Relation between the hue and composition of TiCxNy films prepared using multiple hollow cathode discharge ion plating

There is a distinct colour difference between electroplated gold layers and gold-like TiN films deposited by ion plating. In order to improve the hue of TiN coatings we have added carbon atoms to the Ti---N matrix and studied the influence of the carbon content on the hue of Ti---C---N complex films.

The films were prepared by means of the reactive ion-plating method using an in-line system composed of three chambers. The film composition was controlled by regulating the throughput of each reactant gas, i.e. nitrogen, acetylene, methane and hydrogen.

The colour of materials is dependent on the optical reflectivity and its dependence on the wavelength and on the lightness. It was found that a colour close to that of electroplated gold could be obtained with an appropriate TiC_xN_y composition, although the lightness of the film surface decreased as the reactant gas throughput increased.     

Control of the bias voltage in d.c. PVD processes on insulator substrates

In plasma-PVD processes, ion bombardment during the growth of thin films has a strong influence on films properties such as morphology, composition, structure, stress, electrical conductivity, and others. Therefore, an accurate control of substrate bias voltage is needed in order to deposit films with the desired properties. For insulator substrates, dc biasing the substrate holder is useless, since the surface shall not follow the applied bias but it will be at the non-controlled floating potential.In this work we present a simple method for the effective control of the substrate bias in dc PVD processes with insulator substrates, based on placing a metallic grid at a certain distance from the non-conductive surfaces to be coated. The desired negative bias is applied to this metallic grid which accelerates ions from the plasma and directs them to the surface to cover. This method has been successfully applied to the deposition of TiN coatings on glass and decorative ceramics by Cathodic Arc Deposition. The deposited films showed good adhesion and gold color, in contrast with the bad adhered and brownish films deposited without the grid. The dependencies on the color and on the mechanical properties of our TiN films deposited on insulating substrates with the value of the bias voltage applied to the substrate are similar to those typically reported in the literature when conductive substrates are used.     

Properties of thin TiN films deposited onto stainless steel by an in-line dry coating process

A new coil-coating pilot plant, capable of utilizing ion plating, sputtering and plasma-assisted chemical vapor deposition (PACVD) processes, independently or in series, was developed and optimum conditions for TiN, TiC, Al_xO_y, SiO_x and Cr coating were established. This paper is mostly concerned with the results of characterization (conducted in parallel by the authors′ two institutions) of TiN films deposited by ion plating or sputtering onto type-304 stainless steel strips. In particular, the dependence of the basic properties such as chemical composition, structure, adhesion, and color on the coating process are discussed with respect to anti-corrosion, anti-wear, and decorative applications. TiN coatings with a very attractive gold coloration were obtained; they performed well in wear testing, but did not show satisfactory corrosion resistance. However, it was found that the latter can be improved significantly by depositing a SiO_x, top layer by PACVD above the TiN coating. Thus the in-line dry coating processes are capable of producing highly functional steel surfaces with decorative color and high corrosion resistance.     

Effects of nitrogen ion implantation and implantation energy on surface properties and adhesion strength of TiN films deposited on aluminum by magnetron sputtering

The performance of tribological coatings depends greatly on the adhesion strength between the coatings and substrates. In this work, we investigated the influence of the ion implantation energy of nitrogen on the adhesion and surface properties of TiN deposited on aluminum substrate. Aluminum samples were implanted with 15 keV, 30 keV and 40 keV nitrogen ions before TiN films were deposited using magnetron sputtering in a custom-designed multi-functional ion implanter. The adhesion properties of the implanted TiN films were assessed using nano-scratch tests and were observed to vary with the nitrogen ion implantation energy. Our frictional test results show that an appropriate ion implantation energy and dose can improve the frictional behavior of TiN films deposited on aluminum.     

H. F.-Bias gesputterte TiN-Schichten zur Verschleißminderung an Grauguß-Kolbenringen

RF-Bias Sputtered TiN-Coatings to Reduce Wear of Cast-Iron Piston Rings By means of the reactive r.f. magnetron sputtering process TiN coatings with a thickness of 2.5 m?m and 6 m?m respectively, have been deposited onto piston rings made of cast iron. The coated piston rings have been tribologically tested using a model wear test, the so called short stroke test, which allows simultaneous testing of eight rings. This test method involves the most important stress features of the fired motor so that a good simulation of the stress conditions under which the piston rings and cylinder linings are working, is achieved. The results found with the short stroke test are compareable to those found with a fired test motor. The test was performed using TiN coated, uncoated and hardchromium electroplated cast iron rings. The reduction of the total wear of the rings and cylinder linings using a 6 m?m thick TiN coating was 85° compared to the uncoated rings and 50° compared to the chromium coated rings. The adhesion of the TiN coatings is excellent and even the graphite inclusions on the cast iron surface did not lead to any adhesion failure of the coatings under the present stress conditions.     

Evaluation of PVD nitride coatings, using impact, scratch and Rockwell-C adhesion tests

In this work the scratch test, the impact test and the Rockwell-C adhesion test were compared by investigating the adhesion properties of three types of sputtered physical vapour deposition coatings: TiN, CrN and Cr₂N. Each coating type was deposited on polished SAE 52100 steel, with different thicknesses in the nominal range of 2–20 μm, to evaluate the thickness influence on the test results. All the tests showed a ductile behaviour for the TiN coating with small delaminations and a brittle behaviour for the CrN and Cr₂N coatings with relatively large delaminations. An increase of the dimensions of the delaminations with increased coating thickness was detected for all layer types.

With the scratch test a significant increase in upper critical load with layer thickness was observed for all of the coatings. However, there was considerable variability especially for the Cr₂N coatings. The impact tests showed no coating failure for the TiN layer, and a decreasing impact crater volume with increasing layer thickness, whereas the CrN and Cr₂N layers failed after 10³ impacts and showed an increasing impact crater volume with increasing layer thickness.

The studies demonstrate the usefulness of using these test methods for differentiating between the behaviour of different coatings under various contact conditions.     

结构调制超硬Ti/TiN纳米多层膜的制备及其尺寸效应

使用多弧离子镀技术在高速钢基体上制备了调制周期为5~40 nm的Ti/TiN纳米多层膜,用扫描电子显微镜(SEM)、X射线能谱仪(EDS)、X射线衍射仪(XRD)、纳米压痕仪和划痕仪等手段表征薄膜的微观结构和性能,研究了调制周期对Ti/TiN纳米多层膜性能的影响,并讨论了在小调制周期条件下Ti/TiN纳米多层膜的超硬效应和多弧离子镀技术对纳米多层膜硬度的强化作用。结果表明,与单层TiN相比,本文制备的Ti/TiN纳米多层膜分层情况良好,薄膜均匀致密,没有明显的柱状晶结构,TiN以面心立方结构沿(111)方向择优生长。随着调制周期的减小薄膜的硬度呈现先增大后减小的趋势,并在调制周期为7.5 nm时具有最大的硬度42.9 GPa和H/E值。这表明,Ti/TiN在具有最大硬度的同时仍然具有良好的耐磨性和韧性。Ti/TiN纳米多层膜的附着力均比单层TiN薄膜的附着力高,调制周期为7.5 nm时多层膜的附着力为(58±0.9) N。     

A comparison of TiN films produced by reactive d.c. sputtering and ion-assisted deposition

The properties of TiN films produced by reactive d.c. sputtering have been compared with those formed by deposition during irradiation by 10 keV nitrogen ions. Films were deposited on aluminium, nickel, molybdenum, silicon and titanium substrates which were chosen because they have a range of mechanical properties. The composition of the films has been studied by Rutherford backscattering, nuclear reaction analysis and transmission electron microscopy and data concerning their hardness and adhesion are also presented. It was found that the films produced by ion-assisted deposition (IAD) were nearly stoichiometric TiN with a predominant (100) orientation while the reactively sputtered films were less crystalline and contained a significant amount of oxygen and carbon throughout the film. There was also considerable improvement in the adhesion of the IAD films but their hardness was only marginally improved.     

Influence of Ti/TiN bilayered and multilayered films on the axial fatigue performance of Ti46Al8Nb alloy

The effects of Ti/TiN bi- and multilayered films on the fatigue performance of the Ti46Al8Nb alloy were investigated. Ti/TiN films with a total thickness of 1 μm were deposited on the Ti46Al8Nb alloy substrate by the hollow cathode deposition method. The samples were examined with various analytical techniques including nanoindentation, scratch test, stripping layer substrate curvature test and scanning electron microscopy. The results show that multilayered Ti/TiN films can enhance the fatigue strength of the Ti46Al8Nb alloy, whereas bilayered films have no obvious effect. Compared with the bilayer, the multilayer exhibits higher hardness, higher residual compressive stress and higher adhesion strength to the substrate. It is also demonstrated that the multilayer is responsible for retarding fatigue crack growth. All the superior properties make the hard Ti/TiN multilayer to be an effective protection coating for the enhanced fatigue strength of the brittle substrate.     

Elektrolytisch abgeschiedene Edelmetallschichten in der Elektrotechnik

Electrodeposited noble metal layers in the electronic industry . Certain unique properties of the noble metals make them an important material for the modern electric and electronic industry. The application of electroplated noble metals is widely spread and ranges from silver layers for heavy duty contacts to the use of gold and rhodium films in the manufacture of semiconductor devices. Gold is used in large amounts in the electronics industry especially in the form of “hard gold” layers for contacts. Besides the pure metals, alloys are used. The applications demand deposits the properties of which are closely regulated by appropriate endpoint specifications, regulating e. g. purity, porosity, hardness, adhesion, wear resistance, solderability and ductility. The use of electrodeposited coatings of the noble metals in the electronics industry is assumed to increase in the future. Therefore the properties of the deposits and the deposition of alloys will be of enhanced interest. Special ways of deposition e. g. by selective plating will be developed.     

Influence of deposition pressure on the structural mechanical and decorative properties of TiN thin films deposited by cathodic arc evaporation

TiN coatings can be obtained in a relatively wide range of compositions around stoichiometry. Changing the stoichiometry around the 1:1 composition broadens the spectrum of colors and can modify the mechanical properties as compared with those of stoichiometric TiN. In this work, we present the deposition of TiN coatings by using a metallic Ti cathode and varying the nitrogen partial pressure in a cathodic arc evaporation reactive process. The composition, crystalline structure, hardness and color of the different samples are characterized, and the effect of deposition pressure is discussed. The hardest coatings were deposited in the interval of deposition pressures between 5 and 20×10⁻³ mbar. From the reflectance spectra in the visible range, a dominant wavelength of 581–582 nm is found for all the TiN samples, very close to that of the pure gold reference spectrum (579 nm) with purity colors that increase with the deposition pressure from 0.67 to 0.84 and approaches the color purity measured for the pure gold reference (0.91).     

Analysis of the oxidation kinetics and barrier layer properties of ZrN and Pt/Ru thin films for DRAM applications

ZrN and Pt/Ru thin films have been grown by an automated ion beam sputter-deposition system. Both materials were evaluated for use as barrier layers (ZrN) and bottom electrodes (Pt/Ru) in dynamic random access memory (DRAM) applications. The ZrN films had resistivities on the order of 250–300 μω cm. The ZrN films were (002) oriented and were rather smooth with an average surface roughness of ±17 Å. Analysis of the oxidation kinetics of the ZrN thin films reveals a thermally activated, diffusion-limited oxidation process with an activation energy of 2.5 eV in the temperature range of 500–650 ° C. This implies that there is an advantage in using ZrN as a barrier layer instead of TiN since the activation energy for oxidation of TiN is 2.05 eV. In addition, preliminary data suggest that a Pt/Ru double layer may be a promising bottom electrode and oxygen diffusion barrier for use in DRAMs with high-permitivity dielectrics.     

Bactericidal and biocompatible properties of TiN/Ag multilayered films by ion beam assisted deposition

Nanoscale TiN/Ag multilayered films of thickness 500 nm were synthesized on AISI317 stainless steel by ion beam assisted deposition (IBAD) with the modulation period of 4, 5, 6, 7.5, and 12 nm. The bactericidal and biocompatible properties of TiN/Ag multilayered films were investigated through Gram negative E. coli bacteria and L929 cells (mice fibroblast) as well as human umbilical vein endothelial cells (HUVEC). The results show that the TiN/Ag multilayered films with the modulation period of 7.5 nm possess the strongest bactericidal property. The cytotoxicity grade of TiN/Ag multilayered coating with the modulation periods of 7.5 nm, 12 nm is in 0-1 scope, which indicates this film has no cytotoxicity to L929. HUVEC on TiN/Ag multilayered film grows well and shows good cellularity. Auger electronic spectroscopy reveals the relationship between the structure of TiN/Ag multilayered film and the biomedical properties.     

Characterization of tribo-layers on self-lubricating plasma-assisted chemical-vapor-deposited TiN coatings

Recently, several new solid lubricants and modern lubrication concepts have been developed to achieve lower friction and wear and thus longer lifetime in severe tribological applications. The aim of this study is to characterize tribo-layers formed during ball-on-disc testing on low-friction, Cl-containing TiN coatings deposited by plasma assisted chemical vapor deposition and to clarify their formation mechanism. Characterization of the transfer layers was done by optical microscopy, optical profilometry, Raman spectroscopy, Auger electron spectroscopy and X-ray photoelectron spectroscopy. Differential scanning calorimetry was used to provide information on the chlorine-influenced chemical reactions of the coatings in ambient air. Iron oxide layers of a thickness in the nm-range have been found on low-chlorine containing TiN coatings (<3 at.% Cl) showing friction coefficients of approximately 0.8, whereas on TiN coatings with higher chlorine contents (>3 at.% Cl) rutile layers were preferably formed, resulting in friction coefficients below 0.2. This self-lubrication mechanism can be explained by the in-situ formation of easy-shearable titanium oxides in the contact zone in the presence of humidity and oxygen.     

Effect of the microstructure of Si3N4 on the adhesion strength of TiN film on Si3N4

The effect of the microstructure of silicon nitride, which was used as a substrate, on the adhesion strength of physical vapor deposited TiN film on Si₃N₄ was investigated. Silicon nitride substrates with different microstructures were synthesized by controlling the size (fine or coarse), the phase ( or β) of starting Si₃N₄ powder, and sintering temperature. The microstructure of Si₃N₄ was characterized in terms of grain size, aspect ratio of the elongated grain, and β-to- phase ratio. For a given chemical composition but different mechanical properties, such as toughness, elastic modulus, and hardness of Si₃N₄ were obtained from the diverse microstructures. Hertzian indentation was used to estimate the yield properties of Si₃N_4, such as critical loads for yield (P_y) and for ring cracking (P_c). The effect of the microstructure of Si₃N₄ on adhesion strength evaluated by scratch test is discussed. TiN films on Si₃N₄ showed high adhesion strengths in the range of 80–140 N. Hardness and the P_y of Si₃N₄ substrate were the primary parameters influencing the adhesion strength of TiN film. In TiN coating on Si₃N₄, substrates with finer grain sizes and higher phase ratios, which show high hardness and high P_y, were suitable for higher adhesion strength of TiN film.     

Bactericidal and biocompatible properties of TiN/Ag multilayered films by ion beam assisted deposition

Nanoscale TiN/Ag multilayered films of thickness 500 nm were synthesized on AISI317 stainless steel by ion beam assisted deposition (IBAD) with the modulation period of 4, 5, 6, 7.5, and 12 nm. The bactericidal and biocompatible properties of TiN/Ag multilayered films were investigated through Gram negative E. coli bacteria and L929 cells (mice fibroblast) as well as human umbilical vein endothelial cells (HUVEC). The results show that the TiN/Ag multilayered films with the modulation period of 7.5 nm possess the strongest bactericidal property. The cytotoxicity grade of TiN/Ag multilayered coating with the modulation periods of 7.5 nm, 12 nm is in 0–1 scope, which indicates this film has no cytotoxicity to L929. HUVEC on TiN/Ag multilayered film grows well and shows good cellularity. Auger electronic spectroscopy reveals the relationship between the structure of TiN/Ag multilayered film and the biomedical properties.     

Antireflection treatment of metal films for optical lithography

The effects of antireflection coating of thin metal films by surface chemical treatments to reduce reflectance for applications to very-large-scale integrated (VLSI) lithography have been studied. The study includes surface treatments in chemical solutions, thin film deposition and direct thermal reaction with gaseous chemicals. Aluminum and molybdenum films were used as test vehicles for the antireflection coatings. While many chemical compositions were effective in reducing aluminum reflectance, some chemicals produced a color with sufficient uniformity for VLSI applications. H₂O₂ was effective in staining molybdenum films, with a reflectance as low as 10% at a wavelength of 436 nm. Molydbenum nitride films, made by direct reaction with ammonia in the temperature range 500–750°C, also reduced the reflectance and added other beneficial properties. Deposition of transparent dielectrics is only effective in the deep-UV region. An opaque film deposition reduced the reflectance in the optical wavelength range. A thin zinc coating deposited by means of electroless plating showed the greatest reduction in reflectance. Some of these techniques applied to photoresist patterning near a tapered step were found to be useful for VLSI lithography.     

A method for elastic modulus measurements of magnetron sputtered thin films dedicated to mechanical applications

Mechanical properties of thin films may highly differ from those of chemically identical bulk materials. Their knowledge is of paramount importance for coatings manufacturers. In this paper, attention is paid on Young's modulus measurements of PVD magnetron sputtered thin films on metallic substrates. The method is based on the three-point bending test of partially coated stainless steel or titanium alloy substrates. After derivation of the corresponding equations, the method and its accuracy according to qualification tests are first described. Results are then presented for coatings as varied as C, W, Cr(C), and TiN with thicknesses spanning 0.5–10 μm, and deposited under different sputtering conditions. It is first seen that the Young's modulus highly depends on the deposition parameters, varying from the bulk values down to the fourth of this value. In the case of reactive sputtering, the evolution of the modulus with the gas flow is also presented and a correlation with phases or microstructure is observed. It is finally concluded that this kind of test, owing to its simplicity and its reliability, may help on a scientific point of view towards understanding the influence of morphology on mechanical properties, and on a practical basis for ensuring a control quality reference when performed systematically after deposition. Some foreseen extensions of this work to adhesion measurements will be mentioned shortly.     

The electromagnetic interference shielding effect of indium-zinc oxide/silver alloy multilayered thin films

A study was made to examine the electromagnetic interference (EMI) shielding effect of multilayered thin films in which indium-zinc oxide (IZO) thin films and Ag or Ag alloy thin films were deposited alternately at room temperature using a RF magnetron sputtering. The optical, electrical and morphological properties of the constituent layers were analyzed using an ultraviolet-visible photospectrometer, a 4-point probe and an atomic force microscopy (AFM), respectively. The EMI shielding effect of the multilayered thin films was also measured using a coaxial transmission line method. A detailed analysis showed that the control of the film morphologies, i.e., the surface roughnesses of the constituent metal layers was essential to an accurate estimate of the electrical and optical properties of multilayered coatings. It was shown that properly designed IZO/Ag alloy multilayered thin films could yield a visible transmission of more than 70%, a sheet resistance of less than 1 Ω/sq., together with an EMI shielding effect larger than 45 dB in the range from 30 to 1000 MHz.