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SEMI P12-0997 © SEMI 1991 , 1997 1 SEMI P12-0997 DETERMINA TION OF IRON, ZINC, CA LCIUM, M A GNESIUM, COPPER, BORON, ALUMI NUM, CHROMIUM, MANGANESE, AND NICKEL IN POSITIVE PHOTORESISTS BY INDUCTIVELY COUPLED PLASMA EMISS…

SEMI P11-0997 © SEMI 1991, 19971

SEMI P11-0997

DETERMINATION OF TOTAL NORMALITY FOR ALKALINE

DEVELOPER SOLUTIONS

1 Scope

1.1 An acid-base potentiometric titration to single or

multiple inflection points is performed on an automatic

recording titrator using standardized hydrochloric acid

as the titrant. The normality (meq/mL) is then

calculated by the titrator using the data obtained.

2 Apparatus

2.1 Autotitrator

2.2 Glass combination electrode

2.3 Class A grade volumetric pipets in 1 to 25 mL

sizes

2.4 250 mL beakers

3 Reagents

3.1 1.0 N Hydrochloric acid (from concentrate or

ready to use 1.0 N)

3.2 Primary Standard — High-purity sodium

carbonate is available from most chemical supply

houses, but must be dried at 400 degree centigrade

before use. TMAH (tris (hydroxymethyl)

aminomethane) is also available from the National

Institute of Standards and Technology (Standard

Reference Material 723a) for this purpose.

3.3 Buffer solutions, pH 4.0, 7.0, 10.0.

4 Procedure

4.1 Standardize the 1.0 N Hydrochloric acid with the

primary standard.

4.2 Standardize the titrator by performing a two point

calibration with pH 4.0, 7.0, and 10.0 buffer.

4.3 Pipette an appropriate aliquot (1 to 25 mL) of

sample into a 250 mL beaker containing a magnetic stir

bar. Sample size should be determined according to the

expected normality and the amount of titrant to be

dispensed that will give the optimum precision and

accuracy. Generally this is between one-half and three-

quarters the capacity of the burette. (See the instrument

manual for the recommended optimum range.)

4.4 Add deionized water to bring the volume to

approximately 150 mL.

4.5 Without delay (to prevent carbon dioxide

absorption), begin stirring without a vortex and titrate

to beyond the inflection endpoint.

4.6 Determine the exact endpoint and record the

volume of titrant consumed at the middle of the

inflection endpoint. This will be done automatically on

most newer digital titrators. On analog titrators, the

inflection point can be determined by using the first

derivative mode, or accurately determining the middle

of the inflection.

5 Calculation

5.1 Calculate the normality of the sample by the

following equation.

ormality (N) =

Volume of titrant (mL) × Normality of titrant (N.HCL)

Sample Volume (mL)

NOTICE: These standards do not purport to address

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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

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suitability of the standard is solely the responsibility of

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

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other relevant literature respecting any materials

mentioned herein. These standards are subject to

change without notice.

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SEMI P12-0997 © SEMI 1991, 19971

SEMI P12-0997

DETERMINATION OF IRON, ZINC, CALCIUM, MAGNESIUM, COPPER,

BORON, ALUMINUM, CHROMIUM, MANGANESE, AND NICKEL IN

POSITIVE PHOTORESISTS BY INDUCTIVELY COUPLED PLASMA

EMISSION SPECTROSCOPY (ICP)

1 Scope

1.1 This procedure is an ICP plasma emission analysis

for determination of iron, zinc, calcium, magnesium,

copper, boron, aluminum, chromium, manganese, and

nickel in photoresist. The applicable concentration

range is 0.1 to 1 ppm when the sample is diluted 1 to 4.

The precision was found to be within 0.1 ppm in a

round robin analysis between four laboratories.

2 Spectrometer

2.1 A grating instrument with resolution sufficient to

separate the analytical emission lines in Table 1 is

required.

Table 1 Analytical Lines of the Elements

Elements

Analytical

Line, nm Elements

Analytical

Line, nm

Aluminum 309.271 Magnesium 285.213

Calcium 317.933 Nickel 231.604

Copper 324.754 Zinc 213.856

Iron 239.562 Chromium 283.563

Boron 208.960 Manganese 257.610

3 Sample Preparation

3.1 The sample is diluted 1/4 (1 part of sample plus 3

parts of solvent weight/weight) in 2-methoxyethanol or

another suitable solvent for positive resist. The solvent

should contain less than 0.03 ppm of the above

elements.

4 Standards

4.1 The standards should be weight/weight (mg/kg)

and should be diluted weight/weight since results will

be expressed in mg/kg.

4.2 The standards are prepared by diluting a

concentrated standard of organic-soluble metals in 2-

methoxyethanol or other suitable solvent. For example,

a 500 ppm standard is diluted to 50 ppm with xylene.

This solution is then diluted to 0.25 ppm with 2-

methoxythanol.

5 Plasma Conditions

5.1 The sample is pumped on the region of 0.7

mL/min, usually with a perstaltic pump attached to the

nebulizer. Choose a tubing that is not attacked by

methyl cellosolve (for example, polytetrafluoro-

ethylene). The argon plasma flow rate and RF power

should be optimized for the sample using settings

recommended in the manufacturer’s manual. Generally,

a plasma gas flow rate of 16 1/min. is necessary to

ionize organic solutions and an RF power of 1.7 watts

is required.

6 Quantitation

6.1 The detector gain is set by measuring the 0.25 ppm

standard. The background is measured with the solvent

and several sample measures. The standard and blank

should be run intermittently to satisfy reasonable

precision. Standard and sample readings should be

repeatable within 0.03 ppm. The effect of sample

viscosity on delivery of diluted resist to the plasma was

not found to be a factor for the resist tested for this

procedure. This effect can be checked by adding an

internal standard of an element known not to be present

in the resist (such as Yttrium) at ppm and checking the

emission response vs. external 1 ppm Yttrium standard

in the diluting solvent.

7 Calculation

7.1 ppm element (mg/kg = ppm measured × delution

factor (weight/weight)

7.2 Detection Limit — The detection limit is a

function of the dilution factor and can vary by

instrument. The dilution factor should be taken into

account in calculation of detection limit.

7.2.1 Detection limit (ppm) = s × dilution factor where

s = standard deviation of instrument readings in ppm.