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SEMI C40-0699 © SEMI 1999 POTASSIUM HYDROXIDE, 45 % SOLUTION 2 connected thro ugh a spray trap to a conden ser, the end of w hich dips beneath the surface of 10 mL of 0.1 N hydroch loric acid. For the st andard, take 50 …

POTASSIUM HYDROXIDE, 45% SOLUTION SEMI C40-0699 © SEMI 19991

SEMI C40-0699

SPECIFICATION FOR POTASSIUM HYDROXIDE, 45% SOLUTION

This specification was technically approved by the Global Process Chemicals Committee and is 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.

1 Purpose

1.1 The purpose of this document is to standardize

requirements for 45% potassium hydroxide solution

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

potassium hydroxide, 45% solution 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 45%

potassium hydroxide solution 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 Property (for information only)

6.1 Not applicable.

7 Requirements

7.1 The requirements for 45% potassium hydroxide

solution for Grade 1 are listed in Table 1.

8 Grade 1 Procedures

NOTE 1: Each laboratory is responsible for verifying the

validity of the method within its own operation.

8.1 Assay



Accurately weigh 70 to 80 g of sample in

a closed weighing bottle. Transfer to a 500 mL

volumetric flask, add in carbon dioxide-free water, cool

to 25°C, dilute to the mark with carbon dioxide-free

water, and mix thoroughly. Transfer 25.0 mL of this

solution to a 500 mL glass-stoppered flask, dilute with

175 mL of carbon dioxide-free water, add 5 mL of

barium chloride reagent solution, shake and allow to

stand for five minutes. Add 0.15 mL of

phenolphthalein indicator solution and titrate with

standardized 1 N hydrochloric acid. (Save this solution

for the potassium carbonate test.)

(g) Sample ofWeight

112.2 HCl of N mL

%Assay

××

8.2 Potassium Carbonate (K

)  To the above

titrated solution, add 0. 15 mL of methyl orange

indicator and continue the titration with 1 N

hydrochloric acid, making sure that no insoluble

carbonate remains. The additional hydrochloric acid is

equivalent to that consumed by the potassium

carbonate.

(g) Sample ofWeight

138.2 HCl of N mL

COK % 32

××

8.3 Ammonium Hydroxide Precipitate  Weigh 40 g

of sample into a 250 mL beaker and dissolve in about

100 mL of water.

8.3.1 Cautiously add 26 mL of sulfuric acid to 30 mL

of water in a 150 mL glass beaker, cool; then cautiously

add the mixture to the solution of the sample, and

evaporate to dense fumes. Cool, dissolve the residue in

130 mL of hot water, and add ammonium hydroxide

until the solution is just basic to methyl red.

8.3.2 Heat to boiling, filter, wash with hot water and

ignite. The weight of the residue should not exceed 2

mg.

8.4 Insoluble Matter  Dilute 100 g of sample in 250

mL of carbon dioxide-free water in a 500 mL stoppered

flask and cool to 25°C. The solution should be clear

and colorless. Filter through a tared, medium porosity

filtering crucible and wash thoroughly with hot water.

Dry the crucible at 105°C for 1 hour, cool and weigh

the residue. The weight of the residue should not

exceed 5.0 mg.

8.5 Stock Solution for Sections 8.6 through 8.13 —

Add 100 g of sample to 250 mL of carbon dioxide-free

water and dilute with such water to 500 mL. One mL

contains 0.20 g of sample. Store in a plastic container.

8.6 Nitrogen Compounds (as N)  Dilute 20 mL of

the stock solution with 50 mL of water in a flask

SEMI C40-0699 © SEMI 1999 POTASSIUM HYDROXIDE, 45% SOLUTION2

connected through a spray trap to a condenser, the end

of which dips beneath the surface of 10 mL of 0.1 N

hydrochloric acid. For the standard, take 50 mL of

water in a similar flask, and add 10 mL of the stock

solution and 1 mL of the nitrogen standard solution

(0.01mg N/mL). To each flask add 0.5 g of aluminum

wire in small pieces, allow to stand for 1 hour, and

slowly distill to about 35 mL. To each distillate add 2

mL of freshly boiled 10% sodium hydroxide reagent

solution, dilute with water to 50, add 2 mL of Nessler

reagent, and mix. Any color in the solution of the

sample should not exceed that in the standard.

8.7 Chloride  Dilute l0 mL of the stock solution

with water to 50 mL. Filter, if necessary, through a

chloride-free filter. To 10 mL of this solution, add 5

mL of water, 2 mL of nitric acid, and 1 mL of silver

nitrate reagent solution. Any turbidity developed

should not exceed that produced by 0.02 mg of chloride

(CI) ion in an equal volume of solution containing the

quantities of reagent used in the test.

8.8 Phosphate  To 50 mL of the stock solution, add

15 mL of hydrochloric acid and evaporate to dryness on

a steam bath. Dissolve the residue in 25 mL of 0.5 N

sulfuric acid. Add 1 mL of ammonium molybdate

reagent solution and l mL of p-(methylamino)phenol

sulfate reagent solution. Allow the solution to stand for

2 hours at room temperature. Any blue color developed

should not exceed that produced when 0.02 mg of

phosphate (PO

) ion is treated as the sample.

8.9 Sulfate  To 20 mL of the stock solution, add 5

mL of hydrochloric acid and evaporate to dryness on a

steam bath. Dissolve the residue in 20 mL of water and

evaporate again to dryness. Dissolve the residue in 20

mL of water, filter if necessary, and add 1 mL of dilute

hydrochloric acid (1+19) and 1 mL of barium chloride

reagent solution. Allow to stand for 10 minutes. Any

turbidity developed should not exceed that produced

when 0.04 mg of sulfate (SO

) ion is treated as the

sample.

8.10 Heavy Metals (as Ag)  To 60 mL of the stock

solution cautiously add 15 mL of nitric acid. For the

standard add 0.05 mg of silver ion (Ag) to 10 mL of the

stock solution and cautiously add 15 mL of nitric acid.

Evaporate both solutions to dryness over a low flame or

on an electric hot plate. Dissolve each residue in about

20 mL of water, filter if necessary through a chloride-

free filter, and dilute with water to 25 mL. Adjust the

pH of the standard and sample solutions to between 3

and 4 (using a pH meter) with 1 N acetic acid or

ammonium hydroxide (10% NH

). Dilute each solution

with water to 40 mL and stir. Add 10 mL of freshly

prepared hydrogen sulfide water to each solution and

stir again. Any color developed in the sample should

not exceed that in the standard.

8.11 Iron  Neutralize l0 mL of the stock solution

with hydrochloric acid, using a phenolphthalein

indicator solution, add 2 mL of HCI in excess, and

dilute with water to 50 mL. Add 30 to 50 mg of

ammonium peroxydisulfate crystals and 3 mL of

ammonium thiocyanate reagent solution. Any red color

developed should not exceed that produced when 0.01

mg of iron (Fe) ion is treated as the sample.

8.12 Nickel  Dilute 20 mL of the stock solution to

50 mL with water and neutralize with hydrochloric acid

using a pH meter. Dilute to 85 mL with water and add

ammonium hydroxide to make the solution barely basic

(pH 8). Add 5 mL of bromine water and 5 mL of

alcoholic 1% dimethylgy1oxime solution. Any red

color developed should not exceed that produced when

0.02 mg of nickel (Ni) ion is treated as the sample.

8.13 Sodium  Dilute 10 mL of the stock solution

with water to 100 mL to form the sample solution. To

prepare the standard solution, add 0.6 mg of sodium

(Na) ion to 10 mL of the stock solution and dilute with

water to 100 mL.

8.13.1 Using flame emission spectroscopy, observe

the emission of the standard solution at the 589 nm

sodium line. Observe the emission of the sample

solution at the 589 nm sodium line and also at a

wavelength of 580 nm. The difference between the

intensities observed for the sample solution at 580 nm

and 589 nm should not exceed the difference observed

at 589 nm between the sample solution and standard

solution (see SEMI Cl, Section 3.7, Flame Emission

Spectroscopy).

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.

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 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 Potassium Hydroxide, 45% Solution

Previous SEMI Reference # --

Grade 1

(Specification)

Assay (KOH) 45.0 - 47.0%

Insoluble Matter 50 ppm max

Nitrogen Compounds (as N) 5 ppm max

Ammonium Hydroxide Precipitate 50 ppm max

Chloride (Cl) 50 ppm max

Phosphate (PO

) 2 ppm max

Potassium Carbonate (K

)0.5% max

Sulfate (SO

) 10 ppm max

Heavy Metals (as Ag) 5 ppm max

Iron (Fe) 5 ppm max

Nickel (Ni) 5 ppm max

Sodium (Na) 0.03% max

NOTICE: 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.

SEMI makes no warranties or representations as to the

suitability of the standards set forth herein for any

particular application. The determination of the

suitability of the standard is solely the responsibility of

the user. Users are cautioned to refer to manufacturer’s

instructions, product labels, product data sheets, and

other relevant literature respecting any materials

mentioned herein. These standards are subject to

change without notice.

The user’s attention is called to the possibility that

compliance with this standard may require use of

copyrighted material or of an invention covered by

patent rights. By publication of this standard, SEMI

takes no position respecting the validity of any patent

rights or copyrights asserted in connection with any

item mentioned in this standard. Users of this standard

are expressly advised that determination of any such

patent rights or copyrights, and the risk of infringement

of such rights, are entirely their own responsibility.

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