ISO 16700:2016

DRAFT INTERNATIONAL STANDARD
ISO/DIS 16700
ISO/TC 202/SC 4 Secretariat: JISC
Voting begins on: Voting terminates on:
2015-09-17 2015-12-16
Microbeam analysis — Scanning electron microscopy —
Guidelines for calibrating image magnification
Analyse par microfaisceaux — Microscopie électronique à balayage — Lignes directrices pour l’étalonnage
du grandissement d’image
ICS: 37.020
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ISO/DIS 16700:2015(E)
RECIPIENTS OF THIS DRAFT ARE INVITED
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NOTIFICATION OF ANY RELEVANT PATENT
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PROVIDE SUPPORTING DOCUMENTATION. ISO 2015

ISO/DIS 16700:2015(E) ISO/DIS 16700:2015(E)

Contents Page
Foreword . iv
Introduction . v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Image magnification . 3
4.1 Scale marker . 3
4.2 Expressing magnification . 3
5 Reference material . 4
5.1 General . 4
5.2 Requirements for CRM . 4
5.3 Pitch patterns on CRM . 4
5.4 Storage and handling . 4
6 Calibration procedures . 5
6.1 General . 5
6.2 Mounting CRM . 5
6.3 Setting SEM operation conditions for calibration . 5
6.4 Image recording . 6
6.5 Measurement of image . 6
6.6 Calibration of magnification and scale marker . 7
7 Accuracy of image magnification and scale marker . 8
8 Calibration report . 9
8.1 General . 9
8.2 Contents of calibration report . 9
Annex A (informative) Reference materials for magnification . 10
Annex B (informative) Parameters that influence the resultant magnification of an SEM . 12
Annex C (informative) Uncertainties in magnification measurements . 14
Annex D (informative) Example of a test report . 15

Bibliography …………………………………………………………………………………………………………….17
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ii © ISO 2015 – All rights reserved
ISO/DIS 16700:2015(E)
Contents Page
Foreword . iv
Introduction . v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Image magnification . 3
4.1 Scale marker . 3
4.2 Expressing magnification . 3
5 Reference material . 4
5.1 General . 4
5.2 Requirements for CRM . 4
5.3 Pitch patterns on CRM . 4
5.4 Storage and handling . 4
6 Calibration procedures . 5
6.1 General . 5
6.2 Mounting CRM . 5
6.3 Setting SEM operation conditions for calibration . 5
6.4 Image recording . 6
6.5 Measurement of image . 6
6.6 Calibration of magnification and scale marker . 7
7 Accuracy of image magnification and scale marker . 8
8 Calibration report . 9
8.1 General . 9
8.2 Contents of calibration report . 9
Annex A (informative) Reference materials for magnification . 10
Annex B (informative) Parameters that influence the resultant magnification of an SEM . 12
Annex C (informative) Uncertainties in magnification measurements . 14
Annex D (informative) Example of a test report . 15

Bibliography …………………………………………………………………………………………………………….17
ISO/DIS 16700:2015(E)
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies
(ISO member bodies). The work of preparing International Standards is normally carried out through ISO
technical committees. Each member body interested in a subject for which a technical committee has been
established has the right to be represented on that committee. International organizations, governmental and
non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the International
Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are described in
the ISO/IEC Directives, Part 1. In particular the different approval criteria needed for the different types of ISO
documents should be noted. This document was drafted in accordance with the editorial rules of the ISO/IEC
Directives, Part 2. www.iso.org/directives
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of any patent rights
identified during the development of the document will be in the Introduction and/or on the ISO list of patent
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the following URL: Foreword - Supplementary information
The committee responsible for this document is ISO/TC 202.
This second edition cancels and replaces the first edition ISO16700:2004(E).

ISO/DIS 16700:2015(E)
Introduction
The scanning electron microscope is widely used to investigate the surface structure of a range of important
materials such as semiconductors, metals, polymers, glass, food and biological materials and this International
Standard is relevant to the need for magnification calibration of the images. It describes the requirements for
calibration of the image magnification in the scanning electron microscope using a reference material or a
certified reference material.
INTERNATIONAL STANDARD ISO/DIS 16700 :2015(E)

Microbeam analysis — Scanning electron microscopy —
Guidelines for calibrating image magnification
1 Scope
This International Standard specifies a method for calibrating the magnification of images generated by a
scanning electron microscope (SEM) using an appropriate reference material. This method is limited to
magnifications determined by the available size range of structures in the calibrating reference material. This
International Standard does not apply to the dedicated critical dimension measurement SEM.
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.
ISO Guide 30, Reference materials — Selected terms and definitions
ISO Guide 34, General requirements for the competence of reference material producers
ISO Guide 35, Reference materials -- General and statistical principles for certification
ISO 5725-1, Accuracy (trueness and precision) of measurement methods and results — Part 1: General principles
and definitions
ISO/IEC 17025, General requirements for the competence of testing and calibration laboratories
ISO/IEC Guide 98-3, Uncertainty of measurement – Part 3: Guide to the expression of uncertainty in measurement
(GUM: 1995)
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1
scanning electron microscope (SEM)
instrument that produces magnified images of a specimen by scanning its surface with an electron beam
3.2
image
two-dimensional representation of the specimen surface generated by SEM
NOTE A photograph of a specimen taken using an SEM is a good example of an image.
3.3
image magnification
ratio of the linear dimension of the scan display to the corresponding linear dimension of the specimen scan
field
ISO/DIS 16700:2015(E)
3.4
scale marker
line / generated line (intervals) on the image representing a designated actual length in the specimen
3.5
reference material (RM)
material, sufficiently homogeneous and stable with respect to one or more specified properties, which has been
established to be fit for its intended use in a measurement process
3.6
certified reference material (CRM)
reference material characterized by a metrologically valid procedure for one or more specified properties,
accompanied by a certificate that provides the value of the specified property, its associated uncertainty, and a
statement of metrological traceability
NOTE For the purposes of this document, an RM/CRM possesses pitch pattern(s) with the desired range of pitch
size(s) and accuracy, to be used for the calibration of the image magnification.
3.7
calibration
set of operations which establish, under specified conditions, the relationship between the magnification
indicated by the SEM and the corresponding magnification determined by examination of an RM or a CRM
3.8
tilt angle
angle of the inclined specimen surface from the plane perpendicularly to the electron beam axis
See Figure 1.
Key
1 tilted specimen
2 electron beam
3 specimen
4 tilt angle
Figure 1 — Tilt angle
ISO/DIS 16700:2015(E)
3.9
display
analog or digital device used for visualization of images
NOTE Examples of display are a cathode ray tube, plasma display panel, liquid crystal display, etc.
3.10
working distance
distance between the specimen surface and the bottom plane of the objective lens of the SEM
3.11
pitch
closest separation of two similar features on a specimen which are equivalent points on a repeat pattern
3.12
accuracy
the closeness of agreement between a test result and the accepted reference value
[ISO 5725-1:1994]
NOTE 1 A ―test result‖ constitutes the observed values of a pitch of a CRM obtained by the procedure outlined in this
International Standard.
NOTE 2 The term ―accepted reference value‖ is a value certified by a national or an international calibrating laboratory.
There will be an uncertainty associated with this value which should also appear on the certificate.
NOTE 3 Accuracy and precision are different. Precision is defined as the closeness of agreement between independent
test results obtained under stipulated conditions. See ISO 5725-1.
4 Image magnification
4.1 Scale marker
To indicate magnification, superimpose on the image a scale marker and the corresponding length, in SI units,
that it actually represents on the specimen. An example is shown in Figure 2.
500 nm 500 nm
Figure 2 — Scale marker and its length
NOTE In Figure 2, the length indicated by the arrows corresponds to 500 nm after the calibration.
4.2 Expressing magnification
Magnification of an image is given by a number representing the number of times the object has been
magnified and it is accompanied by the symbol ―‖ (e.g. 100 , 10 000 , 10k  or  100,  10 000,  10 k
where 100, 10 000 and 10 k are magnitude numbers). See Annex A.
NOTE 1 It is not always necessary to show the magnification when the scale marker is shown on the image.
NOTE 2 The magnification shown on the image corresponds to a chosen output device, which can be a display monitor
or a printer or a photographing device. The scale marker shown on the image is independent from the output device chosen
by the operator of the SEM. The magnification shown corresponds to the scale marker only when the image is displayed or
printed on the operator-chosen output device.
ISO/DIS 16700:2015(E)
5 Reference material
5.1 General
See ISO Guide 30.
For calibrating the magnification of an image, wherever possible, choose a CRM that is produced in
accordance with ISO Guide 34 and certified in accordance with ISO Guide 35.
When a suitable CRM is not available, an RM produced in accordance with ISO Guide 34 may be used.
5.2 Requirements for CRM
Ensure that the chosen CRM:
 is stable with respect to vacuum and repeated electron beam exposure;
 provides good contrast in the SEM image;
 is electrically conductive;
 can be cleaned to remove contamination occurring during normal use without causing mechanical damage
or distortion;
 has an associated valid calibration certificate.
5.3 Pitch patterns on CRM
Pitch patterns on the CRM may be in any one or more of the following forms:
 an orthogonal cross grid;
 a line array;
 a dot array;
 an orthogonal dot array.
Ensure that the chosen CRM contains pitch patterns that allow for calibration in at least one direction, and that
the uncertainty in the pitch patterns is consistent with the targeted accuracy.
NOTE 1 The CRM may contain pitch patterns both in X and Y directions so that the measurements can be performed in
orthogonal directions without the necessity of mechanically rotating the CRM. The CRM may additionally contain other
structures for testing image distortion and/or resolution.
NOTE 2 The chosen CRM may have different sized pitch patterns to cover the whole range of magnifications for which
calibration is needed. It may also be necessary to have more than one CRM to cover the desired range of magnifications.
5.4 Storage and handling
Store the CRM in a desiccating cabinet or in a vacuum container.
NOTE To ensure minimal handling of the actual CRM, it may be permanently mounted on a stub.
Handle the CRM using fingerstalls, clean room gloves or tweezers.
Visually inspect the CRM surface for contamination and deterioration, as this may affect calibration. Do not use
the CRM if it is damaged or grossly contaminated.
ISO/DIS 16700:2015(E)
Remove any dust, loose debris or other contamination from the CRM using clean dry air or nitrogen gas, taking
care not to damage the CRM.
Check the calibration of the CRM at intervals by comparison with other CRMs; record the results. The
frequency of verification may depend on the nature and usage of the CRM.
Use the CRM for calibration purposes only.
6 Calibration procedures
6.1 General
Parameters that influence the resultant magnification of an SEM may cause systematic errors. These are listed
in Annex B.
The stability of the SEM will be a major factor in determining the calibration interval. Initially it will be necessary
to perform calibration at frequent intervals in order to verify that the SEM is stable.
The results obtained will provide an estimate of the reproducibility within the laboratory and the bias inherent in
both the display and the data automatically superimposed on any output.
The selection of the CRM depends on the magnification being used and accuracy required. For the purposes of
this International Standard, ensure that the accuracy of calibration is better than 10 %.
6.2 Mounting CRM
At the time of mounting the specimen, ensure that handling of the CRM is carried out in accordance with 5.4.
Mount the CRM in accordance with the SEM and the CRM manufacturer‘s instructions.
Ascertain that there is a good electrical contact between the CRM and the specimen stage of the SEM.
Check that the CRM is securely fixed on the specimen stage so that it does not move from its mounting. This
enables one to minimize any image degradation caused by vibration.
6.3 Setting SEM operation conditions for calibration
Evacuate the specimen chamber to the working vacuum in accordance with the SEM manufacturer‘s
instructions.
Optimize the electron beam brightness and alignment in accordance with the SEM manufacturer‘s instructions.
Set tilt angle to 0 following the SEM manufacturer‘s inst
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