ASTM F1228-89(1994)E01

Test Method for Oxidizable (Organic) Carbon on Wafer Surfaces (By Persulfate) (Withdrawn 2001)

SCOPE
1.1 This test method covers wafers composed of silicon and other materials used in the semiconductor industry.
1.2 The test method is used to determine the mass of organic (oxidizable) carbon deposited on all exposed wafer surfaces. It is not used to determine total carbon content of the wafer material.
1.3 This test method is limited to carbon determinations in the range from 0.1 to 50 [mu]g/sample. The detection limit is defined as 2 X standard deviation (2[sigma]).
1.4 Volatiles may be lost during storage or handling, or both, of wafers. This test method is not used to quantify volatile organic compounds.
1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.

General Information

• Status: Withdrawn
• Publication Date: 31-Dec-1993
• Withdrawal Date: 09-Jun-2001
• Technical Committee: F01 - Electronics
• Drafting Committee: F01.10 - Contamination Control

Standards Content (Sample)

NOTICE: This standard has either been superseded and replaced by a new version or discontinued.
Contact ASTM International (www.astm.org) for the latest information.
e1
Designation: F 1228 – 89 (Reapproved 1994)
Standard Test Method for
Oxidizable (Organic) Carbon on Wafer Surfaces
(By Persulfate)
This standard is issued under the fixed designation F 1228; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (e) indicates an editorial change since the last revision or reapproval.
e NOTE—Keywords were added editorially in September 1994.
1. Scope lar sieve trap held at room temperature (25 to 28°C). The
carbon dioxide is then thermally desorbed by heating the trap
1.1 This test method covers wafers composed of silicon and
to 200 6 10°C and is carried by nitrogen into a nondispersive
other materials used in the semiconductor industry.
infrared (NDIR) detector sensitized to carbon dioxide. The
1.2 The test method is used to determine the mass of organic
resulting detector signal (less the procedural blank) represents
(oxidizable) carbon deposited on all exposed wafer surfaces. It
the mass of carbon oxide from the wafer surface. The carbon
is not used to determine total carbon content of the wafer
dioxide peak is quantized to carbon mass by either a linearized
material.
calibrated direct readout or comparison with signals resulting
1.3 This test method is limited to carbon determinations in
from oxidation of solutions of carbon standards.
the range from 0.1 to 50 μg/sample. The detection limit is
defined as 2 3 standard deviation (2s).
5. Significance and Use
1.4 Volatiles may be lost during storage or handling, or
5.1 Organic carbon contaminants deposited on semiconduc-
both, of wafers. This test method is not used to quantify
tor wafers can cause losses in product yield. This test method
volatile organic compounds.
makes possible a rapid quantification of surface contamination
1.5 This standard does not purport to address all of the
by carbon. Wafers can be tested before and after various stages
safety concerns, if any, associated with its use. It is the
of the wafer fabrication process. Results can be obtained within
responsibility of the user of this standard to establish appro-
a few minutes of wafer sampling to aid in decisions concerning
priate safety and health practices and determine the applica-
the wafer production process.
bility of regulatory limitations prior to use.
6. Interferences
2. Referenced Documents
6.1 Direct contact of a wafer with the human body or
2.1 ASTM Standards:
materials containing even small amounts of organic carbon
D 1129 Terminology Relating to Water
2 compounds can cause a positive interference. Wafers must be
D 1193 Specification for Reagent Water
handled with tools that have been cleaned of organic carbon.
3. Terminology 6.2 Prolonged exposure of a clean wafer to the atmosphere
can cause a positive interference due to adsorption of organics
3.1 Definitions:
and carbon dioxide from the air or due to particle settling on
3.1.1 For definitions of terms used in this test method, refer
the wafer. Wafers should be tested at time frame relevant to
to Terminology D 1129.
process.
4. Summary of Test Method 6.3 Organic compounds are not oxidized at the same rates.
Compounds may exist that are not completely oxidized in the
4.1 Carbon on wafer surfaces is determined by oxidation to
standard time (4 min) allowed for reaction. In this case, a
carbon dioxide using a persulfate oxidant solution at 100 6
negative interference (loss of recovery) will result and if the
1°C. The wafer is placed in a chamber filled with a clean,
slowly oxidizing compounds in question partition into the
acidified persulfate solution and the heated chamber is sealed.
reaction solution, a positive interference (carry-over) may
Susceptible organic carbon is submitted to a 4 min digestion at
occur with the next sample. Thus, time of reaction must be
100°C to form carbon dioxide in solution. The resulting carbon
demonstrated to be sufficient for complete oxidation of com-
dioxide is purged from solution and concentrated on a molecu-
pounds present. Reaction time may be evaluated by analyzing
a single wafer in replicate (without removing it from the
This test method is under the jurisdiction of ASTM Committee F-1 on
chamber). If the result from the second carbon determination is
Electronics and is the direct responsibility of Subcommittee F01.10 on Contamina-
tion Control Processing. greater than the blank by more than 0.1 μg, carbon was not
Current edition approved May 26, 1989. Published July 1989.
sufficiently oxidized in the first determination. In this case,
Annual Book of ASTM Standards, Vol 11.01.
Copyright © ASTM, 100 Barr Harbor Drive, West Conshohocken, PA 19428-2959, United States.
F 1228
reaction time should be increased 1 min and the replicate test while in-line with the detector is needed. The valving system
repeated with a new wafer until acceptable results are obtained. should be designed to minimize contamination and handling of
6.4 Opening the digestion chamber introduces ambient car- plumbing components. Fig. 3 shows a diagrammatic presenta-
bon dioxide, that must be flushed from the chamber head space tion of a suitable analyzer.
before each analysis. Carbon dioxide left in the head space will 7.5 Tweezers—A pair of clean TFE-fluorocarbon tweezers is
introduce a positive error in the results. needed to transfer wafers to and from the digestion chamber.
7. Apparatus 8. Reagents and Materials
7.1 Sealable Chamber, suitable for maintaining a persulfate 8.1 Purity of Reagents—Reagent grade chemicals shall be
solution at 100 6 1°C without corroding or producing carbon used. Unless otherwise indicated, it is intended that all reagents
dioxide from the chamber materials is necessary. The chamber conform to the specifications of the Committee on Analytical
shall be of a configuration to accept wafers to be analyzed and
Reagents of the American Chemical Society where such
must permit passage of nitrogen purge gas through the con- specifications are available. Inferior grades may cause an
tained solution for purging of carbon dioxide (see Fig. 1).
increase in the procedural blank due to higher concentrations of
˚
7.2 Molecular Sieve Trap—A trap containing 5A molecular carbon contaminants in the reagent.
sieve, 30 to 60-mesh and a method of rapid trap heating
8.2 Purity of Water—Unless otherwise indicated, references
capable of maintaining a trap temperature of 200 6 10°C is to water shall be understood to mean reagent water as defined
required. The trap should rise from 25 to 200°C in less than 30
by Type II of Specification D 1193. This water should contain
s. A stainless steel tube of 3.2-mm outside diameter and less than 0.2 mg/L Total Oxidizable Carbon, (TOC).
2.7-mm inside diameter packed with 15 cm of 30 to 60-mesh
8.3 Acidified Sodium Persulfate (10 %) Solution—Prepare
molecular sieve is suitable as a trap (see Fig. 2). by dissolving 100 6 1 g of sodium persulfate (Na S O ) into
2 2 8
7.3 Non-Dispersive Infrared Detector—A NDIR capable of
1 L of reagent water. Add 5 mL of 85 % phosphoric acid
detecting carbon dioxide in the range of
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