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SEMI P13-91 © SEMI 1991, 2004 1 SEMI P13-91 (Reapproved 1104) DETERMINATION OF SODIUM AN D POTASSIUM IN POSITIVE PHOTORESISTS BY ATOMIC AB SORPTION SPECTROSCOPY This standard was techn ically approved by the Global Micro…

SEMI P12-0997 © SEMI 1991, 1997 2

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.

SEMI P13-91 © SEMI 1991, 2004 1

SEMI P13-91 (Reapproved 1104)

DETERMINATION OF SODIUM AND POTASSIUM IN POSITIVE

PHOTORESISTS BY ATOMIC ABSORPTION SPECTROSCOPY

This standard was technically approved by the Global Micropatterning Committee and is the direct

responsibility of the North American Micropatterning Committee. Current edition approved by the North

American Regional Standards Committee on July 11, 2004. Initially available at www.semi.org September

2004; to be published November 2004. Originally published in 1991.

1 Scope

1.1 This procedure is a flame atomic absorption

analytical method for sodium and potassium analysis in

photoresist. The applicable concentration range is 0.1 to

1 ppm when the sample is diluted one to four. The

precision was found to be within 0.1 ppm in a round-

robin analysis between four laboratories.

NOTICE: 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 or other limitations prior

to use.

2 Referenced Standards

2.1 None.

3 Terminology

3.1.1 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.

4 Atomic Absorption Spectrometer

4.1 The analytical wavelength for sodium is 589.0 nm

and for potassium is 766.0 nm. The instrument

conditions (i.e., slit width, burner gas flow rates) should

be set according to the manufacturer’s manual (the fuel

flow should be set to approximately 1/2 the air flow to

optimize for organic solvent). Optimize the nebulizer

and lamp alignment to maximize the absorbance of the

1 ppm standard.

5 Sample Preparation

5.1 The sample should be diluted 1/4 (1 part resist and

3 parts of solvents weight/weight) in 2-methoxyethanol

or another suitable solvent for positive resist. The

solvent should contain less than 0.1 ppm of the element

being analyzed.

6 Standards

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

and should be diluted weight/weight since results will

be expressed in mg/kg.

6.2 The standards are prepared by diluting a

concentrated stock of organic-soluble sodium and

potassium. For example, a 500 ppm standard of sodium

is diluted to 50 ppm with reagent xylene. This solution

is then diluted to 1 ppm with 2-methoxyethanol or

another suitable solvent.

7 Procedure

7.1 Set the absorbance reading to zero with the flame

ignited and no sample aspirating. Measure the

absorbance of the solvent blank. It should not be more

than 0.04. Measure the absorbance of the 1 ppm

standard and samples. The absorbance of the standard

should be in the region of 0.4. Duplicate sample and

standard readings should be within 0.01 absorbance. A

recovery of 88% was determined when a 1 ppm

potassium internal standard was added to the resist

tested. The effect of viscosity on delivery to the burner

can be determined by adding 2 ppm of a potassium

internal standard to the sample and checking the

absorbance versus an external 2 ppm potassium

standard in the diluting solvent. The potassium level in

the resist, if any, should be subtracted.

8 Calculation

pm (mg/kg) =

Abs. Sample  ppm Standard  dilution factor  R

Abs. Standard

R = Recovery factor due to sample viscosity if

applicable, for example 1.136 in above example.

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

standard deviation of instrument “readings” in ppm.

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.