ASTM F1366-92(2002)
(Test Method)Standard Test Method for Measuring Oxygen Concentration in Heavily Doped Silicon Substrates by Secondary Ion Mass Spectrometry (Withdrawn 2003)
Standard Test Method for Measuring Oxygen Concentration in Heavily Doped Silicon Substrates by Secondary Ion Mass Spectrometry (Withdrawn 2003)
SCOPE
This standard was transferred to SEMI (www.semi.org) May 2003
1.1 This test method covers the determination of total oxygen concentration in the bulk of single crystal silicon substrates using secondary ion mass spectrometry (SIMS).
1.2 This test method can be used for silicon in which the dopant concentrations are less than 0.2 % (1 X 1020 atoms/cm3) for boron, antimony, arsenic, and phosphorus (see Test Method F 723). This test method is especially applicable for silicon that has resistivity between 0.0012 and 1.0 Ω-cm for p-type silicon and between 0.008 and 0.2 -cm for n-type silicon (see Test Methods F 43).
1.3 This test method can be used for silicon in which the oxygen content is greater than the SIMS instrumental oxygen background as measured in a float zone silicon sample, but the test method has a useful precision especially when the oxygen content is much greater (approximately 10x to 20x) than the measured oxygen background in the float zone silicon.
1.4 This test method is complementary to infrared absorption spectroscopy that can be used for the measurement of interstitial oxygen in silicon that has resistivity greater than 1.0 Ω-cm for p-type silicon and greater than 0.1 -cm for n-type silicon (see Test Method F 1188). The infrared absorption measurement can be extended to between 0.02 and 0.1 Ω-cm for n-type silicon with minor changes in the measurement procedure.
1.5 In principle, different sample surfaces can be used, but the precision estimate was taken from data on chemical-mechanical polished surfaces.
1.6 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
Relations
Standards Content (Sample)
NOTICE: This standard has either been superceded and replaced by a new version or discontinued.
Contact ASTM International (www.astm.org) for the latest information.
Designation: F 1366 – 92 (Reapproved 2002)
Standard Test Method for
Measuring Oxygen Concentration in Heavily Doped Silicon
Substrates by Secondary Ion Mass Spectrometry
This standard is issued under the fixed designation F 1366; 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.
1. Scope E 122 Practice for Choice of Sample Size to Estimate a
Measure of Quality for a Lot or Process
1.1 This test method covers the determination of total
F 43 Test Methods for Resistivity of Semiconductor Mate-
oxygen concentration in the bulk of single crystal silicon
rials
substrates using secondary ion mass spectrometry (SIMS).
F 723 Practice for Conversion Between Resistivity and
1.2 This test method can be used for silicon in which the
Dopant Density for Arsenic-Doped, Boron-Doped, and
dopant concentrations are less than 0.2 % (1 3 10 atoms/
Phosphorus-Doped Silicon
cm ) for boron, antimony, arsenic, and phosphorus (see Test
F 1188 Test Method for Interstitial Atomic Oxygen Content
Method F 723). This test method is especially applicable for
of Silicon by Infrared Absorption
silicon that has resistivity between 0.0012 and 1.0 V-cm for
p-type silicon and between 0.008 and 0.2 V-cm for n-type
3. Terminology
silicon (see Test Methods F 43).
3.1 Definitions of Terms Specific to This Standard:
1.3 This test method can be used for silicon in which the
3.1.1 ion mass spectrometry—the separation and counting
oxygen content is greater than the SIMS instrumental oxygen
of ions by their mass-to-charge ratio.
background as measured in a float zone silicon sample, but the
3.1.2 primary ions—ions created and focussed by an ion
test method has a useful precision especially when the oxygen
gun onto the specimen surface to sputter ionize surface atoms.
content is much greater (approximately 103 to 203) than the
3.1.3 secondary ions—ions that leave the specimen surface
measured oxygen background in the float zone silicon.
as a result of the primary ion beam sputter ionizing the
1.4 This test method is complementary to infrared absorp-
specimen surface atoms.
tion spectroscopy that can be used for the measurement of
3.1.4 secondary ion mass spectrometry—mass spectrometry
interstitial oxygen in silicon that has resistivity greater than 1.0
performed upon secondary ions from the specimen surface.
V-cm for p-type silicon and greater than 0.1 V-cm for n-type
silicon (see Test Method F 1188). The infrared absorption
4. Summary of Test Method
measurement can be extended to between 0.02 and 0.1 V-cm
4.1 SIMS is utilized to determine the bulk concentration of
for n-type silicon with minor changes in the measurement
2 oxygen in single crystal silicon substrate. Specimens of single
procedure.
crystal silicon (one float-zone silicon specimen, two calibration
1.5 In principle, different sample surfaces can be used, but
specimens, and the test specimen) are loaded into a sample
the precision estimate was taken from data on chemical-
holder. The holder with the specimens is baked at 100°C in air
mechanical polished surfaces.
for 1 h and then transferred into the analysis chamber of the
1.6 This standard does not purport to address all of the
SIMS instrument. A cesium primary ion beam is used to
safety concerns, if any, associated with its use. It is the
bombard each specimen. The negative secondary ions are mass
responsibility of the user of this standard to establish appro-
analyzed. The specimens are presputtered sequentially to
priate safety and health practices and determine the applica-
reduce the instrumental oxygen background. The specimens
bility of regulatory limitations prior to use.
are then analyzed, in locations different from the presputtering
2. Referenced Documents locations, for oxygen and silicon in a sequential manner
throughout the holder. Three measurement passes are made
2.1 ASTM Standards:
through the holder. The ratio of the measured oxygen and
− −
silicon secondary ion intensities (O /Si ) is calculated for each
This test method is under the jurisdiction of ASTM Committee F01 on specimen. The relative standard deviation (RSD) of the ratio is
Electronics and is the direct responsibility of Subcommittee F01.06 on Silicon
then calculated for each specimen. If any specimen other than
Materials and Process Control.
Current edition approved Jan. 15, 1992. Published March 1992.
Hill, D. E., “Determination of Interstitial Oxygen Concentration in Low-
Resistivity n-type Silicon Wafers by Infrared Absorption Measurements,” Journal of Annual Book of ASTM Standards, Vol 14.02.
the Electrochemical Society, Vol 137, 1990, p. 3926. Annual Book of ASTM Standards, Vol 10.05.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
NOTICE: This standard has either been superceded and replaced by a new version or discontinued.
Contact ASTM International (www.astm.org) for the latest information.
F 1366 – 92 (2002)
the float zone specimen has a RSD of the ratio greater than 7.1.1 The SIMS instrument should be adequately prepared
3 %, more analyses are performed. The SIMS average O/Si (that is, baked) so as to provide the lowest possible instrumen-
ratios are then converted to infrared-equivalent concentrations tal background.
,
5 6
by utilizing either the load-line calibration method or the 7.2 Cryopane1, liquid nitrogen- or liquid helium-cooled,
load factor calibration method with the calibration specimens which surrounds the test specimen holder in the analysis
in the load. chamber.
7.3 Test Specimen Holder.
5. Significance and Use
7.4 Oven, for baking test specimen holder.
5.1 SIMS can measure the oxygen concentration in heavily-
8. Sampling
doped silicon substrates used for epitaxial silicon where the
8.1 Since this procedure is destructive in nature, a sampling
free carrier concentration obscures the infrared absorption and
procedure must be used to evaluate the characteristics of a
prevents the normal use of the infrared measurement as a
group of silicon wafers. No general sampling procedure is
characterization technique for the commercial production of
included as part of this test method, because the most suitable
silicon.
sampling plan will vary considerably depending upon indi-
5.2 The SIMS measurement allows for the production of
vidual conditions. For referee purposes, a sampling plan shall
controlled oxygen content in heavily-doped silicon crystals.
be agreed upon before conducting the test. See Practice E 122
5.3 This test method can be used for process control,
for suggested choices of sampling plans.
research and development, and materials acceptance purposes.
9. Specimen Requirements
6. Interferences
9.1 Sample specimens must be flat and smooth on the side
6.1 Oxygen from silicon oxide, carbon oxide, and water on
used for analysis.
the surface can interfere with the oxygen measurement.
9.2 Sample specimens must be cleaved or diced to fit within
6.2 Oxygen adsorbed from the SIMS instrument chamber to
the sample specimen holder.
the surface can interfere with the oxygen measurement.
6.3 There are no effects upon the oxygen ion yield from the
10. Calibration
20 3
dopants for dopant densities less than 1 3 10 atoms/cm .
10.1 The two calibration standards in each load must be
6.4 The SIMS oxygen instrumental background as mea-
lightly doped Czochralski silicon in which the oxygen con-
sured on the float zone silicon specimen should be as low as
centration is measured by infrared absorption spectroscopy
possible and stable before the analyses are begun.
(see Test Method F 1188), and the measured values of the two
6.5 The specimen surface must be flat in the specimen
standards bracket the expected values for the test specimen
holder windows so that the inclination of the specimen surface
(that is, one calibration standard is higher in oxygen and one is
with respect to the ion collection optics is constant from
lower, compared to the expected value in the test specimen).
specimen to specimen. Otherwise, the accuracy and precision
10.2 The calibration standards must be measured by infra-
can be degraded.
red absorption to determine the concentration and homogeneity
6.6 The accuracy and precision of the measurement signifi-
of the oxygen within the standards; each standard is assigned
cantly degrade as the roughness of the specimen surface
the averaged infrared absorption oxygen value for the sub-
increases. This degradation can be avoided by using chemical-
strate.
mechanical polished surfaces.
10.3 Calibration standards that are included in the SIMS
6.7 Variability of oxygen in the calibration standards can
analyses must be taken from that portion of the wafer that
limit the measurement precision.
provided a homogeneous measurement in the Fourier trans-
6.8 Bias in the assigned oxygen of the calibration standards
form infrared spectrophotometer, (FT-IR) analysis; this portion
can introduce bias into the SIMS measured oxygen.
is typically the central portion of the wafer.
10.4 Each calibration standard specimen must be the same
7. Apparatus
size and have the same polished surface as the test specimen.
7.1 SIMS Instrument, equipped with a cesium primary ion
10.5 The float zone specimens that are included in the SIMS
source, electron multiplier detector and Faraday cup detector,
analysis to measure the instrumental oxygen background must
and capable of measuring negative secondary ions.
be measured by infrared absorption to determine if the oxygen
concentration is low enough to measure the instrumental SIMS
background. Oxygen concentrations below 0.5 ppma (see Test
Goldstein, M., and Makovsky, J., “The Calibration and Reproducibility of
Method F 1188) in the float zone specimen are normally
Oxygen Concentration in Silicon Measurements Using SIMS Characterization
sufficient.
Techniques,” Semiconductor Fabrication: Technology and Metrology, ASTM STP
10.6 Each float zone specimen must be the same size and
990, Dinesh C. Gupta, Ed., ASTM, 1988, pp. 350–360.
Makovsky, J., Goldstein, M., and Chu, P., “Progress in the8 Load Line
have the same polished surface as the test specim
...
Questions, Comments and Discussion
Ask us and Technical Secretary will try to provide an answer. You can facilitate discussion about the standard in here.