Papers

ICMCTF2004 Session B1: Sputtered Coatings and Technologies

Thursday, April 22, 2004 8:30 AM in Room Golden West

Thursday Morning

Start	Invited?	Item
8:30 AM		B1-1 Recent Developments in Pulsed Magnetron Sputtering R.D. Arnell, P.J. Kelly (University of Salford, United Kingdom); J.W. Bradley (Umist, United Kingdom) In magnetron sputtering, coating properties are largely determined by the rate at which energy is delivered to the growing film through simultaneous ion bombardment. The structure and properties depend on three parameters: the homologous temperature; the ratio of the fluxes of bombarding ions and depositing atoms; and the energy of the bombarding ions. It is shown here that pulsing the target voltage can strongly influence these intrinsic parameters and can cause much greater energy fluxes to be delivered to the substrate than in DC systems operating at the same input power. Time averaged Langmuir probe measurements have shown that electron temperatures, ion and electron densities and ion fluxes to the substrate all increase with increasing pulse frequency, and that a burst of "hot" electrons is associated with the fast negative voltage transient between "reverse" and "on" phases of the target voltage It is shown that the energies of the ions arriving at the substrate are influenced by both the reverse time/duty factor and the pulse frequency, and that that these energy variations have very significant effects on coating structure and properties. The effects of applying mid-frequency (100 - 350kHz) pulsed dc power at the substrate have also been studied. It has been found that, unlike the dc case, if the bias is pulsed in this range, the current drawn at the substrate does not saturate, but continues to increase with increasing bias voltage. In addition, this effect becomes more marked as the pulse frequency is increased. Pulsing the substrate bias voltage, therefore, offers a novel means of controlling the ion current drawn at the substrate. Clearly, this has significant implications in relation to film growth, sputter cleaning, and substrate preheating processes.
9:10 AM		B1-3 A Simplified Treatment of Target Implantation Effects in Reactive Sputtering T. Nyberg, D. Rosen, I. Katardjiev, S. Berg (Uppsala University, Sweden) It is well known that a compound layer may form at the target surface during reactive sputtering. The only mechanism that is taken into account for the formation of the compound layer in previous standard models for the reactive sputtering process, is chemisorption at the target surface. This is a sufficiently good approximation when the partial pressures of the reactive gas is relatively low and when the sticking coefficient of the reactive gas is sufficiently high. At high partial pressures of the reactive gas however, a significant fraction of the ion current is carried by reactive gas ions, resulting in a direct implantation of rective gas species into the target. Moreover, there is a high probability that incoming ions may knock chemisorped ractive species at the surface, into the target. If the sticking coefficient is small enough, these implantation effects may be the major mechanisms responsible for the formation of the compound layer at the target. We present an extension of the basic reactive sputtering model that takes these implantation effects into account. From this model it is possible to examine the behaviour of the reactive sputtering process at high reactive gas pressures and/or weakly reactive systems. Results from simulations will be presented and compared with relevant experimental observations to illustrate the capabilities of the improved model.
9:30 AM		B1-4 Plasma Diagnostical Comparison of the MSIP Process of (Ti,Al)N with Pulsed and DC Power Supplies using Energy Resolved Mass Spectroscopy E. Lugscheider, N. Papenfuss-Janzen (RWTH Aachen University, Germany); R. Cremer, G. Erkens, S. Rambadt (CemeCon AG, Germany) Plasma diagnostics by energy resolved mass spectroscopy is a well known method to understand and control rf-plasmas, e.g. during plasma etching, and in PECVD processes. Only very few scientific work concentrates on the investigation of the MSIP process. This is the reason why, so far, this process is not very well understood. A technology that is gaining increasing importance within the last decade is the use of pulsed power supplies. On the one hand, this technology allows the sputtering of insulating coatings with a significantly higher sputtering rate than with rf-plasma. On the other hand, the degree of ionization is higher than in dc-processes. In this article, the ion energy distribution of aluminum and titanium as well as titanium nitride is observed by using different types of pulsed cathode power supplies and a dc power supply. The different behavior of the ion energy distributions depending on the power supplies is shown. The cathode power and the nitrogen flow are the observed varying process parameters.
9:50 AM		B1-5 Erosion Resistant Properties of Magnetron Sputtering Deposited Ti_1-xAl_xN_y Coatings Q. Yang, D.Y. Seo, L.R. Zhao (National Research Council, Canada) The excellent wear- and oxidation-resistant properties render TiAlN as a suitable protective coating for high-speed cutting and drilling tools. While most of attentions have been drawn to its remarkable anti-wear behavior, less effort has been made to explore the potentials of TiAlN coatings for erosion protection application. In this study, Ti_1-xAl_xN_y coatings were deposited by a magnetron sputtering technique, and subsequently characterized by SEM, XRD and nano-hardness testing. The erosion resistant properties of Ti_1-xAl_xN_y coatings were evaluated under solid particle impact testing with different particle impingement angles and speeds. The Ti_1-xAl_xN_y coatings exhibited superior resistance to high-speed hard particle impingement, with erosion rates several times lower than those of TiN coatings deposited under similar process conditions. The substrate bias voltage applied during deposition had an appreciable effect on the erosion behavior of the coatings, and underlying mechanisms were analyzed in terms of the microstructure and internal stress.
10:10 AM		B1-6 Deposition of CrN-MoS₂ Thin Films by D. C. Magnetron Sputtering S.K. Kim, B.C. Cha (University of Ulsan, South Korea) Deposition of CrN-MoS₂ composite thin films on the SKD11 tool steel by D. C. magnetron sputtering was studied. The influence of the N₂/Ar gas ratio, the deposition temperature, the current ratio of MoS₂ over Ti and the thickness of chromium interlayer on the structure, hardness and adhesion of the composite films were investigated. The hardness of the films increased with the increase of the N₂/Ar gas ratio and the deposition temperature. The surface morphology changed from tapered crystallites to dome structure with the increase of the current ratio of MoS₂ over Ti. Adhesion of the film increased with the increase of chromium interlayer thickness within the range studied.
10:30 AM		B1-7 Elaboration and Characterization of Thin Films of ZrBN Deposited by Triode PVD Prossec A. Chala (Labomap - Ensam, France); A. Djouadi (Institut des Materiaux Jean Rouxel, France); C. Siad (Universite de Biskra, France); C. Nouveau (Labomap - Ensam, France); S. Aida (Constantine University, France) The efficiency of hard coating, as ZrBN, in increasing abrasive resistance is studied in this paper. the aim of this study is to optimize the duplex treatments by modifying the nitriding gas mixture in high temperature process and time (from 2 to 8 hours). the influence of gas (composed of N₂, H₂ and CH₄) on the mechanical properties of low alloy steel samples was studied. the composition and structure of nitriding layers were determined by XRD and EDS. Vickers microhardness profiles were also performed to study the influence of the gas mixture. The morphology of the nitriding layers was observed by by optical microscopy. ZrBN coatings have been realized by triode sputtering on both silicon and steel substrates. The EDS analyses permitted to verify the composition while their structure was determined by the XRD. different kinds of samples are tested: non treated, nitrided, ZrBN-triode sputtered and ZrBN-duplex treated. It was obvious that increasing the nitrogen contents from 20% to 80% in the nitriding gas mixture N₂ + H₂ or adding only 5% of CH4 permit to increase the nitrided layer thickness and hardness. This result was also obtained by increasing time from 2 to 8 hours. The duplex treated samples obtained with 80% of N₂ or 5% of CH4 performed best and allowed to increase the service life.
10:50 AM		B1-8 Zirconia-metal Oxide Nanolaminate Films C.R. Aita (Advanced Coatings Experimental Laboratory) The growth and unique properties of sputter-deposited zirconia-metal oxide nanolaminate films are reviewed here, using three model systems: zirconia-alumina, zirconia-yttria, and zirconia-titania. Each system represents a different type of interfacial behavior and cation mixing. The talk will emphasize how zirconia-based nanolaminate structures are used to produce coatings with tailorable physiochemical properties, with specific examples of corrosion-resistant, mechanical, and optical behavior not achievable in single-layer films. Support under NSF Grant No. CMS-9988892 is acknowledged.
11:30 AM		B1-10 Pvd-Al₂o₃ Coated Cemented Carbide Cutting Tools T. Selinder, M. Astrand (AB Sandvik Coromant, Sweden); F. Fietzke, H. Klostermann (Fraunhofer-Institut fur Elektronenstrahl- und Plasmatechnik FEP, Germany) With the invention of the bipolar pulsed DMS technique (Dual Magnetron Sputtering) a wide range of opportunities has opened up for the deposition of insulating layers such as Al₂O₃ as well as for non-insulating compound layers such as Ti_xAl_1-xN. In the pulsed DMS, the two magnetrons alternately act as a cathode and an anode and, hence, preserve a metallic anode over long process times. At high enough frequencies, 25-50 kHz, possible electron charging on the insulating layers will be suppressed and the otherwise troublesome phenomenon of arcing will be limited. Furthermore, the DMS method has made it possible to deposit hard (>20 GPa) nanocrystalline, gamma-Al₂O₃, strongly textured in the (440)-direction, at substrate temperatures as low as 600 C which is a much lower temperature than the conventional CVD-temperatures, 1000-1050°C, for the deposition of the alumina polymorphs alfa and kappa. For conducting compound layers such as TixAl1-xN the DMS technique makes it possible to vary the metal ratio Ti/Al over wide ranges by changing the the duty cycle (pulse durations) for the sputtering of Ti and Al. PVD coated cemented carbide cutting tools coated with a double layer of gamma-Al₂O₃ and TiAlN or TiN have been evaluated in a number of cutting operations such as parting/grooving, threading and end-milling. The addition of a 2 micrometer thick gamma-Al₂O₃ layer improves the surface finish of the workpiece material simultaneously as the BUE-formation on the tool edge is reduced. The effect of the gamma-Al₂O₃ layer as a thermal barrier, i.e. preventing heat from flowing from the rake face into the cutting edge causing plastic deformation of the cemented carbide, is clearly demonstrated in a grooving operation in austenitic stainless steel. The gamma-Al₂O₃/TiAlN(TiN) coated inserts exhibit tool lifes considerably longer than the single-coated inserts at higher cutting speeds when plastic deformation of a non-Al₂O₃ coated cutting edge causes the coating to spall off.
11:50 AM		B1-11 Deposition of α-Alumina Hard Coatings by Reactive Magnetron Sputtering T. Kohara, H. Tamagaki, Y. Ikari, H. Fujii, K. Yamamoto (Kobe Steel, Ltd., Japan) Alumina as top-coat of hard coatings is considered as the suitable material for oxidation-resistance and heat-resistance layer for cutting tools. Particularly, α-alumina with the corundum structure is considered as the best because of its higher thermal stability than any other crystal structures of alumina. However, such film can be commercially deposited only by CVD at temperature above 1000°C. In this work, the deposition of crystalline PVD-Alumina at lower temperature on cemented carbide substrates by a reactive magnetron sputtering was reported. The films were deposited from the metallic aluminum targets in argon-oxygen gas mixture at the substrate temperature from 600°C to 750°C in a production scale PVD system. The sputter process was controlled in the transition mode by combining a discharge voltage control and an optical emission feedback to obtain stoichiometric films at reasonable rate. The deposition rate as high as 0.7µm/hr was achieved. The α-Al₂O₃ films on CrN films and TiAlN films on the cemented carbide substrates were deposited by optimizing the film structure and the process condition. The deposited films were characterized by hardness and adhesion, and the crystal structure were examined by XRD. SEM was used to investigate the morphology of the α-Al₂O₃ films. The cross-sections of the films were investigated in TEM.
12:10 PM		B1-12 Nanostructured Nitride Films of Multi-element High-entropy Alloys by Reactive Sputtering T.K. Chen, M.S. Wong (National Dong Hwa University, Taiwan, R.O.C.); T.T. Shun (Industrial Technology Research Institute, Taiwan, R.O.C.); J.W. Yeh (National Tsing Hua University, Taiwan, R.O.C.) Multi-element high-entropy alloys are alloy systems with n (5≤n≤13) principal elements each having an atomic percentage no more than 35%. The novel alloys possess unique mechanical, thermal, and chemical properties. Using the alloys as target materials in reactive sputtering, nanostructured nitride films were deposited. Two high-entropy alloys of FeCoNiCrCuAl and FeCoNiCrCuAl₂ were used. Various characterization techniques were used to measure morphology, phase structure, crystallinity, mechanical, electrical, and tribological properties of the films. The films are extremely smooth. The nitrogen content of the films increases but the film deposition rate decreases with increasing nitrogen flow rate. The values of resistivity of the two alloy films are 135 and 108µΩ-cm, respectively and of their nitride films increases with nitrogen content. The crystallinity of the films decreases but their hardness increases with increasing both nitrogen flow rate and substrate bias.