Surface chemical analysis -- Depth profiling -- Method for sputter rate determination in X-ray photoelectron spectroscopy, Auger electron spectroscopy and secondary-ion mass spectrometry sputter depth profiling using single and multi-layer thin films

ISO 17109:2015 specifies a method for the calibration of the sputtered depth of a material from a measurement of its sputtering rate under set sputtering conditions using a single- or multi-layer reference sample with layers of the same material as that requiring depth calibration. The method has a typical accuracy in the range 5 % to 10 % for layers 20 nm to 200 nm thick when sputter depth profiled using AES, XPS, and SIMS. The sputtering rate is determined from the layer thickness and the sputtering time between relevant interfaces in the reference sample and this is used with the sputtering time to give the thickness of the sample to be measured. The determined ion sputtering rate can be used for the prediction of ion sputtering rates for a wide range of other materials so that depth scales and sputtering times in those materials can be estimated through tabulated values of sputtering yields and atomic densities.

Analyse chimique des surfaces -- Profilage d'épaisseur -- Méthode pour la détermination de la vitesse de pulvérisation lors du profilage d'épaisseur par pulvérisation en spectroscopie de photoélectrons par rayons X, spectroscopie d'électrons Auger et spectrométrie de masse des ions secondaires à l'aide de films minces multicouches

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Published
Publication Date
27-Jul-2015
Current Stage
9020 - International Standard under periodical review
Start Date
15-Jul-2020
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ISO 17109:2015 - Surface chemical analysis -- Depth profiling -- Method for sputter rate determination in X-ray photoelectron spectroscopy, Auger electron spectroscopy and secondary-ion mass spectrometry sputter depth profiling using single and multi-layer thin films
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INTERNATIONAL ISO
STANDARD 17109
First edition
2015-08-01
Surface chemical analysis — Depth
profiling — Method for sputter rate
determination in X-ray photoelectron
spectroscopy, Auger electron
spectroscopy and secondary-ion mass
spectrometry sputter depth profiling
using single and multi-layer thin films
Analyse chimique des surfaces — Profilage d’épaisseur — Méthode
pour la détermination de la vitesse de pulvérisation lors du profilage
d’épaisseur par pulvérisation en spectroscopie de photoélectrons par
rayons X, spectroscopie d’électrons Auger et spectrométrie de masse
des ions secondaires à l’aide de films minces multicouches
Reference number
ISO 17109:2015(E)
ISO 2015
---------------------- Page: 1 ----------------------
ISO 17109:2015(E)
COPYRIGHT PROTECTED DOCUMENT
© 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

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ii © ISO 2015 – All rights reserved
---------------------- Page: 2 ----------------------
ISO 17109:2015(E)
Contents Page

Foreword ........................................................................................................................................................................................................................................iv

Introduction ..................................................................................................................................................................................................................................v

1 Scope ................................................................................................................................................................................................................................. 1

2 Normative references ...................................................................................................................................................................................... 1

3 Terms and definitions ..................................................................................................................................................................................... 1

4 Requirement of single- and multi-layer reference thin films ................................................................................ 1

5 Determination of sputtering rate ........................................................................................................................................................ 2

Annex A (informative) Report of international Round Robin Test ........................................................................................ 6

Annex B (informative) Prediction of the rates for a wide range of other materials through

tabulated values of sputtering yields ...........................................................................................................................................15

Bibliography .............................................................................................................................................................................................................................16

© ISO 2015 – All rights reserved iii
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ISO 17109:2015(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 (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 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 201, Surface chemical analysis, Subcommittee

SC 4, Depth profiling.
iv © ISO 2015 – All rights reserved
---------------------- Page: 4 ----------------------
ISO 17109:2015(E)
Introduction

The sputtering rate in surface chemical analysis is generally determined from the quotient of sputtered

depth, measured using stylus profilometry, and sputtering time. However, for multi-layered thin films,

only the average sputtering rate is determined by this method. Therefore, this method is difficult to

apply to multi-layered thin films comprised of materials with different sputtering rates. Sputtering

rates are also affected by various experimental parameters so that it is difficult for them to tabulate and

to be used for sputter depth calibrations. For higher accuracies, it is important for sputtering rates to be

determined under specific experimental conditions for each laboratory for sputter depth calibration.

Sputter rates should be determined using single-layers that are much thicker than the projected range

of the sputtering ions so that the surface transient effect is negligible or by using multi-layered thin

films where the effect of surface transient phenomena can be excluded and interface transients can

be minimized. This International Standard is developed for the calibration of sputtered depth by

determining the ion sputtering rate for depth profiling measurement with Auger electron spectroscopy

(AES), X-ray photoelectron spectroscopy (XPS), and secondary ion mass spectrometry (SIMS) using

single- and multi-layer thin films. The measured ion sputtering rate can be used for the prediction of

ion sputtering rates for a wide range of other materials so that depth scales or sputtering times can be

estimated in day-to-day samples through tabulated values of sputtering yields and bulk densities.

© ISO 2015 – All rights reserved v
---------------------- Page: 5 ----------------------
INTERNATIONAL STANDARD ISO 17109:2015(E)
Surface chemical analysis — Depth profiling — Method
for sputter rate determination in X-ray photoelectron
spectroscopy, Auger electron spectroscopy and secondary-
ion mass spectrometry sputter depth profiling using single
and multi-layer thin films
1 Scope

This International Standard specifies a method for the calibration of the sputtered depth of a material

from a measurement of its sputtering rate under set sputtering conditions using a single- or multi-layer

reference sample with layers of the same material as that requiring depth calibration. The method has a

typical accuracy in the range 5 % to 10 % for layers 20 nm to 200 nm thick when sputter depth profiled

using AES, XPS, and SIMS. The sputtering rate is determined from the layer thickness and the sputtering

time between relevant interfaces in the reference sample and this is used with the sputtering time

to give the thickness of the sample to be measured. The determined ion sputtering rate can be used

for the prediction of ion sputtering rates for a wide range of other materials so that depth scales and

sputtering times in those materials can be estimated through tabulated values of sputtering yields and

atomic densities.
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 14606, Surface chemical analysis — Sputter depth profiling — Optimization using layered systems as

reference materials
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1
upper plateau

region exhibiting intensities higher than 95 % of the maximum intensity of the characteristic signal for

that layer and covering more than half the thickness of that layer
3.2
lower plateau

region exhibiting intensities lower than the minimum intensity plus 5 % of the maximum intensity of

the characteristic signal for that layer and covering more than half the thickness of that layer

4 Requirement of single- and multi-layer reference thin films

4.1 The thickness of each layer in multi-layer thin films and the thickness of single-layer thin films shall

be sufficiently thicker than the sum of the projected range of the sputtering ions and the information

depth of the analytical method so that an upper plateau and a lower plateau shall be obtained for each

layer in sputter depth profiling. The projected range can be simply calculated using SRIM code which is

[7]
available from http://www.srim.org.
© ISO 2015 – All rights reserved 1
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ISO 17109:2015(E)

NOTE Sample rotation during ion sputtering is shown to reduce surface roughness development especially

[11]

of polycrystalline films leading to sharper interfaces and a better estimate of sputtering rates.

4.2 The surface and the interfaces shall be flat and parallel to each other to avoid any distortion of

sputter depth profiles. The surface roughness is often measured using atomic force microscopy and the

thickness variation using transmission electron microscopy. The surface roughness of sample and the

thickness variation of each layer shall be smaller than the sum of the projected range of the sputtering

ions and the information depth of the analytical method.

4.3 The thickness of each layer in multi-layer thin films and the thickness of single-layer thin films shall

be determined by high resolution cross-sectional transmission electron microscopy, grazing incidence

X-ray reflectivity, medium energy ion scattering spectroscopy, or other appropriate methods for which

an accurate uncertainty of measurement can be evaluated.

4.4 The number of A/B layer pairs in the multi-layered reference thin films shall be greater than two

since profiles of the first layer A and the last layer B shall not be used due to the surface and the final

interface transient effects.

4.5 For single-layer thin films, to minimize any likely contamination or surface oxidation problems,

materials like gold on Si or SiO on Si and Ta O on Ta which are stable and remain clean or can easily be

2 2 5
cleaned are recommended.
5 Determination of sputtering rate

5.1 Set the sputtering conditions to be those for which the sputtering rates are required. Changes in

the sputtering species, the impact energy, and beam current will change the sputtering rates. The sputter

depth profiling parameters are optimized according to ISO 14606.

NOTE 1 A typical AES, XPS, and SIMS sputter depth profile is given in Figure A.2 to Figure A.4, respetively.

NOTE 2 The ordinate axis units can be intensity, atomic fraction, an intensity ratio, concentration, or whatever

is the unit most linearly related to the amount of substance present at each depth.

5.2 The sputter depth profiles shall be measured after the instrument has stabilized to minimize

uncertainty due to instrumental fluctuation. Inspect the data, identify, and then ignore, in what follows,

any noise spikes.

5.3 Measure the sputter depth profile of a single- or multi-layer reference thin film and determine

the interface position by the point where the signal intensity of the element reaches 50 % of its value

between the lower plateau where the element is essentially absent and the upper plateau level for the

layer where it is present. The determination of the interface position by this procedure is applied to this

International Standard until the development of an ISO Standard for interface position. The average

intensity in the upper plateau region is the plateau intensity (I ). This shall be calculated by summing

upper

the intensity for each measurement where the intensity is greater than 95 % of the maximum intensity

and dividing by the number of measurements used in the summation.

A similar procedure shall be adopted for the determination of the lower plateau for each constituent of

the profile (I ). The average intensity shall be calculated as follows:
lower

a) subtract the minimum intensity value in this part of the profile from all readings;

b) calculate the value of 5 % of the maximum intensity (following the subtraction in one, above);

c) sum all of the intensities which are less than the 5 % value calculated in two, above;

d) divide the sum by the number of readings to get an average;
2 © ISO 2015 – All rights reserved
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ISO 17109:2015(E)
e) add the minimum intensity to the average calculated in four to arrive at I .
lower
The 50 % signal intensity shall be calculated as follows: I = (I – I )/2.
50 % upper lower

Examples of determining the upper plateau level and the lower plateau level are demonstrated in

Figure A.2 to Figure A.4 for AES, XPS, and SIMS depth profiling, respectively. For single-layer thin

films, the beginning of the sputter time is defined by the time where the intensity for the given element

reaches 50 % of the upper plateau level in the similar manner.

For some sputter depth profiling, often by SIMS, the interface positions may be significantly affected by

changes in the matrix effect in the interface region. If the upper plateau defined with intensities higher

than 95 % of the maximum intensity is less than half of the layer thickness due to large distortions at

interfaces, this standard shall not be used for sputter rate determination.
[2]
NOTE 1 The 50 % of the plateau level is mentioned in ISO/TR 15969.

NOTE 2 A flow chart is given to guide the sputter rate determination of multi-layered thin films and single-

layer thin films as below.

5.4 The sputtering rates of layers of A, z , and B, z , are determined by dividing the thicknesses of

A B
R R R R

layer A, d , and B, d , by the sputtering times of layers of A, t , and B, t , of a reference A/B/A/B….

A B A B
multi-layer thin film. The unit of sputtering rate is nm/s.
R R
zd= /t (1)
( )
AA A
R R
zd= /t (2)
( )
BB B

The sputtering time of layers of A, t , is determined from the time interval from B/A to A/B interfaces

and that of layers of B, t , is determined from the time period from A/B to B/A interfaces. Measure

three sputter depth profiles to determine the uncertainties. If the standard deviation (SD) is

inappropriate, the sputter depth profiling parameters shall be optimized according to ISO 14606 to

improve the uncertainties.

The average sputtering rates of layers of A, z , and B, z , are determined from the average values of

A B

the respective sputtering rates z and z of all layers except the outmost layer A and the last layer B

A B
adjacent to the substrate.

For single-layer thin films, the sputtering rates of layer A, z , is determined with Formula (1). The

sputtering time of layer A, t , is determined from the time interval from the surface layer A to the

A/substrate interface. The average sputtering rate of layer A, z , is determined from the average value

of three consecutive profiling of a single-layer thin film.

NOTE 1 A flow chart is given to guide the sputter rate determination of multi-layered thin films and single-

layer thin films.
NOTE 2 SD of better than 5 % has been found useful and practicable.
© ISO 2015 – All rights reserved 3
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ISO 17109:2015(E)
Set the sputteringconditions
Optimize the sputtering depth
parameters
Multi-layer Single-layer
Single layer or
multilayer ?
Optimize the sputtering depth Optimize the sputtering depth
parameters parameters
Determine the plateau and the bottom Determine the plateau and the bottom

levels for all the layers in a multi-layered level for a single reference thin as

reference thin as 5.3 5.3
Determine the sputtering time from
interface positions for all the layers
Determine the sputtering time from
except the A layer and the last B
interface positions
layer
Determine the sputtering rate from the
Determine the sputtering rate from the sputtering time
sputtering time and the thickness of each
and the thickness of a single reference thin with
layers of a multi-layered reference thin
Formula (1) & (2)
with Formula (1) & (2)
Determine the average sputtering rate
Repeat three times and estimate the SD of
from the sputtering rate of A & B layer of
the sputtering rate
a multi-layered reference thin
Repeat three times and estimate the
Is the SD
standard deviation (SD) of the sputtering
adequate?
rates for the layer A and B
yes yes
Can setting be
changed to yes
improve the SD?
Is the SD
adequate?
stop
yes
Determine the plateau and the bottom
Determine the plateau and the bottom
levels for all the layers in a multi-layered
level for a sample to be determined
thin to be measured
Determine the sputtering time
Determine the sputtering time from the
from interface positions for all the layers except
interface positions for a sample to be
B layer for
determined
a multi-layered thin to be measured
Repeat three times and estimate the
Repeat three times and estimate the SD of
standard deviation (SD) of the sputtering
the sputtering time
time for each layer
Is the SD
Is the SD
adequate?
adequate?
yes yes
Estimate the average sputter time for Estimate the average sputter time of a
each layer of a sample to be determined sample to be determined
Determine the thickness of each layer
Determine the thickness of a sample to
of a sample to be determined using
be determined using Formula (3)
Formula (3) & (4)
end end

5.5 For the multi-layered reference thin film, estimate the standard deviation of sputtering rates for

layer A and layer B using the three average sputtering rates of l
...

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