Method for Removing Trace Bromine from High-Purity Boron

Abstract

The present invention provides a method for removing trace bromine from high-purity boron, comprising the following steps: A) crushing a high-purity boron block to obtain boron powder; B) washing and drying the boron powder, placing it in a boron nitride container within a quartz tube, introducing oxygen, and heating to oxidize the surface of the boron powder; C) introducing nitrogen and heating the container to melt the surface boron oxide; and D) introducing hydrogen to react, with the generated hydrogen bromide discharged from the other end of the quartz tube. The method is simple to operate, pollution-free, highly efficient, easily scalable, and low-cost. The bromine content can be stably reduced to less than 20 ppb, meeting the requirements for use as an MBE source.

Description

Technical Field

[0001] The invention belongs to the technical field of semiconductor material preparation, and in particular relates to a method for removing trace bromine in high-purity boron. Background Art

[0002] Boron and its compounds possess unique physical and chemical properties and are widely used in semiconductor materials, ballistic ceramics, fuel-rich propellants, superconductors, amorphous alloys, aerospace alloys, electronic materials, chemical corrosion protection materials, ceramics, and nuclear leak prevention materials. High-purity boron powder exceeding 99.9999% purity is primarily used as a dopant for single-crystalline silicon and germanium, as well as an additive in special alloys and polycrystalline diamond. High-purity electronic-grade boron is prepared by heating and vaporizing high-purity boron bromide, mixing it with hydrogen, and then reacting and depositing it in a chemical vapor deposition system to produce electronic-grade high-purity boron.

[0003] In the process of producing high-purity boron, boron bromide is hydroreduced, and boron tribromide and H2 react chemically at high temperature to produce elemental boron and HBr. Most of the generated HBr is carried away by the air flow, and a small amount of boron bromide will react incompletely, and trace levels of bromine will still remain in the elemental boron product. Summary of the Invention

[0004] The present invention aims to provide a method for removing trace bromine from high-purity boron. The method is simple to operate, pollution-free, highly efficient, easily scalable, and low-cost. The bromine content can be stably maintained at less than 20 ppb, meeting the requirements for use as an MBE source.

[0005] The present invention provides a method for removing trace bromine in high-purity boron, comprising the following steps:

[0006] A) crushing high-purity boron blocks to obtain boron powder;

[0007] B) washing and drying the boron powder, placing it in a boron nitride container in a quartz tube, introducing oxygen, and heating to oxidize the surface of the boron powder;

[0008] C) After the oxidation is completed, nitrogen is introduced and the temperature is increased to melt the boron oxide on the surface;

[0009] D) Hydrogen is introduced to react, and the generated hydrogen bromide is discharged from the other end of the quartz tube.

[0010] Preferably, the high-purity boron block is prepared by hydroboration of bromide.

[0011] Preferably, the particle size of the boron powder is 10 to 30 meshes.

[0012] Preferably, the boron powder is cleaned using an acid aqueous solution;

[0013] The acid aqueous solution is a hydrofluoric acid aqueous solution and / or a nitric acid aqueous solution; the mass concentration of the acid aqueous solution is 1 to 10 wt%.

[0014] Preferably, the cleaned boron powder is vacuum dried at a temperature of 60 to 80° C. and for a time of 180 to 300 minutes.

[0015] Preferably, the oxidation temperature in step B) is 250-300° C., and the oxidation time is 2-4 hours.

[0016] Preferably, the flow rate of the oxygen is 150 to 250 L / h.

[0017] Preferably, the flow rate of nitrogen in step C) is 200-400 L / h.

[0018] Preferably, in step C), the temperature is raised to 550-700° C. and the holding time is 2-4 hours.

[0019] Preferably, the flow rate of the hydrogen is 100 to 500 L / h; the reaction temperature in step D) is 600 to 800° C.; and the reaction time is 8 to 16 hours.

[0020] The present invention provides a method for removing trace bromine from high-purity boron, comprising the following steps: A) crushing a high-purity boron block to obtain boron powder; B) washing and drying the boron powder, loading it into a boron nitride container and placing it in a quartz tube, introducing oxygen, and heating to oxidize the surface of the boron powder; C) introducing nitrogen and increasing the temperature after oxidation to melt the surface boron oxide; D) introducing hydrogen to react, with the generated hydrogen bromide discharged from the other end of the quartz tube. This method utilizes the fact that high-purity boron is easily oxidized and the resulting boron oxide melts at relatively low temperatures. The method first crushes the high-purity boron block, then introduces oxygen to oxidize the surface and increases the temperature to melt it, followed by hydrogenation to remove bromine. This method not only achieves deep removal of trace bromine from the boron block, but also removes metallic impurities on the boron surface. The method is simple to operate, pollution-free, highly efficient, easily scalable, and low-cost. The bromine content can be stably maintained at less than 20 ppb, meeting the requirements for use as an MBE source. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are merely embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying any creative work.

[0022] Figure 1 Schematic diagram of the device for removing trace bromine from high-purity boron in the present invention. DETAILED DESCRIPTION

[0023] The present invention provides a method for removing trace bromine in high-purity boron, comprising the following steps:

[0024] A) crushing high-purity boron blocks to obtain boron powder;

[0025] B) washing and drying the boron powder, placing it in a boron nitride container in a quartz tube, introducing oxygen, and heating to oxidize the surface of the boron powder;

[0026] C) After the oxidation is completed, nitrogen is introduced and the temperature is increased to melt the boron oxide on the surface;

[0027] D) Hydrogen is introduced to react, and the generated hydrogen bromide is discharged from the other end of the quartz tube.

[0028] The present invention first crushes the high-purity boron block into boron powder. In the present invention, the high-purity boron block is preferably prepared by hydroboration of bromide. The present invention has no special restrictions on the technology of preparing the high-purity boron block by hydroboration of bromide, and the existing conventional technology in this field can be used.

[0029] In the present invention, the boron content in the high-purity boron block is 99.9999%; the bromine content is 300-600 ppb.

[0030] In the present invention, the particle size of the boron powder is preferably 10 to 30 meshes, more preferably 10 to 20 meshes. Grinding the boron powder to this mesh size can remove bromine more thoroughly.

[0031] After obtaining the boron powder, the present invention uses an acid aqueous solution to clean the boron powder to remove impurity silicon contamination, and then vacuum-drying the boron powder.

[0032] The mass concentration of the acid aqueous solution is preferably 1 to 10 wt%, more preferably 3 to 8 wt%, such as 1 wt%, 2 wt%, 3 wt%, 4 wt%, 5 wt%, 6 wt%, 7 wt%, 8 wt%, 9 wt%, 10 wt%, preferably a range value with the upper or lower limit of any of the above numerical values; the acid aqueous solution is preferably an aqueous solution of hydrofluoric acid and / or an aqueous solution of nitric acid.

[0033] In the present invention, the temperature of the vacuum drying is preferably 60 to 80°C, more preferably 65 to 75°C, such as 60°C, 65°C, 70°C, 75°C, 80°C, preferably a range value with any of the above numerical values ​​as the upper or lower limit, the time of the vacuum drying is preferably 180 to 300 min, more preferably 200 to 250 min, such as 180 min, 190 min, 200 min, 210 min, 220 min, 230 min, 240 min, 250 min, 260 min, 270 min, 280 min, 290 min, 300 min, preferably a range value with any of the above numerical values ​​as the upper or lower limit; the vacuum degree of the vacuum drying is preferably -0.08 to -0.09 MPa, more preferably -0.085 MPa.

[0034] After obtaining dry boron powder, the present invention places the dried boron powder into a boron nitride boat, then pushes it into one end of a quartz tube, and seals the other end of the quartz tube. Oxygen is introduced into the quartz tube to replace the air in the quartz tube. At the same time, the quartz tube is heated to an oxidation temperature and then kept warm to oxidize the surface of the high-purity boron powder to generate boron oxide.

[0035] In the present invention, a container made of boron nitride is used to hold boron powder, which can prevent the surface of high-purity boron from being contaminated again.

[0036] In the present invention, the flow rate of the oxygen is preferably 150 to 250 L / h, more preferably 180 to 220 L / h, such as 150 L / h, 160 L / h, 170 L / h, 180 L / h, 190 L / h, 200 L / h, 210 L / h, 220 L / h, 230 L / h, 240 L / h, 250 L / h, preferably a range value with any of the above values ​​as the upper or lower limit; the temperature of the oxidation is preferably 250 to 300°C, more preferably 260 to 280°C, such as 250°C, 260°C, 270°C, 280°C, 290°C, 300°C, preferably a range value with any of the above values ​​as the upper or lower limit; the holding time of the oxidation is preferably 2 to 4 hours, more preferably 2 to 3 hours.

[0037] After the oxidation is completed, the present invention introduces nitrogen and continues to increase the temperature to replace oxygen with the nitrogen flow, so that the boron oxide on the surface melts into liquid, and the boron oxide liquid is taken out by the air flow.

[0038] In the present invention, the flow rate of nitrogen is preferably 200-400 L / h, more preferably 250-350 L / h, such as 200 L / h, 220 L / h, 250 L / h, 280 L / h, 300 L / h, 320 L / h, 350 L / h, 380 L / h, 400 L / h, preferably a range value with any of the above values ​​as the upper or lower limit; after the nitrogen is introduced, the temperature is raised to 550-700°C, preferably 500-650°C, such as 550°C, 580°C, 600°C, 620°C, 650°C, 680°C, 700°C, preferably a range value with any of the above values ​​as the upper or lower limit; the insulation time is preferably 2-4 hours, more preferably 2-3 hours.

[0039] Then hydrogen is introduced, and the free bromine mixed in the liquid boron oxide reacts with the hydrogen to generate hydrogen bromide, which is discharged from the tail end of the quartz tube along with the air flow.

[0040] In the present invention, the flow rate of the hydrogen is preferably 100 to 500 L / h, more preferably 200 to 400 L / h, such as 100 L / h, 150 L / h, 200 L / h, 250 L / h, 300 L / h, 350 L / h, 400 L / h, 450 L / h, 500 L / h, preferably a range value with the above arbitrary numerical values ​​as the upper or lower limit; the reaction temperature is preferably 600 to 800°C, more preferably 650 to 750°C, such as 600°C, 650°C, 700°C, 750°C, 800°C, preferably a range value with the above arbitrary numerical values ​​as the upper or lower limit; the reaction time is preferably 8 to 16 hours, more preferably 10 to 15 hours.

[0041] The present invention provides a method for removing trace bromine from high-purity boron, comprising the following steps: A) crushing a high-purity boron block to obtain boron powder; B) washing and drying the boron powder, loading it into a boron nitride container and placing it in a quartz tube, introducing oxygen, and heating to oxidize the surface of the boron powder; C) introducing nitrogen and increasing the temperature after oxidation to melt the surface boron oxide; D) introducing hydrogen to react, with the generated hydrogen bromide discharged from the other end of the quartz tube. This method utilizes the fact that high-purity boron is easily oxidized and the resulting boron oxide melts at relatively low temperatures. The method first crushes the high-purity boron block, then introduces oxygen to oxidize the surface and increases the temperature to melt it, followed by hydrogenation to remove bromine. This method not only achieves deep removal of trace bromine from the boron block, but also removes metallic impurities on the boron surface. The method is simple to operate, pollution-free, highly efficient, easily scalable, and low-cost. The bromine content can be stably maintained at less than 20 ppb, meeting the requirements for use as an MBE source.

[0042] To further illustrate the present invention, a method for removing trace bromine in high-purity boron provided by the present invention is described in detail below with reference to examples, but this should not be construed as limiting the scope of protection of the present invention.

[0043] Example 1

[0044] First, high-purity boron blocks (prepared by hydroboration of boron bromide) were crushed into 20-mesh boron powder, cleaned with a 3wt% hydrofluoric acid solution, and vacuum-dried. A 130mm diameter quartz tube was pre-treated with ultrapure water and connected to a hydrogen line. Nine kilograms of the dried boron blocks (bromine content of 380 ppb, as measured by boron nitride powder) were placed in a boron nitride boat and transferred to one end of the quartz tube, while the other end was sealed.

[0045] First, introduce oxygen at a flow rate of 200 L / h into the quartz tube for 30 minutes to replace the air in the quartz tube, and heat it to 260°C and maintain it for 3 hours;

[0046] Then, nitrogen gas was introduced at a flow rate of 300 L / h, and the temperature of the quartz tube was raised at the same time. The temperature was designed to be maintained at 600°C for 3 hours.

[0047] Then, hydrogen gas was introduced at a flow rate of 120 L / h and reacted at 600°C for 3 hours. The free bromine contained in the boron block reacted with the hydrogen gas to generate hydrogen bromide, which was discharged from the tail end of the quartz tube along with the gas flow.

[0048] The purified boron powder was sampled and analyzed (the bromine content of the product after bromine removal was 15 ppb).

[0049] Example 2

[0050] First, high-purity boron blocks (prepared by hydroboration of boron bromide) were crushed into 20-mesh boron powder, cleaned with a 3wt% hydrofluoric acid solution, and vacuum-dried. A 130mm diameter quartz tube was pre-treated with ultrapure water and connected to a hydrogen line. Nine kilograms of the dried boron blocks (bromine content of 350 ppb, as measured by boron nitride powder) were placed in a boron nitride boat and transferred to one end of the quartz tube, while the other end was sealed.

[0051] First, introduce oxygen at a flow rate of 200 L / h into the quartz tube for 30 minutes to replace the air in the quartz tube, and heat it to 300°C and maintain it for 3 hours;

[0052] Then, nitrogen gas was introduced at a flow rate of 300 L / h, and the temperature of the quartz tube was raised at the same time. The temperature was designed to be 650°C and maintained for 3 hours.

[0053] Then, hydrogen gas was introduced at a flow rate of 200 L / h and reacted at 650°C for 3 hours. The free bromine contained in the boron block reacted with the hydrogen gas to generate hydrogen bromide, which was discharged from the tail end of the quartz tube along with the air flow.

[0054] The purified boron powder was taken and the product was sampled and analyzed (the bromine content of the product after bromination was 5 ppb).

[0055] Comparative Example 1

[0056] Trace bromine in the high-purity boron block was removed according to the preparation method of Example 2, except that the hydrogen gas flow step was omitted in Comparative Example 1. The purified boron powder was taken and the product was sampled and analyzed (the bromine content of the product after bromine removal was 105 ppb).

[0057] Comparative Example 2

[0058] The trace bromine in the high-purity boron block was removed according to the preparation method of Example 2, except that the sample of Comparative Example 2 was not crushed. The purified boron powder was taken and the product was sampled and analyzed (the bromine content of the product after bromine removal was 55 ppb).

[0059] Comparative Example 3

[0060] Trace bromine was removed from the high-purity boron block according to the preparation method of Example 2, except that in Comparative Example 3, the temperature was not increased during the nitrogen flow step, and the boron oxide was not melted. The product was sampled and analyzed (the bromine content of the product after bromine removal was 300 ppb).

[0061] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A method for removing trace bromine from high-purity boron, comprising the following steps: A) crushing high-purity boron blocks to obtain boron powder; B) washing and drying the boron powder, placing it in a boron nitride container in a quartz tube, introducing oxygen, and heating to oxidize the surface of the boron powder; the oxidation temperature in step B) is 250-300° C.; C) After the oxidation is completed, nitrogen is introduced and the temperature is raised to 550-700°C to melt the boron oxide on the surface; D) hydrogen gas is introduced to react, and the generated hydrogen bromide is discharged from the other end of the quartz tube; The flow rate of the hydrogen is 100-500 L / h; the reaction temperature in step D) is 600-800°C.

2. The removal method according to claim 1, characterized in that The high-purity boron block is prepared by hydroboration of bromide.

3. The removal method according to claim 1, characterized in that The particle size of the boron powder is 10 to 30 meshes.

4. The removal method according to claim 1, characterized in that Wash the boron powder with an acid solution; The acid aqueous solution is a hydrofluoric acid aqueous solution and / or a nitric acid aqueous solution; the mass concentration of the acid aqueous solution is 1 to 10 wt%.

5. The removal method according to claim 1, characterized in that: The cleaned boron powder is vacuum dried at a temperature of 60 to 80° C. and for a time of 180 to 300 minutes.

6. The removal method according to claim 1, characterized in that: The oxidation time in step B) is 2 to 4 hours.

7. The removal method according to claim 5, characterized in that: The flow rate of the oxygen is 150 to 250 L / h.

8. The removal method according to claim 1, characterized in that: The flow rate of nitrogen in step C) is 200-400 L / h.

9. The removal method according to claim 7, characterized in that: The holding time in step C) is 2 to 4 hours.

10. The removal method according to claim 1, characterized in that: The reaction time in step D) is 8 to 16 hours.

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