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SEMI C35-0301 © SEMI 1979, 2001 NITRIC A CID 2 dryness in a h ood. Dissolv e t he residu e in 10 mL of wate r and 1 m L of dilu te hydrochloric acid (1 + 19); filter if nece ssary. Add 1 mL of barium chloride reagent sol…

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NITRIC ACID SEMI C35-0301 © SEMI 1979, 20011
SEMI C35-0301
SPECIFICATIONS AND GUIDELINE FOR NITRIC ACID
These specifications and this guideline 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
C1.12, C7.6, and C8.6 in their entirety. Originally published in 1979, 1990, and 1992 respectively;
previously published June 1999.
1 Purpose
1.1 The purpose of this document is to standardize
requirements for nitric 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 nitric 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 nitric
acid used in the semiconductor industry.
2.2 These standards do not purport to address safety
issues, if any, associated with their use. It is the
responsibility of the user of these standards 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.
5 Terminology
5.1 None.
6 Physical Property (for information only)
Density at 25°C
1.42 g/mL
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
7 Requirements
7.1 The requirements for nitric acid for Grades 1 and 2
and Tier B 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 a small glass-stoppered
conical flask containing about 15 mL of water. Deliver
from a pipet about 2 mL of the sample near the water
surface, stopper immediately, cool, and reweigh. Dilute
to about 50 mL with water, add 0.10 mL of methyl
orange indicator solution, and titrate with standardized
1 N sodium hydroxide to a red to yellow color change.
% Assay =
mL
×
N
of
N
aOH
×
6.301
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 — Dilute 84 mL (120 g) of sample with
10 mL of water, add 1 mL of silver nitrate reagent
solution, and evaporate to dryness on a steam bath in a
hood. Dissolve the residue in 0.5 mL of ammonium
hydroxide, dilute with 20 mL of water, and add 1.5 mL
of nitric acid. Any turbidity produced should be no
greater than that produced when 0.01 mg of chloride
ion (Cl) is treated as the sample.
8.4 Phosphate — To 35 mL (50 g) of sample add 10
mL of sodium carbonate reagent solution and evaporate
to dryness on a steam bath 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 of 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.
8.5 Sulfate — To 70 mL (100 g) of sample add 10 mL
of sodium carbonate reagent solution and evaporate to
SEMI C35-0301 © SEMI 1979, 2001 NITRIC ACID2
dryness in a hood. Dissolve the residue in 10 mL of
water and 1 mL of dilute hydrochloric acid (1 + 19);
filter if necessary. Add 1 mL of barium chloride reagent
solution, mix, and allow to stand for 10 minutes. Any
turbidity developed should be no greater than that
produced when 0.05 mg of sulfate ion (SO
4
) is treated
as the sample.
8.6 Arsenic and Antimony (as As) — To 141 mL (200
g) of sample in a 400 mL beaker add 5 mL of sulfuric
acid, and evaporate to dense fumes of sulfur trioxide in
a hood. Cool, cautiously add 10 mL of water, and again
evaporate to dense fumes of sulfur trioxide. Cool, and
cautiously wash into a generator flask with water to
make a volume of 35 mL. Proceed as described in the
General Method for Arsenic (and Antimony) under
SEMI C1, Section 3.4.5, starting with the sentence
which begins, "Swirl the flask...." Any red color in the
silver diethyldithiocarbamate solution of 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 Nitric Acid, Ultra Pure — Use nitric acid
specified for ultra low metal ion content.
8.7.3.2 2% Nitric Acid Solution — Dilute 20 mL of
ultra pure nitric 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 In a clean environment, place 250 g of sample
in a PTFE evaporating dish. Slowly evaporate on a hot
plate, avoiding loss of sample by effervescence or
spattering until approximately 2 mL of liquid remains.
Cool, and transfer quantitatively to a 50 mL volumetric
flask using 2% nitric acid for rinsing and dilution to
volume. Run a reagent blank.
8.7.5 Analysis
8.7.5.1 Using the acid sample and reagent blank,
analyze group 1 elements by flame atomic absorption
spectroscopy and all other elements by plasma emission
spectroscopy.
9 Grade 2 Procedures
NOTE 3: 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
Phosphate
Sulfate
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, Ultra Pure — Use nitric acid
specified for low metal ion content.
9.2.2.2 7.0% Nitric Acid Solution — Dilute 20 g of
ultrapure nitric acid to 200 g 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 a
indium internal standard solution to a concentration of
20 µg/mL (ppm) from a appropriate concentrated
indium standard solution.
NITRIC ACID SEMI C35-0301 © SEMI 1979, 20013
9.2.3 Sample Preparation
9.2.3.1 In a clean environment, place 2.00 g of sample
into a tared FEP bottle (30 mL), dilute with Type E1.1
water to a final weight of 20.0 g. Add 20 µL of the
indium internal standard solution. 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 7.0% nitric acid solution
and the indium internal standard such that the final
concentration is 20 ng/g of indium.
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.
12 Grade 5 Procedures
12.1 This section does not apply to this chemical.
13 VLSI Grade Procedures
13.1 This section does not apply to this chemical.
14 Tier A Procedures
14.1 This section does not apply to this chemical.
15 Tier B Procedures
15.1 Standardized test methods are being developed
for all parameters at the purity levels indicated. Until
standardized test methods are published, test
methodology shall be determined by user and producer.
The Process Chemical Committee considers a test
method to be valid only if there is a documented
recovery study showing a recovery of 75–125%.
Recovery is for a known sample spike at 50% of the
specified level.
16 Tier C Procedures
16.1 This section does not apply to this chemical.
17 Tier D Procedures
17.1 This section does not apply to this chemical.
Table 1 Impurity Limits and Other Requirements for Nitric Acid
Previous SEMI Reference # C1.12-96 C7.6-95 C8.6-95
Grade 1 Grade 2 Tier B
(Specification) (Specification) (Guideline)
Assay (HNO
3
) 69.0–70.0% 69.0–70.0% 69.0–70.0%
Color (APHA) 10 max
(see NOTE 1)
10 max 10 max
Chloride (Cl) 0.08 ppm max 80 ppb max 50 ppb max
Phosphate (PO
4
) 0.2 ppm max 200 ppb max 50 ppb max
Sulfate (SO
4
) 0.5 ppm max 500 ppb max 50 ppb max
Aluminum (Al) 0.2 ppm max 5 ppb max 1 ppb max
Antimony (Sb) -- 5 ppb max --
Arsenic (As) -- 10 ppb max --
Arsenic and Antimony (as As) 0.005 ppm max -- 1 ppb max
Barium (Ba) -- 10 ppb max 1 ppb max
Beryllium (Be) -- 10 ppb max 1 ppb max
Bismuth (Bi) -- 10 ppb max 1 ppb max
Boron (B) 0.1 ppm max 10 ppb max 1 ppb max
Cadmium (Cd) -- 5 ppb max 1 ppb max
Calcium (Ca) 0.2 ppm max 10 ppb max 1 ppb max
Chromium (Cr) 0.1 ppm max 10 ppb max 1 ppb max
Cobalt (Co) -- 10 ppb max 1 ppb max
Copper (Cu) 0.05 ppm max 10 ppb max 1 ppb max
Gallium (Ga) -- 10 ppb max 1 ppb max
Germanium (Ge) -- 5 ppb max 1 ppb max