ICMCTF1999 Session F1/E4: Mechanical Properties and Adhesion

Thursday, April 15, 1999 8:30 AM in Room San Diego

Thursday Morning

Time Period ThM Sessions | Abstract Timeline | Topic F Sessions | Time Periods | Topics | ICMCTF1999 Schedule

Start Invited? Item
8:30 AM F1/E4-1 Depth Sensing Indentation of Thin Films: Results from the VAMAS TWA 22 Project
S.R.J. Saunders, N.M. Jennett (National Physical Laboratory, United Kingdom); D.T. Smith (NIST); T. Yoshida (University of Tokyo, Japan)
Technical Working Area (TWA) 22 of the Versailles Project on Advanced Materials and Standards (VAMAS) has ongoing projects in the area of mechanical property measurements for thin films and coatings. The first project, begun in 1996, includes nearly 50 participants in the measurement of thin film hardness and Young’s modulus using depth-sensing indentation. Experimental round-robin results and modeling analyses are being collected and compared for two coating systems: one hard coating (alumina) on a soft substrate (aluminum), and one soft coating (alumina) on sapphire. Coating thicknesses range from 0.1 μm to 5.0 μm for alumina and from 0.3 μm to 3.0 μm for aluminum. Comparisons between sets of experimental results and between experimental and modeling results will be presented. The different data sets are processed through a single data analysis procedure, thus allowing comparison of this important aspect of the experimental work. In addition, the status of a new project on thin film adhesion will be discussed. The project is beginning with a mini-round-robin test of adhesion of TiN coatings on steel.
8:50 AM F1/E4-2 Determination of Coating Mechanical Properties Using Spherical Indenters
K.C. Tang, R.D. Arnell (University of Salford, England)

This paper describes methods combining finite element analysis and experimental indentation testing to determine coating modulus and hardness independent of substrate effects.

To determine coating modulus, the contact modulus of the coated surface is first determined from the elastic portion of an experimental load/displacement curve. The modulus of the coating alone is then determined from a function derived by a parametric fimite element analysis of indentation behaviour.

The hardness of the coating alone is determined by comparing an experimentally determined mean contact pressure for the coated surface with parametric finite element results for the same contact geometry and known hardness ratios.

9:30 AM F1/E4-4 New Possibilities of Mechanical Surface Characterization with Spherical Indenters by Comparison of Experimental and Theoretical Results
T. Chudoba (Technische Universität Chemnitz, Germany); N. Schwarzer, F. Richter (Technical University of Chemnitz, Germany)

An accurate determination of mechanical properties of film substrate compounds and thin layers itself becomes increasingly important due to its economic relevance. On the other hand it is desirable to come to a calculated film design regarding the mechanical properties to limit the empirically based search for a suitable film. For both cases it is advantageous to use spherical indenters because they allow a description with analytical models and furthermore the splitting of the penetration process into a completely elastic an an inelastic part.

The results of a new analytical model for the calculation of elastic stresses and deformations during normal and tangential loading of a sphere will be compared with experimental results. It will be shown that the calculated load-depth data for different film substrate combinations agree with the results of indentation measurements.

Further, the change of value and position of the stress maximum and the measurable stiffness in dependence on the elastic properties and the thickness of the film are given. This is used for the evaluation of the critical load during scratch tests.

Finally, an outlook will be given for the calculation and evaluation of elastoplastic deformations due to spherical indentation in the case of homogeneous materials. An impoved analysis method is proposed that uses a pressure distribution after plastic deformation which is more realistic than that of the Hertzian theory.

9:50 AM F1/E4-5 Evaluation of Fracture Toughness of Ultra-Thin Amorphous Carbon Coatings Deposited by Different Deposition Techniques
X. Li, B. Bhushan (The Ohio State University)
The successful performance and reliability of thin coatings is often limited by their mechanical properties. Generally, harder coatings are more brittle and easily damaged by shock forces in practical applications. A necessary criterion for evaluating brittleness of thin coatings is to measure fracture toughness of the coatings. In this paper, the nanoindentation fracture of ultra-thin amorphous coatings on Si substrate deposited by filtered cathodic arc, direct ion beam, electron-cyclotron resonance plasma chemical vapor deposition and sputter deposition techniques was studied using a cube corner indenter. Based on the analysis of the energy release in cracking, the fracture toughness of the coatings was calculated. The nanoscratch fracture of the coatings was also studied, and compared with the nanoindentation fracture. The fracture mechanisms of various coatings were discussed.
10:10 AM F1/E4-6 Structure/Mechanical Properties Relationship of TiO2 Multi-Layers Deposited by Means of Modulated Magnetron Sputtering
F. Lapostolle, A. Billard, J. von Stebut (Ecole des Mines, France)

TiO2 is an insulator well known for its optical properties. High hardness and corrosion resistance are in favour of mutiple industrial applications.

In the present work we study PVD multi-layers with alternating Ti and O compositions obtained at low deposition pressures (<400K) by magnetron sputtering in a reactive plasma of varying, low pressure (0.2 0.3 Pa) Ar O carrier gas compositions.

Structural properties are assessed by standard metallurgical techniques like SEM, TEM and XRD. They are studied in relation with the surface mechanical properties assessed by depth sensing micro and nanoindentation, standard and microscratch testing as well as multipass friction fatigue in the online ,triboscopic operation mode.

The main issue in the present study is the relation between multilayer coating architecture and brittle mechanisms in tribologic applications

10:30 AM F1/E4-7 Mechanical Property Measurement - Lessons Learned from the Microelectronics Industry
B. Michel (Institute for Reliability and Microintegration (IZM),, Germany)

New generations of microelectronics and microsystem devices call for the utilization of a variety of new materials and the combination of materials with a wide spread of their mechanical and thermal characteristics. Reliability and functionality of microsystems, i.e. of small scale integrated electronic, mechanical and optical components, largely depend on their mechanical and thermal constitution. Thermo-mechanical aspects of component and system reliability become more and more important with growing miniaturization as the local physical parameters and field quantities show an increase in sensitivity due to inhomogeneities in local stresses, strains and temperature fields. Since there is usually a lack of information about the local material parameters, a pure field simulation cannot as a rule solve the problem. The state of the art of microsystem design more and more requires direct "coupling" between simulation tools (including e.g. FE modelling) and advanced physical experiments.

The author has combined various laser techniques, scanning microscopy, thermography and acoustomicroscopy with advanced numerical field simulation. The input data from the experiment are directly led into the simulation codes to get more realistic results for reliability estimation and life time prediction. The investigations have been directed towards electronic packaging of microsystems, crack and fracture behavior of multilayer systems ("fracture electronics") within the interconnected regions surrounding the chips and to other problems, e.g. occurring due to thermal "misfit" between different materials within the critical regions of microsystems. The author also deals with the microDAC method, a new powerful tool for microdeformation analysis within a scanning electron microscope applying the grey level image correlation method to obtain the strain fields and related local fracture quantities of microcomponents.

11:10 AM F1/E4-9 Effects of Composition and Structure on the Interfacial Fracture of Tantalum Nitride Films
N.R. Moody (Sandia National Laboratories); A. Strojny (University of Minnesota); D. Medlin (Sandia National Laboratories); A.A. Talin (Motorola); W.W. Gerberich (University of Minnesota)
Thin tantalum nitride films are often used in microelectronic applications because of their long term stability and low thermal coefficients of resistance. However, they are high heat generators that when combined with a high structural defect content and high compressive residual stresses can alter properties over long service lives. This has motivated replacing aluminum oxide substrates currently in use with higher heat transfer aluminum nitride. However, recent results characterizing interface structure and fracture properties of these films on aluminum oxide and aluminum nitride substrates lead to contradictory conclusions. We have therefore employed nanoindentation and nanoscratch testing to study interfacial fracture of tantalum nitride on a single multi-layer aluminum oxide and aluminum nitride substrate system. TEM, SEM, and AFM techniques were used to determine the relationship between interface structure and the fracture process and mechanics-based models were applied to determine fracture energies. The results showed that even though the compositions differed between the two substrate materials, the interface structures and fracture energies were essentially the same. In this presentation, the results will be discussed and used to show how interface composition and structure combine to control thin film adhesion. This work supported by U.S. DOE Contract DE-AC04-94AL85000.
11:30 AM F1/E4-10 High Temperature Nano-scale Mechanical Property Measurements
J.F. Smith (Micro Materials Limited, United Kingdom); K. Mao (Birmingham Research and Development Limited, United Kingdom); S. Zheng (Micro Materials Limited, United Kingdom)

Measurement of the small scale mechanical properties of surface engineered materials at elevated temperatures opens up significant new possibilities for the materials scientist. For example, wear resistant coatings and surfaces generally experience temperatures significantly above room temperature during normal service, and it is well known that both the hardness and modulus of such materials can be strongly dependent on temperature. It is clearly desirable to optimise the mechanical properties at the service temperature rather than to extrapolate the results of room temperature measurements. In addition, many microelectronic thin film structures are produced and processed at temperatures of several hundred degrees. A complete understanding of the interactions between the materials used can be obtained only by making measurements across the full temperature range rather than only at room temperature.

Insruments for routinely measuring the mechanical properties of materials on a very small scale have hitherto been limited to room temperature operation. One factor responsible for this is that in most nano-scale instruments the displacement transducer is placed above the specimen, thus leading to unacceptably high thermal drift. In the present work, a novel transducer arrangement has been used which obviates this. The configuration avoids any significant radiant heating, conductive heating, as well as convection currents. Specimen temperatures of 500 °C can be achieved with a thermal drift rate below 0.004 nm/s.

Nanohardness and nanoscratch results have been obtained on a variety of materials, including metals, thin films and ceramics. In many cases, these show a substantial temperature dependence of the mechanical properties. For the particular case of silicon, the well-known crystalline-to-amorphous transition behaviour has now been characterised from room temperature to 500°C.

11:50 AM F1/E4-11 Influence of the Temperature on the Cracking Progress of Submicron Glass Films Deposited on a Polymer Substrate
M. Yanaka, Y. Tsukahara (Toppan Printing Co., Ltd., JAPAN); N. Takeda (The University of Tokyo, JAPAN)

As the substitution for the conventional aluminum metalized film, the transparent gas barrier films consisting of a 10~100nm thick SiOx film deposited on a 12µmm-thick polyethylene terephthalate (PET) substrate are widely noticed in the food packaging industry. In the manufacturing process, such as the lamination or the heat sealing, films are often loaded under high temperature conditions.

Therefore, in order to investigate the temperature influence on the fracture strength, the multiple cracking progress in SiOx films during tensile tests in the furnace were in-situ observed. It was shown that at the temperature of 82°C, the crack onset applied strain was higher than that at 33°C. In addition, at 82°C, increasing rate of cracks with the applied strain became slower than that at 33°C.

Next, to take into account the influence of the mechanical properties of the substrate to the cracking, tensile tests of bare PET films were performed at different temperatures. The remarkable reduction of the Young's modulus and the yield stress were seen around 70°C. The residual strains in films which are also significant factors, were also estimated from the curvature of SiOx/PET specimens at different temperatures. With the consideration of these factors, the cracking progress in SiOx films with different temperatures were reasonably predicted by the modified shear lag analysis.

Time Period ThM Sessions | Abstract Timeline | Topic F Sessions | Time Periods | Topics | ICMCTF1999 Schedule