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SEMI C44-0301 © SEMI 1978, 2001 SULFURIC ACID 2 minute s. Cool and tra nsfer to a tightly -capped glass bottle for storage. 8.4 Nitrate — Prepare the followin g so lutions: Sam p le Soluti on A: Cautiously add 27 m L (50…

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SULFURIC ACID SEMI C44-0301 © SEMI 1978, 20011
SEMI C44-0301
SPECIFICATIONS AND GUIDELINES FOR SULFURIC ACID
These specifications and guidelines were technically approved by the Global Process Chemicals Committee
and are the direct responsibility of the North American Process Chemicals Committee. Current edition
approved by the North American Regional Standards Committee on October 17, 1999. Initially available at
www.semi.org February 2001; to be published March 2001. This document replaces SEMI C1.16, C7.8,
C8.8, and C11.5 in their entirety. Originally published in 1978, 1990, 1992, and 1994 respectively;
previously published October 2000.
1 Purpose
1.1 The purpose of this document is to standardize
requirements for sulfuric acid used in the
semiconductor industry and testing procedures to
support those standards. Test methods have been shown
to give statistically valid results. This document also
provides guidelines for grades of sulfuric acid for which
a need has been identified. In the case of the guidelines,
the test methods may not have been statistically
validated yet.
2 Scope
2.1 The scope of this document is all grades of sulfuric
acid used in the semiconductor industry.
2.2 The VLSI grade purity level is typically required
by semiconductor devices with geometries of 0.8–1.2
microns.
2.3 This standard does not purport to address safety
issues, if any, associated with its use. It is the
responsibility of the users of this standard to establish
appropriate safety and health practices and determine
the applicability of regulatory limitations prior to use.
3 Limitations
3.1 None.
4 Referenced Standards
4.1 SEMI Standards
SEMI C1 — Specifications for Reagents
4.2 ASTM Standards
1
ASTM D5127 — Standard Guide for Ultra Pure Water
Used in the Electronics and Semiconductor Industry
NOTE 1: As listed or revised, all documents cited shall be the
latest publications of adopted standards.
1 American Society for Testing and Materials, 100 Barr Harbor
Drive, West Conshohocken, Pennsylvania 19428-2959, USA.
Telephone: 610.832.9585, Fax: 610.832.9555. Website:
www.astm.org
5 Terminology
5.1 None.
6 Physical Property (for information only)
Density at 25°C
1.83 g/mL
7 Requirements
7.1 The requirements for sulfuric acid for Grades 1
and 2, VLSI Grade, and Tiers B and C are listed in
Table 1.
8 Grade 1 Procedures
NOTE 2: Each laboratory is responsible for verifying the
validity of the method within its own operation.
8.1 Assay — Accurately weigh 1 mL of sample in a
small glass-stoppered conical flask. Cautiously add 30
mL of water, cool, add 0.1 mL of methyl orange
indicator solution, and titrate with standardized 1.0 N
sodium hydroxide to a red to yellow color change.
%Assay
=
mL
×
N
of NaOH
×
4.904
Weight of sample g()
8.2 Color — Dilute 2.0 mL of platinum-cobalt stock
solution (APHA No. 500) to 100 mL with water.
Compare this standard (APHA No. 10) with 100 mL of
sample in Nessler tubes. View vertically over a white
background. The sample must be no darker than the
standard.
8.3 Chloride — Place 40 mL of water in each of two
beakers. To one, add carefully 27 mL (50 g) of sample
and to the other, 27 mL (50 g) of chloride-free sulfuric
acid and 0.005 mg of chloride ion (Cl). Cool to room
temperature and add 1 mL of nitric acid and 1 mL of
silver nitrate reagent solution. Mix well; if necessary,
make the volume of each solution identical by adding
water. After 10 minutes, measure the turbidity of each
solution using a suitable nephelometer. The turbidity in
the sample should be no greater than the standard.
NOTE 3: Prepare chloride-free sulfuric acid in a hood by
gently fuming sulfuric acid in a crucible or dish for at least 30
SEMI C44-0301 © SEMI 1978, 2001 SULFURIC ACID2
minutes. Cool and transfer to a tightly-capped glass bottle for
storage.
8.4 Nitrate — Prepare the following solutions:
Sample Solution A: Cautiously add 27 mL (50 g) of sample
to 1.0 mL of water, dilute to 50 mL with
brucine sulfate reagent solution and
mix.
Control Solution B: Cautiously add 27 mL (50 g) of sample
to 1.0 mL of the standard nitrate
solution containing 0.01 mg of nitrate
ion (NO
3
) per mL, dilute to 50 mL with
brucine sulfate reagent solution and
mix.
Blank Solution C: Use 50 mL of brucine sulfate reagent
solution.
8.4.1 Heat the three solutions in a preheated (boiling)
water bath for 10 minutes. Cool rapidly in an ice bath to
room temperature. Set a photometer at 410 nm and,
using 1-cm cells, adjust the instrument to read zero
absorbance with Blank Solution C in the light path, then
determine the absorbance of Sample Solution A. Adjust
the instrument to read zero absorbance with Sample
Solution A in the light path and determine the
absorbance of Control Solution B. The absorbance of
Sample Solution A should be no greater than that
Control Solution B.
8.5 Phosphate — Evaporate 11 mL (20 g) of sample
to dryness in a platinum dish in a hood. Dissolve the
residue in 25 mL of 0.5 N sulfuric acid. Add 1 mL of
ammonium molybdate reagent solution and 1 mL p-
(methylamino)phenol sulfate reagent solution. Allow to
stand at room temperature for 2 hours. Any blue color
produced should be no greater than that produced when
0.01 mg of phosphate ion (PO
4
) is treated as the sample.
8.6 Arsenic and Antimony (as As) — To 109 mL (200
g) of sample in a beaker, add 5 mL of nitric acid and
evaporate to about 10 mL in a hood. Cool. Cautiously
add 10 mL of water, and again evaporate to about 5
mL. Cool, and cautiously wash into a generator flask
with water to make a volume of 35 mL. Proceed as
described in General Method for Arsenic (and
Antimony) under SEMI C1, Section 3.4.5, starting with
the first sentence which begins: “Swirl the flask...”
Any red color in the silver diethyldithiocarbamate
solution from the sample should be no greater than that
of the standard containing 0.001 mg of arsenic (As).
8.7 Trace Metal Analysis
8.7.1 Gold (Au) — Analyze by graphite atomic
absorption using the manufacturer's recommended
procedure. This technique has been shown to give
satisfactory results using a 1:4 dilution and Zeeman
background correction. Each laboratory must determine
the appropriate dilution and background correction for
its instrument to meet the specification limit.
8.7.2 The following method has given satisfactory
results in determining trace metal impurities at the
value specified for each of the following trace metals:
aluminum (Al), boron (B), calcium (Ca), chromium
(Cr), copper (Cu), iron (Fe), lead (Pb), magnesium
(Mg), manganese (Mn), nickel (Ni), potassium (K),
sodium (Na), tin (Sn), titanium (Ti), and zinc (Zn).
Alternate methods may be used as long as appropriate
studies demonstrate recovery between 75–125% of a
known sample spike for half of the value of each
specified item.
8.7.3 Special Reagents
8.7.3.1 Water — The water used for all the dilution,
calibration and standards should meet at a minimum the
criteria for Type E1.1 in ASTM D5127 in regard to
cation analysis.
8.7.3.2 Indium Internal Standard — Make up the
indium intenal standard solution to a concentration of
20 µg/mL (ppm) from the appropriate concentrated
indium standard solution.
8.7.3.3 Nitric Acid, Ultrapure — Use nitric acid
specified for ultra low metal ion content.
8.7.3.4 1% Nitric Acid Solution — Dilute 10 mL of
ultrapure nitric acid to 1 L using water meeting the
criteria for Type E1.1 in ASTM D5127.
8.7.3.5 2% Nitric Acid Solution — Dilute 20 mL of
ultrapure nitric acid to 1 L using water meeting the
criteria for Type E1.1 in ASTM D5127.
8.7.3.6 Hydrochloric Acid, Ultrapure — Use
hydrochloric acid specified for ultra low metal ion
content.
8.7.3.7 2% Hydrochloric Acid Solution — Dilute 20
mL of ultra-pure hydrochloric acid to 1 L using water
meeting the criteria for Type E1.1 in ASTM D5127.
8.7.4 Sample Preparation
8.7.4.1 Boron — In a clean environment, dilute 1.00 g
sample with 15.0 g of Type E1.1 water and add 15 µL
of the indium internal standard. Run a reagent blank.
8.7.4.2 Tin — In a clean environment, place 100 g of
sulfuric acid in a quartz crucible. Slowly evaporate to
dryness on a hot plate avoiding loss of sample by
effervescence or spattering. Cool. Add 2 mL of high
purity 12 M hydrochloric acid and 10 mL of water.
Cover, and digest on the hot plate for 10 minutes. Cool.
Transfer quantitatively to a 50 mL volumetric flask
using water for rinsing and dilution to volume. Run a
reagent blank.
SULFURIC ACID SEMI C44-0301 © SEMI 1978, 20013
8.7.5 All Other Elements — In a clean environment,
place 100 g of sulfuric acid in a quartz crucible. Slowly
evaporate on a hot plate avoiding loss of sample by
effervescence or spattering until approximately 2 mL of
liquid remains. Cool. Add carefully, 1 mL of high
purity, 70% nitric acid. While maintaining volume,
carefully warm several minutes to dissolve any residue.
Cool. Transfer quantitatively to a 50 mL volumetric
flask using 2% nitric acid and dilute to volume. Run a
reagent blank.
8.7.6 Analysis — Using the prepared solutions and
blanks, analyze boron by inductively coupled plasma
mass spectrometry (ICP/MS). Using the acid sample
and reagent blank, analyze group I elements by flame
atomic absorption spectroscopy. Analyze all other
elements by plasma emission spectroscopy.
NOTE 4: Analysis of dilute sulfuric acid can produce rapid
corrosion of nickel cones commonly used in inductively
coupled plasma mass spectrometry, platinum cones should be
considered as alternative when performing this analysis.
9 Grade 2 Procedures
NOTE 5: Each laboratory is responsible for verifying the
validity of the method within its own operation.
9.1 Non-Metal Impurities — See Section 8, which
contains procedures for the following tests:
Assay
Color (APHA)
Chloride
Nitrate
Phosphate
9.2 Trace Metals Analysis
9.2.1 The following method has given satisfactory
results in determining metal ion impurities at the values
specified for each of the following metals: aluminum
(Al), antimony (Sb), arsenic (As), barium (Ba),
beryllium (Be), bismuth (Bi), boron (B), calcium (Ca),
chromium (Cr), cobalt (Co), copper (Cu), gallium (Ga),
germanium (Ge), gold (Au), iron (Fe), lead (Pb),
lithium (Li), magnesium (Mg), manganese (Mn),
molybdenum (Mo), nickel (Ni), niobium (Nb),
potassium (K), silver (Ag), sodium (Na), strontium (Sr),
tantalum (Ta), tin (Sn), titanium (Ti), vanadium (V),
zinc (Zn), and zirconium (Zr). Alternate methods may
be used as long as appropriate studies demonstrate a
recovery between 75–125% of a known sample spike
for half of the value of each specified element.
9.2.2 Special Reagents
9.2.2.1 Nitric Acid, Ultrapure — Use nitric acid
specified for low metal ion content.
9.2.2.2 1% Nitric Acid Solution — Dilute 10 mL of
ultrapure nitric acid to 1 L using water meeting the
criteria for Type E1.1 in ASTM D5127.
9.2.2.3 Water — The water used for all the dilution,
calibration and standards should meet at a minimum the
criteria for Type E1.1 in ASTM D5127 in regard to
cation analysis.
9.2.2.4 Indium Internal Standard — Make up the
indium intenal standard solution to a concentration of
20 µg/mL (ppm) from the appropriate concentrated
indium standard solution.
9.2.3 Sample Preparation
9.2.3.1 Chromium, Cobalt, Lithium, Manganese,
Nickel, Titanium, Vanadium, and Zinc — In a clean
environment, place 1.00 g of sample into a clean quartz
dish. Slowly evaporate on a hot plate to dryness
avoiding loss of sample by effervescence or spattering.
Dissolve the residue with 5 mL of the 1% nitric acid
solution by heating on a hot plate at low temperature for
several minutes. Cool to room temperature, dilute to 15
mL with 1% nitric acid, add 15 µL of the indium
internal standard, mix well. Run a reagent blank.
9.2.3.2 All Other Elements — In a clean environment,
dilute 1.00 g sample with 15.0 g of Type E1.1 water
and add 15 µL of the indium internal standard. Run a
reagent blank.
9.2.4 Analysis
9.2.4.1 Using the prepared solutions and blanks,
analyze sodium, potassium, calcium and iron by
graphite furnace atomic absorption (GFAA) and the
remaining elements by inductively coupled plasma
mass spectrometry (ICP/MS). For calibration, the
standards are made up with the 1% nitric acid solution
and the indium internal standard such that the final
indium concentration is 20 ng/g. For boron and
tantalum, the standards for calibration must be matrix
matched with equal amounts of sulfuric acid certified to
have both elements below 1 µg/mL in the concentrated
acid.
NOTE 6: Analysis of dilute sulfuric acid can produce rapid
corrosion of nickel cones commonly used in inductively
coupled plasma mass spectrometry, platinum cones should be
considered as alternative when performing this analysis.
10 Grade 3 Procedures
10.1 This section does not apply to this chemical.
11 Grade 4 Procedures
11.1 This section does not apply to this chemical.