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SEMI P32-1104 © SEMI 1998, 2004 2 6 Apparatus 6.1 Measurement Equipment 6.1.1 Flam e Atomic Absorption Spectrom eter (F-AAS) and ICP-MS c an be applied to t he dry as hing me thod. 6.1.2 Graphite Furn ace Atomic Absorpti…

SEMI P32-1104 © SEMI 1998, 2004 1

SEMI P32-1104

TEST METHOD FOR DETERMINATION OF TRACE METALS IN

PHOTORESIST

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

responsibility of the Japanese Micropatterning Committee. Current edition approved by the Japanese

Regional Standards Committee on July 23, 2004. Initially available at www.semi.org August 2004; to be

published November 2004. Originally published September 1998.

1 Purpose

1.1 This document describes an outline of a

quantitative analysis method on trace metal

concentration. This standard is intended to promote

communication between users and suppliers.

2 Scope

2.1 This document applies to a measurement of trace

metal concentration in ppb level in photoresist by

instrumental techniques, such as Atomic Absorption

Spectrometry, Plasma Ion Source Mass Spectrometry,

and Inductively Coupled Plasma Atomic Emission

Spectrometry.

2.2 Object metals in this measurement are Al, Ca, Cr,

Cu, Fe, Mg, Mn, Ni, K, and Na.

2.3 Either additional metals or fewer can be agreed

upon between users and suppliers and are added to the

measurement list.

2.4 The following method has given satisfactory results

in determining trace metal impurities at the specified

value for each of the target trace metals. Alternative

methods or conditions may be used as long as

appropriate studies demonstrate recovery between

75%–125% of a known sample spike for half the

specification value. The results should be reported as

within specification (below a certain value) or not in

specification only (SEMI C1).

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.

3 Referenced Standards

3.1 SEMI Standard

SEMI C1 — Guide for the Analysis of Liquid

Chemicals

3.2 ASTM Standard

ASTM D1193 — Standard Specification for Reagent

Water

4 Summary of Method

4.1 Photoresist test solution is prepared by dry ashing

method or direct method. Then trace metals in the test

solution are measured by Atomic Absorption

Spectrometry, Plasma Ion Source Mass Spectrometry,

or Inductively Coupled Plasma Atomic Emission

Spectrometry. The trace metal concentration is

determined using a working curve, which is obtained by

measuring a standard solution.

5 Terminology

5.1 Definitions

5.1.1 blank test — a measurement without the object

photoresist, which is performed under the standard

procedures.

5.1.2 dilution factor — numerical number that

indicates final amount of solution divided by the initial

amount of solution in the preparation of the photoresist

process.

5.1.3 direct method — a sample preparation method

for preparing samples for direct trace metal in

photoresist. The materials are diluted with a solvent and

then analyzed by the appropriate analytical instrument.

5.1.4 dry ashing method — a sample preparation

method for preparing samples used in measuring trace

metals in the photoresist. The photoresist is evaporated

and decomposed to ash by heating. The ash is dissolved

in a volumetric flask with acid and aqueous reagent,

and then analyzed by the appropriate analytical

instrument.

5.1.5 plasma ion source mass spectrometry — a

method that isolates and measures quantitative metal

element by mass spectrometer using plasma as

excitation source. Inductively Coupled Plasma Mass

Spectrometry (ICP-MS) and Microwave Induced

Plasma Mass Spectrometry (MIP-MS) belong to this

category.

5.1.6 working curve — the relationship between known

metal concentrations prepared by standard solutions and

the observed values of instrumental analysis.

SEMI P32-1104 © SEMI 1998, 2004 2

6 Apparatus

6.1 Measurement Equipment

6.1.1 Flame Atomic Absorption Spectrometer (F-AAS)

and ICP-MS can be applied to the dry ashing method.

6.1.2 Graphite Furnace Atomic Absorption

Spectrometer (GF-AAS), Electrothermal Atomization

Atomic Absorption Spectrometer (ETA-AAS), ICP-

MS, MIP-MS, and Inductively Coupled Plasma Atomic

Emission Spectrometer (ICP-AES) can be applied to

the direct method.

6.1.3 Instrument Condition — Recommended

instrumental conditions are summarized in Table 1 for

each target metal.

Table 1 Measurement Equipment and Metal Elements

Plasma Ion Source Mass Spectrometry

Element

Atomic Absorption

Spectroscopy

ICP-MS (Note 1) MIP-MS (Note 2)

ICP-Atomic Emission

Spectrometer

Al 309.2 nm

Al 396.2 nm

Ca 422.7 nm

Ca,

Ca (Note 3)

Ca 393.4 nm

Cr 357.9 nm

359.4 nm

Cr,

(Note 3)

Cr 267.7 nm

283.6 nm

Cu 324.7 nm

Cu,

Cu 324.8 nm

Fe 248.3 nm

Fe,

(Note 3)

Fe,

Fe 259.9 nm

Mg 285.2 nm

Mg,

Mg 279.6 nm

Mn 279.5 nm

Mn (Note 3)

Mn 257.6 nm

Ni 232.0 nm

341.4 nm

Ni,

(Note 3)

Ni,

Ni 221.6 nm

231.6 nm

K 766.5 nm

K (Note 3)

K 766.5 nm

Na 589.0 nm

NOTE 1: ICP-MS — Ar is used as the plasma generation gas.

NOTE 2: MIP-MS — N

is used as the plasma generation gas.

NOTE 3: Beware of interfering ion (see Table 2).

Table 2 Interfering Ions

Object Metal Interfering Ion

7 Vessels, Reagents, and Environment

7.1 Vessel

7.1.1 Quartz glass volumetric flask

7.1.2 Quartz glass measuring pipette

7.1.3 Quartz glass beaker

7.1.4 PTFE vessel

7.1.5 Platinum crucible

7.2 Reagents

7.2.1 DI Water — Resistivity ≥ 18.0 MΩ cm at 25°C

per ASTM D 1193.

7.2.2 Organic Reagent — Use commercially

guaranteed reagent for trace metal analysis.

7.2.3 Inorganic Reagent — Use commercially

guaranteed reagent for trace metal analysis.

7.2.4 Standard Reagent — Use the commercially

guaranteed reagents which have certified trace metals

concentration.

7.3 Environment

7.3.1 The measurement is recommended to be

performed in a clean room or clean zone at constant

temperature. The stability of temperature should be

better than ± 2°C. Dry ashing method should be

performed in a draft chamber with HEPA filter, if

possible.

7.3.2 In the case of volumetric analysis, the

measurement environment is set to the standard

temperature of measuring tools such as volumetric flask

and measuring pipette.

8 Procedures

8.1 Flow Chart of Measurement — Refer to Figure 1

as suggested analysis process.

Figure 1

Flow Chart of Trace Metal Measurement