IEC 62951-3:2018

IEC 62951-3 ®
Edition 1.0 2018-11
INTERNATIONAL
STANDARD
colour
inside
Semiconductor devices – Flexible and strechable semiconductor devices –
Part 3: Evaluation of thin film transistor characteristics on flexible substrates
under bulging
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IEC 62951-3 ®
Edition 1.0 2018-11
INTERNATIONAL
STANDARD
colour
inside
Semiconductor devices – Flexible and strechable semiconductor devices –

Part 3: Evaluation of thin film transistor characteristics on flexible substrates

under bulging
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 31.080.99 ISBN 978-2-8322-6161-3

– 2 – IEC 62951-3:2018 © IEC 2018
CONTENTS
FOREWORD . 3
INTRODUCTION . 5
1 Scope . 6
2 Normative references . 6
3 Terms and definitions . 6
4 Test piece . 6
4.1 General . 6
4.2 Size of a test piece . 7
4.3 Measurement of dimensions . 7
4.4 Storage prior to testing . 7
5 Test apparatus and procedure . 7
5.1 General . 7
5.2 Test apparatus . 7
5.2.1 General . 7
5.2.2 Apparatus . 8
5.3 Test procedure and analysis . 12
5.3.1 Test procedure . 12
5.3.2 Data analysis . 14
6 Test report . 17
Annex A (informative) Other types of electrical and mechanical test equipments . 18
A.1 Absorption type electrical and mechanical test equipment with heating
system . 18
A.2 Bulging-type electrical and mechanical test equipment with halogen lamp
heating system . 18
Annex B (informative) Failure pressure estimation . 20
Bibliography . 22

Figure 1 – Pressure chamber open window shapes . 9
Figure 2 – Typical example of bulging-type mechanical and electrical measurement
test apparatus with heating system . 11
Figure 3 – Exemplary schematics of pressure chamber, pressure chamber open
window . 11
Figure 4 – Exemplary schematic of wire bonding. 12
Figure 5 – Exemplary DC characteristics for determining (a) μ (b) μ and (c) SS . 16
lin sat
Figure 6 – Representative bulge test data showing pressure-deflection relation for Ag-
Pd/SiN . 17
x
Figure A.1 – Exemplary schematic of absorption-type electrical and mechanical test
equipment with heating system . 18
Figure A.2 – Exemplary schematic of bulging-type electrical and mechanical test
equipment with halogen lamp heating system . 19
Figure B.1 – Schematic for failure pressure estimation for 100 μm-thick polyimide
assuming yield and tensile strength of 69 MPa and 231 MPa . 20

Table B.1 – Flexible substrate information (polyimide) . 20
Table B.2 – Pressure calculation results . 21

INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
SEMICONDUCTOR DEVICES –
FLEXIBLE AND STRECHABLE SEMICONDUCTOR DEVICES –

Part 3: Evaluation of thin film transistor characteristics
on flexible substrates under bulging

FOREWORD
1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising
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8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is
indispensable for the correct application of this publication.
International Standard IEC 62951-3 has been prepared by IEC technical committee 47:
Semiconductor devices.
The text of this International Standard is based on the following documents:
FDIS Report on voting
47/2492/FDIS 47/2511/RVD
Full information on the voting for the approval of this International Standard can be found in
the report on voting indicated in the above table.
This document has been drafted in accordance with the ISO/IEC Directives, Part 2.
A list of all parts in the IEC 62951 series, published under the general title Semiconductor
devices – Flexible and stretchable semiconductor devices, can be found on the IEC website.

– 4 – IEC 62951-3:2018 © IEC 2018
The committee has decided that the contents of this document will remain unchanged until the
stability date indicated on the IEC website under "http://webstore.iec.ch" in the data related to
the specific document. At this date, the document will be
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.
A bilingual version of this publication may be issued at a later date.

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INTRODUCTION
The International Electrotechnical Commission (IEC) draws attention to the fact that it is
claimed that compliance with this document may involve the use of a patent concerning the
method and apparatus for testing flexible elements.
IEC takes no position concerning the evidence, validity and scope of this patent right.
The holder of this patent right has assured the IEC that he/she is willing to negotiate licences
under reasonable and non-discriminatory terms and conditions with applicants throughout the
world. In this respect, the statement of the holder of this patent right is registered with IEC.
Information may be obtained from:
Industry Academy Cooperation Foundation of Sejong University,
Korea Institute of Machinery and Materials,
Electronics and Telecommunications Research Institute
1002 GwangGaeTo B/D
209, Neungdong-ro, Gwangjin-gu, Seoul, 05006,
KOREA
Attention is drawn to the possibility that some of the elements of this document may be the
subject of patent rights other than those identified above. IEC shall not be held responsible for
identifying any or all such patent rights.
ISO (www.iso.org/patents) and IEC (http://patents.iec.ch) maintain on-line data bases of
patents relevant to their standards. Users are encouraged to consult the data bases for the
most up to date information concerning patents.

– 6 – IEC 62951-3:2018 © IEC 2018
SEMICONDUCTOR DEVICES –
FLEXIBLE AND STRECHABLE SEMICONDUCTOR DEVICES –

Part 3: Evaluation of thin film transistor characteristics
on flexible substrates under bulging

1 Scope
This part of IEC 62951 specifies the method for evaluating thin film transistor characteristics
on flexible substrates under bulging. The thin film transistor is fabricated on flexible
substrates, including polyethylene terephthalate (PET), polyimide (PI), elastomer and others.
The stress is applied by applying a uniformly-distributed pressure to the flexible substrate
using the equipment.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their
content constitutes requirements 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 62047-17, Semiconductor devices – Micro-electromechanical devices – Part 17: Bulge
test method for measuring mechanical properties of thin films
IEC 60747-8, Semiconductor devices – Discrete devices – Part 8: Field-effect transistors
3 Terms and definitions
For the purposes of this document, the terms and definitions given in IEC 62047-17, in
IEC 60747-8 and the following apply.
ISO and IEC maintain terminological databases for use in standardization at the following
addresses:
• IEC Electropedia: available at http://www.electropedia.org/
• ISO Online browsing platform: available at http://www.iso.org/obp
3.1
flexible substrate
substrate with flexibility onto which a thin film transistor is fabricated
4 Test piece
4.1 General
The test piece shall be prepared using the thin film transistor fabrication process on flexible
substrates. The mechanical and electrical properties of thin film transistors may depend on
the fabrication processes. Thin film transistors shall be prepared to prevent formation of
cracks or flaws and delamination from the substrate.

4.2 Size of a test piece
As long as the size of a test piece is larger than that of the chamber open area, any test piece
will suffice. Since the change in electrical characteristics is related to strain or stress, it is
recommended that the thin film transistors be fabricated in a central region, where the strain
is uniform. To measure the electrical characteristics, attach lead wires to the source, drain
and gate pads of thin film transistors of the test piece.
4.3 Measurement of dimensions
The thickness and dimension of the thin film transistors and flexible substrate shall be
accurately measured respectively, because they are used to determine the mechanical and
electrical properties of thin film transistors. It is recommended that the thickness of thin film
transistors be smaller than that of the substrate in order to keep the deformation of the thin
film transistors uniform. The substrate material should be in-plane isotropic in order to keep
the stress and strain applied on the thin film transistor equibiaxial. There can be some
combinations of thin film transistor and substrate where it is difficult to fulfil the tolerance of
thickness measurement. In this case the average and the standard deviation of the thickness
measurement should be reported.
4.4 Storage prior to testing
In the case of thin film transistors, the storage environment may affect the electromechanical
properties of the thin film transistors. For example, oxidation on the test piece surface will
deteriorate the electrical and mechanical properties of the test piece. 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 Test apparatus and procedure
5.1 General
The test is performed by bulging a test piece at a specified temperature. To measure the
change in electrical characteristics along with the change in mechanical strain, carefully
select the measuring section. The section for measuring mechanical strain shall be coincident
with or scalable to that for measuring electrical characteristics. There are several types of
bulging equipment by which to measure the electromechanical property of thin film transistors.
It is not necessary that a certain type of bulging test method be preferred. As examples,
absorption-type electrical and mechanical test equipment with a heating system and
bulging-type electrical and mechanical test equipment with a halogen lamp heating system
are described in Annex A.
5.2 Test apparatus
5.2.1 General
By applying pressure to the specimen, the deformation response, i.e. the change in bulge
height as well as the electrical response of the thin film transistor on flexible substrate, shall
be measured. In general, test apparatus can be composed of pressuring device, pressure
chamber, pressure chamber open window, heating device (optional), bulging height
measurement unit and electrical measurement units as shown in Figure 2. Exemplary
schematics of pressure chamber, pressure chamber open window and wire bonding are given
in Figure 3 and Figure 4.
– 8 – IEC 62951-3:2018 © IEC 2018
5.2.2 Apparatus
5.2.2.1 Pressuring device
The pressuring device should be equipped to apply a specified continuous pressure with a
controlled rate or a certain level of pressure to the pressure chamber open window to be
stressed. Pressure media can be oil, gas and distilled water. In general, the device can be
composed of a pressure sensor and pressure controller. The controller should show an
accuracy of 1 % in the full test scale.
NOTE At the pressures encountered in the tests, gas is over a million times more compressible than typical
liquids such as oil and distilled water.
5.2.2.2 Pressure chamber
The pressure chamber should be as compact as possible, to reduce the compliance of the
test system. The volume, which has to be pressurized and which potentially contributes to the
compliance, would be minimized.
In case liquid is used to pressurize the test system, the system shall contain as little air as
possible because even a small air bubble trapped inside the test system can dominate the
system’s compliance. It is recommended that the system including the chamber be designed
so that there are no places where air bubbles can hide and that the liquid can be refilled
easily. It is necessary that special care be taken not to introduce air bubbles when the test
piece is mounted and removed.
The material of the chamber should be chosen considering the pressure media for the test,
testing pressure range, measurement temperature range and interference with the electrical
measurements.
In case liquid is used to pressurize the test system, it is recommended that the testing
apparatus be made out of transparent plexiglass (polymethyl methacrylate) in order to see air
bubbles and then to minimize them trapped within the chamber.
The pressure chamber is connected to the pressuring device and thus allows a test piece to
be deformed with fine control. The test piece is mounted on the pressure chamber by
mechanical clamping or the epoxy gluing method, etc.
NOTE In the case of a capacitance measurement type, the pressure chamber has an electrode and a mechanical
spacer. The electrode, which measures the height change of a test specimen due to deformation, is made of Cu-
coated polychlorinated biphenyl (PCB). A mechanical spacer that is located between the specimen and the
electrode controls a sensitivity of capacitance change by adjusting the thickness of the spacer.
The pressure inside the chamber shall be monitored and measured through a suitable
pressure sensor, which can be installed directly in the chamber or connected though the tube
transporting the pressure without loss of the pressure to be measured.
It is recommended that exposition of the area of the pressure sensor to the pressure media be
minimized and that the area have no indentation or internal cavities tr
...