A new design of a low pressure sputtering system of magnetron type is described. The optimum sputtering conditions are discussed in relation to the system. It is shown that this system is able to produce uniform thin films with good reproducibility, and especially to produce a metal oxide film by reactive sputtering. Some typical configurations are presented for use in the laboratory and on a production scale.

Proposed Model for the Composition of Sputtered Multicomponent Thin Films

Abstract: A simple model is proposed which predicts the composition of sputtered multicomponent thin films. The model is applied to such problems as alloy sputtering, gas incorporation into thin films, and compound formation. Several practical systems are considered such as the sputtering of Gd3Fe5 and Ni4Fe alloys and the incorporation of argon, oxygen, and nitrogen into tungsten films. The results of these studies suggest that the film composition is a strong function of vapor pressure, sputtering rate, atomic size, system geometry, sticking probabilities, and sputtering coefficients.

Thermal Oxidation of Sputtered Tantalum Thin Films between 100° and 525°C

Abstract: Results are presented for the thermal oxidation behavior of four types of sputtered tantalum films between 100° and 525°C. These films are bcc tantalum, β‐tantalum, a porous β‐tantalum, and tantalum nitride (Ta2N). All four types of films show parabolic oxidation kinetics and the formation of adherent Ta2O5 (tantalum oxy‐nitride for Ta2N films) with bright interference colors. The first three types of films dissolve about 12 at.% oxygen, which is much higher than the oxygen solubility found in bulk tantalum, and the films show a different degree of suboxide formation than bulk tantalum. The activation energies for oxygen diffusion in the metal and for oxide growth are 1.2 and 1.4 eV, respectively. The dielectric properties of the thermal oxide are discussed in terms of the defects in the oxide.

Cation deficiencies in RF sputtered gadolinium iron garnet films

Abstract: RF sputtering of stoichiometric, polycrystalline gadolinium iron garnet material resulitns films significantly deficient in iron content. The cation deficiency is shown to be quite sensitiov ep reparatory conditions and reflects itself markedly in the magnetic and structural properties of the resultant films. Temperature dependent sticking probabilities and selective resputterig at the growing film surface are thought to be the most likely causes for the observed deficiencies. A simultaneously operated rf-dc two-target sputtering system is described in some detail, which allows an expeditious study of and subsequent compensation for the observedcation deficiency. Films with essentially the bulk garnet composition and bulk structural and magnetic properties were prepared in this two target system.

Temperature Dependence of the Ag/Cu Sputtering Ratio for the Eutectic

Abstract: The relative sputtering rates of Ag and Cu from the Ag/Cu eutectic (60% Ag‐40% Cu by atoms) were measured by means of the spectroscopic emission technique. The targets were bombarded by 100‐eV Ar ions for target temperatures in the range of 80° to 285°C. At low target temperatures, the Ag and Cu sputtering yields vary with time of sputtering according to a simple sputtering model. However, at the higher temperatures surprisingly large differences were observed which could not be explained by a simple model. For example, Ag/Cu sputtering ratio variations greater than a factor of 10 were observed. After prolonged sputtering in the high‐temperature range, a thick surface layer (∼1 μ) developed which was highly enriched in Cu. A model based on surface diffusion of Ag on Cu is proposed to explain the results.

Direct collection of some metal ions in an electromagnetic isotope separator and related surface effects.

Abstract: The direct collection of Fe, Co, Ni, Cu, Zn, and Sn ions has been investigated in the energy range from about 10 eV to 110 keV in an electromagnetic isotope separator. At low energies the ions build up a layer on the surface of the graphite block used as a backing, while at high energies only a certain saturation value can be collected. For these ions the highest energies at which the building-up of a layer was observed were 1.5 keV, 1.0 keV, 0.8 keV, 0.3 keV, 0.3 keV, and 0.45 keV, respectively. In the building-up region the efficiency of the collection process and the sticking probability of ions as a function of energy have been measured. From these the self-sputtering ratios have been calculated. In the saturation region the amounts of material collected have been measured and the ranges of ions in graphite backings saturated with metal atoms have been calculated theoretically. This calculation gives an estimate of the metal atom concentrations in the graphite, which in turn determines the sputtering ...

Epitaxial Thin Films of ZnO on CdS and Sapphire

Abstract: The technique for obtaining polycrystalline thin films of ZnO by sputtering of the compound has been perfected so that epitaxial films can be obtained on sapphire and CdS Dependence of the crystalline perfection of the films on substrate temperature, deposition rate, and substrate polish has been studied in detail Substrate temperatures from 100 ° to 500 °C and deposition rates from 1 to 100 A/min were studied Film structure was evaluated by x-ray diffraction and reflection electron diffraction Electrical and optical measurements were made to determine the resistivity, Hall mobility, optical absorption edge, and refractive index of films It was found that these properties of the films were very similar to bulk crystal data except for the Hall mobility which was lower by almost two orders of magnitude The poor mobility is attributed to scattering by defects introduced during the high-energy sputtering process

Distribution of Material Sputtered from a Disk Electrode

Abstract: Using the Davidse-Maissel diode sputtering system, the distribution of material deposited in the substrate plane during sputtering is studied as a function of power, sputtering pressure, target-to-collector spacing and electrode shielding. Both rf and dc sputtering are investigated. The target is a cobalt disk surrounded by concentric rings of nickel, iron, and copper; the concentration of each component in the deposit (collected on glass slides) is determined through x-ray fluorescence analysis. A mathematical relationship between the local deposition rate on the substrate and the emission from the source is derived. The proposed model describes the observed distribution as arising from the superposition of two sources: (1) a uniform disk, and (2) a ring of infinitesimal width at the perimeter (both sources emitting with a cosine distribution). The latter phenomenon is due to the fact that the dark space of the glow discharge can wrap around the edge of the electrode.

High‐Coercive‐Force Rare‐Earth Alloy Films by Getter Sputtering

Abstract: Thin films of the rare‐earth alloys of the Co–Sm system with and without the addition of Cu have been found to have exceptionally high coercive forces. A coercive force of 30 000 Oe was realized with Co3.65Cu1.35Sm films, 4000‐A thick prepared at a substrate temperature of 500°C using getter sputtering. This technique avoids troublesome oxidation problems usually encountered in preparing films of active materials such as the rare‐earth compounds.

Thin-Film Josephson Junctions Using Getter-Sputtered Niobium

Abstract: Thin‐film niobium‐niobium oxide‐lead Josephson junctions were fabricated by use of getter sputtering for the Nb films, thermal oxidation of the Nb and evaporation of the Pb top films These devices have characteristics comparable to good Pb–PbO–Pb devices Temperature cycling is not harmful to the devices although some drift with time is seen in the characteristics This drift is in the form of a conductance increase which has been measured as something between a factor of 11 to a factor of 20 over a period of months with the devices stored at room temperature

High Field Properties of Pure Niobium Nitride Thin Films

Abstract: NbN thin film production by refined reactive sputtering technique, discussing Pauli spin paramagnetism and spin orbit scattering in high field superconductivity

Some Magnetic and Structural Properties of Epitaxial Garnet Films Prepared by rf Sputtering

Abstract: Epitaxial garnet films have been prepared by rf sputtering from a polycrystalline gadolinium iron garnet target onto single‐crystal substrates of YAG. Epitaxy is achieved on all orientations of the substrate, either in situ when depositing at ≥500°C, or during post‐deposition crystallization of amorphous or partially crystallized films deposited at <500°C. The compensation temperature in epitaxial films depends strongly on the deposition temperature. The lowest compensation temperatures are found in films prepared at the highest deposition temperatures. Flims prepared on glass substrates at elevated deposition temperatures are iron deficient and crystallize in at least two phases, Gd3Fe5O12 and GdFeO3. The iron deficiency in these films is assumed to be caused by a variation with temperature in the net cation sticking coefficients. No GdFeO3 phase is found in epitaxial films prepared at the same elevated deposition temperatures, although these films should also be iron deficient. It is believed that they ...

Structural, Optical, and Dielectric Properties of Reactively Sputtered Films in the System AlN–BN

Abstract: Previous studies by the authors have shown that oriented, crystalline films of AlN prepared by reactive sputtering in an ultrahigh-vacuum system (residual pressure <10−9 Torr) display dielectric properties comparable, and often superior, to those of ceramic AlN. The present work examines the optical absorption of such AlN films in the region of the absorption edge and extends the investigation to include reactively sputtered films of BN and AlN–BN mixtures. The absorption edge of AlN films, sputtered in high pressures of Ar, shows an anomalous shift of about 2.5 eV to lower energies that can be removed by annealing in N2; similar, but smaller, shifts occur in bulk, single-crystal AlN. Films of BN display corresponding shifts of about 0.5 eV and yield diffraction patterns consistent with the bulk hexagonal polymorph but with slightly altered lattice parameters. The structural and optical absorption data for mixed AlN–BN films are consistent with a small degree of solubility of BN in AlN.