Production process of boron oxide

Abstract

The present invention provides a production process of boron oxide, which comprises the following steps: Step 1, raw material calcination. After drying the raw material boric acid powder, it is added into the melting container of a vacuum furnace, and the raw material boric acid powder in the melting container is heated to 800°C - 1000°C for atmospheric calcination to obtain a molten liquid; Step 2, vacuum heating. The molten liquid is heated to 1400°C - 1600°C, the vacuum furnace is evacuated to a pressure between 100 Pa and 300 Pa inside the furnace, and after the liquid level is stable, the pressure inside the furnace is restored to atmospheric pressure to obtain a first liquid product; Step 3, secondary vacuum. The first liquid product is stirred, then the vacuum furnace is evacuated to a pressure less than or equal to 80 Pa inside the furnace, the evacuation is stopped and the pressure inside the furnace is maintained until no bubbles are generated on the liquid surface, and then the pressure inside the furnace is restored to atmospheric pressure to obtain a second liquid product; Step 4, casting and forming. The second liquid product is cast and then cooled and demolded to obtain a boron oxide product. The water content of the boron oxide product produced by the present invention is less than or equal to 120 ppm.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor crystal growth covering agents, and particularly to a production process of boron oxide. Background Art

[0002] In recent years, with the continuous development of the chip industry, the domestic chip production capacity has increased, and the demand for high-purity boron oxide has been increasing, with higher and higher technical requirements. At present, the moisture content of existing boron oxide products is basically around 200 PPM. The fourth-generation semiconductor materials have higher and higher requirements for the moisture of boron oxide. Some require boron oxide products with a moisture content below 120 PPM. The moisture content of existing boron oxide products can no longer meet the requirements. The above problems need to be solved urgently. Summary of the Invention

[0003] In order to solve the problems in the background art, the present invention provides a production process of boron oxide, which includes the following steps:

[0004] Step 1, raw material calcination: After drying the raw material boric acid powder, add it into the melting container of the vacuum furnace, heat the boric acid powder in the melting container to 800°C - 1000°C, and perform atmospheric calcination to obtain a molten liquid;

[0005] Step 2, vacuum heating: Heat the molten liquid to 1400°C - 1600°C, evacuate the vacuum furnace to a pressure between 100 Pa and 300 Pa inside the furnace. After the liquid level is stable, restore the pressure inside the furnace to atmospheric pressure to obtain a first liquid product;

[0006] Step 3, secondary vacuum: Stir the first liquid product, then evacuate the vacuum furnace to a pressure less than or equal to 80 Pa inside the furnace. Stop evacuating and maintain the pressure inside the furnace until no bubbles are generated on the liquid surface, and then restore the pressure inside the furnace to atmospheric pressure to obtain a second liquid product;

[0007] Step 4, casting and molding: Cast the second liquid product and then cool and demold it to obtain a boron oxide product.

[0008] In the production process of boron oxide of the present invention, in step 2, evacuating the vacuum furnace to a pressure between 100 Pa and 300 Pa inside the furnace is carried out in multiple times. Each time, stop evacuating when the pressure inside the furnace drops to the boiling point of the molten liquid surface. After the molten liquid surface is stable and no bubbles are generated, continue to evacuate. Repeat the above operations until the pressure inside the furnace is between 100 Pa and 300 Pa.

[0009] In the production process of boron oxide of the present invention, after the pressure inside the furnace reaches 100 Pa - 300 Pa in step 2, maintain the pressure inside the furnace for at least 15 minutes, and then restore the pressure inside the furnace to atmospheric pressure.

[0010] In the production process of boron oxide of the present invention, the step of evacuating the vacuum furnace to a pressure inside the furnace less than or equal to 80 Pa in step three includes the following steps:

[0011] Evacuate the vacuum furnace to a pressure inside the furnace of 100 - 300 Pa (in 2 - 3 minutes, all at once), stop evacuating, and maintain the pressure inside the furnace for 12 - 13 minutes;

[0012] The vacuum furnace continues to be evacuated to a pressure inside the furnace of 50 Pa - 80 Pa.

[0013] In the production process of boron oxide of the present invention, after stopping the evacuation in step three, no bubbles are generated on the liquid surface within 1 minute, and then the pressure inside the furnace is restored to normal pressure to obtain a second liquid product.

[0014] In the production process of boron oxide of the present invention, before stirring in step three, the detection samples and unqualified products from the previous furnace are added to the melting container.

[0015] In the production process of boron oxide of the present invention, the step of casting the second liquid product and then cooling and demolding to obtain a boron oxide product in step four includes the following steps:

[0016] Cool the second liquid product to 900 °C - 1100 °C and then cast it to obtain a casting;

[0017] Cool the casting to 450 °C - 550 °C for demolding to obtain a demolded product;

[0018] Cool the demolded product to 30 °C under vacuum conditions and then package it to obtain a boron oxide product.

[0019] In the production process of boron oxide of the present invention, the time for calcination at normal pressure in step one is 15 minutes.

[0020] In the production process of boron oxide of the present invention, after the raw material boric acid powder is dried, it is added to the melting container of the vacuum furnace in batches. When adding each batch of materials, it should be added after the raw material boric acid powder in the melting container is completely melted and the liquid surface is stable.

[0021] In the production process of boron oxide of the present invention, the raw material boric acid powder is 6N boric acid powder.

[0022] The beneficial effects of the present invention are as follows: The production process of boron oxide of the present invention can effectively reduce the water content in the boron oxide product based on increasing the calcination temperature, cooperating with vacuum exhaust, and secondary vacuum exhaust after stirring, so that the water content of the product boron oxide is reduced to less than 120 ppm, which can meet the current requirements for the water content of boron oxide products. Detailed implementation manners

[0023] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions in the embodiments of this application will be clearly and completely described below. Obviously, the described embodiments are part of the embodiments of this application, rather than all of them. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in this application without creative efforts belong to the scope of protection of this application.

[0024] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the technical field to which this application belongs; the terms used in the specification of this application are only for the purpose of describing specific embodiments and are not intended to limit this application; the terms "including" and "having" and any variations thereof in the specification and claims of this application are intended to cover non-exclusive inclusion.

[0025] Referring to "embodiments" herein means that specific features, structures, or characteristics described in connection with the embodiments can be included in at least one embodiment of this application. The phrase appears in various places in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment mutually exclusive with other embodiments. Those skilled in the art will explicitly and implicitly understand that the embodiments described herein can be combined with other embodiments.

[0026] The following details a production process of boron oxide according to the present invention, which includes the following steps:

[0027] Step 1: Raw material calcination. After drying the raw material boric acid powder (the raw material boric acid powder is 6N boric acid powder), it is added into the melting container (the melting container is a crucible arranged in a vacuum furnace) of the vacuum furnace. The raw material boric acid powder in the melting container is heated to 800°C - 1000°C for atmospheric pressure calcination (calcination for 15 minutes or the calcination time is determined according to the existing process), and a molten liquid is obtained.

[0028] Specifically, after drying the raw material boric acid powder, it is added to the melting container of the vacuum furnace in batches. When adding each batch of materials, it should be added after the raw material boric acid powder in the melting container is completely melted and the liquid level is stable.

[0029] Step 2: Vacuum heating. The molten liquid is heated to 1400°C - 1600°C, and the vacuum furnace is evacuated to a pressure between 100 Pa and 300 Pa inside the furnace. After the liquid level is stable (the liquid level is stable, that is, the liquid level is bubbling and the liquid does not splash out or there are no bubbles. Generally, it is sufficient when the liquid level is bubbling and the liquid does not splash out), the pressure inside the furnace is restored to atmospheric pressure (specifically, after the pressure inside the furnace reaches 100 Pa - 300 Pa, the pressure inside the furnace is maintained for at least 15 minutes, and then the pressure inside the furnace is restored to atmospheric pressure. Usually, it is sufficient to maintain the pressure inside the furnace for 15 minutes, specifically based on no bubbles appearing on the liquid level). A first liquid product is obtained.

[0030] Preferably, in step two, the vacuum furnace is evacuated to a pressure between 100 Pa and 300 Pa in multiple times. Each time, the evacuation is stopped after the pressure in the furnace is reduced to the boiling point of the molten liquid surface (the pressure reduction speed should be controlled to avoid missing the boiling pressure). After the molten liquid surface is stable and no bubbles are generated, the evacuation is continued. Repeat the above operation until the pressure in the furnace is between 100 Pa and 300 Pa; based on multiple evacuation operations, the volatilization of materials is reduced and the product yield is increased.

[0031] Specifically, for example, when evacuating for the first time at 1500 °C to about 2000 Pa, the liquid boils. After that, each time the pressure in the vacuum furnace is reduced by about 150 Pa until the liquid boils, which can be specifically determined according to the temperature of the vacuum furnace.

[0032] Step three, secondary vacuum. Stir the first liquid product (maintaining the temperature in the furnace at this time, that is, the temperature of the first liquid product is the same as the temperature during calcination), and then evacuate the vacuum furnace to a pressure less than or equal to 80 Pa. Stop evacuating and maintain the pressure in the furnace until no bubbles are generated on the liquid surface, and then restore the pressure in the furnace to normal pressure to obtain the second liquid product; specifically, observe that no bubbles are generated on the liquid surface within 1 minute, and then restore the pressure in the furnace to normal pressure (the observation time should not be too long. If the time exceeds 1 minute, the moisture content of boron oxide in the product will not decrease significantly, but instead, the volatilization amount will increase due to too long observation time, resulting in a decrease in the product yield). Based on the secondary vacuum combined with stirring, the moisture content in the product boron oxide can be further reduced.

[0033] Specifically, evacuating the vacuum furnace to a pressure less than or equal to 80 Pa in step three includes the following steps S1-2:

[0034] Step S1, evacuate the vacuum furnace to a pressure of 100 - 300 Pa at one time (evacuate at one time), stop evacuating, and maintain the pressure in the furnace for 12 - 13 minutes;

[0035] Step S2, continue to evacuate the vacuum furnace to a pressure of 50 Pa - 80 Pa. The pressure should not be too low, otherwise the product volatilization will be serious and affect the yield. Nor should it be too high, otherwise the moisture content of the product will increase.

[0036] Furthermore, before stirring in step three, add the detection samples of the previous furnace and unqualified products (products with bubbles or unqualified gram weight) into the melting container. This reduces product waste. It should be noted that the detection samples and unqualified products cannot be added with the raw material boric acid powder. If added with the raw materials, the moisture content in the detection samples and unqualified products cannot be reduced during the first vacuum heating (step two), and it will increase the heating load and prolong the processing time.

[0037] Step 4: Casting and forming. Cast the second liquid product and then cool it to demold, obtaining a boron oxide product.

[0038] Specifically, the process of casting the second liquid product and then cooling it to demold to obtain a boron oxide product in Step 4 includes the following steps M1 - 3:

[0039] Step M1: Cool the second liquid product to 900°C - 1100°C and then cast it to obtain a cast product.

[0040] Step M2: Cool the cast product to 450°C - 550°C for demolding to obtain a demolded product.

[0041] Step M3: Cool the demolded product to 30°C under vacuum conditions and then encapsulate it to obtain a boron oxide product.

[0042] The production process of boron oxide in the present invention is based on increasing the calcination temperature, combined with vacuum exhaust and secondary vacuum exhaust after stirring, which can effectively reduce the water content in the boron oxide product, making the water content of the boron oxide product reduced to below 120 ppm, meeting the current requirements for the water content of boron oxide products, and reducing the processing time of the product; and the production process of the present invention can significantly shorten the vacuum time. The vacuum operation time of the present invention is about 50 minutes (the existing process generally requires 90 minutes).

[0043] Example 1

[0044] Step 1: Dry the raw material boric acid powder and add it to the melting container of the vacuum furnace. Heat the raw material boric acid powder in the melting container to 1000°C for atmospheric calcination to obtain a molten liquid.

[0045] Step 2: Raise the temperature of the molten liquid to 1600°C. Vacuumize the vacuum furnace once to make the pressure in the furnace 300 Pa. After the liquid surface is stable, restore the pressure in the furnace to atmospheric pressure to obtain a first liquid product.

[0046] Step 3: Stir the first liquid product for 2 - 3 minutes, then vacuumize the vacuum furnace once to make the pressure in the furnace 80 Pa. Vacuumize and maintain the pressure in the furnace at 80 Pa until no bubbles are generated on the liquid surface, and then restore the pressure in the furnace to atmospheric pressure to obtain a second liquid product.

[0047] Step 4: Cast the second liquid product and then cool it to demold, obtaining a boron oxide product.

[0048] Product detection:

[0049] After detection, the water content in the boron oxide product is: 90 ppm; the product yield is: 70%.

[0050] Example 2

[0051] Step 1: After drying the raw material boric acid powder, add it into the melting container of the vacuum furnace. Heat the boric acid powder in the melting container to 1000 °C and conduct atmospheric calcination to obtain a molten liquid;

[0052] Step 2: Raise the temperature of the molten liquid to 1400 °C. Vacuum the vacuum furnace once to make the pressure in the furnace 100 Pa. After the liquid level stabilizes, restore the pressure in the furnace to atmospheric pressure to obtain the first liquid product;

[0053] Step 3: Stir the first liquid product for 2 - 3 minutes, then vacuum the vacuum furnace once to make the pressure in the furnace 50 Pa. Vacuum and maintain the pressure in the furnace at 50 Pa until no bubbles are generated on the liquid surface, and then restore the pressure in the furnace to atmospheric pressure to obtain the second liquid product;

[0054] Step 4: Cast the second liquid product and then cool and demold it to obtain a boron oxide product.

[0055] Product detection:

[0056] After detection, the water content in the boron oxide product is: 110 ppm; the product yield is: 70%.

[0057] Example 3

[0058] Step 1: After drying the raw material boric acid powder, add it into the melting container of the vacuum furnace. Heat the boric acid powder in the melting container to 1000 °C and conduct atmospheric calcination to obtain a molten liquid;

[0059] Step 2: Raise the temperature of the molten liquid to 1500 °C. Vacuum the vacuum furnace once to make the pressure in the furnace 200 Pa. After the liquid level stabilizes, restore the pressure in the furnace to atmospheric pressure to obtain the first liquid product;

[0060] Step 3: Stir the first liquid product for 2 - 3 minutes, then vacuum the vacuum furnace once to make the pressure in the furnace 65 Pa. Vacuum and maintain the pressure in the furnace at 65 Pa until no bubbles are generated on the liquid surface, and then restore the pressure in the furnace to atmospheric pressure to obtain the second liquid product;

[0061] Step 4: Cast the second liquid product and then cool and demold it to obtain a boron oxide product.

[0062] Product detection:

[0063] After detection, the water content in the boron oxide product is: 100 ppm; the product yield is: 70%.

[0064] Example 4

[0065] The difference between this example and Example 1 is that in Step 2, the vacuuming of the vacuum furnace to make the pressure in the furnace 200 Pa is carried out in multiple times, and the rest is the same as Example 1.

[0066] Product testing:

[0067] After testing, the water content in the boron oxide product is: 100 ppm; the product yield is: 85%.

[0068] Example 5

[0069] The difference between this example and Example 1 is that in Step 3, the vacuum furnace is evacuated to an internal pressure of 65 Pa in two stages. First, it is evacuated to an internal pressure of 200 Pa and maintained for 12 minutes, and then it is evacuated again to 65 Pa. The rest is the same as in Example 1.

[0070] Product testing:

[0071] After testing, the water content in the boron oxide product is: 95 ppm; the product yield is: 70%.

[0072] Example 6

[0073] The difference between this example and Example 1 is that in Step 2, the vacuum furnace is evacuated to an internal pressure of 200 Pa in multiple stages, and in Step 3, the vacuum furnace is evacuated to an internal pressure of 65 Pa in two stages. First, it is evacuated to an internal pressure of 200 Pa and maintained for 12 minutes, and then it is evacuated again to 65 Pa. The rest is the same as in Example 1.

[0074] Product testing:

[0075] After testing, the water content in the boron oxide product is: the average water content is 95 ppm; the product yield is: 95%.

[0076] Comparative Example 1

[0077] The difference between this comparative example and Example 1 is that in Step 3, the vacuum furnace is evacuated to an internal pressure of 100 Pa in one step. The rest is the same as in Example 1.

[0078] Product testing:

[0079] After testing, the water content in the boron oxide product is: the average water content is 110 ppm; the product yield is: 80%.

[0080] Comparative Example 2

[0081] The difference between this comparative example and Example 1 is that in Step 3, the vacuum furnace is evacuated to an internal pressure of 40 Pa in one step. The rest is the same as in Example 1.

[0082] Product testing:

[0083] After testing, the water content in the boron oxide product is: 85 ppm; the product yield is: 55%.

[0084] Comparative Example 3

[0085] The difference between this comparative example and Example 1 is that in Step 2, the molten liquid is heated to 1200 °C, and the rest is the same as in Example 1.

[0086] Product detection:

[0087] After detection, the water content in the boron oxide product is: 165 ppm; the product yield is: 95%.

[0088] Comparative Example 4

[0089] The difference between this comparative example and Example 1 is that in Step 3, stirring is not carried out, and the rest is the same as in Example 1.

[0090] Product detection:

[0091] After detection, the water content in the boron oxide product is: 135 ppm; the product yield is: 70%.

[0092] It can be seen from the above examples and comparative examples that the production process of boron oxide of the present invention can significantly reduce the water content of the boron oxide product. Especially under the conditions of Example 6, by adopting secondary vacuum + stirring, and the vacuum extraction in Step 2 and Step 3 is carried out multiple times, it can not only ensure the water content of the boron oxide product, but also has a high product yield. And referring to Comparative Example 2, when the secondary vacuum pressure exceeds the required range of the present invention, the yield drops significantly. In Comparative Example 4, without stirring, the water content of the product increases significantly.

[0093] And in actual production, due to problems such as aging of processing equipment, the water content of boron oxide in different batches of products will fluctuate. For example, when using the same equipment to produce multiple times according to the conditions of Example 1, the water content of the boron oxide product will fluctuate in the range of 90 - 110 ppm. Under the conditions of Example 6, when producing multiple times, the water content of the boron oxide product fluctuates in the range of 90 - 100 ppm. It can be seen that under the conditions of Example 6, the fluctuation of the water content of the boron oxide product in multiple productions can be reduced, which is helpful to obtain a product with a more stable water content. Under the conditions of Comparative Examples 3 and 4, the water content of the boron oxide product obtained from multiple productions is in the range of 150 - 180 ppm and 120 - 150 ppm. It can be seen that the water content of the boron oxide product prepared by the production process of boron oxide of the present invention through multiple productions is more stable and has less fluctuation.

Claims

1. A production process of boron oxide, characterized in that, It includes the following steps: Step 1, raw material calcination: After drying the raw material boric acid powder, add it into the melting container of the vacuum furnace, heat the boric acid powder in the melting container to 800°C - 1000°C, and conduct atmospheric pressure calcination to obtain a molten liquid; Step 2, vacuum heating: Heat the molten liquid to 1400°C - 1600°C, evacuate the vacuum furnace to a pressure between 100 Pa and 300 Pa inside the furnace. After the liquid level is stable, restore the pressure inside the furnace to atmospheric pressure to obtain a first liquid product; Step 3, secondary vacuum: Stir the first liquid product, then evacuate the vacuum furnace to a pressure less than or equal to 80 Pa inside the furnace, stop evacuating and maintain the pressure inside the furnace until no bubbles are generated on the liquid surface, and then restore the pressure inside the furnace to atmospheric pressure to obtain a second liquid product; Step 4, casting and molding: Cast the second liquid product and then cool and demold it to obtain a boron oxide product.

2. The production process of boron oxide according to claim 1, characterized in that, In step 2, evacuating the vacuum furnace to a pressure between 100 Pa and 300 Pa inside the furnace is carried out in multiple times. Each time, stop evacuating when the pressure inside the furnace drops to the point where the liquid surface of the molten liquid boils, and continue evacuating after the liquid surface of the molten liquid is stable and no bubbles are generated. Repeat the above operation until the pressure inside the furnace is between 100 Pa and 300 Pa.

3. The production process of boron oxide according to claim 1, characterized in that After the pressure inside the furnace reaches 100 Pa - 300 Pa in step 2, maintain the pressure inside the furnace for greater than or equal to 15 minutes, and then restore the pressure inside the furnace to atmospheric pressure.

4. The production process of boron oxide according to claim 1, characterized in that, The step of evacuating the vacuum furnace to a pressure less than or equal to 80 Pa in step 3 includes the following steps: Evacuate the vacuum furnace to a pressure of 100 - 300 Pa inside the furnace at one time, stop evacuating, and maintain the pressure inside the furnace for 1 minute; The vacuum furnace continues to evacuate to a pressure of 50 Pa - 80 Pa inside the furnace.

5. The production process of boron oxide according to claim 1, characterized in that, In step 3, no bubbles are generated on the liquid surface within 1 minute after stopping evacuating, and then the pressure inside the furnace is restored to atmospheric pressure to obtain a second liquid product.

6. The production process of boron oxide according to claim 1, characterized in that, Before stirring in step 3, add the test samples and unqualified products of the previous furnace into the melting container.

7. The production process of boron oxide according to claim 1, characterized in that, The step of casting the second liquid product and then cooling and demolding it to obtain a boron oxide product in step 4 includes the following steps: Cool the second liquid product to 900°C - 1100°C and then cast it to obtain a casting; Cool the casting to 450°C - 550°C for demolding to obtain a demolded product; Cool the demolded product to 30°C under vacuum conditions and then package it to obtain a boron oxide product.

8. The production process of boron oxide according to claim 1, characterized in that, The time for atmospheric pressure calcination in step 1 is 15 minutes.

9. The production process of boron oxide according to claim 1, characterized in that, After drying the raw material boric acid powder in step 1, add it to the melting container of the vacuum furnace in batches. When adding each batch of materials, it should be added after the boric acid powder in the melting container is completely melted and the liquid surface is stable.

10. The production process of boron oxide according to claim 1, characterized in that, The raw material boric acid powder is 6N boric acid powder.