ICMCTF1998 Session B2-2: CVD Hard Coatings & Technologies - CVD, MOCVD & Related Techniques

Wednesday, April 29, 1998 1:30 PM in Room Golden West

Wednesday Afternoon

Start	Invited?	Item
1:30 PM	Invited	B2-2-1 Understanding Gas-Phase Reactions in the Thermal CVD of Hard Coatings Using Computational Methods M. Allendorf (Sandia Naional Laboratories) Ceramic coatings are of considerable commercial interest for a wide range of applications because of their many desirable properties, which include corrosion resistance, stability to oxidation at high temperatures, hardness, optical and electronic properties, etc. Manufacturing processes based on chemical vapor deposition (CVD) are often used to form these materials and typically involve high temperatures (≥600 °C), where gas-phase chemical reactions can be important. Unfortunately, quantitative evalution of the importance of gas-phase chemistry is usually difficult due to the lack of reliable thermochemical and kinetic data. The focus of this presentation will be the use of theoretical and experimental methods to address the need for basic knowledge of the high-temperature reactions occurring during the CVD of these materials. First, ab initio electronic structure calculations, using BAC-MP4 calculations and other methods, will be described that enable the accurate (±2-3 kcal/mol) prediction of heats of formation for first- and second-row compounds. Second, examples of experiments conducted in a high-temperature flow reactor will be described, in which the products and rates of gas-phase reactions relevant to CVD were measured. Chemistry relevant to several CVD systems will be described, including silicon carbide, hexagonal boron nitride, titanium nitride, and indium oxide.
2:10 PM		B2-2-3 LPCVD and PACVD (Ti,Al)N Films: Morphology and Mechanical Properties S. Anderbouhr (CEREM, France); V. Ghetta (LTPCM-ENSEEG, France); C. Chabrol (CEREM, France); E. Blanquet (LTPCM-ENSEEG, France); F. Schuster (CEREM, France); C. Bernard (INPG-CNRS-UJF, France) Coatings of (Ti,Al)N have been deposited on Silicon and different kinds of steel substrates by both Low Pressure CVD and Plasma-Assisted CVD starting from in situ chlorination of a TiAl alloy mixed with NH3, H2 and Ar. The morphology and microstructure of the as-deposited films were investigated using XRD, SEM, EDS as well as RBS and NRA (composition and stoechiometry). Hardness and scratch tests measurements have been also performed in order to evaluate tribological and mechanical properties. Correlations between both processes and films morphologies have been pointed out.
2:30 PM		B2-2-4 Low Temperature MOCVD of V-C-N Coatings Using Bis(arene)vanadium as Precursors S. Abisset (INPT, FRANCE); F. Maury (CNRS, FRANCE) Vanadium carbide coatings were deposited on steel substrates by MOCVD in the temperature range 400-550 °C using bis(arene)vanadium as precursors. The films are polycrystalline and exhibit the cubic structure V₈C₇. Their crystallinity increases with the temperature. The composition of the films grown using V(C₆H₆)₂ does not change significantly in the whole temperature range and is typically V_0.52C_0.48. No significant difference of composition was observed for a coating grown using V(C₆H₅CH₃)₂ indicating that a methyl group bound to the aromatic rings does not increase the C content. SIMS profiles have shown the uniform depth distribution of the elements. Addition of C₆Cl₆ in the gas phase allows to decrease the C content and to increase the growth rate of the coatings. Then, depending on the composition of the initial mixture V(C₆H₆)₂/C₆Cl₆/H₂/He the different phases of the V-C phase diagram have been deposited at 400 °C, including the growth of coatings exhibiting the cubic structure of metal vanadium. However the C content of such films is about 14 at % that is far beyond its solubility in vanadium. Therefore they must be considered as a supersaturated metastable solid solution. Vanadium nitride coatings were grown at 550 °C using the input gas phase V(C₆H₆)₂/NH₃ in the same isothermal low pressure reactor. The films exhibit the cubic structure δ-VN with a (111) texture. The C content is lower than 5 at %. The deposition process and the main features of these V-based coatings are presented and discussed.
2:50 PM		B2-2-5 Deposition and Characterization of Zirconium-Based MOCVD Coatings C.P. Allenbach, M. Morstein, N.D. Spencer (Laboratory for Surface Science & Technology, ETH Zurich, Switzerland) Protective films of ZrN and its derivative Zr(C,N) deposited by MOCVD (metallorganic chemical vapor deposition) are among the less investigated hard-coating materials. In comparison to TiN, which is widely used for cutting tool coatings, these films display a smaller coefficient of friction while possessing comparable hardness and chemical properties. Advantages of ZrN in the machining of non-ferrous metals (brass, Ti alloys) have been reported. Systematic investigations concerning the tribological properties, the substrate-layer interface, and the deposition of gradient layers or multilayers are still lacking. Until now, Zr(NEt₂)₄ has mainly been used, by other groups, as a precursor for MOCVD of zirconium nitride. Three new precursors, Zr(NEtMe)₄, Zr(pip)₄ and Zr(pyrr)₄, have been synthesized and characterized in our laboratory. The substituents in these volatile molecules have been chosen such that thermal decomposition occurs at lower temperatures, thus reducing loss of substrate hardness during deposition. The compounds already contain direct zirconium-nitrogen bonds. Coatings were deposited on both silicon wafers and HSS tool-steel samples in the temperature range of 350 to 700°C using a low-pressure cold-wall reactor. Decomposition byproducts were investigated using an in-line mass spectrometer. Coatings and interfaces were chemically characterized employing XPS analysis and depth profiling. Phase analysis was carried out using XRD. Coating thickness and growth rate were evaluated. Hardness was determined from both micro- and nanoindentation techniques. Surface roughness was measured by AFM and the morphology of the film surface and cross-section characterized by FE-SEM. Tribological results were obtained using a pin-on-disk tribometer. Both precursors proved to be suitable for use with the MOCVD technique and our experimental set-up. The concentration of carbon and oxygen impurities, however, had a remarkable impact on the established hardness values.
3:30 PM		B2-2-7 LPCVD, PACVD and PVD (Ti,Al)N Films : Comparison Between PCV and CVD Processes F. Schuster, S. Anderbouhr (C.E.A, France); C. Chabrol (C.E.A., France); E. Blanquet (INPG-CNRS-UJF, France); L. Filhol (C.E.A, France); C. Bernard (INPG-CNRS-UJF, France) The present work reports the results of a comparative study of the TiAlN films properties obtained by both PVD and CVD processes includind: PACVD, LPCVD, Arc deposition. Films with different Ti/Al ratios have been deposited onto high speed steels in order to evaluate tribological and mechanical performances. The microstructures were investigated using XRD, SEM as well as EDS, RBS and NRA. A comparison between these processes and a correlation with the morphologies and properties are performed.
3:50 PM		B2-2-8 Mechanical Properties, Structure and Oxidation Behaviour of (Ti_1-xAl_x)N-hard Coatings Deposited by Pulsed dc Plasma-assisted Chemical Vapor Deposition (PACVD) C. Jarms (Stiftung Institut für Werkstofftechnik, Germany); H.-R. Stock (Institutfür Germany); P. Mayr (Institutfür, Germany) Wear resistant (Ti_1-xAl_x)N hard coatings were deposited in the whole range 0 < x < 1 by pulsed dc plasma-assisted chemical vapour deposition on high speed steel. TiCl₄ and AlCl₃ – generated in situ – were used as metal precursors. The influence of the AlCl₃-partial pressure and the plasma voltage on the properties of the coatings were examined. The aluminium content increases linear with the AlCl₃-partial pressure and the plasma voltage. The coatings have a smooth surface and the fracture surface exhibits a dense structure. The microhardness of the (Ti_1-xAl_x)N coatings is about 2000 HV for low aluminium contents (x < 0.5), but decreases to a value of 1300 HV for higher aluminium contents (x > 0.5). The adhesion – measured with the scratch test – decreases with increasing aluminium content. XRD measurements reveal the fcc structure up to an aluminium content of x = 0.8. A hexagonal wurtzite structure is formed for x-values greater than 0.97. X-ray photoelectron spectroscopy (XPS) depth profiles show a better oxidation resistance of (Ti_1-xAl_x)N as compared to TiN. The oxidation experiments were carried out in air at 600 °C. The oxidation resistance increases with increasing aluminium content. The chemical composition of the surface of the oxidised TiN-coating was similar to TiO₂. The aluminium content of the surface of the (Ti_1-xAl_x)N coatings increases during the oxidation. Aluminium atoms were found to diffuse to the surface.
4:10 PM		B2-2-9 Low Resistivity Tungsten CVD Using B₂H₆ Additions T.P.H.F Wendling (Fachhochschule Hannover, Germany); K.K. Lai (Applied Materials); D. Sauvage (Applied Materials, France); C. Maddalon, G. Wyborn (SGS Thompson, France); A.K. Mak (Applied Materials); M. Bakli (Applied Materials, Germany); W.A. Hathcock (Applied Materials) Currently CVD Tungsten plug technology is optimized for contact and via interconnect applications. Tungsten has been proposed to be used as gate electrode material and bit line contact in the source and drain regions for the next generation devices. A reduction of W resistivity by Diborane (B₂H₆), published by Hara¹ et. al., will be advantageous to these advanced applications that require device speed enhancement and geometry shrinkage. A novel Tungsten (W) CVD process was developed which includes B₂H₆ doping in various stages of the process recipe performed on an Applied Materials Centura^TM WxZ Tungsten chamber. The bulk resistivity of the CVD W film was measured at 8.5 μΩ-cm which represented a 38% reduction at 2000 Å thickness over the resistivity of a standard W CVD process. This work will report the W CVD process conditions and the metrics developed to measure the film density and thickness for a W CVD film resistivity verification. Other film properties such as: step coverage, reflectivity, surface roughness, stress , impurity content and crystal size of the obtained films will be compared to the standard W CVD film. A proposed model for the resistivity reduction was developed to explain the observed changes in the W films. Other possible applications of these novel low resistivity W films in future IC designs will also be discussed. ¹ T. Hara, T. Ohba, H. Yagi, H. Tsuchikawa in: Proc. Advanced Metallization for ULSI Applications in 1993, Edts.: D.P. Favreau, Y. Shachman-Diamond and Y. Horiike, Materials Research Society, Pittsburgh, PA, 1994, p. 353
4:30 PM		B2-2-10 Combinations of Coating and Heat Treating Processes: Establishing a System for Combined Processes and Examples O.H. Kessler, F.T. Hoffmann, P. Mayr (Stiftung Institut fuer Werkstofftechnik, Germany) High resistance of metals against wear, fatigue and corrosion can be achieved by several different treatments, like coating, thermochemical, thermal and mechanical processes. Combining successful single processes in one treatment can result in even higher resistance of materials against complex loads, e.g. wear, fatigue and corrosion superimposed, due to the addition of the single process advantages. For a substantial choice of technical and economical promising combined processes, a system for combined processes was set up. The single processes were divided into four groups: coating, thermochemical, thermal and mechanical processes. A 4 x 4 matrix out of these four groups was set up, which contains a large number of possible combined processes. This matrix holds for steels as well as for non-ferrous metals. The potential of different combined processes was analysed theoretically and experimentally. Several combined processes for steels and non-ferrous metals were reviewed. Common combined processes for steels are thermochemical treatment + coating and coating + thermal treatment. Examples like carburizing + CVD, nitriding + PVD, CVD + quench hardening and CVD + induction hardening will be presented. The combined process CVD + quench hardening illustrates the principle of combined processes: The high hardness of the thin CVD-coating is supported by the high strength of the quench hardened steel substrate. Examples for non-ferrous metals are plasma nitriding + precipitation hardening of aluminium and nitriding + CVD of titanium alloys. These examples will highlight the great potential of combined processes.
4:50 PM		B2-2-11 Chromazing and Aluminizing Processes Performed by CVD-Fluidized Bed Reactor in Iron Base Materials F.J. Perez, E. Otero, M.P. Hierro, C. Gomez, F. Pedraza (Universidad Complutense de Madrid, Spain) The diffusion of chromium and aluminium into iron base materials has been achieved using chemical vapor deposition in a fluidized bed reactor technique. The advantageous sinergistic effects of these two alloying element in minimizing the oxidation and corrosion of steels at high temperatures, suggest the use of both elements in diffusion coatings to form an alloy surface. Thermodynamic calculations have been performed in order to determine the optimum conditions for Cr and Al depositon. The results achieved demonstrate the potential utility of the fluidized bed reactor for depositing chromizing aluminizing coatings.