Chlorosilane raw material purification system for reducing donor and acceptor impurities in polycrystalline silicon

Abstract

The utility model discloses a chlorosilane raw material purification system for reducing donor and acceptor impurities in polycrystalline silicon, which belongs to the technical field of polycrystalline silicon production and comprises a first rectifying tower, the first rectifying tower is connected with a chlorosilane raw material pipe, a first silicon tetrachloride outlet pipe and a first connecting pipe, and the first connecting pipe is connected with a second rectifying tower. The second rectifying tower is connected with a second connecting pipe and a third connecting pipe, the second connecting pipe is connected with a third rectifying tower, the third rectifying tower is connected with a fourth connecting pipe and a fifth connecting pipe, the fourth connecting pipe is connected with a fourth rectifying assembly, and the fourth rectifying assembly is connected with a product liquid outlet pipe and a chlorosilane raw material tank; the fifth connecting pipe is connected with the first cooler and the first adsorber, and the first adsorber is connected with the chlorosilane raw material tank. According to the utility model, high-purity trichlorosilane is obtained; dichlorosilane in the chlorosilane raw material reacts with silicon tetrachloride in the reactor to obtain trichlorosilane, so that the utilization rate of chlorosilane is further increased.

Description

Technical Field

[0001] The utility model belongs to the technical field of polysilicon production, and particularly relates to a purification system for chlorosilane raw materials that reduces donor and acceptor impurities in polysilicon. Background Art

[0002] High-purity polysilicon is usually manufactured by using a CVD method called the "Siemens method" with chlorosilane gases mainly composed of trichlorosilane as raw materials in a hydrogen atmosphere. Therefore, the chlorosilanes as raw materials for high-purity polysilicon are also required to have extremely high purity.

[0003] In particular, when the impurities contained in the raw material chlorosilanes are impurities such as phosphorus and arsenic that are donors in silicon crystals or impurities such as boron and aluminum that are acceptors, even if these impurities are trace amounts, they will have a significant impact on the electrical properties (resistivity) of the manufactured polysilicon. Therefore, providing a technology for efficiently removing donor impurities and acceptor impurities contained in raw material chlorosilanes and achieving high purity is of great significance in practical applications.

[0004] Generally, chlorosilanes for polysilicon production are manufactured by the following method: obtaining a chlorosilane distillate from metallurgical-grade silicon (so-called metal-grade silicon, hereinafter referred to as "metallic silicon") containing a relatively large amount of impurities by a known method, and then further purifying the chlorosilane distillate by methods such as distillation to achieve high purity.

[0005] However, generally, the above-mentioned donor impurities and acceptor impurities are contained in metallic silicon at levels of several hundred ppb (atoms) to several hundred ppm (atoms) in terms of atomic ratio. Therefore, the following problems occur: these impurities are not sufficiently removed during the purification process of the chlorosilane distillate, and donor impurities and acceptor impurities remain in the finally obtained chlorosilanes, and these residual impurities reduce the quality of polysilicon.

[0006] As a method for obtaining a chlorosilane distillate, a hydrogenation step is known in which a substance containing silicon tetrachloride (SiCl4) reacts with hydrogen in the presence of metallic silicon to obtain a chlorosilane distillate containing trichlorosilane (SiHCl3) (for example, refer to Japanese Patent Application Laid-Open No. 2008-532907 (Patent Document 1), Japanese Patent Application Laid-Open No. 58-217422 (Patent Document 2), Japanese Patent Application Laid-Open No. 58-161915 (Patent Document 3), etc.).

[0007] This hydrogenation reaction proceeds according to the following reaction formula.

[0008] 3SiC14 + 2H2 + Si → 4SiHC13 [Formula 1]

[0009] Chlorosilane distillates are fractions of crude chlorosilanes as products synthesized by hydrogenation reactions, and are generally mixtures mainly composed of chlorosilanes such as dichlorosilane (SiH2Cl2), trichlorosilane (SiHCl3), and tetrachlorosilane (SiCl4).

[0010] In addition, as another method for obtaining chlorosilane distillates, a chlorination process is also known in which metallic silicon is brought into contact with hydrogen chloride in the presence of a catalyst to carry out a chlorination reaction to obtain a chlorosilane distillate containing trichlorosilane (for example, refer to Japanese Patent Laid-Open No. 2005-67979 (Patent Document 4)).

[0011] This chlorination reaction proceeds according to the following reaction formula.

[0012] Si + 3HCl → SiHCl3 + H2 [Formula 2]

[0013] Chlorosilane distillates are fractions of crude chlorosilanes as products synthesized by chlorination reactions. In this case, they are generally also mixtures mainly composed of chlorosilanes such as dichlorosilane, trichlorosilane, and tetrachlorosilane.

[0014] It is generally considered that donor impurities and acceptor impurities contained in metallic silicon are simultaneously hydrogenated, chlorinated, etc. during the formation of crude chlorosilanes and are mixed into the crude chlorosilanes in the form of compounds with various structures. Although high-purity chlorosilanes can be obtained by purifying such crude chlorosilanes, it is difficult to separate and remove these impurities by general distillation methods when the boiling points of compounds of donor impurities and acceptor impurities are close to the boiling point of trichlorosilane.

[0015] Moreover, when using chlorosilanes in which donor impurities and acceptor impurities have not been sufficiently removed as raw materials to manufacture polysilicon, polysilicon with desired properties cannot be obtained as a result.

[0016] Based on the above circumstances, various methods have been proposed as methods for removing donor impurities and acceptor impurities in chlorosilane distillates. For example, a method has been proposed in which an organic substance is added to the chlorosilane distillate to form an adduct with the donor impurity or acceptor impurity, and then distillation purification is carried out to obtain high-purity chlorosilanes.

[0017] Specifically, Japanese Patent Laid-Open No. 2005-67979 (Patent Document 4) discloses a method of adding an ether to a chlorosilane and performing distillation purification. In addition, U.S. Patent No. 3126248 (Patent Document 5) discloses a method of removing impurities by adding an organic compound containing a dialkane, benzaldehyde, methyl ethyl ketone, dimethylglyoxime, and valerolactone. Further, Japanese Patent Laid-Open No. 2009-62213 (Patent Document 6) discloses the following method: reacting a chlorosilane with oxygen in the presence of benzaldehyde to convert impurities into high-boiling compounds, and subjecting the treated chlorosilane to distillation or the like to separate the high-boiling compounds as impurities and the chlorosilane.

[0018] In addition, the following method has also been proposed: adding a metal chloride to a chlorosilane distillate to form an adduct with a donor impurity or an acceptor impurity, and then performing distillation purification to obtain high-purity chlorosilanes.

[0019] Specifically, U.S. Patent No. 2821460 (Patent Document 7) discloses a method of adding aluminum chloride to a chlorosilane to form an AlCl3·PCl5 complex and then performing distillation purification. In addition, Japanese Patent Laid-Open No. 4-300206 (Patent Document 8) discloses a method of adding a high-concentration aqueous solution of an inorganic salt such as TiCl4 to hydrolyze impurities to form high-boiling compounds and then performing distillation purification.

[0020] In addition, a method of adsorbing impurities contained in a chlorosilane onto alumina, silica gel, activated carbon, or the like to remove them has also been proposed.

[0021] Specifically, U.S. Patent No. 3252752 (Patent Document 9) discloses the following method: fixing a substance having a lone pair of electrons (for example, a substance such as propionitrile having a nitrogen atom or benzaldehyde having an oxygen atom) to an adsorbent such as activated carbon or silica gel, and passing a chlorosilane gas through it to capture and remove impurities. In addition, German Patent No. 1289834 (Patent Document 10) discloses a method of removing impurities by bringing a chlorosilane into contact with activated alumina in a liquid or vapor state. Further, U.S. Patent No. 4112057 (Patent Document 11) discloses a method of removing impurities by bringing a chlorosilane into contact with a hydrated silica gel, alumina gel, or other metal oxides. Japanese Patent Laid-Open No. 2001-2407 (Patent Document 12) discloses a method of removing impurities by bringing a chlorosilane into contact with a fluoride salt of an alkali metal or an alkaline earth metal.

[0022] In addition to these methods, the following method has also been proposed: A small amount of oxygen is introduced into silanes under high-temperature conditions to react and form a complex. A new complex is formed by the reaction of this complex with a donor impurity or an acceptor impurity, and it is separated in the distillation process of silanes, thereby obtaining silanes with a low impurity concentration (refer to Japanese Patent Publication No. 58-500895 (Patent Document 13)).

[0023] Prior Art Documents

[0024] Patent Documents

[0025] Patent Document 1: Japanese Patent Publication No. 2008-532907

[0026] Patent Document 2: Japanese Unexamined Patent Application Publication No. 58-217422

[0027] Patent Document 3: Japanese Unexamined Patent Application Publication No. 58-161915

[0028] Patent Document 4: Japanese Unexamined Patent Application Publication No. 2005-67979

[0029] Patent Document 5: U.S. Patent No. 3126248 Specification

[0030] Patent Document 6: Japanese Unexamined Patent Application Publication No. 2009-62213

[0031] Patent Document 7: U.S. Patent No. 2821460 Specification

[0032] Patent Document 8: Japanese Unexamined Patent Application Publication No. 4-300206

[0033] Patent Document 9: U.S. Patent No. 3252752 Specification

[0034] Patent Document 10: German Patent No. 1289834 Specification

[0035] Patent Document 11: U.S. Patent No. 4112057 Specification

[0036] Patent Document 12: Japanese Unexamined Patent Application Publication No. 2001-2407

[0037] Patent Document 13: Japanese Patent Publication No. 58-500895 Summary of the Utility Model

[0038] The above technical route has the problem that other substances are introduced, which will generate other substances from the donor and acceptor impurities, and the subsequent treatment is complicated. The present utility model provides a purification system for chlorosilane raw materials to reduce donor and acceptor impurities in polysilicon. The chlorosilane raw materials produced in the cold hydrogeneration or trichlorosilane synthesis process are subjected to the first rectification separation, the second rectification separation, the third rectification separation, and the fourth rectification separation through the first rectification tower, the second rectification tower, the third rectification tower, and the fourth rectification component to obtain high-purity trichlorosilane (the concentration of trichlorosilane is greater than 99.9%); dichlorosilane and silicon tetrachloride in the chlorosilane raw materials react in a reactor to obtain trichlorosilane, further improving the utilization rate of chlorosilane (the theoretical utilization rate of chlorosilane raw materials is 100%, realizing closed-loop use of raw materials); the first adsorber removes B / P impurities existing in the form of heavy components (the removal rate of B / P impurities in the form of heavy components > 90%), and the second adsorber removes B / P impurities existing in the form of light components (the removal rate of B / P impurities in the form of light components > 90%).

[0039] The purpose of the present utility model is achieved through the following technical solutions:

[0040] A purification system for chlorosilane raw materials to reduce donor and acceptor impurities in polysilicon, including a first rectification tower, the first rectification tower is connected to a chlorosilane raw material pipe, a first silicon tetrachloride outlet pipe, and a first connecting pipe, the first connecting pipe is connected to a second rectification tower, the second rectification tower is connected to a second connecting pipe and a third connecting pipe, the second connecting pipe is connected to a third rectification tower, the third rectification tower is connected to a fourth connecting pipe and a fifth connecting pipe, the fourth connecting pipe is connected to a fourth rectification component, the fourth rectification component is connected to a product liquid outlet pipe and a chlorosilane raw material tank; the fifth connecting pipe is connected to a first cooler and a first adsorber, and the first adsorber is connected to the chlorosilane raw material tank.

[0041] Preferably, the third connecting pipe and a silicon tetrachloride inlet pipe are connected to a mixer, the mixer is connected to a reactor through a sixth connecting pipe, the reactor is connected to a fifth rectification tower through a seventh connecting pipe, the fifth rectification tower is connected to an eighth connecting pipe and a ninth connecting pipe, the eighth connecting pipe is connected to a second cooler and a second adsorber, and the second adsorber is connected to the chlorosilane raw material tank.

[0042] Preferably, the fourth rectification component includes at least one rectification tower.

[0043] Preferably, the first silicon tetrachloride outlet pipe is connected to a silicon tetrachloride raw material tank.

[0044] Preferably, a feeding pump is provided on the sixth connecting pipe.

[0045] Preferably, the mixer adopts a pipeline mixer.

[0046] Preferably, the number of theoretical plates of the first distillation column is 80 - 160, the number of theoretical plates of the second distillation column is 80 - 160, the number of theoretical plates of the third distillation column is 80 - 160, and the number of theoretical plates of the distillation column in the fourth distillation assembly is 80 - 160.

[0047] Preferably, the number of plates of the fifth distillation column is 80 - 160.

[0048] Preferably, the adsorbents of the first adsorber and the second adsorber are silica gel, alumina or amino resin.

[0049] Preferably, the catalyst of the reactor is amino anion exchange resin.

[0050] The beneficial effects of this technical solution are as follows:

[0051] 1. A chlorosilane raw material purification system for reducing donor and acceptor impurities in polysilicon provided by the present utility model. The chlorosilane raw material produced in the cold hydrogenation or trichlorosilane synthesis process undergoes first distillation separation, second distillation separation, third distillation separation, and fourth distillation separation through the first distillation column, the second distillation column, the third distillation column, and the fourth distillation assembly to obtain high-purity trichlorosilane (the concentration of trichlorosilane is greater than 99.9%); dichlorodihydrogen silane and silicon tetrachloride in the chlorosilane raw material react in the reactor to obtain trichlorosilane, further improving the utilization rate of chlorosilane (the theoretical utilization rate of chlorosilane raw material is 100%, realizing the closed-loop use of raw materials); the first adsorber removes B / P impurities existing in the form of heavy components (the removal rate of B / P impurities in the form of heavy components > 90%), and the second adsorber removes B / P impurities existing in the form of light components (the removal rate of B / P impurities in the form of light components > 90%).

[0052] 2. A chlorosilane raw material purification system for reducing donor and acceptor impurities in polysilicon provided by the present utility model uses the purification effect of the distillation column to concentrate B / P impurities in the chlorosilane raw material to a higher concentration, and then uses the adsorption effect of the adsorbent to adsorb the B / P impurities with a higher concentration, separating the impurities from the chlorosilane raw material, thereby reducing the impurity content in the chlorosilane. The B / P impurities can be reduced to the PPB level or even to the PPT level, and the polysilicon produced with this chlorosilane reaches the electronic grade. BRIEF DESCRIPTION OF THE DRAWINGS

[0053] Figure 1 is a schematic structural diagram of the present utility model;

[0054] Wherein: 1. The first rectification column; 2. The chlorosilane raw material pipe; 3. The first silicon tetrachloride outlet pipe; 4. The first connecting pipe; 5. The second rectification column; 6. The second connecting pipe; 7. The third connecting pipe; 8. The third rectification column; 9. The fourth connecting pipe; 10. The fifth connecting pipe; 12. The fourth rectification assembly; 13. The product liquid outlet pipe; 14. The chlorosilane raw material tank; 15. The first adsorber; 16. The silicon tetrachloride inlet pipe; 17. The mixer; 18. The sixth connecting pipe; 19. The reactor; 20. The seventh connecting pipe; 21. The fifth rectification column; 22. The eighth connecting pipe; 23. The ninth connecting pipe; 24. The second adsorber; 25. The silicon tetrachloride raw material tank; 26. The feeding pump; 27. The first cooler; 28. The second cooler. Detailed implementation manners

[0055] The present utility model will be further described in detail below in conjunction with embodiments, but the implementation manners of the present utility model are not limited thereto.

[0056] Embodiment 1

[0057] As Figure 1 shown, a chlorosilane raw material purification system for reducing donor and acceptor impurities in polysilicon includes a first rectification column 1, the first rectification column 1 is connected to a chlorosilane raw material pipe 2, a first silicon tetrachloride outlet pipe 3 and a first connecting pipe 4, the first connecting pipe 4 is connected to a second rectification column 5, the second rectification column 5 is connected to a second connecting pipe 6 and a third connecting pipe 7, the second connecting pipe 6 is connected to a third rectification column 8, the third rectification column 8 is connected to a fourth connecting pipe 9 and a fifth connecting pipe 10, the fourth connecting pipe 9 is connected to a fourth rectification assembly 12, the fourth rectification assembly 12 is connected to a product liquid outlet pipe 13 and a chlorosilane raw material tank 14; the fifth connecting pipe 10 is connected to a first cooler 27 and a first adsorber 15, and the first adsorber 15 is connected to the chlorosilane raw material tank 14.

[0058] Embodiment 2

[0059] The difference between this embodiment and Embodiment 1 is that: wherein, the third connecting pipe 7 and the silicon tetrachloride inlet pipe 16 are connected to a mixer 17, the mixer 17 is connected to a reactor 19 through a sixth connecting pipe 18, the reactor 19 is connected to a fifth rectification column 21 through a seventh connecting pipe 20, the fifth rectification column 21 is connected to an eighth connecting pipe 22 and a ninth connecting pipe 23, the eighth connecting pipe 22 is connected to a second cooler 28 and a second adsorber 24, and the second adsorber 24 is connected to the chlorosilane raw material tank 14; the ninth connecting pipe 23 is connected to a silicon tetrachloride raw material tank 25.

[0060] Wherein, the fourth rectification assembly 12 includes at least one rectification column.

[0061] Among them, the first silicon tetrachloride outlet pipe 3 is connected to the silicon tetrachloride raw material tank 25.

[0062] Among them, a feeding pump 26 is arranged on the sixth connecting pipe 18.

[0063] Among them, the mixer 17 adopts a pipeline mixer 17.

[0064] Among them, the number of theoretical plates of the first distillation column 1 is 80 - 160, the number of theoretical plates of the second distillation column 5 is 80 - 160, the number of theoretical plates of the third distillation column 8 is 80 - 160, and the number of theoretical plates of the distillation column in the fourth distillation assembly 12 is 80 - 160.

[0065] Among them, the number of plates of the fifth distillation column 21 is 80 - 160.

[0066] Among them, the adsorbents of the first adsorber 15 and the second adsorber 24 adopt silica gel or alumina or amino resin.

[0067] Among them, the catalyst of the reactor 19 adopts amino anion exchange resin.

[0068] When this system is in use, it includes the following steps:

[0069] Step 1: The chlorosilane raw material enters the first distillation column 1 for the first distillation separation. The bottoms product of the first distillation column 1 flows into the silicon tetrachloride raw material tank 25, and the overhead product of the first distillation column 1 flows into the second distillation column 5;

[0070] Step 2: The overhead product of the first distillation column 1 undergoes the second distillation separation in the second distillation column 5. The bottoms product of the second distillation column 5 flows into the third distillation column 8, and the overhead product of the second distillation column 5 flows into the mixer 17;

[0071] Step 31: The bottoms product of the second distillation column 5 undergoes the third distillation separation in the third distillation column 8. The overhead product of the third distillation column 8 flows into the fourth distillation assembly 12;

[0072] Step 411: The overhead product of the third distillation column 8 undergoes the fourth distillation separation in the fourth distillation assembly 12. The bottoms product of the fourth distillation assembly 12 flows into the chlorosilane storage tank, and the overhead product of the fourth distillation assembly 12 obtains the product liquid;

[0073] Step 412: The bottoms product of the third distillation column 8 undergoes impurity removal by adsorption in the first adsorber 15 and then flows into the chlorosilane storage tank after impurity removal.

[0074] Among them, it also includes the following steps:

[0075] Step 32: The overhead product of the second distillation column 5 and silicon tetrachloride are mixed in the mixer 17; after mixing, they flow into the reactor 19;

[0076] Step 42: The reaction solution obtained from the reaction flows into the fifth distillation column 21 for the fifth distillation separation. The bottom product of the fifth distillation column 21 flows into silicon tetrachloride, and the top product of the fifth distillation column 21 flows into the second adsorber 24.

[0077] Step 43: The top product of the fifth distillation column 21 is subjected to impurity removal by adsorption in the second adsorber 24, and then flows into the chlorosilane storage tank after impurity removal.

[0078] Among them, in the above step 1, the chlorosilane raw material is the chlorosilane raw material produced by the cold hydrogenation or trichlorosilane synthesis process. The temperature of the chlorosilane raw material is 40°C, where the mass content of trichlorosilane is 25%, the mass content of dichlorodihydrogen silane is 0.5%, the mass content of silicon tetrachloride is 74.5%, and there are a small amount of chlorosilane polymers and donor and acceptor impurities.

[0079] Among them, the number of theoretical plates of the first distillation column 1 is 80, the top reflux ratio of the first distillation column 1 is 6, the tower pressure of the first distillation column 1 is 0.8 MpaG, the temperature at the top of the first distillation column 1 is 112°C, and the temperature at the bottom of the first distillation column 1 is 147°C; the number of theoretical plates of the second distillation column 5 is 80, the feed reflux ratio of the second distillation column 5 is 4, the tower pressure of the second distillation column 5 is 0.5 MpaG, the temperature at the top of the second distillation column 5 is 72°C, and the temperature at the bottom of the second distillation column 5 is 96°C; the number of theoretical plates of the third distillation column 8 is 80, the top reflux ratio of the third distillation column 8 is 7, the tower pressure of the third distillation column 8 is 0.8 MpaG, the temperature at the top of the third distillation column 8 is 113°C, and the temperature at the bottom of the third distillation column 8 is 119°C; the number of theoretical plates of the distillation column of the fourth distillation assembly 12 is 80, the feed reflux ratio of the distillation column of the fourth distillation assembly 12 is 5, the tower pressure of the distillation column of the fourth distillation assembly 12 is 0.8 MpaG, the temperature at the top of the distillation column of the fourth distillation assembly 12 is 113°C, and the temperature at the bottom of the distillation column of the fourth distillation assembly 12 is 119°C; the temperature in the first adsorber 15 is 30°C, and the residence time of the bottom product of the third distillation column 8 in the first adsorber 15 is 1 h.

[0080] Among them, the mass feed ratio of silicon tetrachloride to the top product of the second distillation column 5 is 2.5: The inlet temperature of silicon tetrachloride is 65°C, and the temperature after mixing is 65°C; after mixing, it flows into the reactor 19 for reaction. The temperature of the reactor 19 is 70°C, and the pressure of the reactor 19 is 0.6 MpaG; the number of plates of the fifth distillation column 21 is 80, the top reflux ratio of the fifth distillation column 21 is 6, the tower pressure of the fifth distillation column 21 is 0.5 MpaG, the temperature at the top of the fifth distillation column 21 is 95°C, and the temperature at the bottom of the fifth distillation column 21 is 133°C; the temperature in the second adsorber 24 is 30°C, and the residence time of the top product of the fifth distillation column 21 in the second adsorber 24 is 1 h.

[0081] The concentration of trichlorosilane in the product liquid is 99.9%, and the content of B / P impurities is at the PPB level (<0.5 PPB).

[0082] The content of B / P impurities in the bottom draw of the third distillation column 8 is >50 PPB, and after adsorption and impurity removal in the first adsorber 15, the content of B / P impurities is <5 PPB.

[0083] The content of B / P impurities in the top draw of the fifth distillation column 21 is >50 PPB. After adsorption and impurity removal in the second adsorber 24, the concentration of trichlorosilane is 95% (the rest is unreacted dichlorosilane), and the content of B / P impurities is <5 PPB.

[0084] The utilization rate of the chlorosilane raw material is 100%.

[0085] A chlorosilane raw material purification system for reducing donor and acceptor impurities in polysilicon provided by the present utility model. The chlorosilane raw material produced in the cold hydrogeneration or trichlorosilane synthesis process undergoes the first distillation separation, the second distillation separation, the third distillation separation, and the fourth distillation separation through the first distillation column 1, the second distillation column 5, the third distillation column 8, and the fourth distillation assembly 12 to obtain high-purity trichlorosilane (the concentration of trichlorosilane is greater than 99.9%); dichlorosilane and silicon tetrachloride in the chlorosilane raw material react in the reactor 19 to obtain trichlorosilane, further improving the utilization rate of the chlorosilane (the theoretical utilization rate of the chlorosilane raw material is 100%, realizing the closed-loop use of the raw material); the first adsorber 15 removes B / P impurities existing in the form of heavy components (the removal rate of B / P impurities in the form of heavy components is >90%), and the second adsorber 24 removes B / P impurities existing in the form of light components (the removal rate of B / P impurities in the form of light components is >90%).

[0086] A chlorosilane raw material purification system for reducing donor and acceptor impurities in polysilicon provided by the present utility model. By using the purification effect of the distillation column, the B / P impurities in the chlorosilane raw material are concentrated to a higher concentration, and then the adsorption effect of the adsorbent is used to adsorb the B / P impurities with a higher concentration, separating the impurities from the chlorosilane raw material, thereby reducing the impurity content in the chlorosilane. The B / P impurities can be reduced to the PPB level or even to the PPT level, and the polysilicon produced with this chlorosilane reaches the electronic grade.

[0087] The above are only the preferred embodiments of the present utility model, and do not impose any form of limitation on the present utility model. Any simple modification or equivalent change made to the above embodiments based on the technical essence of the present utility model shall fall within the protection scope of the present utility model.

Claims

1. A purification system for chlorosilane raw materials to reduce donor and acceptor impurities in polysilicon, characterized in that: It includes a first rectification tower (1), which is connected to a chlorosilane raw material pipe (2), a first silicon tetrachloride outlet pipe (3) and a first connecting pipe (4). The first connecting pipe (4) is connected to a second rectification tower (5). The second rectification tower (5) is connected to a second connecting pipe (6) and a third connecting pipe (7). The second connecting pipe (6) is connected to a third rectification tower (8). The third rectification tower (8) is connected to a fourth connecting pipe (9) and a fifth connecting pipe (10). The fourth connecting pipe (9) is connected to a fourth rectification assembly (12). The fourth rectification assembly (12) is connected to a product liquid outlet pipe (13) and a chlorosilane raw material tank (14). The fifth connecting pipe (10) is connected to a first cooler (27) and a first adsorber (15). The first adsorber (15) is connected to the chlorosilane raw material tank (14).

2. The purification system for chlorosilane raw materials to reduce donor and acceptor impurities in polysilicon according to claim 1, wherein: The third connecting pipe (7) and a silicon tetrachloride inlet pipe (16) are connected to a mixer (17). The mixer (17) is connected to a reactor (19) through a sixth connecting pipe (18). The reactor (19) is connected to a fifth rectification tower (21) through a seventh connecting pipe (20). The fifth rectification tower (21) is connected to an eighth connecting pipe (22) and a ninth connecting pipe (23). The eighth connecting pipe (22) is connected to a second cooler (28) and a second adsorber (24). The second adsorber (24) is connected to the chlorosilane raw material tank (14).

3. A purification system for chlorosilane raw materials to reduce donor and acceptor impurities in polysilicon according to claim 2, characterized in that: The fourth rectification assembly (12) includes at least one rectification tower.

4. A chlorosilane raw material purification system for reducing donor and acceptor impurities in polysilicon according to claim 3, characterized in that: The first silicon tetrachloride outlet pipe (3) is connected to a silicon tetrachloride raw material tank (25).

5. A purification system for chlorosilane raw materials to reduce donor and acceptor impurities in polysilicon according to claim 4, characterized in that: A feed pump (26) is arranged on the sixth connecting pipe (18).

6. The purification system for chlorosilane raw materials to reduce donor and acceptor impurities in polysilicon according to claim 5, wherein: The mixer (17) adopts a pipeline mixer.

7. A purification system for chlorosilane raw materials for reducing donor and acceptor impurities in polysilicon according to claim 6, characterized in that: The number of theoretical plates of the first rectification tower (1) is 80 - 160, the number of theoretical plates of the second rectification tower (5) is 80 - 160, the number of theoretical plates of the third rectification tower (8) is 80 - 160, and the number of theoretical plates of the rectification tower in the fourth rectification assembly (12) is 80 - 160.

8. A purification system for chlorosilane raw materials for reducing donor and acceptor impurities in polysilicon according to claim 7, characterized in that: The number of plates of the fifth rectification tower (21) is 80 - 160.

9. The purification system of chlorosilane raw materials for reducing donor and acceptor impurities in polysilicon according to claim 8, characterized in that: The adsorbents of the first adsorber and the second adsorber adopt silica gel or alumina or amino resin.

10. A chlorosilane raw material purification system for reducing donor and acceptor impurities in polysilicon according to claim 9, characterized in that: The catalyst of the reactor (19) adopts an amino anion exchange resin.

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