Method for removing boron and phosphorus impurities in chlorosilane

Abstract

The invention discloses a method for removing boron and phosphorus impurities in chlorosilane, which comprises the following steps: (1) feeding: mixing crude chlorosilane liquid and a complexing agent in proportion to obtain mixed liquid; (2) separation: heating the mixed liquid obtained in the step (1) to 50-95 DEG C to obtain a vapor-state fraction and a liquid-state high-boiling-point component; and (3) collection: collecting fractions obtained in the separation in the step (2), so as to obtain the chlorosilane liquid with boron and phosphorus impurities removed. The method has the advantages that the ether substance serving as a complexing agent is mixed with the crude chlorosilane liquid in the reactor and then is heated to perform distillation operation, and the fraction with the boiling point of 30-60 DEG C is collected to serve as the chlorosilane liquid for removing the boron and phosphorus impurities, so that the effect of removing the boron and phosphorus impurities is remarkable, the content of the boron and phosphorus impurities in the crude chlorosilane liquid can be greatly reduced, and the production cost is reduced. The influence on the product quality of downstream products due to continuous enrichment of boron and phosphorus impurities can be avoided, and the effect of purifying chlorosilane can be achieved.

Description

Technical field:

[0001] The invention relates to the field of chlorosilane production, and in particular to a method for removing boron and phosphorus impurities in chlorosilane. Background technology:

[0002] Chlorosilane is an important chemical raw material with wide application value in many fields and plays a key role. For example, in the semiconductor industry, it can be used as a key material for the production of high-quality silicon wafers, which directly affects the performance and output of integrated circuits.

[0003] In the production process of chlorosilane, since industrial coarse silicon powder contains metal impurities and non-metal impurities, they will be substituted into chlorosilane during cold hydrogenation of silicon powder. Therefore, the product will carry some metal impurities and some non-metal impurities. Metal impurities can be removed by distillation, but non-metal impurities are mainly boron compounds such as BCl3, PCl3 and PCI 5, Phosphorus compounds, such as chlorosilane, have a boiling point close to that of these impurities; and, in the periodic table, boron and silicon are diagonal positions, phosphorus and silicon are adjacent positions, and the radius of silicon, boron and phosphorus is similar, so their chlorides and hydrides have similar properties and are mutually soluble, and it is difficult to remove them efficiently using conventional physical methods. In addition, in the reduction process of reducing gaseous chlorosilane to elemental silicon in a hydrogen atmosphere, if the chlorosilane material is mixed with metal and non-metallic impurities, especially boron and phosphorus, it will have a great impact on the quality of the silicon rod. Boron and phosphorus impurities such as BH3 and PH3 exist in hydrogen in the form of gas, but cannot be completely removed by traditional tail gas recovery methods. They can only participate in the production cycle with hydrogen and will continue to be enriched in the system. As downstream products of electronic-grade polysilicon, the size of electronic devices and integrated circuits continues to develop in a smaller direction, and even a small amount of boron and phosphorus impurities mixed in will affect the product quality of integrated circuits. Therefore, based on the properties of boron and phosphorus compounds, exploring methods to efficiently remove trace boron and phosphorus impurities in trichlorosilane and circulating hydrogen is of great significance for enhancing my country's international competitiveness in the field of electronic-grade polysilicon and helping the country upgrade its high-end industries. Summary of the invention:

[0004] In order to efficiently remove boron and phosphorus impurities in chlorosilane and improve the performance, the present invention aims to provide a method for removing boron and phosphorus impurities in chlorosilane.

[0005] The present invention is implemented by the following technical solutions:

[0006] A method for removing boron and phosphorus impurities in chlorosilane comprises the following steps:

[0007] (1) Adding materials: mixing crude chlorosilane liquid and complexing agent in proportion to obtain a mixed liquid;

[0008] (2) separation: heating the mixed liquid obtained in the step (1) to 50-95° C. to obtain a vapor fraction and a liquid high-boiling-point component;

[0009] (3) Collection: The fraction obtained in the separation of step (2) is collected, i.e., the chlorosilane liquid from which the boron and phosphorus impurities are removed.

[0010] Furthermore, in the step (1) of adding materials, the complexing agent is an ether substance.

[0011] Furthermore, in the step (1), the volume ratio of the complexing agent to the crude chlorosilane liquid is 1:10 to 10000.

[0012] Furthermore, the temperature of the fraction obtained in the separation of step (2) is 30-60°C.

[0013] Chlorosilane liquid is mainly a mixture of trichlorosilane and silicon tetrachloride, where trichlorosilane has a boiling point of 31.8°C and silicon tetrachloride has a boiling point of 57.6°C. As the mixed liquid is heated, trichlorosilane is heated and vaporized first, and condensed into liquid and collected through a condenser, followed by silicon tetrachloride, which is vaporized and collected through condensation. After the fraction of the mixed liquid of trichlorosilane and silicon tetrachloride is obtained, the content of metal elements in it is tested. The boiling point of n-butyl ether is 141°C, and it is left in the distillation flask together with the remaining undistilled chlorosilane liquid.

[0014] Advantages of the present invention:

[0015] The ether substance is used as a complexing agent, mixed with crude chlorosilane liquid in a reactor, and then distilled by heating. The fraction with a boiling point of 30 to 60°C is collected as the chlorosilane liquid for removing boron and phosphorus impurities. The effect of removing boron and phosphorus impurities is remarkable, the content of boron and phosphorus impurities in the crude chlorosilane liquid can be greatly reduced, the continuous enrichment of boron and phosphorus impurities can be avoided to affect the product quality of downstream products, and the effect of purifying chlorosilane can be achieved. At the same time, the method is simple, low-cost, easy to operate, does not require expensive equipment, and will not introduce new impurities. It provides a new research direction for removing boron and phosphorus impurities in chlorosilane and provides a strong guarantee for the production of high-quality silicon wafers. Specific implementation method:

[0016] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0017] Embodiment 1:

[0018] A method for removing boron and phosphorus impurities in chlorosilane comprises the following steps:

[0019] (1) Adding materials: adding 90 ml of crude trichlorosilane having a boron content of 0.0254 μg / ml and a phosphorus content of 0.0044 μg / ml to a reactor, and then adding 9 ml of n-butyl ether to the reactor to obtain a mixed liquid;

[0020] (2) Separation: The reactor was heated to 50°C by an oil bath for distillation;

[0021] (3) Collection: The temperature of the distillate is detected by a thermometer set at the outlet of the distillate, and the distillate at 30-60°C is collected in a collector to obtain a chlorosilane liquid with boron and phosphorus impurities removed, wherein the boron content is 0.0025 μg / ml, and the removal rate is as high as 90.16%; the phosphorus content is 0 μg / ml, and the removal rate is as high as 100%.

[0022] Embodiment 2:

[0023] A method for removing boron and phosphorus impurities in chlorosilane comprises the following steps:

[0024] (1) Adding materials: adding 100 ml of a mixed solution of crude trichlorosilane and crude silicon tetrachloride having a boron content of 0.0366 μg / ml and a phosphorus content of 0.0103 μg / ml to a reactor, and then adding 1 ml of n-butyl ether to the reactor to obtain a mixed liquid;

[0025] (2) Separation: The reactor was heated to 95°C by an oil bath for distillation;

[0026] (3) Collection: The temperature of the distillate is detected by a thermometer set at the outlet of the distillate, and the distillate at 30-60°C is collected in a collector to obtain a chlorosilane liquid with boron and phosphorus impurities removed. Among them, the B content in trichlorosilane and silicon tetrachloride liquids is 0.0060 μg / ml and 0.0028 μg / ml, respectively, and the phosphorus content is 0 μg / ml. If the B and P contents in the obtained chlorosilane fractions decrease by an order of magnitude, it can be proved that the addition of n-butyl ether will play a significant role in removing B and P impurities in chlorosilane in the actual distillation process operation.

[0027] Embodiment 3:

[0028] A method for removing boron and phosphorus impurities in chlorosilane comprises the following steps:

[0029] (1) Adding materials: adding 100 ml of a mixed solution of crude trichlorosilane, crude dichlorosilane and crude silicon tetrachloride having a boron content of 0.3693 μg / ml and a phosphorus content of 0.1119 μg / ml to a reactor, and then adding 0.01 ml of n-butyl ether to the reactor to obtain a mixed liquid;

[0030] (2) Separation: The reactor was heated to 95°C by an oil bath for distillation;

[0031] (3) Collection: The temperature of the distillate is detected by a thermometer set at the outlet of the distillate, and the distillate at 30-60°C is collected in a collector to obtain a chlorosilane liquid with boron and phosphorus impurities removed. The boron content in the distilled trichlorosilane and silicon tetrachloride liquids is 0.0041 μg / ml, with a removal rate of up to 98.89%; the phosphorus content is 0.0134 μg / ml, with a removal rate of up to 88.03%.

[0032] Comparative Example 1:

[0033] The difference between this comparative example and Example 1 is that in step (1), the amount of n-butyl ether added to the reactor is 20 ml; the boron content in the final fraction is 0.0019 μg / ml, and the removal rate is 92.5%; the phosphorus content is 0.0003 μg / ml, and the removal rate is 93.18%.

[0034] Since n-butyl ether is expensive, the additional benefits brought by the addition of excessive n-butyl ether far exceed the cost. Moreover, considering the comprehensive removal effect on boron and phosphorus, the volume ratio of n-butyl ether to crude chlorosilane liquid in the present invention is limited to 1:10-10000.

[0035] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for removing boron and phosphorus impurities in chlorosilane, characterized in that: The following steps are involved: (1) Adding materials: mixing crude chlorosilane liquid and complexing agent in proportion to obtain a mixed liquid; (2) separation: heating the mixed liquid obtained in the step (1) to 50-95° C. to obtain a vapor fraction and a liquid high-boiling-point component; (3) Collection: The fraction obtained in the separation of step (2) is collected, i.e., the chlorosilane liquid from which the boron and phosphorus impurities are removed.

2. A method for removing boron and phosphorus impurities in chlorosilane according to claim 1, characterized in that: In the step (1) of adding materials, the complexing agent is an ether substance.

3. A method for removing boron and phosphorus impurities in chlorosilane according to claim 1, characterized in that: In the step (1), the volume ratio of the complexing agent to the crude chlorosilane liquid is 1:10 to 10000.

4. The method for removing boron and phosphorus impurities in chlorosilane according to claim 1, characterized in that: The temperature of the fraction obtained in the separation of step (2) is 30-60°C.