Method for removing boron and phosphorus impurities from chlorosilane

Abstract

Disclosed in the present invention is a method for removing boron and phosphorus impurities from chlorosilane. The method comprises the following steps: (1) feeding, involving: mixing a crude chlorosilane liquid and a complexing agent in proportion to obtain a mixed liquid; (2) separation, involving: heating the mixed liquid obtained in step (1) of feeding to 50-95°C, so as to obtain a vapor-state fraction and a liquid-state high-boiling-point component; and (3) collection, involving: collecting the fraction obtained in step (2) of separation, which fraction is a chlorosilane liquid from which boron and phosphorus impurities have been removed. The advantages of the method lie in that by using an ether substance as a complexing agent, mixing same with a crude chlorosilane liquid in a reactor, then heating the mixture to perform a distillation operation, and collecting a fraction having a boiling point of 30-60°C to serve as a chlorosilane liquid from which boron and phosphorus impurities have been removed, the effect of removing boron and phosphorus impurities is significant, the content of the boron and phosphorus impurities in the crude chlorosilane liquid can be greatly reduced, the influence on the product quality of downstream products by the continuous enrichment of boron and phosphorus impurities can be avoided, and the effect of purifying chlorosilane can be achieved.

Description

Method for removing boron and phosphorus impurities in chlorosilane TECHNICAL FIELD

[0001] The present application relates to the field of chlorosilane production, in particular to a method for removing boron and phosphorus impurities in chlorosilane. BACKGROUND

[0002] Chlorosilane is an important chemical raw material, which has wide application value and plays a key role in many fields. In the semiconductor industry, it can be used as a key material for producing high-quality silicon wafers, directly affecting the performance and yield of integrated circuits.

[0003] In the production process of chlorosilane, industrial coarse silicon powder may contain metal and non-metal impurities, which will be introduced into chlorosilane during silicon powder cold hydrogenation. Therefore, the product may carry some metal impurities and some non-metal impurities. For metal impurities, they can be removed by rectification, but for non-metal impurities, the main components are BCl3 and other boron compounds, as well as PCl3 and PCI5, and other phosphorus compounds. Since the boiling points of these impurities are similar to those of chlorosilane, and in the periodic table, boron and silicon are diagonal positions, and phosphorus and silicon are adjacent positions, the atomic radii of silicon and boron, phosphorus are similar, so their chlorides and hydrides have similar properties and are mutually soluble, and it is difficult to remove them efficiently by conventional physical methods. In addition, in the reduction process of gaseous chlorosilane to elemental silicon in a hydrogen atmosphere, if the chlorosilane material contains metal and non-metal impurities, especially boron and phosphorus, it will have a great impact on the quality of silicon rods. BH3, PH3 and other boron and phosphorus impurities exist in the form of gas in hydrogen, but they cannot be completely removed by traditional tail gas recovery methods and can only participate in production circulation with hydrogen, which will continuously enrich in the system. As a downstream product of electronic-grade polysilicon, electronic devices and integrated circuits are constantly developing towards smaller sizes, and the mixing of even a small amount of boron and phosphorus impurities will affect the product quality of integrated circuits. Therefore, according to the properties of boron and phosphorus compounds, exploring an efficient method for removing trace amounts of boron and phosphorus impurities in trichlorosilane and circulating hydrogen is of great significance for improving China's international competitiveness in the field of electronic-grade polysilicon and helping the country upgrade high-end industries. SUMMARY

[0004] In order to efficiently remove boron and phosphorus impurities in chlorosilane, the purpose of the present application is to provide a method for removing boron and phosphorus impurities in chlorosilane.

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

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

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

[0008] (2)Separation: heating the mixed liquid obtained in the step (1) charging to 50-95℃, obtaining the distillate in vapor state and the high-boiling component in liquid state;

[0009] (3) Collection: collecting the distillate obtained in the step (2) separation, which is the chlorosilane liquid from which the boron and phosphorus impurities are removed.

[0010] Further, in the step (1) charging, the complexing agent is an ether substance.

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

[0012] Further, the temperature of the distillate obtained in the step (2) separation is 30-60℃.

[0013] The chlorosilane liquid is mainly a mixed liquid of trichlorosilane and silicon tetrachloride, wherein the boiling point of trichlorosilane is 31.8℃, and the boiling point of silicon tetrachloride is 57.6℃. With the heating of the mixed liquid, trichlorosilane is first heated and vaporized, and then condensed into liquid through a condenser for collection. Subsequently, silicon tetrachloride is vaporized and collected through condensation. After obtaining the distillate of the mixed liquid of trichlorosilane and silicon tetrachloride, the content of metal elements in the distillate is tested. The boiling point of n-butyl ether is 141℃, and it is left in the distillation flask together with the remaining chlorosilane liquid that is not distilled.

[0014] Advantages of the present application:

[0015] By using an ether substance as a complexing agent, mixing it with a crude chlorosilane liquid in a reactor, and then performing distillation operation by heating and collecting the distillate with a boiling point of 30-60℃ as the chlorosilane liquid from which the boron and phosphorus impurities are removed, 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, the continuous enrichment of the 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 in cost, easy to operate, does not need to invest in expensive equipment, and does not introduce new impurities, thereby providing a new research direction for removing the boron and phosphorus impurities in chlorosilane and providing a strong guarantee for the production of high-quality silicon wafers. DETAILED DESCRIPTION

[0016] The technical solutions in the embodiments of the present application will be described below in a clear and complete manner. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0017] Embodiment 1:

[0018] A method for removing boron and phosphorus impurities from chlorosilane, comprising the following steps:

[0019] (1) Feeding: 90 ml of crude trichlorosilane with a boron content of 0.0254 μg / ml and a phosphorus content of 0.0044 μg / ml is added into a reactor, and then 9 ml of n-butyl ether is added into the reactor to obtain a mixed liquid;

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

[0021] (3) Collection: the temperature of the distillate is detected by a thermometer arranged at the distillate outlet, and the distillate with a temperature of 30-60°C is collected in a collector, thereby obtaining 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] Example 2:

[0023] A method for removing boron and phosphorus impurities from chlorosilane, comprising the following steps:

[0024] (1) Feeding: 100 ml of a mixed liquid of crude trichlorosilane and crude silicon tetrachloride with a boron content of 0.0366 μg / ml and a phosphorus content of 0.0103 μg / ml is added into a reactor, and then 1 ml of n-butyl ether is added into the reactor to obtain a mixed liquid;

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

[0026] (3) Collection: the temperature of the distillate is detected by a thermometer arranged at the distillate outlet, and the distillate with a temperature of 30-60°C is collected in a collector, thereby obtaining chlorosilane liquid with boron and phosphorus impurities removed, wherein the B content in the 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 distillate decrease by an order of magnitude, it can be proved that the addition of n-butyl ether plays a significant role in removing B and P impurities in chlorosilane in actual rectification process operation.

[0027] Example 3:

[0028] A method for removing boron and phosphorus impurities from chlorosilane, comprising the following steps:

[0029] (1) Feeding: 100 ml of a mixed liquid of crude trichlorosilane, crude dichlorodihydrogen silane and crude silicon tetrachloride with a boron content of 0.3693 μg / ml and a phosphorus content of 0.1119 μg / ml is added into a reactor, and then 0.01 ml of n-butyl ether is added into the reactor to obtain a mixed liquid;

[0030] (2)Separation: distillation by heating the reactor to 95°C by oil bath;

[0031] (3)Collection: collecting the fraction of 30-60°C in the collector by detecting the temperature of the fraction by the thermometer set at the fraction outlet, thus obtaining the chlorosilane liquid with boron and phosphorus impurities removed, wherein the boron content in the distilled trichlorosilane and silicon tetrachloride liquid is 0.0041 μg / ml, and the removal rate is as high as 98.89%; the phosphorus content is 0.0134 μg / ml, and the removal rate is as high as 88.03%.

[0032] Comparative Example 1

[0033] The difference between the present comparative example and Example 1 is that in step (1), the amount of n-butyl ether added into the reactor is 20 ml; the boron content in the finally obtained 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 benefit brought by the excess n-butyl ether added far exceeds the cost, and in combination with the comprehensive removal effect of boron and phosphorus, the volume ratio of n-butyl ether to the crude chlorosilane liquid in the present application is limited to 1:10-10000.

[0035] The above only describes the preferred embodiments of the present application and should not be used to limit the present application, and any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application should be included in the protection scope of the present application.

Claims

1. A method for removing boron and phosphorus impurities from chlorosilanes, characterized by, The method comprises the following steps: (1) mixing: mixing the crude chlorosilane liquid and the complexing agent in proportion to obtain a mixed liquid; (2) separation: heating the mixed liquid obtained in the step (1) to 50-95 ℃ to obtain a gaseous fraction and a liquid high-boiling component; (3) collection: collecting the fraction obtained in the step (2), which is a chlorosilane liquid from which boron and phosphorus impurities are removed.

2. The method of claim 1, wherein the method is characterized by, In the step (1), the complexing agent is an ether substance.

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

4. The method of claim 1, wherein the method is characterized by, The temperature of the fraction obtained in the step (2) is 30-60 ℃.