Surface chemical analysis — Secondary ion mass spectrometry — Calibration of the mass scale for a time-of-flight secondary ion mass spectrometer

This document specifies a method to optimize the mass calibration accuracy in time-of-flight secondary ion mass spectrometry (SIMS) instruments used for general analytical purposes. It is only applicable to time-of-flight instruments but is not restricted to any particular instrument design. Guidance is provided for some of the instrumental parameters that can be optimized using this procedure and the types of generic peaks suitable to calibrate the mass scale for optimum mass accuracy.

Analyse chimique des surfaces — Spectrométrie de masse des ions secondaires — Étalonnage de l'échelle de masse pour un spectromètre de masse des ions secondaires à temps de vol

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Published
Publication Date
14-Nov-2018
Current Stage
9092 - International Standard to be revised
Completion Date
16-Sep-2024
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INTERNATIONAL ISO
STANDARD 13084
Second edition
2018-11
Surface chemical analysis —
Secondary ion mass spectrometry
— Calibration of the mass scale for
a time-of-flight secondary ion mass
spectrometer
Analyse chimique des surfaces — Spectrométrie de masse des ions
secondaires — Étalonnage de l'échelle de masse pour un spectromètre
de masse des ions secondaires à temps de vol
Reference number
©
ISO 2018
© ISO 2018
All rights reserved. Unless otherwise specified, or required in the context of its implementation, 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
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: +41 22 749 01 11
Fax: +41 22 749 09 47
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland
ii © ISO 2018 – All rights reserved

Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Symbols and abbreviated terms . 1
4.1 Symbols . 1
4.2 Abbreviated terms . 2
5 Outline of method . 2
6 Method for improving mass accuracy . 3
6.1 Obtaining the reference sample for optimization . 3
6.2 Preparation of polycarbonate sample . 4
6.3 Obtaining the SIMS spectral data . 4
6.4 Calculating mass accuracy . 5
6.5 Optimizing instrumental parameters . 7
6.6 Calibration procedure . 9
Annex A (informative) Calibration uncertainty .11
Annex B (informative) Internal addition method .13
Bibliography .15
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 of the voluntary nature of standards, 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 www .iso
.org/iso/foreword .html.
This document was prepared by Technical Committee ISO/TC 201, Surface chemical analysis,
Subcommittee SC 6, Secondary ion mass spectrometry.
This second edition cancels and replaces the first edition (ISO 13084:2011), which has been technically
revised.
The main changes to the previous edition are as follows:
— addition of Annex B (informative), Internal addition method.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www .iso .org/members .html.
iv © ISO 2018 – All rights reserved

Introduction
Secondary ion mass spectrometry (SIMS) is a powerful technique for the analysis of organic and
molecular surfaces. Over the last decade, instrumentation has improved significantly so that modern
[2]
instruments now have very high repeatability and constancy . An increasing requirement is for the
identification of the chemical composition of complex molecules from accurate measurements of the
mass of the secondary ions. The relative mass accuracy to do this and to distinguish between molecules
that contain different chemical constituents, but are of the same nominal mass (rounded to the nearest
integer mass), is thus an important parameter. A relative mass accuracy of better than 10 ppm is
required to distinguish between C H (28,031 30 u) and Si (27,976 92 u) in a parent ion with total mass
2 4
up to 1 000 u, and between CH (14,015 65 u) and N (14,003 07 u) in parent ions with total mass up to
[3]
300 u. However, in a recent interlaboratory study , the average fractional mass accuracy was found
to be 150 ppm. This is significantly worse than is required for unambiguous identification of ions. A
[4]
detailed study shows that the key factors degrading the accuracy include the large kinetic energy
distribution of secondary ions, non-optimized instrument parameters and extrapolation of the mass
scale calibration.
This document describes a simple method, using locally sourced material, to optimize the instrumental
parameters, as well as a procedure to ensure that accurate calibration of the mass scale is achieved
within a selectable uncertainty.
INTERNATIONAL STANDARD ISO 13084:2018(E)
Surface chemical analysis — Secondary ion mass
spectrometry — Calibration of the mass scale for a time-of-
flight secondary ion mass spectrometer
1 Scope
This document specifies a method to optimize the mass calibration accuracy in time-of-flight secondary
ion mass spectrometry (SIMS) instruments used for general analytical purposes. It is only applicable
to time-of-flight instruments but is not restricted to any particular instrument design. Guidance is
provided for some of the instrumental parameters that can be optimized using this procedure and the
types of generic peaks suitable to calibrate the mass scale for optimum mass accuracy.
2 Normative references
There are no normative references in this document.
3 Terms and definitions
No terms and definitions are listed in this document.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https: //www .iso .org/obp
— IEC Electropedia: available at http: //www .electropedia .org/
4 Symbols and abbreviated terms
4.1 Symbols
m mass of interest
m calibration mass 1
m calibration mass 2
M mass (u)
M the peak centre (u)
ΔM mass accuracy (u)
M measured peak mass (u)
P
M true mass (u)
T
U(m) mass uncertainty for a mass, m, arising from calibration
U uncertainty in the accurate mass measurement of m
1 1
U uncertainty in the accurate mass measurement of m
2 2
U average uncertainty in an accurate mass measurement
V reflector or acceptance voltage (V)
R
W relative mass accuracy
x number of carbon atoms
y number of hydrogen atoms
G scaling term
α asymmetry term
σ(ΔM) standard deviation of the mass accuracy for a number of peaks
+
σ average of the standard deviations of ΔM for each of the four C H cascades with 4, 6, 7 and
M x y
8 carbon atoms
4.2 Abbreviated terms
MEMS micro-electromechanical system
PC polycarbonate
ppm parts per million
r/min revolutions per minute
SIMS secondary ion mass spectrometry
THF tetrahydrofuran
ToF time-of-flight
5 Outline of method
Here, the method is outlined so that the detailed procedure, given in Clause 6, may be understood in
context. Firstly, to optimize a time-of-flight mass spectrometer using this procedure, obtain a thin film
of polycarbonate (PC) on a conducting substrate (silicon). The optimization procedure is achieved by
carrying out the procedures in 6.3 to 6.5 iteratively; it uses 19 specific C H peaks in the PC positive-
x y
ion mass spectrum. In 6.6, a general calibration procedure is given which provides the rules by which
calibrations for inorganics and organics may be incorporated. This leads to a new generic set of ions
for mass calibration that can improve the mass accuracy from some often-used calibrations by a factor
of five. The effects of extrapolation beyond the calibration range are discussed and a recommended
procedure is given to ensure that accurate mass is achieved, within a selectable uncertainty, for large
molecules. Therefore, the procedure has two parts, optimization and calibration. 6.1 to 6.5 are only
required as part of the regular maintenance of the instrument as defined by the testing laboratory. 6.6
is required for all calibrations of the mass scale. This is summarized in the flowchart in Figure 1.
2 © ISO 2018 – All rights reserved

Figure 1 — Flowchart of sequence of operations of the method
6 Method for improving mass accuracy
6.1 Obtaining the reference sample for optimization
A sample of thin (10 to 100 nm) PC on a flat conducting substrate (e.g. silicon wafer) shall either be
obtained or prepared, as described in 6.2.
6.2 Preparation of polycarbonate sample
6.2.1 Instructions for the preparation of a PC reference sample are provided. This method can give
[2]
sample-to-sample repeatability in ToF SIMS spectra of better than 1,9 % . To prepare such a sample
for static SIMS analysis requires a clean working environment. To reduce surface contamination, clean
glassware, tweezers and powderless gloves shall be used. The equipment required is a 1 ml glass pipette,
a 100 ml glass-stoppered measuring flask and a device for spin casting. If a device for spin casting is not
available, droplet deposition of the PC solution may be used. However, this will give poor repeatability,
which will need to be carefully taken into account during spectral analysis.
6.2.2 Using poly(bisphenol A carbonate), abbreviated to PC, weigh out 100 mg on a clean piece of
aluminium foil. Introduce the PC into the 100 ml, glass-stoppered measuring flask, add tetrahydrofuran
(THF) of analytical reagent quality to the 100 ml level line. Shake the flask to mix the PC and allow time to
dissolve it completely. This produces a 1 mg/ml solution of PC in THF. The aluminium foil shall be freshly
unrolled and the shiny surface used. Ensure that the THF is anhydrous, otherwise streaks will appear
from water when spin coating, as described in 6.2.3. The shelf life of freshly prepared stock solution shall
be no more than one month owing to water take-up.
NOTE 1 It does not matter if the PC contains low levels of additives.
NOTE 2 It does not matter if the final PC/THF solution concentration var
...


INTERNATIONAL ISO
STANDARD 13084
Second edition
2018-11
Surface chemical analysis —
Secondary ion mass spectrometry
— Calibration of the mass scale for
a time-of-flight secondary ion mass
spectrometer
Analyse chimique des surfaces — Spectrométrie de masse des ions
secondaires — Étalonnage de l'échelle de masse pour un spectromètre
de masse des ions secondaires à temps de vol
Reference number
©
ISO 2018
© ISO 2018
All rights reserved. Unless otherwise specified, or required in the context of its implementation, 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
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: +41 22 749 01 11
Fax: +41 22 749 09 47
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland
ii © ISO 2018 – All rights reserved

Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Symbols and abbreviated terms . 1
4.1 Symbols . 1
4.2 Abbreviated terms . 2
5 Outline of method . 2
6 Method for improving mass accuracy . 3
6.1 Obtaining the reference sample for optimization . 3
6.2 Preparation of polycarbonate sample . 4
6.3 Obtaining the SIMS spectral data . 4
6.4 Calculating mass accuracy . 5
6.5 Optimizing instrumental parameters . 7
6.6 Calibration procedure . 9
Annex A (informative) Calibration uncertainty .11
Annex B (informative) Internal addition method .13
Bibliography .15
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 of the voluntary nature of standards, 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 www .iso
.org/iso/foreword .html.
This document was prepared by Technical Committee ISO/TC 201, Surface chemical analysis,
Subcommittee SC 6, Secondary ion mass spectrometry.
This second edition cancels and replaces the first edition (ISO 13084:2011), which has been technically
revised.
The main changes to the previous edition are as follows:
— addition of Annex B (informative), Internal addition method.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www .iso .org/members .html.
iv © ISO 2018 – All rights reserved

Introduction
Secondary ion mass spectrometry (SIMS) is a powerful technique for the analysis of organic and
molecular surfaces. Over the last decade, instrumentation has improved significantly so that modern
[2]
instruments now have very high repeatability and constancy . An increasing requirement is for the
identification of the chemical composition of complex molecules from accurate measurements of the
mass of the secondary ions. The relative mass accuracy to do this and to distinguish between molecules
that contain different chemical constituents, but are of the same nominal mass (rounded to the nearest
integer mass), is thus an important parameter. A relative mass accuracy of better than 10 ppm is
required to distinguish between C H (28,031 30 u) and Si (27,976 92 u) in a parent ion with total mass
2 4
up to 1 000 u, and between CH (14,015 65 u) and N (14,003 07 u) in parent ions with total mass up to
[3]
300 u. However, in a recent interlaboratory study , the average fractional mass accuracy was found
to be 150 ppm. This is significantly worse than is required for unambiguous identification of ions. A
[4]
detailed study shows that the key factors degrading the accuracy include the large kinetic energy
distribution of secondary ions, non-optimized instrument parameters and extrapolation of the mass
scale calibration.
This document describes a simple method, using locally sourced material, to optimize the instrumental
parameters, as well as a procedure to ensure that accurate calibration of the mass scale is achieved
within a selectable uncertainty.
INTERNATIONAL STANDARD ISO 13084:2018(E)
Surface chemical analysis — Secondary ion mass
spectrometry — Calibration of the mass scale for a time-of-
flight secondary ion mass spectrometer
1 Scope
This document specifies a method to optimize the mass calibration accuracy in time-of-flight secondary
ion mass spectrometry (SIMS) instruments used for general analytical purposes. It is only applicable
to time-of-flight instruments but is not restricted to any particular instrument design. Guidance is
provided for some of the instrumental parameters that can be optimized using this procedure and the
types of generic peaks suitable to calibrate the mass scale for optimum mass accuracy.
2 Normative references
There are no normative references in this document.
3 Terms and definitions
No terms and definitions are listed in this document.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https: //www .iso .org/obp
— IEC Electropedia: available at http: //www .electropedia .org/
4 Symbols and abbreviated terms
4.1 Symbols
m mass of interest
m calibration mass 1
m calibration mass 2
M mass (u)
M the peak centre (u)
ΔM mass accuracy (u)
M measured peak mass (u)
P
M true mass (u)
T
U(m) mass uncertainty for a mass, m, arising from calibration
U uncertainty in the accurate mass measurement of m
1 1
U uncertainty in the accurate mass measurement of m
2 2
U average uncertainty in an accurate mass measurement
V reflector or acceptance voltage (V)
R
W relative mass accuracy
x number of carbon atoms
y number of hydrogen atoms
G scaling term
α asymmetry term
σ(ΔM) standard deviation of the mass accuracy for a number of peaks
+
σ average of the standard deviations of ΔM for each of the four C H cascades with 4, 6, 7 and
M x y
8 carbon atoms
4.2 Abbreviated terms
MEMS micro-electromechanical system
PC polycarbonate
ppm parts per million
r/min revolutions per minute
SIMS secondary ion mass spectrometry
THF tetrahydrofuran
ToF time-of-flight
5 Outline of method
Here, the method is outlined so that the detailed procedure, given in Clause 6, may be understood in
context. Firstly, to optimize a time-of-flight mass spectrometer using this procedure, obtain a thin film
of polycarbonate (PC) on a conducting substrate (silicon). The optimization procedure is achieved by
carrying out the procedures in 6.3 to 6.5 iteratively; it uses 19 specific C H peaks in the PC positive-
x y
ion mass spectrum. In 6.6, a general calibration procedure is given which provides the rules by which
calibrations for inorganics and organics may be incorporated. This leads to a new generic set of ions
for mass calibration that can improve the mass accuracy from some often-used calibrations by a factor
of five. The effects of extrapolation beyond the calibration range are discussed and a recommended
procedure is given to ensure that accurate mass is achieved, within a selectable uncertainty, for large
molecules. Therefore, the procedure has two parts, optimization and calibration. 6.1 to 6.5 are only
required as part of the regular maintenance of the instrument as defined by the testing laboratory. 6.6
is required for all calibrations of the mass scale. This is summarized in the flowchart in Figure 1.
2 © ISO 2018 – All rights reserved

Figure 1 — Flowchart of sequence of operations of the method
6 Method for improving mass accuracy
6.1 Obtaining the reference sample for optimization
A sample of thin (10 to 100 nm) PC on a flat conducting substrate (e.g. silicon wafer) shall either be
obtained or prepared, as described in 6.2.
6.2 Preparation of polycarbonate sample
6.2.1 Instructions for the preparation of a PC reference sample are provided. This method can give
[2]
sample-to-sample repeatability in ToF SIMS spectra of better than 1,9 % . To prepare such a sample
for static SIMS analysis requires a clean working environment. To reduce surface contamination, clean
glassware, tweezers and powderless gloves shall be used. The equipment required is a 1 ml glass pipette,
a 100 ml glass-stoppered measuring flask and a device for spin casting. If a device for spin casting is not
available, droplet deposition of the PC solution may be used. However, this will give poor repeatability,
which will need to be carefully taken into account during spectral analysis.
6.2.2 Using poly(bisphenol A carbonate), abbreviated to PC, weigh out 100 mg on a clean piece of
aluminium foil. Introduce the PC into the 100 ml, glass-stoppered measuring flask, add tetrahydrofuran
(THF) of analytical reagent quality to the 100 ml level line. Shake the flask to mix the PC and allow time to
dissolve it completely. This produces a 1 mg/ml solution of PC in THF. The aluminium foil shall be freshly
unrolled and the shiny surface used. Ensure that the THF is anhydrous, otherwise streaks will appear
from water when spin coating, as described in 6.2.3. The shelf life of freshly prepared stock solution shall
be no more than one month owing to water take-up.
NOTE 1 It does not matter if the PC contains low levels of additives.
NOTE 2 It does not matter if the final PC/THF solution concentration var
...

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