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SEMI MF1239-0305 © SEMI 2003, 2005 1 SEMI MF1239-0305 TEST METHOD FOR OXYGEN PR ECIPITATION CHARACTERISTICS OF SILICON WAFERS BY MEASUREM ENT OF INTERSTITIAL OXYGEN REDUCTION These test methods were techni cally approved…
SEMI MF1188 © SEMI 2003, 2005 12
A1-4.1.3 Identification of test and reference specimens,
A1-4.1.4 Temperature of the spectrophotometer chamber,
A1-4.1.5 Thickness of test and reference specimens,
A1-4.1.6 Location and size of the illuminated area on the specimen,
A1-4.1.7 Apodization function used (FT-IR instruments),
A1-4.1.8 Spectral full width at half maximum of the absorption peak,
A1-4.1.9 Area of specimen illuminated,
A1-4.1.10 W
p
, wavenumber of the absorption peak, in cm
1
,
A1-4.1.11 The absorption coefficient due to interstitial oxygen,
o
, in cm
1
,
A1-4.1.12 Oxygen concentration, in ppm or in atoms/cm
3
, and
A1-4.1.13 The calibration factor used (IOC-88 recommended).
A1-5 Precision
A1-5.1 The precision of this test method depends upon the thickness of the test specimen and its oxygen content.
The single instrument repeatability of this test method was studied in an international experiment, in which the
oxygen contents of equivalent sets of 20, 2 mm thick samples, with interstitial oxygen content ranging from 5 ppma
to 30 ppma (IOC-88), were measured by 18 different laboratories. The single instrument repeatability of this test
method, pooled over all 20 specimens in the test set, ranged from 0.4 to 1.2% (R1S) for the 18 laboratories in the
study.
1
A1-5.2 The multilaboratory reproducibility for the same sets of test specimens was determined in the same study,
with 18 participating laboratories, to be ± 3% (R1S).
1
A1-6 Bias
A1-6.1 This experiment also included measurements of the absolute oxygen content by a variety of physical
methods. The uncertainty in the absolute determinations of oxygen content in silicon during the Grand Round
Robin results primarily from the uncertainty in the chemical analysis measurements and any variations in the oxygen
content of the various slices used in the test. The first of these is estimated to be about 6%, and the second is
estimated to be much smaller. This uncertainty directly affects the assigned value of the IOC-88 calibration factor.
Errors in this calibration factor cause errors in the value of the derived oxygen content. Therefore, the bias of these
measurements from these sources is estimated not to exceed 6%.
A1-6.2 There is also the possibility of bias because of interfering peaks in the infrared spectrum at the
wavenumbers where the baseline is determined. The magnitude of this bias varies from sample to sample and
cannot be predicted.
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SEMI MF1239-0305 © SEMI 2003, 2005 1
SEMI MF1239-0305
TEST METHOD FOR OXYGEN PRECIPITATION CHARACTERISTICS
OF SILICON WAFERS BY MEASUREMENT OF INTERSTITIAL OXYGEN
REDUCTION
These test methods were technically approved by the Global Silicon Wafer Committee and are the direct
responsibility of the North American Silicon Wafer Committee. Current edition approved for publication by
the North American Regional Standards Committee on December 10, 2004. Initially available at
www.semi.org January 2005; to be published March 2005. Original edition published by ASTM
International as ASTM F 1239-89. Last previous edition SEMI MF1239-02.
1 Purpose
1.1 Oxide precipitates in the bulk of a silicon wafer can act as gettering sites for contamination that may be
introduced during manufacture of circuits and devices. This contamination (usually metallic impurities), if not
gettered, can reduce device manufacturing yields and degrade device or circuit performance. Thus, the oxygen
precipitation characteristics of the silicon wafer can significantly affect both yields and performance.
1.2 Although interstitial oxygen concentration is an important factor in affecting the amount of oxygen precipitation
that occurs in silicon during a specific thermal cycle, the presence of other impurities such as carbon or nitrogen, and
differences in dopant type and density, thermal history, or defect properties of the crystal can also affect the
precipitation characteristics. Thus, it is frequently necessary to choose particular material properties and preparation
techniques to obtain the desired precipitation characteristics for a particular application.
1.3 This test method may be used to compare the oxygen reduction of two or more groups of silicon wafers. This
test method is based on thermal cycles that simulate certain common device processing cycles.
1.3.1 Cycle A, a one-step precipitation cycle, provides an indication of the native nucleation sites present in the as-
received wafers.
1.3.2 Cycle B, a two-step nucleation-precipitation cycle, simulates the precipitation that occurs in normal n-MOS
device processing.
1.4 These test methods may be used to compare qualitatively the precipitation characteristics of two or more groups
of wafers.
1.5 These test methods may also be used to determine the uniformity of oxygen reduction across a wafer (in
conjunction with SEMI MF951) or from wafer to wafer within a lot.
2 Scope
2.1 These test methods cover complementary procedures for testing the oxygen precipitation characteristics of
silicon wafers. It is assumed that the precipitation characteristics are related to the amount of interstitial oxygen lost
during specified thermal cycles.
2.2 These test methods may be applied to any n- or p-type Czochralski silicon wafers of any orientation whose
thickness, resistivity, and surface finish are such as to permit the oxygen concentration to be determined by infrared
absorption and whose oxygen concentration is such as to produce measurable oxygen loss.
2.3 These test methods are not suitable for determining the width or characteristics of a “denuded zone,'' a region
near the surface of a wafer that is essentially free of oxide precipitates.
2.4 Because these test methods are destructive, suitable sampling techniques must be employed.
2.5 Determination of material performance in actual device fabrication situations is beyond the scope of these
methods. However, by comparing the results of these tests with actual device yields and performance, criteria for
selection of specific material characteristics may be established.
2.6 The values stated in SI units are regarded as standard.
SEMI MF1239-0305 © SEMI 2003, 2005 2
NOTICE: This standard does not purport to address safety issues, if any, associated with its use. It is the
responsibility of the user of this standard to establish appropriate safety and health guides and determine the
applicability of regulatory or other limitations prior to use.
3 Limitations
3.1 All factors that affect the infrared absorption measurement (including differences in back surface condition,
instrumental characteristics, and wafer resistivity) may cause errors in the determination of oxygen reduction.
3.2 If significant quantities of oxygen are outdiffused during the thermal cycles, the measured oxygen reduction
may not be representative of the amount of oxygen precipitation.
3.3 If precipitate size varies from sample to sample, the variations in measured oxygen reduction may not be
representative of variations in the number of oxide precipitates that are formed.
3.4 The specified thermal cycles may or may not provide adequate simulation of the cycles used in a particular
device processing sequence. The results obtained in these test methods can serve as predictors of those expected in
actual device processing only to the extent that the simulation is representative of the device process.
4 Referenced Standards
4.1 SEMI Standards
SEMI C28 — Specifications and Guidelines for Hydrofluoric Acid
SEMI C29 — Specifications and Guideline for 4.9% Hydrofluoric Acid 10:1 v/v
SEMI C54 — Specifications and Guidelines for Oxygen
SEMI C59 — Specifications and Guidelines for Nitrogen
SEMI M59 — Terminology for Silicon Technology
SEMI MF951 — Test Method for Determination of Radial Interstitial Oxygen Variation Silicon Wafers
SEMI MF1188 — Test Method for Interstitial Atomic Oxygen Content of Silicon by Infrared Absorption with Short
Baseline
SEMI MF1619 — Test Method for Measurement of Interstitial Oxygen Content of Silicon Wafers by Infrared
Absorption Spectroscopy with p-Polarized Radiation Incident at the Brewster Angle
4.2 ASTM Standard
D 5127 — Guide for Ultra Pure Water Used in the Electronics and Semiconductor Industry
1
4.3 JEITA (formerly JEIDA) Standard
EM-3504 (61) — Standard Test Method for Interstitial Atomic Oxygen Content of Silicon by Infrared Absorption
2
4.4 DIN Standard
50438/1 — Determination of Impurity Content in Silicon by Infrared Absorption: Oxygen
3
NOTICE: Unless otherwise indicated, all documents cited shall be the latest published versions.
5 Terminology
5.1 For definitions of terms relating to silicon technology, refer to SEMI M59.
1 Annual Book of ASTM Standards, Vol 11.01, ASTM International, 100 Barr Harbor Drive, West Conshohocken, PA 19428. Telephone: 610-
832-9500, Fax: 610-832-9555, Website:
www.astm.org
2 Japan Electronics and Information Technology Industries Association, 3
rd
floor, Mitsui Sumitomo Kaijo Bldg. Annex, 11, Kanda-Surugadai 3-
chome, Chiyoda-ku, Tokyo 101-0062, Japan, Telephone: 81.3.3518.6434, Fax: 81.3.3295.8726, Website:
www.jeita.or.jp
.
3 Deutches Institut für Normung e.V., standards are available in both English and German editions from Beuth Verlag GmbH, Burggrafenstrasse
6, 10787 Berlin, Germany, Telephone: 49.30.2601-0, Fax: 49.30.2601.1263, Website:
www.beuth.de
.