GOST 26239.7-84
GOST 26239.7−84 semiconductor Silicon. Method of determination of oxygen, carbon and nitrogen (with Change No. 1)
GOST 26239.7−84
Group B59
STATE STANDARD OF THE USSR
SILICON SEMICONDUCTOR
Method of determination of oxygen, carbon and nitrogen
Semiconductor silicon. Method of oxygen, carbon and nitrogen determination
AXTU 1709
Date of introduction 1986−01−01
The decision of the State Committee USSR on standards on July 13, 1984 N 2491* validity installed before
__________________
* See the label «notes»;
** Expiration removed by Protocol No. 7−95 Interstate Council for standardization, Metrology and certification (I & C N 11, 1995). — Note the manufacturer’s database.
The Change N 1, approved and in effect
Change No. 1 made by the manufacturer of the database in the text ICS N 10, 1990
This standard specifies a method for the determination of oxygen, carbon and nitrogen in semiconductor silicon using the activation by accelerated ions and Not protons within the ranges of values of mass fraction of impurities:
| oxygen instrumental analysis |
from 5·10 |
| the radiochemical allocation | from 1·10 |
| carbon instrumental analysis | from 2·10 |
| the radiochemical allocation | from 1·10 |
| the nitrogen radiochemical allocation | from 1·10 |
The method is based on irradiation of samples analysed samples and comparison with accelerated ions (determination of oxygen and carbon) and protons (determination of nitrogen) with subsequent measurement of induced activity of radioactive isotopes
F and
C in the spectrometer
of coincidences.
The content of impurities in the sample is determined by comparing the intensities of the pulse counting of radioactive isotopes detectable elements in the samples and the comparison samples.
1. GENERAL REQUIREMENTS
1.1. General requirements for method of analysis according to GOST 26239.0−84.
2. APPARATUS, MATERIALS AND REAGENTS
Particle accelerator — ion sources Not with the energy of 13 MeV at a current of ions in the beam 1−5 µa, source of protons with an energy of at least 6.5 MeV and a current of ions in the beam 1 to 5 µa.
Spectrometer -a match with crystal Nal (T1) having a size of not less than 100х70 mm.
Universal radiometer-dosimeter, type MKS-01R.
Boxy type 1K-NJ for radiochemical work with an additional protection of lead bricks and lead glass in accordance with the requirements of NRB-76/87/
Personal protective equipment against radiation and contamination by radioactive substances, in accordance with the requirements of OSP-72/87*.
_______________
* On the territory of the Russian Federation the document is not valid. Act SP 2.6.1.799−99. — Note the manufacturer’s database.
The stopwatch according to GOST 5072−79.
Analytical scale.
The laboratory centrifuge at a rotation speed of 5000 rpm.
Tile electric.
Caliper type В20034.
Water jet pump laboratory glass.
Copper washers with a diameter of 35 mm, height 13 mm with a set of detachable aluminum diaphragm with a thickness of 0.4−0.5 mm. the outside diameter of the diaphragms 30 mm hole diameters 7, 8, 9, 10, 11, 12, 13, 14 mm, 5−8 PCs. of each size.
Magazine aluminum, diameter 28 mm, height 5 mm. Thickness of bottom and lid of the cassette 1.5 mm.
Aluminium foil thickness 10, 15, 23, 34, 50, 70 µm.
The asbestos sheet.
A set of test tubes made of PTFE-4 with a capacity of 20 cm.
Tongs crucible.
Crucible Nickel 30 mm diameter, height 50 mm.
The furnace crucible is vertical, the diameter of the quartz insert, 60 mm, height 200 mm, power of 1.5 kW or similar furnace.
Rubber hose diameter of 6 mm.
Hose PVC with a diameter of 6 mm.
Silica gel chromatography of the brand KSK with a grain size of 100 µm.
Filter paper.
Semi-logarithmic paper according to GOST 334−73.
Tracing.
References: plate optical quartz glass marks KB size 15х15х3 mm; plate cut from pyrographite brand MPG-8, size 15х15х3 mm; plate of aluminum nitride with a size 15х15х3 mm.
The tweezers are metal.
Tweezers made of PTFE-4.
Metal spatulas.
Abrasive powders M28, M20, M14, M10 according to GOST 3647−80.
Gallium metal technical.
Indium metal according to GOST technical 10297−75*.
______________
* On the territory of the Russian Federation the document is not valid. Standards 10297−94. — Note the manufacturer’s database.
Cups of PTFE-4, with a diameter of 30−35 mm, a height of 25−30 mm.
The reaction flask is made of molybdenum glass with a capacity of 100 cmround bottom.
Pipettes Plexiglas for 5, 10 cm.
The flask Drexel with a capacity of 50, 100 cm.
Glasses glass with a capacity of 50, 100, 500 and 1000 cm.
The filter SCHOTT No. 4, with a diameter of 40 mm.
Bunsen flask with a capacity of 500 cm.
Glass measuring cylinders with a capacity of 25, 50 cm.
Measuring cylinders made of Plexiglas with a capacity of 10, 15 cm.
Glass volumetric flasks with a capacity of 500 cm.
Tube rubber.
Nitric acid GOST 4461−77, concentrated.
Sulfuric acid GOST 4204−77, concentrated.
Hydrofluoric acid according to GOST 10484−78, concentrated.
Lanthanum nitrate.
Sodium fluoride, technical.
Barium chloride technical GOST 742−78.
Ammonia water according to GOST 3760−79, H. h, concentrated and 25%.
Sodium nitrate technical GOST 828−77.
Sodium hydroxide according to GOST 4828−83*, CH.
______________
* On the territory of the Russian Federation the document is not valid. Valid GOST R 51135−98. — Note the manufacturer’s database.
Sodium bicarbonate according to GOST 2156−76, CH.
Diethyl ether, H. h
Carbon tetrachloride according to GOST 20288−74.
The technical rectified ethyl alcohol GOST 18300−87.
Distilled water GOST 6709−72.
Solution 1: a solution of lanthanum nitrate containing 0.2 g of lanthanum of 1 cm, 312 g of La (NO
)
·6H
O was dissolved with heating to 170 cm
of concentrated nitric acid, the solution was cooled to room temperature and transferred to a volumetric flask with a capacity of 500 cm
, then adjusted to the mark with distilled water.
Solution 2: mixture of acids for polishing and dissolution of silicon samples. Prepared in a polyethylene jar with a capacity of 500 cmof concentrated nitric and hydrofluoric acids in the ratio 3:1 by volume.
Determine the content of fluoride ion in the prepared mixture of acids: in the four glasses with a capacity of 50 cmpour 10 cm
of the solution 1 and heated on a hotplate to a boil. In the boiling solution 1 is poured to 5 cm
solution 2. Formed in each glass, the precipitate is lanthanum fluoride is separated by centrifugation, washed with 5 M nitric acid, ethyl alcohol ether, ether and dried to constant weight. For 100% release of lanthanum fluoride be the arithmetic mean of the masses of four selected precipitation.
Ammonia solution of barium chloride containing 0.14 g of barium 1 cm: 250 g of BaCl
·2H
O dissolved in distilled water, add 91 cm
of a 25% ammonia solution, transferred to a measuring flask with volume capacity of 1000 cm
and adjusted to the mark with distilled water. The solution was transferred to a beaker with a capacity of 2,000 cm
and bring to a boil. The cooled solution was filtered and stored in a hermetically sealed container. If the storage solution precipitate, the solution must be re-boiled and the precipitate filtered.
The gallium-indium alloy, similar in composition to the eutectic (20 to 30% India and 80 to 70% gallium) in a porcelain Cup was placed a mixture of gallium and indium in the ratio 7:3 by weight, is heated on a hot plate for 2−2. 5 h and cooled in air.
(Changed edition, Rev. N 1).
3. PREPARATION FOR ASSAY
3.1. Preparation of the analyzed silicon wafer samples and comparison to irradiation
3.1.1. To obtain one result of the analysis necessary to prepare and irradiate at least two parallel plates of silicon. For analysis preparing a silicon plate in the form of squares with a side of 12−14 mm and a thickness of 0.3−3.5 mm. the Surface selected for analysis of the plates must be chemically polished. To obtain the chemically polished surface of the silicon was first treated by abrasive powders M28, M20, M14, moving progressively from coarser powder to M28 M14. During manual polishing abrasive powder applied on a flat glass plate and moistened with water. For each issue of powder should be a separate plate. Powders treated with both the plane plate of silicon. The lateral surface is not treated. After grinding of each powder on the surfaces should not be scratched, the silicon wafer must be thoroughly clean from the previous powder.
The mixture of acids for chemical polishing (solution 2) in a quantity sufficient for total immersion of the plates, pour in a Cup made of PTFE. The silicon plate is clamped in tweezers made of PTFE and is immersed in a polishing mixture. In the process of polishing the mixture is stirred continuously. The polishing is done when the surface of the silicon wafer becomes shiny. Silicon is quickly removed from the polishing mixture, washed with running water and dried with filter paper. If the surface is scratched, the pores or sinks, the treatment should be repeated.
Samples from the surface of which the above defects when re-processing is not eliminated, are not suitable for analysis.
Selected for analysis of the silicon wafer weigh and measure with a micrometer the thickness at the geometric center, measure the geometric dimensions of the plate with calipers and calculated surface area.
Before you install the copper washer onto the plane of the silicon wafer opposite to the irradiated, is applied with wooden sticks indium-gallium eutectic. The wetted surface of the silicon plate is placed on the surface of a massive copper washers at its geometric centre, lightly pressed and grind to it, speaking of droplets of a eutectic is removed with a wooden stick, after which the silicon plate is placed an aluminum diaphragm and fix the position of clamping screws. The aperture opening should be 1−2 mm smaller than the diameter or side of square plate.
(Changed edition, Rev. N 1).
3.1.2. Copper washers with samples of comparison is prepared as follows: at the center of the copper washer is placed a reference sample (quartz, graphite or aluminum nitride) and fix his diaphragm and clamping screws.
If you want to reduce the energy of ions between the diaphragm and the reference sample placed foil made of aluminum, the thickness of which should correspond to the desired energy reduction.
3.2. Irradiation of silicon wafers and samples of comparison
Prepared copper washers with a silicon wafer loaded into a device for irradiation, periodically and randomly inserting between them a copper washer with samples comparison.
For each defined impurity should be prepared by 9 goals with the comparison samples irradiated at three different values of ion energy in the range from 6 to 10 MeV for He and from 4 to 6.5 MeV for protons.
In the determination of oxygen and carbon copper washers with the silicon wafer and the samples comparison (quartz and graphite) irradiated with ions, Not with the energy from 12.7 to 13 MeV.
When determining nitrogen silicon wafers and samples comparison of aluminum nitride irradiated with protons with an energy of 6.5 MeV.
The irradiation of plates of silicon, the current of singly charged ions is 1−5 µa, exposure time from 20 to 120 min.
Samples of comparison is irradiated with a current of 0.1 µa, exposure time of 1−3 min.
(Changed edition, Rev. N 1).
3.3. Treatment of irradiated samples comparison
Copper washers irradiated samples comparison of quartz kept in the packing box for 4−5 h, washers, graphite or aluminum nitride can withstand 1.5−2 hours
After aging the samples for the comparison are removed from the washers. Plate quartz wipe with a cotton swab moistened with alcohol, Packed in an aluminum cassette and transferred to the spectrometer -coincidences for measuring the curves of decay.
3.4. Processing of the silicon wafer after irradiation
After the end of irradiation of copper washers with the silicon wafer received in the packing box of the radiochemical laboratory, where they were kept for 5−10 min (for analysis with radiochemical selection of the analytical isotopes F or
C), or 30−45 min (instrumental analysis).
At the end of exposure, the silicon wafer is removed from the copper washers, clean the surface with a cotton swab moistened with alcohol and placed in a box for a chemical treatment.
In the determination of oxygen and carbon from the surface of the irradiated silicon wafer needs to be removed layer thickness of 45−50 microns, which corresponds to a decrease in ion energy from 13 to 10 MeV.
When determining the nitrogen (proton) from proton irradiated silicon wafer is removed layer thickness of 15−20 microns.
To remove the surface layer of the silicon wafer is treated in a mixture of hydrofluoric acid and nitric acid (solution 2). 10−15 cmof this mixture poured into two cups made of PTFE. The silicon plate is clamped in tweezers made of PTFE and is immersed in the Cup 1 so that the etching process she was completely immersed in the mixture. During the etching mixture is continuously stirred.
The plate of silicon is treated in the Cup 1 during a fixed time (30 or 60), then quickly remove it from the Cup, carefully washed with water, dried with filter paper and weighed. By difference between the mass of a sample before etching and after etching to determine the thickness strawling layer (a), µm, according to the formula
where 
— weight of sample before etching, mg;
— weight of sample after etching, mg;
— total surface of the silicon wafer, mm
.
If after processing in the Cup 1 thickness strawling layer is smaller than required, the etching continues in the Cup 2 with the speed of etching the silicon wafer in the Cup 1. Waste solutions were poured into a radioactive waste collections.
After etching the silicon plate is quickly extracted from the mixture of acids, washed thoroughly with water, dried, and weighed to determine total thickness strawling layer according to the formula (1). Stravinskogo thickness of the layer should be such that the activity remaining on the plate portion of the irradiated layer correspond to energies 10 MeV.
The thus treated silicon wafers transmit to instrumental analysis or subjected to further radiochemical processing.
(Changed edition, Rev. N 1).
4. ANALYSIS
4.1. Instrumental determination of oxygen and carbon in silicon
Instrumental method is used for determining the oxygen, carbon in polycrystalline silicon and undoped silicon and in silicon grown by the floating zone method, zone melting, as well as for the determination of oxygen in silicon grown by Czochralski method.
After removal of the surface layer (see p.3.4) plate of silicon is Packed in a cassette made of aluminium, and transmitted to the spectrometer -coincidences for measuring the curves of decay.
Before measurements, the spectrometer is a match with the source
Na is set to a registration mode annihilation
quanta, and then determine the natural background of the spectrometer.
Measuring the activity of the silicon wafer (the number of matches per unit of time) should be started one hour after the end of irradiation. During the first hours of measurements, when you register an activity With intervals between measurements of the activity must be 10−15 min, then the spacing between measurements of activity can be increased to 30−60 min. Time set of matches in each dimension is set such in which the statistical error (
Activity comparison of samples measured on a spectrometer of coincidences for two to four half-lives of the corresponding analytical isotope (for
F
With
With samples comparison of graphite and aluminum nitride are measured with an interval of 20−40 min,
F-samples comparison of quartz — interval 60−120 min.
The results of measurements of activity build on semi-logarithmic paper the curves of decay of radionuclides F and
C in the silicon wafer, and samples comparison. These curves are built in coordinates
the count rate analytical isotope, soup./min, measured in time
.
Decay curves based on the results of activity measurements of silicon wafers, usually composed of two components with half-lives 20,38 min (C) and to 109.8 (
F).
Treatment of decay curves is their graphical decomposition into components and finding by extrapolation of the counting rate of each isotope analytical (
F),
(
C) at the time of end of irradiation.
If during processing of the decay curves are mismatched half-lives found in the experiment, table values, analysis of the silicon wafers must be repeated with the use of radiochemical selection of the analytical isotopes.
Decay curves based on the results of measurement of activity of samples comparison, are single-labeled and must comply with the half-life for graphite, or
F for quartz. On these curves decay to determine the count rate is
F (
, cowp./min) in quartz and the count rate
C (
, cowp./min) in graphite at the time of end of irradiation.
The values of activity of samples comparison for three values of the energy of the activating particles used to construct the calibration curves of the dependences ,
on the energy of the trigger particle
, MeV. These calibration curves are used to determine the activity of samples comparisons at intermediate values of energy of an activating particle of the actual thickness removed from the silicon wafer surface layer.
Mass fraction of impurity in percent is calculated according to the formulas:
of oxygen 
carbon 
where ,
is the count rate of the radioisotope is
F and
s respectively at the time of end of irradiation in the silicon wafer corresponding to the energy of the particles
, cowp./min;
,
— count rate, the radioisotope is
F and
s respectively at the time of end of irradiation in quartz (SiO
) or graphite ©, the corresponding energy of the particles
, cowp./min;
,
,
— the average current of the activating particles during irradiation on the accelerator of silicon (
), quartz (SiO
) or graphite ©, mA;
,
,
— duration of irradiation on the accelerator of silicon (
), quartz (SiO
), and graphite ©, min.
The principle of measurement of decay curves, processing the measurement results and the final result is a concentration of the impurity in the wafer of silicon — the basis of automated system «AKAN» in the complex of the computer of EU-1010. The program processing of the measurement results is in the language «FORTRAN 4».
The analysis result should be the arithmetic mean of two calculated by the formula (2) or (3) results of parallel measurements, each obtained for one of the two silicon wafer, irradiated with a single mode of operation of the accelerator (without adjustment for energy).
The difference between the larger and the smaller of the two results of parallel measurements with a confidence probability of 0.95 does not exceed the allowable absolute values of the differences given in table.1.
Table 1
| Determined by the impurity | Mass fraction of impurities, % | The absolute allowable difference, % |
| Oxygen | 1·10 |
6,3·10 |
1·10 |
6,3·10 | |
1·10 |
6,3·10 | |
1·10 |
6,3·10 | |
5·10 |
3,0·10 | |
| Carbon | 1·10 |
5,5·10 |
1·10 |
5,5·10 | |
1·10 |
5,5·10 | |
2·10 |
1,0·10 |
The correctness of the results of analysis control method, which consists in the analysis of the same silicon wafer at two values of the energies of the activating particles. For control of correctness is taken from earlier analysis of silicon wafer samples with the content of controlled impurities at the level of 10-10
% by weight.
Carbon and oxygen determined at an energy of ions is Not 7.5 and 10 MeV, in the determination of nitrogen plate is irradiated with protons with energy of 5 and 6.5 MeV.
The results of the analysis you think is right with confidence probability of 0.95, if the difference between the found at different energies of the particles concentrations of impurities does not exceed the absolute permissible differences given in table.1.
(Changed edition, Rev. N 1).
4.2. Analysis using radiochemical selection of the analytical isotopes
4.2.1. The determination of oxygen in silicon with the use of radiochemical selection
The method used for the determination of oxygen in silicon, when it is necessary to eliminate the influence of impurities sources of positron activity. Interference from impurities and the necessity of their elimination set by results of processing of the decay curves in the analysis of silicon by instrumental method in accordance with claim 4.1.
To determine the oxygen content with the use of radiochemical selection F of the silicon plate after the instrumental analysis according to claim 4.1 must be processed again in accordance with clause 3.1, re-irradiated, matured after the end of irradiation for 5−10 min and treated in accordance with clause 3.4, after which the silicon wafer is transferred to a box N 2 for radiochemical work.
In a Cup made of PTFE pour 5 cmof a mixture of concentrated hydrofluoric and nitric acids with a known content of fluorine (solution 2) and a pair of tweezers made of PTFE immersed in the silicon.
During the dissolution in the mixture of the thickness of the silicon wafer must be reduced to not less than 300 microns. The amount of silicon transferred to the solution, control for reducing the weight of the silicon plate , mg, taking into account its entire surface
, mm
(see clause 3.4).
In the reaction flask of the device for distillation of fluorine (Fig.1) put 250−300 mg of crushed silica gel, a flask, close the funnel with a glass stopper and connected to a water-jet pump, whereupon the flask is poured a mixture of 2 of the PTFE Cup containing the dissolved silicon, and pour 10−15 cmof concentrated sulfuric acid.
Damn.1. Device for distillation of the compounds of fluorine with the silicon of molybdenum glass
Device for distillation of the compounds of fluorine with the silicon of molybdenum glass
1 — reaction flask; 2 — tube with silica gel impregnated with concentrated sulfuric acid; 3 — receiver fluorine containing 15 cmof distilled water
Damn.1
Fluoride of silicon was removed in 3−5 min with the running water jet pump and absorb the distilled water in the receiver 3. After distilling off the receiver 3 is detached from the device, and then disconnect the water-jet pump.
The solution from the receiver 3 is poured into a glass beaker with a capacity of 100 cm, containing 15 cm
, heated to the boiling point of the solution of lanthanum nitrate (solution 1) and heating was continued for another 1 min, constantly stirring the solution.
Precipitate lanthanum fluoride is separated by centrifugation, washed successively with hot 5 M nitric acid, alcohol, ester, ether and then dried by placing the tube with the sediment in close proximity to electric.
Duration of chemical for precipitation of lanthanum fluoride does not exceed 20−30 min.
The dried precipitate is lanthanum fluoride is transferred to tracing paper, wrapped in it, the tracing is placed in an aluminum cassette and transferred to the spectrometer -coincidences for measuring the curve of decay.
The activity precipitate lanthanum fluoride measured on the spectrometer coincidence with the intervals between measurements 30−60 min. Measurement done when the activity of the sediment will drop to the background level of the spectrometer.
The results of measurements build the curve of the collapse 
F in the fluoride of lanthanum
, cowp./min, at the end of the exposure extrapolation method.
After measurements are completed, the precipitate lanthanum fluoride is extracted from aluminium cassette and weighed. The chemical yield of fluorine is defined as the ratio of the mass of sediment
selected in this experiment the sediment
Mass fraction of impurities (oxygen) in percent is calculated by the formula
where is the count rate of the radioisotope
F at the time of end of irradiation in the silicon wafer corresponding to the energy of the particles
, cowp./min;
— the count rate of the radioisotope
F at the time of end of irradiation in quartz (SiO
), the corresponding energy of the activating particles
, cowp./min;
,
— average current activated particles irradiation on the accelerator, respectively, of silicon (
), quartz (SiO
), mA;
,
— duration of irradiation on the accelerator, respectively, of silicon (
), quartz (SiO
), min;
— chemical release of fluoride.
The measurement of decay curves of selected precipitation lanthanum fluoride and handling of measurement results provided by the program drawn up for the automated system «AKAN» in the complex of the computer of EU-1010, written in «FORTRAN-4».
The analysis result should be the arithmetic mean of two calculated by the formula (5) results of parallel measurements, each obtained for one of the two silicon wafer, irradiated with a single mode of operation of the accelerator (without adjustment for energy).
The difference between the larger and the smaller of the two results of parallel measurements with a confidence probability of 0.95 does not exceed the allowable absolute values of the differences given in table.2.
Table 2
| Mass fraction of impurities of oxygen, % |
The absolute allowable difference, % |
1·10 |
7,0·10 |
1·10 |
7,0·10 |
1·10 |
7,0·10 |
1·10 |
7,0·10 |
5·10 |
3,0·10 |
The correctness of the results of analysis control according to claim 4.1.
4.2.2. The determination of oxygen and carbon in silicon with the use of radiochemical selection of fluorine and carbon.
The method is applied in cases where it is necessary to eliminate the mutual influence of oxygen and carbon and other impurities — sources positron activity on the results of the analysis.
In the Nickel crucible is placed 2 g of sodium hydroxide, 1 g of sodium nitrate, 0.8 g of sodium fluoride and 0.3 g of sodium carbonate, the crucible, put the crucible in the oven, preheated to 200−250 °C, kept there until the cessation of gassing. Then remove the crucible from the furnace, cooled in air up to 100−150 °C, after which in the melt are immersed a sample of silicon. The temperature in the furnace increased to 400−450 °C, the crucible with the sample put in the oven and hold fusion for 4−5 min. After the fusion of the Nickel crucible 1 is removed from the furnace, cooled in air up to 100−150 °C and placed on the bottom of the reaction vessel 2 of the device (Fig.2).
Damn.2. Device for distillation of fluorine compounds with silicon and of carbon dioxide from molybdenum glass
Device for distillation of fluorine compounds with silicon and of carbon dioxide from molybdenum glass
1 — Nickel crucible with the cooled melt; 2 — reaction vessel; 3 — tube with silica gel impregnated with concentrated sulfuric acid; 4 — receiver of the fluorine containing 15 cmof distilled water; 5 — intermediate tank; 6 — receiver of carbon dioxide, containing 15 cm
of ammonia solution of barium chloride
Damn.2
The reaction vessel is closed, the drip funnel, a device for distillation of gases is connected to the water-jet pump. In the reaction vessel using a funnel pour the drip of 10−15 cmof concentrated sulfuric acid. After 4−5 min after start of the reaction the flask was poured 1.5−2 cm
of water. The Stripping continued for another 3 min, and then sequentially turn off the receivers 3, 5 and the water jet pump.
4.2.2.1. The determination of oxygen
From the solution contained in the receiver 4, the isolated precipitate lanthanum fluoride according to claim
The chemical yield of the fluorine is determined by the formula
where is the mass of the precipitate lanthanum fluoride capitalized in this experience,
Mass fraction of oxygen impurity is calculated by the formula (5).
The analysis result should be the arithmetic mean of two calculated by the formula (5) results of parallel measurements, each obtained for one of the two silicon wafer, irradiated with a single mode of operation of the accelerator (without adjustment for energy).
The difference between the larger and the smaller of the two results of parallel measurements with a confidence probability of 0.95 does not exceed the allowable absolute values of the differences given in table.3.
Table 3
| Mass fraction of impurities of oxygen, % |
The absolute allowable difference, % |
1·10 |
7,0·10 |
1·10 |
7,0·10 |
1·10 |
7,0·10 |
1·10 |
7,0·10 |
The correctness of the results of analysis control according to claim 4.1.
4.2.2.2. Determination of carbon
From the solution contained in the receiver 6, allocate the precipitate of barium carbonate. To do this, the contents of the receiver 6 is poured into a glass. Beaker cover watch glass, put on the hotplate and boil for 1−2 min. Then solution was cooled, the precipitate is collected on a paper filter placed on the bottom of the funnel SCHOTT. The filtration is performed at a vacuum created a water vacuum pump. The precipitate was washed successively with cold solution of barium chloride, alcohol, ether, and dried in air. The filter with the precipitate is transferred to tracing paper, wrapped in it. Tracing paper with precipitate was placed in an aluminum cassette for activity measurement by the spectrometer of coincidences.
The activity highlighted the precipitate barium carbonate measured in the first hour, every 10−15 minutes, then the interval between measurements may be increased to 30−60 min. Measurement is done when the activity of the barium carbonate will be reduced to background level in the measurement setup.
According to the results of measurements of activity build the curve of the decay 
With the carbonate of barium
at the time of end of irradiation.
After measurements are completed, the precipitate of barium carbonate is extracted from aluminium cassette and weighed. The chemical yield of carbon is defined as the ratio of the mass of the precipitate barium carbonate, corresponding to 100% of the allocation entered in the experience of stable isotopic carrier carbon 0,558 g, to the weight selected in this experiment the sediment
Mass fraction of impurities (carbon) in percent is calculated by the formula
where is the count rate of the radioisotope
From the time of end of irradiation in the silicon wafer corresponding to the energy of the particles
, cowp./min;
the activity of the radioisotope
From the time of end of irradiation in graphite © at the energy of the trigger particle
, cowp./min;
,
is the average current of the activating particles during irradiation, respectively of silicon (
) and graphite ©, mA;
,
— duration exposure, respectively, of silicon (
) and graphite ©, min;
— chemical yield of carbon.
The measurement of decay curves of selected precipitation of barium carbonate and the processing of the measurement results provided by the program drawn up for the automated system «AKAN» in the complex of the computer of EU-1010, written in «FORTRAN-4».
The analysis result should be the arithmetic mean of two calculated by the formula (8) results of parallel measurements, each obtained for one of the two silicon wafer, irradiated with a single mode of operation of the accelerator (without restructuring energy).
The difference between the larger and the smaller of the two results of parallel measurements with a confidence probability of 0.95 does not exceed the allowable absolute values of the differences given in table.4.
Table 4
| Mass fraction of impurities of carbon, % |
The absolute allowable difference, % |
1·10 |
8,3·10 |
1·10 |
8,3·10 |
1·10 |
8,3·10 |
2·10 |
8,3·10 |
The correctness of the results of analysis control according to claim 4.1.
4.2.3. Determination of nitrogen in silicon with the use of a radiochemical carbon emissions
The method used to determine the nitrogen content in the silicon, if the mass fraction of boron does not exceed 1·10%.
When determining the nitrogen from the apparatus for distillation (Fig.2) delete the receiver 4, connecting tube with silica gel 3 and the intermediate container 5 vinyl chloride pipe. The determination is performed as specified in claim
The analysis result should be the arithmetic mean of two calculated by the formula (8) results of parallel measurements, each obtained for one of the two silicon wafer, irradiated with a single mode of operation of the accelerator (without adjustment for energy).
The difference between the larger and the smaller of the two results of parallel measurements with a confidence probability of 0.95 does not exceed the allowable absolute values of the differences given in table.5.
Table 5
| Mass fraction of impurities of nitrogen, % |
The absolute allowable difference, % |
1·10 |
9,5·10 |
1·10 |
9,5·10 |
1·10 |
9,5·10 |
The correctness of the results of analysis control according to claim 4.1.
4.2.1, 4.2.2,
