ASTM F1724-01

Standard Test Method for Measuring Surface Metal Contamination of Polycrystalline Silicon by Acid Extraction-Atomic Absorption Spectroscopy (Withdrawn 2003)

SCOPE
This standard was transferred to SEMI (www.semi.org) May 2003
1.1 This test method covers the quantitative determination of surface trace metal contamination on the surface of polycrystalline silicon using an acid to extract the metals from the surface. The metals content of the acid is then analyzed by graphite furnace atomic-absorption spectroscopy.
1.2 This test method can be used for various rod, chunk, granule and chip sizes, for polycrystalline or single crystal silicon, to determine surface metal contaminants. Since the area of irregularly-shaped chunks, chips, or granules is difficult to measure accurately, values are based on sample weight. Using a sample weight of 300 g allows detection limits at the 0.1 ppbw (parts per billion weight) level.
1.3 The strength, composition, temperature, and exposure time of the acid determine the depth of surface etching and the efficiency of the extraction of the contaminants from the surface. Less than 1 % of the sample weight is removed in this test method.
1.4 This test method is useful for determining the alkali elements, alkali earth, and first series transition elements, such as sodium, potassium, calcium, iron, chromium, nickel, copper, zinc, as well as other elements such as aluminum. The recovery of these elements from the silicon surface is measured as greater than 90 %, using control standards intentionally added to the polysilicon surface.
1.5 This test method suggests a particular sample size, acid composition, etch cycle, testing environment, and instrument protocol. Variations in these parameters may be used, but may effect the recovery efficiency or retention of metals during processing. In practice, this test method is used for sample weights of 25 to 5000 g. For referee purposes, this test method specifies a sample weight of 300 g. This test method includes guidelines to alert the analyst to the interferences and resultant variations in this test method, and includes standard methods for quantifying and reporting these variations.
1.6 This test method specifies the use of graphite furnace atomic-absorption spectroscopy to analyze trace metals content of the acid extract. Other instruments of equivalent sensitivity, such as inductively-coupled plasma/mass spectrometry, may be used.
1.7 The detection limit and method variation depend on the efficiency of the acid extraction procedure, sample size, the method interferences, the absorption spectrum of each element, and the instrumental sensitivity, background, and blank value.
1.8 This test method uses hot acid to etch away the surface of the silicon. The etchant is potentially harmful and must be handled in an acid exhaust fume hood, with utmost care at all times. Hydrofluoric acid solutions are particularly hazardous and should not be used by anyone who is not familiar with the specific preventive measures and first aid treatments given in the appropriate Material Safety Data Sheet.
1.9 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use. Specific precautionary statements are given in Section 9.

General Information

• Status: Withdrawn
• Publication Date: 09-Jun-2001
• Withdrawal Date: 09-May-2003
• ICS: 29.045 - Semiconducting materials
• Technical Committee: F01 - Electronics

Relations

• Replaces: ASTM F1724-96 - Standard Test Method for Measuring Surface Metal Contamination of Polycrystalline Silicon by Acid Extraction-Atomic Absorption Spectroscopy
• Effective Date: 10-Jun-2001

Standards Content (Sample)

NOTICE: This standard has either been superceded and replaced by a new version or discontinued.
Contact ASTM International (www.astm.org) for the latest information.
Designation: F 1724 – 01
Standard Test Method for
Measuring Surface Metal Contamination of Polycrystalline
Silicon by Acid Extraction-Atomic Absorption
1
Spectroscopy
This standard is issued under the fixed designation F 1724; 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 (e) indicates an editorial change since the last revision or reapproval.
1. Scope of the acid extract. Other instruments of equivalent sensitivity,
such as inductively-coupled plasma/mass spectrometry, may be
1.1 This test method covers the quantitative determination
used.
of surface trace metal contamination on the surface of poly-
1.7 The detection limit and method variation depend on the
crystalline silicon using an acid to extract the metals from the
efficiency of the acid extraction procedure, sample size, the
surface. The metals content of the acid is then analyzed by
method interferences, the absorption spectrum of each element,
graphite furnace atomic-absorption spectroscopy.
and the instrumental sensitivity, background, and blank value.
1.2 This test method can be used for various rod, chunk,
1.8 This test method uses hot acid to etch away the surface
granule and chip sizes, for polycrystalline or single crystal
of the silicon. The etchant is potentially harmful and must be
silicon, to determine surface metal contaminants. Since the
handled in an acid exhaust fume hood, with utmost care at all
area of irregularly-shaped chunks, chips, or granules is difficult
times. Hydrofluoric acid solutions are particularly hazardous
to measure accurately, values are based on sample weight.
and should not be used by anyone who is not familiar with the
Using a sample weight of 300 g allows detection limits at the
specific preventive measures and first aid treatments given in
0.1 ppbw (parts per billion weight) level.
the appropriate Material Safety Data Sheet.
1.3 The strength, composition, temperature, and exposure
1.9 This standard does not purport to address all of the
time of the acid determine the depth of surface etching and the
safety concerns, if any, associated with its use. It is the
efficiency of the extraction of the contaminants from the
responsibility of the user of this standard to establish appro-
surface. Less than 1 % of the sample weight is removed in this
priate safety and health practices and determine the applica-
test method.
bility of regulatory limitations prior to use. Specific precau-
1.4 This test method is useful for determining the alkali
tionary statements are given in Section 9.
elements, alkali earth, and first series transition elements, such
as sodium, potassium, calcium, iron, chromium, nickel, copper,
2. Referenced Documents
zinc, as well as other elements such as aluminum. The recovery
2.1 ASTM Standards:
of these elements from the silicon surface is measured as
2
D 5127 Guide for Electronic Grade Water
greater than 90 %, using control standards intentionally added
E 122 Practice for Choice of Sample Size to Estimate a
to the polysilicon surface.
3
Measure of Quality of a Lot or Process
1.5 This test method suggests a particular sample size, acid
2.2 SEMI Standards:
composition, etch cycle, testing environment, and instrument
SEMI C28 Specifications and Guidelines for Hydrofluoric
protocol. Variations in these parameters may be used, but may
4
Acid
effect the recovery efficiency or retention of metals during
SEMI C30 Specifications and Guidelines for Hydrogen
processing. In practice, this test method is used for sample
4
Peroxide
weights of 25 to 5000 g. For referee purposes, this test method
4
SEMI C35 Specifications and Guideline for Nitric Acid
specifies a sample weight of 300 g. This test method includes
2.3 Federal Standard:
guidelines to alert the analyst to the interferences and resultant
209E Airborne Particulate Cleanliness Classes in Clean-
variations in this test method, and includes standard methods
5
rooms and Clean Zones
for quantifying and reporting these variations.
2.4 ISO Standard:
1.6 This test method specifies the use of graphite furnace
ISO 14644–1 Cleanrooms and associated controlled
atomic-absorption spectroscopy to analyze trace metals content
2
Annual Book of ASTM Standards, Vol 11.01.
1 3
This test method is under the jurisdiction of ASTM Committee F01 on Annual Book of ASTM Standards, Vol 14.02.
4
Electronics and is the direct responsibility of Subcommittee F01.06 on Silicon Available from Semiconductor Equipment and Materials International, 3081
Materials and Process Control. Zanker Road, San Jose, CA 95134 (www.semi.org).
5
Current edition approved June 10, 2001. Published August 2001. Originally Available from Superintendent of Documents, U.S.
...