ISO 17331:2004
(Main)Surface chemical analysis — Chemical methods for the collection of elements from the surface of silicon-wafer working reference materials and their determination by total-reflection X-ray fluorescence (TXRF) spectroscopy
Surface chemical analysis — Chemical methods for the collection of elements from the surface of silicon-wafer working reference materials and their determination by total-reflection X-ray fluorescence (TXRF) spectroscopy
ISO 17331:2004 specifies chemical methods for the collection of iron and/or nickel from the surface of silicon-wafer working reference materials by the vapour-phase decomposition method or the direct acid droplet decomposition method. It applies to iron and/or nickel atomic surface densities from 6 times 10 to the power 9 atoms per square centimetre to 5 times 10 to the power 11 atoms per square centimetre.
Analyse chimique des surfaces — Méthodes chimiques pour collecter les éléments analysés de tranches de silicium comme matériaux de référence pour l'analyse par spectroscopie de fluorescence X en réflexion totale (TXRF)
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INTERNATIONAL ISO
STANDARD 17331
First edition
2004-05-15
Surface chemical analysis — Chemical
methods for the collection of elements
from the surface of silicon-wafer working
reference materials and their
determination by total-reflection X-ray
fluorescence (TXRF) spectroscopy
Analyse chimique des surfaces — Méthodes chimiques pour collecter
les éléments analysés de tranches de silicium comme matériaux de
référence pour l'analyse par spectroscopie de fluorescence X en
réflexion totale (TXRF)
Reference number
ISO 17331:2004(E)
©
ISO 2004
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ISO 17331:2004(E)
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ISO 17331:2004(E)
Contents Page
Foreword. iv
Introduction . v
1 Scope. 1
2 Normative references. 1
3 Terms and definitions. 1
4 Abbreviations. 2
5 Reagents. 2
6 Apparatus. 6
7 Specimen preparation and measurement environments. 6
8 Preparation of calibration specimen. 6
9 Making calibration curve. 8
10 Collection of iron and/or nickel from working reference material . 10
11 Determination of iron and/or nickel of working reference material. 11
12 Precision. 11
13 Test report. 12
Annex A (informative) International inter-laboratory test results. 13
Annex B (informative) International inter-laboratory test results of GF-AAS and ICP-MS . 16
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ISO 17331:2004(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.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.
The main task of technical committees is to prepare International Standards. Draft International Standards
adopted by the technical committees are circulated to the member bodies for voting. Publication as an
International Standard requires approval by at least 75 % of the member bodies casting a vote.
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
rights (see Note to 10.1). ISO shall not be held responsible for identifying any or all such patent rights.
ISO 17331 was prepared by Technical Committee ISO/TC 201, Surface chemical analysis.
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ISO 17331:2004(E)
Introduction
The measurement of metal impurities on the surface of silicon wafers by total-reflection X-ray fluorescence
spectroscopy (TXRF) is commonly accepted by the semiconductor industry.
ISO 14706 specifies a TXRF method for the measurement of metal impurities on a silicon-wafer surface with
10 2 14 2
atomic surface densities from 1 × 10 atoms/cm to 1 × 10 atoms/cm , also a vapour-phase decomposition
8 2 12 2
(VPD) method for atomic surface densities from 5 × 10 atoms/cm to 5 × 10 atoms/cm .
In ultra-large-scale integrated circuit (ULSI) manufacturing, the measurement of very-low-level metal
10 2
impurities on the surface of a silicon wafer, less than 10 atoms/cm , is currently required.
Reference materials with low-level metal impurities are important in TXRF analysis (see ISO 14706), but the
reference materials have a limited shelf life, especially as regards surface contamination. As a result,
preparation methods for working reference materials need to be standardized.
This test method allows the calculation of metal impurities on the surface of reference and test wafers.
Interlaboratory trials in nine laboratories in different countries indicated that this method has good
reproducibility and repeatability.
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INTERNATIONAL STANDARD ISO 17331:2004(E)
Surface chemical analysis — Chemical methods for the
collection of elements from the surface of silicon-wafer working
reference materials and their determination by total-reflection
X-ray fluorescence (TXRF) spectroscopy
1 Scope
This International Standard specifies chemical methods for the collection of iron and/or nickel from the surface
of silicon-wafer working reference materials by the vapour-phase decomposition method or the direct acid
droplet decomposition method.
NOTE The determination of the elements collected may be carried out by graphite-furnace atomic-absorption
spectroscopy or inductively coupled plasma mass spectrometry instead of by total-reflection X-ray fluorescence
spectroscopy.
9 2
This International Standard applies to iron and/or nickel atomic surface densities from 6 × 10 atoms/cm to
11 2
5 × 10 atoms/cm .
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 5725-2:1994, Accuracy (trueness and precision) of measurement methods and results — Part 2: Basic
method for the determination of repeatability and reproducibility of a standard measurement method
ISO 14644-1:1999, Cleanrooms and associated controlled environments — Part 1: Classification of air
cleanliness
ISO 14706:2000, Surface chemical analysis — Determination of surface elemental contamination on silicon
wafers by total-reflection X-ray fluorescence (TXRF) spectroscopy
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1
working reference material
silicon wafer used for the calibration specified in ISO 14706
3.2
calibration specimen
silicon wafer with a known amount of iron and/or nickel in a dried residue, used for calibration purposes
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ISO 17331:2004(E)
3.3
calibration solution
solution used to make a calibration specimen
3.4
internal standard
known amount of vanadium or scandium used to normalize the variation in the fluorescence X-ray intensities
of iron and/or nickel in a residue
3.5
internal-standard solution
solution used to make an internal standard
3.6
scanning
rolling a VPD or DADD microdroplet on a hydrophobic silicon surface in a reproducible pattern to cover the
entire surface of the wafer
4 Abbreviations
For the purposes of this document, the following abbreviations apply:
TXRF total-reflection X-ray fluorescence spectroscopy
VPD vapour-phase decomposition
DADD direct acid droplet decomposition
PE polyethylene
PFA polyfluoroalkoxyethylene
PP polypropylene
PTFE polytetrafluoroethylene
GF-AAS graphite furnace atomic absorption spectroscopy
ICP-MS inductively coupled plasma mass spectroscopy
5 Reagents
WARNING — Hydrofluoric acid is a highly corrosive liquid which attacks glass and has a great affinity
for water. Its vapour is irritant and toxic. Its action on the skin and eyes is strongly corrosive,
producing severe and painful burns which may not be immediately evident and which respond slowly
to treatment.
All specimens shall be handled in a well-ventilated area. Rubber gloves, rubber boots and a gown of a
suitable size to give adequate protection to the individual, as well as full head and face protection,
shall be worn when handling materials.
In an event of contact or suspected contact with hydrofluoric acid, wash the affected area with
copious quantities of water and seek immediate medical attention. Consult the manufacture’s
literature for further information.
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ISO 17331:2004(E)
5.1 Ultra-pure water, containing less than 1 pg/ml of each of the impurities iron, nickel, vanadium and
scandium.
5.2 Ultra-pure hydrofluoric acid, concentration ca. 21 mol/l to ca. 29 mol/l and containing less than
10 pg/ml of each of the impurities iron, nickel, vanadium and scandium.
NOTE The concentration of commercially available ultra-pure hydrofluoric acid is expressed as a percentage.
21 mol/l hydrofluoric acid corresponds to ca. 38 % and 29 mol/l to ca. 50 %.
5.3 Ultra-pure hydrogen peroxide, concentration ca. 10 mol/l to ca. 12 mol/l and containing less than
10 pg/ml of each of the impurities iron, nickel, vanadium and scandium.
NOTE The concentration of commercially available ultra-pure hydrogen peroxide is expressed as a percentage.
10 mol/l hydrogen peroxide corresponds to ca. 30 % and 12 mol/l to ca. 35 %.
5.4 Ultra-pure nitric acid, concentration ca. 11 mol/l to ca. 15 mol/l and containing less than 100 pg/ml of
each of the impurities iron, nickel, vanadium and scandium.
NOTE The concentration of commercially available ultra-pure nitric acid is expressed as a percentage. 11 mol/l nitric
acid corresponds to ca. 55 % and 15 mol/l to ca. 68 %.
5.5 Hydrofluoric acid, concentration ca. 29 mol/l and containing less than 100 pg/ml of each of the
impurities iron, nickel, vanadium and scandium.
NOTE The concentration of commercially available hydrofluoric acid is expressed as a percentage. 29 mol/l
hydrofluoric acid corresponds to ca. 50 %. The hydrofluoric acid specified in 5.5 is available commercially as
“semiconductor” grade.
5.6 Hydrogen peroxide, concentration ca. 10 mol/l and containing less than 100 pg/ml of each of the
impurities iron, nickel, vanadium and scandium.
NOTE The concentration of commercially available hydrogen peroxide is expressed as a percentage. 10 mol/l
hydrogen peroxide corresponds to ca. 30 %. The hydrogen peroxide specified in 5.6 is available commercially as
“semiconductor” grade.
5.7 Standard solutions
5.7.1 Iron standard solution: Use a commercially available 1 000 µg/ml iron standard solution specified for
AAS.
5.7.2 Nickel standard solution: Use a commercially available 1 000 µg/ml nickel standard solution
specified for AAS.
5.7.3 Vanadium standard solution: Use a commercially available 1 000 µg/ml vanadium standard solution
specified for AAS.
5.7.4 Scandium standard solution: Use a commercially available 1 000 µg/ml scandium standard solution
specified for AAS.
5.8 Diluted calibration solutions
5.8.1 Diluted iron calibration solution 1: A 10 µg/ml iron calibration solution in nitric acid.
Prepare diluted iron calibration solution 1 by either method a) or b) below:
a) Transfer 1 000 µl of iron standard solution (5.7.1) to a plastic 100 ml one-mark volumetric flask (6.1) with
a plastic micropipette (6.2), add ca. 90 ml of ultra-pure water (5.1), then add ca.1 ml of ultra-pure nitric
acid (5.4) and finally make up to the mark with ultra-pure water (5.1) and mix.
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ISO 17331:2004(E)
b) Weigh a 100 ml plastic beaker (6.3) to the nearest 0,1 g. Transfer 1 000 µl of iron standard solution
(5.7.1) to the beaker with a plastic micropipette (6.2), add ca. 90 ml of ultra-pure water (5.1), then add ca.
1 ml of ultra-pure nitric acid (5.4) and finally add ultra-pure water (5.1) to make the mass up to 100 g (plus
the mass of the beaker) to the nearest 0,1 g and mix.
5.8.2 Diluted iron calibration solution 2: A 100 ng/ml iron calibration solution in nitric acid.
Prepare diluted iron calibration solution 2 by either method a) or b) below:
a) Transfer 1 000 µl of diluted iron calibration solution 1 (5.8.1 a) to a plastic 100 ml one-mark volumetric
flask (6.1) with a plastic micropipette (6.2), add ca. 90 ml of ultra-pure water (5.1), then add ca. 1 ml of
ultra-pure nitric acid (5.4) and finally make up to the mark with ultra-pure water (5.1) and mix.
b) Weigh a 100 ml plastic beaker (6.3) to the nearest 0,1 g. Transfer 1 000 µl of diluted iron calibration
solution 1 (5.8.1 b) to the beaker with a plastic micropipette (6.2), add ca. 90 ml of ultra-pure water (5.1),
then add ca. 1 ml of ultra-pure nitric acid (5.4) and finally add ultra-pure water (5.1) to make the mass up
to 100 g (plus the mass of the beaker) to the nearest 0,1 g and mix.
5.8.3 Diluted nickel calibration solution 1: A 10 µg/ml nickel calibration solution in nitric acid.
Prepare diluted nickel calibration solution 1 by either method a) or b) below:
a) Transfer 1 000 µl of nickel standard solution (5.7.2) to a 100 ml one-mark volumetric plastic flask (6.1)
with a plastic micropipette (6.2), add ca. 90 ml of ultra-pure water (5.1), then add ca. 1 ml of ultra-pure
nitric acid (5.4) and finally make up to the mark with ultra-pure water (5.1) and mix.
b) Weigh a 100 ml plastic beaker (6.3) to the nearest 0,1 g. Transfer 1 000 µl of the nickel standard solution
(5.7.2) to the beaker with a plastic micropipette (6.2), add ca. 90 ml of ultra-pure water (5.1), then add ca.
1 ml of ultra-pure nitric acid (5.4) and finally add ultra-pure water (5.1) to make the mass up to 100 g (plus
the mass of the beaker) to the nearest 0,1 g and mix.
5.8.4 Diluted nickel calibration solution 2: A 100 ng/ml nickel calibration solution in nitric acid.
Prepare diluted nickel calibration solution 2 by either method a) or b) below:
a) Transfer 1 000 µl of diluted nickel calibration solution 1 (5.8.3 a) to a plastic 100 ml one-mark volumetric
flask (6.1) with a plastic micropipette (6.2), add ca. 90 ml of ultra-pure water (5.1), then add ca. 1 ml of
ultra-pure nitric acid (5.4) and finally make up to the mark with ultra-pure water (5.1) and mix.
b) Weigh a 100 ml plastic beaker (6.3) to the nearest 0,1 g. Transfer 1 000 µl of diluted nickel calibration
solution 1 (5.8.3 b) to the beaker with a plastic micropipette (6.2), add ca. 90 ml of ultra-pure water (5.1),
then add ca. 1 ml of ultra-pure nitric acid (5.4) and finally add ultra-pure water (5.1) to make the mass up
to 100 g (plus the mass of the beaker) to the nearest 0,1 g and mix.
5.8.5 Diluted iron and nickel mixture calibration solution 1: A 10 µg/ml iron and 10 µg/ml nickel mixture
calibration solution in nitric acid.
Prepare diluted iron and nickel mixture calibration solution 1 by either method a) or b) below:
a) Transfer 1 000 µl of iron standard solution (5.7.1) and 1 000 µl of nickel standard solution (5.7.2) to a
plastic 100 ml one-mark volumetric flask (6.1) using a different plastic micropipette (6.2) for each, add ca.
90 ml of ultra-pure water (5.1), then add ca. 1 ml of ultra-pure nitric acid (5.4) and finally make up to the
mark with ultra-pure water (5.1) and mix.
b) Weigh a 100 ml plastic beaker (6.3) to the nearest 0,1 g. Transfer 1 000 µl of iron standard solution
(5.7.1) and 1 000 µl of nickel standard solution (5.7.2) to the beaker using a different plastic micropipette
(6.2) for each, add ca. 90 ml of ultra-pure water (5.1), then add ca. 1 ml of ultra-pure nitric acid (5.4) and
finally add ultra-pure water (5.1) to make the mass up to 100 g (plus the mass of the beaker) to the
nearest 0,1 g and mix.
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ISO 17331:2004(E)
5.8.6 Diluted iron and nickel mixture calibration solution 2: A 100 ng/ml iron and 100 ng/ml nickel
mixture calibration solution in nitric acid.
Prepare diluted iron and nickel mixture calibration solution 2 by either method a) or b) below:
a) Transfer 1 000 µl of diluted iron and nickel mixture calibration solution 1 (5.8.5 a) to a plastic 100 ml one-
mark volumetric flask (6.1) with a plastic micropipette (6.2), add ca. 90 ml of ultra-pure water (5.1), then
add ca. 1 ml of ultra-pure nitric acid (5.4) and finally make up to the mark with ultra-pure water (5.1) and
mix.
b) Weigh a 100 ml plastic beaker (6.3) to the nearest 0,1 g. Transfer 1 000 µl of iron and nickel mixture
calibration solution 1 (5.8.5 b) to the beaker with a plastic micropipette (6.2), add ca. 90 ml of ultra-pure
water (5.1), then add ca. 1 ml of ultra-pure nitric acid (5.4) and finally add ultra-pure water (5.1) to make
the mass up to 100 g (plus the mass of the beaker) to the nearest 0,1 g and mix.
5.9 Internal standard solution: A 1 µg/ml vanadium or scandium solution in nitric acid.
Prepare the internal standard solution by either method a) or b) below:
a) Transfer 100 µl of vanadium standard solution (5.7.3) or 100 µl of scandium standard solution (5.7.4) to a
plastic 100 ml one-mark volumetric flask (6.1) with a plastic micropipette (6.2), add ca. 90 ml of ultra-pure
water (5.1), then add ca. 1 ml of ultra-pure nitric acid (5.4) and finally make up to the mark with ultra-pure
water (5.1) and mix.
b) Weigh a 100 ml plastic beaker (6.3) to the nearest 0,1 g. Transfer 100 µl of vanadium standard solution
(5.7.3) or 100 µl of scandium standard solution (5.7.4) to the beaker with a plastic micropipette (6.2), add
ca. 90 ml of ultra-pure water (5.1), then add ca. 1 ml of ultra-pure nitric acid (5.4) and finally add ultra-
pure water (5.1) to make the mass up to 100 g (plus the mass of the beaker) to the nearest 0,1 g and mix.
5.10 Blank solution: A mixture containing ca. 1 mol/l of hydrofluoric acid and ca. 0,7 mol/l of hydrogen
peroxide.
Prepare the blank solution by either method a) or b) below:
a) Transfer ca. 50 ml of ultra-pure hydrofluoric acid (5.2) and ca. 60 ml of ultra-pure hydrogen peroxide (5.3)
to a plastic 1 000 ml one-mark volumetric flask (6.1), make up to the mark with ultra-pure water (5.1) and
mix.
b) Weigh a 1 000 ml plastic beaker (6.3) to the nearest 1 g. Transfer ca. 56 g of ultra-pure hydrofluoric acid
(5.2) and ca. 65 g of ultra-pure hydrogen peroxide (5.3) to the beaker, add ultra-pure water (5.1) to make
the mass up to 1 000 g (plus the mass of the beaker) to the nearest 1 g and mix.
5.11 Scanning solution: A mixture containing 1 mol/l of hydrofluoric acid and 0,7 mol/l of hydrogen peroxide
plus 25 ng/ml of vanadium or scandium internal standard.
Prepare the scanning solution by either method a) or b) below:
a) Transfer ca. 5,0 ml of ultra-pure hydrofluoric acid (5.2) and ca. 6,0 ml of ultra-pure hydrogen peroxide
(5.3) to a plastic 100 ml one-mark volumetric flask (6.1), then add 2 500 µl of vanadium or scandium
internal standard solution (5.9 a) with a plastic micropipette (6.2), make up to the mark with ultra-pure
water (5.1) and mix.
b) Weigh a 100 ml plastic beaker (6.3) to the nearest 0,1 g. Transfer ca. 5,6 g of ultra-pure hydrofluoric acid
(5.2) and ca. 6,5 g of ultra-pure hydrogen peroxide (5.3) to the beaker, then add 2 500 µl of vanadium or
scandium internal standard solution (5.9 b) with a plastic micropipette (6.2), add ultra-pure water (5.1) to
make the mass up to 100 g (plus the mass of the beaker) to the nearest 0,1 g and mix.
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ISO 17331:2004(E)
5.12 Cleaning solution: A mixture containing ca. 5 mol/l of hydrofluoric acid and ca. 2 mol/l of hydrogen
peroxide.
Prepare the cleaning solution using hydrofluoric acid (5.5) and hydrogen peroxide (5.6). Mix the hydrofluoric
acid and hydrogen peroxide with ultra-pure water (5.1) in the approximate volume ratio of 1:1:3.
6 Apparatus
For the preparation of reagents and specimens use ordinary laboratory glassware or plasticware unless
otherwise stated.
In order to check the accuracy of micropipettes used in the volumetric method, these shall be periodically
calibrated by taking an exact volume of water with the micropipette and weighing it on a high-precision
balance.
CAUTION — Apparatus that may come into contact with hydrofluoric acid and/or hydrofluoric acid
solution shall not be made of glass or other silicate materials. Hydrofluoric acid attacks such
materials.
6.1 Plastic one-mark volumetric flasks, 100 ml ± 1 ml and 1 000 ml ± 1 ml, made of PE, PFA or PP.
6.2 Plastic micropipettes, 100 µl ± 1 µl, 1 000 µl ± 10 µl, from 10 µl ± 0,1 µl to 100 µl ± 1 µl and from
100 µl ± 1 µl to 1 000 µl ± 10 µl, made of PE, PFA or PP.
6.3 Plastic beakers, 100 ml and 1 000 ml, made of PE, PFA, PP or PTFE.
6.4 Wafer-stand, made of PFA or PTFE.
6.5 Drying apparatus: Use either an infrared lamp with a power controller or a vacuum vessel fitted with
gas flow equipment and/or an infrared lamp.
6.6 Vertical laminar flow cabinet, meeting the requirements for ISO class 2 (see ISO 14644-1) or better.
For reasons of cleanliness and operator safety, clean air shall be passed over the specimen-handling area
and exhausted outside the cabinet.
6.7 VPD box, made of PTFE, PFA or similar material.
7 Specimen preparation and specimen measurement environments
7.1 Specimens shall be handled in a clean environment (ISO class 4 or better) (see ISO 14644-1).
7.2 The instruments shall be set up in a clean environment (ISO class 5 or better) (see ISO 14644-1).
8 Preparation of calibration specimens
8.1 Prepare five silicon wafers of which the crystallographic orientation is the same as that of the silicon
wafers specified in ISO 14706.
Just before preparing the actual calibration specimens, clean the silicon wafers with cleaning solution (5.12) in
order to make the surface of the wafers clean and hydrophobic.
8.2 Prepare calibration solutions containing 0 ng/ml, 0,1 ng/ml, 1 ng/ml, 10 ng/ml and 25 ng/ml of iron,
nickel, or iron and nickel, plus 25 ng/ml of vanadium or scandium internal standard solution (5.9) by either the
volumetric procedure in 8.2.1 or the gravimetric procedure in 8.2.2.
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ISO 17331:2004(E)
8.2.1 Volumetric method
Prepare five plastic 100 ml one-mark volumetric flasks (6.1) for the following solutions:
a) For the preparation of the 0 ng/ml calibration solution, transfer 2 500 µl of vanadium or scandium internal
standard solution (5.9 a) with a plastic micropipette (6.2) to a plastic 100 ml one-mark volumetric flask
(6.1), make up to the mark with blank solution (5.10 a) and mix.
b) For the preparation of the 0,1 ng/ml calibration solution, transfer 100 µl of diluted iron calibration
solution 2 (5.8.2 a), diluted nickel calibration solution 2 (5.8.4 a) or diluted iron and nickel mixture
calibration solution 2 (5.8.6 a) with a plastic micropipette (6.2) to a plastic 100 ml one-mark volumetric
flask (6.1) and add 2 500 µl of vanadium or scandium internal standard solution (5.9 a), also with a plastic
micropipette (6.2), make up to the mark with blank solution (5.10 a) and mix.
c) For the preparation of the 1 ng/ml calibration solution, transfer 1 000 µl of diluted iron calibration
solution 2 (5.8.2 a), diluted nickel calibration solution 2 (5.8.4 a) or diluted iron and nickel mixture
calibration solution 2 (5.8.6 a) with a plastic micropipette (6.2) to a plastic 100 ml one-mark volumetric
flask (6.1) and add 2 500 µl of vanadium or scandium internal standard solution (5.9 a), also with a plastic
micropipette (6.2), make up to the mark with blank solution (5.10 a) and mix.
d) For the preparation of the 10 ng/ml calibration solution, transfer 100 µl of diluted iron calibration solution 1
(5.8.1 a), diluted nickel calibration solution 1 (5.8.3 a) or diluted iron and nickel mixture calibration
solution 1 (5.8.5 a) with a plastic micropipette (6.2) to a plastic 100 ml one-mark volumetric flask (6.1) and
add 2 500 µl of vanadium or scandium internal standard solution (5.9 a), also with a plastic micropipette
(6.2), make up to the mark with blank solution (5.10 a) and mix.
e) For the preparation of the 25 ng/ml calibration solution, transfer 250 µl of diluted iron calibration solution 1
(5.8.1 a), diluted nickel calibration solution 1 (5.8.3 a) or diluted iron and nickel mixture calibration
solution 1 (5.8.5 a) with a plastic micropipette (6.2) to a 100 ml plastic one-mark volumetric flask (6.1) and
add 2 500 µl of vanadium or scandium internal standard solution (5.9 a), also with a plastic micropipette
(6.2), make up to the mark with blank solution (5.10 a) and mix.
NOTE Vanadium or scandium internal standard can either be added in the calibration solution, as above, or be
added directly to the droplet placed on the wafer, before the droplet is dried.
8.2.2 Weighing method
Prepare five 100 ml plastic beakers (6.3) for the following solutions:
a) For the preparation of the 0 ng/ml calibration solution, weigh a 100 ml plastic beaker (6.3) to the nearest
0,1 g. Transfer 2 500 µl of vanadium or scandium internal standard solution (5.9 b) with a plastic
micropipette (6.2) to the beaker, add blank solution (5.10 b) to make the mass up to 100 g (plus the mass
of the beaker) to the nearest 0,1 g and mix.
b) For the preparation of the 0,1 ng/ml calibration solution, weigh a 100 ml plastic beaker (6.3) to the nearest
0,1 g. Transfer 100 µl of diluted iron calibration solution 2 (5.8.2 b), diluted nickel calibration solution 2
(5.8.4 b) or diluted iron and nickel mixture calibration solution 2 (5.8.6 b) with a plastic micropipette (6.2)
to the beaker, add 2 500 µl of vanadium or scandium internal standard solution (5.9 b), also with a plastic
micropipette (6.2), and finally add blank solution (5.10 b) to make the mass up to 100 g (plus the mass of
the beaker) to the nearest 0,1 g and mix.
c) For the preparation of the 1 ng/ml calibration solution, weigh a 100 ml plastic beaker (6.3) to the nearest
0,1 g. Transfer 1 000 µl of diluted iron calibration solution 2 (5.8.2 b), diluted nickel calibration solution 2
(5.8.4 b) or diluted iron and nickel mixture calibration solution 2 (5.8.6 b) with a plastic micropipette (6.2)
to the beaker, add 2 500 µl of vanadium or scandium internal standard solution (5.9 b), also with a plastic
micropipette (6.2), and finally add blank solution (5.10 b) to make the mass up to 100 g (plus the mass of
the beaker) to the nearest 0,1 g and mix.
d) For the preparation of the 10 ng/ml calibration solution, weigh a 100 ml plastic beaker (6.3) to the nearest
0,1 g. Transfer 100 µl of diluted iron calibration solution 1 (5.8.1 b), diluted nickel calibration solution 1
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