ASTM F2405-04

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Designation:F2405–04
Standard Test Method for
Trace Metallic Impurities in High Purity Copper by High-
Mass-Resolution Glow Discharge Mass Spectrometer
This standard is issued under the fixed designation F2405; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope E876 Practice for Use of Statistics in the Evaluation of
Spectrometric Data
1.1 This test method covers the concentrations of trace
F1593 Test Method for Trace Metallic Impurities in Elec-
metallic impurities in high purity (99.95 wt. % pure, or purer,
tronic Grade Aluminum by High Mass-Resolution Glow-
with respect to metallic trace impurities) electronic grade
Discharge Mass Spectrometer
copper.
1.2 This test method pertains to analysis by magnetic-sector
3. Terminology
glow discharge mass spectrometer (GDMS).
3.1 Terminology in this test method is consistent with
1.3 This test method does not include all the information
Terminology E135. Required terminology specific to this test
needed to complete GDMS analyses. Sophisticated computer-
method, not covered in Terminology E135, is indicated in 3.2.
controlled laboratory equipment, skillfully used by an experi-
3.2 Definitions:
enced operator, is required to achieve the required sensitivity.
3.2.1 campaign—atestproceduretodeterminetheaccuracy
Thistestmethoddoescovertheparticularfactors(forexample,
of the instrument, which was normally performed at the
specimen preparation, setting of relative sensitivity factors,
beginning of the day or after the instrument modification, or
determination of detection limits, and the like) known by the
both.
responsible technical committee to effect the reliability of high
3.2.2 reference sample—material accepted as suitable for
purity copper analyses.
use as a calibration/sensitivity reference standard by all parties
1.4 This standard does not purport to address all of the
concerned with the analyses.
safety concerns, if any, associated with its use. It is the
3.2.3 specimen—a suitably sized piece cut from a reference
responsibility of the user of this standard to establish appro-
or test sample, prepared for installation in the GDMS ion
priate safety and health practices and determine the applica-
source, and analyzed.
bility of regulatory limitations prior to use.
3.2.4 test sample—material (copper) to be analyzed for
2. Referenced Documents trace metallic impurities by this GDMS method.
2 3.2.4.1 Discussion—Generally the test sample is extracted
2.1 ASTM Standards:
from a larger batch (lot, casting) of product and is intended to
E135 Terminology Relating to Analytical Chemistry for
be representative of the batch.
Metals, Ores, and Related Materials
E173 Practice for Conducting Interlaboratory Studies of
4. Summary of Test Method
Methods for Chemical Analysis of Metals
4.1 A specimen is mounted in a plasma discharge cell.
E180 Practice for Determining the Precision of ASTM
Atoms subsequently sputtered from the specimen surface are
Methods for Analysis and Testing of Industrial and Spe-
ionized, and then focused as an ion beam through a double-
cialty Chemicals
focusing magnetic-sector mass separation apparatus. The mass
E691 Practice for Conducting an Interlaboratory Study to
spectrum (the ion current) is collected as magnetic field or
Determine the Precision of a Test Method
acceleration voltage, or both, and is scanned.
4.2 The ion current of an isotope at mass M is the total
i
measured current, less contributions from all other interfering
This test method is under the jurisdiction of ASTM Committee F01 on
sources. Portions of the measured current may originate from
Electronics and is the direct responsibility of Subcommittee F01.17 on Sputter
the ion detector alone (detector noise). Portions may be due to
Metallization.
Current edition approved May 1, 2004. Published June 2004. DOI: 10.1520/ incompletelymassresolvedionsofanisotopeormoleculewith
F2405-04.
mass close to, but not identical with M. In all such instances
i
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. Withdrawn. The last approved version of this historical standard is referenced
Withdrawn. on www.astm.org.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
F2405–04
the interfering contributions must be estimated and subtracted 6. Apparatus
from the measured signal.
6.1 Glow Discharge Mass Spectrometer, with mass resolu-
4.2.1 If the source of interfering contributions to the mea-
tion greater than 3500, and associated equipment and supplies.
sured ion current at M cannot be determined unambiguously,
6.2 Machining Apparatus, capable of preparing specimens
i
the measured current less the interfering contributions from
andreferencesamplesinthedesiredgeometryandwithsmooth
identified sources constitutes an upper bound of the detection
surfaces.
limit for the current due to the isotope.
7. Reagents and Materials
4.3 The composition of the test specimen is calculated from
7.1 Reagents—Reagent and high purity grade reagents as
the mass spectrum by applying a relative sensitivity factor
required (MeOH, HNO , and HF).
(RSF(X/M)) for each contaminant element, X, compared to the
7.2 Demineralized Water.
matrixelement, M.RSF’saredeterminedinaseparateanalysis
7.3 Tantalum Reference Sample.
of a reference material performed under the same analytical
7.4 Copper Reference Sample:
conditions, source configuration, and operating protocol as for
7.4.1 To the extent available, copper reference materials
the test specimen.
shall be used to produce the GDMS relative sensitivity factors
4.4 The relative concentrations of elements X and Y are
for the various elements being determined (see Table 1).
calculated from the relative isotopic ion currentsI(X) and I
i
7.4.1.1 As necessary, non-copper reference materials may
(Y) in the mass spectrum, adjusted for the appropriate isotopic
j
be used to produce the GDMS relative sensitivity factors for
abundance factors (A (X),A(Y) and RSF’s.I(X) andI(Y)
i j i j
the various elements being determined.
refer to the measured ion current from isotopes X and Y,
i j
7.4.2 Reference materials should be homogeneous (see
respectively, of atomic species X and Y as follows:
11.1) and free of cracks or porosity.
~X! RSF~X/M! A~Y ! I~X !
j i
7.4.3 At least two reference materials are required to estab-
5 3 3
~Y! RSF~Y/M! A~X ! I~Y !
i j
lish the relative sensitivity factors, including a 99.9999 % pure
where (X)/(Y) is the concentration ratio of atomic species X copper metal to establish the background contribution in
to species Y. If species Y is taken to be the copper matrix (RSF analyses.
(M/M) = 1.0), (X) is (with only very small error for pure metal 7.4.4 The concentration of each analyte for relative sensi-
matrices) the absolute impurity concentration of X. tivity factor determination should be at a factor of 100 greater
than the detection limit determined using a 99.9999 % pure
copper specimen, but less than 100 ppmw.
5. Significance and Use
7.4.5 To meet expected analysis precision, it is necessary
5.1 This test method is intended for application in the
that specimens of reference and test material present the same
semiconductor industry for evaluating the purity of materials
size and configuration (shape and exposed length) in the glow
(for example, sputtering targets, evaporation sources) used in
discharge ion source, with a tolerance of 0.2 mm in diameter
thin film metallization processes. This test method may be
and 0.5 mm in the distance of sample to cell ion exit slit.
useful in additional applications, not envisioned by the respon-
sible technical committee, as agreed upon between the parties
8. Preparation of Reference Standards and Test
concerned.
Specimens
5.2 This test method is intended for use by GDMS analysts
8.1 The surface of the parent material must not be included
invariouslaboratoriesforunifyingtheprotocolandparameters
in the specimen.
for determining trace impurities in copper. The objective is to
8.2 The machined surface of the specimen must be cleaned
improve laboratory-to-laboratory agreement of analysis data.
by etching immediately prior to mounting the specimen and
This test method is also directed to the users of GDMS
inserting it into the glow discharge ion source.
analyses as an aid to understanding the determination method,
8.2.1 In order to obtain a representative bulk composition in
and the significance and reliability of reported GDMS data.
a reasonable analytical time, surface cleaning must remove all
5.3 For most metallic species, the detection limit for routine
contaminants without altering the composition of the specimen
analysis is on the order of 0.01 wt. ppm. With special
surface.
precautions, detection limits to sub-ppb levels are possible.
8.2.2 To minimize the possibility of contamination, clean
5.4 This test method may be used as a referee method for eachspecimenseparately,immediatelypriortomountinginthe
producers and users of electronic-grade copper materials. glow discharge ion source.
A
TABLE 1 Suite of Impurity Elements to Be Analyzed
NOTE—Establish RSFs for the following suite of elements:
Aluminum Antimony Arsenic Beryllium Bismuth Boron Calcium Carbon
Chromium Cobalt Germanium Gold Iron Lead Lithium Magnesium
Manganese Molybdenum Nickel Niobium Nitrogen Oxygen Phosphorous Potassium
Selenium Silicon Silver Sodium Sulfur Tellurium Thorium Tin
Titanium Uranium Vanadium Zinc Zirconium
A
Additional species may be determined and reported, as agreed upon between all parties concerned with the analyses.
F2405–04
A
TABLE 2 Isotope Selection
8.2.3 Prepare etching solutions in a clean container in-
soluble in the contained solution.
NOTE—Use the following isotopes for establishing RSF values and for
8.2.3.1 Etching—Perform etching by immersing the speci-
performing analyses on test specimens.
men in a suitable acid mixture solution (4:1:1 H O:HF:HNO
2 3 Element Isotope
and 1:1 H O:HNO were found applicable). Etch the specimen
2 3
Aluminum Al 27
until smooth, clean metal is exposed over the entire surface.
Antimony Sb 121
Arsenic As 75
8.3 Immediately after cleaning, wash the specimen with
Beryllium Be 9
several rinses of high purity methanol, or other high purity
Bismuth Bi 209
reagent able to remove water from the specimen surface, and
Boron B 11
Calcium Ca 44
dry the specimen in the laboratory environment.
Carbon C 12
8.4 Immediately mount and insert the specimen into the
Chromium Cr 52
glow discharge ion source, minimizing exposure of the Cobalt Co 59
Germanium Ge 70
cleaned, rinsed and dried specimen surface to the laboratory
Gold Au 197
environment.
Iron Fe 56
Lead Pb 208
8.4.1 As necessary, use a noncontacting gage when mount-
Lithium Li 7
ing specimens in the analysis cell specimen holder to ensure
Magnesium Mg 24
the proper sample configuration in the glow discharge cell (see
Manganese Mn 55
Molybdenum Mo 98
7.4.5).
Nickel Ni 58
8.5 Sputter etch the specimen surface in the glow discharge
Niobium Nb 93
plasma for a period of time before data acquisition to ensure
Nitrogen N 14
Oxygen O 16
the cleanness of the surface (see 12.3). Pre-analysis sputtering
Phosphorous P 31
conditions are limited by the need to maintain sample integrity.
Potassium K 39
Pre-analysis sputtering at twice the power used for analysis
Selenium Se 82
Silicon Si 28
should be adequate for sputter etch cleaning.
Silver Ag 109
Sodium Na 23
9. Preparation of the GDMS Apparatus
Sulfur S 32
Tellurium Te 125
9.1 See Test Method F1593, Section 9 on Preparation of the
Thorium Th 232
Tin Sn 124
GDMS Apparatus.
Titanium Ti 48
Uranium U 238
10. Instrument Quality Control
Vanadium V 51
Zinc Zn 68
10.1 See Test Method F1593, Section 10 on Instrument
Zirconium Zr 90
Quality Control, using a copper reference standard in place of
A
This selection of isotopes minimizes significant interference. Additional spe-
an aluminum standard.
cies may be determined and reported, as agreed upon between all parties
concerned with the analyses.
11. Standardization
TABLE 3 Required Relative Standard Deviation (RSD) for RSF
11.1 The GDMS instrument should be standardized using
Determinations, Pre-Sputtering Period, and Plasma Stability
international recognized reference materials, preferably cop-
Tests (between the last two measurements)
per, to the extent such reference samples are available.
Analyte Content Concentration
11.1.1 RSF values should, in the best case, be determined Range Difference, %
from the ion beam ratio measurements of four randomly
Major (>100 ppm) 5
Minor (100 ppm > 3 >1 ppm) 10
selected specimens from each standard required, with four
Trace (1 ppm > 3 >100 ppb) 20
independent measurements of each pin.
11.1.2 RSF values must be determined for the suite of
impurity elements for which specimens are to be analyzed (see
and detection limits; and (2) mass ranges about the analyte
Table 1) using selected isotopes for measurement and RSF
mass peak over which measurements are acquired to clarify
calculation (see Table 2).
mass interference.
12.2 Insert the prepared specimen into the GDMS ion
12. Analysis Procedure
source, allow the specimen to cool to source temperature, and
12.1 Establish a suitable data acquisition protocol (DAP)
initiate the glow discharge at pre-analysis sputtering condi-
appropriate for the GDMS instrument used for the analysis.
tions.
12.1.1 The protocol must include, but is not limited to, the 12.3 After at least 5 min of pre-analysis sputtering, adjust
measurement of elements tabulated in Table 1 and isotopes
the glow discharge ion source sputtering conditions to the
tabulated in Table 2. Annex A1 lists significant spectral conditions required for analysis, ensuring that the gas pressure
interference in this testing.
required to do so is within normal range.
12.1.2 Instrumental parameters selected for isotope mea- 12.4 Analyze the specimen using the DAP protocol, and
surements must be appropriate for the analysis requirements: accept as final the concentration values determined only as
(1) ion current integration times to achieve desired precision detection limits.
F2405–04
TABLE 4 Summary of Copper Round Robin Test Results Providing Precision and Bias on Interlaboratory GDMS Analysis
A
of High Purity Copper
All entries
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