Quartz tube for semiconductor single crystal growth and pretreatment method thereof

Abstract

The invention belongs to the technical field of semiconductor preparation devices and pretreatment, and discloses a quartz tube for semiconductor single crystal growth and a pretreatment method of the quartz tube. The pretreatment method comprises the following steps: cleaning a quartz tube in a pickling solution, washing with pure water, drying, heating to 80-100 DEG C, spraying silane coupling agent hydrolysate on the inner surface of the quartz tube, and carrying out heat preservation, standing and coupling reaction to obtain a quartz tube subjected to coupling treatment; and finally, heating the quartz tube subjected to coupling treatment to 500-700 DEG C for heat treatment to obtain the quartz tube subjected to dehydroxylation treatment. According to the pretreatment method, a specific pickling solution is adopted for impurity removal pretreatment, and a chemical coupling and heat treatment combined dehydroxylation treatment mode is adopted, so that the impurity removal effect and the dehydroxylation effect of the quartz tube can be remarkably improved, and the crystal yield of the quartz tube for semiconductor single crystal growth can be remarkably improved.

Description

Technical Field

[0001] The invention belongs to the technical field of semiconductor preparation equipment and pretreatment, and in particular relates to a quartz tube used for semiconductor single crystal growth and a pretreatment method thereof. Background Art

[0002] Quartz material has excellent properties such as high temperature resistance, small thermal expansion coefficient, excellent light transmittance, good electrical insulation, corrosion resistance, etc. It is one of the key raw materials in the semiconductor industry. Quartz material can be made into quartz tubes and other products for use in the semiconductor field. Semiconductor materials require quartz devices as carriers during crystal growth (such as gallium arsenide, indium phosphide, germanium, indium antimonide, photovoltaic industry crystal materials, etc.). Currently, commonly used quartz devices include quartz tubes and large quartz crucibles, which are contaminated to varying degrees during production and transportation. Therefore, quartz materials need to be cleaned and pre-treated.

[0003] In addition, with the development of semiconductor technology, the quality requirements for quartz devices are getting higher and higher, and the demand is also increasing. In the VGF method of growing semiconductor single crystals, the hydroxyl content of the quartz tube has an important influence on the growth process. Too high hydroxyl content will lead to uneven temperature during the growth process and affect the yield of crystal growth. At the same time, the unevenness or unevenness of the surface of the quartz tube is also considered to be one of the main reasons for the failure of large-diameter dislocation-free crystal growth. Therefore, there are high requirements for the surface morphology of the quartz tube.

[0004] At present, the main methods for removing hydroxyl groups from quartz tubes include heat treatment, chemical treatment and plasma treatment. Heat treatment is a common method for removing hydroxyl groups. It mainly uses the fact that quartz tubes will undergo a pyrolysis reaction at high temperatures, and hydroxyl groups will be decomposed to release water molecules and detach from the surface of the quartz tube. The advantage of this method is that it is simple and easy to operate, but it requires a higher temperature and a longer time to achieve a good dehydroxyl effect. In addition, long-term high-heat treatment may cause changes in the surface morphology and crystal structure of the quartz tube, affecting its performance. The commonly used chemical treatment method mainly uses chemical treatment agents such as acids and alkalis to react with hydroxyl groups on the surface of the quartz tube to remove them. It can be completed at a relatively low temperature, but conventional chemical treatment agents such as acids and alkalis can not only react with hydroxyl groups, but also corrode the quartz material to a certain extent, affect its surface morphology, and produce new hydroxyl groups at the corrosion site. The control of its treatment process is difficult; at the same time, the by-products of the reaction between conventional chemical treatment agents and hydroxyl groups also have a greater impact on the single crystal growth performance of the device, and its post-processing steps are relatively complicated. The plasma treatment method has the advantages of low processing temperature and no introduction of by-products, but it has high requirements for equipment and process control. Summary of the invention

[0005] In view of the shortcomings and deficiencies of the above prior art, the primary purpose of the present invention is to provide a pretreatment method for a quartz tube used for growing semiconductor single crystals.

[0006] Another object of the present invention is to provide a quartz tube pretreated by the above method.

[0007] The purpose of the present invention is achieved through the following technical solutions:

[0008] A method for pretreating a quartz tube for growing semiconductor single crystals comprises the following steps:

[0009] (1) The quartz tube is placed in an acid cleaning solution for cleaning, and then rinsed with pure water and dried to obtain a quartz tube after acid cleaning and impurity removal;

[0010] (2) heating the quartz tube treated in step (1) to 80-100° C., spraying the silane coupling agent hydrolyzate on the inner surface of the quartz tube, keeping the temperature and allowing the coupling reaction to proceed, cooling the tube to room temperature after the coupling reaction is completed, rinsing the tube with pure water, and drying the tube to obtain a coupling-treated quartz tube;

[0011] (3) The quartz tube treated in step (2) is heated to 500-700° C. for heat treatment to obtain a quartz tube after dehydroxylation treatment.

[0012] Furthermore, the pickling solution in step (1) is a mixed aqueous solution of 1% to 10% by mass of hydrofluoric acid and 10% to 35% by mass of nitric acid.

[0013] Furthermore, the cleaning in step (1) refers to immersion cleaning for 5 to 30 minutes.

[0014] Furthermore, the silane coupling agent in step (2) 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.

[0015] Furthermore, the method for preparing the silane coupling agent hydrolyzate in step (2) comprises the following steps:

[0016] 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 to obtain a silane coupling agent hydrolyzate.

[0017] Furthermore, in the preparation of the silane coupling agent hydrolyzate, the amount of pure water added is 5% to 40% of the mass of the silane coupling agent.

[0018] Furthermore, the time for the coupling reaction to be kept at room temperature in step (2) is 1 to 15 minutes.

[0019] Furthermore, the heat treatment in step (3) refers to heat treatment under normal air conditions or heat treatment under low-pressure oxygen conditions of 0.1 to 10 kPa.

[0020] Furthermore, the heat treatment time in step (3) is 1 to 6 hours.

[0021] A quartz tube for growing semiconductor single crystals is obtained by the above-mentioned pretreatment method.

[0022] Furthermore, the hydroxyl value of the quartz tube used for semiconductor single crystal growth is lower than 5 ppm.

[0023] The principle of the present invention is as follows: conventional heat treatment directly decomposes hydroxyl groups from the surface of the quartz tube by breaking Si-O bonds, and the Si-O bond energy is large, so a high temperature and a long time are required to achieve a good dehydroxylation effect, but 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 bond of the silane coupling agent to remove carbon and hydrogen elements through heat treatment. The bond energy of the Si-C bond breaking is significantly lower than that of the Si-O bond, so the coupling byproducts can be efficiently removed at a lower heat treatment temperature. At the same time, the Si-O-Si bond coupling product is heat-treated to generate SiO2 with the same composition as the quartz tube, without introducing additional impurities, thereby achieving an efficient dehydroxylation effect. 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 higher metal impurity content), a higher content of new hydroxyl groups will be produced due to the breaking of Si-O chemical bonds and the reaction with water. 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 flatness and uniformity of the quartz tube surface, and thus improving the single crystal growth effect.

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

[0025] (1) The pretreatment method of the present invention uses a mixed pickling solution of hydrofluoric acid and nitric acid of a certain concentration to pretreat the quartz tube for impurity removal, which has the advantages of good impurity removal effect and little corrosion effect on the quartz tube.

[0026] (2) The pretreatment method of the present invention 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 single crystal growth effect. DETAILED DESCRIPTION

[0027] The present invention is further described in detail below in conjunction with examples, but the embodiments of the present invention are not limited thereto.

[0028] Example 1

[0029] A method for pretreating a quartz tube for growing semiconductor single crystals comprises the following steps:

[0030] (1) A quartz tube (initial hydroxyl value content of 226 ppm, metal impurity content (including aluminum, iron, sodium, potassium, lithium) of 650 ppm) was immersed in a pickling solution with a mass fraction of 4.9% hydrofluoric acid and a mass fraction of 14.2% nitric acid for 20 minutes, then rinsed with pure water and dried to obtain a quartz tube after pickling and impurity removal. The hydroxyl value content detected by ICP-MS was 405 ppm. The metal impurity content was less than 10 ppm.

[0031] (2) The quartz tube treated in step (1) is heated to 90° C., and then a silane coupling agent hydrolyzate is sprayed on the inner surface of the quartz tube (methyltrimethoxysilane is added to an isopropanol solution to dilute it to a mass concentration of 35%, and then pure water is added at room temperature to stir and hydrolyze for 1 hour, and the amount of pure water added is 12% of the mass of methyltrimethoxysilane). The coupling reaction is allowed to stand for 10 minutes at the temperature. After the coupling reaction is completed, the tube is cooled to room temperature, rinsed with pure water, and dried to obtain a coupling-treated quartz tube.

[0032] (3) The quartz tube treated in step (2) is heated to 600° C. under normal air conditions for 3 hours to obtain a quartz tube after dehydroxylation treatment.

[0033] The quartz tube obtained in this example after dehydroxylation treatment has a hydroxyl value of 3.2 ppm as determined by ICP-MS, and a metal impurity content of <10 ppm.

[0034] It can be seen from the above results that the pickling pretreatment of the present invention can significantly reduce the metal impurity content, but will lead to an increase in the hydroxyl content; through further dehydroxylation treatment, the hydroxyl value content can be reduced to <5ppm, and the metal impurity content can be reduced to <10ppm.

[0035] Example 2

[0036] A method for pretreating a quartz tube for growing semiconductor single crystals comprises the following steps:

[0037] (1) A quartz tube (initial hydroxyl value content of 235 ppm, metal impurity content (including aluminum, iron, sodium, potassium, lithium) of 625 ppm) was immersed in an acid cleaning solution with a mass fraction of 2.5% hydrofluoric acid and a mass fraction of 12% nitric acid for 30 minutes, then rinsed with pure water and dried to obtain a quartz tube after acid cleaning and impurity removal. ICP-MS detected that the hydroxyl value content was 317 ppm. The metal impurity content was less than 10 ppm.

[0038] (2) The quartz tube treated in step (1) is heated to 80° C., and then a silane coupling agent hydrolyzate is sprayed on the inner surface of the quartz tube (methyltrimethoxysilane is added to an isopropanol solution to dilute it to a mass concentration of 20%, and then pure water is added at room temperature to stir and hydrolyze for 2 hours, and the amount of pure water added is 15% of the mass of methyltrimethoxysilane). The coupling reaction is allowed to stand for 15 minutes at the temperature. After the coupling reaction is completed, the tube is cooled to room temperature, rinsed with pure water, and dried to obtain a coupling-treated quartz tube.

[0039] (3) The quartz tube treated in step (2) is heated to 500° C. under 1 kPa low-pressure oxygen conditions for 6 hours to obtain a quartz tube after dehydroxylation treatment.

[0040] The quartz tube obtained in this example after dehydroxylation treatment has a hydroxyl value of 3.9 ppm as determined by ICP-MS, and a metal impurity content of <10 ppm.

[0041] It can be seen from the above results that the pickling pretreatment of the present invention can significantly reduce the metal impurity content, but will lead to an increase in the hydroxyl content; through further dehydroxylation treatment, the hydroxyl value content can be reduced to <5ppm, and the metal impurity content can be reduced to <10ppm.

[0042] Example 3

[0043] A method for pretreating a quartz tube for growing semiconductor single crystals comprises the following steps:

[0044] (1) A quartz tube (initial hydroxyl value content of 254 ppm, metal impurity content (including aluminum, iron, sodium, potassium, lithium) of 612 ppm) was immersed in a pickling solution with a mass fraction of 7.4% hydrofluoric acid and a mass fraction of 20% nitric acid for 10 minutes, then rinsed with pure water and dried to obtain a quartz tube after pickling and impurity removal. ICP-MS detected that the hydroxyl value content was 580 ppm. The metal impurity content was less than 10 ppm.

[0045] (2) The quartz tube treated in step (1) is heated to 100° C., and then a silane coupling agent hydrolyzate is sprayed on the inner surface of the quartz tube (methyltrimethoxysilane is added to an isopropanol solution to dilute it to a mass concentration of 40%, and then pure water is added at room temperature to stir and hydrolyze for 0.5 h, and the amount of pure water added is 10% of the mass of methyltrimethoxysilane). The coupling reaction is allowed to stand for 5 min at the temperature, and after the coupling reaction is completed, the tube is cooled to room temperature, rinsed with pure water, and dried to obtain a coupling-treated quartz tube.

[0046] (3) The quartz tube treated in step (2) is heated to 700° C. under normal air conditions for 2 hours to obtain a quartz tube after dehydroxylation treatment.

[0047] The quartz tube obtained in this example after dehydroxylation treatment has a hydroxyl value of 3.8 ppm as determined by ICP-MS, and a metal impurity content of <10 ppm.

[0048] It can be seen from the above results that the pickling pretreatment of the present invention can significantly reduce the metal impurity content, but will lead to an increase in the hydroxyl content; through further dehydroxylation treatment, the hydroxyl value content can be reduced to <5ppm, and the metal impurity content can be reduced to <10ppm.

[0049] Comparative Examples 1 to 3

[0050] A pretreatment method for a quartz tube for growing a semiconductor single crystal, wherein the quartz tube after pickling and impurity removal under the same conditions as in Example 1 (the hydroxyl value content of different treatment batches is in the range of 350 to 420 ppm, and the metal impurity content is less than 10 ppm) is directly placed in a vacuum dehydroxylation furnace (with a vacuum degree of less than 0.1 Pa) according to the dehydroxylation temperature and dehydroxylation time in Table 1 for high-temperature dehydroxylation treatment.

[0051] The corresponding hydroxyl content results of the quartz tube after dehydroxylation are shown in Table 1 below.

[0052] The quartz tubes obtained by the treatment methods of Examples 1 to 3 and Comparative Examples 1 to 3 were used for the vertical gradient condensation method of single crystal growth of gallium arsenide polycrystalline material (the crystal growth program control temperature was 1238°C and the single crystal size was 6 inches), and the corresponding crystal yield was tested. The results are shown in Table 1.

[0053] Table 1

[0054] Test Case Dehydroxylation temperature Dehydroxylation time Hydroxyl content Crystal yield* Example 1 600℃ 3h 3.2ppm 87％ Example 2 500℃ 6h 3.9ppm 83％ Example 3 700℃ 2h 3.8ppm 83％ Comparative Example 1 950℃ 6h 8.4ppm 57％ Comparative Example 2 1050℃ 6h 6.2ppm 60％ Comparative Example 3 1150℃ 6h 3.5ppm 63％

[0055] *Statistics based on 30 batches of results.

[0056] It can be seen from the results in Table 1 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, and can significantly improve the yield of semiconductor single crystal growth.

[0057] 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 pretreating a quartz tube for growing semiconductor single crystals, characterized in that: The steps include: (1) The quartz tube is placed in an acid cleaning solution for cleaning, and then rinsed with pure water and dried to obtain a quartz tube after acid cleaning and impurity removal; (2) heating the quartz tube treated in step (1) to 80-100° C., spraying the silane coupling agent hydrolyzate on the inner surface of the quartz tube, keeping the temperature and allowing the coupling reaction to proceed, cooling the tube to room temperature after the coupling reaction is completed, rinsing the tube with pure water, and drying the tube to obtain a coupled quartz tube; (3) The quartz tube treated in step (2) is heated to 500-700° C. for heat treatment to obtain a quartz tube treated with dehydroxylation.

2. A method for pretreating a quartz tube for growing a semiconductor single crystal according to claim 1, characterized in that: The pickling solution in step (1) 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.

3. The method for pretreating a quartz tube for growing a semiconductor single crystal according to claim 1, characterized in that: The silane coupling agent in step (2) is selected from methyltrimethoxysilane or methyltriethoxysilane.

4. The method for pretreating a quartz tube for growing a semiconductor single crystal according to claim 1, characterized in that: The method for preparing the silane coupling agent hydrolyzate in step (2) comprises the following steps: 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 at room temperature to stir and hydrolyze for 0.5 to 2 hours to obtain a silane coupling agent hydrolyzate.

5. A method for pretreating a quartz tube for growing semiconductor single crystals according to claim 4, characterized in that: In the preparation of the silane coupling agent hydrolyzate, the amount of pure water added is 5% to 40% of the mass of the silane coupling agent.

6. The method for pretreating a quartz tube for growing a semiconductor single crystal according to claim 1, characterized in that: The time for the coupling reaction to be kept at room temperature in step (2) is 1 to 15 minutes.

7. The method for pretreating a quartz tube for growing a semiconductor single crystal according to claim 1, characterized in that: The heat treatment in step (3) refers to heat treatment under normal air conditions or heat treatment under low-pressure oxygen conditions of 0.1 to 10 kPa.

8. A method for pretreating a quartz tube for growing semiconductor single crystals according to claim 7, characterized in that: The heat treatment time in step (3) is 1 to 6 hours.

9. A quartz tube for growing semiconductor single crystals, characterized in that: The product is obtained by the pretreatment method according to any one of claims 1 to 8.

10. The quartz tube for growing semiconductor single crystals according to claim 9, characterized in that: The quartz tube has a hydroxyl value of less than 5 ppm.