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SEMI C21-0301 © SEMI 1978, 2001 AMMONIUM HY DROXIDE 2 the same volume of the bariu m hydroxide solu tio n is added to 21 m L of the carbon di oxide- free water contain i ng 0.5 m g of anhy drous sodium carbon ate. 8.5 Su…
AMMONIUM HYDROXIDE SEMI C21-0301 © SEMI 1978, 20011
SEMI C21-0301
SPECIFICATIONS AND GUIDELINES FOR AMMONIUM HYDROXIDE
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 on
SEMI OnLine February 2001; to be published March 2001. This document replaces SEMI C1.4, C7.1, C8.1,
C11.1, and C17.1 in their entirety. Originally published in 1978, 1990, 1992, 1994, and 1997 respectively;
previously published June 2000.
1 Purpose
1.1 The purpose of this document is to standardize
requirements for ammonium hydroxide 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 ammonium hydroxide
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
ammonium hydroxide 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 The guideline for VLSI grade ammonium
hydroxide is only applicable for materials that remain
below 25°C during transport and storage.
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
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
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
0.90 g/mL
7 Requirements
7.1 The requirements for ammonium hydroxide for
Grades 1, 2, 3, and 4, and VLSI Grade 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
flask containing about 15 mL of water. Deliver from a
pipet about 2 mL of the sample near the water surface,
stopper immediately, and reweigh. Add 0.1 mL of
methyl red indicator solution and titrate with
standardized 1 N hydrochloric acid to a yellow-to-red
color change.
%Assay
=
mL
×
N
of HCl
×
1.703
Weight of sample g
()
8.2 Appearance — Place 15 mL of the sample in a 20
× 150 mm test tube and compare with water in a similar
tube. Viewed across the column by means of
transmitted light, the two liquids should be equal in
clarity and free from suspended matter.
8.3 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.
8.4 Carbon Dioxide — Dilute 11 mL (10 g) of sample
with 10 mL of carbon dioxide-free water and add 5 mL
of a clear, saturated solution of barium hydroxide. Any
turbidity should be no greater than that produced when
SEMI C21-0301 © SEMI 1978, 2001 AMMONIUM HYDROXIDE2
the same volume of the barium hydroxide solution is
added to 21 mL of the carbon dioxide-free water
containing 0.5 mg of anhydrous sodium carbonate.
8.5 Substances Reducing Permanganate — Dilute 3
mL (2.7 g) of sample with 5 mL of water. Add 50 mL
of 10% sulfuric acid and 0.05 mL of 0.1 N (0.02 M)
potassium permanganate. Boil for 5 minutes. The pink
color should not be entirely discharged.
8.6 Chloride — To 22 mL (20 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 10 mL of water. Add 1 mL of nitric acid.
Filter, if necessary, through a chloride-free filter. Dilute
to 20 mL with water and add 1 mL of silver nitrate
reagent solution. Any turbidity produced should be no
greater than that produced when 0.01 mg of chloride
ion (Cl) is treated as the sample.
8.7 Phosphate — Evaporate 22 mL (20 g) of sample to
dryness on a steam bath in a hood. Take up the residue
with 25 mL of approximately 0.5 N sulfuric acid. Add 1
mL of ammonium molybdate reagent solution and 1 mL
of p-(methylamino)phenol sulfate reagent solution, and
allow to stand for 2 hours at room temperature. Any
blue color should be no greater than that produced
when 0.01 mg of phosphate ion (PO
4
) is treated as the
sample.
8.8 Total Sulfur (as SO
4
) — To 56 mL (50 g) of
sample, add 1 mL of sodium carbonate reagent solution
and evaporate on a steam bath in a hood to a volume of
about 5 mL. Add 2 mL of bromine water and evaporate
to dryness. Dissolve the residue with 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.
8.9 Arsenic and Antimony (as As) — Evaporate 44 mL
(40 g) of sample in a 150 mL beaker to a small volume
in a hood. Cool, cautiously add 10 mL of water and 5
mL of sulfuric acid, and 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 that 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 0.002 mg of arsenic (As).
8.10 Trace Metal Analysis — The following method
has given satisfactory results in determining trace metal
impurities at the value specified for each of the
following trace metal impurities at the value specified
for each of the following trace metals: aluminum (Al),
boron (B), calcium (Ca), chromium (Cr), copper (Cu),
gold (Au), 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.
8.10.1 Special Reagents
8.10.1.1 5% Mannitol Solution — Weigh out 5 g of
Mannitol Powder (ACS Reagents Grade), and dilute to
100 mL using water meeting the criteria for Type E1 in
ASTM D5127. Mannitol solution is subject to attack by
microorganisms and should be carefully monitored for
such contamination.
8.10.1.2 Hydrochloric Acid, Ultra Pure — Use
hydrochloric acid specified for ultra low metal ion
content.
8.10.1.3 2% (v/v) Hydrochloric Acid Solution —
Dilute 20 mL of ultra pure hydrochloric acid to 1 L
using water meeting the criteria for Type E1 in ASTM
D5127.
8.10.2 Sample Preparation
8.10.2.1 In a clean environment, place 250 mL of
aqueous ammonium hydroxide in a PTFE dish. Add 0.5
mL of freshly prepared 5% mannitol solution. Slowly
evaporate on a hot plate, avoiding loss of sample by
effervescence or spattering until approximately 1 mL of
liquid remains. Cool. Add 1 mL of ultra pure, 12 M
hydrochloric acid. Continue heating until approximately
0.5 mL of liquid remains. Cool. Transfer quantitatively
to 50 mL volumetric flask using 2% (v/v) hydrochloric
acid for rinsing and dilution to volume. Run reagent
blank.
8.10.3 Analysis
8.10.3.1 Using the acid sample and reagent blank,
analyze group 1 elements by flame atomic absorption
spectroscopy and all other elements by plasma emission
spectroscopy.
NOTE 3: Due to the uncertainty of the acid concetration in
the liquid residue, the final concentration can be estimated at
approximately 1-2% (v/v). Standard calibration solutions are
to use this same acid concentration.
9 Grade 2 Procedures
NOTE 4: Each laboratory is responsible for verifying the
validity of the method within its own operation.
9.1 Non-Metal Impurities
9.1.1 See Section 8, which contains procedures for the
following tests:
AMMONIUM HYDROXIDE SEMI C21-0301 © SEMI 1978, 20013
Assay
Color (APHA)
Carbon Dioxide
Substances Reducing Permanganate
9.2 Anions
9.2.1 The following method has given satisfactory
results in determining anion impurities at the values
specified for each of the following anions: chloride
(Cl), phosphate (PO
4
), nitrate (NO
3
), and sulfate (SO
4
).
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 anion.
9.2.2 Special Reagents
9.2.2.1 Eluent — Prepare an eluent solution that is 2.2
mM sodium carbonate (Na
2
CO
3
) and 0.75 mM sodium
bicarbonate (NaHCO
3
) in deionized water meeting the
criteria for Type E1.1 in ASTM D5127. Store eluent
under a helium gas blanket.
9.2.2.2 Regenerant — Prepare a 0.025 N sulfuric acid
(H
2
SO
4
) in deionized water meeting the criteria for
Type E1.1 in ASTM D5127.
9.2.2.3 Potassium Carbonate Solution — Prepare a
solution containing 500 mg of reagent grade potassium
carbonate (K
2
CO
3
) into 100 mL of water meeting the
criteria for Type E1.1 in ASTM D5127.
9.2.3 Sample Preparation
9.2.3.1 In a clean environment, place 40 g of sample
into a clean beaker. Add 1 mL of a 5 mg/mL potassium
carbonate solution and evaporate carefully (at 100°C) to
a volume of 0.5 mL. Dilute with water meeting the
criteria for Type E1.1 in ASTM D5127 to a final
volume of 20 mL.
9.2.4 Analysis
9.2.4.1 Using the prepared solutions and blanks,
analyze chloride, nitrate, phosphate, and sulfate by ion
chromatography. Run a reagent blank. Samples and
reagent blanks should be prepared and analyzed in
triplicate.
9.2.4.2 Columns — Precolumn should be AG4-A
(Dionex) or equivalent and Separation column should
be AS4-A (Dionex) or equivalent.
9.3 Trace Metals Analysis
9.3.1 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), boron (B), calcium
(Ca), chromium (Cr), copper (Cu), gold (Au), iron (Fe),
lead (Pb), magnesium (Mg), manganese (Mn), nickel
(Ni), potassium (K), sodium (Na), titanium (Ti), and
zinc (Zn). 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.
9.3.2 Special Reagents
9.3.2.1 Nitric Acid, Ultra Pure — Use nitric acid
specified for low metal ion content.
9.3.2.2 4% Nitric Acid Solution — Dilute 40 mL of
ultra pure nitric acid to 1 L using water meeting the
criteria for Type E1.1 in ASTM D5127.
9.3.2.3 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.
9.3.2.4 Indium Internal Standard — Make up an
indium internal standard solution to a concentration of
20 µg/mL (ppm) from an appropriate concentrated
indium standard solution.
9.3.3 Sample Preparation
9.3.3.1 In a clean environment, evaporate a 50.0 g
sample at low heat until approximately 20 g of the
sample remains. Carefully add 1 mL of the ultra pure
nitric acid and gently warm for several minutes. Cool to
room temperature, add 25 µL of the indium internal
standard, and dilute with Type E1.1 water to a final
weight of 25.0 g.
9.3.4 Analysis
9.3.4.1 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 in 4% nitric acid solution with
final concentration of 20 ng/g of the indium internal
standard. Run a reagent blank.
10 Grade 3 Procedures
NOTE 5: The analytical procedures associated with this
standard are not intended to be the only acceptable procedure
or the best procedure available. The published procedures
have been found to meet the required criteria for acceptance
of an analytical procedure. Alternate procedures may be used
if they meet the same criteria as the published procedures.
NOTE 6: Each laboratory is responsible for verifying the
validity of each method within its own operation.
10.1 Non-Metal Impurities