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SEMI C2-95 © SEMI 1981 , 1996 1 SEMI C2-9 5 SPECIFICA TIONS FOR ETCHANTS 1 Preface 1.1 The SEMI Com mittee on Chem i c a l Reagents began its efforts on etchants i n 1979. With t his publication, the Committee estab lish…

SEMI C1-0705 © SEMI 1978, 2005 27

NOTICE: 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 or equipment mentioned herein. These standards are subject to change without

notice.

By publication of this standard, Semiconductor Equipment and Materials International (SEMI) takes no position

respecting the validity of any patent rights or copyrights asserted in connection with any items 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.

International), 3081 Zanker Road, San Jose, CA 95134. Reproduction of

the contents in whole or in part is forbidden without express written

consent of SEMI.

SEMI C2-95 © SEMI 1981, 19961

SEMI C2-95

SPECIFICATIONS FOR ETCHANTS

1 Preface

1.1 The SEMI Committee on Chem ical Reagents

began its efforts on etchants in 1979. With this

publication, the Committee establishes definitions for

three major types of etchant mixtures; mixed acid

etchants, buffer oxide etchants, and phosphoric

etchants. Specifications and analytical procedures are

introduced for each type.

1.2 Etchants within all of the requirements can be

described as “meeting SEMI specifications.”

1.3 Where an analytical procedure different from that

provided is substituted by a supplier or user, the burden

of proof is on said supplier or user to confirm the

equivalency.

2 Definitions

2.1 All definitions set forth in SEM I C1, Section 2 are

adopted for SEMI C2.

2.2 Etchant — The exact definitio n of an etchant

mixture shall be set forth as the initial paragraph of its

Standard. The composition shall be expressed as a ratio

of the relative volumes taken of the components in an

assigned order. In the expression, all the relative

volumes shall be reduced to a ratio of the smallest

whole numbers. If a component is absent, its relative

volume shall be taken as zero.

2.3 Composition — The content o f each component of

an etchant shall be expressed on a weight/weight basis

of the 100% component (for example, 100% HF, not

49% HF). Any tolerance allowed for the content of a

component shall be expressed on a weight/weight basis

of that 100% component.

3 General Procedures and G uidelines to

Certain Methods

3.1 The general procedures and guidelines for certain

methods set forth in SEMI C1, Section 3 are adopted

for SEMI C2.

3.2 Determination of Nitric Acid b y Ultraviolet

Absorption Spectrophotometry

3.2.1 Introduction — The photometric determination

of nitric acid in various etchant mixtures is based on the

strong absorption of the nitrate ion in the ultraviolet

region. For this spectral region fused silica (quartz)

cells are required.

3.2.2 Preparation of Calibration Curve — Secure a

bottle of nitric acid (70%) and determine its assay in

duplicate. Accurately weigh 2.8 to 3.0 g dilute with 100

mL of water, add 10 drops of phenolphthalein indicator

solution to each solution, and titrate with standardized 1

N sodium hydroxide solution to a pink end-point.

(g) Sample ofWeight

6.302NaOH of mL

)( Acid Nitric %

××

If the results do not differ by more than 0.2%, average

them. Otherwise, repeat the analysis.

3.2.3 In five previously tared weigh ing bottles,

accurately weigh about 1.0, 1.2, 1.4, 1.6 and 1.8 g of

the previously assayed 70% nitric acid. Calculate the

weight, in grams, of 100% nitric acid present in each of

these five standards. Quantitatively transfer each

standard to a separate 100 mL volumetric flask, dilute

to volume with water, and mix thoroughly.

3.2.4 Following the manufacturer’s directions, ready a

spectrophotometer and set the wavelength to 302 nm.

Measure the absorbance of each standard versus water

using a 1 cm fused silica cell. On (linear) coordinate

graph paper plot the absorbance versus the weight, in

grams, of 100% nitric acid for each standard. Draw the

best-fitting straight line through the points.

3.2.5 Application to Acid Etch Mixtu res — Proceed as

given under the Standard for the relevant etchant.

4 Reagent and Standard So lutions

4.1 The reagent and standard solutions set forth in

SEMI C1, Section 4 are adopted for SEMI C2.

4.2 Acetate Buffer for Hydrofluoric Acid

Determination — Dissolve 106 g of sodium acetate

trihydrate, CH

COONa•3H

O, and 137 g of ammonium

acetate, CH

COOHN

, in about 700 mL of water. Add

5.1 mL of glacial acetic acid, adjust to pH 5.5-6.6 with

dilute ammonium hydroxide (10% NH

) or dilute acetic

acid (20%), and dilute to 1000 mL with water.

4.3 Aluminum Chloride Standard Solution

Preparation — Dissolve 40.0 g of aluminum chloride

hexahydrate, AlCl

•6H

O, in about 700 mL of water

and 0.5 mL of hydrochloric acid contained in a 1000

mL volumetric flask; dilute to volume with water, and

mix thoroughly.

4.3.1 Standardization — Transfer 1.5 mL of hydro-

fluoric acid to a 250 mL polyethylene beaker containing

50 mL of water. Add 10 drops of phenolphthalein

indicator solution. With magnetic stirring, titrate with

standarized 1N sodium hydroxide solution to a pink

endpoint. Record the volume of base delivered (A).

Add 25 mL of Acetate Buffer for Hydrofluoric Acid

Determination and 1 g of Eriochrome Cyanine R

indicator mixture; mix thoroughly. With magnetic

stirring, titrate with the aluminum chloride solution to a

pink-purple endpoint. Record the volume of this

solution delivered (B).

soln. AlCl of B

2.001NaOH of A

Factor HF

××

4.4 Eriochrome Cyanine A Indicat or Mixture — Using

a mortar and pestle, thoroughly grind and mix 0.1 g of

Eriochrome Cyanine R (C.I. 43820) with 100 g of

potassium nitrate.

5 Safety

Because of the continuing evolution of safety

precautions, it is impossible in this publication to

provide definite statements relating to the safe handling

of individual etchants. The user is referred to product

labels, product and safety data sheets, government

regulations, and other relevant literature.

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.

International), 3081 Zanker Road, San Jose, CA 95134. Reproduction o

the contents in whole or in part is forbidden without express written

consent of SEMI.