WO2023243466A1 - Method for producing purified trichlorosilane - Google Patents
Method for producing purified trichlorosilane Download PDFInfo
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- WO2023243466A1 WO2023243466A1 PCT/JP2023/020839 JP2023020839W WO2023243466A1 WO 2023243466 A1 WO2023243466 A1 WO 2023243466A1 JP 2023020839 W JP2023020839 W JP 2023020839W WO 2023243466 A1 WO2023243466 A1 WO 2023243466A1
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- WO
- WIPO (PCT)
- Prior art keywords
- trichlorosilane
- concentration
- isopentane
- crude
- methyldichlorosilane
- Prior art date
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- ZDHXKXAHOVTTAH-UHFFFAOYSA-N trichlorosilane Chemical compound Cl[SiH](Cl)Cl ZDHXKXAHOVTTAH-UHFFFAOYSA-N 0.000 title claims abstract description 292
- 239000005052 trichlorosilane Substances 0.000 title claims abstract description 290
- 238000004519 manufacturing process Methods 0.000 title claims abstract description 21
- QWTDNUCVQCZILF-UHFFFAOYSA-N isopentane Chemical compound CCC(C)C QWTDNUCVQCZILF-UHFFFAOYSA-N 0.000 claims abstract description 261
- 238000004821 distillation Methods 0.000 claims abstract description 205
- AFABGHUZZDYHJO-UHFFFAOYSA-N dimethyl butane Natural products CCCC(C)C AFABGHUZZDYHJO-UHFFFAOYSA-N 0.000 claims abstract description 130
- 238000009835 boiling Methods 0.000 claims abstract description 103
- KTQYJQFGNYHXMB-UHFFFAOYSA-N dichloro(methyl)silicon Chemical compound C[Si](Cl)Cl KTQYJQFGNYHXMB-UHFFFAOYSA-N 0.000 claims abstract description 94
- 239000005048 methyldichlorosilane Substances 0.000 claims abstract description 94
- 238000000746 purification Methods 0.000 claims abstract description 39
- 230000002829 reductive effect Effects 0.000 claims description 66
- VXEGSRKPIUDPQT-UHFFFAOYSA-N 4-[4-(4-methoxyphenyl)piperazin-1-yl]aniline Chemical compound C1=CC(OC)=CC=C1N1CCN(C=2C=CC(N)=CC=2)CC1 VXEGSRKPIUDPQT-UHFFFAOYSA-N 0.000 claims description 63
- 239000005049 silicon tetrachloride Substances 0.000 claims description 63
- MROCJMGDEKINLD-UHFFFAOYSA-N dichlorosilane Chemical compound Cl[SiH2]Cl MROCJMGDEKINLD-UHFFFAOYSA-N 0.000 claims description 47
- 239000007789 gas Substances 0.000 claims description 30
- 229910052710 silicon Inorganic materials 0.000 claims description 22
- 239000010703 silicon Substances 0.000 claims description 22
- 239000001257 hydrogen Substances 0.000 claims description 11
- 229910052739 hydrogen Inorganic materials 0.000 claims description 11
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 claims description 10
- 239000005046 Chlorosilane Substances 0.000 claims description 9
- KOPOQZFJUQMUML-UHFFFAOYSA-N chlorosilane Chemical compound Cl[SiH3] KOPOQZFJUQMUML-UHFFFAOYSA-N 0.000 claims description 9
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 claims description 6
- 229910000041 hydrogen chloride Inorganic materials 0.000 claims description 6
- IXCSERBJSXMMFS-UHFFFAOYSA-N hydrogen chloride Substances Cl.Cl IXCSERBJSXMMFS-UHFFFAOYSA-N 0.000 claims description 6
- 239000012535 impurity Substances 0.000 abstract description 62
- 229910021420 polycrystalline silicon Inorganic materials 0.000 abstract description 22
- 238000000034 method Methods 0.000 abstract description 21
- 239000002994 raw material Substances 0.000 abstract description 10
- LIKFHECYJZWXFJ-UHFFFAOYSA-N dimethyldichlorosilane Chemical compound C[Si](C)(Cl)Cl LIKFHECYJZWXFJ-UHFFFAOYSA-N 0.000 abstract description 3
- 239000007788 liquid Substances 0.000 description 38
- 239000012141 concentrate Substances 0.000 description 31
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 23
- 229910052799 carbon Inorganic materials 0.000 description 23
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 22
- 238000000605 extraction Methods 0.000 description 21
- 238000010992 reflux Methods 0.000 description 16
- 239000000203 mixture Substances 0.000 description 14
- 238000001514 detection method Methods 0.000 description 10
- 238000000926 separation method Methods 0.000 description 8
- 239000012071 phase Substances 0.000 description 7
- 239000006227 byproduct Substances 0.000 description 5
- 238000001816 cooling Methods 0.000 description 5
- 238000007038 hydrochlorination reaction Methods 0.000 description 5
- 239000000126 substance Substances 0.000 description 5
- VSCWAEJMTAWNJL-UHFFFAOYSA-K aluminium trichloride Chemical compound Cl[Al](Cl)Cl VSCWAEJMTAWNJL-UHFFFAOYSA-K 0.000 description 4
- IJOOHPMOJXWVHK-UHFFFAOYSA-N chlorotrimethylsilane Chemical compound C[Si](C)(C)Cl IJOOHPMOJXWVHK-UHFFFAOYSA-N 0.000 description 4
- 230000000052 comparative effect Effects 0.000 description 4
- 238000012790 confirmation Methods 0.000 description 4
- 238000009826 distribution Methods 0.000 description 4
- 238000010438 heat treatment Methods 0.000 description 4
- 238000004458 analytical method Methods 0.000 description 3
- SLLGVCUQYRMELA-UHFFFAOYSA-N chlorosilicon Chemical compound Cl[Si] SLLGVCUQYRMELA-UHFFFAOYSA-N 0.000 description 3
- 239000013078 crystal Substances 0.000 description 3
- 238000010586 diagram Methods 0.000 description 3
- 230000000694 effects Effects 0.000 description 3
- FBAFATDZDUQKNH-UHFFFAOYSA-M iron chloride Chemical compound [Cl-].[Fe] FBAFATDZDUQKNH-UHFFFAOYSA-M 0.000 description 3
- 238000005259 measurement Methods 0.000 description 3
- 229910001510 metal chloride Inorganic materials 0.000 description 3
- 239000004065 semiconductor Substances 0.000 description 3
- 208000033962 Fontaine progeroid syndrome Diseases 0.000 description 2
- 238000005033 Fourier transform infrared spectroscopy Methods 0.000 description 2
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 2
- 229910003902 SiCl 4 Inorganic materials 0.000 description 2
- 230000015572 biosynthetic process Effects 0.000 description 2
- -1 boiling point 42°C) Chemical compound 0.000 description 2
- 238000006243 chemical reaction Methods 0.000 description 2
- 150000008280 chlorinated hydrocarbons Chemical class 0.000 description 2
- 239000000284 extract Substances 0.000 description 2
- 238000002290 gas chromatography-mass spectrometry Methods 0.000 description 2
- 238000011084 recovery Methods 0.000 description 2
- 238000007086 side reaction Methods 0.000 description 2
- 150000004756 silanes Chemical class 0.000 description 2
- FDNAPBUWERUEDA-UHFFFAOYSA-N silicon tetrachloride Chemical compound Cl[Si](Cl)(Cl)Cl FDNAPBUWERUEDA-UHFFFAOYSA-N 0.000 description 2
- CZDYPVPMEAXLPK-UHFFFAOYSA-N tetramethylsilane Chemical compound C[Si](C)(C)C CZDYPVPMEAXLPK-UHFFFAOYSA-N 0.000 description 2
- 239000005051 trimethylchlorosilane Substances 0.000 description 2
- 230000002411 adverse Effects 0.000 description 1
- 229910052782 aluminium Inorganic materials 0.000 description 1
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 1
- 239000007795 chemical reaction product Substances 0.000 description 1
- 229910052801 chlorine Inorganic materials 0.000 description 1
- 125000001309 chloro group Chemical group Cl* 0.000 description 1
- YGZSVWMBUCGDCV-UHFFFAOYSA-N chloro(methyl)silane Chemical class C[SiH2]Cl YGZSVWMBUCGDCV-UHFFFAOYSA-N 0.000 description 1
- 238000004587 chromatography analysis Methods 0.000 description 1
- 150000001875 compounds Chemical class 0.000 description 1
- 239000002826 coolant Substances 0.000 description 1
- 238000000151 deposition Methods 0.000 description 1
- 238000013461 design Methods 0.000 description 1
- BUMGIEFFCMBQDG-UHFFFAOYSA-N dichlorosilicon Chemical compound Cl[Si]Cl BUMGIEFFCMBQDG-UHFFFAOYSA-N 0.000 description 1
- 238000007599 discharging Methods 0.000 description 1
- 238000004993 emission spectroscopy Methods 0.000 description 1
- 238000011156 evaluation Methods 0.000 description 1
- 239000000945 filler Substances 0.000 description 1
- 238000011049 filling Methods 0.000 description 1
- 239000000706 filtrate Substances 0.000 description 1
- 238000004817 gas chromatography Methods 0.000 description 1
- 239000007792 gaseous phase Substances 0.000 description 1
- 229930195733 hydrocarbon Natural products 0.000 description 1
- 150000002430 hydrocarbons Chemical class 0.000 description 1
- 150000002431 hydrogen Chemical class 0.000 description 1
- 238000009616 inductively coupled plasma Methods 0.000 description 1
- 230000002401 inhibitory effect Effects 0.000 description 1
- 229910052742 iron Inorganic materials 0.000 description 1
- RBTARNINKXHZNM-UHFFFAOYSA-K iron trichloride Chemical compound Cl[Fe](Cl)Cl RBTARNINKXHZNM-UHFFFAOYSA-K 0.000 description 1
- 230000002427 irreversible effect Effects 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 229910052751 metal Inorganic materials 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- 229910021421 monocrystalline silicon Inorganic materials 0.000 description 1
- 239000000843 powder Substances 0.000 description 1
- 238000010248 power generation Methods 0.000 description 1
- 238000012545 processing Methods 0.000 description 1
- 239000000047 product Substances 0.000 description 1
- 239000012495 reaction gas Substances 0.000 description 1
- 238000011160 research Methods 0.000 description 1
- 239000007787 solid Substances 0.000 description 1
- 238000001179 sorption measurement Methods 0.000 description 1
- HOHCZXBQTZMSEL-UHFFFAOYSA-N trichlorosilane Chemical compound Cl[SiH](Cl)Cl.Cl[SiH](Cl)Cl HOHCZXBQTZMSEL-UHFFFAOYSA-N 0.000 description 1
- 235000012431 wafers Nutrition 0.000 description 1
Images
Classifications
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B33/00—Silicon; Compounds thereof
- C01B33/08—Compounds containing halogen
- C01B33/107—Halogenated silanes
Definitions
- the present invention relates to a method for producing purified trichlorosilane, and more particularly, to a method for obtaining purified trichlorosilane by purifying crude trichlorosilane containing at least isopentane and methyldichlorosilane by distillation.
- SiHCl 3 high purity trichlorosilane
- SiHCl 3 polycrystalline silicon
- Polycrystalline silicon is used, for example, as a raw material for semiconductor or solar power generation wafers.
- a method for producing trichlorosilane a method is known in which a gas containing hydrogen chloride or silicon tetrachloride and hydrogen is reacted with metallurgical grade silicon.
- a method of subjecting metallurgical grade silicon to a hydrogen chloride-containing gas at 250°C or higher, generally from 250 to 450°C, or a mixed gas of metallurgical grade silicon, silicon tetrachloride, and hydrogen A method of carrying out a hydrochlorination reaction of and at a temperature of 400°C or higher, generally 400 to 600°C, is known.
- trichlorosilane is produced as a by-product by, for example, subjecting metallurgical grade silicon to a hydrochlorination reaction with a mixed gas of chlorinated hydrocarbon and hydrogen.
- Trichlorosilane produced by these methods is free from various side reactions generated by side reactions accompanying the formation of trichlorosilane and by hydrochlorination of carbon impurities contained in the metallurgical grade metal silicon used as the raw material.
- This is crude trichlorosilane containing raw impurities.
- By-product impurities typically include trichlorosilane (which is the target of purification such as dichlorosilane (H 2 SiCl 2 : boiling point 8.4°C), tetramethylsilane (Si(CH 3 ) 4 : boiling point 27°C), etc.
- boiling point means the value under normal pressure (under 1 atmosphere). Therefore, in order to remove by-product impurities contained in such crude trichlorosilane, purification by distillation has conventionally been carried out.
- Patent Document 1 [0028], Patent Document 2 [0007], and FIG. 1).
- JP2018-052765A Japanese Patent Application Publication No. 2014-152093
- distillation purification is a separation method that utilizes the boiling point difference between substances, so if a substance with a small boiling point difference, that is, a by-product impurity contained in the crude trichlorosilane, is classified as the impurity near the boiling point.
- Patent Document 2 describes crude trichlorosilane with a high content of methyldichlorosilane, which is obtained by removing high-boiling impurities such as low-boiling methylchlorosilanes and silicon tetrachloride (FIG. 1 and [0045]). , a chlorine atom redistribution reaction consisting of a specific step is performed to obtain the above-mentioned fraction with a low methyldichlorosilane content. This fraction with a low methyldichlorosilane content is distilled again to obtain trichlorosilane from which methyldichlorosilane has been considerably removed ([0050]).
- the present inventors have continued their intensive research in view of the above problems. As a result, the inventors have found that the above-mentioned problems can be solved by subjecting crude trichlorosilane containing at least isopentane and methyldichlorosilane to a specific two-stage distillation, and have completed the present invention.
- the present invention supplies crude trichlorosilane containing at least isopentane and methyldichlorosilane to a first distillation column, and extracts a low-boiling point fraction whose isopentane concentration is 150 times or more higher than the concentration in the crude trichlorosilane.
- the trichlorosilane with reduced isopentane concentration is extracted from the bottom of the column by distillation purification in a manner that discharges the trichlorosilane, Next, the obtained trichlorosilane with reduced isopentane concentration is supplied to a second distillation column, and a high boiling point fraction whose methyldichlorosilane concentration is 1.5 times or more higher than the concentration in the crude trichlorosilane is discharged.
- This is a method for producing purified trichlorosilane, which is characterized in that purified trichlorosilane with a reduced concentration of methyldichlorosilane is distilled out from the top of the column by distillation purification in a specific manner.
- At least crude trichlorosilane containing isopentane and methyldichlorosilane can be highly reduced in near-boiling impurities that are difficult to separate from these trichlorosilanes, especially isopentane.
- the polycrystalline silicon produced using the purified trichlorosilane as a raw material has an extremely low amount of carbon impurities, making it possible to produce high-purity silicon single crystals as a raw material for manufacturing semiconductor devices. , is extremely useful industrially.
- FIG. 1 is a distillation flow diagram showing a typical embodiment of the method for producing purified trichlorosilane according to the present invention.
- FIG. 2 is a distillation flow diagram showing the method for producing purified trichlorosilane carried out in Comparative Example 1.
- the crude trichlorosilane used to produce purified trichlorosilane contains at least both isopentane and methyldichlorosilane.
- the crude trichlorosilane is obtained by reacting the hydrogen chloride or silicon tetrachloride and a hydrogen-containing gas with metallurgical grade silicon.
- These crude trichlorosilanes are produced by cooling the reaction gas produced by the above reaction to form a condensate, and sending this condensate to a crude trichlorosilane recovery tower to remove impurities with a boiling point higher than silicon tetrachloride, specifically Generally, a metal chloride such as iron chloride is separated and removed.
- crude trichlorosilane obtained by subjecting metallurgical grade silicon to a hydrochlorination reaction with a mixed gas of chlorinated hydrocarbon and hydrogen can also be used satisfactorily.
- Such crude trichlorosilane usually contains 10 to 40% mole of trichlorosilane, preferably 20 to 30% mole.
- crude chlorosilane usually contains 30 to 200 ppb moles of isopentane, more specifically 50 to 100 ppb moles, and 1000 to 20000 ppb moles of methyldichlorosilane, more specifically 6000 to 10000 ppb moles, as impurities. Contains.
- crude trichlorosilane usually contains 0.1 to 10% mole of dichlorosilane, more specifically 0.2 to 2% mole, as a low boiling point impurity.
- silicon tetrachloride is usually contained in an amount of 50 to 89.9% by mole, more specifically 70 to 80% by mole.
- the content of the above-mentioned components means the concentration of the above-mentioned components.
- low-boiling point impurities such as tetramethylsilane
- high-boiling point impurities such as trimethylchlorosilane and dimethyldichlorosilane may also be contained.
- measurements of impurity concentrations of silanes such as methyldichlorosilane, silicon tetrachloride, and dichlorosilane, and isopentane contained in the trichlorosilane refer to values measured using a gas chromatograph.
- crude trichlorosilane containing at least isopentane and methyldichlorosilane is purified by a specific distillation using a combination of a first distillation column and a second distillation column, which will be described later.
- Each distillation column used may be either a tray type distillation column or a packed type distillation column.
- the actual number of stages is not particularly limited, and is, for example, 10 or more and 150 or less, more preferably 20 or more and 100 or less.
- examples of the filler include a Raschig ring and a Lessing ring.
- the distillation column can be operated either batchwise or continuously.
- crude trichlorosilane is first supplied to the first distillation column and purified.
- isopentane among the impurities near the boiling point is removed by distillation.
- the greatest feature of the present invention is that isopentane is removed by distillation in this manner prior to the distillation removal of methyldichlorosilane, which is the other component of the near-boiling impurities.
- the distillative removal of isopentane is carried out in the presence of the methyldichlorosilane.
- the isopentane concentration is particularly preferably 200 times or more and 300 times or less higher than the isopentane concentration in the crude trichlorosilane.
- isopentane has a particularly small difference in boiling point from trichlorosilane among the impurities near the boiling point of trichlorosilane, and also exhibits the property of forming an azeotrope with chlorosilanes. , separation by distillation is particularly difficult. Given this property, if distillation is carried out in the coexistence of methyldichlorosilane as described above, it becomes possible to carry out the removal to a higher degree.
- the isopentane content (isopentane concentration) in crude trichlorosilane is 30 ppb mol or more, more specifically 50 to 100 ppb mol
- the isopentane content is more preferably 20 ppb mol or less. It is also possible to reduce the amount to 10 to 19 ppb mol.
- the boiling point difference between isopentane and trichlorosilane is 4.1°C, and the boiling point difference between methyldichlorosilane and trichlorosilane is 10°C. Further, as described above, the isopentane concentration in the crude trichlorosilane is about 30 to 200 ppb mole, and the methyldichlorosilane concentration in the crude trichlorosilane is about 2000 to 20000 ppb mole, as described above.
- distillation operation it is usually necessary to first perform the distillation operation to remove the components with a large boiling point difference from the target component, and then to remove the components with a small boiling point difference. It will be done.
- a distillation operation is usually performed to remove components with a high content, and then a distillation operation is performed to remove components with a low content.
- a distillation operation it is preferable to perform a distillation operation to remove components with a large content first.
- methyldichlorosilane when distilling crude trichlorosilane to separate isopentane and methyldichlorosilane from the crude trichlorosilane, methyldichlorosilane must be removed first by distillation, both from the viewpoint of boiling point difference and from the viewpoint of content. The isopentane is then removed by distillation.
- the concentration of isopentane in trichlorosilane is obtained as a value that is reduced to a certain extent when analyzed by the gas chromatography.
- the effect of removing carbon impurities derived from isopentane is not actually sufficient, and a phenomenon occurs in which the content of carbon impurities is not sufficiently low in polycrystalline silicon produced using this purified trichlorosilane. That is, when the distillation removal operation of methyldichlorosilane is performed first, the isopentane reduction effect obtained by performing the distillation removal operation of isopentane in the coexistence of methyldichlorosilane cannot be obtained.
- methyldichlorosilane has the effect of inhibiting the formation of an azeotrope between isopentane and the chlorosilanes.
- isopentane exists alone in trichlorosilane in the coexistence of methyldichlorosilane, so if it is distilled off, a higher degree of purification becomes possible.
- the isopentane is believed to form an azeotrope with various silanes including the trichlorosilane.
- the boiling point of the azeotrope of isopentane and trichlorosilane is closer to the boiling point of trichlorosilane than the boiling point of isopentane.
- the low boiling point fraction whose isopentane concentration is 150 times or more higher than the concentration in the crude trichlorosilane is discharged by heating the crude trichlorosilane stored at the bottom and adjusting the distillation conditions as appropriate.
- the above-mentioned low boiling point fraction may be discharged from the top or side of the column.
- the temperature at the top or upper side of the column is set at about 50 to 53°C.
- the first distillation column it is preferable that a part of the distillate from the top of the column is condensed by cooling and refluxed.
- the trichlorosilane with reduced isopentane concentration extracted from the bottom of the column is supplied to the second distillation column and purified.
- the purification in the second distillation column residual methyldichlorosilane among the impurities near the boiling point is removed by distillation.
- distillation purification is carried out in such a manner that a high boiling point fraction in which the concentration of methyldichlorosilane is 1.5 times or more higher than the concentration in the crude trichlorosilane is discharged, and the concentration of methyldichlorosilane is also reduced from the top of the column.
- the purified trichlorosilane is distilled off.
- the concentration of methyldichlorosilane in the high boiling point fraction is 2 to 5 times higher than the concentration in the crude trichlorosilane.
- the high boiling point fraction whose concentration of methyldichlorosilane is 1.5 times or more higher than the concentration in the crude trichlorosilane is discharged from isopentane, which is supplied from the first distillation column and stored at the bottom.
- This may be carried out by heating trichlorosilane whose concentration has been reduced, appropriately setting distillation conditions, and extracting the above-mentioned high-boiling point fraction at the bottom or lower side of the column.
- the temperature at the bottom or lower side of the column is set at about 64 to 67°C.
- this second distillation column as in the case of the first distillation column, it is preferable that a part of the distillate from the top of the column is condensed and refluxed by cooling, and the reflux ratio at that time is: The larger the number, the better the separation efficiency, but it is set appropriately in consideration of productivity.
- the content of methyldichlorosilane (methyldichlorosilane concentration) in the isopentane-reduced trichlorosilane is 1000 ppb mol or more, more specifically 2000 to 20000 ppb. Even if it is molar, it is also possible to reduce the content of the methyldichlorosilane to 100 ppb mole or less, more preferably 50 to 90 ppb mole.
- purified trichlorosilane can be obtained as a clean product with an isopentane content (isopentane concentration) of 20 ppb mol or less and a methyldichlorosilane content (methyldichlorosilane concentration) of 100 ppb mol or less. becomes possible. Moreover, in this purified trichlorosilane, not only the content of detectable isopentane but also the content of difficult-to-detect azeotropes of isopentane and trichlorosilane are extremely low. Therefore, polycrystalline silicon produced using this material has a highly reduced carbon impurity content (carbon concentration).
- the high boiling point fraction discharged from the second distillation column and having a concentration of methyldichlorosilane that is 1.5 times or more higher than the concentration in the crude trichlorosilane is A third distillation column is supplied to the third distillation column, and a high boiling point fraction in which the methyldichlorosilane concentration is higher (preferably 10 times or more) than the concentration in the crude trichlorosilane is discharged again from the third distillation column. It is also possible to perform distillation purification to obtain purified trichlorosilane with a reduced concentration of methyldichlorosilane distilled from the top of the column.
- the purified trichlorosilane obtained in this third distillation column also has the same isopentane content (isopentane concentration) and methyldichlorosilane content (methyldichlorosilane concentration) as the purified trichlorosilane discharged from the top of the second distillation column. It is possible to do so.
- crude trichlorosilane in addition to near-boiling impurities (isopentane and methyldichlorosilane), crude trichlorosilane usually contains dichlorosilane as a low-boiling impurity and silicon tetrachloride as a high-boiling impurity. There is. It is preferable to remove these low-boiling point impurities and high-boiling point impurities to a high degree.
- the crude trichlorosilane is supplied to the first distillation column, that is, before performing a distillation operation to remove near-boiling point impurities.
- the crude trichlorosilane is supplied to the pre-first distillation column, and purified by distillation in a manner that discharges a high boiling point fraction in which the silicon tetrachloride concentration is 1.1 times or more higher than the concentration in the crude trichlorosilane.
- Crude trichlorosilane with reduced silicon tetrachloride concentration is distilled from the top, Next, the obtained crude trichlorosilane with a reduced silicon tetrachloride concentration is supplied to a pre-second distillation column, and a low boiling point fraction whose dichlorosilane concentration is 100 times or more higher than the concentration in the crude trichlorosilane is discharged. Crude trichlorosilane with reduced dichlorosilane concentration is extracted from the bottom of the column and supplied to the first distillation column. This will be implemented by In this specification, the crude trichlorosilane with reduced dichlorosilane concentration extracted from the bottom of the pre-second distillation column is also referred to as pre-purified trichlorosilane.
- silicon tetrachloride which is a high-boiling point impurity and has a high content (high concentration) in the crude trichlorosilane
- distillation purification is performed in such a manner that a high boiling point fraction in which the silicon tetrachloride concentration is 1.1 times or more higher than the concentration in the crude trichlorosilane is discharged, and the silicon tetrachloride concentration is reduced from the top of the column. Distill the trichlorosilane.
- the silicon tetrachloride concentration in the high boiling point fraction is 1.2 to 2 times higher than the concentration in the crude trichlorosilane.
- the high boiling point fraction whose silicon tetrachloride concentration is 1.1 times or more higher than the concentration in the crude trichlorosilane is discharged by heating the crude trichlorosilane stored at the bottom,
- the distillation may be carried out by appropriately setting distillation conditions and extracting the above-mentioned high boiling point fraction from the bottom or lower side of the column.
- the temperature at the bottom or lower side of the column is set at about 90 to 93°C.
- the high boiling point fraction may contain solid content such as unreacted silicon fine powder.
- this pre-first distillation column as in the case of the first distillation column, it is preferable that a part of the distillate from the top of the column is condensed and refluxed by cooling, and the reflux ratio at that time is , the larger the separation efficiency, the better the separation efficiency, but it is set appropriately in consideration of productivity.
- the content of silicon tetrachloride (silicon tetrachloride concentration) in the crude trichlorosilane was 50% mole or more, more specifically 50 to 89.9% mole. However, it is also possible to reduce the content (concentration) to 0.1% mole or less, more preferably 10 ppm mole or less (TCD detection limit value).
- the subsequent purification in the pre-second distillation column involves distillation removal of dichlorosilane, which is a low-boiling point impurity and has a relatively large content (relatively high concentration) in the crude trichlorosilane.
- distillation purification is performed in such a manner that a low boiling point fraction with a dichlorosilane concentration 100 times or more higher than the concentration in the crude trichlorosilane is discharged, and trichlorosilane with a reduced dichlorosilane concentration is extracted from the bottom of the column. Pull it out.
- the dichlorosilane concentration in the low boiling point fraction is 100 to 200 times higher than the concentration in the crude trichlorosilane.
- the low boiling point fraction whose dichlorosilane concentration is 100 times or more higher than the concentration in the crude trichlorosilane is discharged by heating the silicon tetrachloride-reduced trichlorosilane stored at the bottom.
- the distillation may be carried out by appropriately setting distillation conditions and discharging the above-mentioned low boiling point fraction from the top or upper side of the column.
- the temperature at the top or upper side of the column is set at about 40 to 43°C.
- this pre-second distillation column as in the case of the first distillation column, it is preferable that a part of the distillate from the top of the column is condensed and refluxed by cooling, and the reflux ratio at that time is , the larger the separation efficiency, the better the separation efficiency, but it is set appropriately in consideration of productivity.
- the content of dichlorosilane (dichlorosilane concentration) in trichlorosilane with reduced silicon tetrachloride concentration is 0.1% mole or more, more specifically 0.2%. Even if it is ⁇ 2% mole, it is possible to reduce its content (concentration) to less than 0.1% mole, more preferably to 10 ppm mole or less (TCD detection limit value).
- trichlorosilane with a reduced dichlorosilane concentration extracted from the bottom of the pre-second distillation column that is, pre-purified trichlorosilane is obtained.
- the contents (concentrations) of silicon tetrachloride and dichlorosilane are both at a clean level of 10 ppm mol (TCD detection limit value) or less, and this is supplied to the first distillation column. becomes possible. Therefore, in pre-purified trichlorosilane, the trichlorosilane content (trichlorosilane concentration) is preferably 99% mole or more, more preferably 99.5% mole or more, and 99.9% mole or more. It is even more preferable.
- the concentration of these near-boiling impurities in crude trichlorosilane containing silicon tetrachloride and dichlorosilane (crude trichlorosilane before pre-purification) and the concentration of these near-boiling impurities in pre-purified trichlorosilane are substantially the same. It is normal that there is. However, if these have changed significantly, the reference concentration of isopentane and methyldichlorosilane before discharge is determined in the removal of these near-boiling impurities, which is performed in combination with the subsequent first distillation column and second distillation column. may be determined based on the concentration in the pre-purified trichlorosilane immediately before the removal treatment.
- the purified trichlorosilane obtained by the method of the present invention is further purified by adsorption and removal, and mixed with trichlorosilane recovered from the exhaust gas after polycrystalline silicon is precipitated using the purified trichlorosilane. Processing may be performed as appropriate.
- FIG. 1 is a distillation flow diagram of an embodiment including pre-purification.
- a liquid flow of crude trichlorosilane produced by reacting a gas containing hydrogen chloride or silicon tetrachloride and hydrogen with metallurgical grade silicon flows through a crude trichlorosilane flow pipe 1. are doing.
- this crude trichlorosilane contains high boiling point impurities such as silicon tetrachloride and low boiling point impurities such as dichlorosilane.
- This crude trichlorosilane is first subjected to pre-purification to remove silicon tetrachloride, which is a high boiling point impurity, and dichlorosilane, which is a low boiling point impurity. That is, the crude trichlorosilane flow pipe 1 is connected to the side of the pre-first distillation column 2, and the crude trichlorosilane liquid stream is supplied to the pre-first distillation column 2. In the pre-first distillation column 2, the crude trichlorosilane liquid stored at the bottom is heated, and distillation and purification thereof is carried out under the conditions described above.
- the bottom liquid corresponding to the high boiling point fraction whose silicon tetrachloride concentration is 1.1 times or more higher than the concentration in the crude trichlorosilane is transferred from the bottom of the column to the silicon tetrachloride concentration column bottom liquid extraction pipe 3.
- a gas phase of trichlorosilane with a reduced silicon tetrachloride concentration is distilled from the top of the column to a silicon tetrachloride-reduced trichlorosilane distillation pipe 4.
- the gas phase of the silicon tetrachloride-reduced trichlorosilane distilled into the silicon-tetrachloride-reduced trichlorosilane distillation pipe 4 is liquefied by the condenser 5, and a part of the liquid stream is transferred to the silicon-tetrachloride-reduced trichlorosilane reflux pipe 6. From there, it is refluxed to the pre-first distillation column 2.
- the other silicon tetrachloride-reduced trichlorosilane supply pipe 7 branched from the silicon tetrachloride-reduced trichlorosilane reflux pipe 6 is connected to the side of the pre-second distillation column 8 .
- the remaining liquid stream of silicon tetrachloride-reduced trichlorosilane refluxed to the pre-first distillation column 2 is supplied to the pre-first distillation column 2.
- the silicon tetrachloride-reduced trichlorosilane liquid stored at the bottom is heated, and its distillation purification is carried out under the conditions described above.
- a gas phase corresponding to a low boiling point fraction in which the dichlorosilane concentration is 100 times or more higher than the concentration in the crude trichlorosilane is distilled from the top of the column to the dichlorosilane concentrate distillation tube 10, and on the other hand, A liquid stream of pre-purified trichlorosilane with a reduced dichlorosilane concentration is extracted from the bottom to a pre-purified trichlorosilane extraction pipe 9 .
- the gas phase of the dichlorosilane concentrate distilled into the dichlorosilane concentrate distillation pipe 10 is liquefied by the condenser 11, and a part of the liquid stream is transferred from the dichlorosilane concentrate reflux pipe 12 to the pre-second distillation It is refluxed to column 8.
- the remaining dichlorosilane concentrate is sent out of the system from the other dichlorosilane concentrate distribution pipe 13 branched from the dichlorosilane concentrate reflux pipe 12.
- isopentane and methyldichlorosilane are removed from the pre-purified trichlorosilane flowing through the pre-purified trichlorosilane extraction pipe 9 from which silicon tetrachloride and dichlorosilane have been removed. . That is, the pre-purified trichlorosilane extraction pipe 9 is connected to the side of the first distillation column 14, and the liquid stream of the pre-purified trichlorosilane is supplied to the first distillation column 14. In the first distillation column 14, the pre-purified trichlorosilane liquid stored at the bottom is heated and distilled and purified under the conditions described above.
- the gas phase of the isopentane concentrate distilled into the isopentane concentrate distillation pipe 16 is liquefied by the condenser 17, and a part of the liquid stream is refluxed from the isopentane concentrate reflux pipe 18 to the first distillation column 14. be done.
- the remaining isopentane concentrate is sent out of the system from the other isopentane concentrate distribution pipe 19 branched from the isopentane concentrate reflux pipe 18.
- the isopentane-reduced trichlorosilane extraction pipe 15 is connected to the side of the second distillation column 20, and the second distillation column 20 is supplied with a liquid stream of the isopentane-reduced trichlorosilane.
- the isopentane-reduced trichlorosilane liquid stored at the bottom is heated and distilled and purified under the conditions described above.
- the bottom liquid corresponding to the high boiling point fraction whose methyldichlorosilane concentration is 1.5 times or more higher than the concentration in the crude trichlorosilane is transferred from the bottom of the column to the methyldichlorosilane concentration column bottom liquid extraction pipe 21.
- a gaseous phase of trichlorosilane with a reduced concentration of methyldichlorosilane is distilled from the top of the column to a purified trichlorosilane distillation tube 22.
- the gas phase of the purified trichlorosilane distilled into the purified trichlorosilane distillation tube 22 is liquefied by the condenser 23, and a part of the liquid stream is refluxed from the purified trichlorosilane reflux tube 24 to the second distillation column 20. be done.
- purified trichlorosilane subjected to the manufacturing method of the present invention is taken out as a residual liquid from the other purified trichlorosilane flow pipe 25 branched from the purified trichlorosilane reflux pipe 24.
- the purified trichlorosilane thus obtained may be usefully used as a raw material for producing polycrystalline silicon.
- Iron chloride (FeCl 3 ), aluminum chloride (AlCl 3 ), organic chlorosilane, and various other organic substances are contained as trace components in the generated gas.
- the composition of the raw materials used was that the metallurgical grade silicon had a silicon concentration of 99% by mass, an iron concentration of 0.7% by mass, an aluminum concentration of 0.3% by mass, and a carbon concentration of 300ppmwt, silicon tetrachloride and hydrogen. The purity was 99% by mass or more.
- the reaction product gas containing trichlorosilane was cooled to a temperature range of 0 to 20°C to obtain a cooled condensate.
- This coolant was sent to a crude trichlorosilane recovery tower to separate metal chlorides such as iron chloride, which have a boiling point higher than silicon tetrachloride, to obtain a crude trichlorosilane liquid.
- the composition of the obtained crude trichlorosilane liquid is as follows: trichlorosilane concentration is 27.2% mole, silicon tetrachloride concentration is 72.3% mole, dichlorosilane concentration is 0.5% mole, methyldichlorosilane concentration is 15000 ppb mole, The isopentane concentration was 85 ppb mole, and the iron chloride concentration and aluminum chloride concentration were each less than 1 ppb-wt.
- Example 1 The crude trichlorosilane liquid was subjected to the distillation flow shown in FIG. 1 and treated.
- each distillation column In the distillation flow shown in FIG. 1, the pre-first distillation column 2 and the pre-second distillation column 8 each had a column diameter of 150 mm and a theoretical plate number of 30.
- the pre-first distillation column 2 was operated under the conditions that the pressure at the bottom of the column was 200 kPa (gauge pressure) and the temperature at the bottom of the column was 91 to 92°C.
- the pre-second distillation column 8 was operated under the conditions that the pressure at the top of the column was 100 kPa (gauge pressure) and the temperature at the top of the column was 41 to 42°C.
- the first distillation column 14 was operated under the conditions that the pressure at the top of the column was 100 kPa (gauge pressure) and the temperature at the top of the column was 51 to 52°C.
- the second distillation column 20 was operated under the conditions that the pressure at the bottom of the column was 200 kPa (gauge pressure) and the temperature at the bottom of the column was 65 to 66°C.
- Pre-first distillation column 2 When we sampled the bottom liquid flowing through the silicon tetrachloride concentration column bottom liquid extraction pipe 3 and analyzed its composition, we found that the silicon tetrachloride concentration was 99.9% molar, and the trichlorosilane concentration was below the detection limit of 10 ppm molar. there were.
- the concentration of silicon tetrachloride in the column bottom liquid is 1.38 times higher than the concentration in the crude trichlorosilane.
- the impurity methyldichlorosilane was removed to a high degree from the trichlorosilane distilled from the filtrate and flowing through the purified trichlorosilane distillation tube 22.
- the composition of the purified trichlorosilane sampled from the purified trichlorosilane flow pipe 25 we found that the trichlorosilane concentration was 99.9% molar, the isopentane concentration was 17 ppb molar, and the methyldichlorosilane concentration was 72 ppb. It was of high molar purity.
- Comparative example 1 Purified trichlorosilane was produced in the same manner as in Example 1, except that the distillation flow of the crude chlorosilane liquid was changed from that shown in FIG. 1 to that shown in FIG. 2.
- the distillation flow of FIG. 2 in the one shown in FIG. 1, crude trichlorosilane (pre-purified trichlorosilane) is distilled, but isopentane concentrate is distilled from the top of the column in the first distillation column 14, and isopentane reduction is distilled from the bottom of the column.
- the process differs in that reduced trichlorosilane is supplied to the first distillation column, and in the first distillation column 14, isopentane concentrate is distilled from the top of the column, and purified trichlorosilane is obtained from the bottom of the column.
- isopentane concentrate is distilled from the top of the column
- purified trichlorosilane is obtained from the bottom of the column.
- the concentration of methyldichlorosilane in the bottom liquid is 2.2 times higher than the concentration in crude trichlorosilane (pre-purified trichlorosilane), and from this, even if methyldichlorosilane is removed first, It was confirmed that methyldichlorosilane was highly removed from the trichlorosilane distilled from the top of the second distillation column 20 and flowing through the methyldichlorosilane-reduced trichlorosilane distillation tube 22.
- Example 1 the distillation of isopentane in the first distillation column 14 is carried out in the presence of methyldichlorosilane, and in this state, the isopentane is also removed as an azeotrope, whereas in Comparative Example 1, the isopentane is removed as an azeotrope.
- the distillation of isopentane in the first distillation column 14 is caused by the fact that most of the methyldichlorosilane is removed in the second distillation column 20, and therefore the azeotrope of isopentane is insufficiently removed.
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Abstract
[Problem] To greatly reduce, in trichlorosilane that serves as a raw material for the production of polycrystalline silicon or the like, the concentration of dimethyldichlorosilane and isopentane, which are impurities having similar boiling points to said trichlorosilane. [Solution] Provided is a method for producing purified trichlorosilane, the method being characterized by, at least: supplying crude trichlorosilane containing isopentane and methyldichlorosilane to a first distillation column; carrying out distillation purification in a manner so as to discharge a low boiling point range fraction in which the concentration of isopentane is at least 150 times higher than the concentration of isopentane in the crude trichlorosilane; removing trichlorosilane having a lowered isopentane concentration from the bottom of the column, then supplying the obtained trichlorosilane having a lowered isopentane concentration to a second distillation column; carrying out distillation purification in a manner so as to discharge a high boiling point range fraction in which the concentration of methyldichlorosilane is at least 1.5 times higher than the concentration of methyldichlorosilane in the crude trichlorosilane; and distilling off purified trichlorosilane having a lowered methyldichlorosilane concentration from the top of the column.
Description
本発明は、精製トリクロロシランの製造方法、詳しくは、少なくとも、イソペンタン及びメチルジクロロシランを含有する粗トリクロロシランを蒸留により精製して、精製トリクロロシランを得る方法に関する。
The present invention relates to a method for producing purified trichlorosilane, and more particularly, to a method for obtaining purified trichlorosilane by purifying crude trichlorosilane containing at least isopentane and methyldichlorosilane by distillation.
従来から、高純度のトリクロロシラン（ＳｉＨＣｌ3）は、多結晶シリコン（Ｓｉ）の製造用原料に使用されている。多結晶シリコンは、例えば半導体または太陽光発電用ウエハの原料として使用される。
Conventionally, high purity trichlorosilane (SiHCl 3 ) has been used as a raw material for producing polycrystalline silicon (Si). Polycrystalline silicon is used, for example, as a raw material for semiconductor or solar power generation wafers.
トリクロロシランの製造方法として、塩化水素、または、四塩化珪素および水素、を含有するガスを、冶金級シリコンと反応させる方法が知られている。具体的には、冶金級シリコンと塩化水素含有ガスとを２５０℃以上、一般には、２５０～４５０℃で水素化塩素化反応させる方法、或いは、冶金級シリコンと、四塩化珪素および水素の混合ガスと、を４００℃以上、一般には、４００～６００℃の温度で水素化塩素化反応させる方法等が知られている。また、トリクロロシランは、冶金級シリコンと、塩素化炭化水素および水素の混合ガスと、を水素化塩素化反応させること等によっても副生することが知られている。
As a method for producing trichlorosilane, a method is known in which a gas containing hydrogen chloride or silicon tetrachloride and hydrogen is reacted with metallurgical grade silicon. Specifically, a method of subjecting metallurgical grade silicon to a hydrogen chloride-containing gas at 250°C or higher, generally from 250 to 450°C, or a mixed gas of metallurgical grade silicon, silicon tetrachloride, and hydrogen. A method of carrying out a hydrochlorination reaction of and at a temperature of 400°C or higher, generally 400 to 600°C, is known. It is also known that trichlorosilane is produced as a by-product by, for example, subjecting metallurgical grade silicon to a hydrochlorination reaction with a mixed gas of chlorinated hydrocarbon and hydrogen.
これらの方法により製造されたトリクロロシランは、前記トリクロロシランの生成に伴う副反応や、原料とされる前記冶金級金属シリコンに含まれる炭素不純物の水素化塩素化による副反応により生成した種々の副生不純物が混入している粗トリクロロシランである。副生不純物としては、代表的には、ジクロロシラン（Ｈ2ＳｉＣｌ2：沸点８．４℃）、テトラメチルシラン（Ｓｉ（ＣＨ3）4：沸点２７℃）等の精製対象であるトリクロロシラン（沸点３１．８℃）より低沸点不純物や、四塩化珪素（ＳｉＣｌ4：沸点５７．７℃）、トリメチルクロルシラン（（ＣＨ3）3ＳｉＣｌ：沸点５７℃）、ジメチルジクロルシラン（（ＣＨ3）2ＳｉＣｌ2：沸点７０℃）等の該トリクロロシランより高沸点不純物、さらにはイソペンタン（ＣＨ3ＣＨ2ＣＨ（ＣＨ3）2：沸点２７．７℃）やメチルジクロロシラン（ＣＨ3ＳｉＨＣｌ2：沸点４２℃）等の該トリクロロシランに対する沸点近接不純物を示すことができる。なお、本願明細書中において、沸点は常圧下（１気圧下）での値を意味する。而して、こうした粗トリクロロシラン中に含まれる副生不純物を除去するために、従来より蒸留による精製が実施されている。（例えば、特許文献１〔００２８〕、特許文献２〔０００７〕及び図１）。
Trichlorosilane produced by these methods is free from various side reactions generated by side reactions accompanying the formation of trichlorosilane and by hydrochlorination of carbon impurities contained in the metallurgical grade metal silicon used as the raw material. This is crude trichlorosilane containing raw impurities. By-product impurities typically include trichlorosilane (which is the target of purification such as dichlorosilane (H 2 SiCl 2 : boiling point 8.4°C), tetramethylsilane (Si(CH 3 ) 4 : boiling point 27°C), etc. Impurities with boiling points lower than 31.8°C (boiling point 31.8°C), silicon tetrachloride (SiCl 4 : boiling point 57.7°C), trimethylchlorosilane ((CH 3 ) 3 SiCl: boiling point 57°C), dimethyldichlorosilane ((CH 3 ) ) 2 SiCl 2 (boiling point 70°C), impurities with a boiling point higher than that of the trichlorosilane, as well as isopentane (CH 3 CH 2 CH (CH 3 ) 2 : boiling point 27.7°C) and methyldichlorosilane (CH 3 SiHCl 2 : Impurities near the boiling point for the trichlorosilane, such as boiling point 42°C), can be shown. In addition, in this specification, boiling point means the value under normal pressure (under 1 atmosphere). Therefore, in order to remove by-product impurities contained in such crude trichlorosilane, purification by distillation has conventionally been carried out. (For example, Patent Document 1 [0028], Patent Document 2 [0007], and FIG. 1).
上記蒸留による精製によれば、前記粗トリクロロシランに含まれる、副生不純物のうち、トリクロロシランに対する沸点差が大きい低沸点不純物や高沸点不純物は、蒸留塔からの留出物や塔底液として、それぞれさほどの困難性なく除去可能である。ところが、言うまでもなく蒸留精製は、物質間の沸点差を利用する分離法であるため、沸点差が小さい物質、即ち、上記粗トリクロロシランに含まれる副生不純物であれば、前記沸点近接不純物として示したものについては、その分離が充分でなくなる（例えば、特許文献１〔００２８〕、特許文献２〔００１２〕。特に、前記イソペンタンは、沸点が前記２７．７℃で、トリクロロシランの沸点３１．８℃に極めて近く、さらにこのものは前記トリクロロシランを始めとしたクロロシラン類と共沸化物を形成する可能性もあり、これを高度に精製することは相当なる困難性があった。
According to the above purification by distillation, among the by-product impurities contained in the crude trichlorosilane, low-boiling point impurities and high-boiling point impurities with a large boiling point difference with respect to trichlorosilane are removed as distillate from the distillation column or bottom liquid. , each can be removed without much difficulty. However, needless to say, distillation purification is a separation method that utilizes the boiling point difference between substances, so if a substance with a small boiling point difference, that is, a by-product impurity contained in the crude trichlorosilane, is classified as the impurity near the boiling point. (For example, Patent Document 1 [0028], Patent Document 2 [0012]. ℃, and there is a possibility that this substance may form an azeotrope with chlorosilanes such as the above-mentioned trichlorosilane, making it extremely difficult to purify it to a high degree.
詳述すれば、前記特許文献２では、低沸点メチルクロロシラン類や四塩化珪素の高沸点不純物を除去して得た（図１及び〔００４５〕）、メチルジクロロシラン含有率が高い粗トリクロロシランについて、特定の工程からなる塩素原子の再分配反応を施して、上記メチルジクロロシラン含有率が低い留分を得ている。そしてこのメチルジクロロシラン含有率が低い留分を再度に蒸留して、該メチルジクロロシランをかなりに除去したトリクロロシランを得ている（〔００５０〕）。この方法において、前記粗トリクロロシラン中に前記イソペンタンが含有されていたかは何も明らかにされていない。この方法では、確かに、前記メチルジクロロシランはある程度に除去可能かもしれないが、仮に、上記イソペンタンが含有されていたならば、このものはほとんどが除去されることなく、得られる精製トリクロロシランに残留する。
Specifically, Patent Document 2 describes crude trichlorosilane with a high content of methyldichlorosilane, which is obtained by removing high-boiling impurities such as low-boiling methylchlorosilanes and silicon tetrachloride (FIG. 1 and [0045]). , a chlorine atom redistribution reaction consisting of a specific step is performed to obtain the above-mentioned fraction with a low methyldichlorosilane content. This fraction with a low methyldichlorosilane content is distilled again to obtain trichlorosilane from which methyldichlorosilane has been considerably removed ([0050]). In this method, nothing is made clear as to whether the isopentane was contained in the crude trichlorosilane. In this method, it is true that the methyldichlorosilane may be removed to some extent, but if the isopentane was contained, most of it would not be removed and the resulting purified trichlorosilane would contain the isopentane. remain.
近年、半導体デバイスの製造原料となるシリコン単結晶に対しては、電気特性に悪影響を与えるため炭素不純物量は極力低減することが益々に望まれてきている。この背景にあって、上記シリコン単結晶を製造するための多結晶シリコンの製造原料になる、トリクロロシランに対しても、こうした炭素不純物の原因になる炭化水素類の含有量は可能な限り低減させることが求められているが、上記沸点近接不純物、特にイソペンタンが十分に除去できないことは、その達成を困難にしており大きな課題であった。
In recent years, it has become increasingly desirable to reduce the amount of carbon impurities in silicon single crystals, which are the raw material for manufacturing semiconductor devices, as much as possible since they adversely affect the electrical properties. Against this background, the content of hydrocarbons that cause carbon impurities in trichlorosilane, which is the raw material for producing polycrystalline silicon for producing the above-mentioned silicon single crystals, should be reduced as much as possible. However, the inability to sufficiently remove the above-mentioned impurities near the boiling point, especially isopentane, has been a major problem, making it difficult to achieve this goal.
本発明者らは上記課題に鑑み鋭意研究を続けてきた。その結果、少なくとも、イソペンタン及びメチルジクロロシランを含有する粗トリクロロシランを、特定の２段階の蒸留に供することにより、上記の課題が解決することを見出し、本発明を完成するに至った。
The present inventors have continued their intensive research in view of the above problems. As a result, the inventors have found that the above-mentioned problems can be solved by subjecting crude trichlorosilane containing at least isopentane and methyldichlorosilane to a specific two-stage distillation, and have completed the present invention.
即ち、本発明は、少なくとも、イソペンタン及びメチルジクロロシランを含有する粗トリクロロシランを、第１蒸留塔に供給して、イソペンタン濃度が該粗トリクロロシラン中の濃度より１５０倍以上高い低沸点域画分を排出させる態様で蒸留精製して、塔底からイソペンタン濃度が低減されたトリクロロシランを抜き出し、
次いで、得られたイソペンタン濃度が低減されたトリクロロシランを第２蒸留塔に供給して、メチルジクロロシラン濃度が前記粗トリクロロシラン中の濃度より１．５倍以上高い高沸点域画分を排出させる態様で蒸留精製して、塔頂からメチルジクロロシラン濃度が低減された精製トリクロロシランを留出させることを特徴とする、精製トリクロロシランの製造方法である。 That is, the present invention supplies crude trichlorosilane containing at least isopentane and methyldichlorosilane to a first distillation column, and extracts a low-boiling point fraction whose isopentane concentration is 150 times or more higher than the concentration in the crude trichlorosilane. The trichlorosilane with reduced isopentane concentration is extracted from the bottom of the column by distillation purification in a manner that discharges the trichlorosilane,
Next, the obtained trichlorosilane with reduced isopentane concentration is supplied to a second distillation column, and a high boiling point fraction whose methyldichlorosilane concentration is 1.5 times or more higher than the concentration in the crude trichlorosilane is discharged. This is a method for producing purified trichlorosilane, which is characterized in that purified trichlorosilane with a reduced concentration of methyldichlorosilane is distilled out from the top of the column by distillation purification in a specific manner.
次いで、得られたイソペンタン濃度が低減されたトリクロロシランを第２蒸留塔に供給して、メチルジクロロシラン濃度が前記粗トリクロロシラン中の濃度より１．５倍以上高い高沸点域画分を排出させる態様で蒸留精製して、塔頂からメチルジクロロシラン濃度が低減された精製トリクロロシランを留出させることを特徴とする、精製トリクロロシランの製造方法である。 That is, the present invention supplies crude trichlorosilane containing at least isopentane and methyldichlorosilane to a first distillation column, and extracts a low-boiling point fraction whose isopentane concentration is 150 times or more higher than the concentration in the crude trichlorosilane. The trichlorosilane with reduced isopentane concentration is extracted from the bottom of the column by distillation purification in a manner that discharges the trichlorosilane,
Next, the obtained trichlorosilane with reduced isopentane concentration is supplied to a second distillation column, and a high boiling point fraction whose methyldichlorosilane concentration is 1.5 times or more higher than the concentration in the crude trichlorosilane is discharged. This is a method for producing purified trichlorosilane, which is characterized in that purified trichlorosilane with a reduced concentration of methyldichlorosilane is distilled out from the top of the column by distillation purification in a specific manner.
本発明の方法によれば、少なくとも、イソペンタン及びメチルジクロロシランを含有する粗トリクロロシランについて、簡便な方法により、これらトリクロロシランから分離し難い沸点近接不純物、特に、イソペンタンを高度に低減させることができる。その結果、得られた精製トリクロロシランを原料に製造した多結晶シリコンは、炭素不純物量が極めて低いものになり、引いては半導体デバイスの製造原料として高純度なシリコン単結晶の製造も可能になり、産業上極めて有用である。
According to the method of the present invention, at least crude trichlorosilane containing isopentane and methyldichlorosilane can be highly reduced in near-boiling impurities that are difficult to separate from these trichlorosilanes, especially isopentane. . As a result, the polycrystalline silicon produced using the purified trichlorosilane as a raw material has an extremely low amount of carbon impurities, making it possible to produce high-purity silicon single crystals as a raw material for manufacturing semiconductor devices. , is extremely useful industrially.
本発明の方法において、精製トリクロロシランの製造に供する粗トリクロロシランは、少なくとも、イソペンタン及びメチルジクロロシランをともに含有するものである。通常は、該粗トリクロロシランは、前記塩化水素または四塩化珪素と水素を含有するガスを、冶金級シリコンと反応させて得られた、粗トリクロロシランである。
In the method of the present invention, the crude trichlorosilane used to produce purified trichlorosilane contains at least both isopentane and methyldichlorosilane. Usually, the crude trichlorosilane is obtained by reacting the hydrogen chloride or silicon tetrachloride and a hydrogen-containing gas with metallurgical grade silicon.
具体的には、冶金級シリコンと塩化水素含有ガスとを２５０℃以上、一般には、２５０～４５０℃で水素化塩素化反応させる方法、或いは、冶金級シリコンと、四塩化珪素および水素の混合ガスと、を４００℃以上、一般には、４００～６００℃の温度で水素化塩素化反応させる方法等により得られたものが好適である。これらの粗トリクロロシランは、上記反応により生成させた反応ガスを冷却して凝縮液とし、この凝縮液を粗トリクロロシラン回収塔に送液して、四塩化珪素より沸点の高い不純物、具体的には、塩化鉄等の金属塩化物を分離除去したものを用いるのが一般的である。
Specifically, a method of subjecting metallurgical grade silicon to a hydrogen chloride-containing gas at 250°C or higher, generally from 250 to 450°C, or a mixed gas of metallurgical grade silicon, silicon tetrachloride, and hydrogen. and are preferably obtained by a method of subjecting them to a hydrochlorination reaction at a temperature of 400°C or higher, generally from 400 to 600°C. These crude trichlorosilanes are produced by cooling the reaction gas produced by the above reaction to form a condensate, and sending this condensate to a crude trichlorosilane recovery tower to remove impurities with a boiling point higher than silicon tetrachloride, specifically Generally, a metal chloride such as iron chloride is separated and removed.
この他、粗トリクロロシランは、冶金級シリコンと、塩素化炭化水素および水素の混合ガスと、を水素化塩素化反応させることにより得られたもの等も良好に使用可能である。
In addition, crude trichlorosilane obtained by subjecting metallurgical grade silicon to a hydrochlorination reaction with a mixed gas of chlorinated hydrocarbon and hydrogen can also be used satisfactorily.
係る粗トリクロロシランには、通常、トリクロロシランが１０～４０％モル、好適には２０～３０％モル含有されている。一方、粗クロロシランには、不純物として、通常、前記イソペンタンが３０～２００ｐｐｂモル、より詳細には５０～１００ｐｐｂモル含有されており、メチルジクロロシランが１０００～２００００ｐｐｂモル、より詳細には６０００～１００００ｐｐｂモル含有されている。また、粗トリクロロシランには、こうした沸点近接不純物の他に、低沸点不純物として、通常、ジクロロシランが０．１～１０％モル、より詳細には０．２～２％モル含有されており、高沸点不純物として、通常、四塩化珪素が５０～８９．９％モル、より詳細には７０～８０％モル含有されている。なお、上記の成分の含有量は、上記の成分の濃度を意味する。さらに、低沸点不純物であるテトラメチルシラン等や、高沸点不純物である、トリメチルクロルシラン、ジメチルジクロルシラン等も含有される場合がある。
Such crude trichlorosilane usually contains 10 to 40% mole of trichlorosilane, preferably 20 to 30% mole. On the other hand, crude chlorosilane usually contains 30 to 200 ppb moles of isopentane, more specifically 50 to 100 ppb moles, and 1000 to 20000 ppb moles of methyldichlorosilane, more specifically 6000 to 10000 ppb moles, as impurities. Contains. In addition to these near-boiling impurities, crude trichlorosilane usually contains 0.1 to 10% mole of dichlorosilane, more specifically 0.2 to 2% mole, as a low boiling point impurity. As a high boiling point impurity, silicon tetrachloride is usually contained in an amount of 50 to 89.9% by mole, more specifically 70 to 80% by mole. In addition, the content of the above-mentioned components means the concentration of the above-mentioned components. Furthermore, low-boiling point impurities such as tetramethylsilane, and high-boiling point impurities such as trimethylchlorosilane and dimethyldichlorosilane may also be contained.
なお、本願明細書中において、上記トリクロロシラン中に含まれる、メチルジクロロシラン、四塩化珪素、ジクロロシラン等のシラン類や、イソペンタンの各不純物濃度の測定は、ガスクロマトグラフにより測定した値をいう。
In the present specification, measurements of impurity concentrations of silanes such as methyldichlorosilane, silicon tetrachloride, and dichlorosilane, and isopentane contained in the trichlorosilane refer to values measured using a gas chromatograph.
本発明の方法では、斯様にイソペンタン及びメチルジクロロシランを少なくとも含有する粗トリクロロシランを、後述する第１蒸留塔と第２蒸留塔とを組合せた、特定の蒸留により精製する。使用する各蒸留塔は、棚段式蒸留塔、充填式蒸留塔のいずれでもよい。棚段式において実段数は、特に限定されるものではなく、例えば、１０段以上１５０段以下であり、より好ましくは２０段以上１００段以下である。充填式において、充填物としては、例えば、ラシヒリング、レッシングリング等が挙げられる。蒸留塔の運転は、回分式、連続式のいずれでも実施可能である。
In the method of the present invention, crude trichlorosilane containing at least isopentane and methyldichlorosilane is purified by a specific distillation using a combination of a first distillation column and a second distillation column, which will be described later. Each distillation column used may be either a tray type distillation column or a packed type distillation column. In the tray type, the actual number of stages is not particularly limited, and is, for example, 10 or more and 150 or less, more preferably 20 or more and 100 or less. In the filling type, examples of the filler include a Raschig ring and a Lessing ring. The distillation column can be operated either batchwise or continuously.
本発明の方法では、粗トリクロロシランは、まず、第１蒸留塔に供給して精製される。この第１蒸留塔での精製では、前記沸点近接不純物の内のイソペンタンの蒸留除去が施される。本発明の最大の特徴は、斯様にイソペンタンの蒸留除去が、前記沸点近接不純物の内の他方成分である、メチルジクロロシランの蒸留除去に先立って実行されることにある。換言すれば、イソペンタンの蒸留除去が、該メチルジクロロシランの共存下に実行されることにある。これにより第１蒸留塔による蒸留では、イソペンタン濃度が該粗トリクロロシラン中のイソペンタン濃度より１５０倍以上高い低沸点域画分が排出され、塔底からイソペンタン濃度が低減されたトリクロロシランを抜き出すことが可能になる。上記低沸点域画分において、イソペンタン濃度は前記粗トリクロロシラン中のイソペンタン濃度より２００倍以上３００倍以下の範囲で高いことが特に好ましい。
In the method of the present invention, crude trichlorosilane is first supplied to the first distillation column and purified. In the purification in the first distillation column, isopentane among the impurities near the boiling point is removed by distillation. The greatest feature of the present invention is that isopentane is removed by distillation in this manner prior to the distillation removal of methyldichlorosilane, which is the other component of the near-boiling impurities. In other words, the distillative removal of isopentane is carried out in the presence of the methyldichlorosilane. As a result, during distillation in the first distillation column, a low boiling point fraction whose isopentane concentration is 150 times or more higher than the isopentane concentration in the crude trichlorosilane is discharged, and trichlorosilane with a reduced isopentane concentration can be extracted from the bottom of the column. It becomes possible. In the low boiling point fraction, the isopentane concentration is particularly preferably 200 times or more and 300 times or less higher than the isopentane concentration in the crude trichlorosilane.
ここで、イソペンタンは、前記したようにトリクロロシランに対する沸点近接不純物の中でも、格別にその沸点差が、該トリクロロシランに対して小さく、しかも、クロロシラン類と共沸化物を形成する性状も呈しており、蒸留での分離は特に難しい状態にある。この性状にあって、前記の如くにメチルジクロロシランの共存下に蒸留を実施したならば、その除去はより高度に実施することが可能になる。具体的には、粗トリクロロシランにおいて、イソペンタンの含有量（イソペンタン濃度）が３０ｐｐｂモル以上、より詳細には５０～１００ｐｐｂモルであったとしても、該イソペンタンの含有量を２０ｐｐｂモル以下、より好適には１０～１９ｐｐｂモルに低減させることも可能である。
Here, as mentioned above, isopentane has a particularly small difference in boiling point from trichlorosilane among the impurities near the boiling point of trichlorosilane, and also exhibits the property of forming an azeotrope with chlorosilanes. , separation by distillation is particularly difficult. Given this property, if distillation is carried out in the coexistence of methyldichlorosilane as described above, it becomes possible to carry out the removal to a higher degree. Specifically, even if the isopentane content (isopentane concentration) in crude trichlorosilane is 30 ppb mol or more, more specifically 50 to 100 ppb mol, the isopentane content is more preferably 20 ppb mol or less. It is also possible to reduce the amount to 10 to 19 ppb mol.
イソペンタンとトリクロロシランとの沸点差は４．１℃であり、メチルジクロロシランとトリクロロシランとの沸点差は１０℃である。また、粗トリクロロシラン中のイソペンタン濃度は、上述したように、３０～２００ｐｐｂモル程度であり、粗トリクロロシラン中のメチルジクロロシラン濃度は、上述したように、２０００～２００００ｐｐｂモル程度である。
The boiling point difference between isopentane and trichlorosilane is 4.1°C, and the boiling point difference between methyldichlorosilane and trichlorosilane is 10°C. Further, as described above, the isopentane concentration in the crude trichlorosilane is about 30 to 200 ppb mole, and the methyldichlorosilane concentration in the crude trichlorosilane is about 2000 to 20000 ppb mole, as described above.
精製対象成分と、精製対象成分よりも低沸点の成分と、精製対象成分よりも高沸点の成分と、を含む物質を蒸留して、精製対象成分を得る場合、どの成分を先に除去するか（蒸留操作を行う順番）は、除去される成分（低沸点成分および高沸点成分）と精製対象成分との沸点差および除去される成分の含有量が考慮される。
When obtaining a target component by distilling a substance containing a component to be purified, a component with a lower boiling point than the component to be purified, and a component with a higher boiling point than the component to be purified, which component should be removed first? (The order in which the distillation operation is performed) takes into consideration the boiling point difference between the components to be removed (low-boiling components and high-boiling components) and the component to be purified, and the content of the components to be removed.
蒸留操作の効率およびコストを考慮すると、通常、除去される成分のうち、精製対象成分との沸点差が大きい成分を除去する蒸留操作を行ってから、沸点差が小さい成分を除去する蒸留操作が行われる。同様に、通常、除去される成分のうち、含有量の多い成分を除去する蒸留操作を行ってから、含有量が少ない成分を除去する蒸留操作が行われる。特に、塔頂成分と塔底成分とに分離する蒸留塔では、含有量の多い成分を除去する蒸留操作を先に行うことが好ましい。
Considering the efficiency and cost of the distillation operation, it is usually necessary to first perform the distillation operation to remove the components with a large boiling point difference from the target component, and then to remove the components with a small boiling point difference. It will be done. Similarly, among the components to be removed, a distillation operation is usually performed to remove components with a high content, and then a distillation operation is performed to remove components with a low content. In particular, in a distillation column that separates into a top component and a bottom component, it is preferable to perform a distillation operation to remove components with a large content first.
したがって、粗トリクロロシランを蒸留して、粗トリクロロシランから、イソペンタンおよびメチルジクロロシランを分離する場合、沸点差の観点からも、含有量の観点からも、メチルジクロロシランを蒸留操作により先に除去してから、イソペンタンを蒸留操作により除去することになる。
Therefore, when distilling crude trichlorosilane to separate isopentane and methyldichlorosilane from the crude trichlorosilane, methyldichlorosilane must be removed first by distillation, both from the viewpoint of boiling point difference and from the viewpoint of content. The isopentane is then removed by distillation.
しかしながら、先にメチルジクロロシランを蒸留除去してから、係るイソペンタンの蒸留除去操作を施した場合、トリクロロシラン中のイソペンタン濃度は前記ガスクロマトグラフによる分析ではある程度に低減した値として得られる。ところが、該イソペンタンに由来する炭素不純物の除去効果は実際には十分ではなく、この精製トリクロロシランを用いて製造した多結晶シリコンでは炭素不純物の含有量が十分な低さにならない現象が発生する。すなわち、先にメチルジクロロシランの蒸留除去操作を行う場合、上記のイソペンタンをメチルジクロロシランの共存下で蒸留除去操作を行うことにより得られるイソペンタン低減効果が得られない。
However, if methyldichlorosilane is first removed by distillation and then the isopentane is removed by distillation, the concentration of isopentane in trichlorosilane is obtained as a value that is reduced to a certain extent when analyzed by the gas chromatography. However, the effect of removing carbon impurities derived from isopentane is not actually sufficient, and a phenomenon occurs in which the content of carbon impurities is not sufficiently low in polycrystalline silicon produced using this purified trichlorosilane. That is, when the distillation removal operation of methyldichlorosilane is performed first, the isopentane reduction effect obtained by performing the distillation removal operation of isopentane in the coexistence of methyldichlorosilane cannot be obtained.
その理由は、必ずしも定かではないが、本発明者らは、メチルジクロロシランが、イソペンタンと前記クロロシラン類との共沸化物の形成を阻害する作用を有するためではないかと推察している。つまり、該メチルジクロロシランの共存下であれば、イソペンタンは単独でトリクロロシラン中に存在するので、それを留去すれば、より高度な精製が可能になる。他方で、当該メチルジクロロシランが先に除去されている場合には、該イソペンタンは前記トリクロロシランを始めとした種々シラン類と共沸化物を形成すると考えられる。このうちイソペンタンとトリクロロシランとの共沸化物は、その沸点が、イソペンタンの沸点よりもトリクロロシランの沸点にさらに近似する。
The reason for this is not necessarily certain, but the present inventors speculate that it is because methyldichlorosilane has the effect of inhibiting the formation of an azeotrope between isopentane and the chlorosilanes. In other words, isopentane exists alone in trichlorosilane in the coexistence of methyldichlorosilane, so if it is distilled off, a higher degree of purification becomes possible. On the other hand, if the methyldichlorosilane is removed first, the isopentane is believed to form an azeotrope with various silanes including the trichlorosilane. Among these, the boiling point of the azeotrope of isopentane and trichlorosilane is closer to the boiling point of trichlorosilane than the boiling point of isopentane.
ここで、通常、トリクロロシランの純度測定で採用されているガスクロマトグラフによる分析等では、このような共沸化物を検出することは困難である。したがって、たとえガスクロマトグラフによる分析等によりイソペンタン濃度としては相当に低減された精製トリクロロシランと判断されたとしても、実際にはイソペンタンは該共沸化物の形態でその多くが残存していると考えられる。斯くしてこの精製トリクロロシランを用いて多結晶シリコンを製造しても、得られた多結晶シリコンには、イソペンタン共沸化物由来の炭素不純物が多く含まれ、炭素含有量（炭素濃度）が十分に低減できない結果が引き起こされる。
Here, it is difficult to detect such an azeotrope using gas chromatograph analysis, which is normally used to measure the purity of trichlorosilane. Therefore, even if it is determined to be purified trichlorosilane with a considerably reduced isopentane concentration through gas chromatographic analysis, it is thought that in reality, much of the isopentane remains in the form of the azeotrope. . Even if polycrystalline silicon is produced using this purified trichlorosilane, the resulting polycrystalline silicon contains many carbon impurities derived from isopentane azeotrope, and the carbon content (carbon concentration) is insufficient. causes irreversible consequences.
これは、上述したように、トリクロロシランの純度測定で用いられるガスクロマトグラフのカラムでは、イソペンタンは検出できるものの、イソペンタン共沸化物を検出することは困難である。したがって、精製トリクロロシランに含まれる、検出されなかったイソペンタン共沸化物が、該精製トリクロロシランを用いて多結晶シリコンを製造する工程において炭素に転換され、多結晶シリコン中の炭素不純物として検出されるためであると考えられる。
This is because, as mentioned above, although isopentane can be detected with the gas chromatograph column used to measure the purity of trichlorosilane, it is difficult to detect isopentane azeotrope. Therefore, the undetected isopentane azeotrope contained in purified trichlorosilane is converted to carbon in the process of producing polycrystalline silicon using the purified trichlorosilane, and is detected as a carbon impurity in polycrystalline silicon. This is thought to be due to the
第１蒸留塔での蒸留において、前記イソペンタン濃度が該粗トリクロロシラン中の濃度より１５０倍以上高い低沸点域画分の排出は、底部に貯留される粗トリクロロシランを加熱し、蒸留条件を適宜に設定して、塔内の塔頂または側部上方において、上記低沸点域画分を排出させて実施すれば良い。たとえば、塔頂部または側部上方部の温度は５０～５３℃程度に設定される。
During distillation in the first distillation column, the low boiling point fraction whose isopentane concentration is 150 times or more higher than the concentration in the crude trichlorosilane is discharged by heating the crude trichlorosilane stored at the bottom and adjusting the distillation conditions as appropriate. The above-mentioned low boiling point fraction may be discharged from the top or side of the column. For example, the temperature at the top or upper side of the column is set at about 50 to 53°C.
また、第１蒸留塔では、塔頂からの留出物の一部は冷却により凝縮させて還流させるのが好ましく、その際の還流比は、大きい方が分離効率が良くなるが、生産性を考慮して適宜設定される。
In addition, in the first distillation column, it is preferable that a part of the distillate from the top of the column is condensed by cooling and refluxed.The larger the reflux ratio is, the better the separation efficiency will be, but the productivity will be reduced. It will be set as appropriate.
次いで、前記第１蒸留塔において、塔底から抜き出されたイソペンタン濃度が低減されたトリクロロシランは、第２蒸留塔に供給され精製される。この第２蒸留塔での精製では、前記沸点近接不純物の内の残余のメチルジクロロシランの蒸留除去が施される。具体的には、メチルジクロロシラン濃度が前記粗トリクロロシラン中の濃度より１．５倍以上高い高沸点域画分を排出させる態様で蒸留精製を実行し、塔頂からメチルジクロロシラン濃度も低減された精製トリクロロシランを留出させる。ここで、上記高沸点域画分においてメチルジクロロシラン濃度は、前記粗トリクロロシラン中の濃度より２～５倍高いのが特に好ましい態様になる。
Next, in the first distillation column, the trichlorosilane with reduced isopentane concentration extracted from the bottom of the column is supplied to the second distillation column and purified. In the purification in the second distillation column, residual methyldichlorosilane among the impurities near the boiling point is removed by distillation. Specifically, distillation purification is carried out in such a manner that a high boiling point fraction in which the concentration of methyldichlorosilane is 1.5 times or more higher than the concentration in the crude trichlorosilane is discharged, and the concentration of methyldichlorosilane is also reduced from the top of the column. The purified trichlorosilane is distilled off. Here, in a particularly preferred embodiment, the concentration of methyldichlorosilane in the high boiling point fraction is 2 to 5 times higher than the concentration in the crude trichlorosilane.
第２蒸留塔での蒸留において、前記メチルジクロロシラン濃度が粗トリクロロシラン中の濃度より１．５倍以上高い高沸点域画分の排出は、第１蒸留塔から供給され底部に貯留されるイソペンタン濃度が低減されたトリクロロシランを加熱し、蒸留条件を適宜に設定して、塔内の底部または側部下方において、上記高沸点域画分を抜き出すことにより実施すれば良い。たとえば、塔底部または側部下方部の温度は６４～６７℃程度に設定される。
In the distillation in the second distillation column, the high boiling point fraction whose concentration of methyldichlorosilane is 1.5 times or more higher than the concentration in the crude trichlorosilane is discharged from isopentane, which is supplied from the first distillation column and stored at the bottom. This may be carried out by heating trichlorosilane whose concentration has been reduced, appropriately setting distillation conditions, and extracting the above-mentioned high-boiling point fraction at the bottom or lower side of the column. For example, the temperature at the bottom or lower side of the column is set at about 64 to 67°C.
なお、この第２蒸留塔でも、前記第１蒸留塔での場合と同様に、塔頂からの留出物の一部は冷却により凝縮させて還流させるのが好ましく、その際の還流比は、大きい方が分離効率が良くなるが、生産性を考慮して適宜設定される。
In addition, in this second distillation column, as in the case of the first distillation column, it is preferable that a part of the distillate from the top of the column is condensed and refluxed by cooling, and the reflux ratio at that time is: The larger the number, the better the separation efficiency, but it is set appropriately in consideration of productivity.
上記第２蒸留塔でのメチルジクロロシランの除去は、具体的には、前記イソペンタン低減トリクロロシランにおいて、メチルジクロロシランの含有量（メチルジクロロシラン濃度）が１０００ｐｐｂモル以上、より詳細には２０００～２００００ｐｐｂモルであったとしても、該メチルジクロロシランの含有量を１００ｐｐｂモル以下、より好適には５０～９０ｐｐｂモルに低減させることも可能である。斯くして本発明によれば、精製トリクロロシランを、イソペンタン含有量（イソペンタン濃度）が２０ｐｐｂモル以下、及びメチルジクロロシラン含有量（メチルジクロロシラン濃度）が、１００ｐｐｂモル以下に清浄なものとして得ることが可能になる。また、この精製トリクロロシランでは、検出可能なイソペンタンの含有量だけでなく、検出困難なイソペンタンとトリクロロシランとの共沸化物等の含有量も極めて少ない。そのためこれを用いて製造した多結晶シリコンは、炭素不純物含有量（炭素濃度）が高度に低減されたものとして得られる。
Specifically, in the removal of methyldichlorosilane in the second distillation column, the content of methyldichlorosilane (methyldichlorosilane concentration) in the isopentane-reduced trichlorosilane is 1000 ppb mol or more, more specifically 2000 to 20000 ppb. Even if it is molar, it is also possible to reduce the content of the methyldichlorosilane to 100 ppb mole or less, more preferably 50 to 90 ppb mole. Thus, according to the present invention, purified trichlorosilane can be obtained as a clean product with an isopentane content (isopentane concentration) of 20 ppb mol or less and a methyldichlorosilane content (methyldichlorosilane concentration) of 100 ppb mol or less. becomes possible. Moreover, in this purified trichlorosilane, not only the content of detectable isopentane but also the content of difficult-to-detect azeotropes of isopentane and trichlorosilane are extremely low. Therefore, polycrystalline silicon produced using this material has a highly reduced carbon impurity content (carbon concentration).
なお、上記第２蒸留塔での蒸留において、該第２蒸留塔から排出された、メチルジクロロシラン濃度が前記粗トリクロロシラン中の濃度より１．５倍以上高い高沸点域画分は、これを第３蒸留塔に供給して、この第３蒸留塔で再度に、前記メチルジクロロシラン濃度が粗トリクロロシラン中の濃度より高い（好適には１０倍以上）高沸点域画分を排出させる態様で蒸留精製を施し、塔頂から留出させたメチルジクロロシラン濃度が低減された精製トリクロロシランを得る等しても良い。この第３蒸留塔で得られる精製トリクロロシランも、前記第２蒸留塔の塔頂より排出される精製トリクロロシランと同等のイソペンタン含有量（イソペンタン濃度）及びメチルジクロロシラン含有量（メチルジクロロシラン濃度）とすることが可能である。
In addition, in the distillation in the second distillation column, the high boiling point fraction discharged from the second distillation column and having a concentration of methyldichlorosilane that is 1.5 times or more higher than the concentration in the crude trichlorosilane is A third distillation column is supplied to the third distillation column, and a high boiling point fraction in which the methyldichlorosilane concentration is higher (preferably 10 times or more) than the concentration in the crude trichlorosilane is discharged again from the third distillation column. It is also possible to perform distillation purification to obtain purified trichlorosilane with a reduced concentration of methyldichlorosilane distilled from the top of the column. The purified trichlorosilane obtained in this third distillation column also has the same isopentane content (isopentane concentration) and methyldichlorosilane content (methyldichlorosilane concentration) as the purified trichlorosilane discharged from the top of the second distillation column. It is possible to do so.
前記したように粗トリクロロシランには、沸点近接不純物（イソペンタン及びメチルジクロロシラン）の他に、通常は、低沸点不純物としてジクロロシランが含有され、さらには高沸点不純物として四塩化珪素が含有されている。これら低沸点不純物及び高沸点不純物も高度に除去することが好ましい。これら低沸点不純物及び高沸点不純物を高度に除去するために、本実施形態では、前記粗トリクロロシランを第１蒸留塔に供給する前に、すなわち、沸点近接不純物を除去する蒸留操作を行う前に、下記プレ精製を施すのが望ましい。
即ち、〔プレ精製〕は、
前記粗トリクロロシランをプレ第１蒸留塔に供給して、四塩化珪素濃度が前記粗トリクロロシラン中の濃度より１．１倍以上高い高沸点域画分を排出させる態様で蒸留精製して、塔頂から四塩化珪素濃度が低減された粗トリクロロシランを留出させ、
次いで、得られた四塩化珪素濃度が低減された粗トリクロロシランをプレ第２蒸留塔に供給して、ジクロロシラン濃度が前記粗トリクロロシラン中の濃度より１００倍以上高い低沸点域画分を排出させる態様で蒸留精製して、塔底からジクロロシラン濃度が低減された粗トリクロロシランを抜き出して前記第１蒸留塔に供給する、
ことにより実施される。本明細書では、プレ第２蒸留塔の塔底から抜き出された、ジクロロシラン濃度が低減された粗トリクロロシランをプレ精製トリクロロシランともいう。 As mentioned above, in addition to near-boiling impurities (isopentane and methyldichlorosilane), crude trichlorosilane usually contains dichlorosilane as a low-boiling impurity and silicon tetrachloride as a high-boiling impurity. There is. It is preferable to remove these low-boiling point impurities and high-boiling point impurities to a high degree. In order to highly remove these low-boiling point impurities and high-boiling point impurities, in this embodiment, before the crude trichlorosilane is supplied to the first distillation column, that is, before performing a distillation operation to remove near-boiling point impurities. , it is desirable to perform the following pre-purification.
That is, [pre-purification] is
The crude trichlorosilane is supplied to the pre-first distillation column, and purified by distillation in a manner that discharges a high boiling point fraction in which the silicon tetrachloride concentration is 1.1 times or more higher than the concentration in the crude trichlorosilane. Crude trichlorosilane with reduced silicon tetrachloride concentration is distilled from the top,
Next, the obtained crude trichlorosilane with a reduced silicon tetrachloride concentration is supplied to a pre-second distillation column, and a low boiling point fraction whose dichlorosilane concentration is 100 times or more higher than the concentration in the crude trichlorosilane is discharged. Crude trichlorosilane with reduced dichlorosilane concentration is extracted from the bottom of the column and supplied to the first distillation column.
This will be implemented by In this specification, the crude trichlorosilane with reduced dichlorosilane concentration extracted from the bottom of the pre-second distillation column is also referred to as pre-purified trichlorosilane.
即ち、〔プレ精製〕は、
前記粗トリクロロシランをプレ第１蒸留塔に供給して、四塩化珪素濃度が前記粗トリクロロシラン中の濃度より１．１倍以上高い高沸点域画分を排出させる態様で蒸留精製して、塔頂から四塩化珪素濃度が低減された粗トリクロロシランを留出させ、
次いで、得られた四塩化珪素濃度が低減された粗トリクロロシランをプレ第２蒸留塔に供給して、ジクロロシラン濃度が前記粗トリクロロシラン中の濃度より１００倍以上高い低沸点域画分を排出させる態様で蒸留精製して、塔底からジクロロシラン濃度が低減された粗トリクロロシランを抜き出して前記第１蒸留塔に供給する、
ことにより実施される。本明細書では、プレ第２蒸留塔の塔底から抜き出された、ジクロロシラン濃度が低減された粗トリクロロシランをプレ精製トリクロロシランともいう。 As mentioned above, in addition to near-boiling impurities (isopentane and methyldichlorosilane), crude trichlorosilane usually contains dichlorosilane as a low-boiling impurity and silicon tetrachloride as a high-boiling impurity. There is. It is preferable to remove these low-boiling point impurities and high-boiling point impurities to a high degree. In order to highly remove these low-boiling point impurities and high-boiling point impurities, in this embodiment, before the crude trichlorosilane is supplied to the first distillation column, that is, before performing a distillation operation to remove near-boiling point impurities. , it is desirable to perform the following pre-purification.
That is, [pre-purification] is
The crude trichlorosilane is supplied to the pre-first distillation column, and purified by distillation in a manner that discharges a high boiling point fraction in which the silicon tetrachloride concentration is 1.1 times or more higher than the concentration in the crude trichlorosilane. Crude trichlorosilane with reduced silicon tetrachloride concentration is distilled from the top,
Next, the obtained crude trichlorosilane with a reduced silicon tetrachloride concentration is supplied to a pre-second distillation column, and a low boiling point fraction whose dichlorosilane concentration is 100 times or more higher than the concentration in the crude trichlorosilane is discharged. Crude trichlorosilane with reduced dichlorosilane concentration is extracted from the bottom of the column and supplied to the first distillation column.
This will be implemented by In this specification, the crude trichlorosilane with reduced dichlorosilane concentration extracted from the bottom of the pre-second distillation column is also referred to as pre-purified trichlorosilane.
上記プレ精製において、プレ第１蒸留塔での精製では、高沸点不純物であり、粗トリクロロシラン中の含有量が多い（濃度が高い）四塩化珪素の蒸留除去が施される。具体的には、四塩化珪素濃度が前記粗トリクロロシラン中の濃度より１．１倍以上高い高沸点域画分を排出させる態様で蒸留精製を実行し、塔頂から四塩化珪素濃度が低減されたトリクロロシランを留出させる。ここで、上記高沸点域画分において四塩化珪素濃度は、前記粗トリクロロシラン中の濃度より１．２～２倍高いのが特に好ましい態様になる。
In the above pre-purification, in the pre-first distillation column, silicon tetrachloride, which is a high-boiling point impurity and has a high content (high concentration) in the crude trichlorosilane, is removed by distillation. Specifically, distillation purification is performed in such a manner that a high boiling point fraction in which the silicon tetrachloride concentration is 1.1 times or more higher than the concentration in the crude trichlorosilane is discharged, and the silicon tetrachloride concentration is reduced from the top of the column. Distill the trichlorosilane. Here, in a particularly preferred embodiment, the silicon tetrachloride concentration in the high boiling point fraction is 1.2 to 2 times higher than the concentration in the crude trichlorosilane.
プレ第１蒸留塔での蒸留において、前記四塩化珪素濃度が粗トリクロロシラン中の濃度より１．１倍以上高い高沸点域画分の排出は、底部に貯留される粗トリクロロシランを加熱し、蒸留条件を適宜に設定して、塔内の底部または側部下方において、上記高沸点域画分を抜き出すことにより実施すれば良い。たとえば、塔底部または側部下方部の温度は９０～９３℃程度に設定される。また、高沸点域画分には、未反応のシリコン微粉等の固形分が含まれていてもよい。
In the distillation in the pre-first distillation column, the high boiling point fraction whose silicon tetrachloride concentration is 1.1 times or more higher than the concentration in the crude trichlorosilane is discharged by heating the crude trichlorosilane stored at the bottom, The distillation may be carried out by appropriately setting distillation conditions and extracting the above-mentioned high boiling point fraction from the bottom or lower side of the column. For example, the temperature at the bottom or lower side of the column is set at about 90 to 93°C. Further, the high boiling point fraction may contain solid content such as unreacted silicon fine powder.
なお、このプレ第１蒸留塔でも、前記第１蒸留塔での場合と同様に、塔頂からの留出物の一部は冷却により凝縮させて還流させるのが好ましく、その際の還流比は、大きい方が分離効率が良くなるが、生産性を考慮して適宜設定される。
In addition, in this pre-first distillation column, as in the case of the first distillation column, it is preferable that a part of the distillate from the top of the column is condensed and refluxed by cooling, and the reflux ratio at that time is , the larger the separation efficiency, the better the separation efficiency, but it is set appropriately in consideration of productivity.
係るプレ第１蒸留塔の蒸留精製によれば、粗トリクロロシランにおいて、四塩化珪素の含有量（四塩化珪素濃度）が５０％モル以上、より詳細には５０～８９．９％モルであったとしても、その含有量（濃度）を０．１％モル以下、より好適には１０ｐｐｍモル（ＴＣＤ検出限界値）以下に低減させることも可能である。
According to the distillation purification in the pre-first distillation column, the content of silicon tetrachloride (silicon tetrachloride concentration) in the crude trichlorosilane was 50% mole or more, more specifically 50 to 89.9% mole. However, it is also possible to reduce the content (concentration) to 0.1% mole or less, more preferably 10 ppm mole or less (TCD detection limit value).
前記プレ精製において、続くプレ第２蒸留塔での精製では、低沸点不純物であり、粗トリクロロシラン中の含有量が比較的多い（濃度が比較的高い）ジクロロシランの蒸留除去が施される。具体的には、ジクロロシラン濃度が該粗トリクロロシラン中の濃度より１００倍以上高い低沸点域画分を排出させる態様で蒸留精製を実行し、塔底からジクロロシラン濃度が低減されたトリクロロシランを抜き出す。ここで、上記低沸点域画分においてジクロロシラン濃度は、前記粗トリクロロシラン中の濃度より１００～２００倍高いのが特に好ましい態様になる。
In the pre-purification, the subsequent purification in the pre-second distillation column involves distillation removal of dichlorosilane, which is a low-boiling point impurity and has a relatively large content (relatively high concentration) in the crude trichlorosilane. Specifically, distillation purification is performed in such a manner that a low boiling point fraction with a dichlorosilane concentration 100 times or more higher than the concentration in the crude trichlorosilane is discharged, and trichlorosilane with a reduced dichlorosilane concentration is extracted from the bottom of the column. Pull it out. Here, in a particularly preferred embodiment, the dichlorosilane concentration in the low boiling point fraction is 100 to 200 times higher than the concentration in the crude trichlorosilane.
プレ第２蒸留塔での蒸留において、前記ジクロロシラン濃度が該粗トリクロロシラン中の濃度より１００倍以上高い低沸点域画分の排出は、底部に貯留される四塩化珪素低減トリクロロシランを加熱し、蒸留条件を適宜に設定して、塔内の塔頂または側部上方において、上記低沸点域画分を排出させて実施すれば良い。たとえば、塔頂部または側部上方部の温度は４０～４３℃程度に設定される。
In the distillation in the pre-second distillation column, the low boiling point fraction whose dichlorosilane concentration is 100 times or more higher than the concentration in the crude trichlorosilane is discharged by heating the silicon tetrachloride-reduced trichlorosilane stored at the bottom. The distillation may be carried out by appropriately setting distillation conditions and discharging the above-mentioned low boiling point fraction from the top or upper side of the column. For example, the temperature at the top or upper side of the column is set at about 40 to 43°C.
なお、このプレ第２蒸留塔でも、前記第１蒸留塔での場合と同様に、塔頂からの留出物の一部は冷却により凝縮させて還流させるのが好ましく、その際の還流比は、大きい方が分離効率が良くなるが、生産性を考慮して適宜設定される。
In addition, in this pre-second distillation column, as in the case of the first distillation column, it is preferable that a part of the distillate from the top of the column is condensed and refluxed by cooling, and the reflux ratio at that time is , the larger the separation efficiency, the better the separation efficiency, but it is set appropriately in consideration of productivity.
係るプレ第２蒸留塔の蒸留精製によれば、四塩化珪素濃度が低減されたトリクロロシランにおいて、ジクロロシランの含有量（ジクロロシラン濃度）が０．１％モル以上、より詳細には０．２～２％モルであったとしても、その含有量（濃度）を０．１％モル未満、より好適には１０ｐｐｍモル（ＴＣＤ検出限界値）以下に低減させることも可能である。斯くしてプレ精製によれば、プレ第２蒸留塔の塔底から抜き出された、ジクロロシラン濃度が低減されたトリクロロシラン、すなわち、プレ精製トリクロロシランが得られる。このプレ精製トリクロロシランでは、四塩化珪素及びジクロロシランの各含有量（各濃度）が、ともに１０ｐｐｍモル（ＴＣＤ検出限界値）以下の清浄なレベルであり、これを第１蒸留塔に供給することが可能になる。したがって、プレ精製トリクロロシランでは、トリクロロシランの含有量（トリクロロシラン濃度）が９９％モル以上であることが好ましく、９９．５％モル以上であることがより好ましく、９９．９％モル以上であることがさらに好ましい。
According to the distillation purification in the pre-second distillation column, the content of dichlorosilane (dichlorosilane concentration) in trichlorosilane with reduced silicon tetrachloride concentration is 0.1% mole or more, more specifically 0.2%. Even if it is ~2% mole, it is possible to reduce its content (concentration) to less than 0.1% mole, more preferably to 10 ppm mole or less (TCD detection limit value). According to the pre-purification, trichlorosilane with a reduced dichlorosilane concentration extracted from the bottom of the pre-second distillation column, that is, pre-purified trichlorosilane is obtained. In this pre-purified trichlorosilane, the contents (concentrations) of silicon tetrachloride and dichlorosilane are both at a clean level of 10 ppm mol (TCD detection limit value) or less, and this is supplied to the first distillation column. becomes possible. Therefore, in pre-purified trichlorosilane, the trichlorosilane content (trichlorosilane concentration) is preferably 99% mole or more, more preferably 99.5% mole or more, and 99.9% mole or more. It is even more preferable.
なお、斯様にプレ精製で、トリクロロシランに対して沸点差の大きい不純物である前記四塩化珪素やジクロロシラン等の除去操作を施したとしても、粗トリクロロシランに含まれる、前記沸点近接不純物であるイソペンタン及びメチルジクロロシランの含有量（濃度）は実質低減しない。したがって、四塩化珪素およびジクロロシランを含む粗トリクロロシラン（プレ精製前の粗トリクロロシラン）中のこれら沸点近接不純物の濃度と、プレ精製トリクロロシラン中のこれら沸点近接不純物の濃度とは実質同一値であるのが普通である。ただし、これらが有意に変化している場合には、続く第１蒸留塔及び第２蒸留塔を組み合せて行われる、これら沸点近接不純物の除去では、そのイソペンタン及びメチルジクロロシランの排出前の基準濃度は、除去処理直前である、上記プレ精製トリクロロシラン中の濃度を基にして求めれば良い。
In addition, even if such pre-purification is performed to remove silicon tetrachloride, dichlorosilane, etc., which are impurities with a large boiling point difference with respect to trichlorosilane, the impurities near the boiling point contained in crude trichlorosilane will not be removed. The content (concentration) of certain isopentane and methyldichlorosilane is not substantially reduced. Therefore, the concentration of these near-boiling impurities in crude trichlorosilane containing silicon tetrachloride and dichlorosilane (crude trichlorosilane before pre-purification) and the concentration of these near-boiling impurities in pre-purified trichlorosilane are substantially the same. It is normal that there is. However, if these have changed significantly, the reference concentration of isopentane and methyldichlorosilane before discharge is determined in the removal of these near-boiling impurities, which is performed in combination with the subsequent first distillation column and second distillation column. may be determined based on the concentration in the pre-purified trichlorosilane immediately before the removal treatment.
前記本発明の方法により得られた精製トリクロロシランは、さらに吸着除去等の更なる精製処理や精製トリクロロシランを使用して多結晶シリコンを析出した後の排出ガスから回収したトリクロロシランと混合する混合処理を適宜に施しても良い。
The purified trichlorosilane obtained by the method of the present invention is further purified by adsorption and removal, and mixed with trichlorosilane recovered from the exhaust gas after polycrystalline silicon is precipitated using the purified trichlorosilane. Processing may be performed as appropriate.
以上説明した精製トリクロロシランの製造方法について、プレ精製を含む態様の蒸留フロー図である図１により、より具体化して示す。図１において、粗トリクロロシラン流通管１には、塩化水素、または、四塩化珪素および水素、を含有するガスを、冶金級シリコンと反応させることにより生成させた、粗トリクロロシランの液流が流通している。この粗トリクロロシランには、イソペンタン及びメチルジクロロシランの他、高沸点不純物である四塩化珪素等及び低沸点不純物であるジクロロシラン等が含有されている。
The method for producing purified trichlorosilane described above is shown in more detail with reference to FIG. 1, which is a distillation flow diagram of an embodiment including pre-purification. In FIG. 1, a liquid flow of crude trichlorosilane produced by reacting a gas containing hydrogen chloride or silicon tetrachloride and hydrogen with metallurgical grade silicon flows through a crude trichlorosilane flow pipe 1. are doing. In addition to isopentane and methyldichlorosilane, this crude trichlorosilane contains high boiling point impurities such as silicon tetrachloride and low boiling point impurities such as dichlorosilane.
この粗トリクロロシランは、まず、プレ精製に供されて、上記高沸点不純物である四塩化珪素及び低沸点不純物であるジクロロシランの除去が施される。即ち、粗トリクロロシラン流通管１は、プレ第１蒸留塔２の側部に繋がっており、該プレ第１蒸留塔２には上記粗トリクロロシランの液流が供給される。そして、プレ第１蒸留塔２では、底部に貯留される上記粗トリクロロシラン液が加熱され、その蒸留精製が前記条件で実施される。この蒸留精製により、塔底から、四塩化珪素濃度が前記粗トリクロロシラン中の濃度より１．１倍以上高い高沸点域画分に当たる塔底液が四塩化珪素濃縮塔底液抜出管３に抜き出され、他方で、塔頂からは四塩化珪素濃度が低減されたトリクロロシランの気相が、四塩化珪素低減トリクロロシラン留出管４に留出される。
This crude trichlorosilane is first subjected to pre-purification to remove silicon tetrachloride, which is a high boiling point impurity, and dichlorosilane, which is a low boiling point impurity. That is, the crude trichlorosilane flow pipe 1 is connected to the side of the pre-first distillation column 2, and the crude trichlorosilane liquid stream is supplied to the pre-first distillation column 2. In the pre-first distillation column 2, the crude trichlorosilane liquid stored at the bottom is heated, and distillation and purification thereof is carried out under the conditions described above. Through this distillation purification, the bottom liquid corresponding to the high boiling point fraction whose silicon tetrachloride concentration is 1.1 times or more higher than the concentration in the crude trichlorosilane is transferred from the bottom of the column to the silicon tetrachloride concentration column bottom liquid extraction pipe 3. On the other hand, a gas phase of trichlorosilane with a reduced silicon tetrachloride concentration is distilled from the top of the column to a silicon tetrachloride-reduced trichlorosilane distillation pipe 4.
この四塩化珪素低減トリクロロシラン留出管４に留出された四塩化珪素低減トリクロロシランの気相は凝縮器５により液化され、その液流の一部は、四塩化珪素低減トリクロロシラン還流管６から、前記プレ第１蒸留塔２に還流される。他方で、前記四塩化珪素低減トリクロロシラン還流管６から分岐された他方の四塩化珪素低減トリクロロシラン供給管７はプレ第２蒸留塔８の側部に繋がっており、該プレ第２蒸留塔８には、前記プレ第１蒸留塔２に還流された残余の四塩化珪素低減トリクロロシランの液流が供給される。そして、プレ第２蒸留塔８では、底部に貯留される上記四塩化珪素低減トリクロロシラン液が加熱され、その蒸留精製が前記条件で実施される。この蒸留精製により、塔頂から、ジクロロシラン濃度が前記粗トリクロロシラン中の濃度より１００倍以上高い低沸点域画分に当たる気相がジクロロシラン濃縮物留出管１０に留出し、他方で、塔底からはジクロロシラン濃度が低減されたプレ精製トリクロロシランの液流が、プレ精製トリクロロシラン抜出管９に抜き出される。
The gas phase of the silicon tetrachloride-reduced trichlorosilane distilled into the silicon-tetrachloride-reduced trichlorosilane distillation pipe 4 is liquefied by the condenser 5, and a part of the liquid stream is transferred to the silicon-tetrachloride-reduced trichlorosilane reflux pipe 6. From there, it is refluxed to the pre-first distillation column 2. On the other hand, the other silicon tetrachloride-reduced trichlorosilane supply pipe 7 branched from the silicon tetrachloride-reduced trichlorosilane reflux pipe 6 is connected to the side of the pre-second distillation column 8 . The remaining liquid stream of silicon tetrachloride-reduced trichlorosilane refluxed to the pre-first distillation column 2 is supplied to the pre-first distillation column 2. In the pre-second distillation column 8, the silicon tetrachloride-reduced trichlorosilane liquid stored at the bottom is heated, and its distillation purification is carried out under the conditions described above. Through this distillation purification, a gas phase corresponding to a low boiling point fraction in which the dichlorosilane concentration is 100 times or more higher than the concentration in the crude trichlorosilane is distilled from the top of the column to the dichlorosilane concentrate distillation tube 10, and on the other hand, A liquid stream of pre-purified trichlorosilane with a reduced dichlorosilane concentration is extracted from the bottom to a pre-purified trichlorosilane extraction pipe 9 .
このジクロロシラン濃縮物留出管１０に留出されたジクロロシラン濃縮物の気相は凝縮器１１により液化され、その液流の一部は、ジクロロシラン濃縮物還流管１２から前記プレ第２蒸留塔８に還流される。他方で、前記ジクロロシラン濃縮物還流管１２から分岐された他方のジクロロシラン濃縮物流通管１３から残余のジクロロシラン濃縮物が系外に送液される。
The gas phase of the dichlorosilane concentrate distilled into the dichlorosilane concentrate distillation pipe 10 is liquefied by the condenser 11, and a part of the liquid stream is transferred from the dichlorosilane concentrate reflux pipe 12 to the pre-second distillation It is refluxed to column 8. On the other hand, the remaining dichlorosilane concentrate is sent out of the system from the other dichlorosilane concentrate distribution pipe 13 branched from the dichlorosilane concentrate reflux pipe 12.
以上のプレ精製の後、上記プレ精製トリクロロシラン抜出管９を流れる、前記四塩化珪素及びジクロロシランの各除去が施されたプレ精製トリクロロシランについて、イソペンタン及びメチルジクロロシランの除去が施される。即ち、プレ精製トリクロロシラン抜出管９は、第１蒸留塔１４の側部に繋がっており、該第１蒸留塔１４には上記プレ精製トリクロロシランの液流が供給される。そして、第１蒸留塔１４では、底部に貯留される上記プレ精製トリクロロシラン液が加熱され、その蒸留精製が前記条件で実施される。この蒸留精製により、塔頂から、イソペンタン濃度が前記粗トリクロロシラン中の濃度より１５０倍以上高い低沸点域画分に当たる気相がイソペンタン濃縮物留出管１６に留出し、他方で、塔底からはイソペンタン濃度が低減されたトリクロロシランの液流が、イソペンタン低減トリクロロシラン抜出管１５に抜き出される。
After the above pre-purification, isopentane and methyldichlorosilane are removed from the pre-purified trichlorosilane flowing through the pre-purified trichlorosilane extraction pipe 9 from which silicon tetrachloride and dichlorosilane have been removed. . That is, the pre-purified trichlorosilane extraction pipe 9 is connected to the side of the first distillation column 14, and the liquid stream of the pre-purified trichlorosilane is supplied to the first distillation column 14. In the first distillation column 14, the pre-purified trichlorosilane liquid stored at the bottom is heated and distilled and purified under the conditions described above. Through this distillation purification, a gas phase corresponding to a low boiling point fraction whose isopentane concentration is 150 times or more higher than the concentration in the crude trichlorosilane is distilled from the top of the column to the isopentane concentrate distillation tube 16, and on the other hand, from the bottom of the column A liquid stream of trichlorosilane with a reduced isopentane concentration is extracted to an isopentane-reduced trichlorosilane extraction pipe 15.
このイソペンタン濃縮物留出管１６に留出されたイソペンタン濃縮物の気相は凝縮器１７により液化され、その液流の一部は、イソペンタン濃縮物還流管１８から前記第１蒸留塔１４に還流される。他方で、前記イソペンタン濃縮物還流管１８から分岐された他方のイソペンタン濃縮物流通管１９から残余のイソペンタン濃縮物が系外に送液される。
The gas phase of the isopentane concentrate distilled into the isopentane concentrate distillation pipe 16 is liquefied by the condenser 17, and a part of the liquid stream is refluxed from the isopentane concentrate reflux pipe 18 to the first distillation column 14. be done. On the other hand, the remaining isopentane concentrate is sent out of the system from the other isopentane concentrate distribution pipe 19 branched from the isopentane concentrate reflux pipe 18.
上記イソペンタン低減トリクロロシラン抜出管１５は、第２蒸留塔２０の側部に繋がっており、該第２蒸留塔２０には上記イソペンタン低減トリクロロシランの液流が供給される。そして、第２蒸留塔２０では、底部に貯留される上記イソペンタン低減トリクロロシラン液が加熱され、その蒸留精製が前記条件で実施される。この蒸留精製により、塔底から、メチルジクロロシラン濃度が前記粗トリクロロシラン中の濃度より１．５倍以上高い高沸点域画分に当たる塔底液がメチルジクロロシラン濃縮塔底液抜出管２１に抜き出され、他方で、塔頂からはメチルジクロロシラン濃度が低減されたトリクロロシランの気相が、精製トリクロロシラン留出管２２に留出される。
The isopentane-reduced trichlorosilane extraction pipe 15 is connected to the side of the second distillation column 20, and the second distillation column 20 is supplied with a liquid stream of the isopentane-reduced trichlorosilane. In the second distillation column 20, the isopentane-reduced trichlorosilane liquid stored at the bottom is heated and distilled and purified under the conditions described above. Through this distillation and purification, the bottom liquid corresponding to the high boiling point fraction whose methyldichlorosilane concentration is 1.5 times or more higher than the concentration in the crude trichlorosilane is transferred from the bottom of the column to the methyldichlorosilane concentration column bottom liquid extraction pipe 21. On the other hand, a gaseous phase of trichlorosilane with a reduced concentration of methyldichlorosilane is distilled from the top of the column to a purified trichlorosilane distillation tube 22.
この精製トリクロロシラン留出管２２に留出された精製トリクロロシランの気相は凝縮器２３により液化され、その液流の一部は、精製トリクロロシラン還流管２４から前記第２蒸留塔２０に還流される。そうして、前記精製トリクロロシラン還流管２４から分岐した他方の精製トリクロロシラン流通管２５から、本発明の製造方法が施された精製トリクロロシランが残余の液として取り出される。このようにして取得された精製トリクロロシランは、多結晶シリコンの製造用原料等として有用に使用すれば良い。
The gas phase of the purified trichlorosilane distilled into the purified trichlorosilane distillation tube 22 is liquefied by the condenser 23, and a part of the liquid stream is refluxed from the purified trichlorosilane reflux tube 24 to the second distillation column 20. be done. Then, purified trichlorosilane subjected to the manufacturing method of the present invention is taken out as a residual liquid from the other purified trichlorosilane flow pipe 25 branched from the purified trichlorosilane reflux pipe 24. The purified trichlorosilane thus obtained may be usefully used as a raw material for producing polycrystalline silicon.
以下、本発明を詳細に説明するために実施例をあげて説明するが、本発明は、これらの実施例に限定されるものではない。なお、実施例および比較例において実施されている、測定や評価は、以下の方法により求めた。
（１）各成分の分析方法
クロロシラン類の濃度は、熱伝導度型検出器（ＴＣＤ検出器）を備えたガスクロマトグラフ（クロロシラン類の検出下限値は１０ｐｐｍモル）で行った。炭素含有化合物の濃度は、検出器として質量分析器（ＭＳ）を備えたガスクロマトクロマトグラフ（ＧＣＭＳ）（検出下限値は１ｐｐｂモル）で行い、金属塩化物の濃度は誘導結合プラズマ（ＩＣＰ）発光分光分析装置（検出下限値は１ｐｐｂモル）で行った。
（２）精製トリクロロシランを使用して製造した多結晶シリコン中の炭素濃度の測定
トリクロロシランを気化して水素と混合したガスを、シーメンス法で １０ｍｍ角のシリコン芯線上で熱分解させて、シリコン芯線上にシリコンを析出させることで成長させた。得られた３０ｍｍ直径の多結晶シリコンロッドをフローティング・ゾーン法（ＦＺ法）により単結晶化させて、その単結晶シリコン中の炭素濃度を低温フーリエ変換赤外分光光度計（ＦＴ－ＩＲ）装置で測定（検出限界値は １０ｐｐｂ‐ａｔｏｍ）することで行った。
（３）粗トリクロロシランの製造条件
四塩化珪素と水素との混合ガスを、冶金級シリコンと約４８０～５２０℃の反応炉内で接触させ、冶金級シリコンを水素化塩素化させてトリクロロシラン（ＳｉＨＣｌ3）を含むガスを発生させた。そのガス中には、四塩化珪素（ＳｉＣｌ4）、ジクロロシラン（ＳｉＨ2Ｃｌ2）等が含まれ、さらに、冶金級シリコン中の珪素以外の不純物も反応炉内で水素化塩素化されて、塩化鉄（ＦｅＣｌ3）、塩化アルミニウム（ＡｌＣｌ3）、有機クロロシラン、各種有機物として発生ガス中に微量成分として含まれる。使用した原料の組成は、冶金級シリコンは、珪素濃度が９９質量％、鉄濃度が０．７質量％、アルミニウム濃度が０．３質量％、炭素濃度が３００ｐｐｍｗｔの組成で、四塩化珪素と水素は、９９質量％以上の純度であった。 EXAMPLES Hereinafter, in order to explain the present invention in detail, Examples will be given and explained, but the present invention is not limited to these Examples. The measurements and evaluations carried out in the Examples and Comparative Examples were determined by the following methods.
(1) Analysis method for each component The concentration of chlorosilanes was determined using a gas chromatograph equipped with a thermal conductivity detector (TCD detector) (lower detection limit for chlorosilanes was 10 ppm mol). The concentration of carbon-containing compounds was determined using a gas chromatograph (GCMS) equipped with a mass spectrometer (MS) as a detector (lower limit of detection is 1 ppb mol), and the concentration of metal chlorides was determined using inductively coupled plasma (ICP) emission spectroscopy. The analysis was performed using an analyzer (lower limit of detection is 1 ppb mol).
(2) Measuring the carbon concentration in polycrystalline silicon produced using purified trichlorosilane Trichlorosilane is vaporized and mixed with hydrogen, and the gas is thermally decomposed on a 10 mm square silicon core wire using the Siemens method. It was grown by depositing silicon on the core wire. The obtained polycrystalline silicon rod with a diameter of 30 mm was single-crystallized by the floating zone method (FZ method), and the carbon concentration in the single-crystal silicon was measured using a low-temperature Fourier transform infrared spectrophotometer (FT-IR). This was done by measuring (detection limit value is 10 ppb-atom).
(3) Conditions for producing crude trichlorosilane A mixed gas of silicon tetrachloride and hydrogen is brought into contact with metallurgical grade silicon in a reactor at approximately 480 to 520°C, and the metallurgical grade silicon is hydrochlorinated to produce trichlorosilane (trichlorosilane). A gas containing SiHCl 3 ) was generated. The gas contains silicon tetrachloride (SiCl 4 ), dichlorosilane (SiH 2 Cl 2 ), etc., and impurities other than silicon in metallurgical grade silicon are also hydrochlorinated in the reactor. Iron chloride (FeCl 3 ), aluminum chloride (AlCl 3 ), organic chlorosilane, and various other organic substances are contained as trace components in the generated gas. The composition of the raw materials used was that the metallurgical grade silicon had a silicon concentration of 99% by mass, an iron concentration of 0.7% by mass, an aluminum concentration of 0.3% by mass, and a carbon concentration of 300ppmwt, silicon tetrachloride and hydrogen. The purity was 99% by mass or more.
（１）各成分の分析方法
クロロシラン類の濃度は、熱伝導度型検出器（ＴＣＤ検出器）を備えたガスクロマトグラフ（クロロシラン類の検出下限値は１０ｐｐｍモル）で行った。炭素含有化合物の濃度は、検出器として質量分析器（ＭＳ）を備えたガスクロマトクロマトグラフ（ＧＣＭＳ）（検出下限値は１ｐｐｂモル）で行い、金属塩化物の濃度は誘導結合プラズマ（ＩＣＰ）発光分光分析装置（検出下限値は１ｐｐｂモル）で行った。
（２）精製トリクロロシランを使用して製造した多結晶シリコン中の炭素濃度の測定
トリクロロシランを気化して水素と混合したガスを、シーメンス法で １０ｍｍ角のシリコン芯線上で熱分解させて、シリコン芯線上にシリコンを析出させることで成長させた。得られた３０ｍｍ直径の多結晶シリコンロッドをフローティング・ゾーン法（ＦＺ法）により単結晶化させて、その単結晶シリコン中の炭素濃度を低温フーリエ変換赤外分光光度計（ＦＴ－ＩＲ）装置で測定（検出限界値は １０ｐｐｂ‐ａｔｏｍ）することで行った。
（３）粗トリクロロシランの製造条件
四塩化珪素と水素との混合ガスを、冶金級シリコンと約４８０～５２０℃の反応炉内で接触させ、冶金級シリコンを水素化塩素化させてトリクロロシラン（ＳｉＨＣｌ3）を含むガスを発生させた。そのガス中には、四塩化珪素（ＳｉＣｌ4）、ジクロロシラン（ＳｉＨ2Ｃｌ2）等が含まれ、さらに、冶金級シリコン中の珪素以外の不純物も反応炉内で水素化塩素化されて、塩化鉄（ＦｅＣｌ3）、塩化アルミニウム（ＡｌＣｌ3）、有機クロロシラン、各種有機物として発生ガス中に微量成分として含まれる。使用した原料の組成は、冶金級シリコンは、珪素濃度が９９質量％、鉄濃度が０．７質量％、アルミニウム濃度が０．３質量％、炭素濃度が３００ｐｐｍｗｔの組成で、四塩化珪素と水素は、９９質量％以上の純度であった。 EXAMPLES Hereinafter, in order to explain the present invention in detail, Examples will be given and explained, but the present invention is not limited to these Examples. The measurements and evaluations carried out in the Examples and Comparative Examples were determined by the following methods.
(1) Analysis method for each component The concentration of chlorosilanes was determined using a gas chromatograph equipped with a thermal conductivity detector (TCD detector) (lower detection limit for chlorosilanes was 10 ppm mol). The concentration of carbon-containing compounds was determined using a gas chromatograph (GCMS) equipped with a mass spectrometer (MS) as a detector (lower limit of detection is 1 ppb mol), and the concentration of metal chlorides was determined using inductively coupled plasma (ICP) emission spectroscopy. The analysis was performed using an analyzer (lower limit of detection is 1 ppb mol).
(2) Measuring the carbon concentration in polycrystalline silicon produced using purified trichlorosilane Trichlorosilane is vaporized and mixed with hydrogen, and the gas is thermally decomposed on a 10 mm square silicon core wire using the Siemens method. It was grown by depositing silicon on the core wire. The obtained polycrystalline silicon rod with a diameter of 30 mm was single-crystallized by the floating zone method (FZ method), and the carbon concentration in the single-crystal silicon was measured using a low-temperature Fourier transform infrared spectrophotometer (FT-IR). This was done by measuring (detection limit value is 10 ppb-atom).
(3) Conditions for producing crude trichlorosilane A mixed gas of silicon tetrachloride and hydrogen is brought into contact with metallurgical grade silicon in a reactor at approximately 480 to 520°C, and the metallurgical grade silicon is hydrochlorinated to produce trichlorosilane (trichlorosilane). A gas containing SiHCl 3 ) was generated. The gas contains silicon tetrachloride (SiCl 4 ), dichlorosilane (SiH 2 Cl 2 ), etc., and impurities other than silicon in metallurgical grade silicon are also hydrochlorinated in the reactor. Iron chloride (FeCl 3 ), aluminum chloride (AlCl 3 ), organic chlorosilane, and various other organic substances are contained as trace components in the generated gas. The composition of the raw materials used was that the metallurgical grade silicon had a silicon concentration of 99% by mass, an iron concentration of 0.7% by mass, an aluminum concentration of 0.3% by mass, and a carbon concentration of 300ppmwt, silicon tetrachloride and hydrogen. The purity was 99% by mass or more.
このトリクロロシランを含む反応生成ガスを０～２０℃温度範囲に冷却して、冷却凝縮液を得た。この冷却液を粗トリクロロシラン回収塔に送液して、四塩化珪素より沸点の高い塩化鉄等の金属塩化物を分離して、粗トリクロロシラン液を得た。
The reaction product gas containing trichlorosilane was cooled to a temperature range of 0 to 20°C to obtain a cooled condensate. This coolant was sent to a crude trichlorosilane recovery tower to separate metal chlorides such as iron chloride, which have a boiling point higher than silicon tetrachloride, to obtain a crude trichlorosilane liquid.
得られた粗トリクロロシラン液の組成は、トリクロロシラン濃度が２７．２％モル，四塩化珪素濃度が７２．３％モル，ジクロロシラン濃度が０．５％モル、メチルジクロロシラン濃度が１５０００ｐｐｂモル、イソペンタン濃度が８５ｐｐｂモル、塩化鉄濃度、塩化アルミニウム濃度がそれぞれ１ｐｐｂ‐ｗｔ以下であった。
The composition of the obtained crude trichlorosilane liquid is as follows: trichlorosilane concentration is 27.2% mole, silicon tetrachloride concentration is 72.3% mole, dichlorosilane concentration is 0.5% mole, methyldichlorosilane concentration is 15000 ppb mole, The isopentane concentration was 85 ppb mole, and the iron chloride concentration and aluminum chloride concentration were each less than 1 ppb-wt.
実施例１
前記粗トリクロロシラン液を、前記図１に示した蒸留フローに供して処理した。 Example 1
The crude trichlorosilane liquid was subjected to the distillation flow shown in FIG. 1 and treated.
前記粗トリクロロシラン液を、前記図１に示した蒸留フローに供して処理した。 Example 1
The crude trichlorosilane liquid was subjected to the distillation flow shown in FIG. 1 and treated.
〔各蒸留塔〕
図１に示した蒸留フローにおいて、プレ第１蒸留塔２とプレ第２蒸留塔８は、それぞれ塔径が１５０ｍｍ直径で理論段数が３０段の蒸留塔を使用した。第１蒸留塔１４は、塔径が１５０ｍｍ直径で理論段数が８０段の蒸留塔を、第２蒸留塔２０は、塔径が１５０ｍｍ直径で理論段数が８５段の蒸留塔を使用した。 [Each distillation column]
In the distillation flow shown in FIG. 1, thepre-first distillation column 2 and the pre-second distillation column 8 each had a column diameter of 150 mm and a theoretical plate number of 30. The first distillation column 14 used was a distillation column with a diameter of 150 mm and the number of theoretical plates of 80, and the second distillation column 20 used a distillation column with a column diameter of 150 mm and the number of theoretical plates of 85.
図１に示した蒸留フローにおいて、プレ第１蒸留塔２とプレ第２蒸留塔８は、それぞれ塔径が１５０ｍｍ直径で理論段数が３０段の蒸留塔を使用した。第１蒸留塔１４は、塔径が１５０ｍｍ直径で理論段数が８０段の蒸留塔を、第２蒸留塔２０は、塔径が１５０ｍｍ直径で理論段数が８５段の蒸留塔を使用した。 [Each distillation column]
In the distillation flow shown in FIG. 1, the
〔各蒸留塔の運転条件〕
プレ第１蒸留塔２は、塔底の圧力が、２００ｋＰａ（ゲージ圧）、塔底部温度が９１～９２℃の条件で運転した。プレ第２蒸留塔８は、塔頂の圧力が、１００ｋＰａ（ゲージ圧）、塔頂部温度が４１～４２℃の条件で運転した。第１蒸留塔１４は、塔頂の圧力が、１００ｋＰａ（ゲージ圧）、塔頂部温度が５１～５２℃の条件で運転した。第２蒸留塔２０は、塔底の圧力が、２００ｋＰａ（ゲージ圧）、塔底部温度が６５～６６℃の条件で運転した。 [Operating conditions for each distillation column]
Thepre-first distillation column 2 was operated under the conditions that the pressure at the bottom of the column was 200 kPa (gauge pressure) and the temperature at the bottom of the column was 91 to 92°C. The pre-second distillation column 8 was operated under the conditions that the pressure at the top of the column was 100 kPa (gauge pressure) and the temperature at the top of the column was 41 to 42°C. The first distillation column 14 was operated under the conditions that the pressure at the top of the column was 100 kPa (gauge pressure) and the temperature at the top of the column was 51 to 52°C. The second distillation column 20 was operated under the conditions that the pressure at the bottom of the column was 200 kPa (gauge pressure) and the temperature at the bottom of the column was 65 to 66°C.
プレ第１蒸留塔２は、塔底の圧力が、２００ｋＰａ（ゲージ圧）、塔底部温度が９１～９２℃の条件で運転した。プレ第２蒸留塔８は、塔頂の圧力が、１００ｋＰａ（ゲージ圧）、塔頂部温度が４１～４２℃の条件で運転した。第１蒸留塔１４は、塔頂の圧力が、１００ｋＰａ（ゲージ圧）、塔頂部温度が５１～５２℃の条件で運転した。第２蒸留塔２０は、塔底の圧力が、２００ｋＰａ（ゲージ圧）、塔底部温度が６５～６６℃の条件で運転した。 [Operating conditions for each distillation column]
The
〔各蒸留塔での不純物除去結果の確認〕
上記各条件での運転が安定化したのち、蒸留フローの各所でサンプリングして、その組成を分析した。 [Confirmation of impurity removal results in each distillation column]
After the operation under each of the above conditions became stable, samples were taken at various points in the distillation flow and their compositions were analyzed.
上記各条件での運転が安定化したのち、蒸留フローの各所でサンプリングして、その組成を分析した。 [Confirmation of impurity removal results in each distillation column]
After the operation under each of the above conditions became stable, samples were taken at various points in the distillation flow and their compositions were analyzed.
（プレ第１蒸留塔２）
四塩化珪素濃縮塔底液抜出管３を流れる塔底液をサンプリングして組成を分析したところ、四塩化珪素濃度が９９．９％モルで、トリクロロシラン濃度は検出限界値の１０ｐｐｍモル以下であった。塔底液の四塩化珪素濃度は、粗トリクロロシラン中の濃度より１．３８倍に高まっており、このことから、当該プレ第１蒸留塔２の蒸留操作により、塔頂から留出して、四塩化珪素低減トリクロロシラン留出管４を流れるトリクロロシランでは、不純物の四塩化珪素が高度に除去されていることが確認された。 (Pre-first distillation column 2)
When we sampled the bottom liquid flowing through the silicon tetrachloride concentration column bottomliquid extraction pipe 3 and analyzed its composition, we found that the silicon tetrachloride concentration was 99.9% molar, and the trichlorosilane concentration was below the detection limit of 10 ppm molar. there were. The concentration of silicon tetrachloride in the column bottom liquid is 1.38 times higher than the concentration in the crude trichlorosilane. Therefore, by the distillation operation of the pre-first distillation column 2, silicon tetrachloride is distilled from the column top and It was confirmed that the impurity silicon tetrachloride was highly removed from the trichlorosilane flowing through the silicon chloride-reduced trichlorosilane distillation tube 4.
四塩化珪素濃縮塔底液抜出管３を流れる塔底液をサンプリングして組成を分析したところ、四塩化珪素濃度が９９．９％モルで、トリクロロシラン濃度は検出限界値の１０ｐｐｍモル以下であった。塔底液の四塩化珪素濃度は、粗トリクロロシラン中の濃度より１．３８倍に高まっており、このことから、当該プレ第１蒸留塔２の蒸留操作により、塔頂から留出して、四塩化珪素低減トリクロロシラン留出管４を流れるトリクロロシランでは、不純物の四塩化珪素が高度に除去されていることが確認された。 (Pre-first distillation column 2)
When we sampled the bottom liquid flowing through the silicon tetrachloride concentration column bottom
（プレ第２蒸留塔８）
ジクロロシラン濃縮物流通管１３を流れるジクロロシラン濃縮物をサンプリングして組成を分析したところ、ジクロロシラン濃度が８１％モル、トリクロロシラン濃度が１９％モル、四塩化珪素濃度が検出限界値の１０ｐｐｍモル以下であった。ジクロロシラン濃縮物は、ジクロロシラン濃度が粗トリクロロシラン中の濃度より１６２倍に高まっており、このことから、当該プレ第２蒸留塔８の蒸留操作により、塔底から抜き出されて、プレ精製トリクロロシラン抜出管９を流れるトリクロロシランでは、不純物のジクロロシランが高度に除去されていることが確認された。実際に、プレ精製トリクロロシラン抜出管９からサンプリングして組成を分析したところ、ジクロロシランと四塩化珪素は、検出限界値１０ｐｐｍモル以下で、トリクロロシランが９９．９％モル、メチルジクロロシランが１５０００ｐｐｂモル、イソペンタンが８５ｐｐｂモルであった。 (Pre-second distillation column 8)
When we sampled the dichlorosilane concentrate flowing through the dichlorosilaneconcentrate flow pipe 13 and analyzed its composition, we found that the dichlorosilane concentration was 81% molar, the trichlorosilane concentration was 19% molar, and the silicon tetrachloride concentration was 10 ppm molar, which was the detection limit. It was below. The concentration of dichlorosilane in the dichlorosilane concentrate is 162 times higher than the concentration in the crude trichlorosilane, and therefore, it is extracted from the bottom of the column by the distillation operation of the second pre-distillation column 8 and subjected to pre-purification. It was confirmed that the impurity dichlorosilane was removed to a high degree from the trichlorosilane flowing through the trichlorosilane extraction pipe 9. In fact, when we sampled from the pre-purified trichlorosilane extraction tube 9 and analyzed its composition, we found that dichlorosilane and silicon tetrachloride were below the detection limit of 10 ppm mol, trichlorosilane was 99.9% mol, and methyldichlorosilane was 99.9% mol. 15,000 ppb mole, and isopentane was 85 ppb mole.
ジクロロシラン濃縮物流通管１３を流れるジクロロシラン濃縮物をサンプリングして組成を分析したところ、ジクロロシラン濃度が８１％モル、トリクロロシラン濃度が１９％モル、四塩化珪素濃度が検出限界値の１０ｐｐｍモル以下であった。ジクロロシラン濃縮物は、ジクロロシラン濃度が粗トリクロロシラン中の濃度より１６２倍に高まっており、このことから、当該プレ第２蒸留塔８の蒸留操作により、塔底から抜き出されて、プレ精製トリクロロシラン抜出管９を流れるトリクロロシランでは、不純物のジクロロシランが高度に除去されていることが確認された。実際に、プレ精製トリクロロシラン抜出管９からサンプリングして組成を分析したところ、ジクロロシランと四塩化珪素は、検出限界値１０ｐｐｍモル以下で、トリクロロシランが９９．９％モル、メチルジクロロシランが１５０００ｐｐｂモル、イソペンタンが８５ｐｐｂモルであった。 (Pre-second distillation column 8)
When we sampled the dichlorosilane concentrate flowing through the dichlorosilane
（第１蒸留塔１４）
イソペンタン濃縮物流通管１９を流れるイソペンタン濃縮物をサンプリングして組成を分析したところ、トリクロロシラン濃度が９９．９％モルで、イソペンタン濃度が２３，０００ｐｐｂモル、メチルジクロロシラン濃度が３ｐｐｂモルであった。イソペンタン濃縮物は、イソペンタン濃度が粗トリクロロシラン（プレ精製トリクロロシラン）中の濃度より２２４倍に高まっており、このことから、当該第１蒸留塔１４の蒸留操作により、塔底から抜き出されて、イソペンタン低減トリクロロシラン抜出管１５を流れるトリクロロシランでは、不純物のイソペンタンが高度に除去されていることが確認された。実際に、イソペンタン低減トリクロロシラン抜出管１５からサンプリングして組成を分析したところ、トリクロロシランが９９．９％モルで、イソペンタンが１７ｐｐｂモル、メチルジクロロシランが１５０００ｐｐｂモルであった。 (First distillation column 14)
When the isopentane concentrate flowing through the isopentaneconcentrate flow pipe 19 was sampled and its composition was analyzed, the concentration of trichlorosilane was 99.9% molar, the concentration of isopentane was 23,000 ppb molar, and the concentration of methyldichlorosilane was 3 ppb molar. . The concentration of isopentane in the isopentane concentrate is 224 times higher than the concentration in crude trichlorosilane (pre-purified trichlorosilane), and therefore, it is extracted from the bottom of the column by the distillation operation of the first distillation column 14. It was confirmed that impurity isopentane was highly removed from the trichlorosilane flowing through the isopentane-reduced trichlorosilane extraction pipe 15. In fact, when a sample was taken from the isopentane-reduced trichlorosilane extraction tube 15 and its composition was analyzed, it was found that trichlorosilane was 99.9% mole, isopentane was 17 ppb mole, and methyldichlorosilane was 15000 ppb mole.
イソペンタン濃縮物流通管１９を流れるイソペンタン濃縮物をサンプリングして組成を分析したところ、トリクロロシラン濃度が９９．９％モルで、イソペンタン濃度が２３，０００ｐｐｂモル、メチルジクロロシラン濃度が３ｐｐｂモルであった。イソペンタン濃縮物は、イソペンタン濃度が粗トリクロロシラン（プレ精製トリクロロシラン）中の濃度より２２４倍に高まっており、このことから、当該第１蒸留塔１４の蒸留操作により、塔底から抜き出されて、イソペンタン低減トリクロロシラン抜出管１５を流れるトリクロロシランでは、不純物のイソペンタンが高度に除去されていることが確認された。実際に、イソペンタン低減トリクロロシラン抜出管１５からサンプリングして組成を分析したところ、トリクロロシランが９９．９％モルで、イソペンタンが１７ｐｐｂモル、メチルジクロロシランが１５０００ｐｐｂモルであった。 (First distillation column 14)
When the isopentane concentrate flowing through the isopentane
（第２蒸留塔２０）
メチルジクロロシラン濃縮塔底液抜出管２１を流れる塔底液をサンプリングして組成を分析したところ、トリクロロシラン濃度が９９．９％モルで、イソペンタン濃度が１７ｐｐｂモル、メチルジクロロシラン濃度が３３０００ｐｐｂモルであった。係る塔底液のメチルジクロロシラン濃度は、粗トリクロロシラン中（プレ精製トリクロロシラン）の濃度より２．２倍に高まっており、このことから、当該第２蒸留塔２０の蒸留操作により、塔頂から留出して、精製トリクロロシラン留出管２２を流れるトリクロロシランでは、不純物のメチルジクロロシランが高度に除去されていることが確認された。実際に、精製トリクロロシラン流通管２５からサンプリングして、得られた精製トリクロロシランの組成を分析したところ、トリクロロシラン濃度が９９．９％モルで、イソペンタン濃度が１７ｐｐｂモル、メチルジクロロシラン濃度が７２ｐｐｂモルの高純度なものであった。 (Second distillation column 20)
When we sampled the bottom liquid flowing through the methyldichlorosilane concentration column bottomliquid extraction pipe 21 and analyzed its composition, we found that the trichlorosilane concentration was 99.9% mol, the isopentane concentration was 17 ppb mol, and the methyldichlorosilane concentration was 33000 ppb mol. Met. The concentration of methyldichlorosilane in the bottom liquid is 2.2 times higher than the concentration in the crude trichlorosilane (pre-purified trichlorosilane). It was confirmed that the impurity methyldichlorosilane was removed to a high degree from the trichlorosilane distilled from the filtrate and flowing through the purified trichlorosilane distillation tube 22. In fact, when we analyzed the composition of the purified trichlorosilane sampled from the purified trichlorosilane flow pipe 25, we found that the trichlorosilane concentration was 99.9% molar, the isopentane concentration was 17 ppb molar, and the methyldichlorosilane concentration was 72 ppb. It was of high molar purity.
メチルジクロロシラン濃縮塔底液抜出管２１を流れる塔底液をサンプリングして組成を分析したところ、トリクロロシラン濃度が９９．９％モルで、イソペンタン濃度が１７ｐｐｂモル、メチルジクロロシラン濃度が３３０００ｐｐｂモルであった。係る塔底液のメチルジクロロシラン濃度は、粗トリクロロシラン中（プレ精製トリクロロシラン）の濃度より２．２倍に高まっており、このことから、当該第２蒸留塔２０の蒸留操作により、塔頂から留出して、精製トリクロロシラン留出管２２を流れるトリクロロシランでは、不純物のメチルジクロロシランが高度に除去されていることが確認された。実際に、精製トリクロロシラン流通管２５からサンプリングして、得られた精製トリクロロシランの組成を分析したところ、トリクロロシラン濃度が９９．９％モルで、イソペンタン濃度が１７ｐｐｂモル、メチルジクロロシラン濃度が７２ｐｐｂモルの高純度なものであった。 (Second distillation column 20)
When we sampled the bottom liquid flowing through the methyldichlorosilane concentration column bottom
〔トリクロロシランを使用して製造した多結晶シリコン中の炭素濃度確認〕
前記得られた精製トリクロロシランを用いて多結晶シリコンを製造し、その炭素濃度を測定したところ３０ｐｐｂモルの低含有量であった。 [Confirmation of carbon concentration in polycrystalline silicon produced using trichlorosilane]
Polycrystalline silicon was produced using the purified trichlorosilane obtained above, and its carbon concentration was measured and found to be as low as 30 ppb mol.
前記得られた精製トリクロロシランを用いて多結晶シリコンを製造し、その炭素濃度を測定したところ３０ｐｐｂモルの低含有量であった。 [Confirmation of carbon concentration in polycrystalline silicon produced using trichlorosilane]
Polycrystalline silicon was produced using the purified trichlorosilane obtained above, and its carbon concentration was measured and found to be as low as 30 ppb mol.
比較例１
実施例１において、粗クロロシラン液の蒸留フローを、図１に示したものから図２に示したものに変更して処理する以外は同様に実施して、精製トリクロロシランを製造した。なお、図２の蒸留フローは、図１のものでは粗トリクロロシラン(プレ精製トリクロロシラン)の蒸留が、第１蒸留塔１４で、イソペンタン濃縮物を塔頂から留出させ、塔底からイソペンタン低減トリクロロシランを得て、このイソペンタン低減トリクロロシランを第２蒸留塔に供給して、該第２蒸留塔２０で、メチルジクロロシラン濃縮塔底液を抜き出して、塔頂から精製トリクロロシランを留出させていたのに対して、これらの除去対象を入れ替えて、第２蒸留塔２０でメチルジクロロシラン濃縮塔底液を抜き出して、塔頂からメチルジクロロシラン低減トリクロロシランを留出させ、このメチルジクロロシラン低減トリクロロシランを第１蒸留塔に供給して、該第１蒸留塔１４で、イソペンタン濃縮物を塔頂から留出させ、塔底から精製トリクロロシランを得ている点で工程が異なっており、これらの関係以外の〔各蒸留塔〕の設計や〔その運転条件〕は両者実質同じであった。 Comparative example 1
Purified trichlorosilane was produced in the same manner as in Example 1, except that the distillation flow of the crude chlorosilane liquid was changed from that shown in FIG. 1 to that shown in FIG. 2. In addition, in the distillation flow of FIG. 2, in the one shown in FIG. 1, crude trichlorosilane (pre-purified trichlorosilane) is distilled, but isopentane concentrate is distilled from the top of the column in thefirst distillation column 14, and isopentane reduction is distilled from the bottom of the column. Obtain trichlorosilane, supply this isopentane-reduced trichlorosilane to a second distillation column, extract the methyldichlorosilane concentration column bottom liquid from the second distillation column 20, and distill purified trichlorosilane from the top of the column. However, by replacing the objects to be removed, the methyldichlorosilane concentration column bottom liquid is extracted from the second distillation column 20, and the methyldichlorosilane-reduced trichlorosilane is distilled from the top of the column. The process differs in that reduced trichlorosilane is supplied to the first distillation column, and in the first distillation column 14, isopentane concentrate is distilled from the top of the column, and purified trichlorosilane is obtained from the bottom of the column. Other than these relationships, the design of each distillation column and its operating conditions were essentially the same.
実施例１において、粗クロロシラン液の蒸留フローを、図１に示したものから図２に示したものに変更して処理する以外は同様に実施して、精製トリクロロシランを製造した。なお、図２の蒸留フローは、図１のものでは粗トリクロロシラン(プレ精製トリクロロシラン)の蒸留が、第１蒸留塔１４で、イソペンタン濃縮物を塔頂から留出させ、塔底からイソペンタン低減トリクロロシランを得て、このイソペンタン低減トリクロロシランを第２蒸留塔に供給して、該第２蒸留塔２０で、メチルジクロロシラン濃縮塔底液を抜き出して、塔頂から精製トリクロロシランを留出させていたのに対して、これらの除去対象を入れ替えて、第２蒸留塔２０でメチルジクロロシラン濃縮塔底液を抜き出して、塔頂からメチルジクロロシラン低減トリクロロシランを留出させ、このメチルジクロロシラン低減トリクロロシランを第１蒸留塔に供給して、該第１蒸留塔１４で、イソペンタン濃縮物を塔頂から留出させ、塔底から精製トリクロロシランを得ている点で工程が異なっており、これらの関係以外の〔各蒸留塔〕の設計や〔その運転条件〕は両者実質同じであった。 Comparative example 1
Purified trichlorosilane was produced in the same manner as in Example 1, except that the distillation flow of the crude chlorosilane liquid was changed from that shown in FIG. 1 to that shown in FIG. 2. In addition, in the distillation flow of FIG. 2, in the one shown in FIG. 1, crude trichlorosilane (pre-purified trichlorosilane) is distilled, but isopentane concentrate is distilled from the top of the column in the
〔各蒸留塔での不純物除去結果の確認〕
（プレ第１蒸留塔２）及び（プレ第２蒸留塔８）までの結果は、実施例１と同一工程であり同じ結果であった。 [Confirmation of impurity removal results in each distillation column]
The results up to (pre-first distillation column 2) and (pre-second distillation column 8) were the same steps as in Example 1, and the results were the same.
（プレ第１蒸留塔２）及び（プレ第２蒸留塔８）までの結果は、実施例１と同一工程であり同じ結果であった。 [Confirmation of impurity removal results in each distillation column]
The results up to (pre-first distillation column 2) and (pre-second distillation column 8) were the same steps as in Example 1, and the results were the same.
（第２蒸留塔２０）
メチルジクロロシラン濃縮塔底液抜出管２１を流れる塔底液をサンプリングして組成を分析したところ、トリクロロシラン濃度が９９．９％モルで、イソペンタン濃度が８５ｐｐｂモル、メチルジクロロシラン濃度が３３０００ｐｐｂモルであった。係る塔底液のメチルジクロロシラン濃度は、粗トリクロロシラン中（プレ精製トリクロロシラン）の濃度より２．２倍に高まっており、このことから、メチルジクロロシランを先に除去する場合であっても、当該第２蒸留塔２０の塔頂から留出して、メチルジクロロシラン低減トリクロロシラン留出管２２を流れるトリクロロシランでは、メチルジクロロシランが高度に除去されていることが確認された。実際に、メチルジクロロシラン低減トリクロロシラン供給管２１からサンプリングして組成を分析したところ、トリクロロシラン濃度が９９．９％モルで、イソペンタン濃度が８５ｐｐｂモル、メチルジクロロシラン濃度が７３ｐｐｂモルであった。 (Second distillation column 20)
When we sampled the bottom liquid flowing through the methyldichlorosilane concentration column bottomliquid extraction pipe 21 and analyzed its composition, we found that the trichlorosilane concentration was 99.9% mol, the isopentane concentration was 85 ppb mol, and the methyldichlorosilane concentration was 33000 ppb mol. Met. The concentration of methyldichlorosilane in the bottom liquid is 2.2 times higher than the concentration in crude trichlorosilane (pre-purified trichlorosilane), and from this, even if methyldichlorosilane is removed first, It was confirmed that methyldichlorosilane was highly removed from the trichlorosilane distilled from the top of the second distillation column 20 and flowing through the methyldichlorosilane-reduced trichlorosilane distillation tube 22. In fact, when a sample was taken from the methyldichlorosilane-reduced trichlorosilane supply pipe 21 and its composition was analyzed, the trichlorosilane concentration was 99.9% mole, the isopentane concentration was 85 ppb mole, and the methyldichlorosilane concentration was 73 ppb mole.
メチルジクロロシラン濃縮塔底液抜出管２１を流れる塔底液をサンプリングして組成を分析したところ、トリクロロシラン濃度が９９．９％モルで、イソペンタン濃度が８５ｐｐｂモル、メチルジクロロシラン濃度が３３０００ｐｐｂモルであった。係る塔底液のメチルジクロロシラン濃度は、粗トリクロロシラン中（プレ精製トリクロロシラン）の濃度より２．２倍に高まっており、このことから、メチルジクロロシランを先に除去する場合であっても、当該第２蒸留塔２０の塔頂から留出して、メチルジクロロシラン低減トリクロロシラン留出管２２を流れるトリクロロシランでは、メチルジクロロシランが高度に除去されていることが確認された。実際に、メチルジクロロシラン低減トリクロロシラン供給管２１からサンプリングして組成を分析したところ、トリクロロシラン濃度が９９．９％モルで、イソペンタン濃度が８５ｐｐｂモル、メチルジクロロシラン濃度が７３ｐｐｂモルであった。 (Second distillation column 20)
When we sampled the bottom liquid flowing through the methyldichlorosilane concentration column bottom
（第１蒸留塔１４）
イソペンタン濃縮物流通管１９を流れるイソペンタン濃縮物をサンプリングして組成を分析したところ、トリクロロシラン濃度が９９．９％モルで、イソペンタン濃度が１３０００ｐｐｂモル、メチルジクロロシラン濃度が７３ｐｐｂモルであった。イソペンタン濃縮物は、イソペンタン濃度が粗トリクロロシラン（プレ精製トリクロロシラン）中の濃度より１５２倍に高まっており、このことから、当該第１蒸留塔１４の蒸留操作により、塔底から抜き出されて、精製トリクロロシラン抜出管１５を流れるトリクロロシランでは、イソペンタンが高濃度で除去されていることが確認された。実際に、精製トリクロロシラン抜出管１５からサンプリングして組成を分析したところ、トリクロロシラン濃度が９９．９％モルで、イソペンタン濃度が１８ｐｐｂモル、メチルジクロロシラン濃度が７３ｐｐｂモルであり、係るＧＣＭＳによる測定ではイソペンタン濃度もメチルジクロロシラン濃度も、前記実施例１で製造した精製トリクロロシランに近い程度に低減できていた。 (First distillation column 14)
When the isopentane concentrate flowing through the isopentaneconcentrate flow pipe 19 was sampled and its composition was analyzed, the concentration of trichlorosilane was 99.9% molar, the concentration of isopentane was 13000 ppb molar, and the concentration of methyldichlorosilane was 73 ppb molar. The concentration of isopentane in the isopentane concentrate is 152 times higher than the concentration in crude trichlorosilane (pre-purified trichlorosilane), and therefore, it is extracted from the bottom of the column by the distillation operation of the first distillation column 14. It was confirmed that isopentane was removed at a high concentration from the trichlorosilane flowing through the purified trichlorosilane extraction pipe 15. In fact, when we sampled from the purified trichlorosilane extraction pipe 15 and analyzed its composition, we found that the trichlorosilane concentration was 99.9% mole, the isopentane concentration was 18 ppb mole, and the methyldichlorosilane concentration was 73 ppb mole, and the GCMS results showed that The measurements showed that both the isopentane concentration and the methyldichlorosilane concentration were reduced to levels close to those of the purified trichlorosilane produced in Example 1.
イソペンタン濃縮物流通管１９を流れるイソペンタン濃縮物をサンプリングして組成を分析したところ、トリクロロシラン濃度が９９．９％モルで、イソペンタン濃度が１３０００ｐｐｂモル、メチルジクロロシラン濃度が７３ｐｐｂモルであった。イソペンタン濃縮物は、イソペンタン濃度が粗トリクロロシラン（プレ精製トリクロロシラン）中の濃度より１５２倍に高まっており、このことから、当該第１蒸留塔１４の蒸留操作により、塔底から抜き出されて、精製トリクロロシラン抜出管１５を流れるトリクロロシランでは、イソペンタンが高濃度で除去されていることが確認された。実際に、精製トリクロロシラン抜出管１５からサンプリングして組成を分析したところ、トリクロロシラン濃度が９９．９％モルで、イソペンタン濃度が１８ｐｐｂモル、メチルジクロロシラン濃度が７３ｐｐｂモルであり、係るＧＣＭＳによる測定ではイソペンタン濃度もメチルジクロロシラン濃度も、前記実施例１で製造した精製トリクロロシランに近い程度に低減できていた。 (First distillation column 14)
When the isopentane concentrate flowing through the isopentane
〔トリクロロシランを使用して製造した多結晶シリコン中の炭素濃度確認〕
前記得られた精製トリクロロシランを用いて多結晶シリコンを製造し、その炭素濃度を測定したところ６１０ｐｐｂモルの含有量で、前記実施例１で製造した精製トリクロロシランから製造した多結晶シリコンよりも相当に高い結果であった。 [Confirmation of carbon concentration in polycrystalline silicon produced using trichlorosilane]
Polycrystalline silicon was produced using the purified trichlorosilane obtained above, and its carbon concentration was measured and found to be 610 ppb mol, which is considerably higher than that of the polycrystalline silicon produced from the purified trichlorosilane produced in Example 1. The results were high.
前記得られた精製トリクロロシランを用いて多結晶シリコンを製造し、その炭素濃度を測定したところ６１０ｐｐｂモルの含有量で、前記実施例１で製造した精製トリクロロシランから製造した多結晶シリコンよりも相当に高い結果であった。 [Confirmation of carbon concentration in polycrystalline silicon produced using trichlorosilane]
Polycrystalline silicon was produced using the purified trichlorosilane obtained above, and its carbon concentration was measured and found to be 610 ppb mol, which is considerably higher than that of the polycrystalline silicon produced from the purified trichlorosilane produced in Example 1. The results were high.
これは実施例１では、第１蒸留塔１４でのイソペンタンの蒸留はメチルジクロロシランの存在下に行われ、この状態では該イソペンタンは共沸化物としても除去されるのに対し、比較例１では、第１蒸留塔１４でのイソペンタンの蒸留は、それより先の第２蒸留塔２０でほとんどのメチルジクロロシランが除去されているため、イソペンタンの共沸化物の除去が不十分であることに起因することが予測された。即ち、メチルジクロロシランの不存在下では、イソペンタンの多くは係るトリクロロシランと共沸化物を形成し、該共沸化物の沸点は、イソペンタンの沸点よりもトリクロロシランの沸点にさらに近似するため、第１蒸留塔１４では十分に除去されず、これにより、たとえ前記実施例１のものと同程度にイソペンタン濃度が低く測定される精製トリクロロシランを用いていても、これにより製造された多結晶シリコンでは共沸化物由来の炭素が存在し、炭素濃度が高い結果が引き起こされるのではないかと推察された。
This is because in Example 1, the distillation of isopentane in the first distillation column 14 is carried out in the presence of methyldichlorosilane, and in this state, the isopentane is also removed as an azeotrope, whereas in Comparative Example 1, the isopentane is removed as an azeotrope. , the distillation of isopentane in the first distillation column 14 is caused by the fact that most of the methyldichlorosilane is removed in the second distillation column 20, and therefore the azeotrope of isopentane is insufficiently removed. It was predicted that That is, in the absence of methyldichlorosilane, most of the isopentane forms an azeotrope with such trichlorosilane, and the boiling point of the azeotrope is more similar to the boiling point of trichlorosilane than the boiling point of isopentane. 1 The distillation column 14 does not sufficiently remove the polycrystalline silicon, so that even if purified trichlorosilane is used, whose isopentane concentration is measured to be as low as that of Example 1, the polycrystalline silicon produced thereby It was speculated that the presence of carbon derived from azeotropes caused the high carbon concentration.
１：粗トリクロロシラン流通管
２：プレ第１蒸留塔
３：四塩化珪素濃縮塔底液抜出管
４：四塩化珪素低減トリクロロシラン留出管
５，１１，１７，２３：凝縮器
６：四塩化珪素低減トリクロロシラン還流管
７：四塩化珪素低減トリクロロシラン供給管
８：プレ第２蒸留塔
９：プレ精製トリクロロシラン抜出管
１０：ジクロロシラン濃縮物留出管
１２：ジクロロシラン濃縮物還流管
１３：ジクロロシラン濃縮物流通管
１４：第１蒸留塔
１５：イソペンタン低減トリクロロシラン抜出管（精製トリクロロシラン抜出管）
１６：イソペンタン濃縮物留出管
１８：イソペンタン濃縮物還流管
１９：イソペンタン濃縮物流通管
２０：第２蒸留塔
２１：メチルジクロロシラン濃縮塔底液抜出管（メチルジクロロシラン低減トリクロロシラン供給管）
２２：精製トリクロロシラン留出管（メチルジクロロシラン低減トリクロロシラン留出管）
２４：精製トリクロロシラン還流管
２５：精製トリクロロシラン流通管 1: Crude trichlorosilane flow pipe 2: Pre-first distillation column 3: Silicon tetrachloride concentration tower bottom liquid extraction pipe 4: Silicon tetrachloride reduced trichlorosilane distillation pipe 5, 11, 17, 23: Condenser 6: Four Silicon chloride-reduced trichlorosilane reflux pipe 7: Silicon tetrachloride-reduced trichlorosilane supply pipe 8: Pre-second distillation column 9: Pre-purified trichlorosilane extraction pipe 10: Dichlorosilane concentrate distillate pipe 12: Dichlorosilane concentrate reflux pipe 13: Dichlorosilane concentrate distribution pipe 14: First distillation column 15: Isopentane-reduced trichlorosilane extraction pipe (purified trichlorosilane extraction pipe)
16: Isopentane concentrate distillation pipe 18: Isopentane concentrate reflux pipe 19: Isopentane concentrate distribution pipe 20: Second distillation column 21: Methyldichlorosilane concentration column bottom liquid extraction pipe (methyldichlorosilane reduced trichlorosilane supply pipe)
22: Purified trichlorosilane distillation tube (methyldichlorosilane reduced trichlorosilane distillation tube)
24: Purified trichlorosilane reflux tube 25: Purified trichlorosilane flow tube
２：プレ第１蒸留塔
３：四塩化珪素濃縮塔底液抜出管
４：四塩化珪素低減トリクロロシラン留出管
５，１１，１７，２３：凝縮器
６：四塩化珪素低減トリクロロシラン還流管
７：四塩化珪素低減トリクロロシラン供給管
８：プレ第２蒸留塔
９：プレ精製トリクロロシラン抜出管
１０：ジクロロシラン濃縮物留出管
１２：ジクロロシラン濃縮物還流管
１３：ジクロロシラン濃縮物流通管
１４：第１蒸留塔
１５：イソペンタン低減トリクロロシラン抜出管（精製トリクロロシラン抜出管）
１６：イソペンタン濃縮物留出管
１８：イソペンタン濃縮物還流管
１９：イソペンタン濃縮物流通管
２０：第２蒸留塔
２１：メチルジクロロシラン濃縮塔底液抜出管（メチルジクロロシラン低減トリクロロシラン供給管）
２２：精製トリクロロシラン留出管（メチルジクロロシラン低減トリクロロシラン留出管）
２４：精製トリクロロシラン還流管
２５：精製トリクロロシラン流通管 1: Crude trichlorosilane flow pipe 2: Pre-first distillation column 3: Silicon tetrachloride concentration tower bottom liquid extraction pipe 4: Silicon tetrachloride reduced
16: Isopentane concentrate distillation pipe 18: Isopentane concentrate reflux pipe 19: Isopentane concentrate distribution pipe 20: Second distillation column 21: Methyldichlorosilane concentration column bottom liquid extraction pipe (methyldichlorosilane reduced trichlorosilane supply pipe)
22: Purified trichlorosilane distillation tube (methyldichlorosilane reduced trichlorosilane distillation tube)
24: Purified trichlorosilane reflux tube 25: Purified trichlorosilane flow tube
Claims (8)
- 少なくとも、イソペンタン及びメチルジクロロシランを含有する粗トリクロロシランを、第１蒸留塔に供給して、イソペンタン濃度が該粗トリクロロシラン中の濃度より１５０倍以上高い低沸点域画分を排出させる態様で蒸留精製して、塔底からイソペンタン濃度が低減されたトリクロロシランを抜き出し、
次いで、得られた前記イソペンタン濃度が低減されたトリクロロシランを第２蒸留塔に供給して、メチルジクロロシラン濃度が前記粗トリクロロシラン中の濃度より１．５倍以上高い高沸点域画分を排出させる態様で蒸留精製して、塔頂からメチルジクロロシラン濃度が低減された精製トリクロロシランを留出させることを特徴とする、精製トリクロロシランの製造方法。 At least, crude trichlorosilane containing isopentane and methyldichlorosilane is supplied to a first distillation column, and distilled in a manner that discharges a low-boiling point fraction whose isopentane concentration is 150 times or more higher than the concentration in the crude trichlorosilane. After purification, trichlorosilane with reduced isopentane concentration is extracted from the bottom of the column.
Next, the obtained trichlorosilane with reduced isopentane concentration is supplied to a second distillation column, and a high boiling point fraction whose methyldichlorosilane concentration is 1.5 times or more higher than the concentration in the crude trichlorosilane is discharged. 1. A method for producing purified trichlorosilane, comprising distilling and purifying it in such a manner that purified trichlorosilane having a reduced concentration of methyldichlorosilane is distilled out from the top of the column. - 前記粗トリクロロシランにおいて、前記イソペンタンの含有量が３０ｐｐｂモル以上であり、前記イソペンタン濃度が低減されたトリクロロシランにおいて、該イソペンタンの含有量が２０ｐｐｂモル以下である、請求項１記載の精製トリクロロシランの製造方法。 The purified trichlorosilane according to claim 1, wherein the isopentane content in the crude trichlorosilane is 30 ppb mol or more, and the isopentane content in the trichlorosilane with reduced isopentane concentration is 20 ppb mol or less. Production method.
- 前記粗トリクロロシランにおいて、前記メチルジクロロシランの含有量が１ｐｐｍモル以上であり、前記メチルジクロロシラン濃度が低減された精製トリクロロシランにおいて、該メチルジクロロシランの含有量が１００ｐｐｂモル以下である、請求項１または請求項２記載の精製トリクロロシランの製造方法。 The content of the methyldichlorosilane in the crude trichlorosilane is 1 ppm mol or more, and the content of the methyldichlorosilane in the purified trichlorosilane with reduced methyldichlorosilane concentration is 100 ppb mol or less. A method for producing purified trichlorosilane according to claim 1 or claim 2.
- 前記粗トリクロロシランが、さらに四塩化珪素及びジクロロシランを含有しており、
前記粗トリクロロシランを第１蒸留塔に供給する前に、下記プレ精製を施してなる、請求項１に記載の精製トリクロロシランの製造方法。
〔プレ精製〕
前記粗トリクロロシランをプレ第１蒸留塔に供給して、四塩化珪素濃度が前記粗トリクロロシラン中の濃度より１．１倍以上高い高沸点域画分を排出させる態様で蒸留精製して、塔頂から四塩化珪素濃度が低減された粗トリクロロシランを留出させ、
次いで、得られた前記四塩化珪素濃度が低減された粗トリクロロシランをプレ第２蒸留塔に供給して、ジクロロシラン濃度が前記粗トリクロロシラン中の濃度より１００倍以上高い低沸点域画分を排出させる態様で蒸留精製して、塔底からジクロロシラン濃度が低減された粗トリクロロシランを抜き出して前記第１蒸留塔に供給する。 The crude trichlorosilane further contains silicon tetrachloride and dichlorosilane,
The method for producing purified trichlorosilane according to claim 1, wherein the crude trichlorosilane is subjected to the following pre-purification before being supplied to the first distillation column.
[Pre-purification]
The crude trichlorosilane is supplied to the pre-first distillation column, and purified by distillation in a manner that discharges a high boiling point fraction in which the silicon tetrachloride concentration is 1.1 times or more higher than the concentration in the crude trichlorosilane. Crude trichlorosilane with reduced silicon tetrachloride concentration is distilled from the top,
Next, the obtained crude trichlorosilane with a reduced silicon tetrachloride concentration is supplied to a pre-second distillation column to obtain a low boiling point fraction whose dichlorosilane concentration is 100 times or more higher than the concentration in the crude trichlorosilane. The crude trichlorosilane having a reduced concentration of dichlorosilane is extracted from the bottom of the column by distillation and purification in a manner that it is discharged, and is supplied to the first distillation column. - 前記粗トリクロロシランにおいて、前記四塩化珪素の含有量が７０モル％以上であり、前記四塩化珪素濃度が低減された粗トリクロロシランにおいて、該四塩化珪素の含有量が１０ｐｐｍモル以下である、請求項４記載の精製トリクロロシランの製造方法。 In the crude trichlorosilane, the silicon tetrachloride content is 70 mol% or more, and in the crude trichlorosilane with a reduced silicon tetrachloride concentration, the silicon tetrachloride content is 10 ppm mol or less. Item 4. The method for producing purified trichlorosilane according to item 4.
- 前記粗トリクロロシランにおいて、前記ジクロロシランの含有量が０．１モル％以上であり、前記ジクロロシラン濃度が低減された粗トリクロロシランにおいて、該ジクロロシランの含有量が１０ｐｐｍモル以下である、請求項４または請求項５記載の精製トリクロロシランの製造方法。 Claim: In the crude trichlorosilane, the content of the dichlorosilane is 0.1 mol% or more, and in the crude trichlorosilane with reduced dichlorosilane concentration, the content of the dichlorosilane is 10 ppm mol or less. 6. The method for producing purified trichlorosilane according to claim 4 or claim 5.
- 前記粗トリクロロシランが、塩化水素または四塩化珪素と、水素と、を含有するガスを、冶金級シリコンと反応させることにより生成されたものである、請求項１記載の精製トリクロロシランの製造方法。 The method for producing purified trichlorosilane according to claim 1, wherein the crude trichlorosilane is produced by reacting a gas containing hydrogen chloride or silicon tetrachloride and hydrogen with metallurgical grade silicon.
- イソペンタンおよびメチルジクロロシランを含み、トリクロロシラン濃度が９９％モル以上である粗トリクロロシランを高純度化して、精製トリクロロシランを製造する方法において、
前記粗クロロシランに対して、前記メチルジクロロシランを除去する蒸留操作を行う前に、前記イソペンタンを除去する蒸留操作を行う精製トリクロロシランの製造方法。 A method for producing purified trichlorosilane by highly purifying crude trichlorosilane containing isopentane and methyldichlorosilane and having a trichlorosilane concentration of 99% molar or more,
A method for producing purified trichlorosilane, comprising performing a distillation operation to remove the isopentane on the crude chlorosilane before performing a distillation operation to remove the methyldichlorosilane.
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Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH06211882A (en) * | 1993-01-11 | 1994-08-02 | Wacker Chemie Gmbh | Method for dividing azeotropic tetrachlorosilane- trimethylchlorosilane mixture by distillation |
| JP2004149351A (en) * | 2002-09-04 | 2004-05-27 | Sumitomo Titanium Corp | Chlorosilane and method for purifying the same |
| JP2009062212A (en) * | 2007-09-05 | 2009-03-26 | Shin Etsu Chem Co Ltd | Method for producing trichlorosilane and method for producing polycrystalline silicon |
| WO2020137853A1 (en) * | 2018-12-27 | 2020-07-02 | 株式会社トクヤマ | Chlorosilane manufacturing method |
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- 2023-06-05 WO PCT/JP2023/020839 patent/WO2023243466A1/en unknown
Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH06211882A (en) * | 1993-01-11 | 1994-08-02 | Wacker Chemie Gmbh | Method for dividing azeotropic tetrachlorosilane- trimethylchlorosilane mixture by distillation |
| JP2004149351A (en) * | 2002-09-04 | 2004-05-27 | Sumitomo Titanium Corp | Chlorosilane and method for purifying the same |
| JP2009062212A (en) * | 2007-09-05 | 2009-03-26 | Shin Etsu Chem Co Ltd | Method for producing trichlorosilane and method for producing polycrystalline silicon |
| WO2020137853A1 (en) * | 2018-12-27 | 2020-07-02 | 株式会社トクヤマ | Chlorosilane manufacturing method |
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