IEC 62047-6:2009

IEC 62047-6 ®
Edition 1.0 2009-04
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Semiconductor devices – Micro-electromechanical devices –
Part 6: Axial fatigue testing methods of thin film materials

Dispositifs à semiconducteurs – Dispositifs microélectromécaniques –
Partie 6: Méthodes d’essais de fatigue axiale des matériaux en couche mince

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IEC 62047-6 ®
Edition 1.0 2009-04
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Semiconductor devices – Micro-electromechanical devices –
Part 6: Axial fatigue testing methods of thin film materials

Dispositifs à semiconducteurs – Dispositifs microélectromécaniques –
Partie 6: Méthodes d’essais de fatigue axiale des matériaux en couche mince

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
PRICE CODE
INTERNATIONALE
P
CODE PRIX
ICS 31.080.99 ISBN 978-2-88910-611-0
– 2 – 62047-6 © IEC:2009
CONTENTS
FOREWORD.3
1 Scope.5
2 Normative references .5
3 Terms and definitions .5
4 Test piece .7
4.1 Design of test piece.7
4.2 Preparation of test piece .7
4.3 Test piece thickness.7
4.4 Storage prior to testing.7
5 Testing method and test apparatus.7
5.1 General .7
5.2 Method of gripping (mounting of test piece).8
5.3 Static loading test.8
5.4 Method of loading.8
5.5 Speed of testing .8
5.6 Environment control .8
6 Endurances (test termination).9
7 Test report.9
Annex A (informative) Technical background of this standard .10
Annex B (informative) Test piece .11
Annex C (informative) Displacement measurement .12
Annex D (informative) Testing environment.13
Annex E (informative) Number of test pieces .14
Bibliography.15

62047-6 © IEC:2009 – 3 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
SEMICONDUCTOR DEVICES –
MICRO-ELECTROMECHANICAL DEVICES –

Part 6: Axial fatigue testing methods of thin film materials

FOREWORD
1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising
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patent rights. IEC shall not be held responsible for identifying any or all such patent rights.
International Standard IEC 62047-6 has been prepared by subcommittee 47F: Micro-
electromechanical systems, of IEC technical committee 47: Semiconductor devices.
The text of this standard is based on the following documents:
FDIS Report on voting
47F/15/FDIS 47F/17/RVD
Full information on the voting for the approval of this standard can be found in the report on
voting indicated in the above table.
This publication has been drafted in accordance with the ISO/IEC Directives, Part 2.
A list of all the parts in the IEC 62047 series, under the general title Semiconductor devices –
Micro-electromechanical devices, can be found on the IEC website.

– 4 – 62047-6 © IEC:2009
The committee has decided that the contents of this publication will remain unchanged until
the maintenance result date indicated on the IEC web site under "http://webstore.iec.ch" in
the data related to the specific publication. At this date, the publication will be
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.
62047-6 © IEC:2009 – 5 –
SEMICONDUCTOR DEVICES –
MICRO-ELECTROMECHANICAL DEVICES –

Part 6: Axial fatigue testing methods of thin film materials

1 Scope
This International Standard specifies the method for axial tensile–tensile force fatigue testing
of thin film materials with a length and width under 1 mm and a thickness in the range
between 0,1 μm and 10 μm under constant force range or constant displacement range. Thin
films are used as main structural materials for MEMS and micromachines.
The main structural materials for MEMS, micromachines, etc., have special features, such as
typical dimensions of a few microns, material fabrication by deposition, and test piece
fabrication by means of non-mechanical machining, including photolithography. This
International Standard specifies the axial force fatigue testing methods for micro-sized smooth
specimens, which enables a guarantee of accuracy corresponding to the special features. The
tests are carried out at room temperatures, in air, with loading applied to the test piece along
the longitudinal axis.
2 Normative references
The following referenced documents are indispensable for the application of this document.
For dated references, only the edition cited applies. For undated references, the latest edition
of the referenced document (including any amendments) applies.
IEC 62047-2:2006, Semiconductor devices – Micro-electromechanical devices – Part 2:
Tensile testing method of thin film materials
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1
maximum force
P
max
highest algebraic value of applied force in a cycle
NOTE Adapted from ASTM E 1823-05a [1] .
3.2
minimum force
P
min
lowest algebraic value of applied force in a cycle
NOTE Adapted from ASTM E 1823-05a [1].
3.3
mean force
P
mean
algebraic average of the maximum and minimum forces in constant amplitude loading, or of
individual cycles
NOTE Adapted from ASTM E 1823-05a [1].
—————————
The figures between brackets refer to the Bibliography.

– 6 – 62047-6 © IEC:2009
3.4
force range
ΔP
algebraic difference between the maximum and minimum forces in constant amplitude loading
3.5
maximum stress
σ
max
highest algebraic value of applied stress in a cycle
3.6
minimum stress
σ
min
lowest algebraic value of applied force in a cycle
3.7
mean stress
σ
mean
algebraic average of the maximum and minimum stress in constant amplitude loading, or of
individual cycles
3.8
stress range
Δσ
algebraic difference between the maximum and minimum stresses in constant amplitude
loading
3.9
maximum displacement
δ
max
highest algebraic value of applied displacement in a cycle
3.10
minimum displacement
δ
min
lowest algebraic value of applied displacement in a cycle
3.11
mean displacement
δ
mean
algebraic average of the maximum and minimum displacement in constant amplitude loading,
or of individual cycles
3.12
displacement range
Δδ
algebraic difference between the maximum and minimum displacements in constant amplitude
loading
3.13
force ratio
stress ratio
R
algebraic ratio of the minimum force (or the minimum stress) to the maximum force (or the
maximum stress)
62047-6 © IEC:2009 – 7 –
4 Test piece
4.1 Design of test piece
In order to minimize the influence of size, the test piece should have dimensions of the same
order as that of the objective device component. The shape and dimensions of the specimen
should be based on Annex C of IEC 62047-2.
The dimensions of the plane shape of the specimen shall be within an accuracy range of
±1 % as specified in IEC 62047-2. The length of the parallel part of the test piece shall be
more than 2,5 times the width. See C.1 in IEC 62047-2. The curved part between the gripped
ends and the parallel part should have a radius of curvature sufficient to not cause a fracture
at the curved part due to stress concentration. See C.2 in IEC 62047-2.
The gauge marks specified in IEC 62047-2 are not necessary if the marks may concentrate
stress or initiate fatigue fractures.
4.2 Preparation of test piece
The test piece should be fabricated using a process as similar as possible to that of the
device to which the thin film is to be applied. The test piece also should be fabricated
following the procedures specified in IEC 62047-2. The substrate removal process should be
carefully chosen to prevent damaging the test piece. See C.3 in IEC 62047-2.
The number of test pieces should be determined adequately according to the thin films tested.
See Annex E.
4.3 Test piece thickness
The thickness of each test piece shall be measured, as the film thickness is not usually
uniform over a wafer. The accuracy of the measurement shall be within 5 %. Each test piece
should be measured directly. However, the film thickness at the step height of a window
opening etched near the test piece can be used as the thickness of a specimen in order to
avoid mechanical damage from the use of a stylus profiler, etc. Methods of measuring film
thickness and measurement errors are given in C.4 of IEC 62047-2.
4.4 Storage prior to testing
In the case of thin films, the storage environment may affect the fatigue properties. If there is
an interval between final preparation and testing, particular care should be taken in storing
the test pieces, and the specimens should be examined by appropriate means to ensure that
the surface has not deteriorated during the storage period. If any deterioration is observed
that was not present after the specimens were prepared, testing shall not be performed.
However, if the damage was introduced during the preparation processes, the test shall be
performed.
5 Testing method and test apparatus
5.1 General
The testing machine should be equipped with a gripping mechanism appropriate for the test
piece, as well as with a mechanism for applying cyclic loading. The cyclic loading applied to
the test piece should be basically tensile-tensile mode loading.
For constant range force testing, maximum and minimum forces (or mean force and force
range) shall be monitored and the testing machine should be equipped with a constant force
range control system. For constant displacement range testing, the maximum and minimum

– 8 – 62047-6 © IEC:2009
displacements (or mean displacement and displacement range) shall be monitored and the
testing machine should be equipped with a constant displacement range control system.
A test-piece failure detection system should be provided and the number of loading (or
displacement) cycles to failure shall be recorded.
5.2 Method of gripping (mounting of test piece)
Each test piece shall be mounted so that the loading axis and test piece axis are aligned.
When gripping both ends of the test piece, care shall be taken to avoid applying excess force
and/or bending stress to the test piece. The gripping methods indicated in Annex A of
IEC 62047-2 are recommended for mounting the test pieces. In addition, the testing apparatus
should be equipped with a test piece alignment mechanism to ensure that the tensile axis of
the test piece is aligned with the loading direction of the test apparatus.
5.3 Static loading test
Static tensile testing of the test piece is recommended before fatigue testing in order to
determine the testing conditions. Static tensile testing shall be carried out according to the
procedures specified in IEC 62047-2.
5.4 Method of loading
If the specimen was fractured during the first loading cycle, the fracture stress shall be
recorded and described in the report. The maximum and minimum forces (or mean force and
force range) shall be kept constant during the constant force range test. The maximum and
minimum displacement (or mean displacement and displacement range) shall be kept
constant during the constant displacement range test.
A load cell with a resolution adequate to guarantee 5 % accuracy of the applied force shall be
used. The drift of the load cell should be less than 1 % of the full-scale force during the
testing. See Annex B in IEC 62047-2 regarding the accuracy of the load cell.
For constant displacement range testing, a displacement measurement system with a
resolution adequate to guarantee 5 % accuracy of the applied displacement shall be used.
See Annex C.
5.5 Speed of testing
As the frequency of the stress cycle will depend upon the testing environment, the type of
testing machine employed, and the stiffness of the test piece, the frequency shall be that
which is most suitable for the particular combination of environment, material, test piece, and
testing machine. Generally, the frequency should be chosen properly depending on the
application of thin film materials. In addition, the frequency shall not heat the test piece during
the application of cyclic loading due to the rapid dissipation of strain energy in the test piece.
This practice does not apply to fatigue testing of viscoelastic films.
5.6 Environment control
As the environment greatly affects the fatigue properties of thin films, the testing temperature
and humidity shall be monitored during testing. The testing temperature and relative humidity
should be controlled to within ±1 °C and ±5 %, respectively. See Annex E. If it is difficult to
control the testing temperature and humidity, these values shall be described in the test
report.
62047-6 © IEC:2009 – 9 –
6 Endurances (test termination)
Fatigue testing shall continue until the test piece is fractured or a predetermined number of
cycles has been applied to the test piece. The termination criterion (test piece fracture or
predetermined number of cycles) shall be described in the test report.
7 Test report
The test report shall include the following information.
• Mandatory
a) reference to this International Standard, i.e. IEC 62047-6
b) test piece material
– in the case of a single crystal: crystallographic orientation
c) method and details of test piece fabrication
– method of thin film deposition
– fabrication processes
– heat treatment (annealing) conditions
d) shape and dimensions of test piece
e) fatigue test conditions
– mean stress (in the case of displacement control, mean displacement)
– stress range (in the case of displacement control, displacement range)
– testing environment (temperature and relative humidity)
– wave form (sinusoidal, triangular, ramp)
– frequency
f) fatigue test result
– number of applied cycles to failure. If the test piece is not fractured during a
predetermined number of cycles, the number of cycles and the description “no
failure” should be noted.
– definition (type) of failure
• Optional
a) microstructure
– in the case of polycrystalline thin film: texture and grain size
b) internal stress
c) surface roughness of test piece
d) brief description of fracture characteristics

– 10 – 62047-6 © IEC:2009
Annex A
(informative)
Technical background of this standard

A.1 Significance of axial loading fatigue testing for thin films
MEMS devices are usually prepared from thin films deposited on a substrate. The
micromachining techniques used are similar to the deposition and etching techniques
employed in LSI processing. The microstructure and surface roughness of thin films depend
upon the processing conditions, and micro/nano defects may occur during processing. These
defects affect the mechanical properties of the thin films. Therefore, the mechanical
properties of thin films should be measured using specimens prepared by the same process
that is used to prepare the actual applied devices. In particular, the fatigue properties of thin
films are essential data for designing durable and reliable MEMS devices. To date, fatigue
tests of micro-sized components, including thin films, have been carried out using on-chip
type test structures [2]-[4] and micro-sized specimens [5]-[6] prepared from thin films. These
methods are, however, not standardized, making it difficult to compare fatigue data from
different institutions. To date, ISO 1099 [8] and ASTM E 466-96 [9] have been specified as
standard testing methods for fatigue testing of macro-sized materials. Of these standard
testing methods, the axial fatigue testing method was established first, and extended testing
methods, including data processing such as S-N curves, have been specified. Axial fatigue
testing is thus a fundamental testing method for evaluating the fatigue properties of material,
as is tensile testing under static loading. Therefore, a general discussion of the fatigue
properties of MEMS devices is possible by first specifying the method used for axial fatigue
testing of thin films.
A.2 Outline of round-robin tests performed in Japan [10]
This standard specifies the method for axial tensile–tensile force fatigue testing of thin film
materials based on the results of round-robin tests (RRT) on axial fatigue testing of thin films
that were performed from 2003 to 2005 in Japan.
The RRT was carried out with the participation of several universities and research institutes
in Japan. The materials used were single and polycrystalline Si thin films, and polycrystalline
Al thin film. These thin films were deposited on Si wafers. Micro-sized specimens were
prepared from the thin film layer on the same wafer in accordance with IEC 62047-2 using a
photolithography technique. The geometry of each test piece was such that it fit the testing
machine at the specified institute, but the dimensions of the parallel parts of each test piece
were standardized in accordance with IEC 62047-2. Axial fatigue tests were carried out
mostly under force control, and the load application, force measurement, and displacement
measurement were noted. The effect of the environment (mainly humidity) on fatigue life was
also examined. The results were plotted as S-N curves and cross comparison of fatigue life
was made. The validity of the testing as a standardized method was investigated and
summarized in this standard.
62047-6 © IEC:2009 – 11 –
Annex B
(informative)
Test piece
The shape and dimensions of the specimen should be designed based on IEC 62047-2. The
axial fatigue test condition is determined by the yield stress and fracture strength of the test
piece. Fatigue test conditions are easier to determine if the same specimens for tensile
testing are used. Incidentally, the geometry of the cross section of the test piece specified in
IEC 62047-2 is proportionally reduced to that specified in ISO 6892 [11].

– 12 – 62047-6 © IEC:2009
Annex C
(informative)
Displacement measurement
When gauge marks are placed on the test piece, the displacement should be measured by the
interference light of the reflected light obtained by laser irradiation of the gauge mark and
simultaneous sensing of two gauge marks by a double-field-of-view microscope, which shows
two distant gauge marks at once. When gauge marks are difficult to place on the test piece or
the distance between the gauge marks cannot be measured (due to high cyclic frequency of
loading), the displacement of the gripping device or that of the actuator can be used, but a
description of such measurement shall be included in the report.

62047-6 © IEC:2009 – 13 –
Annex D
(informative)
Testing environment
The testing environment has a more significant effect on the fatigue life of micro-sized
materials than it does on that of macro-sized materials due to the larger specific surface area.
Particularly, the fatigue life greatly depends upon the humidity during the test [4]. Therefore,
control of the humidity during fatigue testing is critical for micro-sized materials.

– 14 – 62047-6 © IEC:2009
Annex E
(informative)
Number of test pieces
In general, fatigue data including fatigue life and fatigue strength are scattered widely, and
the statistical analysis is becoming important for estimating fatigue life and strength. For bulk
materials, these analyses are specified in ISO 12107 [12]. Based on this standard, the
number of test pieces can be determined depending on the required reliability of test results.
This standard is, however, limited to the analysis of fatigue data for materials exhibiting
homogeneous behaviour due to a single mechanism of fatigue failure.
For metallic thin film materials, the fatigue is usually controlled by single mechanism, and the
number of specimen can be determined based on ISO 12107. For Si thin film materials,
however, several fatigue mechanisms are considered to be involved, and the possible fatigue
mechanisms have not yet been identified. This indicates that the analysis method in ISO
12107 cannot be directly applicable for determining the number of test pieces for Si thin film
materials.
62047-6 © IEC:2009 – 15 –
Bibliography
[1] ASTM E 1823-05a, Standard terminology relating to fatigue and fracture testing.
[2] Kahn, H., Ballarini, R., Mullen., R. L., Heuer, A. H., Electrostatically actuated failure of
microfabricated polysilicon fracture mechanics specimens, Proceedings of the Royal
Society of London, 455 (1999), pp. 3807-3823.
[3] Ando, T., Shikida, M. and Sato, K., Tensile-mode fatigue testing of silicon films as
structural materials for MEMS, Sensors and Actuators, A93 (2001) pp. 70-75.
[4] Muhlstein, C. L., Brown, S. B. and Ritchie, R. O., High-cycle fatigue and durability of
polycrystalline silicon thin films in ambient air, Sensors and Actuators, A94 (2001), pp.
177-188.
[5] Sharpe Jr., W. N. and Bagdahn, J., Fatigue testing of polysilicon – a Review, Mechanics
of Materials, 36 (2004) pp. 3-11.
[6] Namazu, T. and Isono, Y., High-cycle fatigue damage evaluation for micro-nanoscale
single crystal silicon under bending and tensile stressing, Proc. 17th IEEE International
Conference on MEMS 2004, IEEE, Maastricht, Netherlands, (2004), pp. 149-152.
[7] Takashima, K. and Higo, Y., Fatigue and fracture of a Ni-P amorphous alloy thin film on
the micrometer scale, Fatigue & Fracture of Engineering Materials & Struc
...