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SEMI C26-0699 E © SEMI 19 83, 2000 HEXAMETH YLDISIL AZANE 2 8.6 U V Absorbance — A UV s can i s obtained on all HMDS electronic grade material to determine if any UV absorbing impurities are p resent: specifically toluen…
HEXAMETHYLDISILAZANE SEMI C26-0699
E
© SEMI 1983, 20001
SEMI C26-0699
E
SPECIFICATION AND GUIDELINE FOR HEXAMETHYLDISILAZANE
(HMDS)
This specification and 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 April 23, 1999. Initially available on SEMI
OnLine May 1999; to be published June 1999. This document replaces SEMI C1.23 and C7.10 in their
entirety. Originally published in 1983 and 1991 respectively.
E
This document was editorially modified in April 2000 to correct a formatting error. Changes were made to
Table 1.
1 Purpose
1.1 The purpose of this document is to standardize
requirements for hexamethyldisilazane 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 hexamethyldisilazane
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
hexamethyldisilazane used in the semiconductor
industry.
3 Limitations
3.1 None.
4 Referenced Documents
SEMI C1 — Specifications for Reagents
5 Terminology
5.1 None.
6 Physical Properties (for in formation only)
Density at 25°C
0.77 g/mL
Boiling Point
126°C
7 Requirements
7.1 The requirements for hexamethyldisilazane for
Grade 1 and Tier A are listed in Table 1.
8 Grade 1 Procedures
8.1 Assay — Analyze the sample by gas
chromatography (see SEMI C1, Section 3.1, Guidelines
for Assay by Wide Bore Columns Gas
Chromatography). The parameters cited have given
satisfactory results.
Column: 30 meter × 530 micon I.D. fused silica
capillary, coated with 5 micron film of DB-1 or
equivalent (100% methylsilicone which has been
bonded and cross linked).
Column Temperature: 40°C isothermal for 2 minutes,
then programmed to 220°C at 10°C/min, and isothermal
for 10 minutes.
Injector Temperature:
200°C
Detector Temperature:
300°C
Sample Size:
0.4 µL
Carrier Gas: Helium at 8 mL/min
Detector: Thermal Conductivity
Approximate Retention Times (min):
Hexamethyldisilazane 14.3
8.2 Trailing Impurities — Use the chromatogram
developed in the assay (see Section 8.1). With the
relative retention time for hexamethyldisilazane taken
as 1.0, establish the integrated area percents for trailing
impurities with relative retention times from 1.3 to 4.0.
The total of such trailing impurities should not exceed
0.1%.
8.3 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.
8.4 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 should be no darker than the
standard.
8.5 Residue After Evaporation — Evaporate 130 mL
(100 g) of sample to dryness in a hood. Dry at 105°C
for one hour, cool in a desiccator, and weigh (see SEMI
C1, Section 3.3, Determination of Residue After
Evaporation).
SEMI C26-0699
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© SEMI 1983, 2000 HEXAMETHYLDISILAZANE2
8.6 UV Absorbance — A UV scan is obtained on all
HMDS electronic grade material to determine if any
UV absorbing impurities are present: specifically
toluene.
8.6.1 Equipment — Bausch and Lomb Spectronic
2000 Spectrophotometer or other double beam
instrument capable of measurements at 270 nm. Cells -
1 cm path length.
8.6.2 Reagents — FC-113 and methanol for UV cell
cleaning.
8.6.3 Procedure — Using water as the reference and
sample cells, establish the baseline between 300 and
270 nm. Remove the water sample from the sample
path and replace it with the HMDS sample. Read the
absorbance between 300 and 270 nm. The absorbance
at 270 nm should read 0.07 to 0.25.
NOTE 1: Oxygen will contribute to the UV absorbance.
NOTE 2: The sample must be at ambient temperature.
NOTE 3: The UV absorbance will increase or decrease with
time.
NOTE 4: HMDS is flammable and corrosive.
8.7 Chloride — To a 500 mL separatory funnel, add
260 mL (200 g) of sample, 20 mL of water, and 1 mL
of sodium hydroxide reagent solution. Shake well for
30 seconds and allow the two layers to separate.
Carefully draw off the aqueous (lower) layer into a 250
mL beaker. Repeat the extraction five times and
combine the six aqueous extracts. Add 2 mL of nitric
acid to acidify the solution and arrange the beaker for
magnetic stirring.
8.7.1 Using a pH meter fitted with a silver billet
electrode (Beckman #89261, Corning #476065, or
equivalent) and a silver/silver chloride reference
electrode, determine the apparent pH versus mL
readings while titrating the continuously stirred sample
solution with 0.01 M methanolic silver nitrate solution.
Add the silver nitrate solution in 0.1-0.2 mL increments
from a 10 mL buret. Run a total blank. Plot the titration
data on linear graph paper or use the second-derivative
method to establish the endpoint.
ppm Chloride Cl
()
=
mL sample - mL blank(
)
×
M of AgNO
3
×
35,460
Weight of sample g
()
8.7.2 Standard Silver Nitrate in Methanol Solution —
Dissolve 1.700 grams of silver nitrate in absolute
methanol and dilute to 1000 mL. Store this solution in
an amber bottle and standardize immediately before use
against a standard sodium chloride (NaCl) solution
using the above second-derivative method.
8.8 Heavy Metals (as Pb) — Evaporate 130 mL (100
g) of sample to dryness in a hood. Dissolve the residue
in 3 mL of dilute hydrochloric acid (1 + 1) and dilute
with water to 15 mL. If necessary, filter through a small
filter, washing the evaporating dish and filter with 10
mL of water. Dilute to 25 mL with water. For the
standard, dilute a solution containing 0.01 mg of lead
ion (Pb) and 3 mL of dilute hydrochloric acid (1 + 1) to
25 mL with water. Adjust the pH of both solutions to
between 3 and 4 (using a pH meter) with dilute
ammonium hydroxide (10% NH
3
) or with 1 N acetic
acid, and dilute with water to 40 mL. To each solution,
add 10 mL of freshly prepared hydrogen sulfide water
and compare. The sample solution should be no darker
than the standard.
8.9 Arsenic and Antimony (as As) — To a 500 mL
separatory funnel, add 260 mL (200 g) of sample, 20
mL of water, and 1 mL of sodium hydroxide reagent
solution. Shake well for 30 seconds and allow the two
layers to separate. Carefully draw off the aqueous
(lower) layer into a 150 mL beaker. Repeat the
extraction twice more, combining the three aqueous
extracts.
8.9.1 Add 15 mL of nitric acid and 5 mL of sulfuric
acid and evaporate to dense fumes of sulfur trioxide.
Cool, cautiously add 10 mL of water, and re-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
not exceed that for the standard containing 0.002 mg of
arsenic (As).
8.10 Trace Elements — By a suitable emission
spectrographic procedure, determine for each of the
specified trace elements that its content is not greater
than the stated specification limit (see SEMI C1,
Section 3.5, Guidelines for Determination of Trace
Elements by Emission Spectrography).
9 Grade 2 Procedures
9.1 This section does not apply to this chemical.
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.
HEXAMETHYLDISILAZANE SEMI C26-0699
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© SEMI 1983, 20003
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 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 Chemicals 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.
15 Tier B Procedures
15.1 This section does not apply to this chemical.
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 Hexamethyldisilazane
Previous SEMI Reference # C1.23-94 C7.10-94
Grade 1 Tier A
(Specification) (Guideline)
Assay 99.0% 99.5% min
Color (APHA) 10 max 10 max
Trailing Impurities (area % max) 0.1% 0.2%
Residue after Evaporation 10 ppm max 10 ppm max
UV absorbance units at 270 nm 0.25 max 0.25 max
Turbidity 1.0 NTU units 1.0 NTU units max
Chloride (Cl) 2 ppm max 0.3 ppm max
Aluminum (Al) 0.1 ppm max 10 ppb max
Antimony (Sb) -- 10 ppb max
Arsenic (As) -- 10 ppb max
Arsenic and Antimony (as As) 10 ppb max --
Barium (Ba) -- 10 ppb max
Beryllium (Be) -- 10 ppb max
Bismuth (Bi) -- 10 ppb max
Boron (B) 0.1 ppm max 10 ppb max
Cadmium (Cd) -- 10 ppb max
Calcium (Ca) 0.1 ppm max 10 ppb max
Chromium (Cr) -- 10 ppb max
Cobalt (Co) -- 10 ppb max
Copper (Cu) 0.1 ppm max 10 ppb max
Gallium (Ga) 0.1 ppm max 10 ppb max
Germanium (Ge) 0.1 ppm max 10 ppb max
Gold (Au) 0.1 ppm max 10 ppb max
Iron (Fe) 0.05 ppm max 10 ppb max
Lead (Pb) 0.1 ppm max 10 ppb max
Lithium (Li) 0.1 ppm max 10 ppb max
Magnesium (Mg) 0.1 ppm max 10 ppb max
Manganese (Mn) -- 10 ppb max
Molybdenum (Mo) -- 10 ppb max
Nickel (Ni) 0.1 ppm max 10 ppb max
Potassium (K) 0.1 ppm max 10 ppb max