Hybrid PVD Techniques and Coatings

Tuesday, April 11, 2000 8:30 AM in Room Golden West

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8:30 AM B1-3-1 Recent Progress in Large Scale Manufacturing of Multilayer/Superlattice Hard Coatings
P.Eh. Hovsepian, D.B. Lewis, W.-D. Münz (Sheffield Hallam University, United Kingdom)
Since the early fundamental research on superlattice structured hard coatings in the late 1980@super ,@s, rapid progress has been achieved to produce nanoscale compositionally modulated multilayer structures. It has been shown that the periodicity of the multilayers is strongly controlled by the substrate rotation and the actual deposition rate. Appropriate multi-target geometry and controlled target poisoning by optimised pumping conditions lead to deposition conditions similar in its economy to the deposition of typical monolithically grown binary hard coatings. The combined steered cathodic arc/unbalanced magnetron technology guaranties sufficient adhesion (Lc@>@50N) of the usually highly stressed coatings as well as smooth surfaces due to UBM deposition (Ra @ < @ 0.04 @ micron @).@paragraph@The paper describes the properties of coatings dedicated to high temperature performance: TiAlN/CrN (period 3.8nm), to tribological applications: TiAlYN/VN (period 3.0 nm) and combined wear and corrosion resistance CrN/NbN (period 3.4nm). All the coatings investigated were found to crystallise into B1 NaCl f. c. c. structure and exhibit {111} or {200} preferred orientation for TiAlN/CrN, TiAlYN/VN and CrN/NbN superlattice coatings respectively. The residual stress has been found to be compressive in the range of 4.0 GPa for TiAlYN/VN and between 1.5 GPa to 7.5 GPa for CrN/NbN depending on the stoichiometry and the bias voltage during coating deposition. Corresponding to the high stress values the plastic hardness of the coatings was measured to be 40 GPa for TiAlN/CrN, 60 GPa for TiAlYN/VN system and between 40 GPa and 70 GPa for CrN/NbN depending on the bias voltage. Oxidation temperatures exceeding 900 @super 0 @C have been typical for TiAlN/CrN. The TiAlYN/VN showed superior tribological properties with coefficient of friction f@=@0.4 and low sliding wear of 1.26 x 10@super-17@ m@super 2@N@super-1@ after 1.1 million cycles against Al@sub 2@O@sub 3@ ball in pin-on-disc test. CrN/NbN exhibit two orders of magnitude lower passive current densities than electroplated hard Cr and pitting potential of 450 mV during polarisation in acetate buffer solution. When Nb@super + @ ion etch was used CrN/NbN superlattice coating deposited on 304L stainless steel showed high pitting potentials in the range of 750 mV to 1000 mV in the same corrosive media.
9:10 AM B1-3-3 Low-temperature Magnetron Sputter-deposition, Hardness and Electrical Resistivity of Amorphous and Crystalline Alumina Thin Films
Q.L Li (Northwestern University); Y.H. Yu (Tatung University, Republic of China); C.S. Bhatia (IBM); S.C. Lee (Tatung University, Republic of China); L.D. Marks, Y.W. Chung (Northwestern University)
Aluminum oxide films were grown by reactive magnetron sputtering. In order to maintain a stable deposition process and high deposition rate, pulsed dc bias was applied to the aluminum target and the substrate. An external solenoid was used to form a magnetic trap between the target and the substrate. The influence of substrate temperature, substrate bias and the magnetic trap on film growth and properties was studied by different surface and thin-film analysis techniques and electrical measurements. Normally, amorphous alumina films were produced. However, under optimum process conditions, crystalline alumina films can be obtained at temperatures as low as 250C, with hardness @~@ 20 GPa and excellent electrical properties.
9:30 AM B1-3-4 About the Characterization of Oxides and Oxide Containing Hard Coatings Deposited by High Ion Sputtering (H.I.S.) Process Technique
G. Erkens, T. Leyendecker, R. Wenke, H.-G. Fuss (CemeCon GmbH, Germany); I. Rass, M. Feldhege (Euromat, Germany); R. Cremer (RWTH Aachen LTH, Germany)
Innovative cutting operations as dry cutting, high speed cutting and hard cutting focus on metastabile coatings. To improve the performance of such films high hardness corresponding with low Youngs modulus and oxide creating elements inside the films are required. These requirements are met by the tenary coating system (Ti,Al)N. For high ion sputtered (H.I.S.-process) (Ti,Al)N, crystalline alumina is created in the subsurface area at elevated temperature. Results from oxidation tests will show the crystalline character of the toplayer that is built continuously during the cutting process. It is illustrated whether the addition of oxygen to deposite Ti-Al-O-N could enhance the formation of crystalline alumina besides the improvement of the oxidation resistance. Thermal stability is also a criteria that should be met by coating systems for innovative cutting operations. In this connection stabilized ZrO@sub 2@ is well known from other applications. ZrO@sub 2@ layers were deposited in combination with (Ti,Al)N as multilayers with the r.f.-High Ion Sputtering (r.f.-H.I.S.) process module following the (Ti,Al)N/Al@sub 2@O@sub3@ deposition. The deposited coatings were evaluated basicly by metallographical examinations (microhardness, film thickness, adhesion, structure (SEM, X-ray defraction) etc.) in view of the potential of high ion sputtered oxides and multilayer coatings with oxygenious interlayers.
9:50 AM B1-3-5 Deposition of CrN Coatings by Pulsed Cathodic Arc Evaporation Process
D.Y. Wang, K.W. Weng (National Chung Hsing University, Taiwan, ROC)
Conventional cathodic arc evaporation (CAE) process suffers from macroparticles contamination and excessive heat load on substrates, resulting from the energetic plasma flux ejected from hot cathode surfaces. In this study, a low frequency pulsing generator was implemented to modulate the cathode currents in high-low cycle. The deposition was conducted primarily during the high current cycles, while a minimum current flow was maintained to sustain the CAE process in DC mode. The migration behavior of cathode spots is improved, so cathodes can be operated steadily at lower currents. Macropaticles ejection was substantially reduced due to the effective cathode cooling. Influences of deposition parameters on mechanical properties of CrN thin film were investigated. Microstructure analyses were conducted using scanning electron microscopy (SEM) and x-ray diffractometry (XRD). A ball-on-disk tribometer was used to measure friction coefficients, wear rates, and adhesion strength of CrN coatings.
10:30 AM B1-3-7 Structure Modification of Magnetron-sputtered CrN Coatings by Intermediate Plasma Etching Steps
H.-S. Park (Seoul National University, Korea); H. Kappl (Forschungsinstitut für Edelmetalle und Metallchemie, Germany); J.-J. Lee (Seoul National University, Korea); H.A. Jehn (Forschungsinstitut für Edelmetalle und Metallchemie, Germany)
Most often PVD coatings show defects like pores and pinholes caused by the growth mechanism inherent to the deposition process. Such defects - when going through from the top surface to the coating/substrate interface - can result in a markedly decreased corrosion resistance of the coating/substrate system if a less noble substrate material is coated with the more noble hard nitrides, when compared with the coating material. Hence, the corrosion resistance of the coating/substrate system can be improved by “densifying” the morphology of the coatings. This was proved with a 3 µm thick CrN film deposited by magnetron sputtering on high speed steel substrates. The coating process was interrupted several times for an intermediate plasma etching process (-1000 V, 5 min, 1 - 16 steps). The coatings showed a multiple-layer structure in which the interfaces can clearly be distinguished. The corrosion resistance as characterized by electrochemical current density-potential measurements was strongly increased already by a few number of etching steps. The interfaces were additionally characterized by TEM and AES depth profiling. The mechanical properties (hardness, critical load) stay almost unchanged, an important factor for the application of such hybrid process coated parts facing corrosive environmental attack.
10:50 AM B1-3-8 Production and Characterization of Single and Multilayered Chromium Nitride (CrN- CrN + Cr@Sub 2@N) Coatings
A.M. Yargan, M. Ürgen, O.L. Eryilmaz, M.K. KazmanliI, A.F. Cakir (Istanbul Technical University, Turkey)
There is an increasing interest towards CrN hard coatings in tribological applications. Physical vapour deposited (PVD) chromium nitride coating (CrN) was introduced as a coating for applications requiring a high degree of abrasive and adhesive wear protection and prevention of metal pick-up and galling. By controlling the partial pressure of nitrogen and bias voltage during arc-PVD process, it is possible to produce films of composition ranging from pure chromium to CrN. At low nitrogen partial pressures and high bias voltages, the film can contain a mixture of Cr2N and CrN phases. At high nitrogen partial pressures and low bias voltages, the film contains only CrN phase. In this study, single layer CrN, Cr2N and various multilayered CrN - CrN + Cr2N coatings on high speed steels (HSS) were coated and characterised with respect to their structure, hardness, adhesion and wear properties. The corrosion behaviour of single layer and multilayer CrN, Cr2N coatings was also investigated and compared with respect to their porosity.
11:10 AM B1-3-9 Unbalanced Magnetron Sputter Deposited CrN Coatings with Enhanced Hardness Properties.
D.B. Lewis (Sheffield Hallam University, United Kingdom); T. Hurkmans (Hauzer Techno Coatings Europe, BV., Netherlands); H. Paritong, Q. Luo, W.-D. Münz (Sheffield Hallam University, United Kingdom)
CrN coatings belong to the most established surfaces in wear protection of engineering components when PVD technology is requested. CrN coatings are characterised by low deposition temperatures with typical hardness values of HV 2000 and excellent adhesion performance when deposited on steel substrates. This paper reports on an investigation of the reactive deposition of CrN by unbalanced magnetron sputtering in gas mixtures of Ar and N2, with N2 flow rates twice as high as that of Ar. Under these conditions, coatings of 3 µm thick have been produced which exhibit hardness values above HK 3000 and a plastic hardness Hpl >40 GPa. The high hardness values are consistent with the large increases in lattice parameter (values of up 4.255 Å compared with 4.14 Å for the JCPDS value) and high internal stresses observed, i.e. up to -5.2GPa. The grain size as measured by TEM decreased from typically 100nm to 30nm which is comparable with corresponding values for TiN and TiAlN PVD coatings. Furthermore, XRD analysis showed that the coatings were highly textured with a (200) preferred orientation. SNMS and RBS analyses also revealed a composition close to stoichiometry. The introduction of a stress releasing base layer is imperative to achieve critical load values Lc beyond 40N as well as reasonable corrosion and tribological results.
11:30 AM B1-3-10 Growth of TiO@sub 2@ and TiN Thin Films Using New High Power Magnetron Sputtering Source
M.J. Jung, H.Y. Lee, J.G. Han, J-H. Boo (Sungkyunkwan University, Korea)
TiO@sub 2@ and TiN thin films were deposited on Si(100) and glass substrates in the growth temperature as low as below 200 @super o@C using newly developed pulsed D. C. magnetron sputtering source. We built-up a magnetron sputtering source with high power (20 - 120 W/cm @super 2@) and unbalanced magnetron (I inner coil : I outer coil = 2:1, magnetic field = 300 G). 4 inch Ti metal target (99.9% purity) with round type was mounted onto the sputtering sources, and oxygen and nitrogen were used as reactive gases with argon. Crack-free, stoichiometric polycrystalline TiO@sub 2@(101) thin films with high transmittance (90%) in the visible range were obtained on glass surfaces at 200 @super o@C. In the case of the TiN film deposition, however, highly oriented polycrystalline TiN thin films in the [100] direction were grown on the glass substrates at 200 @super o@C and 4 sccm of nitrogen flow. The TiN thin films showed very high reflectance (80%) in the infrared region, indica! ting that these TiN films can be applied for the heat mirror. The as-grown films were characterized with XRD, XPS, AES, SEM, ellipsometry, and UV-visible spectroscopy. During film deposition, plasma diagnostics was also carried out in situ by optical emission spectroscopy analysis. Four-point probe method was also utilized for the electrical resistivity measurements.
11:50 AM B1-3-11 Qualitative/Quantitative Model to Study the Deposition of Aluminium Nitride in a High Energy Plasma Assisted Processing
W. Ahmed, E. DeSilva (Manchester Metropolitan University, United Kingdom)
Plasma based processes such as sputtering , ion-implantation and plasma assisted chemical vapour deposition (CVD) have become popular in recent years for the deposition of thin film coatings in number of industrial applications including components for microelectronics, automotive machinery and aerospace. The generation of a plasma above a substrate surface provides extra energy to the gas mixture to enable a coating to be deposited at much lower substrate temperature thus allowing a wider range of potential applications to be developed. Many of the base materials used in the automotive and aerospace industry cannot tolerate high temperature used in techniques such as CVD. At low temperatures, the adhesion and structural integrity of the coatings produced by plasma based methods are often unsatisfactory. Therefore, an improved or new technology is required which can overcome these problems. An attractive alternative to high temperature CVD is to use a new technology called high energy intensified plasma assisted processing (HEPAP). @paragraph@ This work describes a qualitative/ quantitative model for the mechanism involved in a triode glow discharge employed to grow aluminium nitride films. A series of systematic studies have been carried out at varying degrees of cathode voltage, cathode current density, pressure range and ion collector voltage values over a fixed period of time. All films developed have been characterised using Scanning Electron Microscopy, Electron Dispersion Spectroscopy, X- ray Diffraction and micro hardness tests. The conclusions of this project have formed a basic theoretical model that can be applied to produce films of different materials. The use of an RF source to negatively biased substrate has enhanced the growth process. The optimum conditions established have been explained with the use of a theoretical model.
12:10 PM B1-3-12 High Intensity Plasma Assisted Deposition of Aluminium Nitride and Silicon Nitride
W. Ahmed, E. DeSilva (Manchester Metropolitan University, United Kingdom)
Chemical vapour deposition (CVD) has become a key technology for the synthesis of inorganic films for use in integrated circuitry, solar energy conversion and tribology. Silicon compounds has emerged as one of the most important materials and are widely used in semiconductors. Conventional methods for the preparation of thin silicon nitride films exhibit less acceptable defects in terms of dangling bonds and inefficient doping. @paragraph@ In the past various surface coating techniques such as vapour deposition, sputtering, ion implantation, ion nitriding and dual ion-implantation/plasma nitriding treatments have been applied to produce silicon nitride. Since ion implantation is a line-of-sight process and therefore irregularly shaped pieces will not be uniformly nitrided. Another factor is the depth limitation. Ion nitriding is a suitable alternative although there is a difficulty of removing oxide barrier that forms during the process. This process also operates in high pressures (1-10 torr) and at relatively low voltages thus producing a low energy plasma. As a result of low energy plasma a lengthy sputter cleaning process is required. @paragraph@ As an initial attempt, silicon discs were successfully nitrided using High Energy Plasma Assisted Processing (HEPAP). This process produces ions and neutrals of higher energies than the conventional methods. This also operates at low pressures and eliminates most of the deficiencies of the conventional techniques. The RF powered negative biased silicon wafers were coated with silicon nitride in a triode system where the thermoionic emitter and the ion collector were operated independently. The coatings obtained were characterised using Scanning Electron Microscope and Energy Dispersion Spectrometry. The hardness was tested using Knoop hardness tester and also the surface profilometry was determined. The low temperature coatings have established this High Energy Plasma Assisted Processing as an alternative method in plasma techniques.