ICMCTF1999 Session B3/F4: Microstructure Characterization

Tuesday, April 13, 1999 8:30 AM in Room San Diego

Tuesday Morning

Start	Invited?	Item
8:30 AM	Invited	B3/F4-1 Recent Technologies and Advances in Thin Film and Coating Characterization Using Atomic Force Microscopy (AFM) F.M. Serry (Digital Instruments Inc. Veeco Metrology Group); J. Elings, J.T. Thornton, L. Ge (Digital Instruments Inc. Veeco Metrology Group, Australia); Y. Strausser (Digital Instruments Inc. Veeco Metrology Group) This talk starts with a brief introduction to the fundamentals of Atomic Force Microscopy (AFM) and some of the AFM techniques, including TappingMode AFM, where the AFM tip taps (rather than dragging on) the surface of the sample. Then, example images and data on thin films and coatings will show how AFM enables 1) visualizing qualitatively-meaningful-things such as surface texture, uniformity of substrate coverage, and grain structure; 2) quantifying the surface locally, through simultaneous measurements in all 3 dimensions on individual features anywhere on an image; and 3) globally quantifying the surface, through a host of statistical numerical representations for properties such as surface roughness, waviness, and average grain size--on the whole image or on any part of an image. Some of the more recent techniques are discussed next, including nano-indenting/nano-scratching, and phase imaging. Nano-indenting/nano-scratching are used to test mechanical properties of thin films and coatings, e.g., hardness, wear, and adhesion. For example, variations in thin film deposition parameters can affect film adhesion: one film adheres better to the substrate, while another film does not adhere so well to the substrate, but adheres to itself well. The AFM can reveal these and other differences. The applications of phase imaging include detection of contamination on a surface, and identification of different phases or constituents of a polymer or polymer coating. AFM's have traditionally been limited to scan areas of up to ~100 micrometers on a side, but that is changing. A new generation of instruments, the Atomic Force Profiler (AFP) is capable of profiling a surface in scans of up to 100mm long, and also imaging the surface in smaller areas to reveal both long-range and local topography with resolution that surpasses that of any stylus profilometer. The additional advantage of the AFP over all stylus profilometers is that it is far gentler on the sample, relying as it does on small intermitent contact forces of TappingMode for tracking the surface. AFM data on thin films and coatings in early stages of production can be tied directly to performance of final products; examples of this in semiconductor and data storage industries are discussed, along with relevant automation features in some of today's AFM's.
9:10 AM		B3/F4-3 Structure and Properties of Sputtered TiAl-M (M=Ag,Cr) Thin Films A.S. Ramos, B. Trindade, M.T. Vieira, C. Coelho (ICEMS - Departamento de Engenharia Mecânica - FCT da Universidade de Coimbra) Titanium aluminide intermetallic compounds are potentially important for use as high temperature structural materials. However, their application is limited due to the low room temperature ductility. One of the methods to overcome this difficulty is through the addition of alloying elements. The aim of this work was to produce TiAl-M (M = Ag, Cr) thin films by sputtering and to characterise them in terms of structure and mechanical behaviour in order to highlight the role of the third element on these properties. The investigation of a third element effect in solid solution in the TiAl compound may provide at atomic scale some hints for a better understanding of the relationship between chemical composition and mechanical properties. The films were studied in the as-deposited condition (metastable state) and after successive annealings up to a maximal temperature of 600ºC. The objective of these heat treatments was to obtain the stable intermetallic phase g-(TiAl) from the initial metastable structure. The experimental techniques used in this work were electron probe microanalysis, transmission electron microscopy and X-ray diffraction with a hot chamber allowing observing in-situ the structural evolution of the TiAl-M films. The mechanical analysis consisted on the determination of hardness and Young's modulus of the films by ultramicrohardness testing.
9:30 AM		B3/F4-4 CrN Coating on Mild Steel with Modified Interlayer of Electroless Ni Plating J.G. Duh, J.S. Chen (National Tsing Hua University, Taiwan) The electroless Ni-P coating is introduced as an interlayer to improve the properties of CrN/mild steel assembly. The acid hypophosphite-reduced bath is applied to deposit electroless Ni-P on mild steel (MS) substrate, and CrN is further prepared by reactive rf magnetron sputtering on the electroless deposited substrate. The electroless nickel layer crystallizes with the precipitation Ni3P phase due to the elevated temperature annealing during rf sputtering, and thus a coating assembly of CrN/Ni-Ni3P/MS is formed. An indentation and cracking tester is employed to investigate the indentation behavior of coating assemblies, and both hardness and Youngs modulus of the coating can be evaluated. The microhardness of the duplex coating ranges from 1966 to 2424 HK at a load of 15gf, in which the corresponding penetration depth is less than 1/6 of the CrN overlayer thickness. It is also observed that the friction coefficient of mild steel surface is reduced by EN deposition. A further reduction in friction coefficient can be achieved in the duplex coating, and is beneficial for the anti-wear behavior.
9:50 AM		B3/F4-5 Temperature Dependence of Thermal Expansion Coefficient and Bi-axial Modulus of Arc-ion Plated TiN, CrN, Cr₂N and AlTiN Coatings. K.Y. Yamamoto, T.S. Sato, E.I. Iwamura (Kobe Steel LTD., Japan) The temperature dependence of thermal stress of metal nitride was measured up to 500 degree using high temperature type thin film stress measurement system(Tencor F2400). And primary results on TiN, CrN, Cr₂N and AlTiN are presented. A series of metal nitrides (TiN, CrN, Cr₂N and AlTiN) were deposited by cathodic arc-ion plating onto Ti-6Al-4V and SUS304 substrate. The temperature dependence of thermal expansion coefficient and bi-axial modulus of these coatings were calculated from the temperature-stress relationship for the coating deposited onto substrates which have different thermal expansion coefficients. The result showed that thermal expansion coefficients of these coatings were monotonicaly increased as temperature increased up to around 500 degree and among these Cr₂N and AlTiN have largest values around 9.5x10^-6 /degree at room temperature. The bi-axial modulus showed slight temperature dependence for all coatings, but quite different for each coatings. The room-temperature bi-axial modulus of TiN, CrN, Cr₂N and AlTiN are 420, 320, 290 and 500 GPa respectively. Using this results, the stress-temperature relationship of TiN, CrN and Cr₂N which were deposited onto AISI-H13 tool steel and Ti-6Al-4V substrates were calcurated
10:10 AM		B3/F4-6 The Deposition of Compounds within the N,Ti Mixed Layer X.X. Ma (Harbin Institute of Technology, PRC); R.C. Che (National University of Defence Technology, PRC); P.L. Wu (Harbin Institute of Technology, PRC); L.F. Xia (Harbin Institute of Technology, P.R.China) By combining unbalanced magnetron sputtering ion plating titanium with plasma source ion implantation nitrogen in a same vacuum chamber, a N,Ti mixed layer which thickness is about 1 micron was obtained on the surface of steel 52100. It can be used for bearing steel surface hardening at lower treatment temperature. The composition of the N,Ti mixed layer was analyzed by XPS. It shows that the ratio between Ti and N keeps at the same level of 6:4. The microstructure of the layer was analyzed by TEM. It is found that very fine TiN particles deposited from the titanium mother phase within the modified layer. The orientation of the relationship of TiN and Ti is TiN[111] parallel to Ti[0001]. And there are some Fe₂Ti phase formed at the interface between the substrate steel 52100 and modified N,Ti mixed layer. After laying up at the room temperature and dry atmosphere for two months, the TEM sample was observed again. It was found that there were almost no TiN particles within the layer. Instead, Ti₂N phases were formed. Some mechnical properties of this kind of N,Ti mixed layer were also tested.
10:30 AM	Invited	B3/F4-7 In-Situ STM Studies of the Evolution of Surface Morphology and Microstructure in Epitaxial TiN(001) Grown by Ultra-High-Vacuum Reactive Magnetron Sputtering J.E. Greene, S. Kodambaka, M. Wall, V. Petrova, P. Desjardins, A. Vailionis, B.W. Karr, I. Petrov, D.G. Cahill (University of Illinois) TiN is widely employed as a wear-resistant coating on mechanical components and as a diffusion barrier in microelectronic devices. We use the epitaxial growth of TiN as a model system for insight on the evolution of surface morphology and microstructure in more complex polycrystalline films. Epitaxial TiN layers are grown on atomically-flat MgO(001) by reactive magnetron sputter deposition in pure N₂ at T_s ≥ 650 °C. Our in-situ STM results show that the development of surface morphology is dominated by growth mounds with an aspect-ratio of 0.006; both the roughness amplitude and average separation between mounds follow an approximate power law dependence on film thickness tγ with γ = 0.25. The films grow in a 2D multilayer mode in which island edges exhibit dendritic geometries characteristic of limited step-edge mobility. TEM shows that the films are epitaxial with dislocation loops on {111} planes and <001> misfit dislocations at the interface. Low-energy N₂⁺ ion irradiation during film growth leads to surface smoothing providing surface widths of 2 Å. However, ion energies > 45 V causes surface roughening with decreased in-plane length scales. High-temperature STM observations are used to follow the decay of small single-atom-high TiN islands at 700-950 °C on atomically-flat TiN(001) terraces and pits. Modeling the island decay rates, through adatom transport to step edges (for the case of single islands on terraces or in pits) or to larger islands through Ostwald ripening (for the case of multiple islands on terraces) yields insights into adatom surface diffusion rates, island detachment rates, and Ehrlich edge barrier energies.
11:10 AM		B3/F4-9 Mechanical Behaviour of Nanostructured W-Si-N Sputtered Films C. Louro, A. Cavaleiro (ICEMS - Departamento de Engenharia Mecânica - FCT da Universidade de Coimbra) In previous research work [1] the oxidation behaviour of W-(N) and W-Si-(N) sputtered coatings was characterised. The coatings containing Si were deposited from a tungsten target superimposed with 20 Si plates, presenting very high contents in this element (Si/W reaches 1). The coatings containing Si presented an amorphous structure in the as-deposited state. With thermal annealing the W-Si coating began to crystallise at 700ºC and finished for 950ºC. During this process, structural transformations took place either with phases change or with increase of the structural order. W-Si-N coating keeps its amorphous structure up to 1000ºC, presenting at this temperature the first signs of crystallisation. Veprek et al [2] found important improvements in the hardness values for W-Si-N films when small crystallites (<40nm) of W2N were dispersed in a Si-N amorphous matrix. The aim of this study is to evaluate the hardness and Young´s modulus of W-Si and W-Si-N films deposited by sputtering after have been thermal annealed at increasing temperatures. The results will be correlated with the degree of structural order obtained for the coatings. [1] - C. Louro and A. Cavaleiro, accepted for publication in Thin Solid Films. [2] - S. Veprek, M. Haussmann and S. Reiprich, J. Vac. Sci. Technol. A, 14(1996)46.
11:30 AM		B3/F4-10 Improvement of the Mechanical Performance of (W-C/N)-Based Coatings by Ti Addition A. Cavaleiro, M.T. Vieira, B. Trindade (ICEMS - Departamento de Engenharia Mecânica - FCT da Universidade de Coimbra) Ternary coatings of transition metal nitrides / carbides represent one of the most important type of materials in the field of hard coatings. The association of two transition metals not belonging to the same group or the same period of the periodic table with carbon or nitrogen gives rise to materials with improved mechanical properties. The aim of this work is to study systematically mixed W-Ti-C/N coatings deposited by reactive sputtering. For that, various W targets with increasing Ti contents (0,10, 20 and 30 wt.%) were used for the depositions with increasing partial pressures of methane or nitrogen and substrate bias. The films have been characterised by electron probe microanalysis, x-ray diffraction, scanning electron microscopy, ultramicrohardness and scratch testing. The interrelations between chemical composition, structure, degree of structural order and mechanical behaviour of the coatings will be presented and discussed.
11:50 AM		B3/F4-11 Properties of Zirconium Oxide Thin Films Deposited by Pulsed Reactive Magnetron Sputtering K. Koski (CEA Grenoble, CEREM-DEM-SGM-LSMM, France and University of Turku, Finland); J. Holsa (University of Turku, Finland); P. Juliet (CEA Grenoble, CEREM-DEM-SGM-LSMM, France) Zirconium oxide thin films were deposited by reactive circular d.c. magnetron sputtering on glass, silicon wafer and stainless steel substrates. The thickness of the films deposited varied between 200 nm and 3 µm. These coatings have many technological interesting properties, like good wear resistance, high insulating capability, chemical and thermal stability, high hardness and transparency. The properties in interest were ratio Zr / O, nanohardness, surface roughness, film density, residual stress, refractive index and crystallographic structure. The properties were studied in terms of the process parameters such as sputtering gas pressure, target voltage and substrate bias voltage. The highest deposition rate obtained for zirconium oxide thin film was 135 nm / min. The power of the target was 1500 W. The zirconium oxide thin films deposited had monoclinic structure having the density between 5.13 and 5.77 g cm^-3. The ratio Zr/O varied between 2.02 and 2.59 depending on the target voltage used. The related nanohardness and the surface roughness were between 12.1 and 17.8 GPa, and 2.9 and 12.6 nm, respectively. The intrinsic stress varied between - 1000 and 150 MPa. Arcing was observed during deposition resulting in defects and macroparticle contamination on the surface of the thin film.