IEC 62951-7:2019
(Main)Semiconductor devices - Flexible and stretchable semiconductor devices - Part 7: Test method for characterizing the barrier performance of thin film encapsulation for flexible organic semiconductor
Semiconductor devices - Flexible and stretchable semiconductor devices - Part 7: Test method for characterizing the barrier performance of thin film encapsulation for flexible organic semiconductor
IEC 62951-7:2019 specifies evaluation conditions and gives a method of measurement as well as a test set-up for the measurement of barrier performance for thin-film layer with ultra‑low permeation rate under both flat and bending conditions. This document also includes the preparation of specimen, electrical contacts, sensor films and calculation procedures. For these purposes, this document provides terms, definitions, symbols, configurations, and test methods including test conditions such as temperature, relative humidity, testing time.
Dispositifs à semiconducteurs - Dispositifs à semiconducteurs souples et extensibles - Partie 7: Méthode d’essai pour caractériser la performance des barrières en couches minces utilisées pour l’encapsulation des semiconducteurs organiques souples
L’IEC 62951-7:2019 spécifie des conditions d’évaluation et fournit une méthode de mesure ainsi qu’un montage d’essai pour la mesure de performance des barrières en couches minces à vitesse de perméation ultra faible, à la fois à plat et en conditions de flexion. Le présent document comprend également la préparation de l’éprouvette, les contacts électriques, les couches de détecteur et les modes opératoires de calcul. A cet effet, le présent document fournit des termes, des définitions, des symboles, des configurations et des méthodes d’essai, y compris des conditions d’essai telles que la température, l’humidité relative et la durée d’essai.
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IEC 62951-7
®
Edition 1.0 2019-02
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Semiconductor devices – Flexible and stretchable semiconductor devices –
Part 7: Test method for characterizing the barrier performance of thin film
encapsulation for flexible organic semiconductor
Dispositifs à semiconducteurs – Dispositifs à semiconducteurs souples et
extensibles –
Partie 7: Méthode d’essai pour caractériser la performance des barrières en
couches minces utilisées pour l’encapsulation des semiconducteurs
organiques souples
IEC 62951-7:2019-02(en-fr)
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IEC 62951-7
®
Edition 1.0 2019-02
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Semiconductor devices – Flexible and stretchable semiconductor devices –
Part 7: Test method for characterizing the barrier performance of thin film
encapsulation for flexible organic semiconductor
Dispositifs à semiconducteurs – Dispositifs à semiconducteurs souples et
extensibles –
Partie 7: Méthode d’essai pour caractériser la performance des barrières en
couches minces utilisées pour l’encapsulation des semiconducteurs
organiques souples
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 31.080.99 ISBN 978-2-8322-6612-0
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® Registered trademark of the International Electrotechnical Commission
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---------------------- Page: 3 ----------------------
– 2 – IEC 62951-7:2019 © IEC 2019
CONTENTS
FOREWORD . 3
1 Scope . 5
2 Normative references . 5
3 Terms and definitions . 5
4 Test method . 6
4.1 General . 6
4.2 Experimental apparatus . 6
4.3 WVTR calculation . 7
4.4 Measurement of Ca resistance . 7
4.5 Application to flexible organic semiconductor devices . 8
4.6 Measurement of barrier performance under the bending condition . 9
5 Test report . 10
Annex A (informative) Sample preparation and data . 12
A.1 Sample preparation . 12
A.2 Measurement data . 12
Bibliography . 14
Figure 1 – Experimental set-up for measuring resistance by the four-wire resistance
measurement method . 6
Figure 2 – Four-wire resistance measurement method for measuring resistance change . 8
Figure 3 – Experimental set-up for measuring resistance by the four-wire resistance
measurement method for flexible substrate . 9
Figure 4 – Experimental set-up for measurement of barrier performance under the
bending condition. 10
Figure A.1 – Example of Ca sensor and its deposition procedures . 12
Figure A.2 – Normalized conductance change as a function of time with linear fit . 13
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IEC 62951-7:2019 © IEC 2019 – 3 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
SEMICONDUCTOR DEVICES –
FLEXIBLE AND STRETCHABLE SEMICONDUCTOR DEVICES –
Part 7: Test method for characterizing the barrier performance of
thin film encapsulation for flexible organic semiconductor
FOREWORD
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International Standard IEC 62951-7 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
47/2533/FDIS 47/2542/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.
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– 4 – IEC 62951-7:2019 © IEC 2019
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.
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.
IMPORTANT – The 'colour inside' logo on the cover page of this publication indicates
that it contains colours which are considered to be useful for the correct
understanding of its contents. Users should therefore print this document using a
colour printer.
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IEC 62951-7:2019 © IEC 2019 – 5 –
SEMICONDUCTOR DEVICES –
FLEXIBLE AND STRETCHABLE SEMICONDUCTOR DEVICES –
Part 7: Test method for characterizing the barrier performance of
thin film encapsulation for flexible organic semiconductor
1 Scope
This part of IEC 62951 specifies evaluation conditions and gives a method of measurement as
well as a test set-up for the measurement of barrier performance for thin-film layer with
ultra-low permeation rate under both flat and bending conditions. This document also includes
the preparation of specimen, electrical contacts, sensor films and calculation procedures. For
these purposes, this document provides terms, definitions, symbols, configurations, and test
methods including test conditions such as temperature, relative humidity, testing time.
2 Normative references
There are no normative references in this document.
3 Terms and definitions
For the purposes of of this document, the following terms and definitions 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
water vapour transmission rate
WVTR
amount of water vapour transmitted through unit area of test specimen per unit time under
specified conditions
2 2
Note 1 to entry: Its unit is generally g/m day or g/(m ⋅24 h) and it means how much water vapour permeates
through a 1 m by 1 m square for 1 day.
[SOURCE: ISO 15106-1:2003, 3.1, modified – the note has been expanded.]
3.2
four-wire resistance measurement
electrical resistance measuring technique that uses separate pairs of current-carrying and
voltage-sensing electrodes to make more accurate measurements than the simpler and more
usual two-terminal sensing
3.3
organic thin film transistor
OTFT
thin film transistor fabricated by using an organic semiconducting material
Note 1 to entry: This note applies to the French language only.
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4 Test method
4.1 General
In the case of organic semiconductor devices, one of the main reliability issues is their
susceptibility to water vapour. Hence, a high performance encapsulation layer is needed to
suppress the ingress of water vapour into devices. The requirement of these barrier layers is
–4 2
less than 10 g/m day to provide enough protection for organic devices such as OTFTs and
organic diodes from the operating environment. Commercially available and published
–3 2 –4
standard for WVTR measurement is only available for a barrier having 10 g/m day or 10
2
g/m day. Hence, this cannot detect the ultra-low permeation of water vapour. This document
covers the measurement method for ultra-low permeation rate and general test set-up. The
WVTR can be measured if the change of resistance of the Ca sensor is measured. In addition,
WVTR under bending conditions needs to be measured for flexible organic electronics.
4.2 Experimental apparatus
Due to the detection limit, the test method based on the infra-red sensor for water vapour
transmission rate in the published standard cannot be applied to barrier layer materials for
organic semiconductors. Ca test is a widely known and used method for measuring ultra-low
permeation rate of the thin-film barriers. Calcium is an electrically conducting and optically
opaque metal which becomes non-conducting and transparent after oxidation by humidity.
Hence, the measurement of Ca conductance or transparency changes provides an indirect
method to determine the oxidation and corrosion rates of Ca induced by permeated water
vapour through the barrier layer. In order to measure the electrical conductance change as a
function of time, the schematics in Figure 1 a) and b) are suggested. Metal electrodes such as
aluminium and Ca sensor are fabricated on the impermeable substrate against water vapour.
The dimension including the thickness of the Ca sensor and electrode shall be changed
according to the applications. The fabrication of each layer is described in Annex A as an
example. The barrier layer which is used to measure WVTR is fabricated on top of the Ca
sensor and electrodes. Figure A.2 in Annex A shows typical conductance change as a
function of time measured in the test set-up illustrated in Figure 1.
a) Side and top view of Ca test cell b) Top view of Ca test cell and
and Al electrical contacts four-wire resistance measurement
Figure 1 – Experimental set-up for measuring resistance by the four-wire resistance
measurement method
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IEC 62951-7:2019 © IEC 2019 – 7 –
4.3 WVTR calculation
By using the experimental set-up described, the change of electrical resistance can be
measured by the four-wire resistance measurement method. An example of data can be found
in Annex A. The WVTR can be determined by monitoring the time rate of change of the
electrical conductance of Ca (data in Figure A.2 in Annex A) through the use of Formula (1)
which has been widely used.
M
dG l HO A
2 Ca
WVTR=nδρ (1)
Ca Ca
dt w M A
Ca w
where
n is the molar equivalent of the reaction (assumed as n = 2);
–8
δ is the calcium resistivity (3,4 × 10 Ω m);
Ca
3
ρ is the calcium density (1,55 g/cm );
Ca
dG
G is the electrical conductance of calcium (the value of in Formula (1) is from the
dt
linear fitting in the conductance change versus time as shown in Figure A.2 in Annex A);
M is the molar mass ( M and M are the molar masses of water vapour and of Ca,
HO
Ca
2
respectively);
l is the length of the calcium sensor;
w is the width of the calcium sensor;
A is the area of the Ca sensor;
ca
A is the area of the window.
w
The ratio of the area of the Ca sensor to the area of the window for water permeation and the
ratio of the length is unity due to the geometry of the experimental set-up.
4.4 Measurement of Ca resistance
In order to measure the electrical conductance change accurately, the four-wire resistance
measurement method is suggested to measure the resistance change, as shown in Figure 2.
The four-wire resistance measurement method is an electrical impedance measuring
technique that uses separate pairs of current-carrying and voltage-sensing electrodes to make
more accurate measurements than the simpler and more usual two-terminal (2T) sensing. Due
to imperceptible change in resistance during the Ca test, the four-wire resistance
measurement method should be used.
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Key
1. resistance of wire;
2. resistance of Ca sensor;
3. volt meter;
4. current source.
Figure 2 – Four-wire resistance measurement method for
measuring resistance change
4.5 Application to flexible organic semiconductor devices
Subclauses 4.2 to 4.4 explain the basic concept of the experimental apparatus for
measurement of permeated water vapour through thin film barrier layer in one direction.
Subclause 4.5 is about the experimental apparatus for measurement of permeated water
vapour through both sides as shown in Figure 3. Due to the limitation of glass substrate to
flexible applications, flexible substrates such as PET (polyethylene terephthalate) have been
widely used. However, most of flexible substrates are permeable to water vapour. Hence, in
order to decrease the amount of permeated water vapour through bottom substrate, a barrier
layer should be deposited on top of the flexible substrate, as illustrated in Figure 3. Water
vapour can permeate through the top barrier layer as well as the bottom flexible substrate
with a barrier layer. The measurement procedure for resistance change is identical to that
described in 4.2 to 4.4.
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IEC 62951-7:2019 © IEC 2019 – 9 –
a) Side and top view of Ca test cell and Al electrical b) Top view of Ca test cell and four-wire
contacts for flexible substrate resistance measurement
Figure 3 – Experimental set-up for measuring resistance by the four-wire resistance
measurement method for flexible substrate
4.6 Measurement of barrier performance under the bending condition
Subclauses 4.2 to 4.5 explain the basic concept of the experimental apparatus for
measurement of permeated water vapour through both the thin film barrier layer and the
flexible substrate. Subclause 4.6 is about the experimental apparatus for measurement of
permeated water vapour through both sides under the bending condition as shown in Figure 4.
Due to the actual application of flexible electronics, the barrier performance needs to be
measured under the bending condition. By using the experimental apparatus described in
Figure 4, the radius of the curvature for the thin film barrier layer can be precisely realized.
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– 10 – IEC 62951-7:2019 © IEC 2019
Key
1 bending radius
2 flexible barrier layer
3 bending test jig
4 Ca sensor
5 bending radius
6 volt meter
7 current source
Figure 4 – Experimental set-up for measurement
of barrier performance under the bending condition
5 Test report
It should be noted that the value of WVTR is significantly dependent on the test environments
such as temperature and relative humidity. Hence, it is noted that the value of WVTR should
be reported with the test environment. In this document, it is suggested that the test should be
carried out either in a controlled environmental chamber or under standard laboratory
conditions. The following information shall be included in the test report:
a) reference to IEC 62951-7
b) the shape and the dimensions of experimental apparatus
• Ca sensor
• electrode
• barrier layer
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IEC 62951-7:2019 © IEC 2019 – 11 –
c) test conditions
• temperature (ambient or environmental chamber)
• relative humidity
• evaluation time
• bending radius of curvature
d) test result
• resistance change as a function of time (or conductance change)
• WVTR
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Annex A
(informative)
Sample preparation and data
A.1 Sample preparation
In order to carry out the experiment for WVTR measurement, the Ca sensor and electrode
should be fabricated. Generally, Ca is oxidized quickly in the air. Hence, it is strongly
suggested that it be fabricated in a vacuum or nitrogen environment. A thermal evaporator for
the fabrication of the Ca and electrode can be used. In the last step, a thin film barrier is
fabricated on top of the buffer layer as illustrated in Figure A.1. As explained in 4.2, the
dimension shall be changed according to the applications. In general, the thickness of the Ca
sensor should be thicker than 20 nm due to its critical thickness. In the case of thickness less
than 20 nm, the sheet resistance of the Ca sensor is too large to detect the change.
Key
1 electrode
2 Ca sensor
3 buffer layer
4 thin-film barrier
a) Ca sensor including electrodes and thin film b) Deposition procedures for each layer
Figure A.1 – Example of Ca sensor and its deposition procedures
A.2 Measurement data
Based on the measurement data of the resistance change of the Ca sensor as a function of
time, WVTR is determined. The accuracy and consistency are critical to determine WVTR.
Figure A.2 shows an example of the change of resistance of the Ca sensor as a function of
time; the measurement was carried out for 800 h. There is no suggestion for evaluation time
but the measurement should be carried out for enough time to get a linear fit. The slope of the
linear fit is significantly dependent on the amount of permeated water vapour. Hence, it
cannot be set in advance about its range.
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IEC 62951-7:2019 © IEC 2019 – 13 –
Figure A.2 – Normalized conductance change as a function of time with linear fit
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Bibliography
IEC 60115-1:2008, Fixed resistors for use in electronic equipment – Part 1: Generic
specification
IEC 60749-39, Semiconductor devices – Mechanical and climatic test methods – Part 39:
Measurement of moisture diffusivity and water solubility in organic materials used for
semiconductor components
1
IEC 62812 , Low resistance measurements – Methods and guidance
ISO 15106-1:2003, Plastics – Film and sheeting – Determination of water vapour transmission
rate - Part 1: Humidity detection sensor method
N. Kim, W. J. Potscavage, Jr., B. Domercq, B. Kippelen, and S. Graham, A hybrid
encapsulation method for organic electronics, Applied Physics Letters, 94, 163-308 (2009)
N Kim, W. J. Potscavage, A. Sundaramoothi, C. Henderson, B. Kippelen, S. Graham, A
correlation study between barrier film performance and shelf lifetime of encapsulated organic
solar cells, Solar Energy Materials & Solar Cells, 101, 140 (2012)
____________
___________
1
Under preparation. Stage at the time of publication: IEC FDIS 62812.
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SOMMAIRE
AVANT-PROPOS . 17
1 Domaine d’application . 19
2 Références normatives . 19
3 Termes et définitions . 19
4 Méthode d’essai . 20
4.1 Généralités . 20
4.2 Appareillage expérimental . 20
4.3 Calcul du CTVE . 21
4.4 Mesure de la résistance du calcium . 22
4.5 Application aux dispositifs à semiconducteurs organiques souples. 22
4.6 Mesure de la performance de la couche de barrière en condition de flexion . 23
5 Rapport d’essai . 24
Annexe A (informative) Préparation de l’échantillon et données . 26
A.1 Préparation de l’échantillon . 26
A.2 Données de mesure . 27
Bibliographie .
...
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