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Paper Title Page
Abstract: The accurate characterization of linear coefficient of thermal expansion (CTE) of thin
films is vital for predicting the thermal stress, which often results in warpage and failure of a
MEMS structure. In this paper, special emphasis is placed on the development of novel test
method to extend an ISDG (Interferometric Strain/Displacement Gage) technique to the direct and
accurate CTE measurement of MEMS materials, AlN and Au. The freestanding AlN and Au films
are 1 μm thick and 5 mm wide. Strain is directly measured by a brand-new digital type ISDG with
two Cr lines deposited on the specimen while heating a specimen in a furnace. The whole test
system is verified first by measuring the CTE for the NIST’s SRM (Standard Reference Material)
736 (Cu) block. The measured CTE is 17.3 με/oC up to 167 oC, which agrees well with the
NIST’s certified value. The CTE of Au is 25.4 ± 1.15 με/oC and that of AlN film is 3.77 ± 0.12
με/oC. The in-plane displacement resolution is about 5 nm at the best circumstances.
199
Abstract: This work presents a comparison of numerical simulation and experiment of
nanoindentation testing. A commercial finite element code ANSYS is adopted in the numerical
simulation, in which elastic-plastic properties are considered. A PMMA specimen and a three side
pyramidal Berkovich probe tip is used in the indentation tests. While the elastic-linear workhardening
properties are adopted, the numerical results agree well with the experimental data for
different indentation loads. It proves the numerical simulation can be used in the small scale
analysis.
203
Abstract: We have designed and fabricated diamond-shaped AFM cantilevers capable of
performing multi-functioning tasks by using single crystal silicon (SCS) micromachining
techniques. Structural improvement of the cantilever has clearly solved the crucial problems
resulted from using conventional simple beam-AFM cantilever for mechanical testing. After forcecalibration
of the cantilever, indentation tests are performed to determine the mechanical behaviors
in micro/nano-scale as well as topographic imaging. A diamond Berkovich tip of which radius at the
apex is approximately 20 nm is attached on the cantilever for the indentation test and 3D topography
measurement. The indentation load-depth curves of nano-scale polymeric pattern (PAK01-UV curable
blended resin) are measured and surface topography right after indenting is also obtained. Development of
this novel cantilever will extend the AFM functionality into the highly sensitive mechanical testing
devices in nano/pico scale.
207
Abstract: It is critical to measure the static and dynamic deformation of the micro beam over their
full range of voltage and frequency inputs, which are key parameters for predicting device behavior.
In this study, full-field technique by correlation of projected fringe patterns is selected to determine
static deformation, while dynamic parameters can be obtained by DIC with high-speed CMOS
camera, whose maximal frame rate is 32k f/s. The static tests of micro beams are carried out by
applying electric field forces under different dc voltage, while the dynamic tests are excited by
harmonic excitations. Using the DIC method, the whole field in-plane or out-of-plane displacements
of the micro beams are obtained, and hence the dynamic characteristics by post-processing of
vibration analysis. Experimental results including the bending deformation and vibration parameters
are reported and compared with finite element method. This study verifies the feasibility of this
technique to measure both static and dynamic characteristics of MEMS components.
211
Abstract: We tried to apply the nanoindentation technique to yield strength characterization by
modifying a previous research. Although the yield strength determining technique developed by
Kramer et al. has been successfully demonstrated for large scale indentations on bulky metals, its
applicability is still doubtful to nanoscale indentations on thin films with severe roughness,
anisotropy, and interfacial constraint. In order to overcome these problems, we combined the
nanoindentation technique with a three-dimensional indent visualization technique in this study.
Nanoindentation tests were performed for Au and TiN thin films and their corresponding indents
were scanned by using an atomic force microscope. From the three-dimensional pile-up
morphology, a circular pile-up boundary was measured and input into the yield strength formulation
as an effective yielded zone radius. The yield strengths calculated were directly compared with
those from the microtensile test.
215
Abstract: As a reliable tool to measure the Young’s modulus, nanoindention technique has been
used widely recently. In this paper, nanoindetation technique was overviewed with its advantage
and limitation and a new method was proposed to determine material properties of film, i.e. both
Young’s modulus E and Poisson’s ratio ν from load-displacement curve of shallow-depth
indentation using ‘inverse method’.
219
Abstract: Extensive research has been done on porous silicon (PS) and its applications in
optoelectronics since the discovery of its light emitting properties. Porous silicon technology is also
used for silicon micro machining. However, porous films can be seriously strained and this often
causes mechanical curling, fracture and device failures. In the present study an optical apparatus
based on substrate curvature method was developed for intrinsic stress measurement of thin films,
which offered a lot of advantages as overall field, non-contact, high precision, nondestructive, easy
operation and quick response. Using the apparatus, the residual stress in porous silicon layers
prepared by electrochemical etching was obtained. The residual stresses in the films were
determined by measuring the curvature of the Si substrate before and after etching. It is found that
the residual tensile stress tends to increase with the porosity increasing and the doping concentration
of the silicon wafer increasing. The results show that there is a deep connection between the microstructure
PS and the residual stress distribution.
223
Abstract: In order to measure the mechanical properties of gold films on silicon substrate, two
types of specimens, i.e., bridged films and circular membranes, are manufactured. Using a wedge
tip, the bridged gold films are indented so that the films are pushed off, which is called as V-peel
test. The load-deflection curves obtained by the V-peel test are analyzed with the concept of
geometrically nonlinear beam by using the minimum potential energy theory together with Ritz
method. Thus, Young’s modulus and residual stress of the bridged gold films are obtained. Blister
test is also conducted to measure the Young’s modulus and residual stress of a circular gold
membrane, of which deformation is measured by Twyman-Green interferometer. By gradually
increasing the external pressure applied on the membrane, the interfacial fracture toughness
between the gold membrane and silicon substrate is measured based on the concepts of interfacial
fracture mechanics.
227
Abstract: A micro-scale uniaxial tension test method for measuring material mechanical properties
of thin film materials is introduced in this paper. A self-developed test device is established based
on the CMT8202 tension test machine. The Interference Strain/Displacement Gauge (ISDG)
method is used to measure the strain in the micro-samples. The three dimensional finite element
method (FEM) is utilized to optimize specimen geometry configuration and to reduce the stress
concentration in specimen around grip region. The experiments are carried out for the
polycrystalline copper thin film. The results show that stress-strain curves and the Young’s modulus
of the thin film material can be obtained by micro-scale tension test. The Young’s modulus
determined by micro-sample for polycrystalline copper thin film has a good agreement with
published results.
233
Abstract: Based on the relationship between quantified blurring degree of Kikuchi bands obtained
by an electron backscattering diffraction (EBSD) technique and macroscopic strains measured by a
strain gauge, the local compression strain SEBSD in sinter ore has been evaluated under various
conditions. There is a good linear relationship between the SEBSD and the strains measured by a
strain gauge. The local strain SEBSD evaluated by EBSD patterns can be used as an index of local
strains.
237