GB/T 38976-2020 English PDF (GBT38976-2020)

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GB/T 38976-2020: Test method for the oxygen concentration in silicon materials--Inert gas fusion infrared detection method
GB/T 38976-2020
GB
NATIONAL STANDARD OF THE
PEOPLE’S REPUBLIC OF CHINA
ICS 77.040
H 17
Test method for the oxygen concentration in silicon
materials - Inert gas fusion infrared detection method
ISSUED ON: JULY 21, 2020
IMPLEMENTED ON: JUNE 01, 2021
Issued by: State Administration for Market Regulation;
Standardization Administration of the People's Republic of
China.
Table of Contents
Foreword ... 3 
1 Scope ... 4 
2 Normative references ... 4 
3 Terms and definitions ... 4 
4 Method principle ... 4 
5 Disturbing factors ... 5 
6 Reagents ... 6 
7 Instruments ... 7 
8 Samples ... 7 
9 Drawing of calibration curve ... 8 
10 Test steps ... 8 
11 Precision ... 9 
12 Test report ... 9 
Test method for the oxygen concentration in silicon
materials - Inert gas fusion infrared detection method
1 Scope
This Standard specifies the method that uses inert gas melting and infrared
technology to test the oxygen concentration in silicon materials.
This Standard is applicable to the tests of oxygen content in silicon single crystal
and polycrystalline silicon with different conductivity types and different
resistivity ranges. The test range is 2.5×1015cm-3 (0.05ppma) ~ 2.5×1018cm-3
(50ppma).
NOTE: The oxygen content in silicon materials is measured in the number of atoms per
cubic centimeter.
2 Normative references
The following referenced documents are indispensable for the application of
this document. For dated references, only the edition cited applies. For undated
references, the latest edition of the referenced document (including any
amendments) applies.
GB/T 1557, Test method for determining interstitial oxygen content in silicon
by infrared absorption
GB/T 14264, Semiconductor materials - Terms and definitions
3 Terms and definitions
For the purposes of this document, the terms and definitions defined in GB/T
14264 apply.
4 Method principle
Place the pre-weighed sample in a high-purity double-layer graphite crucible.
The sample is heated and melted at high temperature under the protection of
inert gas to release oxygen, nitrogen and hydrogen. The oxygen in the sample
combines with the carbon in the graphite crucible to form carbon monoxide.
Nitrogen and hydrogen are released as nitrogen and hydrogen, respectively.
Depending on the test instrument, the content of carbon monoxide can be
directly measured by a non-dispersive infrared detector. It is also possible to
oxidize carbon monoxide through a heated rare earth copper oxide catalyst
under the transportation of inert gas to generate carbon dioxide, and the content
of carbon dioxide is measured by infrared testing equipment. The test
instrument performs blank deduction based on the content of carbon monoxide
or carbon dioxide. Combined with the weight of the sample, the oxygen content
in the tested sample is finally obtained.
5 Disturbing factors
5.1 Inert gas (helium or argon) is as the carrier gas in the test instrument. The
impurities contained therein may adsorb the oxygen released by the silicon
material sample, thereby affecting the test results. Therefore, it is
recommended to use high purity gas with a purity (volume fraction) not less
than 99.99% to improve the accuracy of the test. At the same time, sodium
hydroxide (super-grade pure) can be used to absorb the residual carbon dioxide
in the inert gas. Anhydrous magnesium perchlorate (MgClO4) is used to absorb
water in inert gas. Copper chips are used to absorb oxygen in the inert gas.
Reduce the influence of the inert gas on the test results.
5.2 The use of single-layer graphite crucible will cause temperature fluctuations,
which will affect the test results, so double-layer graphite crucibles shall be used.
5.3 The oxygen in the graphite crucible will also continue to be released during
the test. Therefore, crucibles made of high-purity graphite shall be used.
Confirm the purity of the graphite crucible before the test to reduce the impact
on the test results.
5.4 The calibration curve is the key to the reliability of oxygen content testing.
The establishment of the silicon single crystal calibration curve is based on the
test results of the interstitial oxygen content in the silicon single crystal sample
by the method specified in GB/T 1557. Therefore, it is necessary to ensure that
the test values of the samples used to establish the calibration curve are
accurate and reliable.
5.5 This method uses the test results of GB/T 1557 as the calibration curve,
which indirectly reflects the interstitial oxygen content in silicon. The oxygen
content value measured by this method is directly related to the gap oxygen
content calibration factor selected by the calibration curve.
5.6 The detection limit of this method is related to the blank value of the
instrument. The difference of the test equipment and the difference in the test
process will have an impact on the detection limit.
9 Drawing of calibration curve
Use at least 2~3 silicon single crystal reference samples with traceable oxygen
content and 1 blank reference sample. Test according to GB/T 1557 and
10.4.1~10.4.5 respectively. Establish a calibration curve. The oxygen content
range of the reference sample shall cover the oxygen content of the sample to
be tested.
10 Test steps
10.1 Instrument preparation
Check the working status of the instrument. After the instrument is fully warmed
up, perform leak detection and analysis to ensure that the instrument has no air
leakage.
10.2 Blank test
Use an empty double-layer graphite crucible to perform a blank test according
to 10.4.2~10.4.5. Test at least 3 times in parallel. Take the average value until
the standard deviation of the blank value is not more than 5×1013cm-3
(0.001ppma). Enter the average value of the blank value and establish a blank
deduction.
10.3 Instrument calibration
Use 1~2 samples with known oxygen content. Test according to 10.4.1~10.4.5.
Verify whether the test value conforms to the calibration curve. Set the drift
calibration value according to the bias of the test value.
10.4 Determination
10.4.1 Weigh 0.3g~1.0g (to the nearest of 0.001g) of sample and put them into
the loading port of the instrument.
10.4.2 Place an empty double-layer graphite crucible on the lower electrode of
the instrument and raise it to the test position.
10.4.3 According to the operation process of the instrument, start the crucible
exhaust process.
10.4.4 The sample is transferred to the crucible. After the in-situ degassing
cycle removes the oxide layer on the surface of the sample (refer to 5.11 for
details), the heating and melting process of the sample is started.
10.4.5 The oxygen in the sample is released and converted into carbon
monoxide or carbon dioxide. Its content is measured by infrared test method.
10.4.6 After correcting according to the calibration curve, the instrument
automatically calculates according to the input sample weight, and directly
outputs the oxygen content.
11 Precision
11.1 This method combines the infrared test method specified in GB/T 1557,
which is generally recognized in the industry, to draw the calibration curve.
Therefore, the comparison with GB/T 1557 directly affects the accuracy of this
method. In the same laboratory, select 3 silicon single wafers with a diameter
of 150mm. In the diameter direction of the same silicon wafer, select a test point
every...