ASTM F1389-00

Standard Test Methods for Photoluminescence Analysis of Single Crystal Silicon for III-V Impurities (Withdrawn 2003)

SCOPE
This standard was transferred to SEMI (www.semi.org) May 2003
1.1 These test methods cover the simultaneous determination of electrically active boron, phosphorus, arsenic, and aluminum content in low-dislocation mono-crystalline silicon.
1.2 These test methods can be used for samples that have majority dopant densities between approximately 1 X 1011 and 5 X 1015 atoms/cm3.
1.3 The concentrations obtained using these test methods are based on an empirically determined relationship of the logarithm of the concentration to the logarithm of specific luminescence line-intensity ratios.
1.4 The empirical relationship established assumes a constant sample excitation level for all measurements on a given instrument.
1.5 To accommodate differences in instrumentation, two methods are included in this proposal. "Test Method A" refers to procedures appropriate for dispersive infrared spectrophotometers operating under the high sample excitation conditions and "Test Method B" refers to procedures appropriate for Fourier transform instruments operating under low excitation conditions.
1.5.1 Typical calibration curves for each test method are provided. These curves are modified for each instrument using the analysis of standard samples as reference data. Once modified, the curves for a given instrument should produce sample dopant density values that agree with other similarly operated instruments using the same test method. Data obtained using Test Method A may not agree with data obtained using Test Method B, hence values must be reported with reference to the test method used.
1.6 Many laboratories use photoluminescence to analyze epitaxial layers. However this application encounters many variables and the underlying physics is not fully understood; hence these test methods do not attempt to outline standard practices regarding such analysis.
1.7 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• Status: Withdrawn
• Publication Date: 09-Jun-2000
• Withdrawal Date: 12-Aug-2003
• ICS: 29.045 - Semiconducting materials
• Technical Committee: F01 - Electronics

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 1389 – 00
Standard Test Methods for
Photoluminescence Analysis of Single Crystal Silicon for
III-V Impurities
This standard is issued under the fixed designation F 1389; 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.
INTRODUCTION
Several different methods of photoluminescence analysis are currently in practice worldwide. The
following test methods address two of these, one in use primarily in Japan and the other primarily in
the United States. Recently published works (1, 2) describe other approaches that subcommittee
F01.06 may incorporate into future versions of these test methods.
1. Scope using Test Method B, hence values must be reported with
reference to the test method used.
1.1 These test methods cover the simultaneous determina-
1.6 Many laboratories use photoluminescence to analyze
tion of electrically active boron, phosphorus, arsenic, and
epitaxial layers. However this application encounters many
aluminum content in low-dislocation mono-crystalline silicon.
variables and the underlying physics is not fully understood;
These chemical species can also be determined by the proce-
hence these test methods do not attempt to outline standard
dure of Test Method F 1630.
practices regarding such analysis.
1.2 These test methods can be used for samples that have
1.7 This standard does not purport to address all of the
majority dopant densities between approximately 1 3 10 and
15 3
safety concerns, if any, associated with its use. It is the
5 3 10 atoms/cm .
responsibility of the user of this standard to establish appro-
1.3 The concentrations obtained using these test methods
priate safety and health practices and determine the applica-
are based on an empirically determined relationship of the
bility of regulatory limitations prior to use.
logarithm of the concentration to the logarithm of specific
luminescence line-intensity ratios.
2. Referenced Documents
1.4 The empirical relationship established assumes a con-
2.1 ASTM Standards:
stant sample excitation level for all measurements on a given
F 416 Test Method for Detection of Oxidation Induced
instrument.
Defects in Polished Silicon Wafers
1.5 To accommodate differences in instrumentation, two
F 723 Practice for Conversion Between Resistivity and
methods are included in this proposal. “Test Method A” refers
Dopant Density for Boron-Doped and Phosphorus-Doped
to procedures appropriate for dispersive infrared spectropho-
Silicon
tometers operating under the high sample excitation conditions
F 1630 Test Method for Low Temperature FT-IR Analysis
and “Test Method B” refers to procedures appropriate for
of Single Crystal Silicon for III-V Impurities
Fourier transform instruments operating under low excitation
F 1723 Practice for Evaluation of Polycrystalline Silicon
conditions.
Rods by Float-Zone Crystal Growth and Spectroscopy
1.5.1 Typical calibration curves for each test method are
provided. These curves are modified for each instrument using
3. Terminology
the analysis of standard samples as reference data. Once
3.1 Definitions:
modified, the curves for a given instrument should produce
3.1.1 defect luminescence lines—those features arising from
sample dopant density values that agree with other similarly
defect structures in the silicon.
operated instruments using the same test method. Data ob-
3.1.2 electron hole droplet (EHD)—the condensed phase
tained using Test Method A may not agree with data obtained
(liquid) of the excitonic gas generated by photoexcitation. The
exciton population is dependent upon excitation intensity and
These test methods are under the jurisdiction of ASTM Committee F01 on can be raised to the point where the exciton density is sufficient
Electronics and are the direct responsibility of Subcommittee F01.06 on Silicon
to allow condensation of the exciton gas into a liquid like
Materials and Process Control.
Current edition approved June 10, 2000. Published August 2000 Originally
published as F 1389–92. Last previous edition F 1389–99.
2 3
The boldface numbers in parentheses refer to the list of references at the end of Discontinued l998; see l997 Annual Book of ASTM Standards, Vol 10.05.
this test method. Annual Book of ASTM Standards, Vol 10.05.
Copyright © ASTM, 100 Barr Harbor Drive, 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 1389
TABLE 2 Photoluminescence Line Locations (Vacuum
exciton state (3). The existence of EHD luminescence can be
Wavenumbers) Detailed Listing for Boron and Phosphorus
an indirect measurement of excitation power density on the
Phosphorus
sample.
Boron Features, Features,
3.1.2.1 Discussion—EHD onset—the point in the sample
−1 −1
cm cm
excitation intensity curve where the electron-hole-droplet be-
gins to form (4). The EHD luminescence includes a very broad
B (BE) = 9281.3 P (BE) = 9275.4
NP NP
feature underlying the TO region impurity lines which, with B (b ) = 9263.6 P (b ) = 9246.4
NP 1 NP 1
B (b ) = 9245.9 P (b ) = 9223.9
NP 2 NP 2
increasing excitation intensity, both intensifies and shifts to
P (b ) = 9208.4
NP 3
lower energies relative to the other silicon luminescence
P (b ) = 9197.8
NP 4
B (BE) = 9130.1 P (BE) = 9124.4
features. TA TA
A
B (b ) = 9112.4 P (BE- = 8992.8
TA 1 NP
3.1.3 excitons—the electron-hole pairs that give rise to the
2e)
luminescence of interest upon recombination at either a free
B (b ) = 9095.2
TA 2
B
B (BE) = 8812.6 P (b 8) = 8812.7
lattice site (free exciton) or an impurity atom site (bound TO TO 1
C
B (b ) = 8795.0 P (BE) = 8806.8
TO 1 TO
exciton).
B
B (b ) = 8777.5 P (b 8) = 8790.4
TO 2 TO 2
C
3.1.4 extrinsic line (X (BE) or X (BE))—the lumines-
TO NP B (b ) = 8763.2 P (b ) = 8778.0
TO 3 TO 1
B
B (b ) = 8752.1 P (b 8) = 8771.3
cence that arises from an exciton captured by an impurity site TO 4 TO 3
C
B (b ) = 8742.6 P (b ) = 8756.0
TO 5 TO 2
in the crystal lattice (a bound exciton). Its energy is lower than
B
P (b 8) = 8756.2
TO 4
B
the intrinsic emission by an amount related to the exciton
P (b 8) = 8745.4
TO 5
C
P (b ) = 8740.2
binding energy of the impurity at 4.2 K. TO 3
A
3.1.4.1 Discussion—“X” is the impurity element symbol The two-electron transition is represented by 2e (see Ref (3)).
B
Beta series transition.
and 88BE” indicates bound exciton luminescence line. Extrinsic
C
Alpha series transition.
luminescence also includes features attributed to bound multi-
exciton complexes ( b , b ,or b would indicate the first,
1 2 3
con requires a momentum conserving mechanism owing to the
second and third bound multi exciton complex lines, respec-
indirect band gap of the crystal. Phonons provide such a
tively). In donor luminescence, these complexes give rise to
mechanism. The principal phonon types of interest in silicon
two series of lines in the TO region, called the alpha and beta
luminescence are the transverse acoustic (TA), transverse
series. The weaker beta series features are denoted by an
optical (TO), and longitudinal optical (LO) phonons. These test
apostrophe after the line notation (that is, P (b8 )). See Table
TO 1
methods address the use of features associated with the TO
1 and Table 2 for line locations.
phonon as well as those not including phonon emission in their
3.1.5 intrinsic line (I (FE))—the luminescence that arises
TO
momentum-conserving processes. These latter features are
from the silicon itself, with no impurity species affecting the
designated “NP” or no-phonon features.
exciton recombination (5, 6).
4. Summary of Test Method
3.1.5.1 Discussion—“I” indicates intrinsic silicon emission,
TO indicates the transverse optical phonon associated with the
4.1 A sample of monocrystalline silicon is cooled to 4.2 K
transition, and FE refers to the free exciton recombination
and photoexcited with greater-than-bandgap energy light at one
responsible for the emission (see Table 1 for line locations).
of two intensities listed, depending upon the type of instrument
3.1.6 phonon—a quantum of lattice vibrational energy, as a
used. The resulting luminescence is collected and recorded.
photon is a quantum of electromagnetic energy.
Spectral features corresponding to intrinsic silicon and extrin-
3.1.6.1 Discussion—The recombination of excitons in sili-
sic impurity emissions are measured and related to calibration
curves to yield dopant density.
TABLE 1 Photoluminescence Line Locations (Vacuum
Wavenumbers)
5. Significance and Use
NOTE 1—Formula to convert vacuum wavenumbers to air wavenum- 5.1 Photoluminescence analysis identifies and quantifies the
bers:
electrically active dopant impurities in monocrystalline silicon.
(air wavenumber) = 1.00030025 3 (vacuum wavenumber)
These test methods address boron, phosphorus, arsenic, and
NOTE 2—Formula to convert wavenumbers to electronvolts:
aluminum, found as impurities in electronic grade silicon.
−4
(eV) = 1.23985 3 10 3 (wavenumber)
5.2 These test methods can be applied to doped and un-
Silicon Free Exciton (FE) Lines:
doped float-zoned or Czochralski material with dopant densi-
−1
I (FE) at 8848 cm
TO
11 15 3
−1
ties between approximately 1 3 10 and 5 3 10 atoms/cm .
I (FE) at 8860 cm
LO
−1
I (FE) at 9166 cm
TA 5.2.1 Electronic-grade polycrystalline silicon producers and
Major Shallow Impurity Bound Exciton (BE) Lines:
users require information regarding impurities for quality
assurance as well as for research and development purposes.
TO region, NP region, NP/TO region BE
Element
−1 −1 A
cm cm line intensity ratio
Polysilicon is float-zoned and a sample from the zoned rod is
analyzed following these test methods to obtain impurity
Boron 8812.6 9281.3 0.017
densities that can be related to the impurity content of the
(Antimony) (8810.5) (9280.0) (0.010)
starting material (see Practice F 1723).
Phosphorus 8806.8 9275.4 1.4
Aluminum 8803.4 9271.8 0.7
6. Interferences
Arsenic 8801.0 9269.4 2.0
A −1
Instrument resolution = 0.5 cm , sample = FZ silicon. 6.1 Variations in Excitation Intensity— The extrinsic BE
NOTICE: This standard has either been superceded and replaced by a new version or discontinued.
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F 1389
and intrinsic FE luminescence features do not vary at the same curacies in the work that produced the calibration curves
rate with excitation intensity (7). The FE features increase impact the accuracy of the PL results.
proportionally with excitation intensity, while the BE features
7. Apparatus
increase proportionally at low excitation levels but become
more slowly increasing at higher excitation levels generally 7.1 Cryostat, that maintains sample temperature at 4.2 K is
needed. Either open-cycle liquid helium immersion or ex-
above the EHD onset point. Since the calculated concentrations
are derived from the ratio of extrinsic features to the intrinsic change gas cryostats, or closed-cycle refrigeration systems
may be used. The bath immersion type cryostat is recom-
feature, the ratio will be decreasing as the excitation intensity
is increasing. Thus, if a sample is measured at a higher mended for higher confidence in the temperature stability of
the sample. In both the exchange gas and closed-cycle systems,
excitation level than the instrument is calibrated for, the
calculated concentration will be artificially low, and vice versa. careful attention must be paid to thermal sinking and accurate
sample temperature measurement; corrections for the effects of
6.2 Sample surface damage, bulk defects, or other lifetime
temperature variations have not been included in these test
reducers also affect the line ratios and overall luminescence
methods.
intensity owing to their tendency to reduce the steady state
7.2 Sample Holder, which does not cause excessive strain
population of excitons, thus mimicking the effects of a lower
on the ample through spring forces or other means, so as to
excitation intensity. Other mechanisms related to the presence
avoid line splitting associated with crystal stresses is required.
of these defects may also introduce decalibrating effects. Some
7.3 Laser Excitation Source, capable of generating electron
luminescence features are generated by defects; for example,
−1
hole pairs in the silicon crystal is needed. The argon-ion laser
those at 6510 and 7050 cm are typical of thermally stressed
operated at 514.5 nm is used. Laser light intensity must be
samples. Such features can provide qualitative information
controllable and stable for accurate measurements to result.
about the presence of defects (8, 9).
7.4 Infrared Spectrophotometer, equipped with a detector
6.3 The ratios and line widths of the silicon luminescence
−1
and optics suitable for use between 8750 and 9300 cm , and
features vary strongly with temperature, hence variations in
−1 −1
capable of at least 0.5 cm resolution at 9300 cm ,is
sample temperature must be avoided.
required.
6.4 Overlapping Spectral Features:
−1
6.4.1 The boron B (BE) feature at 8812.6 cm overlaps
TO
8. Hazards
−1
the P (b8 ) feature at 8812.7 cm causing a direct error
TO 1
8.1 Chemicals used in this procedure are potentially harmful
when calculating boron concentration. The beta-series P (
TO
and must be handled with the utmost care at all times. Refer to
b8 ) line is approximately one-tenth the intensity of the alpha
the Annex of Test Method F 416.
−1
series P (BE) line at 8806.6 cm , so a subtraction based on
TO
the amount of phosphorus present can be made in the boron
9. Sample Preparation
feature measurement. An alternative approach is to use the
9.1 Perform one of the following to remove all work
B (b ) boron line, which is free from a coincident phosphorus
TO 1
damage and surface contamination (as-received chemical-
line, provided the photoluminescence (PL) instrument has been
mechanically polished wafers should not need further prepa-
calibrated for this feature.
ration).
6.4.2 The antimony Sb (BE) line falls between boron and
TO
9.1.1 Etch sample using a suitable etchant (for example,
phosphorus TO features. Since the line widths are broad
CP-5 hydrofluoric-nitric-acetic acid etchant).
relative to the line positions of these features, the presence of
9.1.2 Polish the surface of the sample with a suitable
antimony affects the apparent intensities of boron and phos-
chemical-mechanical polishing compound.
phorus TO features. The no-phonon, (NP) fea
...