ICMCTF2005 Session B1-1: Sputtering Coatings and Technologies

Thursday, May 5, 2005 8:30 AM in Room Golden West

Thursday Morning

Start	Invited?	Item
8:30 AM	Invited	B1-1-1 Measuring the Plasma Characteristics in Pulsed DC Magnetron Sputtering Discharges J.W. Bradley (University of Liverpool, United Kingdom) Asymmetric bi-polar DC magnetron pulsing [1] has become an important technique in the reactive sputter-deposition of high quality dielectric thin films and coatings [2]. In this technique, the magnetron cathode voltage is typically modulated between 20 and 350 kHz with duty cycles ranging from 50-90 %. To understand better these complicated plasmas, investigators are employing a number of diagnostic techniques to determine the temporal evolution of the plasma parameters and their effect on the growing film at the substrate. Here, these techniques are reviewed and the latest results from the community presented. The techniques include: the development of emissive probes to determine the temporal and spatial evolution of plasma potential; the use of cylindrical and planar Langmuir probes to measure the electron temperature and density; time and energy-resolved mass spectroscopic measurements of the important ionic and neutral species at the substrate; and optical emission spectroscopy to determine the presence and energies of electrons and excited species in the plasma. A discussion of future opportunities in research on pulsed magnetron discharges is given. [1] RA Scholl, Surf. Coat Technol. 98 (1998) 823 [2] PJ Kelly and RD Arnell, J. Vac. Sci. Technol. A 17 (3) (1999) 945.
9:10 AM		B1-1-3 Cathode Current Distributions in Unbalanced Magnetrons G.C.B. Clarke, P.J. Kelly (University of Salford, United Kingdom); J.W. Bradley (University of Liverpool, United Kingdom) The planar magnetron is extensively used as a sputtering source for a wide variety of target materials. Unfortunately, in some configurations, the target may have to be replaced when as little as 30% of its material had been sputtered. This is due to the non-uniform distribution of bombarding ions across the face of the target, which leads to the formation of erosion profile that peaks beneath the racetrack. A better understanding of this process could lead to number of benefits including improved target utilization in sputtering processes. The arrival of ions and the emission of electrons from a target can be measured as a current, and it is the variation of this current with position that is the focus of this paper. To measure how the current varies two different probes have been constructed, to suit rectangular and cylindrical geometry unbalanced magnetrons, respectively. The probes consist of grids of detectors positioned across the full racetrack regions of the targets, and mounted flush with their surfaces. The targets were sputtered in DC and pulsed DC modes and the current at each detector position across the target was monitored under a series of operating conditions. The results presented here show how the current distribution varies under different conditions whilst operating in both modes, and also how the current distribution evolves with time whilst pulsing.
9:30 AM		B1-1-4 Influence of the Target Temperature on the Sputtering Mode Stability for Reactive Deposition of Oxides and Nitrides D. Mercs (Laboratoire d'Etudes et de recherche des matériaux. Les procédés et les surfaces (UTBM-LERMPS), France); A. Billard (École des Mines Parc de Saurupt, France) Reactive magnetron sputtering is a commonly used technique to synthesise high quality metallic or ceramic coatings. In the case of industrial plants, the relative large area of the chamber walls regarding with the suction capacity of the pumping system often produces an unstable behaviour which constitutes the major drawback of the technique; stoichiometric coating are usually synthesised in the reactive sputtering mode, i.e. with a very low deposition rate, whereas coatings sputter-deposited in the elemental sputtering mode are often sub-stoichiometric. In previous papers, we pointed out the beneficial effect of increasing the temperature of a titanium target sputtered in argon-nitrogen or argon-oxygen reactive mixtures, on the stabilisation of the sputtering mode [1]. In this paper, we present complementary investigations resulting from the sputtering of titanium and zirconium targets at different temperatures in reactive argon-nitrogen and argon-oxygen mixtures. After a short description of the target shapes specifically designed to control their temperature, we show that increasing the target temperature is able to allow the perfect stabilisation of the sputtering mode, and hence, the high-rate deposition of stoichiometric titanium or zirconium oxides or nitrides. Finally, the origin of the process stabilisation is discussed in relation with the help of a model taking into account the metalloid diffusion into the target. [1] A. Billard, D. Mercs, F. Perry, C. Frantz, Surf. Coat. Technol., 116/119 (1999), 721.
9:50 AM		B1-1-5 Optical Emission Spectroscopy in an Inverted Cylindrical Magnetron Plasma A.D. Srivastava, A. Khanna, D.G. Bhat, M.H. Gordon (University of Arkansas) In the present research project the authors aim to develop a PVD process methodology for growing crystalline alumina coatings using a novel inverted cylindrical magnetron sputtering system. This ICM technique offers the advantage of very high deposition rates and has the potential for scale-up of deposition recipes for alumina films for applications in the cutting tool industry. An understanding of both the plasma environment and the plasma-surface interactions is critical for this project's success. In this paper we present the preliminary spectroscopic results obtained for both a Ti-Ar-N and an Al-Ar-O plasma. Our first emission scans were acquired from 4000-8200 Å, for conditions used to deposit TiN. The total pressure was 2 mTorr, power supplied was 8 kW, argon flow was 85 sccm, and nitrogen flow was 13 sccm. A two-lens optical system imaged the plasma onto the entrance slit of a 0.5m monochromator. Signal amplification was accomplished using a Hamamatsu PMT. The spectral response of the system was calibrated using a quartz-halogen tungsten lamp whose operating temperature was measured with a Pyro-micro disappearing filament optical pyrometer. Results indicate a Boltzmann temperature of about 4000 K using the spectroscopic data for the Ar emission lines at 751.4 nm and 811.5 nm. The uncertainty, however, is high because the two states are only 0.2eV apart in energy, but this value is considerably lower than the average electron energy of the plasma (typically in the 1-2 eV range 11,000-22,000 K). This discrepancy is not surprising at the low operating pressure (2 m Torr) where the mean free path is on the order of 5 cm such that there are relatively few collisions. Thus, the supplied power which is directly coupled to the charged particles (primarily the electrons) is not efficiently transferred to the neutral species, such as argon. In the final paper, we will also present data obtained from on-going experiments involving an Al-Ar-O plasma.
10:10 AM		B1-1-6 Magnetron Rod Cathode for Inner Cylinder Coatings F. Löffler (Pysikalisch-Technische Bundesanstalt, Germany) Large numbers of applications require coatings on inner surfaces of components. Examples are the inner cylinders of engines and inner surfaces of bearings or other cylindrical tubes. For special sensors, e. g. acceleration measuring sensors or magnetic bearings, an electric conductivity has to be realized with an inner coating. Most of the applications need a coating with a high homogeneity and an even thickness distribution of the inner surfaces without a significant heat up during coating process. This requires sputtering processes for the inner coatings. The realization of homogeneous coatings inside small cylindrical parts, e.g. 10 mm in diameter, can be achieved by diode sputtering. Due to the higher quality of coatings applying a magnetron during the sputtering process, this investigation discusses the possibilities of this method. The present study describes a sputter cathode system using an inner magnetron for the rod cathodes. The study uses cathodes with a diameter between 4 mm and 12 mm. Cylindrical substrates with an inner diameter of 10 mm up to 30 mm are made of an aluminium alloy. Theoretical considerations, set up and realization of the experiment as well as the coating characterization are content of the paper.
10:30 AM		B1-1-7 Growth Mechanisms and Corrosion Characteristics of Magnetron Sputtered Cr Films R. Wei, K.-T. Chiang, J. Dante, E. Langa, C. Rincon, J. Arps (Southwest Research Institute) Chromium films are commonly used as corrosion resistant coatings. Their microstructure is an important aspect in corrosion resistance. In this work, we have studied the growth mechanisms of these films to gain insight of the microstructural properties on corrosion resistance. Films of Cr have been deposited on silicon wafer, copper and steel substrates using a plasma-enhanced magnetron sputtering technique. The film growth, morphology, and microstructure are correlated with the sample orientation (with respect to the magnetron) and more importantly the plasma bombardment. It has been found that at a low ion bombardment, a loose columnar structure is observed and the film is dis-contiguous. As the ion bombardment increases, the film becomes denser and contiguous. Eventually the columnar structure disappears and the film is near featureless. The corrosion behaviors of the deposited coatings are studied using electrochemical techniques. The coatings are also tested at elevated temperatures to determine high temperature corrosion resistance. It has demonstrated that adequate ion bombardment is necessary to achieve the required corrosion resistance. In this paper, we will present the data obtained from the SEM, XRD, and AFM studies and the corrosion tests.
10:50 AM		B1-1-8 Fabrication and Characterization of Non-Evaporable Porous Getter Films C.-C. Li, J.-L. Huang (National Cheng-Kung University, Taiwan); R.-J. Lin (Industrial Technology Research Institute, Taiwan) The getter materials (titanium or titanium alloys) are widely used in vacuum-type devices to upgrade and sustain the vacuum environment inside the cavity of the device by the chemical interaction between getters and gases. The common shape of the getters is a pellet or sheet. These getters can not be applied in the minimizing vacuum devices, such as high Q mechanical resonator, infrared detector of focal plane array or tunneling sensors, etc. due to their limited space. With the progress of MEMS (microelectromechanical system) technologies, the minimizing vacuum devices have being increased. Therefore, the development of the non-evaporable thin-film-type getters (< 2 µm in thickness) is necessary. The porous film is much better for increasing the surface area. The porous titanium (Ti) getter films have been successfully grown on silicon wafer by the magnetron sputtering method with controlling the incident angle of sputtering flux onto the substrate. The film thickness is 0.5-1µm. The columnar grain size of the porous Ti film is 28-33 nm, which is related to the incident angle and sputtering power. The inter-distance between the columns is about 10-30 nm. The analysis of gases absorption of porous Ti films shows that the partial pressure of H₂O, CO, O₂ and CO₂ gases is rapidly reduced at 300 °C by the thermal desorption spectroscopy (TDS). This means that the activation temperature of the porous Ti film getters can be 300 °C. The gases absorption characteristic of porous Ti films is much more effective than that of non-porous films. The detailed discussion of the relationship between the microstructure, crystal structure (texture orientation), specific surface area of the porous Ti film and the deposition parameters, and the capability for gettering the atmosphere gases will be presented.
11:10 AM		B1-1-9 W-Fe Alloy Nanolayer Growth by Magnetron Co-Sputtering P. Plantin, P. Brault, A.-L. Thomann (Universite d'Orleans-CNRS, France); Th. Sauvage (CERI CNRS Orleans, France); P.-O. Renault, D. Faurie, P. Goudeau, E. Le Bourhis (LMP CNRS - Universite Poitiers, France) A multitarget magnetron sputtering system has been built for studying and comparing growth of metallic multilayers and alloys. We have studied the thin film growth of W-Fe alloys deposited on Fe by the co-sputtering. The composition and organization of the films are examined by Rutherford Backscattering Spectrometry. The figure below displays the RBS spectrum of a 200 nm coating of W-Fe on a Fe substrate previously coated 400 nm W films. On both W and Fe components, an oscillatory behavior appears. This is consistent with a 200 nm thickness coating formed by 10 layers (20 nm each) with alternate composition W0.7Fe0.3 and W0.4Fe0.6. This oscillatory behavior appears spontaneously at small thicknesses and is not observed any more above 500 nm. A detailed study of this kind of self organization at the nanometer scale will be presented. Influence of self-organization on the mechanical properties (hardness, elastic response) will be reported.
11:30 AM		B1-1-10 Pulsed Power MagnetronSputtering of a Niobium Target in Reactive Oxygen and/or Nitrogen Atmosphere M. Fenker, R. Bretzler, H. Kappl, K. Petrikowski (FEM, Schwäbisch Gmünd, Germany) The behavior of a niobium target during magnetron sputtering in reactive nitrogen and/or oxygen atmosphere using a pulsed power supply has been investigated. It was found that the cathode voltage was strongly influenced by pulse width and pulse frequency in the studied range (500 - 4000 ns and 50 - 250 kHz, respectively). The cathode voltage decreased with increasing pulse width and increasing pulse frequency for about 100 - 400 V, depending on the sputtering parameters. No arcing was observed at any deposition conditions. Deposition rates in the system Nb-O-N were in the range of 0.8 - 3.6 µm/h. The highest rates were found for low oxygen flows in the Nb-O system. The chemical composition and the crystallographic structure of the deposited Nb-O, Nb-N and Nb-O-N coatings have been studied by energy dispersive X-ray spectroscopy (EDX) and X-ray diffraction (XRD), respectively. Hardness measurements were performed using the instrumented indentation test. As for other Me-O-N systems (Me = metal) the oxygen has a strong influence on the chemical composition of the Nb oxynitride coatings due to the higher reactivity compared with nitrogen. Nb-O coatings deposited at oxygen gas flows > 5 sccm look transparent, at lower oxygen gas flows the coatings appear metallic. Oxygen gas flows > 5 sccm do not influence the chemical composition or hardness of the coatings appreciable (saturation effect). Addition of nitrogen shift the transition "metallic-transparent" to lower oxygen gas flows. Nb-O coatings seem to be X-ray amorphous. The hardness of the transparent Nb-O-N coatings is lower than the hardness of pure niobium.
11:50 AM		B1-1-11 Nanostructured Nitride Films of Multi-Element High-Entropy Alloys by Reactive DC Sputtering T.K. Chen (National Dong Hwa University, Taiwan); T.T. Shun (Industrial Technology Research Institute, Taiwan); J.W. Yeh (National Tsing Hua University, Taiwan); M.S. Wong (National Dong Hwa University, Taiwan) Multi-element high-entropy alloys are alloy systems with over five principal elements each having an atomic percentage no more than 35%. The novel alloys possess unique crystallographic, mechanical, thermal, and chemical properties. Using the alloys, e.g. FeCoNiCrCuAl_0.5 and FeCoNiCrCuAl₂, as target materials in reactive sputtering, nanostructured nitride films were deposited. XRD patterns show that the alloy films are crystalline with structures of simple fcc or bcc solid solution, while the crystallinity decreased and approached amorphous with increasing nitrogen flow rate into the processing chamber. Detailed nanostructures of the nitride films are characterized by TEM. Their mechanical properties are also determined and compared.
12:10 PM		B1-1-12 Tailoring of Wear-Resistant Coatings on H-13 Tool Steel Produced by PVD A. Rojo (ITESM-TOL, Mexico); J. Oseguera, O. Salas (ITESM, Mexico) Wear-resistance coatings on a H-13 tool steel are commonly used to improve tribomechanical properties. Physical vapor deposition (PVD) process with non balanced magnetrons was used to produce transition metal nitride layers of CrN and AlN on plasma nitrided H-13 steel substrates. Plasma spectral lines, identified by optical emission spectroscopy (OES) and electron density by a Langmuir probe, were linked to process parameters and to the structural characterization of the layers obtained. important parameters to tailor the layers. The results of the analysis were central to establish the elements to be considered to tailoring these deposits.