Background Statement for SEMI Draft Document 5564B
New Standard: Test Method for the Measurement of Chlorine in
Silicon by Ion Chromatography
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Background Statement
Nowadays more and more Granular silicon are produced and used. Thus the quality of polysilicon is very
important for the users. As researched, there are more Chlorine remained in the granular silicon than that
in chunk. Chlorine remained in the silicon may affect the quality. Therefore, it is necessary to develop a
standardized method to measure the Chlorine in silicon.
Review and Adjudication Information
Task Force Review
Group:
PV Silicon Raw Materials Task Force
Committee Adjudication
China PV Committee
Date:
TBD
Sep. 12th, 2014
Time &Timezone:
TBD
09:30 -16:50, Beijing Time
Location:
TBD
Grand Ballroom, 3F, Shangri-La Hotel Dalian
City,
State/Country:
China
Dalian, Liaoning, China
Leader(s):
Li He (CPVT)
Xiaoxia Liu( GCL)
Dazhou Yan(SINOSICO)
Guangchun Zhang(CanadianSolar)
Jun Liu(CESI)
Standards Staff:
Kris Shen(SEMI China)
kshen@semi.org
Kris Shen(SEMI China)
kshen@semi.org
Meeting date and time are subject to change, and additional TF review sessions may be scheduled if
necessary. Contact the task force leaders or Standards staff for
confirmation.Checkwww.semi.org/standards for the latest schedule.
If you have any questions, please contact the Poly-Silicon TF Leader.
Xiaoxia Liu/ GCL
Tel: +86 516 85868888-88500
E-mail: liuxiaoxia@gclsolarenergy.com
Or contact SEMI Staff, Kris Shen at kshen@semi.org
Semiconductor Equipment and Materials International
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DRAFT
SEMI Draft Document 5564B
New Standard: Test Method for the Measurement of Chlorine in
Silicon by Ion Chromatography
1 Purpose
1.1 The quality of polysilicon is very important for the user. Nowadays more and more granular silicon are
produced and used to produce polysilicon for used in the photovoltaic industry. As researched, there are more
chlorine remained in the granular silicon than that in chunk. Chlorine remained in the silicon will affect the quality.
Thus, it is necessary to develop a method to measure the chlorine in silicon.
1.2 This test method can facilitate unifying of protocols and test results among worldwide laboratories used for
monitoring or qualifying chlorine in silicon.
2 Scope
2.1 This Standard provides a test method for the Chlorine in silicon by Ion Chromatography.
2.2 This test method can be used for various rod, chunk, granule and chip sizes, for polysilicon, to determine the
content of Chlorine. In addition to the Granular silicon, other form of silicon needs to be pulverized, in particle size
range 200-3000 µm.
2.3 Relative units ppbw and ppmw are used for impurity concentration values in this test method. For conversion to
other units, see SEMI AUX022.
NOTICE: SEMI Standards and Safety Guidelines do not purport to address all safety issues associated with their
use. It is the responsibility of the users of the Documents to establish appropriate safety and health practices, and
determine the applicability of regulatory or other limitations prior to use.
3 Limitations
3.1 None
NOTE 1: This test method uses high-purity acid to neutralization. The etchant is potentially harmful and should be handled in
exhaust fume-hood, with utmost care at all times. Nitric acid solutions are particularly hazardous and should not be used by
anyone who is not familiar with the specific preventive measures.
NOTE 2: Take the utmost care to ensure all contact to the sample containers should be pure, rinse it with copious amounts of DI
water and use nitrogen to blow clean.
4 Referenced Standards and Documents
4.1 SEMI Standards and Documents
SEMI C35 –– Specifications and Guideline for Nitric Acid
SEMI AUX022 –– Conversion of Units for Impurity Concentrations in Silicon
4.2 ASTM Standards1
ASTM D1193 — Standard Specification for Reagent Water
ASTM E122 — Standard Practice for Calculating Sample Size to Estimate, With Specified Precision, the Average
for a Characteristic of a Lot or Process
4.3 Federal Standard2
ISO/DIS 14644-1 — Clean-rooms and associated controlled environments—Part 1: Classification of air cleanliness
by particle concentration
NOTICE: Unless otherwise indicated, all documents cited shall be the latest published versions.
1
American Society for Testing and Materials, 100 Barr Harbor Drive, West Conshohocken, PA 19428-2959, USA; Telephone: 610.832.9585,
Fax: 610.832.9555, http://www.astm.org
2
Federal Standard, c/o U.S. Government Printing Office, Washington DC, 20402, USA
This is a Draft Document of the SEMI International Standards program. No material on this page is to be construed as an official or adopted Standard or Safety Guideline.
Permission is granted to reproduce and/or distribute this document, in whole or in part, only within the scope of SEMI International Standards committee (document
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5 Terminology
5.1 Refer to SEMI Standards Compilation of Terms (COTs) for a list of the most current terms and their definitions.
5.2 Abbreviations and Acronyms
5.2.1 IC — Ion Chromatography
5.2.2 ppmw — part per million weight
5.2.3 ppbw — part per billion weight
5.3 Definitions
5.3.1 Granular silicon, n — nearly spherical, granules (200—3000µm) of silicon as produced in a fluidized bed
reactor.
5.3.2 Method blank — a solution of acid prepared using the preparation method without a specimen or test sample
used to establish the contribution of trace Chlorine contamination from the laboratory environment, reagents or
labware to the background.
5.3.3 Certified Reference Material (CRM) — a NIST traceable single or multi-element solution standard.
5.3.4 Reference samples — samples prepared to known concentrations of the analytes, typically 0.1 ppmw, 0.2
ppmw, 0.5 ppmw, 1 ppmw and 2 ppmw to provide a Chlorine standard for the IC instrument.
6 Summary of Test Method
6.1 Dissolve —The sample was dissolved in a 50% NaOH solution then the chlorine ion separate out.
6.2 Neutralization — Using distilled high purity nitrate to adjust the pH to neutral.
6.3 Measurement — After filtration and centrifugation, the sample is injected into to the IC, then the content of
chlorine ion is analyzed.
7 Apparatus
7.1 IC — Ion Chromatography instruments
7.2 Electronic Balance(s) — 0.1 mg accuracy for weighing NaOH reagents and silicon samples.
7.3 Pipette — 2、10、20 ml, used to transfer liquid reagents
7.4 Penicillin vials — Approximately 20 ml in volume, for collecting samples.
7.5 beaker(plastics or glass) — 100 ml in volume, for neutralization
7.6 Acid Exhaust Fume Hood — To provide for exhaust of acid fumes, a clean air environment (ISO Class 6
minimum, as defined in ISO 14544-1), a drain for acids and water, and a deionized water supply. This hood provides
for the cleaning of glass containers and neutralization.
7.7 Ultrasound equipment — Eluentssonicated for an IC instrument.
7.8 Centrifuge — Used to separate the samples
7.9 Intelligent digital water bath — For sample heating
8 Reagents and Materials
8.1 Ultra-Pure Water — Unless otherwise indicated, reagent water should be conforming to specification ASTM
D1193.
8.2 Nitrogen — 99.5 % (m/m) minimum
8.3 Sodium hydroxide reagent — Electronic level, in which chloride is less than 5ppm.
This is a Draft Document of the SEMI International Standards program. No material on this page is to be construed as an official or adopted Standard or Safety Guideline.
Permission is granted to reproduce and/or distribute this document, in whole or in part, only within the scope of SEMI International Standards committee (document
development) activity. All other reproduction and/or distribution without the prior written consent of SEMI is prohibited.
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Document Number: 5564B
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8.4 Nitric Acid (HNO3) — 65%,in accordance with Grade 2 of SEMI C35.Distilled into high-purity nitrate.
8.5 Chlorine reference solution — GBW(E)080268, Concentration value of 1000mg/L,
8.6 0.74g/ml NaOH solution — Add 50grams NaOH into 50ml water, mix. Used for digestion silicon samples,
8.7 Disposable filter — 0.45m, used to filter samples.
9 Safety Precautions
9.1 The acids used in this practice are potentially harmful and must be handled with the utmost of care at all times.
Nitric Acid (HNO3) solutions are especially hazardous to the eyes, skin, mucous membranes, and the lungs. Anyone
using HNO3 and other acids must be familiar with the potential hazards and must employ proper techniques and
preventive measures to avoid injury.
10 Sampling
10.1 This test method is intended for sampling of silicon lots. Typically, one 5-kg bag from a lot is selected for
sampling. The sample is taken from this bag, and the Chlorine values analyzed are assumed representative of the lot.
Statistical techniques, such as process capability ratios, are used to determine actual sampling plans for
manufacturing processes. A choice of sampling plans is found in ASTM Practice E122. For referee purpose, a
sampling plan shall be agreed upon before conducting the test. Contamination during the sampling procedure is a
critical concern and shall be avoided.
11 Preparation of Apparatus
11.1 Requirements according to the sample configuration corresponding concentration of sulfuric acid solution,
eluent — use 0.45 m filter membrane filtration then ultrasound it for 10 minutes.
11.2 Operating exhaust — the needle valve is loosen. The workstation is manually set with the pump flow rate of
2.0ml/min. The air should be suctioned with a syringe from the needle valve until the eluent continuous outflow
from the needle valve with no bubbles. Before tightening the valve, pump flow rate shall be set at 0.7ml/min, and
care should be taken to avoid damaging to the separation column.
11.3 The samples should not be analyzed before the baseline of the instrument is stable.
12 Calibration and Standardization
12.1 Method Blank — a solution of acid prepared using the preparation method without a specimen or test sample
used to establish the contribution of trace Chlorine contamination from the laboratory environment, reagents or
labware to the background.
12.2 Calibration Graph — Use the Cl- standard solution in ¶8.5, configured into a standard solution of 0.1, 0.2, 0.5,
1,2ppmw, using an ion chromatograph to analyze, produce a calibration graph based on workstation applications, for
the quantitative analysis of the silicon sample.
13 Procedure
13.1 Weigh 0.5000±0.1000 gram silicon for the sample dissolved in 10ml of 50% NaOH solution count sample 1;
another 10 ml of 50% NaOH solution is used as the method blank count sample 2. Two samples are done parallel
samples.
13.2 Take the weighing vial completed on water bath digestion(half covered, not tighten), set the temperature as
70℃，it takes 4-12 hours digesting, which is determined by the quality/size of the silicon.
13.3 When the sample digestion completed, transfer each of the samples and blank solutions into a glass beaker,
rinse the weighing vials twice by Ultra-Pure Water.
13.4 Use the High-purity nitric acid to adjust the solution to neutral (make sure the pH is fit for the instrument),
cool down the solution, transfer it into a 100ml volumetric flask, rinse the beaker with DI water more than 2 times
into the volumetric flask, dilute with DI water to volume, and mix. Take about 35ml from the flask into a centrifugal
with a rotational speed of 2500 r/min, 20 minutes.
This is a Draft Document of the SEMI International Standards program. No material on this page is to be construed as an official or adopted Standard or Safety Guideline.
Permission is granted to reproduce and/or distribute this document, in whole or in part, only within the scope of SEMI International Standards committee (document
development) activity. All other reproduction and/or distribution without the prior written consent of SEMI is prohibited.
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13.5 Take 20ml sample solution through the 0.45m filter; transfer 10ml into a 100ml volumetric flask, dilute with
DI water to volume, and mix. The preparation of sample for the instrument (Ion Chromatography) is completed.
13.6 Measure the sample solutions by Ion Chromatography.
14 Calculations
14.1 Chlorine concentration of sample(ppmw, mg/kg):
Computing formula: wc  C0  C1   R  V
m  10 6
(1)
Where:
C0: the chlorine concentration of sample solution, mg/L
C1: the concentration of blank, mg/L;
V: volume of sample solution, L
R: dilution factor;
m: the mass, in grams, of the silicon tested.
15 Report
15.1 The results to be reported — use the arithmetic mean of the parallel samples’ results which should be in a
reasonable range of deviation.
16 Technical specifications of the IC
16.1 Parameters of the instrument in Table 1 below are for reference:
Table 1 Parameter of the IC Instrument
Pump flow rate
0.7ml/min
Loop
20ul
Chromatographic column
Metrosep A supp5-150/4.0
Automatic sampler
Intelligent Dosino 800
MSM switching period
every 10 minutes
Operating pressure
About 9Mpa
Peristaltic pump rate
18r/min 0.3ml/min
Workstation
MagIC NET 2.2
The eluent
3.2mmol/L Na2CO3 and 1mmol/L NaHCO3
MSM Regeneration solution
100mmol/L H2SO4
MSMRinse solution
Ultra-Pure Water
17 Related Document
BS EN ISO 9556:2001—Steel and iron—Determination of the total carbon content— Infrared absorption method
after combustion in an induction furnace.
This is a Draft Document of the SEMI International Standards program. No material on this page is to be construed as an official or adopted Standard or Safety Guideline.
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NOTICE: Semiconductor Equipment and Materials International (SEMI) makes no warranties or representations as
to the suitability of the Standards and Safety Guidelines set forth herein for any particular application. The
determination of the suitability of the Standard or Safety Guideline is solely the responsibility of the user. Users are
cautioned to refer to manufacturer’s instructions, product labels, product data sheets, and other relevant literature,
respecting any materials or equipment mentioned herein. Standards and Safety Guidelines are subject to change
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rights or copyrights asserted in connection with any items mentioned in this Standard or Safety Guideline. Users of
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This is a Draft Document of the SEMI International Standards program. No material on this page is to be construed as an official or adopted Standard or Safety Guideline.
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