Recovery method of arsenic-containing quartz tube

Abstract

The invention belongs to the technical field of semiconductor material and equipment recovery, and particularly relates to a recovery method of an arsenic-containing quartz tube. The recycling method comprises the following steps that a pipe opening of an arsenic-containing quartz pipe is sealed through a graphite plug with an air inlet hole and an exhaust hole, then the arsenic-containing quartz pipe is placed in a horizontal heating furnace, the air inlet hole of the graphite plug is connected with an air inlet pipe, the exhaust hole is connected with an exhaust pipe, and the exhaust pipe is sequentially connected with a cooling water recycling device and an acid tail gas treatment device; and heating the quartz tube to 615-650 DEG C through a horizontal heating furnace, carrying out heating arsenic removal treatment on the quartz tube, cleaning the quartz tube subjected to heating arsenic removal treatment in a pickling solution, and finally carrying out dehydroxylation treatment to obtain the recycled quartz tube. Compared with a conventional strong acid soaking and acid pickling method, the recycling method can effectively avoid potholes and cracks caused by strong acid corrosion, residual arsenic passing through the quartz tube can be recycled, arsenic-containing waste liquid is not generated, and environmental pollution and resource waste are reduced.

Description

Technical Field

[0001] The invention belongs to the technical field of semiconductor material and equipment recovery, and in particular relates to a recovery method for an arsenic-containing quartz tube. Background Art

[0002] Quartz material has excellent properties such as high temperature resistance, small thermal expansion coefficient, excellent light transmittance, good electrical insulation, and corrosion resistance. It is one of the key raw materials in the semiconductor industry. For example, quartz tubes are needed in the preparation of high-purity arsenic and gallium arsenide crystals. After the preparation of high-purity arsenic or gallium arsenide crystals, some arsenic slag often remains on the inner wall of the quartz tube. The existing technology removes the arsenic slag on the inner wall of the quartz tube by corroding it with a strong acid, and then rinsing it with pure water. The quartz tube can be reused. For example, patent CN 109136568B discloses a resource processing method for arsenic-containing quartz tubes. By sequentially soaking in strong acids, the arsenic element, arsenic trioxide, and gallium arsenide on the surface of the quartz tube are oxidized to form As-containing 3+ and As 5+ Arsenic-containing solution will form a layer of arsenic trioxide film on the surface of the quartz tube; mixed acid cleaning will oxidize the arsenic trioxide on the surface of the quartz tube after soaking in strong acid to arsenic pentoxide, and then form arsenic acid in the solution; and tap water flushing will clean the mixed acid attached to the surface of the quartz tube and recycle the quartz tube. However, under the corrosion of strong acid, arsenic will react with quartz, causing pits inside the quartz tube and even cracking the quartz tube, affecting the service life of the quartz tube. At the same time, arsenic will also react with strong acid to form arsenic-containing waste liquid, and the arsenic slag cannot be recycled, and it will also pollute the environment.

[0003] In addition, strong acid immersion and pickling treatment will destroy the chemical bonds on the quartz surface, resulting in the formation of hydroxyl groups, making the hydroxyl content on the surface of the quartz tube too high. The hydroxyl group in the quartz tube has an important influence on the growth process of semiconductor single crystals. If the hydroxyl group is too high, it will lead to uneven temperature during the growth process and affect the yield of crystal growth. Conventional quartz tube dehydroxylation methods generally use vacuum high temperature (800-1100°C) dehydroxylation treatment, but long-term high temperature dehydroxylation treatment will cause crystallization on the surface of the quartz tube to a certain extent, which will also affect the success rate of semiconductor single crystal growth and the quality of the crystal rod. Summary of the invention

[0004] In view of the shortcomings and deficiencies of the above prior art, the object of the present invention is to provide a method for recovering arsenic-containing quartz tubes.

[0005] The purpose of the present invention is achieved through the following technical solutions:

[0006] A method for recovering arsenic-containing quartz tubes comprises the following steps:

[0007] (1) The tube mouth of the arsenic-containing quartz tube is sealed with a graphite plug with an air inlet hole and an air outlet hole, and then placed in a horizontal heating furnace, the air inlet hole of the graphite plug is connected to an air inlet pipe, the air outlet hole is connected to an exhaust pipe, and the exhaust pipe is connected to a cooling water recovery device and an acid tail gas treatment device in sequence;

[0008] (2) heating the quartz tube treated in step (1) to 615-650° C. in a horizontal heating furnace to convert solid arsenic in the quartz tube into arsenic vapor, introducing an inert gas through an air inlet pipe while heating, so that the arsenic vapor is discharged through an exhaust pipe to a cooling water recovery device to cool and solidify into arsenic particles, and the remaining gas enters an acid tail gas treatment device;

[0009] (3) placing the quartz tube treated in step (2) into an acid wash solution to remove impurities on the inner wall of the quartz tube, then rinsing with pure water, and drying to obtain a cleaned quartz tube;

[0010] (4) The quartz tube treated in step (3) is subjected to a dehydroxylation treatment to obtain a recovered quartz tube.

[0011] Furthermore, the air inlet pipe in step (1) is extended to the middle of the quartz tube to facilitate gas filling and exhaust of arsenic vapor from the exhaust pipe.

[0012] Furthermore, in step (1), ultrapure water with a temperature of 10-18° C. is used in the cooling water recovery device to prevent the introduction of impurities and improve the purity of the recovered arsenic particles.

[0013] Furthermore, in step (1), the acidic tail gas treatment device uses a nitric acid aqueous solution with a mass fraction of 5% to 20%. The acidic tail gas treatment device can further absorb the residual arsenic vapor and harmful gases generated by heating.

[0014] Furthermore, the inert gas in step (2) is nitrogen or argon. Nitrogen is preferred because of its low price.

[0015] Furthermore, the pickling solution in step (3) is a mixed aqueous solution of 1% to 10% by mass of hydrofluoric acid and 10% to 35% by mass of nitric acid; and the cleaning refers to immersion cleaning for 5 to 30 minutes.

[0016] Furthermore, the steps of the dehydroxylation treatment in step (3) are as follows:

[0017] The quartz tube is heated to 80-100°C, and then the hydrolyzed silane coupling agent atomized liquid is sprayed in the quartz tube, and the coupling reaction is kept at a temperature of 1-15 minutes. After cooling to room temperature, the tube is rinsed with pure water, and then heated to 500-700°C for heat treatment for 1-6 hours to obtain a quartz tube after dehydroxylation treatment.

[0018] Conventional heat treatment directly decomposes hydroxyl groups from the surface of the quartz tube by breaking Si-O bonds, but Si-O bonds have large bond energy, and require high temperatures and long times to achieve good dehydroxylation effects. However, long-term high-temperature heat treatment will cause the flatness and crystal structure of the quartz tube to change, affecting its performance. The present invention first converts hydroxyl groups into highly stable Si-O-Si bonds through a chemical coupling reaction of a silane coupling agent, and then breaks and decomposes the Si-C bonds of the silane coupling agent through heat treatment to generate SiO2 with the same composition as the quartz tube, thereby achieving an efficient dehydroxylation effect. At the same time, the bond energy of the Si-C bond rupture is significantly lower than that of the Si-O bond, so that efficient removal of coupling byproducts can be achieved at a lower heat treatment temperature. In addition, after pickling and impurity removal, the surface of the quartz tube will be corroded to a certain extent. In the corroded parts (concentrated in the parts with high arsenic and metal impurity content), the Si-O chemical bond is broken and reacts with water to produce a high content of new hydroxyl groups. Therefore, the subsequent coupling reaction is more concentrated in the corroded parts. In the further heat treatment process, more SiO2 is generated in the corroded parts, thereby achieving a certain self-repairing effect, improving the surface flatness and uniformity of the quartz tube, and thus improving the recycling application effect.

[0019] Furthermore, the silane coupling agent is selected from methyltrimethoxysilane or methyltriethoxysilane. The above silane coupling agent has high chemical coupling activity with hydroxyl groups and does not introduce other impurity elements.

[0020] Furthermore, the hydrolyzed silane coupling agent atomized liquid is prepared by the following method:

[0021] The silane coupling agent is added to the isopropanol solution to dilute it to a mass concentration of 10% to 50%, and then pure water is added under normal temperature conditions to stir and hydrolyze for 0.5 to 2 hours. The obtained hydrolyzate is atomized by an atomizing spray device to obtain a hydrolyzed silane coupling agent atomized liquid.

[0022] Further preferably, the amount of pure water added is 5% to 40% of the mass of the silane coupling agent.

[0023] Furthermore, the hydroxyl value of the quartz tube after the dehydroxylation treatment is lower than 10 ppm; more preferably, the hydroxyl value is lower than 5 ppm.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] (1) Compared with conventional strong acid immersion and pickling methods, the recovery method of the arsenic-containing quartz tube of the present invention can effectively avoid pits and cracks caused by strong acid corrosion, and the quartz tube has a long service life and can be reused many times.

[0026] (2) The residual arsenic in the quartz tube in the recovery method of the present invention can be recycled without generating arsenic-containing waste liquid, thereby reducing environmental pollution and waste of resources.

[0027] (3) The recycling method of the present invention further adopts a dehydroxylation treatment method combining chemical coupling with heat treatment, which can significantly improve the dehydroxylation effect and reduce the temperature of heat treatment dehydroxylation, thereby avoiding the influence of long-term high-temperature heat treatment on the performance of the quartz tube. At the same time, the dehydroxylation treatment method of the present invention can also repair the surface flatness and uniformity reduction caused by pickling corrosion to a certain extent, thereby improving the recycling and application effect of the quartz tube. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 The schematic diagram of the structure of a recovery device of a method for recovering arsenic-containing quartz tubes in an embodiment of the present invention is as follows: 1-inlet pipe, 2-outlet pipe, 3-graphite plug, 4-cooling water recovery device, 5-acid tail gas treatment device, 6-horizontal heating furnace, 7-quartz tube, 8-arsenic slag. DETAILED DESCRIPTION

[0029] The present invention is further described in detail below in conjunction with embodiments and drawings, but the embodiments of the present invention are not limited thereto.

[0030] Example 1

[0031] A method for recovering arsenic-containing quartz tubes comprises the following steps:

[0032] (1) The mouth of the arsenic-containing quartz tube is sealed with a graphite plug with an air inlet and an air outlet, and then placed in a horizontal heating furnace. The air inlet of the graphite plug is connected to an air inlet pipe, which extends to the middle of the quartz tube to facilitate gas filling and exhaust of arsenic vapor; the air outlet is connected to an exhaust pipe, which is connected in turn to a cooling water recovery device and an acid tail gas treatment device. The structural schematic diagram of the recovery device is shown in FIG. Figure 1 shown.

[0033] (2) The quartz tube treated in step (1) is heated to 630°C in a horizontal heating furnace to convert the solid arsenic in the quartz tube into arsenic vapor. While heating, nitrogen is introduced through the air inlet pipe to discharge the arsenic vapor through the exhaust pipe to the cooling water recovery device to cool and solidify into arsenic particles. Ultrapure water at a temperature of 15°C is used in the cooling water recovery device. The remaining gas enters the acid tail gas treatment device for further absorption treatment. A nitric acid aqueous solution with a mass fraction of 10% is used in the acid tail gas treatment device. After all the arsenic slag in the quartz tube is converted into arsenic vapor and discharged from the quartz tube, nitrogen is continuously introduced, heating is stopped, the quartz tube is cooled to room temperature, and the nitrogen is then turned off.

[0034] (3) The quartz tube treated in step (2) is immersed in an acid cleaning solution for 20 minutes, wherein the acid cleaning solution is a mixed aqueous solution of 4.9% hydrofluoric acid by mass and 14.2% nitric acid by mass, to remove metal impurities on the inner wall of the quartz tube, and then rinsed with pure water and dried to obtain a quartz tube with impurities removed.

[0035] (4) Methyltrimethoxysilane was added to an isopropanol solution and diluted to a mass concentration of 35%, and then pure water was added at room temperature and stirred for hydrolysis reaction for 1 hour. The amount of pure water added was 12% of the mass of methyltrimethoxysilane. The obtained hydrolyzate was sprayed onto the inner surface of a de-impurity quartz tube preheated to 90°C by an atomizing spray device, and the reaction was kept at a temperature for 10 minutes. After cooling to room temperature, the solution was rinsed with pure water, and then heated to 600°C for 3 hours under normal air conditions to obtain a quartz tube after dehydroxylation. The hydroxyl value of the de-hydroxylation quartz tube was 3.5ppm as determined by ICP-MS. The total impurity content (including arsenic, aluminum, iron, sodium, potassium, and lithium) was less than 10ppm. There were no pits or cracks on the inner wall of the quartz tube.

[0036] Example 2

[0037] A method for recovering arsenic-containing quartz tubes comprises the following steps:

[0038] Step (1) is the same as in Example 1.

[0039] (2) The quartz tube treated in step (1) is heated to 615°C in a horizontal heating furnace to convert the solid arsenic in the quartz tube into arsenic vapor. While heating, nitrogen is introduced through the air inlet pipe to discharge the arsenic vapor through the exhaust pipe to the cooling water recovery device to cool and solidify into arsenic particles. Ultrapure water at a temperature of 18°C ​​is used in the cooling water recovery device. The remaining gas enters the acid tail gas treatment device for further absorption treatment. A nitric acid aqueous solution with a mass fraction of 14.2% is used in the acid tail gas treatment device. After all the arsenic slag in the quartz tube is converted into arsenic vapor and discharged from the quartz tube, nitrogen is continuously introduced, heating is stopped, the quartz tube is cooled to room temperature, and the nitrogen is then turned off.

[0040] (3) The quartz tube treated in step (2) is immersed in an acid cleaning solution for 30 minutes, wherein the acid cleaning solution is a mixed aqueous solution with a mass fraction of 2.5% hydrofluoric acid and a mass fraction of 12% nitric acid, to remove metal impurities on the inner wall of the quartz tube, and then rinsed with pure water and dried to obtain a decontaminated quartz tube.

[0041] (4) Methyltrimethoxysilane was added to an isopropanol solution and diluted to a mass concentration of 20%, and then pure water was added at room temperature and stirred for hydrolysis reaction for 2 hours. The amount of pure water added was 15% of the mass of methyltrimethoxysilane. The obtained hydrolyzate was sprayed onto the inner surface of a de-impurity quartz tube preheated to 80°C by an atomizing spray device, and the reaction was kept at room temperature for 15 minutes. After cooling to room temperature, the solution was rinsed with pure water, and then heated to 500°C under normal air conditions for 6 hours to obtain a quartz tube after dehydroxylation. The hydroxyl value of the de-hydroxylation quartz tube was 4.6ppm as detected by ICP-MS. The total impurity content (including arsenic, aluminum, iron, sodium, potassium, and lithium) was less than 10ppm. There were no pits or cracks on the inner wall of the quartz tube.

[0042] Example 3

[0043] A method for recovering arsenic-containing quartz tubes comprises the following steps:

[0044] Step (1) is the same as in Example 1.

[0045] (2) The quartz tube treated in step (1) is heated to 650°C in a horizontal heating furnace to convert the solid arsenic in the quartz tube into arsenic vapor. While heating, nitrogen is introduced through the air inlet pipe to discharge the arsenic vapor through the exhaust pipe to the cooling water recovery device to cool and solidify into arsenic particles. Ultrapure water at a temperature of 10°C is used in the cooling water recovery device. The remaining gas enters the acid tail gas treatment device for further absorption treatment. A nitric acid aqueous solution with a mass fraction of 20% is used in the acid tail gas treatment device. After all the arsenic slag in the quartz tube is converted into arsenic vapor and discharged from the quartz tube, nitrogen is continuously introduced, heating is stopped, the quartz tube is cooled to room temperature, and the nitrogen is then turned off.

[0046] (3) The quartz tube treated in step (2) is immersed in an acid cleaning solution for 10 minutes, wherein the acid cleaning solution is a mixed aqueous solution with a mass fraction of 7.4% hydrofluoric acid and a mass fraction of 20% nitric acid, to remove metal impurities on the inner wall of the quartz tube, and then rinsed with pure water and dried to obtain a decontaminated quartz tube.

[0047] (4) Methyltrimethoxysilane was added to an isopropanol solution and diluted to a mass concentration of 40%, and then pure water was added under normal temperature conditions and stirred for hydrolysis reaction for 0.5 hours. The amount of pure water added was 10% of the mass of methyltrimethoxysilane. The obtained hydrolyzate was sprayed onto the inner surface of a de-impurity quartz tube preheated to 100°C by an atomizing spray device, and the reaction was kept at a temperature for 5 minutes. After cooling to room temperature, the solution was rinsed with pure water, and then heated to 700°C under normal air conditions for 2 hours to obtain a quartz tube after dehydroxylation. The hydroxyl value of the de-hydroxylation quartz tube was 4.0 ppm as determined by ICP-MS. The total impurity content (including arsenic, aluminum, iron, sodium, potassium, and lithium) was less than 10 ppm. There were no pits or cracks on the inner wall of the quartz tube.

[0048] Comparative Example 1

[0049] A method for recovering arsenic-containing quartz tubes, compared with Example 1, the arsenic-containing quartz tubes are not heated to remove arsenic by a recovery device, but are directly soaked and cleaned by an acid wash solution, comprising the following steps:

[0050] The arsenic-containing quartz tube was immersed in an acid cleaning solution for 20 minutes. The acid cleaning solution was a mixed aqueous solution of 4.9% hydrofluoric acid and 14.2% nitric acid to remove metal impurities on the inner wall of the quartz tube. The tube was then rinsed with pure water and dried to obtain a decontaminated quartz tube.

[0051] The inner wall of the impurity-removed quartz tube in this comparative example after direct acid washing has obvious pits and cracks, and cannot be used for subsequent recycling. The reason is that under strong acid corrosion, arsenic reacts with quartz, causing pits and cracks to appear on the quartz tube.

[0052] Comparative Example 2

[0053] A method for recovering arsenic-containing quartz tubes. Compared with Example 1, the arsenic-containing quartz tubes are not immersed in acid solution for cleaning and impurity removal after being heated and treated by a recovery device for arsenic removal.

[0054] The total impurity content (including arsenic, aluminum, sodium, potassium, and lithium) of the quartz tube in this comparative example after heating to remove arsenic is 981 ppm, which cannot meet the purity requirements for single crystal growth.

[0055] Example 4

[0056] A method for recovering arsenic-containing quartz tubes, compared with Example 1, steps (1) to (3) are the same, and step (4) adopts the following dehydroxylation treatment:

[0057] The impurity-removed quartz tube was placed in a vacuum dehydroxylation furnace (vacuum degree within 0.1 Pa) for high-temperature dehydroxylation. The dehydroxylation temperature, dehydroxylation time and hydroxyl content of the quartz tube after treatment are shown in Table 1 below.

[0058] Table 1

[0059] Dehydroxylation temperature 800℃ 900℃ 900℃ 900℃ 1000℃ Dehydroxylation time 6h 3h 6h 9h 6h Hydroxyl content 21.4ppm 16.5ppm 9.6ppm 8.1ppm 7.8ppm

[0060] By comparing the results of Example 4 with Examples 1 to 3, it can be seen that the dehydroxylation treatment method combining chemical coupling with heat treatment in the present invention can significantly improve the dehydroxylation effect and reduce the temperature of heat treatment dehydroxylation.

[0061] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be equivalent replacement methods and are included in the protection scope of the present invention.

Claims

1. A method for recovering arsenic-containing quartz tubes, characterized in that: The steps include: (1) The tube mouth of the arsenic-containing quartz tube is sealed with a graphite plug with an air inlet hole and an air outlet hole, and then placed in a horizontal heating furnace, the air inlet hole of the graphite plug is connected to an air inlet pipe, the air outlet hole is connected to an exhaust pipe, and the exhaust pipe is connected to a cooling water recovery device and an acid tail gas treatment device in sequence; (2) heating the quartz tube treated in step (1) to 615-650° C. in a horizontal heating furnace to convert solid arsenic in the quartz tube into arsenic vapor, introducing an inert gas through an air inlet pipe while heating, so that the arsenic vapor is discharged through an exhaust pipe to a cooling water recovery device to cool and solidify into arsenic particles, and the remaining gas enters an acid tail gas treatment device; (3) placing the quartz tube treated in step (2) into an acid wash solution to remove impurities on the inner wall of the quartz tube, then rinsing with pure water, and drying to obtain a cleaned quartz tube; (4) The quartz tube treated in step (3) is subjected to a dehydroxylation treatment to obtain a recovered quartz tube.

2. The method for recovering arsenic-containing quartz tube according to claim 1, characterized in that: The inlet pipe in step (1) extends to the middle of the quartz tube to facilitate gas filling and exhaust of arsenic vapor from the exhaust pipe.

3. The method for recovering arsenic-containing quartz tube according to claim 1, characterized in that: The cooling water recovery device in step (1) uses ultrapure water with a temperature of 10 to 18°C.

4. The method for recovering arsenic-containing quartz tube according to claim 1, characterized in that: In step (1), the acidic tail gas treatment device uses a nitric acid aqueous solution with a mass fraction of 5% to 20%.

5. The method for recovering arsenic-containing quartz tube according to claim 1, characterized in that: The inert gas in step (2) is nitrogen or argon.

6. The method for recovering arsenic-containing quartz tube according to claim 1, characterized in that: The pickling solution in step (3) is a mixed aqueous solution of 1% to 10% hydrofluoric acid by mass and 10% to 35% nitric acid by mass; the cleaning refers to immersion cleaning for 5 to 30 minutes.

7. The method for recovering arsenic-containing quartz tube according to claim 1, characterized in that: The steps of dehydroxylation treatment in step (3) are as follows: The quartz tube is heated to 80-100°C, and then the hydrolyzed silane coupling agent atomized liquid is sprayed in the quartz tube, and the coupling reaction is kept at a temperature of 1-15 minutes. After cooling to room temperature, the tube is rinsed with pure water, and then heated to 500-700°C for heat treatment for 1-6 hours to obtain a quartz tube after dehydroxylation treatment.

8. The method for recovering arsenic-containing quartz tube according to claim 7, characterized in that: The silane coupling agent is selected from methyltrimethoxysilane or methyltriethoxysilane; the hydrolyzed silane coupling agent atomized liquid is prepared by the following method: The silane coupling agent is added to the isopropanol solution to dilute it to a mass concentration of 10% to 50%, and then pure water is added under normal temperature conditions to stir and hydrolyze for 0.5 to 2 hours. The obtained hydrolyzate is atomized by an atomizing spray device to obtain a hydrolyzed silane coupling agent atomized liquid.

9. The method for recovering arsenic-containing quartz tubes according to claim 8, characterized in that: The amount of pure water added is 5% to 40% of the mass of the silane coupling agent.

10. The method for recovering arsenic-containing quartz tube according to claim 1, characterized in that: The hydroxyl value of the quartz tube after the dehydroxylation treatment is lower than 10 ppm.

Images