ISO 16700:2016

Microbeam analysis - Scanning electron microscopy - Guidelines for calibrating image magnification

ISO 16700:2016 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. It does not apply to the dedicated critical dimension measurement SEM.

Analyse par microfaisceaux — Microscopie électronique à balayage — Lignes directrices pour l'étalonnage du grandissement d'image

General Information

• Status: Published
• Publication Date: 17-Jul-2016
• ICS: 37.020 - Optical equipment
• Technical Committee: ISO/TC 202/SC 4 - Scanning electron microscopy
• Drafting Committee: ISO/TC 202/SC 4 - Scanning electron microscopy
• Current Stage: 9093 - International Standard confirmed
• Start Date: 23-Nov-2023
• Completion Date: 13-Dec-2025

Relations

• Revises: ISO 16700:2004 - Microbeam analysis - Scanning electron microscopy - Guidelines for calibrating image magnification
• Effective Date: 23-Nov-2013

Overview

ISO 16700:2016 - Microbeam analysis - Scanning electron microscopy - Guidelines for calibrating image magnification provides a standardized method to calibrate the image magnification of a scanning electron microscope (SEM) using an appropriate reference material (RM) or certified reference material (CRM). The method is limited by the size range (pitch patterns) available on the reference material and does not apply to dedicated critical-dimension (CD) SEMs. The standard emphasizes metrological traceability, scale markers, and reporting of calibration results and uncertainties.

Key topics and requirements

• Scale marker and magnification expression
  • Superimpose a scale marker on SEM images and express lengths in SI units.
  • Magnification may be shown (e.g., 10 000×) but the scale marker is the definitive indicator for measurement.
• Reference material (RM/CRM)
  • Prefer CRMs produced/certified per ISO Guides (where possible).
  • CRM requirements include stability under vacuum and electron beam, good contrast, electrical conductivity, cleanability, and a valid calibration certificate.
  • Pitch patterns on CRMs determine the usable magnification range.
• Calibration procedures
  • Mounting of CRM and controlled SEM operating conditions (working distance, tilt, beam parameters).
  • Image recording, measurement of features on images, and calculation/adjustment of magnification and scale markers.
• Accuracy and uncertainty
  • Evaluate accuracy (trueness) and quantify measurement uncertainty; annexes cover uncertainty estimation and influencing parameters.
• Documentation
  • Produce a calibration report describing conditions, results, uncertainties, and traceability.

Applications

• Routine SEM magnification calibration in research, quality control, materials characterization, failure analysis, and microstructure studies.
• Ensuring quantitative image measurements (lengths, pitches) are traceable and accurate for standards-compliant testing.
• Useful for labs preparing images for publication, certification, regulatory compliance, or cross-laboratory comparison.

Who should use this standard

• SEM operators and laboratory managers responsible for instrument calibration and quality assurance.
• Calibration and testing laboratories seeking compliance with ISO/IEC 17025 and metrological traceability.
• Producers and users of reference materials (RM/CRM) for SEM magnification.

Related standards

• ISO Guide 30, ISO Guide 34, ISO Guide 35 (reference material production and certification)
• ISO 5725-1 (accuracy)
• ISO/IEC 17025 (laboratory competence)
• ISO/IEC Guide 98-3 (GUM-uncertainty of measurement)

Keywords: ISO 16700:2016, SEM magnification calibration, scanning electron microscope, CRM, reference material, scale marker, calibration report, measurement uncertainty.

Standards Content (Sample)

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
THIS DOCUMENT IS A DRAFT CIRCULATED
FOR COMMENT AND APPROVAL. IT IS
THEREFORE SUBJECT TO CHANGE AND MAY
NOT BE REFERRED TO AS AN INTERNATIONAL
STANDARD UNTIL PUBLISHED AS SUCH.
IN ADDITION TO THEIR EVALUATION AS
BEING ACCEPTABLE FOR INDUSTRIAL,
TECHNOLOGICAL, COMMERCIAL AND
USER PURPOSES, DRAFT INTERNATIONAL
STANDARDS MAY ON OCCASION HAVE TO
BE CONSIDERED IN THE LIGHT OF THEIR
POTENTIAL TO BECOME STANDARDS TO
WHICH REFERENCE MAY BE MADE IN
Reference number
NATIONAL REGULATIONS.
ISO/DIS 16700:2015(E)
RECIPIENTS OF THIS DRAFT ARE INVITED
TO SUBMIT, WITH THEIR COMMENTS,
NOTIFICATION OF ANY RELEVANT PATENT
RIGHTS OF WHICH THEY ARE AWARE AND TO
©
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
© ISO 2015, Published in Switzerland
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized otherwise in any form
or by any means, electronic or mechanical, including photocopying, or posting on the internet or an intranet, without prior
written permission. Permission can be requested from either ISO at the address below or ISO’s member body in the country of
the requester.
ISO copyright office
Ch. de Blandonnet 8 • CP 401
CH-1214 Vernier, Geneva, Switzerland
Tel. [phone]
Fax [phone]
[e-mail]
www.iso.org
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
declarations received. www.iso.org/patents
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation on the meaning of ISO specific terms and expressions related to conformity assessment, as
well as information about ISO's adherence to the WTO principles in the Technical Barriers to Trade (TBT) see
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
...

INTERNATIONAL ISO
STANDARD 16700
Second edition
2016-08-01
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
Reference number
©
ISO 2016
© ISO 2016, Published in Switzerland
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized otherwise in any form
or by any means, electronic or mechanical, including photocopying, or posting on the internet or an intranet, without prior
written permission. Permission can be requested from either ISO at the address below or ISO’s member body in the country of
the requester.
ISO copyright office
Ch. de Blandonnet 8 • CP 401
CH-1214 Vernier, Geneva, Switzerland
Tel. [phone]
Fax [phone]
[e-mail]
www.iso.org
ii © ISO 2016 – All rights reserved

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 . 3
5.1 General . 3
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
6.6.1 General. 7
6.6.2 Magnification . 7
6.6.3 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 .11
Annex B (informative) Parameters that influence the resultant magnification of an SEM .13
Annex C (informative) Uncertainties in magnification measurements .15
Annex D (informative) Example of a test report .16
Bibliography .18
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 (see 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 declarations received (see www.iso.org/patents).
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation on the meaning of ISO specific terms and expressions related to conformity assessment,
as well as information about ISO’s adherence to the World Trade Organization (WTO) principles in the
Technical Barriers to Trade (TBT) see the following URL: www.iso.org/iso/foreword.html.
The committee responsible for this document is ISO/TC 202, Microbeam analysis, Subcommittee SC 4,
Scanning electron microscopy (SEM).
This second edition cancels and replaces the first edition (ISO 16700:2004), which has been technically
revised.
iv © ISO 2016 – All rights reserved

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 16700:2016(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 documents, in whole or in part, are normatively referenced in this document and are
indispensable for its application. For dated references, only the edition cited applies. For undated
references, the latest edition of the referenced document (including any amendments) applies.
ISO/IEC 17025:2005, General requirements for the competence of testing and calibration laboratories
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
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 (3.1)
Note 1 to entry: 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
3.4
scale marker
line/generated line (intervals) on the image (3.2) 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 (3.5) 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 1 to entry: For the purposes of this International Standard, 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 (3.3).
3.7
calibration
set of operations which establish, under specified conditions, the relationship between the magnification
indicated by the SEM (3.1) and the corresponding magnification determined by examination of an RM
(3.5) or a CRM (3.6)
3.8
tilt angle
angle of the inclined specimen surface from the plane perpendicular to the electron beam axis
Note 1 to entry: See Figure 1.
Key
1 tilted specimen
2 electron beam
3 specimen
4 tilt angle
Figure 1 — Tilt angle
3.9
display
analog or digital device used for visualization of images (3.2)
Note 1 to entry: 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 (3.1)
3.11
pitch
closest separation of two similar features on a specimen which are equivalent points on a repeat pattern
2 © ISO 2016 – All rights reserved

3.12
accuracy
closeness of agreement between a test result and the accepted reference value
Note 1 to entry: A “test result” constitutes the observed values of a pitch (3.11) of a CRM (3.6) obtained by the
procedure outlined in this International Standard.
Note 2 to entry: 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 to entry: 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.
NOTE In Figure 2, the length indicated by the arrows corresponds to 500 nm after the calibration.
Figure 2 — Scale marker and its length
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, × 10k,
where 100, 10 000 and 10k are magnitude numbers).
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.
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, and
— 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 There are cases where the CRM contains 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. In some cases, the CRM additionally contains other structures for testing image distortion and/or
resolution.
NOTE 2 There are instances where the chosen CRM has different-sized pitch patterns to cover the whole range
of magnifications for which calibration is needed. It can 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 can 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.
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.
4 © ISO 2016 – All rights reserved

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 instructions so that CRM surface is perpendicular
to the electron beam axis during operation.
Check the tilt of the CRM by the following procedures.
a) Turn off the tilt angle correction, the scan rotation and the zoom control of the magnification.
b) Select the imaging mode (secondary electron and/or back scattered electron).
c) Bring the image into focus without visible stigmatic distortions in the image.
d) Select the magnification at which the entire area of measurement is visible.
e) Determine the tilt position where the measured value of pitch is maximum. If the difference of
measured values is not found, assume that the tilt angle is 0°. Carry out subsequent recording of the
image in this position.
NOTE 1 If the image of the whole area cannot be brought into focus, then it is necessary to remount the
CRM or readjust the mechanical alignment of the SEM.
f) Select the accelerating voltage and the working distance for which the calibration is to be performed
and bring the CRM into the correct position using the specimen stage controls.
g) Wait until the instrument is fully stabilized at the desired operating conditions in accorda
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