Showing papers on "Sputtering published in 1996"

Ion-Solid Interactions: Fundamentals and Applications

Abstract: 1. General features and fundamental concepts 2. Interatomic potentials 3. Dynamics of binary elastic collisions 4. Cross-section 5. Ion stopping 6. Ion range and range distribution 7. Radiation damage and spikes 8. Ion-solid simulations and irradiation enhanced transport 9. Sputtering 10. Order-disorder under irradiation and ion implantation metallurgy 11. Ion beam mixing 12. Phase transformations 13. Ion beam assisted deposition 14. Applications of ion beam processing techniques 15. Ion beam system features Appendices: A. Crystallography B. Table of contents C. Density of states D. Derivation of the Thomas-Fermi differential equations E. Centre-of-mass and laboratory scattering angles F. Miedema's semi-empirical model for the enthalpy of formation in the liquid and solid state G. Implantation metallurgy - study of equilibrium alloys.

Work function of indium tin oxide transparent conductor measured by photoelectron spectroscopy

Abstract: We used ultraviolet and x‐ray photoelectron spectroscopy (XPS) and (UPS) techniques to directly measure absolute values of vacuum work function of indium tin oxide (ITO) thin films. We obtained a work function of 4.4–4.5 eV which is lower than the commonly cited value. These values do not change substantially by heating and Ar ion sputtering. The atomic concentrations of each element in ITO, measured with XPS, are also quite stable under heat treatment and ion sputtering.

Postdeposition annealing of radio frequency magnetron sputtered ZnO films

Abstract: Zinc oxide (ZnO) films have been deposited on 1 μm SiO2/Si (100) substrates by rf magnetron sputtering. Using a sputtering gas of pure oxygen, a pressure regime is found in which the ZnO films grow on room temperature substrates with a single (0001) orientation, small grains (crystallite sizes ∼10–15 nm), and high intrinsic biaxial compressive stress (∼6 GPa). The effects of post‐deposition annealing these films in air was investigated over a range of temperatures (200–1000 °C) and durations (2–2000 min). Annealing resulted in lower biaxial compressive stresses and increased average crystallite sizes in all films. Additional ZnO grain orientations were detected only after annealing above 500 °C for longer than 90 min, and the results are interpreted in terms of film recrystallization. Consequently, a relatively rapid thermal anneal at 1000 °C for 5 min caused grain recovery without recrystallization, resulting in maximum stress reduction (90%–100% of stress was relieved and average crystallized size tripl...

Study of oxygen chemisorption on the GaN(0001)‐(1×1) surface

Abstract: Clean, ordered GaN(0001)‐(1×1) surfaces are prepared by sputtering with nitrogen ions followed by annealing in ultrahigh vacuum. The surfaces are subsequently exposed at room temperature to O2 and the chemisorption process studied using Auger, valence and core‐level photoemission and electron energy loss spectroscopies, low‐energy electron diffraction, and work function measurements. Saturation occurs at a coverage of Θox=0.4 ML and is accompanied by the removal of surface states near the band edges. The continued presence of a clear (1×1) diffraction pattern, together with other data, indicates a well‐defined adsorption site, but the relative importance of Ga–O and N–O bonding remains undetermined. The realization that surface states exist near the valence‐band maximum has led to a more accurate determination of the surface Fermi‐level pinning position, and of dependent quantities, than given previously. Clean‐surface data are also compared with those for surfaces prepared by in situ deposition of Ga metal followed by thermal desorption. No significant differences are seen, which suggests that nitrogen‐ion sputtering and annealing is suitable for preparing clean, ordered GaN(0001)‐(1×1) surfaces. The results for O chemisorption on atomically clean surfaces have been applied to evaluating the passivation of surfaces prepared by ex situ wet‐chemical cleaning. The band bending is found to be ∼0.5 eV less than on atomically clean surfaces.

Symmetric tunable inductively coupled HDP-CVD reactor

Abstract: The present invention provides an HDP-CVD tool using simultaneous deposition and sputtering of doped and undoped silicon dioxide capable of excellent gap fill and blanket film deposition on wafers having sub 0.5 micron feature sizes having aspect ratios higher than 1.2:1. The system of the present invention includes: a dual RF zone inductively coupled plasma source configuration capable of producing radially tunable ion currents across the wafer; a dual zone gas distribution system to provide uniform deposition properties across the wafer surface; temperature controlled surfaces to improve film adhesion and to control extraneous particle generation; a symmetrically shaped turbomolecular pumped chamber body to eliminate gas flow or plasma ground azimuthal asymmetries; a dual helium cooling zone electrostatic chuck to provide and maintain uniform wafer temperature during processing; an all ceramic/aluminum alloy chamber construction to eliminate chamber consumables; and a remote fluorine based plasma chamber cleaning system for high chamber cleaning rate without chuck cover plates.

Comparative study of tantalum and tantalum nitrides (Ta2N and TaN) as a diffusion barrier for Cu metallization

Abstract: Tantalum (Ta) and tantalum nitride films (Ta2N and TaN) of about 50 nm thickness were reactively sputter deposited onto (100) Si substrate by using dc magnetron sputtering and their diffusion barrier properties in between Cu and Si were investigated by using sheet resistance measurement, x‐ray diffraction, Auger electron spectroscopy, and Secco etching. With increasing amounts of nitrogen in the sputtering gas, the phases in the as‐deposited film have been identified as a mixture of β‐Ta and bcc‐Ta, bcc‐Ta, amorphous Ta2N, and crystalline fcc‐TaN. Diffusion barrier tests indicate that there are two competing mechanisms for the barrier failure; one is the migration of Cu into the Si substrate and another is the interfacial reaction between the barrier layer and the Si substrate. For instance, we identified that elemental Ta barrier failure occurs initially by the diffusion of Cu into the Si substrate through the barrier layer at 500 °C. On the other hand, the Ta2N barrier fails at 700 °C by the interfacial reaction between Ta2N and Si substrate instead of the migration of Cu into the Si substrate. For the case of TaN, the barrier failure occurs by the migration of Cu into the Si substrate at 750 °C. It is also demonstrated that the diffusion barrier property is enhanced as the nitrogen concentration in the film is increased.

New Routes in the Preparation of Mechanically Hard Films

Abstract: Superhard nitride superlattice coatings with nanometer-scale multilayers have hardnesses exceeding 50 gigapascals, making these films highly resistant to abrasion. The nitride superlattice films can be deposited economically by reactive sputtering in production-size equipment on a variety of substrates. A model for the superlattice strength enhancement has been developed that accurately predicts which materials can be used together to produce the enhanced hardness. Advancements in sputtering technology-specifically, pulsed dc power and reactive-gas partial-pressure control-make it possible to reactively deposit nonconducting oxide films at high deposition rates. This technology is being used along with the superlattice strength model in the development of oxide superlattice films.

Optical nonlinearities of Au/SiO2 composite thin films prepared by a sputtering method

Abstract: Third‐order nonlinear optical properties of Au/SiO2 composite thin films have been investigated by means of a degenerate four‐wave mixing at room temperature. In the optical‐absorption spectra the absorption peak due to the surface plasmon resonance of Au particles is observed at the wavelength around 530 nm. With increasing the mean diameter of Au particles, the absorption at the peak is increased and the full width at half‐maximum of the absorption band is decreased from 130 to 80 nm. The third‐order nonlinear susceptibility χ(3) exhibits a peak at the wavelength of the absorption peak and the maximum value of χ(3) is obtained to be 2.0×10−7 esu. The size‐dependent enhancement of the χ(3) in Au particles with the mean diameter of 3.0–33.7 nm has been also investigated. The value of χ(3)/α (α: absorption coefficient) for the films is increased upon an increase of mean diameter of Au particles. This is explained by the size dependences of the local‐field factor and the imaginary part of dielectric constant of the metal particles.

High‐frequency magnetic properties in metal–nonmetal granular films (invited)

Abstract: The structure and properties of Co–N and Co–O based films, prepared by rf magnetron reactive sputtering using nitrogen or oxygen and argon gases, have been studied. Transmission electron microscopy (TEM) observation reveals that each Co–(Al or Si)–(N or O) film is a typical film with granular structure, with grain size less than 5 nm. It is found by micro‐focused energy‐dispersive x‐ray and electron energy loss spectroscopy analysis that the grains are mainly composed of Co and the intergranular regions are ceramics of N or O. In Co–N based films, soft magnetic properties are found in both Si and Al containing films over a wide range of film preparation conditions and compositions. Only the films with Al show soft magnetic properties in Co–O based films, which have ρ of 500–1000 μΩ cm, Hk of about 80 Oe and Bs of about 10 kG. By adding about 10 at. % Pd, the soft magnetic properties and Hk of Co–O based films are significantly improved, with Hk more than 180 Oe. These films exhibit a remarkable constant f...

Structural and mechanical properties of carbon nitride CNx (0.2⩽x⩽0.35) films

Abstract: This article reports on the structure and mechanical properties of CNx thin films deposited by unbalanced reactive magnetron sputtering of C in N2 discharges. The films were grown on Si(001) substrates kept at temperatures (Ts) between 150 and 600 °C. Depending on Ts, the films contained between 15 and 26 at. % N. X‐ray photoelectron spectroscopy of samples typically showed two peaks in the C 1s core level spectrum (centered at 284.5 and 286.2 eV) and two peaks in the N 1s core level spectrum (centered at 398.4 and 400.3 eV). This indicates that there are two types of C–N bonds where N is bonded to both sp2‐ and sp3‐coordinated C atoms in the as‐deposited films. Transmission electron microscopy showed that the films produced in the temperature range 200≤Ts≤600 °C had a highly textured, turbostraticlike structure with the c axis in the plane of the film. The basal planes in this structure were found to be buckled and bent due to incorporation of N in substitutional sites. By contrast, films produced at Ts=...

Tetrahedral amorphous carbon films prepared by magnetron sputtering and dc ion plating

Abstract: Highly tetrahedral, dense amorphous carbon (ta‐C) films have been deposited using rf sputtering of graphite by an unbalanced magnetron with intense dc Ar‐ion plating at low temperatures (<70 °C). The ratio of the argon ion flux to neutral carbon flux Φi/Φn is about 5. The film density and compressive stress are found to pass through a maximum of 2.7 g/cm3 and 16 GPa, respectively, at an ion plating energy of about 100 eV. Experiments with higher ion flux ratios of Φi/Φn=10 show that it is possible to deposit carbon films with densities up to 3.1 g/cm3 and sp3 contents up to 87%. Deposition of ta‐C in this experiment when the energetic species is Ar appears to require a minimum stress of 14 GPa to create significant sp3 bonding, which contrasts with the continuous increase in sp3 content with stress when the energetic species is C ions themselves. These results are used to discuss possible deposition mechanisms.

Copper nitride and tin nitride thin films for write‐once optical recording media

Abstract: The feasibility of using copper nitride and tin nitride thin films as write‐once optical recording media was explored. The Cu3N and SnNx films were obtained by the reactive sputtering method. They were thermally decomposed into Cu and Sn films at 470 and 550 °C, respectively. The Cu film obtained by the thermal decomposition showed a large difference in reflectance which is applicable to the optical recording media. The Sn film obtained by the thermal decomposition included SnO, and consequently it showed a small difference in reflectance from that of SnNx film.

Analytic description of the chemical erosion of graphite by hydrogen ions

Abstract: One main concern about the use of graphite as a plasma facing material is the enhanced erosion under hydrogen bombardment due to hydrocarbon formation. In view of the lifetime evaluation of plasma exposed carbon components and of impurity production in present and future machines such as ITER, an analytical expression for the erosion yield by chemical sputtering for the relevant energies, temperatures and incident fluxes is of special importance. An extrapolation to fluxes and energies relevant for high density divertor plasmas has not been possible up to now on the basis of semiempirical fits to laboratory data. Starting from a short review of the existing empirical formulas, recent detailed investigations of the atomistic processes for the thermally activated hydrocarbon emission are described, which enable the formulation of an improved analytical description including the ion flux as a parameter. The chemical erosion of graphite by hydrogen bombardment results from two processes: the thermally activated hydrocarbon emission, Ytherm, and a surface process at low energies and low temperatures resulting from the kinetic ejection of surface hydrocarbon complexes from collisional energy transfer, Ysurf. The new analytic description can be fitted well to the existing data for ion beam erosion, and extrapolation to divertor relevant fluxes is possible. At high ion fluxes the maximum of chemical erosion is shifted to higher temperatures, where annealing of damaged structures leads to a stronger reduction of Ytherm than previously estimated. There are no data on a possible flux dependence of Ysurf, leaving still some uncertainty in extrapolation

Sputtering system using cylindrical rotating magnetron electrically powered using alternating current

Abstract: A sputtering system (50) using an AC power supply (59) in the range of 10 kHz to 100 kHz uses two rotatable cylindrical magnetrons (60, 62). The rotatable cylindrical magnetrons (60, 62), when used for depositing a dielectric layer onto a substrate (80), clean off dielectric material that is deposited onto the target (64, 65). This prevents a dielectric layer on the target (64, 65) from acting like a capacitor and may help avoid arcing. Additionally, an impedance-limiting capacitor (58) can be placed in series in the electrical path between the targets (64, 65) through the transformer (54) so as to reduce arcing. This impedance-limiting capacitor (58) has a value much larger than the capacitor used to couple the power supply (59) to a target (64, 65) in radio frequency sputtering systems.

Reactive magnetron sputter deposited CNx: Effects of N2 pressure and growth temperature on film composition, bonding, and microstructure

Abstract: The effects of growth processes on the chemical bond structure, microstructure, and mechanical properties of carbon–nitride (CNx) thin films, deposited by reactive magnetron sputtering in a pure N2 discharge, are reported. The film deposition rate RD increases with increasing N2 pressure PN2 while N/C ratios remain constant. The maximum N concentration was ∼35 at. %. RD was found to be dependent upon the film growth temperature Ts. For a given PN2, RD decreased slightly as Ts was increased from 100 to 600 °C. The variations in RD with both PN2 and Ts can be explained by ion‐induced desorption of cyano radicals CNx from both the target and growth surfaces during deposition. X‐ray photoelectron spectroscopy and Fourier transform infrared spectroscopy (FTIR) analyses showed that N atoms in films grown at Ts≳350 °C with low nitrogen partial pressures PN2, ∼2.5 mTorr, were bound to C atoms through hybridized sp2 and sp3 configurations. For low Ts=100 °C and higher PN2, 10 mTorr, triple‐bonded C≡N was detected ...

Preparation and characteristics of nickel oxide thin film by controlled growth with sequential surface chemical reactions

Abstract: Nickel oxide films have been fabricated by various physical and chemical vapour deposition (CVD) techniques such as reactive sputtering [1] and plasma-enhanced chemical vapour deposition [2] because their chemical stability as well as their optical and electrical properties are excellent. If the fabrication technology could lead to growth on an atomic scale, it would be rauch more interesting also for applications to soft X-ray multilayers and neutron optics because compound multilayer structures consisting of NiXx (X = C, N, dry air) layers have been the focus of recent attention [3]. In recent years, atomic layer deposition of A1203 [4-7], TiO2 [8, 9] and multilayers based on A1203/TiO2 [10] by sequential surface chemical reactions has been reported. This deposition technique could be used to sequentially dose a surface with appropriate chemical precursors to promote surface chemical reactions that are inherently self-limiting. The selflimiting nature of the surface reactions enables precise control of the thickness of the deposited layers on an atomic scale and gives rise to homogeneous films on large areas. In this work, bis-methylcyclopentadienyl nickel (Ni(CH3CsH4)2) and hydrogen peroxide (H202) were used for controlled growth of amorphous nickel oxide films by sequential surface chemical reactions, because amorphous structures are suitable for applications to soft X-ray multilayers due to their smooth surface and interface. The experimental setup comprised a stainless steel vacuum chamber with computer-controlled leak and gare valves, a capacitor manometer and a substrate holder connected to a heater. The substrate was cut from a (100)-orientated Si wafer. As vapour sources, high purity bis-methylcyclopentadienyl nickel (Ni(CH3C»H4)2; Trichemical Laboratory Inc.) and H 2 0 2 w e r e used. As shown in Fig. 1, the vapour pressure of Ni(CH3CsH4)2 is high among those of nickel compounds [11], which makes it rather easy to u s e . H 2 0 2 w a s prepared by vacuum distilling

Superlattices of PbZrO3 and PbTiO3 prepared by multi‐ion‐beam sputtering

Abstract: Artificial superlattices consisting of antiferroelectric PbZrO3 (PZO) and ferroelectric PbTiO3 (PTO) have been fabricated by a multi‐ion‐beam sputtering technique. The epitaxial PZO and PTO layers were sequentially grown on (100)Pt/MgO substrates at a low substrate temperature of 415 °C with a periodicity from 5 to 100 perovskite unit cells. X‐ray diffraction studies revealed the superlattice structures with a‐axis oriented PTO layers on a‐axis oriented PZO layers. The dielectric and ferroelectric properties of the superlattice films were enhanced with increasing periodicity.

Sputtered molybdenum oxide thin films for NH3 detection

Abstract: Thin films of MoO3 for gas sensing applications have been deposited by reactive sputtering using a metallic molybdenum target. After annealing at 500°C in air, the layers consist of rhombic molybdenum trioxide with a (010) texture. The morphology of the layers considerably depends on the film thickness. Electrical conductivity measurements with different test gases show that MoO3 layers are suitable for NH3 detection at operating temperatures between 400 and 450°C.

Electrical and Optical Properties of Copper Oxide Films Prepared by Reactive RF Magnetron Sputtering

Abstract: Copper oxide thin films were prepared by reactive rf magnetron sputtering of a pure copper target in an oxygen-argon atmosphere. The phases of the deposited films strongly depend on the oxygen content in the sputtering gas. X-ray diffraction studies show that by controlling the oxygen partial pressure single phase Cu2O and CuO can be obtained. The resistivity of the Cu2O film in the present study is 43 Ω cm. The optical constants were evaluated from transmission and reflection measurements.

Studies of grain size effects in rf sputtered CdS thin films

Abstract: CdS thin films with various grain sizes were produced by rf sputtering and in situ postannealing processes. For a series of annealing time intervals, the average grain sizes of an as‐deposited thin film with thickness ∼4000 A were found to vary from ∼280 to ∼1500 A. Three bands located in the green, yellow, and red regions were observed in photoluminescence (PL) spectra of these as‐deposited films. The temperature dependence of (PL) spectra of CdS microcrystals was investigated. The variations of the (PL) spectra with average grain size and thickness of CdS thin films were also studied. It was found that the intensity of the yellow band was increased as increasing the film thickness while the intensity of the red band was decreased as the grain size of the film became larger. The peak positions of the yellow and red bands were found to be blue‐shifted as the films became thinner.

Microstructure and magnetism in FeTaN films deposited in the nanocrystalline state

Abstract: As‐deposited, magnetically soft nanocrystalline FeTaN films are successfully grown by dc‐magnetron reactive sputtering. Growth conditions are instrumental in extending the solubility limit of Ta in the bcc FeTa alloy. Nitrogen incorporation in FeTa films is found to be much higher than in Fe films and can be explained in terms of thermochemistry using a large Ta‐N interaction coefficient. The influence of different alloying elements is discussed theoretically, with regard to the metal‐nitrogen affinity. A ‘‘typical columnar microstructure’’ associated with the sputtering process is identified and its evolution versus the extent of nitrogenation is described in detail. Stress, magnetostriction, resistivity, and magnetic properties are respectively described as a function of both Ta and N contents of the films. The magnetic behavior of as‐deposited nanocrystalline FeTaN is found to be very sensitive to both the dimension of the grains, their morphology and the nature of the grain boundary material which rep...

Plasma reactor using UHF/VHF and RF triode source, and process

Abstract: A plasma reactor preferably uses a split electrode which surrounds a plasma dome region of the reactor, is driven by high frequency energy selected from VHF and UHF and produces an electric field inside the electrode, parallel to the wafer support electrode. A static axial magnetic field may be used which is perpendicular to the electric field. The above apparatus generates a high density, low energy plasma inside a vacuum chamber for etching metals, dielectrics and semiconductor materials. Relatively lower frequency, preferably RF frequency, auxiliary bias energy applied to the wafer support cathode controls the cathode sheath voltage and controls the ion energy independent of density. Various etch processes, deposition processes and combined etch/deposition processes (for example, sputter/facet deposition) are disclosed. The triode (VHF/UHF split electrode plus RF wafer support electrode) provides processing of sensitive devices without damage and without microloading, thus providing increased yields.

The early stages of solid-state reactions in ni/al multilayer films

Abstract: Ni/Al multilayer films with pair thicknesses of 10 and 20 nm and with overall compositions in the range 48–88 at. % Al were prepared by sputtering. For comparison, Ni‐Al alloy films in the same concentration range were prepared by co‐deposition of the elements. The films were studied by x‐ray diffraction, electron diffraction, and differential scanning calorimetry. It was found that the B2 NiAl phase with a metastable concentration of approximately 63 at. % Al was the first phase to grow upon annealing of the multilayer films. The growth of this phase could be described by Johnson–Mehl–Avrami kinetics with an activation energy of 0.8 eV and an Avrami exponent of 0.5. This low activation energy was consistent with the observation that the phase had formed during deposition and continued to grow upon annealing at low temperatures to thicknesses of a few nanometers. If the reactant phases were not fully consumed by the B2 phase growth, the subsequent reaction was the formation of NiAl3, previously thought to...