Method for removing trace boron and phosphorus impurities in trichlorosilane

Abstract

The invention discloses a method for removing trace boron and phosphorus impurities in trichlorosilane, which belongs to the technical field of chlorosilane purification, and comprises the following steps: adding a complexing agent into crude liquid trichlorosilane, carrying out complexation reaction, and rectifying the mixture obtained by the reaction to obtain the purified trichlorosilane, the cyclic siloxane and the chain siloxane have the advantages that the stability is high, new impurities are not easy to introduce, the compatibility with chlorosilane is good, and the like, so that ppb-level boron and phosphorus impurities can be efficiently removed; the trichlorosilane purified by the method is suitable for production of electronic-grade polycrystalline silicon.

Description

Technical Field

[0001] This invention belongs to the field of chlorosilane purification technology, and particularly relates to a method for removing trace boron and phosphorus impurities from trichlorosilane. Background Technology

[0002] Polysilicon is a crucial raw material for the photovoltaic and electronics industries, widely used in the production of transistors, integrated circuits, computer chips, and solar cells. In recent years, my country's polysilicon production capacity and output have continued to increase, with an output growth rate exceeding 100% between 2017 and 2021, indicating a promising future for the polysilicon industry. Based on purity, polysilicon can be classified into metallurgical grade, solar grade, and electronic grade. Metallurgical grade polysilicon has a purity between 95% and 99.8%, solar grade polysilicon between 4N and 6N, and electronic grade polysilicon between 6N and 9N. Despite the rapid expansion of my country's polysilicon production capacity, solar grade production is dominant, while electronic grade polysilicon is primarily reliant on imports. my country's electronic grade polysilicon industry is facing development bottlenecks and urgently needs enterprises, universities, and research institutions to increase R&D investment in electronic grade products and strengthen production process and product quality management to achieve import substitution for electronic grade polysilicon as soon as possible.

[0003] Currently, there are many production processes for polysilicon, but the main method is the modified Siemens process. The modified Siemens process is the third generation of Siemens polysilicon production technology. After two generations of continuous innovation and optimization, over 85% of polysilicon is now produced using this process. The modified Siemens process mainly includes steps such as trichlorosilane synthesis, trichlorosilane purification, trichlorosilane reduction, tail gas recovery, and trichlorosilane oxidation. This method uses industrial silicon powder as raw material, inevitably introducing impurities such as metals, boron (B), and phosphorus (P) into the trichlorosilane, affecting the quality of the polysilicon. During the trichlorosilane refining process, metallic impurities can be removed by direct distillation. However, impurities existing in the form of boron trichloride and phosphorus trichloride have properties similar to chlorosilanes, making them difficult to remove using common physical methods.

[0004] Currently, the main methods for removing boron and phosphorus impurities from trichlorosilane are adsorption and complexation. The complexation method, based on Lewis acid-base theory, defines the electron donor as the base and the electron acceptor as the acid. The acid and base components can combine through coordinate bonds to form a complex without electron transfer. Boron impurities, represented by BCl3, are mostly electron acceptors, while phosphorus impurities, represented by PCl3, are mostly electron donors. They can be reacted with complexing agents according to Lewis acid-base theory to form high-boiling-point compounds, which can then be removed by other methods. However, boron impurities (such as BCl3) and phosphorus impurities (such as PCl3) have opposite electrical properties. A single complexing agent can usually only efficiently capture one type. To simultaneously and deeply remove both, two or more composite complexing agents may be needed, complicating the process. Chlorosilanes (such as SiHCl3) themselves also possess weak Lewis acidity. If the complexing agent is too basic (such as certain amines or phosphines), it will not only react with BCl3, but may also undergo varying degrees of coordination or reaction with the main product SiHCl3, leading to silane loss, decreased yield, and even unnecessary side reactions. Some Lewis acid-base complexing reactions are reversible; during subsequent distillation or heating, the complex may dissociate, releasing impurities again, resulting in rework or incomplete purification.

[0005] Therefore, finding efficient complexing agents that do not react with chlorosilanes (such as SiHCl3) and do not release impurities again is the most important part of the complexation process. Summary of the Invention

[0006] To address the aforementioned technical problems, this invention proposes a method for removing trace boron and phosphorus impurities from trichlorosilane, overcoming the drawbacks of traditional distillation, such as low efficiency in removing B and P, complex operation, high cost, and easy increase in organic carbon content in polycrystalline silicon.

[0007] To achieve the above objectives, the present invention provides a method for removing trace boron and phosphorus impurities from trichlorosilane, comprising the following steps: adding a complexing agent to crude liquid trichlorosilane to carry out a complexing reaction, and then distilling the mixture obtained from the reaction, the distillate being the purified trichlorosilane. The complexing agent is selected from at least one of cyclic siloxanes and chain polysiloxanes; The general formula for the cyclic siloxane is (R¹R²SiO). n , where R 1 R 2 Independently selected from methyl or vinyl, n=3~5; The general formula of the chain siloxane is R 3 Si-O-SiR 3 , where R 3 It is independently selected from methyl or phenyl.

[0008] In the process of removing impurities using the complexation method, additional substances may introduce carbon-containing impurities into the original chlorosilane system. The cyclic and chain siloxanes used in this invention have low carbon content, significantly reducing the risk of increased organic carbon content due to the introduction of organic complexing agents. The cyclic and chain siloxanes used in this invention have high solubility in trichlorosilane, react uniformly, and are less prone to solid precipitation and equipment clogging. Furthermore, the cyclic and chain siloxanes used in this invention, the complexation products, and trichlorosilane have significantly different boiling points; efficient separation of the complexation products from trichlorosilane can be achieved through simple distillation, resulting in a high-purity trichlorosilane product suitable for continuous industrial production.

[0009] Furthermore, the cyclic siloxane is selected from hexamethylcyclotrisiloxane, octamethylcyclotetrasiloxane, decamethylcyclopentasiloxane, or 2,4,6,8-tetramethyl-2,4,6,8-tetravinylcyclotetrasiloxane.

[0010] Furthermore, the chain siloxane is selected from 1,1,3,3-tetramethyl-1,3-diphenyldisiloxane.

[0011] Further, the mass ratio of the crude liquid trichlorosilane to the complexing agent is (100~1050):1; preferably, the mass ratio of the crude liquid trichlorosilane to the complexing agent is (500~1050):1.

[0012] Furthermore, the complexation reaction is carried out at room temperature, at a pressure of 0.1 MPa, and for 1 hour.

[0013] Furthermore, the distillation temperature is 55℃~90℃, preferably 65℃~70℃.

[0014] Furthermore, when the complexing agent is a mixture of cyclic siloxanes and chain siloxanes, the mass ratio of the cyclic siloxanes to the chain siloxanes is (1~10):1; preferably (1~2):1.

[0015] Compared with the prior art, the present invention has the following advantages and technical effects: (1) High efficiency in removing boron and phosphorus impurities: The siloxane complexing agent used in this invention exhibits extremely high complexing ability for ppb-level boron and phosphorus impurities in trichlorosilane. It can generally reduce the impurity concentration from 150ppb to about 10ppb. The best can achieve a boron concentration of 1.02ppb and a phosphorus concentration of 6.34ppb in trichlorosilane, with a boron removal rate of 99.3%.

[0016] (2) Avoid secondary pollution: The siloxane complexing agent selected in this invention has a silicon-oxygen framework structure and low carbon content, which effectively avoids the problem of increased organic carbon content in the final polycrystalline silicon product due to the introduction of organic complexing agents.

[0017] (3) Synergistic effect: By combining cyclic siloxanes and chain siloxanes, this invention utilizes their different electronic structures and spatial configurations to simultaneously and efficiently remove two types of impurities, boron and phosphorus, which have very different properties, demonstrating a synergistic effect and a purification effect superior to that of a single component.

[0018] (4) Simple process: The method of the present invention is mild and does not require high temperature, high pressure and complex equipment. Moreover, the siloxane complexing agent has good solubility in trichlorosilane and does not produce solid precipitates, thus avoiding the problem of equipment blockage. Detailed Implementation

[0019] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0020] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Every smaller range between any stated value or intermediate value within a stated range, and any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0021] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0022] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0023] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0024] An embodiment of the present invention provides a method for removing trace boron and phosphorus impurities from trichlorosilane, comprising the following steps: adding a complexing agent to crude liquid trichlorosilane to carry out a complexing reaction, such that the complexing agent reacts with the boron and phosphorus impurities in the crude liquid trichlorosilane to generate a high-boiling-point complex; then distilling the mixture obtained from the reaction, separating the trichlorosilane and the high-boiling-point complex by controlling the distillation conditions, and collecting the obtained fraction, which is the purified trichlorosilane; The complexing agent is selected from at least one of cyclic siloxanes and chain polysiloxanes; The general formula for cyclic siloxanes is (R¹R²SiO). n , where R 1 R 2 Independently selected from methyl or vinyl, n=3~5; The general formula for chain siloxanes is R 3 Si-O-SiR 3 , where R 3 It is independently selected from methyl or phenyl.

[0025] This invention uses cyclic siloxanes and chain polysiloxanes as complexing agents to remove trace boron and phosphorus impurities from trichlorosilane. Specifically, cyclic siloxanes, due to the strong electrostatic potential superposition at the center of their cyclic structure, exhibit excellent complexing ability for trace boron and metallic impurities in trichlorosilane. Chain polysiloxanes, on the other hand, contain abundant specific functional groups, effectively utilizing the weak electron-withdrawing properties of phosphorus impurities to achieve efficient removal. The two work synergistically to complete the complexation and removal of the aforementioned impurities. Compared to other existing siloxanes, the cyclic and chain polysiloxanes selected in this invention can remove boron and phosphorus impurities from trichlorosilane at a low concentration of 150 ppb to below 10 ppb, with the best results achieving a boron concentration of 1.02 ppb and a phosphorus concentration of 6.34 ppb, achieving a boron removal rate of 99.3%.

[0026] In a preferred embodiment of the present invention, the cyclic siloxane is selected from hexamethylcyclotrisiloxane, octamethylcyclotetrasiloxane, decamethylcyclopentasiloxane or 2,4,6,8-tetramethyl-2,4,6,8-tetravinylcyclotetrasiloxane.

[0027] In a preferred embodiment of the present invention, the chain polysiloxane is selected from 1,1,3,3-tetramethyl-1,3-diphenyldisiloxane.

[0028] This invention utilizes cyclic and chain siloxanes with specific structures as complexing agents to efficiently remove trace amounts of boron and phosphorus impurities from trichlorosilane. Cyclic siloxanes (such as hexamethylcyclotrisiloxane) exhibit strong coordination ability towards electron-deficient boron impurities due to the high electron cloud density and electrostatic potential energy at their cyclic center, forming stable high-boiling-point boron-siloxane complexes. Chain siloxanes (such as 1,1,3,3-tetramethyl-1,3-diphenyldisiloxane) weakly coordinate with phosphorus impurities (such as PCl3) through their terminal or side-chain functional groups (such as phenyl and vinyl groups), forming phosphorus-siloxane complexes. The synergistic effect of these two agents achieves efficient and simultaneous removal of boron and phosphorus impurities. The resulting complexes have significantly higher boiling points than trichlorosilane and can be separated by a simple distillation process, thus achieving deep purification.

[0029] In a preferred embodiment of the present invention, the mass ratio of crude liquid trichlorosilane to complexing agent is (100~1050):1; preferably, the mass ratio of crude liquid trichlorosilane to complexing agent is (500~1050):1.

[0030] In a preferred embodiment of the present invention, the complexation reaction is carried out at room temperature, at a pressure of 0.1 MPa, and for a time of 1 hour.

[0031] In a preferred embodiment of the present invention, the distillation temperature is 55°C to 90°C, preferably 65°C to 70°C.

[0032] In a preferred embodiment of the present invention, when the complexing agent is a mixture of cyclic siloxanes and chain siloxanes, the mass ratio of cyclic siloxanes to chain siloxanes is (1~10):1, preferably (1~2):1, and more preferably 2:1.

[0033] The cyclic and chain siloxanes used in this invention have advantages such as high stability, low susceptibility to introducing new impurities, and good compatibility with chlorosilanes. They can efficiently remove ppb-level boron and phosphorus impurities. The trichlorosilane purified by the method of this invention is suitable for the production of electronic-grade polycrystalline silicon.

[0034] Unless otherwise specified, the room temperature in this invention is 25±2℃.

[0035] It should be noted that any aspects not described in detail in this invention are conventional practices in the field and are not the focus of this invention.

[0036] The technical solution of the present invention will be further illustrated by the following embodiments.

[0037] Example 1 A method for removing trace boron and phosphorus impurities from trichlorosilane includes the following steps: Weigh 0.031 g of hexamethylcyclotrisiloxane and add it to 20 mL (approximately 26.8 g) of crude trichlorosilane liquid (containing 150 ppb of boron impurities). Shake at 25 °C for 1 h (pressure 0.1 MPa) to allow the hexamethylcyclotrisiloxane and boron impurities to fully complex. Then place the mixture in a distillation apparatus and heat it to 65 °C. The distillate obtained is the purified trichlorosilane.

[0038] According to ICP-MS testing, the boron content of the distillate in this embodiment was 2.72 ppb.

[0039] Example 2 A method for removing trace boron and phosphorus impurities from trichlorosilane includes the following steps: Weigh 0.026 g of hexamethylcyclotrisiloxane and add it to 20 mL of crude trichlorosilane liquid (containing 150 ppb of phosphorus impurities). Shake at 25 °C for 1 h (pressure 0.1 MPa) to allow the hexamethylcyclotrisiloxane and phosphorus impurities to fully complex. Then place the mixture in a distillation apparatus and heat it to 65 °C. The distillate obtained is the purified trichlorosilane.

[0040] According to ICP-MS testing, the phosphorus content in the distillate in this embodiment was 22.51 ppb.

[0041] Example 3 A method for removing trace boron and phosphorus impurities from trichlorosilane includes the following steps: Weigh 0.041 g of octamethylcyclotetrasiloxane and add it to 20 mL of crude trichlorosilane liquid (containing 150 ppb of boron impurities). Shake at 25 °C for 1 h (pressure 0.1 MPa) to allow the octamethylcyclotetrasiloxane and boron impurities to fully complex. Then place the mixture in a distillation apparatus and heat it to 65 °C. The distillate obtained is the purified trichlorosilane.

[0042] According to ICP-MS testing, the boron content of the distillate in this embodiment was 1.79 ppb.

[0043] Example 4 A method for removing trace boron and phosphorus impurities from trichlorosilane includes the following steps: Weigh 0.035 g of octamethylcyclotetrasiloxane and add it to 20 mL of crude trichlorosilane liquid (containing 150 ppb of phosphorus impurities). Shake at 25 °C for 1 h (pressure 0.1 MPa) to allow the octamethylcyclotetrasiloxane and phosphorus impurities to fully complex. Then place the mixture in a distillation apparatus and heat it to 65 °C. The distillate obtained is the purified trichlorosilane.

[0044] According to ICP-MS testing, the phosphorus content of the distillate in this embodiment was 9.01 ppb.

[0045] Example 5 A method for removing trace boron and phosphorus impurities from trichlorosilane includes the following steps: Weigh 0.051 g of decamethylcyclopentasiloxane and add it to 20 mL of crude trichlorosilane liquid (containing 150 ppb of boron impurities). Shake at 25 °C for 1 h (pressure 0.1 MPa) to allow the decamethylcyclopentasiloxane and boron impurities to fully complex. Then place the mixture in a distillation apparatus and heat it to 65 °C. The distillate obtained is the purified trichlorosilane.

[0046] According to ICP-MS testing, the boron content of the distillate in this embodiment was 4.04 ppb.

[0047] Example 6 A method for removing trace boron and phosphorus impurities from trichlorosilane includes the following steps: Weigh 0.043 g of decamethylcyclopentasiloxane and add it to 20 mL of crude trichlorosilane liquid (containing 150 ppb of phosphorus impurities). Shake at 25 °C for 1 h (pressure 0.1 MPa) to allow the decamethylcyclopentasiloxane and phosphorus impurities to fully complex. Then place the mixture in a distillation apparatus and heat it to 65 °C. The distillate obtained is the purified trichlorosilane.

[0048] According to ICP-MS testing, the phosphorus content of the distillate in this embodiment was 7.50 ppb.

[0049] Example 7 A method for removing trace boron and phosphorus impurities from trichlorosilane includes the following steps: Weigh 0.039 g of 1,1,3,3-tetramethyl-1,3-diphenyldisiloxane and add it to 20 mL of crude trichlorosilane liquid (containing 150 ppb of boron impurities). Shake at 25 °C for 1 h (pressure 0.1 MPa) to allow 1,1,3,3-tetramethyl-1,3-diphenyldisiloxane and boron impurities to fully complex. Then place the mixture in a distillation apparatus and heat to 65 °C. The distillate obtained is the purified trichlorosilane.

[0050] According to ICP-MS testing, the boron content of the distillate in this embodiment was 14.51 ppb.

[0051] Example 8 A method for removing trace boron and phosphorus impurities from trichlorosilane includes the following steps: Weigh 0.033 g of 1,1,3,3-tetramethyl-1,3-diphenyldisiloxane and add it to 20 mL of crude trichlorosilane liquid (containing 150 ppb of phosphorus impurities). Shake at 25 °C for 1 h (pressure 0.1 MPa) to allow 1,1,3,3-tetramethyl-1,3-diphenyldisiloxane and phosphorus impurities to fully complex. Then place the mixture in a distillation apparatus and heat to 65 °C. The distillate obtained is the purified trichlorosilane.

[0052] According to ICP-MS testing, the phosphorus content of the distillate in this embodiment was 7.05 ppb.

[0053] Example 9 A method for removing trace boron and phosphorus impurities from trichlorosilane includes the following steps: Weigh 0.047 g of 2,4,6,8-tetramethyl-2,4,6,8-tetravinylcyclotetrasiloxane and add it to 20 mL of crude trichlorosilane liquid (containing 150 ppb of boron impurities). Shake at 25 °C for 1 h (pressure 0.1 MPa) to allow 2,4,6,8-tetramethyl-2,4,6,8-tetravinylcyclotetrasiloxane and boron impurities to fully complex. Then place the mixture in a distillation apparatus and heat to 65 °C. The distillate obtained is the purified trichlorosilane.

[0054] According to ICP-MS testing, the boron content of the distillate in this embodiment was 11.05 ppb.

[0055] Example 10 A method for removing trace boron and phosphorus impurities from trichlorosilane includes the following steps: Weigh 0.04 g of 2,4,6,8-tetramethyl-2,4,6,8-tetravinylcyclotetrasiloxane and add it to 20 mL of crude trichlorosilane liquid (containing 150 ppb of phosphorus impurities). Shake at 25 °C for 1 h (pressure 0.1 MPa) to allow 2,4,6,8-tetramethyl-2,4,6,8-tetravinylcyclotetrasiloxane and phosphorus impurities to fully complex. Then place the mixture in a distillation apparatus and heat to 65 °C. The distillate obtained is the purified trichlorosilane.

[0056] According to ICP-MS testing, the phosphorus content of the distillate in this embodiment was 15.10 ppb.

[0057] Example 11 A method for removing trace boron and phosphorus impurities from trichlorosilane includes the following steps: Weigh 0.028 g of octamethylcyclotetrasiloxane and 0.014 g of 1,1,3,3-tetramethyl-1,3-diphenyldisiloxane, and add them to 20 mL of crude trichlorosilane liquid (containing 150 ppb each of boron and phosphorus impurities). Shake at 25 °C for 1 h (pressure 0.1 MPa) to allow the siloxane and boron impurities to fully complex. Then place the mixture in a distillation apparatus and heat to 65 °C. The distillate obtained is the purified trichlorosilane.

[0058] According to ICP-MS testing, the boron and phosphorus contents in the distillate of this embodiment were 1.02 ppb and 6.34 ppb, respectively.

[0059] Example 12 A method for removing trace boron and phosphorus impurities from trichlorosilane includes the following steps: Weigh 0.021 g of octamethylcyclotetrasiloxane and 0.021 g of 1,1,3,3-tetramethyl-1,3-diphenyldisiloxane, and add them to 20 mL of crude trichlorosilane liquid (containing 150 ppb each of boron and phosphorus impurities). Shake at 25 °C for 1 h (pressure 0.1 MPa) to allow the siloxane and boron impurities to fully complex. Then place the mixture in a distillation apparatus and heat to 65 °C. The distillate obtained is the purified trichlorosilane.

[0060] According to ICP-MS testing, the boron and phosphorus contents in the distillate of this embodiment were 1.57 ppb and 6.87 ppb, respectively.

[0061] Example 13 A method for removing trace boron and phosphorus impurities from trichlorosilane includes the following steps: Weigh 0.032 g of octamethylcyclotetrasiloxane and 0.011 g of 1,1,3,3-tetramethyl-1,3-diphenyldisiloxane, and add them to 20 mL of crude trichlorosilane liquid (containing 150 ppb each of boron and phosphorus impurities). Shake at 25 °C for 1 h (pressure 0.1 MPa) to allow the siloxane and boron impurities to fully complex. Then place the mixture in a distillation apparatus and heat to 65 °C. The distillate obtained is the purified trichlorosilane.

[0062] According to ICP-MS testing, the boron and phosphorus contents in the distillate of this embodiment were 1.22 ppb and 8.03 ppb, respectively.

[0063] Example 14 A method for removing trace boron and phosphorus impurities from trichlorosilane is the same as in Example 11, except that the distillation temperature is 55°C.

[0064] According to ICP-MS testing, the boron and phosphorus contents in the distillate of this embodiment were 3.38 ppb and 8.64 ppb, respectively.

[0065] Example 15 A method for removing trace boron and phosphorus impurities from trichlorosilane is the same as in Example 11, except that the distillation temperature is 70°C.

[0066] According to ICP-MS testing, the boron and phosphorus contents in the distillate of this embodiment were 1.34 ppb and 6.36 ppb, respectively.

[0067] Example 16 A method for removing trace boron and phosphorus impurities from trichlorosilane is the same as in Example 11, except that the distillation temperature is 90°C.

[0068] According to ICP-MS testing, the boron and phosphorus contents in the distillate of this embodiment were 8.59 ppb and 14.03 ppb, respectively.

[0069] Example 17 A method for removing trace boron and phosphorus impurities from trichlorosilane includes the following steps: Weigh 0.04 g of octamethylcyclotetrasiloxane and 0.004 g of 1,1,3,3-tetramethyl-1,3-diphenyldisiloxane, and add them to 20 mL of crude trichlorosilane liquid (containing 150 ppb each of boron and phosphorus impurities). Shake at 25 °C for 1 h (pressure 0.1 MPa) to allow the siloxane and boron impurities to fully complex. Then place the mixture in a distillation apparatus and heat to 65 °C. The distillate obtained is the purified trichlorosilane.

[0070] According to ICP-MS testing, the boron and phosphorus contents in the distillate of this embodiment were 4.75 ppb and 9.78 ppb, respectively.

[0071] Example 18 A method for removing trace boron and phosphorus impurities from trichlorosilane includes the following steps: Weigh 0.178 g of octamethylcyclotetrasiloxane and 0.089 g of 1,1,3,3-tetramethyl-1,3-diphenyldisiloxane, and add them to 20 mL of crude trichlorosilane liquid (containing 150 ppb each of boron and phosphorus impurities). Shake at 25 °C for 1 h (pressure 0.1 MPa) to allow the siloxane and boron impurities to fully complex. Then place the mixture in a distillation apparatus and heat to 65 °C. The distillate obtained is the purified trichlorosilane.

[0072] According to ICP-MS testing, the boron and phosphorus contents in the distillate of this embodiment were 5.73 ppb and 9.36 ppb, respectively.

[0073] Example 19 Take 5 mL of the distillate obtained in Example 11, process it, and then use a TOC analyzer to test the organic carbon content in the distillate. The organic carbon content was found to be 0.058 μg / L.

[0074] Comparative Example 1 A method for removing trace boron and phosphorus impurities from trichlorosilane includes the following steps: 20 mL of crude trichlorosilane liquid (containing 150 ppb of phosphorus impurities) was shaken at 25 °C for 1 h (pressure 0.1 MPa), and then placed in a distillation apparatus and heated to 65 °C to collect the distillate.

[0075] According to ICP-MS testing, the phosphorus content of the distillate in this comparative example was 143.21 ppb.

[0076] Comparative Example 2 A method for removing trace boron and phosphorus impurities from trichlorosilane includes the following steps: 20 mL of crude trichlorosilane liquid (containing 150 ppb of boron impurities) was shaken at 25 °C for 1 h (pressure 0.1 MPa), and then placed in a distillation apparatus, heated to 65 °C, and the distillate was collected.

[0077] According to ICP-MS testing, the boron content of the distillate in this comparative example was 124.52 ppb.

[0078] Comparative Example 3 Take 5 mL of crude trichlorosilane liquid (without added boron and phosphorus impurities), and after processing, use a TOC analyzer to test the organic carbon content in the trichlorosilane. The organic carbon content was found to be 0.056 μg / L.

[0079] By comparing the various embodiments with the comparative examples, it can be found that cyclic siloxanes and / or chain siloxanes are excellent complexing agents for removing trace boron and phosphorus impurities from trichlorosilane.

[0080] By comparing Examples 1, 3, 5, 7, and 9 (using the same amount of complexing agent), it can be found that octamethylcyclotetrasiloxane has the highest removal rate for boron impurities in trichlorosilane.

[0081] By comparing Examples 2, 4, 6, 8, and 10 (using the same amount of complexing agent), it can be found that 1,1,3,3-tetramethyl-1,3-diphenyldisiloxane has the highest removal rate for phosphorus impurities in trichlorosilane.

[0082] Examples 11, 12, and 13 show that the complexation effect is best when the mass ratio of cyclic siloxane to chain siloxane mixture is 2:1.

[0083] By comparing Example 19 and Comparative Example 3, it can be found that the siloxane used in this invention does not cause an increase in the organic carbon content of the sample.

[0084] The above are merely preferred embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for removing trace boron and phosphorus impurities from trichlorosilane, characterized in that, Includes the following steps: Add the complexing agent to crude liquid trichlorosilane to carry out a complexation reaction, and then distill the resulting mixture. The complexing agent is selected from at least one of cyclic siloxanes and chain siloxanes; The general formula for the cyclic siloxane is (R¹R²SiO). n , where R 1 R 2 Independently selected from methyl or vinyl, n=3~5; The general formula of the chain siloxane is R 3 Si-O-SiR 3 , where R 3 It is independently selected from methyl or phenyl.

2. The method for removing trace boron and phosphorus impurities from trichlorosilane according to claim 1, characterized in that, The cyclic siloxane is selected from hexamethylcyclotrisiloxane, octamethylcyclotetrasiloxane, decamethylcyclopentasiloxane, or 2,4,6,8-tetramethyl-2,4,6,8-tetravinylcyclotetrasiloxane.

3. The method for removing trace boron and phosphorus impurities from trichlorosilane according to claim 1, characterized in that, The chain siloxane is selected from 1,1,3,3-tetramethyl-1,3-diphenyldisiloxane.

4. The method for removing trace boron and phosphorus impurities from trichlorosilane according to claim 1, characterized in that, The mass ratio of the crude liquid trichlorosilane to the complexing agent is (100~1050):

1.

5. The method for removing trace boron and phosphorus impurities from trichlorosilane according to claim 4, characterized in that, The mass ratio of the crude liquid trichlorosilane to the complexing agent is (500~1050):

1.

6. The method for removing trace boron and phosphorus impurities from trichlorosilane according to claim 1, characterized in that, The complexation reaction was carried out at room temperature, at a pressure of 0.1 MPa, and for 1 hour.

7. The method for removing trace boron and phosphorus impurities from trichlorosilane according to claim 1, characterized in that, The distillation temperature is 55℃~90℃.

8. The method for removing trace boron and phosphorus impurities from trichlorosilane according to claim 7, characterized in that, The distillation temperature is 65℃~70℃.

9. The method for removing trace boron and phosphorus impurities from trichlorosilane according to claim 1, characterized in that, When the complexing agent is a mixture of cyclic siloxanes and chain siloxanes, the mass ratio of the cyclic siloxanes to the chain siloxanes is (1~10):

1.

10. The method for removing trace boron and phosphorus impurities from trichlorosilane according to claim 9, characterized in that, The mass ratio of the cyclic siloxane to the chain siloxane is (1~2):1.