The effects of mechanical properties of thin films on nano-indentation data: Finite element analysis (original) (raw)
Related papers
2013
Nanoindentation of thin film-thick substrate system is commonly employed tool to measure the mechanical properties of materials. Finite element simulation (FEM) of nanoindentation experiment can overcome the expense and limitations of sophisticated test procedure. This study focused on the FEM simulation of nanoindentation test in ABAQUS environment to check the effects of film-substrate material properties and geometry. The indentation process in concern involves a two dimensional axisymmetric model where a thin film is placed above substrate and indented by a rigid indenter for specific friction condition. Modulus of elasticity and hardness of thin film has been calculated from analysis results using empirical relationship. For this study, two types of thin film properties i.e. elastic-perfectly plastic and elasto-plastic with specific strain hardening condition are taken for consideration. Firstly, different elastic substrate materials have been used under elastic-perfectly plastic thin film to observe the substrate strength effects. The analysis has been conducted for four different indentation depths to incorporate the influence of depth of penetration also. Secondly, similar analysis has performed for strain-hardening film material for all substrate strength to compare the behavior with perfectly plastic case. Finally, thickness of substrate layer has also been varied to observe the effect of substrate thickness under nanoindentation test. The simulation result shows that substrate strength effect is pronounced on film modulus determination whereas hardness is not significantly sensitive to this effect. Substrate modulus with magnitude of smaller or near film modulus can predict reasonable value of film modulus whereas high strength substrate modulus i.e. rigid body as a substrate produces extremely high film modulus. Indentation derived film hardness affects significantly than elastic modulus due to incorporation of strain hardening in thin film properties. In addition, calculated film properties increases with the increment of indentation depth but shows negligible change due to the variation of substrate thickness.
Numerical study on the measurement of thin film mechanical properties by means of nanoindentation
Nanoindentation is a technique commonly used for measuring thin film mechanical properties such as hardness and stiffness. In this study, we used the finite element method to investigate the effect of substrate and pileup on hardness and stiffness measurements of thin film systems. We define a substrate effect factor and construct a map that may be useful in the interpretation of indentation measurements when it is not possible to make indentations shallow enough to avoid the influence of the substrate on the measurements. A new technique for measuring mechanical properties of thin films by nanoindentation is suggested at the end of this article.
Philosophical Magazine, 2006
Several models have been developed to extract the intrinsic elastic modulus of thin films from the composite film/substrate modulus value obtained from indentation tests on coated systems. Either analytical, semi-analytical or empirical, they generally propose an expression of the composite modulus as a function of the film and substrate elastic moduli and of the film thickness. When the substrate properties and the film thickness are known, the expression without adjustable parameter contains only the film elastic modulus as unknown parameter, which can thus be deduced.
Determining mechanical properties of thin films from the loading curve of nanoindentation testing
Thin Solid Films, 2008
Nanoindentation has been widely used to evaluate material properties. In this study, we propose a method that utilizes only the loading curves of an indentation test to extract the elastoplastic properties of an elastic-perfectly plastic thin film as well as the plastic properties of a work hardening thin film. The use of loading curve circumvents some common difficulties encountered during the post-processing of experimental unloading curves. Measurements are taken at two different indentation depths, which have different levels of substrate effects and lead to the establishment of independent equations that correlate the material properties with indentation responses. Effective reverse analysis algorithms are proposed by following which the desired film properties can be determined from a sharp indentation test. The extracted material properties agree well with that measured from a bulge test.
International Journal of Applied Mechanics, 2010
This paper presents alternative analysis methodologies to extract the elastic modulus and hardness of the ultra-thin films from nanoindentation load-displacement data, especially when the film thickness is only few hundred nanometers or less. At such film thickness, the conventional analysis methods for nanoindentation usually do not give accurate film properties due to the substrate effect. The new methods are capable to show how to determine the film-only properties and how the substrates affect the nanoindentation measurement, especially for ultra thin films. These methods give accurate results for nanoindentation of various metallic, ceramic and polymeric films. It also reveals the differences between the use of high-resolution nanoindentation set-up and normal nanoindentation set-up on the same films. The relationships between the mechanical properties and film thickness are also discussed.
Modeling the substrate effects on nanoindentation mechanical property measurement
EuroSimE 2009 - 10th International Conference on Thermal, Mechanical and Multi-Physics Simulation and Experiments in Microelectronics and Microsystems, 2009
Nanoindentation technique is commonly used to characterize the mechanical properties of thin films. However, the validity of the measurements is greatly affected by the indentation depth and the substrate properties. The purpose of this study is to understand the influence of the substrate properties, the thin film thickness and the mechanical properties of the thin film itself on force-displacement curves obtained by nanoindentation. The experimentally obtained force versus indentation depth curves of single and bi-layer thin film systems on silicon wafers were simulated using Finite Element Modeling (FEM). The materials properties of the thin film layers were extracted by fitting the load-displacement curves obtained by FEM and experiments. The experimental part of this study includes nanoindentation tests performed on low-k films deposited on a silicon substrate. These films were treated during different periods of time (0s, 20s, 35s, 70s, 140s, 350s and 700s) with He/H2 downstreamplasma (DSP) at a fixed temperature of 280°C, thereby resulting in a double layered structure with the same total film thickness, but with different thickness and mechanical properties of the "modified" top layer. The results of this work provide considerable insight for the determination of the mechanical properties of layered systems.
Elastic indentation problems in thin films on substrate systems
Journal of Mechanics of Materials and Structures, 2006
In this paper an analytical solution of an elastic isotropic thin-film on an elastic substrate under an axisymmetric loading on the plane surface is presented. The analysis is intended to model the micronanoindentation tests to evaluate some of the relevant properties of thin films and provide information about the influence of interface conditions between the film and the substrate. The theoretical solution of the equations of three-dimensional elasticity is obtained by using Dini and Fourier-Bessel expansions for the displacement field. To describe the elastic mechanical interaction between the indenter and the film for low load, we make use of the pressure distribution for contact between two homogeneous bodies, and the corresponding displacement field is solved in explicit form. The contact law is obtained with two different ideal interface conditions between the film and the substrate: perfectly bonded and frictionless contact. This form of the elastic solution may be utilized for different axisymmetric pressure distributions performed to model the interaction between the indenter and the film, thus obtaining an analytical framework for comparing experimental and numerical results.
A new paradigm in thin film indentation
Journal of Materials Research, 2010
A new method to accurately and reliably extract the actual Young's modulus of a thin film on a substrate by indentation was developed. The method involved modifying the discontinuous elastic interface transfer model to account for substrate effects that were found to influence behavior a few nanometers into a film several hundred nanometers thick. The method was shown to work exceptionally well for all 25 different combinations of five films on five substrates that encompassed a wide range of compliant films on stiff substrates to stiff films on compliant substrates. A predictive formula was determined that enables the film modulus to be calculated as long as one knows the film thickness, substrate modulus, and bulk Poisson's ratio of the film and the substrate. The calculated values of the film modulus were verified with prior results that used the membrane deflection experiment and resonance-based methods. The greatest advantages of the method are that the standard Oliver ...
Depth-sensing indentation modeling for determination of Elastic modulus of thin films
Mechanics of Materials, 2010
There are various methods to address the problem of determining the hardness of thin films when the substrate is involved in the deformation process produced during conventional indentation tests. For the determination of the elastic modulus using depth-sensing indentation methods, the problem is more complex due to the deformation of the equipment that comes in addition to the effect of the substrate.