Papers

ICMCTF2001 Session B1-2: Sputtering Technique and Methodology

Monday, April 30, 2001 1:30 PM in Room Golden West

Monday Afternoon

Start	Invited?	Item
1:30 PM		B1-2-1 Growth and Characterization of Boron Carbide Nanostructured Coatings M.Y. Chen (Air Force Research Laboratory, Materials Directorate, USAF); R.Y. Lin (University of Cincinnati) Boron carbide in bulk ceramic or powder form has demonstrated extreme hardness and chemical inertness due to its covalent bonding. There is strong interest in boron carbide coatings for protective, wear, or corrosion resistance applications. However, the inherent brittleness of this material requires special designs of the coating nanostructure to achieve high fracture toughness. In this work, bilayers consisting of boron carbide and a metal (Mo or Ti) are deposited using d.c. magnetron sputtering with substrates held at ambient temperatures. Analytical techniques including x-ray photoelectron spectroscopy and standard x-ray diffraction analysis are used to determine the composition, chemical bonding, and phase structure of the nanostructured coatings. Overall film morphology is examined using SEM/EDS. Mechanical testing includes nanoindentation, scratch testing, and pin-on-disc tribotesting. The effects of bilayer material and individual layer thickness on film structure and mechanical properties will be presented.
1:50 PM		B1-2-2 The Role of Percolation for the Control of the Hardness in Super- and Ultrahard Nanocomposites A. Niederhofer, T. Bolom, P. Nesladek, K Moto, C. Eggs, S Veprek (Technical University Munich, Germany) In our earlier papers ^1-3 we have shown that under condition of plasma CVD with a low ion bombardment of the surface of growing film and increasing content of Si₃N₄ in the nc-M_nN/a-Si₃N₄ nanocomposites (M = Ti, W, V) the crystallite size passes a minimum and hardness (and elastic modulus) a maximum at a silicon nitride content corresponding the percolation threshold in a three dimensional network. This phenomena resulted in an apparent increase of the hardness (and elastic modulus) with decreasing crystallite size from 10 to 3 nm (see Fig. 8 in ²). More recently we found that if the surface of the growing film is heavily bombarded by energetic ions during the growth, as in the case of an abnormal D.C. glow discharge, the crystallite size is reduced due to the bombardment to about 4-2 nm and shows only a little dependence on the Si₃N₄ content. However, also in this case, the maximum hardness is achieved at Si₃N₄ content corresponding to the percolation threshold, when the thickness of the a-Si₃N₄ covering surfaces of the TiN nanocrystals corresponds to about one monolayer. In the ternary and quaternary nc-TiN/a-Si₃N₄/a- & nc-TiSi_x system which are deposited at a lower plasma density, the hardness reaches ≥ 40 GPa in a wide range of the composition but the ultrahardness of ≥ 80 GPa is achieved again when the surfaces of the nanocrystals are just covered by about one monolayer of Si₃N₄ although the crystallite size can vary between 4 and 11 nm. We shall summarize the experimental results and present their theoretical interpretation in terms of a stabilization of the nanostructure by decreasing the interface energy. ¹ ¹ S. Veprek and S. Reiprich, Thin Solid Films 268 (1995) 64 ² S. Veprek, M. Haussmann and S. Reiprich, J. Vac. Sci. Technol. A 14 (1996) 46 ³ S. Veprek, M. Haussmann and Li Shizhi, Electrochem. Soc. Proc. 96-5 (1996) 619
2:10 PM		B1-2-3 Multilayer Nitride Coatings by Closed Field Unbalanced Magnetron Sputter Ion Plating K.E. Cooke (Teer Coatings Ltd, United Kingdom); M. Bamber (UMIST, United Kingdom); J. Bassas (Univesitat Autonoma de Barcelona, Spain); D. Boscarino (Thin Films srl, Italy); B. Derby (UMIST, United Kingdom); A. Figueras (Univesitat Autonoma de Barcelona, Spain); B.J. Inkson (University of Oxford, United Kingdom); V. Rigato (Instituto Nazionale de Fisica Nucleare, Italy); T. Steer (University of Oxford, United Kingdom); D.G. Teer (Teer Coatings Ltd., United Kingdom) A range of ceramic multilayer nitride coatings, including Nb_xTi_yN, Nb_xZr_yN, and Mo_xZr_yN, has been successfully deposited onto tool and die steels by Closed Field Unbalanced Magnetron Sputter Ion Plating (CFUBMSIP). The mechanical properties of the resulting coatings, including adhesion and hardness, have been evaluated by micro- and nano-indentation techniques, scratch testing etc. Their detailed micro-structure, including their respective nm-scale multilayer repeat distance, λ, has been studied by advanced analytical techniques including High Resolution Transmission Electron Microscopy (HRTEM), Rutherford Back Scattering (RBS), and Glancing Angle X-ray Diffraction (GAXRD), etc. Focused Ion Beam (FIB) machining techniques have been developed to produce electron transparent coating cross-sections for analysis. The coating properties are reviewed and correlated with the analytical data. Potential applications for, and some limitations.
2:30 PM		B1-2-4 Enhancement of Aluminum Oxide PVD with a Secondary Plasma D.N. Ruzic (Univeristy of Illinois at Urbana-Champaign); N. Li, J.P. Allain, J.E. Norman (Univeristy of Illinois at Urbana Champaign) Reactive sputtering of aluminum oxide in a planar magnetron system is conducted with a mixture of O₂ and Ar and an aluminum target. The aluminum target is powered by a pulsed directed current (DC) bias which functions to discharge the accumulated ions on the insulating AlO_x film surface effectively during the positive duty cycle and suppress arc formation. A seven-turn helical antenna sits below the magnetron sputtering system in the vacuum system and delivers a radio-frequency (RF) power to generate a secondary plasma in the chamber. This plasma can efficiently ionize the sputtered flux, achieving ionized physical vapor deposition (IPVD). A gridded energy analyzer (GEA) and a quartz crystal microbalance (QCM) are located in the substrate plane to allow the ion and neutral deposition rates to be determined. Electron temperature and electron density are measured by a reciprocating Langmuir probe. A RF power of 500W significantly increases the deposition rate of AlO_x up to half of the Al deposition rate in metallic mode at the total pressure of 10mT. At 25mTorr, the ionization fraction of Al atoms reaches 90%. In addition, the desirable AlO_x film can be made at a lower O₂ partial pressure when the RF is on than when there is no RF. SEM photos show that the secondary RF plasma makes the films smoother and denser due to ion bombardment. The deposition rates and ionization fractions fluctuate as a function of O₂ partial pressure. These variations can be explained by the variation of the plasma parameters.
3:10 PM		B1-2-6 The Synthesis of Crystalline Alumina Thin Films at Low Temperature by Reactive Magnetron Sputtering J.L. Wang, I. Widlow, Y.-W. Chung (Northwestern University) Crystalline alumina thin films are known to have various excellent optical and tribological properties. They were generally grown by chemical vapor deposition, which requires ~1000 °C. This high temperature limits the application of alumina thin films only on specific substrates able to withstand such high substrate temperatures. In this paper, we grew crystalline alumina thin films at low substrate temperatures by reactive magnetron sputtering. A pulsed DC bias was applied to both the aluminum target and the substrate to maintain a stable deposition process and high deposition rate. An external solenoid coil was placed underneath the substrate to form a magnetic trap between the substrate and the target. Effects of substrate bias and magnetic trap on film properties were investigated. Under optimum conditions, crystalline alumina films were obtained at ~350 °C, with hardness ~20 GPa and refractive index ~1.68 in the visible region. Wear resistance and friction coefficients of both crystalline and amorphous alumina thin films were studied. Experimental techniques and further details will be discussed.
3:30 PM		B1-2-7 Role of Hydrogen Incorporation on the Structure and Mechanical Properties of Al_xO_yH_z Thin Films J.M. Schneider (Linköping Univeristy, Sweden); B. Hjörvarsson (KTH, Stockholm, Sweden); K. Larsson, J. Lu, E. Olsson (Uppsala Univeristy, Sweden); L. Hultman (Linköping University, Sweden) NOTE: PLEASE CHECK THE SECOND SENTENCE. I AM NOT SURE WHAT WAS SUPPOSE TO BE THERE. The role of the hydrogen concentration for the structure and mechanical properties of Al_xO_yH_z (0.32â‰¤xâ‰¤0.4; 0.54â‰¤yâ‰¤0.6; 0â‰¤zâ‰¤0.14) films as deposited by reactive magnetron sputtering in an Ar/O₂/H₂O discharge is discussed. As deposited films were studied by Rutherford-backscattering spectroscopy, nuclear resonance analysis, nanoidentation and electron microscopy. Experimentally and theoretically the mechanical properties were found to be a strong function of the hydrogen concentration. As the hydrogen concentration is increased from 0 to 13.8 at%, both, the elastic modulus values as well as the hardness values are reduced by approximately 50%. Based on the presented data the large scatter of mechanical propterty data reported in the literature for so called 'alumina' thin films can readily be understood.
3:50 PM		B1-2-8 Residual Stress Control of Magnetron Sputtered TiB₂ Coatings M. Berger, E. Coronel, S. Hogmark (Uppsala University, Sweden) TiB₂ is a hexagonal compound that has been attracting a growing interest as coating material due to many beneficial properties such as high hardness, high thermal and electrical conductivity and good chemical stability. Possible applications for this coating material include diffusion barrier in electrical contacts, wear protection on machining tools as well as extrusion dies. In this study the influence of process parameters on the structure and properties of d.c. magnetron sputtered TiB₂ coatings are evaluated. The main focus has been to develop a technique to control the residual stress level. A beam deflection technique was utilised for residual stress measurements. The coating structure was analysed by XRD and TEM. Mechanical properties such as hardness and Young's modulus were determined using nanoindentation. It is shown that by changing process parameters, i.e. changing growth kinetics, it is possible to control the residual stress level in these coatings.
4:10 PM		B1-2-9 Preparation of Amorphous SiC Films by Alternate Deposition of Si and C Thin Layers Using a Dual Magnetron Sputtering Source N. Kikuchi, E. Kusano, A. Kinbara (Kanazawa Institute of Technology, Japan) Amorphous silicon carbide (SiC) films have been prepared by alternately depositing thin Si and C layers on aluminosilicate glass substrate by magnetron sputtering. The apparatus used in the experiment was a dual-cathode sputtering machine with a carrousel type substrate holder. By rotating the substrate holder at a rotation rate of 30 rpm, a thin Si layer of <0.1 nm and a thin C layer of < 0.15 nm were alternately deposited on the substrate, depending on the cathode power. The C/Si compositional ratio of films deposited was controlled by changing flux ratio (layer thickness ratio) of Si and C. The composition, structure, and hardness of the deposited films were estimated as a function of source C/Si flux ratio. Results of X-ray photoelectron spectroscopy showed that the film composition changed Si:C=1:0 to 0:1 linearly with increasing C/Si ratio. The peak positions of Si2p and C1s shift also, showing the formation of Si-C bond in films. The X-ray diffraction measurements showed that films deposited were amorphous for all the composition. The maximum microhardness of about 30 GPa was obtained for a film deposited at a C/Si flux ratio of unity (for a film with C concentration of 47 at.%). This value was almost equal to that of a SiC film deposited from a SiC ceramics target by conventional rf sputtering. Internal stresses of films ranged from -0.5 to -1.0 GPa (compressive) and were 1/2 to 1/4 compared to that of the SiC film deposited from a SiC target by conventional sputtering without rotating substrate. The formation of an amorphous SiC film reveals that in the a dual-source alternate sputtering of Si and C, sputtered particles transferred energy enough to form Si-C bond in deposited film to the substrate.
4:30 PM		B1-2-10 Substrate Heating by Sputter-Deposition of AlN: The Effects of dc- and rf-Discharges for Nitrogen and Nitrogen-Argon Atmospheres T.P. Drüsedau, K. Koppenhagen (Otto-von-Guericke Universität Magdeburg, Germany) The power density at the substrate during sputter deposition of AlN was measured by a calorimetric method. Deposition was performed by either a dc-discharge in pure nitrogen atmosphere or a 13.56 MHz rf-discharge in nitrogen and argon-nitrogen atmosphere, respectively. The combination with measurements of the atomic deposition rate resulted in the determination of the total amount of the energy input per incorporated atom. For rf-discharges in N₂ atmosphere there is a monotonic increase of energy in put with increasing pressure and decreasing power. The energy input is in the range between 0.4 and 15.7 keV per atom. For dc-discharges, the energy flux is (under identical conditions) significant smaller and in the range between 270 and 720 eV. At the metallic / reactive sputtering transition in low-pressure argon-nitrogen mixtures (rf-discharge), the energy input increases from 40 eV for under-stoichiometric AlN to 400 eV for stoichiometric films. The hypothetical bombardment of a metallic and nitrogenated target by nitrogen ions was simulated by TRIM.SP and TRIDYN Monte-Carlo calculations. The resulting sputtering yields, reflection coefficients and average energies of sputtered atoms and reflected nitrogen-neutrals are discussed. The calculations indicate the strong effect of reflected nitrogen, but cannot account for the high experimental values of energy input. It is argued that the contributions of charged particles and AlN dimers are the origin of the discrepancy.
4:50 PM		B1-2-11 Improvement of the Corrosion Resistance of Hard Wear Resistant Coatings by Intermediate Plasma Etching and/or Multilayered Structure M. Balzer, H.A. Jehn, H. Kappl (Forschungsinstitut für Edelmetalle und Metallchemie, Germany); J.-J. Lee, K.H. Lee, H.-S. Park (Seoul National University, Korea); M. Fenker (Forschungsinstitut für Edelmetalle und Metallchemie, Germany) PVD hard coatings can be a serious alternative to electrochemical deposited coatings, if they are dense and without pores. This study is part of a series of experiments with the aim to deposit thin films onto high speed steel by magnetron sputtering which possess a high corrosion resistance. Two different ways were chosen: 1.) deposition of single layers (CrN, NbN) and 2.) deposition of multilayer films (Cr/CrN, NbN/CrN). Additionally the effect of intermediate plasma etching was studied for these coating systems. That means for single layer systems, that the film growth was stopped several times and the as-grown film was exposed to an ion bombardment. For multilayer systems the intermediate plasma etching was applied between the different layers. It is assumed that the plasma etching of the film leads to a denser coating, due to defect-induced renucleation and improved adatom mobility. The corrosion resistance of the coatings was studied by potentiodynamic and potentiostatic corrosion tests in sodium chloride solution. Further film properties were investigated by SEM, XRD, TEM, AES, Scratch testing and microhardness measurements. The results reveal that intermediate etching improves the corrosion resistance of single layers, whereas for the multilayered coatings no or nearly no positive effect could be observed.