JSNM
Standard of Japan Society of Newer Metals

JSNM-SI-002

Test method for determination of low carbon impurity
concentration in single crystal silicon byphotoluminescence spectroscopy
Established in March 2021

Prepared by
Silicon PL Standardization Working Group
Silicon Standardization Promotion CommitteeStandardization Committee
Published by
Japan Society of Newer Metals

JSNM-SI-002

Contents
Main body
1. Scope ------------------------------------------------------------------------------------------------------- 1
2. Definition of terms --------------------------------------------------------------------------------------- 1
3. Samples ---------------------------------------------------------------------------------------------------- 2
3.1 Silicon crystal------------------------------------------------------------------------------------------ 2
3.2 Luminescence activation ----------------------------------------------------------------------------- 3
4. Measuring equipment ------------------------------------------------------------------------------------ 3
5. Measuring method --------------------------------------------------------------------------------------- 4
5.1 Overview of measurement method ---------------------------------------------------------------- 4
5.2 Measurement environment ------------------------------------------------------------------------- 4
5.3 Excitation light intensity ---------------------------------------------------------------------------- 4
5.4 Wavelength resolution ------------------------------------------------------------------------------ 5
5.5 Wavelength range ------------------------------------------------------------------------------------ 5
6. Data analysis ---------------------------------------------------------------------------------------------- 5
6.1 Identification of spectral line--------------------------------------------------------------------- 5

6.2 Measurement of peak intensity -------------------------------------------------------------------- 5
6.3 Concentration calculation -------------------------------------------------------------------------- 6
6.4 Detection limit --------------------------------------------------------------------------------------- 6
7. Calibration ------------------------------------------------------------------------------------------------ 7
8. Accuracy and reliability --------------------------------------------------------------------------------- 8
8.1 Error in intensity ratio ------------------------------------------------------------------------------ 8
8.2 Accuracy ---------------------------------------------------------------------------------------------- 8
8.3 Reproducibility -------------------------------------------------------------------------------------- 9Commentary
I. Purpose of enactment ............................................................................................................C1
II. Background of enactment .....................................................................................................C1
III. Principle ...............................................................................................................................C1
IV. Explanation of standard items ..............................................................................................C2
V. Standard samples ...................................................................................................................C6
VI. References ...........................................................................................................................C7
List of committee member for JSNM-SI-001-02(i)

JSNM-SI-002

This document is a translation of JSNM standard in Japanese.
In the event of any doubt arising, the original standard in Japanese is to be evidenced.

(ii)

JSNM-SI-002

JSNM standard

JSNM-SI-002
Test method for determination of low carbon impurity concentrationin single crystal silicon by photoluminescence spectroscopy
1. Scope
This standard specifies a method for measuring the carbon impurity concentration in single crystal silicon byphotoluminescence. The materials to which this standard is applicable should have an interstitial oxygen
concentration of approximately 1×1017 to 2×1017 atoms/cm3, a resistivity of approximately 50 Ωcm or more forn-type materials and 1k Ωcm or more for p-type materials. The measurable range is 1×1014 to 3×1015
atoms/cm3 (2 to 60 ppba).
Remark 1: The following are the reference standards for this standard.
JIS H 0615 Test method for determination of impurity concentrations in silicon crystal byphotoluminescence spectroscopy.
SEMI MF1389-0704 Test methods for photoluminescence analysis of single crystal silicon for III-V
impurities
JIS K 8541 Nitric acid (reagent)
JIS K 8819 Fluoric acid (reagent)
JEITA EM-3503 Standard test method for substitutional atomic carbon content of silicon by
infrared absorption
SEMI MF1391-1107 Test method for substitutional atomic carbon content of silicon by infraredabsorption
SEMI MF1188-1107 Test method for interstitial oxygen content of silicon by infrared absorption
with short baseline
Remark 2: The interstitial oxygen concentration is obtained by the infrared absorption method according to
the SEMI MF1188-1107, with a conversion coefficient of 3.14×1017 atoms/cm2 (IOC-88).
2. Definition of terms
The main terms used in this standard are defined as follows.
(1) Photoluminescence (PL): Light emitted from a material as a result of their luminescent recombination
when excess electrons and holes are generated in the material by light irradiation.
Remark: The analysis of photoluminescence of a semiconductor crystal allow us to evaluate the band
structure of the crystal and impurities and defects in the crystal.

1

JSNM-SI-002(2) Exciton: A state in which a free electron and a free hole in a semiconductor crystal are coupled by coulomb
force.
Remark: There are two types of excitons: free exciton (FE), which moves around freely in the crystal, andbound exciton (BE), which is trapped by the electronic levels created by impurities or defects. Under
strong excitation conditions, a bound multiple exciton complex (BMEC) in which multiple excitons
are trapped by the electronic level is generated. BMEC with (n + 1) bound excitons is written as“bn”.
(3) Phonon: The energy quantum of the lattice vibration in the crystal.
Remark: Since silicon is an indirect-transition-type semiconductor, emission lines with phonon emissions for
momentum conservation are observed during the emission process, and are called phonon sidebands.
Types of phonons include, transverse acoustic (TA) phonons, longitudinal acoustic (LA) phonons,
transverse optical (TO) phonons, longitudinal optical (LO) phonons. In emission processes involving
impurities or defects, the selection rule is relaxed by the interaction with impurities or defects, andemission line without phonons (no phonon; NP) can also be observed.
(4) Luminescence activation: When impurities contained in the crystal do not act as luminescentrecombination centers and, as a result, cannot be detected by photoluminescence, light emission centerscomposed of the same impurities can be formed by irradiating high energy particles. The luminescence
activation is the process of forming the light emission centers so that they can be detected byphotoluminescence.
(5) G-line: Luminescent line originated from the complex of interstitial and substitution carbon atoms(G-center) formed when silicon crystal is irradiated with high energy particles such as electrons. It shows asharp peak at 0.969 eV.
Remark 1: Since this defect is generated from carbon impurities in the crystal, G-line intensity is used as anindex of carbon impurity concentration.
Remark 2: When silicon is irradiated with high energy particles such as electrons, interstitial oxygen andinterstitial carbon complex (C-center) is also generated and has a sharp peak at 0.789 eV, called
C-line. The C-line intensity is also correlated with the carbon concentration, but it is strongly
affected by the oxygen concentration because it contains oxygen impurities as a component.
3.

Samples

3.1 Silicon crystal
Samples should be treated basically to fulfil the JIS H 0615 requirement.
(1) In the case of a polished wafer for semiconductor device fabrication, a pellet of about 5×10 mm is cut out
from the wafer and used as a sample. After the activation by electron beam irradiation, PL measurement isperformed as it is.
(2) If the material to be measured is not a polished wafer, a pellet of about 5×5 mm or more and a thickness ofabout 1 mm is cut out and used as a sample. The sample should be rinsed with pure water and etched to get

2

JSNM-SI-002
mirror-like surface. For etchant, nitric acid (HNO3) specified in JIS K 8541 and hydrofluoric acid (HF)
specified in JIS K 8819 are mixed in volume ratio HNO3 : HF = 5 : 3. The samples are dipped for 1 to 2
minutes. After rinsing with pure water, drying, and activation of carbon impurities by electron beam irradiation,
PL measurement is performed on the samples.
3.2 Luminescence activation
The pellet is irradiated with 1 MeV electrons with a fluence of 1×1015 electrons/cm2 at room temperature inorder to form G-center which is luminescent center including carbon impurities as compositional elements.
During this process, the sample should be cooled so that the temperature does not exceed 100 ° C.
4. Measuring equipment
The equipment consists of a laser light source, a cryostat, an optical system, and a spectrometer with thesame performance as specified in JIS H 0615. Each of these devices has the following specification.
(1) Laser light source
A continuous-wave laser should be used which has an oscillation wavelength in the range of 450-650 nm andan output with 50 mW or more on the sample surface.
(2) Cryostat
In order to perform PL measurement at the temperature of 4.2 K, liquid-helium-immersion-type cryostat
should be used. The cryostat has a window (windows) through which the sample is irradiated with the laser
light and the PL light is extracted from the sample. When the sample is mounted on the sample holder in thecryostat, the sample should not be excessively stressed: For example, one end of the sample is pressed gently
with a phosphor bronze spring.
(3) Optical system
The system should consist of an infrared cut filter that removes infrared light contained in the laser lightsource, optical path changing flat mirrors, condensing lens or mirrors that guide PL light to the spectrometer,
and long-pass filter to brock laser light and higher-order light from diffraction grating. The condensing lens or
mirrors should be optically aligned with the spectrometer and photodetector so that PL light can reach thephotodetector with as low loss as possible.
(4) Spectrometer
The applicable spectrometer is as follows.
(a) The spectrometer consists of a dispersive monochromator, a photodetector, and a signal processing system.
The measurement wavelength ranges are from 1270 nm (0.976 eV) to 1290 nm (0.961 eV) for G-line
measurement and from 1076 nm (1.152 eV) to 1142 nm (1.086 eV) for near-band-edge emission measurement
specified in JIS H 0615. The wavelength resolution of 0.25 nm is required in these regions.
Note:

The spectral position shall be indicated by the wavelength λ (nm) and the photon energy E (eV), andboth are expressed by the following formula.
E = 1240 / λ

3JSNM-SI-002(b) The recommended dispersive spectroscope has a focal length of about 0.3 to 1 m and a 600 grooves/mm
grating blazed at 1000 to 1200 nm.
(c) For the photodetector, a photomultiplier tube should be used which has high sensitivity in near infrared
region in the case of a wavelength-scanning type spectrometer. In the case of a multichannel spectrometer, acooled InGaAs diode array is recommendable.
(d) For the signal processing system, the phase-locked detection (lock-in) method is suitable for weak light
amplification in the case of a wavelength-scanning type spectrometer. Laser beam is passed through an opticalchopper with a duty cycle of 50% and irradiated on the sample. Signal from photodetector is amplified by alock-in amplifier and the optical output signal for each wavelength is recorded on the recorder or is plotted out
by computer. If a multichannel spectrometer is used, output of the signal processor which is built in thephotodetector should be directly linked with a personal computer.
Remark: Fourier transform spectrometer can be used as a spectrometer. In this case, the equipment
parameters are not specified in this standard.
5.

Measurement method

5.1 Overview of measurement method
The sample is mounted on the sample holder and immersed in liquid helium in the cryostat. Under themeasurement environment of 5.2, the sample is irradiated with the laser beam of the intensity shown in 5.3. PLlight from the sample is measured over a wavelength range of 5.5 with a wavelength resolution of 5.4.
5.2 Measurement environment
The measuring system should be installed in a dark room with low electromagnetic noise. The environmental
temperature should be from 15 to 25 °C, the fluctuation during measurement should be within ± 1 °C, and therelative humidity should be 60 % or less.
5.3 Excitation light intensity
The excitation laser beam has an intensity of 50 mW on the sample surface and a beam diameter of 2.5 mm.

Fig. 1: PL spectrum of near-band-edge emission at 4.2K.

4

JSNM-SI-002
Remark: The sample is a p-type, high resistivity silicon crystal (carbon concentration: 6.3×1015 atoms /cm3,
oxygen concentration: 1.6×1017 atoms/cm3). The baseline drawing is shown (dashed line a b).

Fig. 2: PL spectrum of G-line at 4.2K.
Remark: The sample is a p-type, high resistivity silicon crystal (carbon concentration: 6.3×1015 atoms/cm3,
oxygen concentration: 1.6×1017 atoms/cm3). The baseline drawing is shown (dashed line a b).
5.4 Wavelength resolution
The wavelength resolution is 0.25 nm in the wavelength region of ITO (FE) line and G-line.
5.5 Wavelength range
The wavelength range is as follows.
TO phonon sideband of band-edge emission (ITO): 1140-1120 nm (1.088-1.107 eV)
G-line: 1270-1290 nm (0.976-0.961 eV)
6.

Data analysis

6.1 Identification of spectral line
Figures 1 and 2 show examples of the PL spectra of the near-band-edge emission and the G-line, respectively,
measured according to 5. The origin of the spectral components in the near-band-edge emission is identified
from their positions.
Remark: The emission lines in the spectrum are denoted by XTO (BE). The first symbol X indicates the typeof impurity (B: boron, P: phosphorus, Al: aluminum, and As: arsenic). The subscript indicates thetype of phonon involved. The type of exciton is shown in parentheses. The symbol I indicates theintrinsic emission of silicon.
6.2 Measurement of peak intensity
Baselines are necessary to measure the peak intensities of ITO(FE) line and G-line. The method of baseline
drawing for the ITO (FE) line conforms to JIS H 0615 standard: The baseline is the straight-line a b connecting
the spectral point a at 1126 nm (1.101 eV) and valley b between ITO (FE) line and BLO (BE) line, as shown in
Fig. 1. The baseline for the G-line is a straight line over the range of  5 nm on both sides of the line, as shown

5

JSNM-SI-002
in Fig. 2. The peak intensities of the ITO(FE) and G-line measured by using the baselines described above arerepresented by ITO(FE) and G. The intensity ratio of the G-line with respect to the ITO (FE) line, G / ITO, is used
as an index of the carbon impurity concentration.
6.3 Concentration calculation
The carbon impurity concentration is calculated using the relationship between the G-line intensity ratio G/
ITO and the carbon impurity concentration as the calibration curve (Fig. 3).
Remark 1: Relationship in Fig. 3 was obtained from the round-robin test of the PL measurement following
the method of 5 by 7 organizations (#1 to #7) after luminescence activation by the method describedin 3.2. The round-robin test was performed on the 4 samples (E8, E9, EA, EB) with n-typeconductivity and a resistivity of approximately 50 Ωcm or more, and 3 samples (G1, G3, G5) with
p-type conductivity and a resistivity of approximately 1 kΩcm or more, as shown in Table 1.
Intensity ratio G/ ITO was calculated by the method described in 6.2, normalized by the intensity ratioof G1 whose carbon concentration was median value, and plotted against carbon concentration
measured by SIMS. (For detail, referred to Commentary 6.3.)
Remark 2: The approximation formula of the calibration curve shown in Fig. 3 is as follows.
G /ITO = 2.52010-30 NC2-32

G /ITO = -1.45710

 NC2 + 2.82510-15 NC - 7.738410-1(G /ITO≦1)(1),(G /ITO＞1)(2),

where NC is the carbon impurity concentration in atoms/cm3.
6.4 Detection limit
The detection limit is determined by the noise level in the near-band-edge emission region and G-line region
in calculating the intensity ratio G/ ITO (the carbon concentration index). For the silicon single crystals to which
this standard is applied, the noise level in the G-line emission region is dominant and governs the detection
limit. If the detection limit is defined as the concentration corresponding to the G-line intensity twice as high as
the noise level around the G-line, the limit is determined to be 8×1013 atoms/cm3 from the calibration curve in
Fig. 3.
Remark: The detection limit has been verified to be reduced to about 4×1013 atoms/cm3 with increasing the
integration time of the detector from about 60 seconds in the round robin test to 1 hour. (Y. Satake,
M. Tajima, S. Asahara, and A. Ogura: “Detection limit of carbon concentration measurement in Si
for photoluminescence method after electron irradiation,” Jpn. J. Appl. Phys. 59, 126501 (2020).)

6JSNM-SI-002

Fig. 3: Calibration curve for carbon impurities in silicon crystals.
Remark: The PL intensity ratio G/ ITO is plotted against the carbon impurity concentration obtained by SIMS.
The regions of G/ ITO ≤ 1 and G / ITO> 1 are approximated by the quadratic exponentiation formula(1) and quadratic polynomial formula (2), respectively.
7.

Calibration
Although the conditions for the PL measurement are specified in 5, the conditions cannot be exactly the same

due to the difference in measuring instruments. Therefore, the calibration curve has to be corrected according to
the measurement conditions of each measuring equipment using standard samples whose carbon concentration
has been determined by other method like infrared absorption spectroscopy (JEITA EM-3503, SEMI
MF1391-1107) or secondary ion mass spectrometry (SIMS). The following is the correction method of thecalibration curve using standard samples, where it is recommendable to use the samples with the carbon
concentration of 4 levels or higher.
(1) Measure the PL spectrum of each standard sample according to the measurement conditions in 5.
(2) Calculate the intensity ratio according to the method specified in 6.
(3) Plot the intensity ratio of the standard sample on the calibration curve (Fig. 3).
7

JSNM-SI-002(4) Shift the calibration curve on the both logarithmic axes vertically so that the difference from the intensity
ratios of the standard samples becomes the smallest.
(5) Corresponding to the vertical shift in (4), the coefficients in formula (1) and (2) are changed.
Remark: Minimizing the difference from the measured intensity ratios by shifting the calibration curve in thevertical direction in (4) is equivalent to minimizing the difference from the calibration curve by
multiplying the measured intensity ratios by a coefficient. If the intensity ratio multiplied by thiscoefficient is used, there is no need to change the coefficients in formula (1) and (2).
Table 1: Characteristics of silicon samples used in round-robin test
Sample No.

E8

Conductivity type

E9

EA

(cm)
Oxygen conc.
(×1017 atoms/cm3)(×1014 atoms/cm3)

G1n-typeResistivity

Carbon conc.

EB

1.4

2.4

G3

G5

p-type

50-70

5300

5200

1410

1-2

1.6

1.5

2.1

6.3

11

36

4.3

6.9

Remark: These silicon single crystal samples were grown by the magnetic-field-applied Czochralski method.
8.

Accuracy and reliability
The accuracy and reliability of the measurement method specified in this standard are determined based on

the results of round-robin tests conducted by 7 organizations on samples with the carbon concentration of 7
levels shown in Table 1.
8.1 Error in intensity ratio
The error in obtaining the intensity ratio G / ITO, which is an index of carbon concentration, is determined by
the noise level on the baseline with respect to the G-line intensity for samples with characteristics within theapplicable range covered by this standard. The noise level is defined as one-half of the difference between the
maximum and minimum background levels in the range of 5 nm close to the G-line. The error of the intensity
ratio G/ ITO is obtained by dividing the noise level by the G-line intensity.
Figure 4 summarizes the results for the 7 samples: within 20 % or less for the sample with the lowest carbon
concentration (1.4×1014 atoms/cm3) and within 5 % or less for the samples with the carbon concentration of
6×1014 atoms/cm3 or more.
8.2 Accuracy
The errors which are the differences of the concentrations determined by each organization using thecalibration curve for the 7 standard samples in Table 1 from the C concentrations determined by SIMS are
shown in Fig. 5. The error tends to increase as the carbon concentration decreases. The error of the carbon
concentration value in all samples is within 30 % or less, as in JIS H 0615 standard for dopant impurity
8

JSNM-SI-002

quantification. Note that the data for sample G5 is excluded in Fig. 5, since its oxygen concentration of
2.1×1017 atoms/cm3 exceeds slightly the upper limit of 2×1017 atoms/cm3 in this standard. The oxygen
concentration outside the range causes an error.
8.3 Reproducibility
Reproducibility of the G-line intensity ratio G / ITO was tested by five organizations for sample G1 withapproximately median carbon concentration in Table 1. The measurement was repeated three times
inconsecutively with optical alignment of sample and spectrometer in each time. Figure 4 shows the deviationof the G-line intensity ratio from the 3 times average for 5 organizations. This indicates that the measurement
error in reproducibility of the intensity ratio is within 10 % or less.

20

Error (%)

15

10

5

0
E8
#1

E9

EA
#2

EB
G1
Sample
#3

G3

#4

G5

#5

Fig. 4: Error in intensity ratio G / ITO
Remark: The figure shows the error induced by noise on the baseline near the G-line when organizations #1 #5 determined the intensity ratio G / ITO of each sample.

9

JSNM-SI-002

30

Error (%)

20
10
0
‐10
‐20
‐30
E8

E9
#1

#2

EA

G1
EB
Sample#3 #4 #5 #6

G3

G5

#7

Fig. 5: Error in carbon concentration obtained from calibration curve
Remark: The figure shows the differences of the concentrations determined by organization #1-#7 using thecalibration curve for the 7 standard samples from those determined by SIMS. Sample G5 was
excluded, because its oxygen concentration exceeded the upper limit of this standard and error
became large.

15

Deviation (%)

10
5
0
‐5

‐10
‐15
#1

#2
1st

#3
#4
Organization
2nd
3rd

#5

Fig. 6: Reproducibility of intensity ratio G / ITO in 3 times repeated measurement by 5 organizations
Remark: Deviations from the average of three times measurements (1st, 2nd, 3rd) of intensity ratio G/ ITO for
sample G1 by organizations #1 - #5.
10

JSNM-SI-002

210806 JSNM-SI-002_PL_Com_MTb

JSNM-SI-002
Test method for determination of low carbon impurity concentrationin single crystal silicon by photoluminescence spectroscopy
CommentaryThis commentary is an explanation of the main body and related matters, and is not the part of this standard.
I. Purpose of establishment
Silicon power devices are important for realization of low carbon society. Because remaining carbon
impurities in single crystal silicon with the low concentration even less than 5×1014 atoms/cm3 affect device
characteristics of the state-of-the-art silicon power device like IGBT (Insulated Gate Bipolar Transistor),
precise control of the carbon impurities in silicon is needed. Under these circumstances, the standard of themeasurement method of low carbon concentration in silicon, which is interface between crystal makers anddevice makers, is eagerly sought. The Fourier transform infrared spectroscopy (FT-IR) method has beenstandardized and is widely used for the measurement of the carbon concentration in silicon. However, thesensitivity is not high enough for the current requirement, because the detection limit of the FT-IR method isapproximately 2×1015 atoms/cm3. Based on this situation, this standard specifies a method for measuring thecarbon concentration with the range of the order of 1014 atoms/cm3 in a silicon single crystal byphotoluminescence (PL).
II. Background of establishment
The activity of standardization of the PL method began at January in 2017 as the 1st preparatory meeting for
the PL method under Material Standards Study Group for Semiconductor Supply-Chain (M4S) in Japan Societyof Newer Metals (JSNM). This preparatory meeting continued till the 5th meeting in March 2018. This activity
continued as one of entrusted projects of Ministry of Economy, Trade and Industry, “Acquisition and Promotionof International Standards for Energy Saving in 2018”. The 1st meeting of National Working Group of the PL
method (PL-NWG) was held in June 2018 and continued till the 15th meeting in February 2018. Based on theseresults, the new JSNM standard of PL method was standardized by Standardization Committee in February
2021, through discussion and deliberation in Silicon Standardization Promotion Committee andPhotoluminescence Standardization Working Group.
III. Principle
Carbon is introduced in silicon crystal as a contaminant during crystal growth or as an impurity in starting
poly crystalline silicon. The carbon atom occupies the lattice site (Cs) in an as-grown crystal and is electricallyinactive. In the case that high energy particles like electrons are irradiated on silicon crystals, Si atoms at theC1

JSNM-SI-002
lattice site are displaced to the interstitial sites and interstitial Si (Sii) atoms are formed. Sii displaces Cs to theinterstitial site and interstitial carbon (Ci) is formed. Ci is not stable and is trapped by interstitial oxygen (Oi) or
Cs, forming complex like Ci-Oi or Ci-Cs, which generates the electronic level called C-center or G-center,
respectively. Luminescence lines from the radiative transition through these levels are termed C-line, G-line
respectively1). Based on the fact that these complexes contain carbon, principle of this method is to estimate thecarbon concentration from the intensity of these luminescence lines2-6).
When the impurity concentration is estimated from the PL intensity, it is necessary to reduce the effects ofother radiative and non-radiative transitions than the radiative transition of the target impurity, because theemission occurs as a result of the competition of all the recombination processes. In the case of the PL method
for the determination of the donor and acceptor impurity concentrations in silicon crystals standardized by JIS
and SEMI, the intensity ratio between the bound exciton and free exciton lines is used to remove these effects,
because the differences in the defects and the surface condition are reflected in the free exciton intensity7). The
intensity ratio between C-line and the free exciton line and that between G-line and the free exciton line arealso effective for the carbon quantification, however, this procedure is not enough. Major luminescence is only
impurity-bound exciton and free exciton in the case of the donor and acceptor impurity quantification, while
C-line and G-line are added to the luminescence process in the case of the carbon impurity quantification.
Moreover, C-line and G-line are strongly affected by the oxygen concentration3,5), because oxygen participatesin the formation of the C-center and G-center. Therefore, the concentrations of donor, acceptor and oxygen
impurities are restricted in a certain range in this method. In practice, scope of this standard limits theapplicable materials to single crystals having the interstitial oxygen concentration of about 1×1017 to 2×1017
atoms/cm3, the resistivity of about 50 Ωcm or more for n-type conductivity and that of about 1 kΩcm or more
for p-type conductivity.
IV. Explanation of standard items
Main items of the main body of this standard are explained in detail.
3. Samples
3.1 Silicon crystal
Sample preparation basically follows JIS H 0615, and the same care is necessary. Moreover, samples should
not be placed in thermal ambient higher than 100 ℃ before the PL measurement, because G-line disappears
by thermal treatment higher than 250 ℃ and defects introduced by the irradiation are not stable in thermal
treatment between 150 ℃ and 450 ℃. It should be noted that G-line is not affected by high-intensity laser
illumination during PL measurement.
3.2 Luminescence activation
Electron irradiation for luminescence activation of carbon in silicon crystals can be done at several outsourcing
facilities like public facilities such as Japan Atomic Energy Agency and commercial establishments where
electron irradiation is performed for sterilization or material reforming. The electron irradiation condition in thisstandard, “acceleration energy of 1 MeV and fluence of 1×1015 electrons/cm2”, is determined by referring theC2

JSNM-SI-002
conditions written in technical papers1,3-6) already published and by considering convenience of the irradiation. In
the process for the determination of the calibration curve, a sample set with the irradiation condition of 2 MeV
acceleration energy and fluence of 1×1015 electrons/cm2 was also prepared, and the PL measurement was
performed on the samples by 2 organizations. An index of the carbon impurity concentration, G/ITO, is supposed
to increase in 2 MeV electron irradiation from the fact that the amount of radiation-induced defects is larger in 2
MeV than in 1 MeV, from the previous experimental results. However, the effect was within the experimental
error and did not exceed “the error in the intensity ratio of G/ITO is within 20 % or less”, shown in 8.1 in the main
body. From the results mentioned above, the calibration curve can be determined by the method shown in 7 under
the different irradiation condition, if the difference in the condition is not large.
Because electrons with energy of both 1 MeV and 2 MeV can penetrate silicon crystal with thickness less than
2 mm, there is no difference between the results of PL measurement from the irradiation side and those from theback side.
4. Measuring equipment(1) Laser light source
DPSS (Diode Pumped Solid State) laser widely used in scientific experiment with wavelength of 532 nm is
recommendable as the light source.
(2) Cryostat
Although the measurement at 4.2 K with a sample being immersed in liquid He is defined in this standard byreference to JIS H 0615, the measurement temperature can be raised up to liquid nitrogen temperature describedin 6.3 in this commentary. In that case, immersion-type and conductive-type cryostats using liquid nitrogen as acoolant and a conductive-type He gas closed cycle cryostat can be used. However, they were not included in thisstandard, because the accuracy of the quantification at higher temperatures was not verified.
(4) Spectrometer
Recently multichannel spectrometer using an InGaAs diode array with high sensitivity and high measurement
speed is used generally. Because PL intensity from indirect-bandgap silicon crystals is not strong, a high sensitive
InGaAs diode array is suitable for the detector. It should be noted that the correction of the spectral response of
the spectrometer is not defined. The error caused by the difference in the spectral response can be corrected by themethod described in 7 in the main body as written in 6.3 in this commentary.
5. Measuring method
5.3 Excitation light intensity
In JIS H 0615, the excitation light intensity on a sample surface is defined as 50 mW with a beam diameter of
2.5 mm, where the incident light is chopped with a duty ratio of 50 %. The intensity equivalent to JIS H 0615 is
100 mW for a multichannel spectrometer using continuous light excitation in this standard. However, theexcitation light intensity is defined as 50 mW in this standard because of the following reasons: (1) The differencein the excitation light intensity can be corrected by the correction of the calibration curve by the measurement of

C3

JSNM-SI-002
standard samples described in 6.3 in this commentary and in commentary IV 5.3 in JIS H 0615, and (2) error in
ITO(FE) line intensity increases in the 100 mW excitation, since electron-hole-droplet emission becomesdominant.
In the round-robin test, some organizations could not change beam diameter from tens of micrometers and theintensity per unit area increased by hundreds of times over this standard. Nonetheless, there was no large
difference in the correlation between the intensity ratio and the carbon concentration shown in Fig. 1 (a).
5.4 Wavelength resolution
For measurement of G-line, high wavelength resolution less than 0.02 nm is needed to measure the precise
spectral shape, because G-line used in this standard is very sharp with a half width of about 0.06 nm. In such acase, a spectrometer with a high wavelength dispersion is needed and the measurement becomes difficult becauseof the reduction of the signal intensity. Therefore, the wavelength resolution in this standard is defined as 0.25 nm
of almost the same value as JIS H 0615 so that the measurement can be performed at general organizations. For
this reason, a slight variation of the wavelength resolution affects the intensity of G-line. This can be corrected by
the method in 7 in the body, as described in 6.3 in this commentary. In any case, however, all measurements
should be performed under the same wavelength resolution.
6. Data analysis
6.3 Concentration calculation
The process of creating the calibration curve in Fig. 3 is explained as follows8). After luminescence activationfor 42 silicon crystals made by 7 organizations, preliminary measurements were performed by 2 organizations,and 21 samples for round-robin test were selected based on the carbon concentrations reported from eachorganization. Ten organizations joined round-robin test of the PL measurement. Three of them measured at thetemperatures of 15 K and 77 K. As shown in Table 1, 7 samples with almost the same oxygen concentrations,which were grown by the magnetic-field-applied Czochralski (MCZ) method, were selected and their carbon
concentrations were measured by SIMS. Four samples (E8, E9, EA, EB) in the 7 samples were of n-typeconductivity with the resistivity of 50 Ωcm and 3 samples (G1, G3, G5) were of p-type conductivity with theresistivity of more than 1 kΩcm.
From the measurement results of the 7 samples, the intensity ratio G/ITO was calculated by the method shownin 6.2 and plotted on a double logarithmic graph against the carbon concentration measured by SIMS, as shown in
Fig. C1 (a). Although the variations of G/ITO of respective samples among organizations are not small, therelations between G/ITO and the carbon concentration for all the samples show a positive correlation for all theorganizations and the shapes of all the correlation curves are quite similar. In order to clarify the similarity, theintensity ratio G/ITO were normalized by the ratio for sample G1, whose carbon concentration is approximately
the median of the 7 samples, and this normalized intensity ratio [G/ITO]N were plotted on a double logarithmic
graph against the carbon concentration measured by SIMS, as shown in Fig. C1 (b). In Fig. C1 (b), it is shownthat all the data points are located very near one correlation curve, and that this correlation can be used as thecalibration curve. Although the deviation of the data points at 15 K and 77 K were large before the normalization,

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these points got closer to the correlation curve after the normalization. However, only 4.2 K data was used in thisstandard, because the deviation of 4.2 K data was smaller than that of 15 K and 77 K data, resulting in the highprecision for the measurement at 4.2 K.
The cause of the above-mentioned variation in the intensity ratio G/ITO among the organizations is that themeasurement conditions were not always the same. The differences of the measurement conditions are as follows.
(1) Because the spectral response of optical measurement systems such as spectrometers and photodetectors
differs depending on the respective apparatuses, there is a difference in the intensity ratio between ITO(FE) line
and G-line with different wavelength positions. (2) As described in IV 5.4 in this commentary, the intensity
decrease of G-line occurs by slightly lowering the wavelength resolution because of its sharp line shape, while
the intensity decrease of ITO(FE) line does not occur because of its broad line shape. (3) Excitation-intensity
dependences of ITO(FE) line and G-line are not the same. These variations of the intensity ratio do not occur inmeasurements in one organization, where the spectral response of optical measurement systems, the wavelength
resolution and the excitation light intensity are fixed. In this standard, not intensity but intensity ratio is used as anindex of the concentration. Furthermore, the ratio is normalized by the ratio for G1 sample, as expressed by[G/ITO]N. These procedures remove the variations in the intensity ratio caused by the differences of themeasurement conditions.
Based on the above results, the calibration curve shown in Fig. 3 of the main body is made by approximating
the relationship between the carbon concentration and the average value of the normalized intensity ratio of eachsample at 4.2 K in Fig. C1 (b) in this commentary. The reason why the intensity ratios in Fig. C1 (a) were notaveraged simply is that the correlation curve for the organization having large intensity ratios is emphasized by
the simple average. Similarity of the correlation curve is equally reflected on a logarithmic axis by averaging
after the normalization of the intensity ratio in Fig. C1 (b).
As described in 8.2 in the main body, the error in the data point for sample G5 is large, because the oxygen
concentration of sample G5 (2.1×1017 atoms/cm3) exceeds a little the upper limit of this standard (2×1017
atoms/cm3). The correction method of the calibration curve for the oxygen concentration difference has alreadybeen studied and has been reported in Ref. 10 in detail. The calibration curve in Fig. 3 in the main body wasdetermined considering the above correction and slightly differs from the calibration curve in Fig. C1 (b) in thehigh carbon concentration range (>1×1015 atoms/cm3). In Ref. 10, the calibration curve in Fig. C1 (b) is denoted“old calibration curve”, and is distinguished from “revised calibration curve” in Fig. 3.
The detection limit has been verified to be reduced to approximately 4×1013 atoms/cm3 with increasing the
integration time of the detector from about 60 seconds in the round robin test to 1 hour.9).
7. Calibration
The correction of the calibration curve in this standard is basically the same as JIS H 0615. In JIS H 0615, thedonor and acceptor concentrations can be determined from the calibration curves without the correction in manycases, because the difference of the intensity ratio among organizations is small. However, the correction isnecessary in this standard, because the difference of the intensity ratio G/ITO among organizations is large, as

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described in IV 6.3 in this commentary. Since the intensity ratio is used as an index of the carbon concentrationand its correlation with the carbon concentration is given on the logarithmic scale, the calibration can be
performed by shifting the calibration curve in Fig. 3, as written in the main body.

Fig. C1:

Dependence of (a) intensity ratio and (b) normalized intensity ratio of G-line on carbon
concentration

Remark: Dependence of (a) intensity ratio G/ITO and (b) normalized intensity ratio [G/ITO]N on carbon
concentration for samples used in round-robin test in Table 1. (Organizations #1 to #7 measured at
4.2 K and organizations #8 to #10 measured at 15 K or 77 K.)

8. Accuracy and reliability
Carbon concentration is determined by SIMS to obtain the calibration curve in this standard. Therefore, theerror in SIMS measurement directly leads to the error of this method.
V. Standard samples
Samples in Table 1 used in round-robin test are the basis for the creation of the calibration curve in thisstandard. They are most suitable for the standard samples for the calibration. Japan Society of Newer Metals
defined these samples used in round-robin test as the primary standard samples. The Society prepared about 15
sets of the secondary standard samples and distributed them to related organizations. Lending of standard

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samples is also available from this society.
VI．References
1)

G. Davies and R. C. Newman: “Carbon in monocrystalline silicon,” Handbook of Semiconductors, eds. T.
S. Moss and S. Mahajan, Ch.21, p. 1557 (Elsevier, Amsterdam, 1994).

2)

J. Weber and M. Singh: “New method to determine the carbon concentration in silicon,” Appl. Phys. Lett.
49, 1617 (1986).

3)

M. Nakamura, E. Kitamura, Y. Misawa, T. Suzuki, S. Nagai, and H. Sunaga: “Photoluminescencemeasurement of carbon in silicon crystals irradiated with high energy electrons,” J. Electrochem. Soc. 141,3576 (1994).

4)

S. Nakagawa, K. Hirose, and M. Tajima: “Quantitative photoluminescence analysis of ultra-low
concentration of impurities in silicon wafers,” Proc. Science and Technology of Silicon Materials 2007, p.
227 (2007).

5)

S. Nakagawa: “Magnetic field-applied Czochralski silicon wafers for power devices,” Oyo Buturi, 84, 976(2015) [in Japanese].

6)

M. Tajima, A. Ogura: “Quantification of carbon in Si crystals by photoluminescence at liquid-nitrogen androom temperatures,” Oyo Buturi, 87, 655 (2018) [in Japanese].

7)

M. Tajima: “Determination of boron and phosphorous concentration in silicon by photoluminescenceanalysis,” Appl. Phys. Lett. 32, 719 (1978).

8)

M. Tajima, S. Samata, S. Nakagawa, J. Oriyama and N. Ishihara: “Round-robin test of photoluminescencemethod after electron irradiation for quantifying low-level carbon in silicon,” Jpn. J. Appl. Phys. 59,
SGGK05 (2020).

9)Y. Satake, M. Tajima, S. Asahara, and A. Ogura: “Detection limit of carbon concentration measurement in
Si for photoluminescence method after electron irradiation,” Jpn. J. Appl. Phys. 59, 126501 (2020).

10) M. Tajima, S. Samata, S. Nakagawa, Y. Shinozuka, J. Oriyama and N. Ishihara: “Calibration curve for thephotoluminescence method after electron irradiation for quantifying low-level carbon in silicon,” Jpn. J.
Appl. Phys. 60, 026501 (2021).

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List of committee members for JSNM-SI-002
Silicon PL Standardization Working Group
Name

Affiliation

Secretary

Shuichi Samata

SUMCO Corp.

MemberMichio Tajima

JAXA,Emeritus Professor

MemberMinoru Nakamura

Ibaraki University

MemberNaoyuki Kawai

ex-Tokyo University

Member(undisclosed)

GlobalWafers Japan Co., Ltd.

Member(undisclosed)

Siltronic Japan Corp.

Member(undisclosed)

Shin-Etsu Handotai Co., Ltd.

Member(undisclosed)

Tokuyama Corp.

Member(undisclosed)

Mitsubishi Materials Corp.

Member(undisclosed)

Toshiba Electronic Devices & Storage Corp.

Member(undisclosed)

Fuji Electric Co., Ltd.

Member(undisclosed)

Foundation for Promotion of Material Science and Technology of Japan

Member(undisclosed)

HORIBA, Ltd.

Member(undisclosed)

Eurofins EAG Materials Science Tokyo Corp.

Secretariat

Jun Oriyama

Japan Society of Newer Metals

Secretariat

Yoshihiko Saito

Japan Society of Newer Metals

Secretariat

Noriko Ohta

Japan Society of Newer Metals

Secretariat

Noriyuki Ishihara

Mizuho Information & Research Institute, Inc.

Silicon Standardization Promotion Committee
Name

Affiliation

ChairmanMichio Tajima

JAXA,Emeritus Professor

Secretary

Naoyuki Kawai

ex-Tokyo University

MemberShinichi Nishizawa

Kyushu University

Member(undisclosed)

GlobalWafers Japan Co., Ltd.

Member(undisclosed)

SUMCO Corp.
Advanced Evaluation & Technology Development Dept. Technology Div.

Member(undisclosed)

SUMCO Corp.
Planning & Engineering Section Epitaxial Engineering Dept. Technology Div.

Member(undisclosed)

Siltronic Japan Corp.

Member(undisclosed)

Shin-Etsu Handotai Co., Ltd

Member(undisclosed)

Tokuyama Corp.

Member(undisclosed)

Mitsubishi Materials Corp.

Member(undisclosed)

Toshiba Electronic Devices & Storage Corp.

JSNM-SI-002
Member(undisclosed)

Fuji Electric Co., Ltd.

Member(undisclosed)

Eurofins EAG Materials Science Tokyo Corp.

Secretariat

Jun Oriyama

Japan Society of Newer Metals

Secretariat

Yoshihiko Saito

Japan Society of Newer Metals

Secretariat

Shigeaki Saito

Japan Society of Newer Metals

Secretariat

Noriko Ohta

Japan Society of Newer Metals

Secretariat

Noriyuki Ishihara

Mizuho Information & Research Institute, Inc.

Standardization Committee
Name

Affiliation

ChairmanToshiro Hiramoto

University of Tokyo

MemberMichio Tajima

JAXA,Emeritus Professor

Member(undisclosed)

Global Advanced Metals Pty Ltd.

Member(undisclosed)

Nuclear Fuel Industries, Ltd.

Member(undisclosed)

JX Nippon Mining & Metals Corp.

Member(undisclosed)

Shin-Etsu Handotai Co., Ltd.

Member(undisclosed)

Taiyo Koko Co., Ltd.

Member(undisclosed)

NGK Insulators, Ltd.

Member(undisclosed)

Mitsui Mining & Smelting Co., Ltd.

Member(undisclosed)

Mitsubishi Nuclear Fuel Co., Ltd.

Secretariat

Jun Oriyama

Japan Society of Newer Metals

Secretariat

Noriko Ohta

Japan Society of Newer Metals

Secretariat

Kei Nemoto

Japan Society of Newer Metals（Author: Michio Tajima）

JSNM-SI-002

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JSNM-SI-002
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Published by Japan Society of Newer Metals (JSNM)
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