ASTM F1366-92(1997)e1

Standard Test Method for Measuring Oxygen Concentration in Heavily Doped Silicon Substrates by Secondary Ion Mass Spectrometry

SCOPE
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 10 20  atoms/ cm ) for boron, antimony, arsenic, and phosphorus. This test method is especially applicable for silicon that has resistivity between 0.0012 and 1.0 [omega]-cm for -type silicon and between 0.008 and 0.2 [omega]-cm for -type silicon.
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 [omega]-cm for -type silicon and greater than 0.1 [omega]-cm for -type silicon (see Test Method F1188). The infrared absorption measurement can be extended to between 0.02 and 0.1 [omega]-cm for -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 problems, 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: Historical
• Publication Date: 31-Dec-1991
• Technical Committee: F01 - Electronics

Relations

• Replaced By: ASTM F1366-92(2002) - Standard Test Method for Measuring Oxygen Concentration in Heavily Doped Silicon Substrates by Secondary Ion Mass Spectrometry (Withdrawn 2003)
• Effective Date: 01-Jan-1992

Standards Content (Sample)

NOTICE: This standard has either been superseded and replaced by a new version or withdrawn. Contact
ASTM International (www.astm.org) for the latest information.
e1
Designation: F 1366 – 92 (l997)
AMERICAN SOCIETY FOR TESTING AND MATERIALS
100 Barr Harbor Dr., West Conshohocken, PA 19428
Reprinted from the Annual Book of ASTM Standards. Copyright ASTM
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.
e NOTE—Keywords were added editorially in April l998.
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
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
2.1 ASTM Standards:
throughout the holder. Three measurement passes are made
through the holder. The ratio of the measured oxygen and
− −
This test method is under the jurisdiction of ASTM Committee F-01 on silicon secondary ion intensities (O /Si ) is calculated for each
Electronics and is the direct responsibility of Subcommittee F01.06 on Silicon
specimen. The relative standard deviation (RSD) of the ratio is
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.
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
then calculated for each specimen. If any specimen other than 7.1.1 The SIMS instrument should be adequately prepared
the float zone specimen has a RSD of the ratio greater than (that is, baked) so as to provide the lowest possible instrumen-
3 %, more analyses are performed. The SIMS average O/Si tal background.
ratios are then converted to infrared-equivalent concentrations 7.2 Cryopane1, liquid nitrogen- or liquid helium-cooled,
,
5 6
by utilizing either the load-line calibration method or the which surrounds the test specimen holder in the analysis
load factor calibration method with the calibration specimens chamber.
in the load. 7.3 Test Specimen Holder.
7.4 Oven, for baking test specimen holder.
5. Significance and Use
8. Sampling
5.1 SIMS can measure the oxygen concentration in heavily-
doped silicon substrates used for epitaxial silicon where the 8.1 Since this procedure is destructive in nature, a sampling
procedure must be used to evaluate the characteristics of a
free carrier concentration obscures the infrared absorption and
group of silicon wafers. No general sampling procedure is
prevents the normal use of the infrared measurement as a
characterization technique for the commercial production of included as part of this test method, because the most suitable
sampling plan will vary considerably depending upon indi-
silicon.
5.2 The SIMS measurement allows for the production of vidual conditions. For referee purposes, a sampling plan shall
be agreed upon before conducting the test. See Practice E 122
controlled oxygen content in heavily-doped silicon crystals.
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
used for analysis.
6.1 Oxygen from silicon oxide, carbon oxide, and water on
9.2 Sample specimens must be cleaved or diced to fit within
the surface can interfere with the oxygen measurement.
the sample specimen holder.
6.2 Oxygen adsorbed from the SIMS instrument chamber to
the surface can interfere with the oxygen measurement.
10. Calibration
6.3 There are no effects upon the oxygen ion yield from the
20 3
10.1 The two calibration standards in each load must be
dopants for dopant densities less than 1 3 10 atoms/cm .
lightly doped Czochralski silicon in which the oxygen con-
6.4 The SIMS oxygen instrumental background as mea-
centration is measured by infrared absorption spectroscopy
sured on the float zone silicon specimen should be as low as
(see Test Method F 1188), and the measured values of the two
possible and stable before the analyses are begun.
standards bracket the expected values for the test specimen
6.5 The specimen surface must be flat in the specimen
(that is, one calibration standard is higher in oxygen and one is
holder windows so that the inclination of the specimen surface
lower, compared to the expected value in the test specimen).
with respect to the ion collection optics is constant from
10.2 The calibration standards must be measured by infra-
specimen to specimen. Otherwise, the accuracy and precision
red absorption to determine the concentration and homogeneity
can be degraded.
of the oxygen within the standards; each standard is assigned
6.6 The accuracy and precision of the measurement signifi-
the averaged infrared absorption oxygen value for the sub-
cantly degrade as the roughness of the specimen surface
strate.
increases. This degradation can be avoided by using chemical-
10.3 Calibration standards that are included in the SIMS
mechanical polished surfaces.
analyses must be taken from that portion of the wafer that
6.7 Variability of oxygen in the calibration standards can
provided a homogeneous measurement in the Fourier trans-
limit the measurement precision.
form infrared spectrophotometer, (FT-IR) analysis; this portion
6.8 Bias in the assigned oxygen of the calibration standards
is typically the central portion of the wafer.
can introduce bias into the SIMS measured oxygen.
10.4 Each calibration standard specimen must be the same
7. Apparatus
size and have the same polished surface as the test specimen.
10.5 The float zone specimens that are included in the SIMS
7.1 SIMS Instrument, equipped with a cesium primary ion
analysis to measure the instrumental oxygen background must
source, electron multiplier detector and Faraday cup detector,
be measured by infrared absorption to determine if the oxygen
and capable of measuring negative secondary ions.
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
...