Electron-beam Sputtering Research Articles

42.3: High‐Luminance Green Electroluminescence of Sputtered ZnS:TbOF

AbstractZnS:TbOF thin films have been deposited by electron‐beam evaporation and RF magnetron sputtering onto iFire thick dielectric substrates. Films deposited by the two techniques have different morphologies, luminance and aging characteristics. Bright and stable green electroluminescence of L60 over 2000 cd/m2 at 120 Hz has been achieved by sputtering.

AN APPROACH OF SHADOW MASK FOR DEEP-HOLES PATTERNING

This paper presents a method to pattern metal in deep holes. We do this by etching holes through a separate wafer to form a shadow mask and then depositing metal by electron-beam evaporation or sputtering through the holes on this shadow mask on to the device wafer. The integration of deep reactive ion etching (DIRE) and KOH wet etching micromachining techniques for the realization of shadow mask in this paper simplifies the fabrication process and provides high resolution.

Development of optical coatings for 157-nm lithography. I. Coating materials.

In a basic study to identify low-loss optics for applications in F2 lithography, five potential coating materials (AlF3, Na3AlF6, MgF2, LaF8, and GdF3) and three deposition methods (thermal evaporation by a resistance heater and by electron beam and ion-beam sputtering) were investigated in the vacuum ultraviolet (VUV) region. Samples were supplied as single-layer coatings on CaF2 substrates by four Japanese coating suppliers. Refractive indices (n) and extinction coefficients (k) of these coatings at 157 nm were evaluated; the transmittance and the reflectance were measured by a VUV spectrometer and were compared. As a result, resistance heating thermal evaporation is seen to be the optimal method for achieving low-loss antireflection coatings. The relation among optical constants, microstructures, and stoichiometry is discussed.

Processing-induced electron traps in n-type GaN

We have used deep-level transient spectroscopy (DLTS) to investigate the electron trap defects introduced in n-GaN during the fabrication of Pt Schottky contacts by electro-deposition, electron beam deposition and sputter deposition under three different deposition conditions. The results indicate that electro-deposition is the only one of these processes that does not introduce any defects. Diodes fabricated by this technique also have the best rectification properties. Both electron beam deposition and sputter deposition introduce electron traps in concentrations that increase towards the Pt/GaN interface. However, sputter deposition at a lower power and higher pressure results in significantly reduced defect concentrations and improved rectification properties.

Controlled Planar Interface Synthesis by Ultrahigh Vacuum Diffusion Bonding/deposition

An ultrahigh vacuum (UHV) diffusion bonding/deposition instrument was designed and constructed, which can produce homophase and heterophase planar interfaces from a wide array of materials. The interfaces are synthesizedin situby diffusion bonding of two substrates with or without various interfacial layers, at temperatures up to about 1500 °C. Substrate surfaces can be heat treated, ion-beam sputter cleaned, and chemically characterizedin situby Auger electron spectroscopy prior to deposition and/or bonding. Bicrystals can be synthesized by bonding two single-crystal substrates at a specified orientation. Interfacial layers can be deposited by electron beam evaporation and/or sputter deposition in any layered or alloyed combination on the substrates before bonding. The instrument can accommodate cylindrical and/or wafer type specimens whose sizes are sufficient for fracture mechanical testing to measure interface bond strength. A variety of planar interfaces of metals, semiconductors, and ceramics were synthesized. Examples of bonded stainless steel/Ti/stainless steel, Si/Si, and sapphire/sapphire interfaces are presented.

Temperature-dependent magnetism in transition metal films observed by magnetic force microscopy and classical magnetometry

Pure Co and Pd–Co alloy films were prepared using electron beam evaporation and sputtering. They were characterized by superconducting quantum interference device magnetometry and magnetic force microscopy (MFM). The magnetic hysteresis curves for the Co film show that the magnetization direction is in the plane of the film. The magnetization data reveal a Curie temperature for the alloy of 370 K, and a preference for the moments to orient perpendicular to the film. MFM images of magnetic domains were obtained for 298 and 323 K. In the Pd–Co film, the phase contrast between the oppositely magnetized domains decreases by 35% as the temperature of the film is raised, even though the dominant length scale of the domains (about 0.25 μm) remains unchanged. A very different result was obtained for the pure Co film: Over the same temperature range the phase contrast in the magnetic images in the Co film decreased only by 10%. This indicates that the observed behavior in the Pd–Co film is mainly due to the much more rapid change in magnetic properties as a function of temperature. We also observe that, while less temperature dependent, the contrast of the magnetic domain images of the Co film is smaller than that of the Pd–Co, a result most likely due to the reorientation of the moments on going from the pure Co film to the Pd–Co film.

High Jc YBCO films on biaxially textured Ni with oxide buffer layers deposited using electron beam evaporation and sputtering

Epitaxial buffer layers of CeO 2 and yttria-stabilized ZrO 2 (YSZ) have been deposited on biaxially textured nickel using conventional electron beam evaporation and r-f sputtering. Epitaxial films of YBa 2Cu 3O 7− δ (YBCO) have been then grown on these buffered substrates using pulsed laser deposition (PLD). Despite intermittent exposure of the buffered substrates to 1 atm air, the resulting YBCO conductors exhibited transport critical current densities ( J c) of 0.8 MA/cm 2 at 77.3 K and H=0 T. The dependence of J c of these conductors on temperature and magnetic field is similar to that of conductors prepared solely by in situ PLD. These results suggest that it may be possible to use more flexible and easily scalable fabrication methods for preparing long YBCO conductors.

Epitaxial Growth of YBa2CH3O7-δ Films on Rolling-Assisted Biaxially Textured Substrates (RABiTS) Produced by Pulsed Laser Ablation at Low Temperatures

AbstractEpitaxial YBa2Cu3O7-δ (YBCO) films were fabricated using laser ablation of YBCO onto rolling-assisted-biaxially-textured-substrates (RABiTS) at a temperature of 650°C. The configuration of the sample was YBCO/YSZ/CeO/Ni. The CeO2 and YSZ buffer layers were deposited using electron-beam evaporation and sputtering, respectively. Both of these techniques are considered to be industrially scalable. SEM images of the YBCO reveal a range of structures ranging from jumbled a-axis to dense c-axis morphologies depending upon the deposition conditions. X-ray θ-2θ scans show a similar c-axis dependence on the deposition conditions.

Evolution mechanism of nearly pinning-free platinum/n-type indium phosphide interface with a high Schottky barrier height by in situ electrochemical process

Recently, unusually high Schottky barrier heights (SBHs) have been realized by our group on n-type InP and related materials by an in situ electrochemical deposition of Pt. In an attempt to understand the underlying mechanism of the SBH enhancement, this article investigates in detail the evolution process of the metal (Pt, Ni, Co, and Ag)-InP interface during the in situ electrochemical process, using current–voltage, capacitance voltage, deep level transient spectroscopy, x-ray photoelectron spectroscopy, Raman, atomic force microscope, and scanning electron microscope measurements. Pt deposition by the electrochemical process realized an oxide-free, defect-free, stress-free, and nearly pinning-free interface, whereas Pt deposition by conventional electron beam evaporation and sputtering processes as well as Ag, Ni, and Co deposition by the electrochemical process gave rise to stressed and pinned interfaces. The observed large process dependence of SBH can be explained by none of the metal induced gap state model, the unified defect model, and the effective workfunction model. It is explained here by the disorder induced gap state model.

Metal contacts to gallium arsenide

In this paper, some aspects that determine the properties of Schottky and ohmic contacts to GaAs are discussed. For Schottky barrier diodes (SBD), we present results of a comprehensive study involving 41 different metals. We pay special attention to Ru and show that its thermal and chemical stability makes it ideal for use in devices operating above room temperature and for experiments involving annealing. Further, we discuss the effect of different metallization methods on SBD properties and show that methods which use energetic particles, such as electron beam deposition and sputter deposition, often result in inferior SBD properties—the consequence of electrically active defects introduced by the energetic particles at and close to the semiconductor surface. The advantages of using Ru as contact material to GaAs are that it forms high quality, thermally stable Schottky contacts to n-GaAs and thermally stable ohmic contacts with low specific contact resistance to p-GaAs. The versatile applicability of Ru contacts makes them extremely important for future use in devices such as heterojunction bipolar transistors and solid state lasers.

Physical vapor deposition tool coatings

Physical vapor deposition (PVD) of hard coatings such as titanium nitride have been an industrial reality since the beginning of the 1980s. Two PVD processes, low voltage electron beam and cathodic arc deposition, were responsible for the early commercial success of hard coatings on high speed steel tooling. Since that time, two other PVD processes have also been prosperous in the industrial world—high voltage triode electron beam and unbalanced magnetron sputtering. There are many similarities and differences between these four PVD hard coating processes, but not all of the commonly used PVD hard coatings can be deposited well in the four systems. Titanium nitride and titanium carbonitride are the two most widely used PVD tool coatings, and they can be deposited in all four PVD systems. Titanium aluminum nitride can be deposited easily with the unbalanced magnetron process and also with the cathodic arc processes as long as cast targets are used. Uniform composition cannot be maintained with the electron beam processes because of the different vapor pressures of titanium and aluminum. New PVD hard coatings are being developed and applied. Diamond-like carbon is now being tried for some non-ferrous cutting applications, and metal-carbon films are showing promise. Polycrystalline nitride superlattice coatings made of thin alternating layers of two hard coatings such as titanium nitride and niobium nitride are showing potential for abrasive cutting situations because of the very high hardness (up to 5200 HV) of these coatings. The search continues for potentially even better tool coatings. An intense effort is underway to produce the superhard crystalline carbon nitride, which is predicted to have a hardness as hard or even harder than diamond. Similarly, cubic boron nitride (CBN) coatings are still very much in the development stage. Thin CBN coatings can now be deposited up to approximately 2000 Å in thickness, but stress in the films prevents thicker films from being made. Aluminum oxide, which has been very difficult to make by PVD techniques, except in the very slow r.f. sputtering mode, can now be deposited in the d.c. magnetron mode when pulsed power is used.

Perpendicular spin valve behavior in a microstructured Co/Cu-Cu oxide/Co trilayer

In this article we report a perpendicular spin valve behavior in a microstructured noncoupling magnetic trilayer system of Co/Cu-Cu oxide/Co. The Co thin films having markedly different coercivity Hc were prepared with a vacuum evaporation with electron beam (Hc= 20–30 Oe) and rf sputtering (Hc= 90–260 Oe), which enables the selective switching of the magnetization in the base and counter Co layers. The film surface of the Cu was oxidized by the rf sputter etching, which results in the increase of the resistance for the perpendicular current and enables measurements of the perpendicular spin valve behavior at room temperature. The additional spacer layer of sputtered SiO2 with a contact hole of 5 μm diameter was fabricated with photolithographic method between the bottom Co and the intermediate Cu layer, which defined the current path perpendicular to the film plane. The measured magnetoresistance ratio was 0.85% (dR=7.6 mΩ, R=0.89 Ω) at room temperature.

Optical properties of thin films composed of complex hexaborides of rare-earth metals

The range of physical properties characteristic of hexaborides of rare-earth metals (REMs), connected with features of their chemical bonding, make these compounds promising as materials for optics and electronics. In particular, according to the data in, massive specimens of MeB{sub 6} can be used to create mirrors and optical filters. Technologies have been developed to obtain thin films of MeB{sub 6} by electron-beam and cathode sputtering of the corresponding compounds, which are then used to make vacuum condensates of congruently melting hexaborides of the cerium group and incongruently melting hexaborides of the yttrium group. As do massive materials, films exhibit selective reflection (and, accordingly, selective transmission), which is related to the resonance of free charge carriers in their plasmas. Here, the energy position of the resonance depends on the chemical composition of the material and the conditions under, which the condensate is obtained. Thus, by using different methods to obtain thin films and by varying process parameters such as condensation and annealing rates and temperatures, it is possible to change the energy position of the plasma extrema in their optical spectra. The high level of reflection of MeB{sub 6} films in the infrared region, the low level of transmission inmore » the ultraviolet region, and the extreme transmission and reflection in the visible region make it possible to use these coatings as selective optical filters.« less

Raman scattering from ion-implanted diamond, graphite, and polymers.

Raman scattering studies were carried out to investigate the effects of ion implantation on the structure of diamond, graphite, and polymers. Carbon phases produced by chemical vapor deposition (CVD diamond) and rf discharge (diamondlike carbon or DLC) were also analyzed. Two types of amorphous carbon phases were distinguished with relevance to hardness. In general, amorphous carbon phases produced by electron beam evaporation and sputtering are soft (hardness \ensuremath{\ll}1 GPa), while DLC and some ion-beam-modified polymers are much harder. In all cases, the characteristic Raman bands of the starting material were lost upon ion implantation, and for the lowest fluences the one-phonon bands near 1360 ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}1}$ (D line) and 1580 ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}1}$ (G line) of disordered polycrystalline graphite appeared. With increasing fluence these bands coalesced into a broad, asymmetric peak with the D line shifting to higher wave number and the G line shifting to lower wave number. This trend was clearly distinguishable from the finite crystallite size effect seen in graphite, where, in addition to the appearance of the D line, the G line shifts to higher wave number with decreasing crystallite sizes. Raman scattering could not distinguish between soft and hard amorphous carbon. There was also no indication that the hardness of DLC films and ion-beam-modified polymers was due to diamondlike ${\mathit{sp}}^{3}$ bonds. Instead, hardness in these materials is related to the three-dimensional interconnectivity of chemical bonds. Experimental results suggest that the amorphous carbons examined in this study are composed of random networks of distorted sp, ${\mathit{sp}}^{2}$, and ${\mathit{sp}}^{3}$ bonded atoms, sometimes in a hydrogenated state. The hard carbons such as DLC films and ion beam modified polymers have long-range chemical connectivity while the soft carbons such as damaged graphite, and carbon films prepared by sputter deposition lack such connectivity.

Corrosion-resistant amorphous surface alloys

This is a review of laser and electron beam processing and sputter deposition for the preparation of corrosion-resistant amorphous surface alloys and of the characteristics of thus prepared surface alloys. Amorphous surface alloys with a large surface area were prepared by repetition of instantaneous melting of a very restricted volume of the surface by irradiation with a CO 2 laser or electron beam and subsequent self quenching by the cold bulk substrates. The materials consisting of the amorphous surface alloys and bulk crystalline metals are quite suitable for corrosion-resistant materials with other specific properties. Sputter deposition was used for preparation of various amorphous alloys such as Al-Ti, Al-Zr, Al-Nb, Al-Ta, Al-Cr, Al-Mo, Al-W, Cr-Ti, Cr-Zr, Cr-Nb, Cr-Ta, Cu-Nb and Cu-Ta. The corrosion resistance of amorphous aluminum alloys was very high and could be changed from that comparable to 304 stainless steels to that far exceeding corrosion-resistant nickel-base alloys by changing the alloying element and its concentration. The corrosion rates of amorphous chomium-valve metal alloys are several orders of magnitude lower than those of alloy constituting elements. The amorphous Al-Mo alloys show high resistance to both sulfidation and oxidation at high temperatures. Sputter deposition is a potential method to produce new materials with specific properties.

Synthesis and Characterization of Zinc Sulfide Thin Films by Pyrolysis and Application to Thin Film Electroluminescence

Thermal decomposition of zinc 2-ethyl-hexanoate solution on glass substrates gave zinc oxide thin films. Zinc sulfide thin films were obtained by sulfidation of the zinc oxide films in a hydrogen sulfide atmosphere. The ZnS films were transparent, had a high degree of crystallinity with {111} preferred orientation, and the breakdown voltage of these films was about 28Vrms at a film thickness of 430nm (breakdown field was about 0.65MV/cm). The microstructure of the cross section of the ZnS thin films formed on a glass substrate was a particle-stacked structure, which is different from the columnar or conical grain structures obtainable by electron beam evaporation or sputtering. MIS (Metal/Insulator/Semiconductor)-type and sandwich (Metal/Insulator/Semiconductor/Insulator)-type thin film EL (electroluminescent) devices fabricated using the ZnS thin films showed EL emission above 100 ft-L at 130Vrms, 5kHz sine wave.

Low pressure magnetron sputtering using ionized, sputtered species

Abstract The possibility of a self-sustained magnetron sputtering process, without the presence of an inert gas, is demonstrated. The advantages of this process are as follows: the possibility of thin metal film deposition at very low pressures p ⩽ 4 × 10−4 Torr; a very high sputtering rate; an absence of inert gas particles in the deposited films; a possibility of deposition on substrates placed at a distance from the target much smaller than the mean free path; a decrease in the plasma discharge influence on substrate, the substrate can be placed at a greater than usual distance from the target. Low pressure magnetron sputtering using target ions opens new possibilities for thin film deposition. The method combines the advantages of both electron beam evaporation (purity, rate) and sputtering (good adhesion, repeatability, free choice of deposition geometry).

Oscillations of composition near the external surface of Y-Ba-Cu-O thin films

An Auger electron spectroscopy study has been made of the depth profiles of films of Y-Ba-Cu-O compounds. The films were produced by electron beam and ion plasma sputtering onto various substrate types. The specimens were annealed in air at temperatures ranging between 450 and 900 °C. The effective diffusion coefficients for the film and substrate constituents have been estimated. The depth profiles of films annealed at 600 °C reveal composition oscillations in the region adjacent to the surface. These composition oscillations are assumed to arise from the phase transformations that occur at 600 °C in films of the Y-Ba-Cu-O system.

Epitaxial Growth of NiSi2 and CoSi2 on Laterally Confined Silicon by Rapid Thermal Annealing

ABSTRACTEpitaxial growth of NiSi2 and CoSi2 on silicon inside miniature oxide openings by rapid thermal annealing has been studied. Effects of lateral confinement, including two-dimensional and linear oxide openings, as well as deposition methods on the growth of NiSi2 and CoSi2 on silicon were investigated. Vast difference found in the behaviors of the growth of epitaxy inside oxide openings between samples with the metal films deposited by electron beam evaporation and sputtering are attributed to the differences in the geometrical configuration of the films and stress levels as well as surface cleanliness.

Interfaces and solid state reactions of Zr/Fe multilayers

Metallic multilayers of Fe and Zr, prepared by electron-beam evaporation and sputter deposition, have been characterized by conversion electron Mossbauer spectroscopy and x-ray diffraction. Amorphous phase formation occurs at the interfaces during deposition for all samples and there is a critical layer thickness near 10 monolayers of each constituent where complete amorphization occurs. The amorphous phase formed upon annealing the 50 monolayer electron-beam sample consumes only about one-third of the Fe before the process saturates.