Showing papers on "Sputtering published in 1986"

The microstructure of sputter-deposited coatings

Abstract: Microstructure is a critical consideration when polycrystalline or amorphous thin films are used for applications such as microcircuit metallization layers and diffusion barriers. The trend in device fabrication toward lower processing temperatures means that such coatings must often be deposited at substrate temperatures T that are low relative to the coating material melting point Tm. The structure of vapor deposited coatings grown under these conditions consists typically of a columnar growth structure, defined by voided open boundaries, which is superimposed on a microstructure which may be polycrystalline (defined by metallurgical grain boundaries) or amorphous. The voided growth structure is clearly undesirable for most applications. Its occurrence is a fundamental consequence of atomic shadowing acting in concert with the low adatom mobilities that characterize low T/Tm deposition, and its formation can be enhanced by the surface irregularities which are common to microcircuit fabrication. This pap...

Titanium aluminum nitride films: A new alternative to TiN coatings

Abstract: TiAl films have been produced in various compositions by using the sputter ion plating process. Films sputtered reactively from a target with the composition of TiAl 50:50 at. % have been deposited with a composition of 27.5 at. % Ti, 28.9 at. % Al, and 43.6 at. % N. The crystal structure found was that of sodium chloride with a lattice parameter of 4.20 A; the microhardness such films was found to be HV 2100–2300. The incorporation of Al into the nitride films improves the oxidation resistance as well as the cutting performances of TiAlN coated drills. TiN films start to oxidize at a temperature level of 550 °C, whereas TiAl coatings react with hot air at a temperature of 800 °C severely. TiAlN coated drills have been tested with two different steels and performed better by a factor >2 compared with TiN coated drills.

Thermal CVD/PECVD reactor and use for thermal chemical vapor deposition of silicon dioxide and in-situ multi-step planarized process

Abstract: A high pressure, high throughput, single wafer, semiconductor processing reactor is disclosed which is capable of thermal CVD, plasma-enhanced CVD, plasma-assisted etchback, plasma self-cleaning, and deposition topography modification by sputtering, either separately or as part of in-situ multiple step processing. The reactor includes cooperating arrays of interdigitated susceptor and wafer support fingers which collectively remove the wafer from a robot transfer blade and position the wafer with variable, controlled, close parallel spacing between the wafer and the chamber gas inlet manifold, then return the wafer to the blade. A combined RF/gas feed-through device protects against process gas leaks and applies RF energy to the gas inlet manifold without internal breakdown or deposition of the gas. The gas inlet manifold is adapted for providing uniform gas flow over the wafer. Temperature-controlled internal and external manifold surfaces suppress condensation, premature reactions and decomposition and deposition on the external surfaces. The reactor also incorporates a uniform radial pumping gas system which enables uniform reactant gas flow across the wafer and directs purge gas flow downwardly and upwardly toward the periphery of the wafer for sweeping exhaust gases radially away from the wafer to prevent deposition outside the wafer and keep the chamber clean. The reactor provides uniform processing over a wide range of pressures including very high pressures.

Physics of Plasma-Wall Interactions in Controlled Fusion

Abstract: In the areas of plasma physics, atomic physics, surface physics, bulk material properties and fusion experiments and theory, the following topics are presented: the plasma sheath; plasma flow in the sheath and presheath of a scrape-off layer; probes for plasma edge diagnostics in magnetic confinement fusion devices; atomic and molecular collisions in the plasma boundary; physical sputtering of solids at ion bombardment; chemical sputtering and radiation enhanced sublimation of carbon; ion backscattering from solid surfaces; implantation, retention and release of hydrogen isotopes; surface erosion by electrical arcs; electron emission from solid surfaces;l properties of materials; plasma transport near material boundaries; plasma models for impurity control experiments; neutral particle transport; particle confinement and control in existing tokamaks; limiters and divertor plates; advanced limiters; divertor tokamak experiments; plasma wall interactions in heated plasmas; plasma-wall interactions in tandem mirror machines; and impurity control systems for reactor experiments.

Preparation of c‐axis oriented PbTiO3 thin films and their crystallographic, dielectric, and pyroelectric properties

Abstract: Highly c‐axis oriented and epitaxial PbTiO3 thin films were grown on MgO single crystals and epitaxial Pt film substrates by the rf‐magnetron sputtering method. The films with a 98% c‐axis orientation rate were obtained under low deposition rate (<20 A/min) and low gas pressure (∼1 Pa) using a PbO‐rich target. Phase transition of the PbTiO3 thin film was studied by high‐temperature x‐ray diffraction. It was found that the c‐axis of the tetragonal phase was parallel to the substrate just below Tc and the c‐axis becomes perpendicular to the substrate with lowering of temperature. These films show high resistivity (∼1010/Ω cm). It was found that significant pyroelectric currents are detected on all specimens without poling treatment. The polarization directions of the films are the same in all specimens. One of these films had a low relative dielectric constant of 97 and a high pyroelectric coefficient of 2.5×10−8 C/cm2 K without poling treatment. These films will be suitable for applications such as pyroelectric infrared detector and piezoelectric transducer.

Charged particle fluxes from planar magnetron sputtering sources

Abstract: We have investigated the charged particle fluxes from circular planar magnetrons with different magnetic field configurations and report measurements of the currents to earthed substrates, the substrate self‐biasing voltages, the ion currents to substrates at −100 V, and deposition rates as functions of axial and radial positions with respect to the target. The magnetrons fall into two classes, whose characteristics are explained in terms of electron motion in inhomogeneous magnetic fields. Both low and high electron/ion bombardment of the growing film can be achieved by small alterations to the magnetic field configuration.

On structure and properties of sputtered Ti and Al based hard compound films

Abstract: After investigating basic correlations between process and film characteristics in previous works new multicomponent hard coatings, on the basis of Ti–Al and Ti–Zr, have been deposited by magnetron sputtering. These ternary and quaternary nitrides are crystallizing in a face centered cubic TiN lattice with reduced or enlarged lattice parameters depending on the amount and the radius of foreign atoms. Improved wear behavior compared to chemical vapor deposition (CVD) TiN coatings has been stated with (Ti,Al)N, (Ti,Zr)N, and (Ti,Al,V)N coatings. According to these results the development of the coating material itself will be of major interest in the future.

Ferroelectric (Pb,La)(Zr,Ti)O3 epitaxial thin films on sapphire grown by rf-planar magnetron sputtering

Abstract: Ferroelectric (Pb,La)(Zr,Ti)O3 (PLZT) thin films have been epitaxially grown on the c plane of sapphire by rf‐planar magnetron sputtering. The sputtering conditions were investigated to obtain epitaxial and transparent films. Dielectric, piezoelectric, and electro‐optic properties of the films were measured. Piezoelectricity of the PLZT(28/0/100) film was confirmed and was as strong as that of BaTiO3. Excellent quadratic electro‐optic effects for PLZT(28/0/100) and PLZT(9/65/35) films and a linear electro‐optic effect for PLZT(21/0/100) film were observed at 0.633‐μm wavelength. Epitaxial PLZT thin film on sapphire is presently the most promising material for new functional devices.

Optical constants and associated functions of metastable diamondlike amorphous carbon films in the energy range 0.5–7.3 eV

Abstract: The complex refractive index N(ω)=n+ik and the complex dielectric constant e(ω)=e1+ie2 are presented for diamondlike amorphous carbon (a‐C) films in the photon energy range 0.5–7.3 eV. The effective number of valence electrons neff per carbon atom, the static dielectric constant e0,eff, and the energy loss function Im[−1/e(ω)] are deduced via the use of sum rules and are used to interpret the optical data. The a‐C films were deposited using an unbalanced magnetron gun to sputter a graphite target (effective sputtering area of 20 cm2) in ultrapure argon gas. The magnetron is characterized by a high deposition flux of condensing atoms (1.5×1014–1.2×1016 cm−2 s−1) and a concomitant high ion flux (6×1014–2.5×1016 cm−2 s−1). A series of films were prepared by sputtering at different power levels in the range 5–500 W. Insulating substrates were used which allowed the films to self‐bias negatively with respect to the plasma, so that the films were bombarded during their growth by Ar+ ions of energy 16–13 eV at a...

Theory of thin‐film orientation by ion bombardment during deposition

Abstract: We study the development of orientational order in thin films grown with off‐normal incidence ion bombardment during deposition. The overall orientational order in our model results from the dependence of the sputtering yield on grain orientation. We demonstrate that the degree of orientational order at the surface of a thick film grows slowly with increasing ion flux until, at a critical value of the flux, it begins to rise more steeply and then saturates at its maximum value. The time needed to approach the thick‐film limit displays a peak as the ion flux is varied. We compare our work with the experimental results of Yu et al. [Appl. Phys. Lett. 47, 932 (1985)] and use our results to show how the deposition technique can be optimized.

Unbalanced dc magnetrons as sources of high ion fluxes

Abstract: We report the characteristics of a new design of magnetron sputter source (a UM‐gun), based on the principle of an unbalanced magnetic design, and capable of giving ion fluxes at the substrate greater than the flux of depositing atoms The dependencies of ion flux and self‐bias potential at a typical substrate position for certain target materials (copper and silicon), gas pressures (025–5 Pa), gas compositions (Ar with O2, N2, and He), and sputtering power levels (up to 2 kW) have been measured for a particular UM‐gun The results show that such guns can be characterized approximately by an ion flux proportional to the discharge current and a constant self‐bias potential

Interlayer dielectric process

Abstract: A method for producing a film over a topologically non-planar surface of a material which has a sputter etch rate which is higher in a direction parallel to the plane of the wafer than in a direction perpendicular to the plane of the wafer. Key steps in the process include first, depositing the material by plasma enhanced chemical vapor deposition while simultaneously sputter etching it. Then second, sputter etching the material. Using this two step process, a substantially conformal or sloped film is produced by repeating the steps consecutively until the desired thickness is obtained. The film can then be substantially planarized if desired, by an extended sputter etch to selectively remove material having a sloped surface rather than a flat surface, since the etch rate is higher parallel to the plane of the wafer than perpendicular to the wafer. If a thicker planar surface is desired, additional material can then be deposited by steps of simultaneous plasma chemical vapor deposition and sputter etch, or by consecutive steps of simultaneous plasma deposition and sputter etch followed by sputter etching.

Unbalanced magnetron ion-assisted deposition and property modification of thin films

Abstract: Unbalanced magnetron (UM‐gun) sputtering sources with the unique characteristic of a high deposition rate and concomitant high ion flux represent an exciting new development in ion‐assisted deposition of thin films. We have used a UM‐gun capable of producing ion current densities up to 5 mA cm−2 (ion flux 3×1016 cm−2 s−1) when operated at a power of 500 W to produce a variety of thin films of amorphous and crystalline materials by varying both the bombarding ion energy in the range 2–100 eV and the ion/atom arrival rate ratio in the range 0.4–10. The great flexibility and usefulness of UM‐guns is demonstrated with examples which include (a) hard diamondlike a‐C films prepared under very low ion energy (13–16 eV) bombardment which possess a metastable bonding configuration consisting of a mixture of tetrahedral and trigonal coordination that varies with ion energy, (b) hard and wear‐resistant TiN films whose electrical and optical properties change dramatically with ion bombardment, and (c) Ni/Cr alloy fil...

Model for ion-assisted thin-film densification

Abstract: A theoretical model to explain the densification of thin films by ion assistance is described. The model takes advantage of previously developed fast methods for three‐dimensional Monte Carlo cascade computations and assumes a low thermal adatom mobility. It is shown that ion incorporation and recoil implantation of surface atoms lead to a film densification slightly below the surface of a growing film and that the density enhancement depends on the ability of vapor atoms to refill surface vacancies which are created by sputtering and driven‐in atoms. In particular, the time‐dependent mass density profiles evolving during the growth of a 600‐eV, oxygen‐assisted, vapor‐deposited ZrO2 film has been determined and good agreement with experiment is obtained.

Morphology and properties of sputtered (Ti,Al)N layers on high speed steel substrates as a function of deposition temperature and sputtering atmosphere

Abstract: (Ti,Al)N layers were prepared by reactive dc and radio‐frequency (rf) magnetron sputtering onto polished flat high speed steel (HSS) surfaces. The rectangular samples were mounted on a special sample holder providing a temperature gradient in the range of 500 °C to room temperature along the length of the sample. The (Ti,Al)N layers were deposited at various N2 and Ar pressures. The target was a Ti–50 at. % Al alloy. The film morphology and composition was observed by scanning electron microscopy (SEM) and Auger electron spectroscopy (AES), respectively, and correlated to mechanical properties like hardness and critical load (scratch test). The results are discussed with the respect of the sputtering conditions.

Electrochromic hydrated nickel oxide coatings for energy efficient windows: Optical properties and coloration mechanism

Abstract: Durable electrochromic coatings of hydrated nickel oxide were produced by reactive rf magnetron sputtering of Ni followed by treatment in KOH. Spectrophotometry was used to assess the achievable modulation of luminous and solar transmittance and to verify that the studied material is interesting for ‘‘smart window’’ applications. 15N nuclear reaction analysis suggested that coloration occurred upon hydrogen extraction.

Mechanisms of atomic ion emission during sputtering

Abstract: Several major experimental and theoretical findings made in the last few years on the mechanisms of secondary ion emission are summarized. There is a strong indication that the phenomena can be divided into two categories: Ion emission from the surfaces of metals and semiconductors tends to have a strong correlation with the work function and can be described quite well with an electron tunneling model. Ion emission from systems which show large chemical enhancement has only a weak correlation with global surface properties like the work function or the bandgap. Instead it seems to be related more to local chemical bonds and coordination numbers. A localized bond breaking picture may be more appropriate in these circumstances.

Sputtering of sodium on the planet Mercury

Abstract: It is shown here that ion sputtering cannot account for the observed neutral sodium vapor column density on Mercury, but that it is an important loss mechanism for Na. Photons are likely to be the dominant stimulus, both directly through photodesorption and indirectly through thermal desorption of absorbed Na. It is concluded that the atmosphere produced is characterized by the planet's surface temperature, with the ion-sputtered Na contributing to a lesser, but more extended, component of the atmosphere.

Control of thin film orientation by glancing angle ion bombardment during growth

Abstract: Glancing angle ion bombardment during thin film deposition is shown to have a pronounced alignment effect on crystallographic orientation. Restricted fiber texture is achieved in Nb films deposited at room temperature onto amorphous silica substrates by Ar ion beam sputtering, with simultaneous bombardment by 200 eV Ar+ ions at 20° from glancing angle. The alignment direction corresponds to a channeling direction for the incident ions between (110) planes, for which a low sputtering yield is expected. The degree of alignment is measured as a function of ion/atom arrival rate ratio up to 1.3 Ar+ ions per Nb film atom, and is shown to increase monotonically with the fraction resputtered. Also, the fiber axis tilts slightly towards the incident ion beam direction, favoring the channeling direction.

Radiation effects in glasses

Abstract: Charged particle irradiation of glasses introduces network damage and alters the chemical composition. Compositional modifications are due to internal electric field formation and/or to sputtering processes, connected to different stopping power regimes (electronic or nuclear). In this paper we discuss the observed alkali migration, in alkali containing glasses, induced by electrons, protons and heavy-mass ion bombardment on the basis of phenomenological models. Particular emphasis is placed on the evidence of cooperative effects and enhanced-diffusion processes, analyzed in terms of the Onsager formalism in the thermodynamics of irreversible processes. Correlation between the alkali sputtering cross-section and the stopping power regimes of incident particles will be presented.

Applications of Monte Carlo simulation in the analysis of a sputter‐deposition process

Abstract: Practicality of the Monte Carlo (MC) method developed for the analysis of the particle transport process in sputter‐deposition was examined. Titanium film thickness distributions on both faces of a planar substrate facing and not facing a planar‐magnetron‐type target were compared with corresponding calculated profiles. The results show that sufficient performance of the MC method can be obtained in the usual sputtering condition up to the argon pressure beyond which the majority of particles are transported by the thermal diffusion process.

Surface Damage on GaAs Induced by Reactive Ion Etching and Sputter Etching

Abstract: surface damage induced by reactive ion etching (RIE) using various gases is compared with sputter etching using inert gases. Anisotropic etching of with minimal surface damage can be obtained with most of the RIE conditions used. Sputter etching using inert gases introduces substantial damage on the surface, and the degree of damage is inversely proportional to the ion mass. In addition, we have found that the damage induced by Ar sputter etching can be greatly reduced by the introduction of reactive gases during etching. Recovery of the diode characteristics is observed after removing 500A of the etched surface using wet chemical solution or by removing 200A of the etched surface using RIE in at 30V.

Deposition and planarizing methods and apparatus

Abstract: A layer of a substance such as an aluminum alloy is deposited, preferably by sputtering, onto a surface of a substrate such as a semiconductor wafer. The deposited substance is redistributed by bombarding the layer with ions. The ion bombardment may be induced by applying low frequency RF excitation at about 5 KHz -1 MHz to the substrate.

Optical behavior of sputter-deposited vanadium pentoxide

Abstract: A series of V–O alloy films were sputter deposited on glass substrates using a vanadium target and rf-excited Ar/O2 discharges containing 2%–8% O2. On the basis of x-ray results, the films were nominally identified as vanadium pentoxide. Optical transmission and reflection characteristics were measured by double-beam spectrophotometry in the 390- to 700-nm-wavelength region. From these measurements, the absorption coefficient α was determined as a function of the incident photon energy hν. The absorption edge of all films showed two distinct regions of behavior: a high photon energy region in which α varied linearly with (hν)2 and a low-energy tail. The behavior of α is discussed in terms of the structural and electronic changes in the films due to nonstoichiometry and compared to results obtained for single crystal V2O5.

Ultraviolet detectors in thin sputtered ZnO films.

Abstract: Ultraviolet-sensitive photodiodes have been made using the Schottky barrier formed in the contact layer between a thin sputtered layer of ZnO and Au. The sputtering parameters for the ZnO layer were optimized. The IV characteristics and the sensitivity spectra of the ZnO–Au photodiodes were investigated.

Internal stress and adherence of titanium nitride coatings

Abstract: Titanium nitride coatings were deposited on various substrates by sputter ion plating and the state of stress was determined by the sin2 ψ method. The lattice distortions that occur in the nitride coatings have been resolved in terms of a macrostrain and microstrain, as determined from the breadth of the x‐ray reflections, and the origins of each are discussed. The internal stress present in a coating is shown to consist of two components, one thermal in origin and the other structural, and that its sign and magnitude varies with substrate material and bias potential. During cooling from deposition temperature partial relaxation of this internal stress (macrostrain) occurs via two mechanisms, plastic deformation of the substrate and yield of the film. The internal stress was completely relaxed on dissolution of the substrate, accompanied by a decrease in the lattice parameter of the film. By comparing the results from substrates biased and unbiased during deposition, and measurements made on adherent and free‐standing coatings, the microstrain measurements have been separated into two parts, one due to distortions at the grain boundaries and one due to defects in the crystallites. A model is proposed that accounts for all the experimental observations; this also provides an explanation for the distortions from cubic symmetry reported in titanium and hafnium nitride films.