Synthetic quartz crucible, preparation equipment thereof and method for inhibiting brown rings on inner surface of synthetic quartz crucible

Abstract

The invention discloses a synthetic quartz crucible, preparation equipment thereof and a method for inhibiting brown rings on the inner surface of the synthetic quartz crucible, and belongs to the technical field of quartz crucibles. The equipment comprises a melting chamber, an air inlet system, an electrode, a helium inlet system, an exhaust system, a mold vacuum system and a mold, the mold, the mold vacuum system and the electrode are all positioned in the melting chamber; the melting chamber is communicated with the air inlet system, the helium inlet system and the exhaust system; the mold vacuum system is arranged on the outer side of the mold to vacuumize the mold; the electrode is arranged above the mold. The gas environment in the melting chamber is controlled through the air inlet system, the helium inlet system and the exhaust system, the vacuum degree in the mold is adjusted through the mold vacuum system, pollution and impurity enrichment on the inner surface of the crucible can be effectively reduced, microbubbles on the inner surface of the crucible can be reduced, and then structural defects caused by bubble breakage are reduced. By adopting the equipment to prepare the synthetic quartz crucible, the number of brown rings on the inner surface of the crucible can be effectively inhibited.

Description

Technical Field

[0001] This invention relates to the field of quartz crucible technology, and more specifically, to a synthetic quartz crucible and its preparation equipment, as well as a method for suppressing brown rings on its inner surface. Background Technology

[0002] Brown rings on quartz crucibles are annular brown or tan marks that appear on the inner wall after high-temperature use. They are typically compound layers formed by the reaction of quartz with the molten silicon or by contamination from impurities. For example, at high temperatures, structural defects on the inner wall of the quartz crucible easily react with the melt inside, generating low-valence silicon oxides. These low-valence silicon oxides adhere to the inner wall of the crucible and form brown rings upon cooling. Furthermore, impurity-rich areas in the quartz crucible, especially alkali metals (such as potassium, sodium, and lithium) or alkaline earth metals (such as calcium and magnesium), can also react with quartz at high temperatures to form colored metal oxides, which may ultimately manifest as brown rings. The formation and peeling off of brown rings disrupt the integrity of the crystal structure, leading to dislocations in single-crystal silicon, significantly reducing yield, and potentially introducing defects such as pinholes.

[0003] In view of this, the present invention is proposed. Summary of the Invention

[0004] The purpose of this invention is to provide a synthetic quartz crucible and its preparation equipment, as well as a method for suppressing brown rings on its inner surface, in order to solve or improve the above-mentioned technical problems.

[0005] This invention can be implemented as follows: In a first aspect, the present invention provides a synthetic quartz crucible preparation apparatus, comprising a melting chamber, an air inlet system, electrodes, a helium gas inlet system, an exhaust system, a mold vacuum system, and a mold; The mold, mold vacuum system, and electrodes are all located in the melting chamber; the melting chamber is connected to the air inlet system, helium inlet system, and exhaust system; the mold vacuum system is located on the outside of the mold, and the mold has an airflow channel connected to the mold vacuum system so that the mold vacuum system can evacuate the mold; the electrodes are located above the mold.

[0006] In an optional implementation, the air intake system includes a pre-filter, a medium-efficiency filter, and a high-efficiency filter arranged sequentially from the outside to the inside, according to the airflow direction.

[0007] In an optional embodiment, at least one of a temperature control device and a humidity control device is provided between the pre-filter and the medium-efficiency filter.

[0008] Secondly, the present invention provides a method for suppressing brown rings on the inner surface of a synthetic quartz crucible, which is prepared using the preparation equipment of any of the foregoing embodiments; The preparation process includes: laying quartz sand in a mold, and then controlling the conditions of the air intake system, helium intake system, and exhaust system in the following five stages: Phase 1: Air is introduced into the mold through the air intake system at a speed of 1 mm / s to 1.5 mm / s, while helium is introduced into the mold through the helium intake system at a gauge pressure of -0.08 MPa to -0.12 MPa. The gas inside the mold is discharged out through the exhaust system at a speed of 2 mm / s to 3 mm / s. The mold vacuum system is used to evacuate the mold to maintain a vacuum level of -0.02 MPa to -0.03 MPa. The second stage involves introducing air into the mold through the air intake system at a speed of 6 mm / s to 7 mm / s, while simultaneously introducing helium into the mold through the helium intake system at a gauge pressure of -0.1 MPa to -0.15 MPa. The exhaust system then expels the gas from the mold through the exhaust system at a speed of 5 mm / s to 6 mm / s, with the air intake speed exceeding the exhaust speed. The mold is then evacuated using a mold vacuum system to maintain a vacuum level of -0.095 MPa to -0.099 MPa. The third stage: Air is introduced into the mold through the air intake system at a speed of 6 mm / s to 7 mm / s; the helium intake system is closed; the gas in the mold is discharged out through the exhaust system at a speed of 5 mm / s to 6 mm / s; and the mold vacuum system is used to evacuate the mold to maintain the vacuum level in the mold at -0.030 MPa to -0.040 MPa. Fourth stage: Introduce air into the mold through the air intake system at a speed of 3mm / s~4mm / s; shut off the helium intake system; exhaust the gas from the mold through the exhaust system at a speed of 4mm / s~5mm / s, with the exhaust speed being greater than the intake speed; shut off the mold vacuum system; Fifth stage: Shut down the air intake system, helium intake system and mold vacuum system; exhaust the gas in the mold to the outside through the exhaust system at a speed of 2mm / s~3mm / s.

[0009] In an optional implementation, in the first stage, the volume of helium in the melting chamber is 5% to 15% of the total volume of helium and air.

[0010] In an optional implementation, during the second stage, electric arc melting is performed through electrodes to form a transparent layer of quartz sand in the area affected by the electric arc. The conditions for arc melting include: a current of 2000A~2300A, an arc duration of 6min~8min, an electrode spacing of 20mm~25mm, and a vertical distance of 150mm~200mm between the arc-starting end of the electrode and the upper port of the rotating mold.

[0011] In an optional implementation, during the third stage, an electric arc is performed through electrodes to form a bubble layer in the quartz sand within the arc-affected area. The conditions for arc melting include: a current of 2700A~3000A, an arc duration of 12min~15min, an electrode spacing of 30mm~35mm, and a vertical distance of 100mm~150mm between the arc-starting end of the electrode and the upper port of the rotating mold.

[0012] In an optional embodiment, the mold rotates at a speed of 67 rpm to 69 rpm during the preparation process.

[0013] In an optional embodiment, the quartz sand used to prepare the synthetic quartz crucible comprises 8% to 10% synthetic quartz sand by mass percentage, with the remainder being high-purity natural quartz sand. Among them, the particle size of synthetic quartz sand is 150μm~200μm and the purity is not less than 99.99999%; the particle size of high-purity natural quartz sand is 200μm~250μm and the purity is not less than 99.9999%.

[0014] Thirdly, the present invention provides a synthetic quartz crucible prepared by any of the methods described in the foregoing embodiments.

[0015] The beneficial effects of this invention include: The synthetic quartz crucible preparation equipment provided by this invention has a simple structure. It controls the gas environment within the melting chamber through an air inlet system, a helium inlet system, and an exhaust system, and adjusts the vacuum level within the mold through a mold vacuum system. This effectively reduces contamination on the inner surface of the crucible and decreases impurity accumulation on the inner wall. Furthermore, it reduces microbubbles on the inner surface of the crucible, thereby minimizing structural defects caused by bubble rupture. Using this equipment to prepare the synthetic quartz crucible effectively suppresses the number of brown rings on the inner surface of the crucible. Attached Figure Description

[0016] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 This is a schematic diagram of the structure of the synthetic quartz crucible preparation equipment provided by the present invention; Figure 2 for Figure 1 A physical image of the central air intake system; Figure 3This is a graph showing the number of brown rings in the straight-wall region after using the synthetic quartz crucible prepared in Example 2. Figure 4 This is a graph showing the number of brown rings in region R after the synthetic quartz crucible prepared in Example 2 has been used. Figure 5 This is a diagram showing the number of brown rings in the straight-wall region of a conventional quartz crucible after use in the prior art. Figure 6 This is a graph showing the number of brown rings in region R after using a conventional quartz crucible in the prior art.

[0018] Icons: 1-Air intake system; 2-Electrode; 3-Helium gas intake system; 4-Exhaust system; 5-Mold vacuum system; 6-Mold; 7-Transparent layer; 8-Bubble layer. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0020] The synthetic quartz crucible provided by this invention is a semiconductor-grade synthetic quartz crucible. The following is a detailed description of the synthetic quartz crucible, its preparation equipment, and the method for suppressing the brown rings on its inner surface.

[0021] This invention provides a device for preparing synthetic quartz crucibles, such as... Figure 1 and Figure 2 As shown ( Figure 1 (The middle arrow indicates the direction of gas flow). The preparation equipment includes a melting chamber, an air inlet system 1, an electrode 2, a helium gas inlet system 3, an exhaust system 4, a mold vacuum system 5, and a mold 6.

[0022] The mold 6, the mold vacuum system 5, and the electrode 2 are all located in the melting chamber; the melting chamber is connected to the air inlet system 1, the helium inlet system 3, and the exhaust system 4; the mold vacuum system 5 is located on the outside of the mold 6, and the mold 6 has an airflow channel connected to the mold vacuum system 5 so that the mold vacuum system 5 can evacuate the mold 6; the electrode 2 is located above the mold 6.

[0023] The aforementioned air intake system 1, helium intake system 3, and exhaust system 4 can all be connected to the melting chamber via pipelines, and valves can be installed on each pipeline.

[0024] In some optional embodiments, the air intake system 1 includes a pre-filter, a medium-efficiency filter, and a high-efficiency filter arranged sequentially from the outside to the inside, according to the airflow direction.

[0025] Outside the melting chamber, the air passes through a pre-filter to intercept larger particles (e.g., particles with a diameter ≥5μm), such as pollen, dust, and insects; a medium-efficiency filter further removes smaller particles (e.g., particles with a diameter of 1.0μm~10μm); and then a high-efficiency filter removes even smaller particles (e.g., particles with a diameter ≥0.3μm).

[0026] Preferably, at least one of a temperature control device and a humidity control device may be provided between the pre-filter and the medium-efficiency filter. The temperature control device may include, for example, a cooling device (such as a cooling plate or cooling pipe) and / or a heating device (such as a heating plate or heating pipe). The cooling device can be used in summer or under high-temperature conditions, while the heating device can be used in winter or under low-temperature conditions. The humidity control device may include, for example, a humidifier and / or a dehumidifier. The specific location of the temperature control device and the humidity control device is not limited, as long as they can achieve the functions of temperature and humidity control.

[0027] The temperature and humidity of the air entering the melting chamber can be regulated by the above-mentioned temperature and humidity control devices. For example, the temperature can be adjusted to 25°C to 28°C and the humidity can be adjusted to 45% to 65%.

[0028] If the temperature of the air entering the melting chamber is too cold or too hot, it will affect the stability of the bubbles. Poor bubble stability will make them more prone to breakage, which will easily introduce impurities. If the humidity of the air entering the melting chamber is too high, it will introduce more hydroxyl groups, lower the softening point of the crucible, and increase the formation of brown rings.

[0029] Therefore, the air intake system 1 described above in this invention can effectively control the cleanliness, temperature, and humidity of the air entering the melting chamber. On the one hand, it can prevent the crucible from directly contacting the atmospheric air environment during the melting process, which would introduce impurities in the air to the inner surface of the crucible and increase the occurrence rate of brown rings. On the other hand, it can control clean air to be introduced into the melting chamber with appropriate humidity and temperature.

[0030] Furthermore, the helium gas inlet system 3 in this invention is mainly used to introduce helium gas into the melting chamber. Helium gas has high diffusivity in quartz, which is beneficial for removing bubbles (such as hydrogen and oxygen) from the molten quartz and improving the purity and transparency of the crucible. Therefore, the introduction of helium gas can reduce bubbles and improve the melting environment.

[0031] In this invention, the exhaust system 4 is mainly used to remove harmful gases and particulate matter generated during the electric arc melting process. Correspondingly, the air intake system 1, the helium intake system 3, and the exhaust system 4 cooperate with each other to maintain stable airflow and pressure.

[0032] In this invention, the mold vacuum system 5 is mainly used to draw helium and air from the melting chamber into the gaps of the quartz sand and control the vacuum level in the mold 6 so as to form a transparent layer 7 and a bubble layer 8 under different arc melting conditions.

[0033] As described above, this invention controls the gas environment in the melting chamber through the air intake system 1, the helium intake system 3, and the exhaust system 4, and adjusts the vacuum level in the mold 6 through the mold vacuum system 5. This not only effectively reduces contamination and impurity accumulation on the inner surface of the crucible, but also reduces microbubbles on the inner surface of the crucible, thereby reducing structural defects caused by bubble rupture.

[0034] Accordingly, the present invention also provides a method for suppressing brown rings on the inner surface of a synthetic quartz crucible, which is prepared using the above-mentioned preparation equipment.

[0035] The preparation process includes: laying quartz sand in mold 6 and then controlling the conditions of air intake system 1, helium intake system 3 and exhaust system 4 in the following five stages.

[0036] In the above preparation process, the rotation speed of mold 6 can be 67 rpm to 69 rpm, such as 67 rpm, 68 rpm or 69 rpm, or other values ​​within the range of 67 rpm to 69 rpm.

[0037] The quartz sand used to prepare the synthetic quartz crucible comprises 8% to 10% (e.g., 8%, 8.5%, 9%, 9.5%, or 10%) of synthetic quartz sand by mass percentage, with the remainder being high-purity natural quartz sand.

[0038] The synthetic quartz sand has a particle size of 150μm~200μm (e.g., 150μm, 160μm, 170μm, 180μm, 190μm or 200μm) and a purity of not less than 99.99999%; the high-purity natural quartz sand has a particle size of 200μm~250μm (e.g., 200μm, 210μm, 220μm, 230μm, 240μm or 250μm) and a purity of not less than 99.9999%.

[0039] When laying quartz sand, follow the order from the outside to the inside, first laying high-purity natural quartz sand, then laying synthetic quartz sand.

[0040] In the first stage of this invention, air is introduced into the mold 6 through the air intake system 1 at a speed of 1 mm / s to 1.5 mm / s, while helium is introduced into the mold 6 through the helium intake system 3 at a gauge pressure of -0.08 MPa to -0.12 MPa. The gas inside the mold 6 is discharged outward through the exhaust system 4 at a speed of 2 mm / s to 3 mm / s. The mold vacuum system 5 is used to evacuate the mold 6 to maintain the vacuum degree inside the mold 6 at -0.02 MPa to -0.03 MPa.

[0041] The air inlet velocity can be 1 mm / s, 1.1 mm / s, 1.2 mm / s, 1.3 mm / s, 1.4 mm / s, or 1.5 mm / s, or other values ​​within the range of 1 mm / s to 1.5 mm / s.

[0042] When helium is introduced, the gauge pressure can be -0.08MPa, -0.09MPa, -0.1MPa, -0.11MPa or -0.12MPa, or other values ​​within the range of -0.08MPa to -0.12MPa.

[0043] The gas discharge velocity can be 2 mm / s, 2.5 mm / s, or 3 mm / s, or other values ​​within the range of 2 mm / s to 3 mm / s.

[0044] The vacuum level inside mold 6 can be -0.02MPa, -0.025MPa, or -0.03MPa, or other values ​​within the range of -0.02MPa to -0.03MPa.

[0045] In the first stage mentioned above, the volume of helium in the melting chamber can be 5% to 15% of the total volume of helium and air, such as 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14% or 15%, or other values ​​within the range of 5% to 15%.

[0046] In the first stage described above, filtered air is introduced through the air intake system 1, helium is introduced through the helium intake system 3, and the original air in the melting chamber is initially exhausted through the exhaust system 4. By continuously introducing and exhausting air, the entire melting chamber is filled with helium and filtered air, reducing contamination on the inner surface of the crucible. Combined with the vacuuming of the mold vacuum system 5, the gaps between the quartz sand are also filled with helium and filtered air, which helps to remove or reduce air bubbles in the molten quartz and improve the purity and transparency of the crucible.

[0047] In the second stage of the present invention, air is introduced into the mold 6 through the air intake system 1 at a speed of 6 mm / s to 7 mm / s, and helium is introduced into the mold 6 through the helium intake system 3 at a gauge pressure of -0.1 MPa to -0.15 MPa. The gas inside the mold 6 is discharged outward through the exhaust system 4 at a speed of 5 mm / s to 6 mm / s. The mold vacuum system 5 is used to evacuate the mold 6 to maintain the vacuum degree inside the mold 6 at -0.095 MPa to -0.099 MPa.

[0048] The air inlet velocity can be 6 mm / s, 6.5 mm / s, or 7 mm / s, or other values ​​within the range of 6 mm / s to 7 mm / s.

[0049] When helium is introduced, the gauge pressure can be -0.1MPa, -0.11MPa, -0.12MPa, -0.13MPa, -0.14MPa, or -0.15MPa, or other values ​​within the range of -0.1MPa to -0.15MPa.

[0050] The gas discharge velocity can be 5 mm / s, 5.5 mm / s, or 6 mm / s, or other values ​​within the range of 5 mm / s to 6 mm / s.

[0051] The vacuum degree inside mold 6 can be -0.095MPa, -0.096MPa, -0.097MPa, -0.098MPa or -0.099MPa, or other values ​​within the range of -0.095MPa to -0.099MPa.

[0052] In the second stage described above, electric arc melting is performed using electrode 2 to form a transparent layer 7 in the quartz sand within the arc-affected area. The electric arc melting conditions may include: a current of 2000A~2300A (e.g., 2000A, 2100A, 2200A, or 2300A), an arc duration of 6min~8min (e.g., 6min, 7min, or 8min), an electrode spacing of 20mm~25mm (e.g., 20mm, 22mm, or 25mm), and a vertical distance between the arc-initiating end of electrode 2 and the upper port of the rotating mold 6 of 150mm~200mm (e.g., 150mm, 180mm, or 200mm).

[0053] The second stage described above pertains to the preparation of the transparent layer 7. At the start of arc melting, the graphite electrode 2 introduces numerous harmful impurities, gases, and white spots (white spots are an amorphous product resulting from vaporization and cooling). This invention effectively maintains the environment within the melting chamber by increasing both the inlet and outlet air speeds, ensuring that the inlet air speed exceeds the outlet air speed. This maintains a positive pressure environment during melting. Simultaneously, the vacuum pressure is controlled to be close to the ultimate pressure, exceeding the melting rate, effectively removing bubbles generated during the melting process and obtaining the transparent layer 7.

[0054] In the third stage of the present invention, air is introduced into the mold 6 through the air intake system 1 at a speed of 6 mm / s to 7 mm / s; the helium intake system 3 is closed; the gas in the mold 6 is discharged outward through the exhaust system 4 at a speed of 5 mm / s to 6 mm / s; and the mold vacuum system 5 is used to evacuate the mold 6 to maintain the vacuum degree in the mold 6 at -0.030 MPa to -0.040 MPa.

[0055] The air inlet velocity can be 6 mm / s, 6.5 mm / s, or 7 mm / s, or other values ​​within the range of 6 mm / s to 7 mm / s.

[0056] The gas discharge velocity can be 5 mm / s, 5.5 mm / s, or 6 mm / s, or other values ​​within the range of 5 mm / s to 6 mm / s.

[0057] The vacuum level inside mold 6 can be -0.030MPa, -0.035MPa, or -0.040MPa, or other values ​​within the range of -0.030MPa to -0.040MPa.

[0058] In the third stage described above, electric arc melting is performed through electrode 2 to form a bubble layer 8 in the quartz sand within the arc-acting area. The electric arc melting conditions may include: a current of 2700A~3000A (e.g., 2700A, 2800A, 2900A, or 3000A), an arc duration of 12min~15min (e.g., 12min, 13min, 14min, or 15min), an electrode spacing of 30mm~35mm (e.g., 20mm, 32mm, or 35mm), and a vertical distance between the arc-initiating end of electrode 2 and the upper port of the rotating mold 6 of 100mm~150mm (e.g., 100mm, 130mm, or 150mm).

[0059] The third stage described above pertains to the preparation of bubble layer 8. This involves reducing the vacuum pressure compared to the second stage, ensuring the vacuum pressure is lower than the melting rate, thereby forming a dense bubble layer 8. Due to the high cost of helium and the fact that there are virtually no gaps after the quartz sand melts, the permeability of helium in the molten quartz is very low. Therefore, helium is not introduced in the third stage or subsequent stages.

[0060] In the fourth stage of the present invention, air is introduced into the mold 6 through the air intake system 1 at a speed of 3 mm / s to 4 mm / s; the helium intake system 3 is closed; the gas in the mold 6 is discharged outward through the exhaust system 4 at a speed of 4 mm / s to 5 mm / s; and the mold vacuum system 5 is closed.

[0061] The air inlet velocity can be 3 mm / s, 3.5 mm / s, or 4 mm / s, or other values ​​within the range of 3 mm / s to 4 mm / s.

[0062] The gas discharge velocity can be 4 mm / s, 4.5 mm / s, or 5 mm / s, or other values ​​within the range of 4 mm / s to 5 mm / s.

[0063] The fourth stage described above is the cooling stage after melting is completed. At this time, the air inlet speed is set to be less than the exhaust speed to prevent some of the residual quartz particles floating in the melting chamber from falling back into the crucible, causing the quartz particles to adhere to the inner surface of the crucible and create structural defects. Among them, the "partially floating residual quartz particles" are mainly some unmelted surface synthetic quartz sand that was impacted by the arc light at the beginning of melting and flew inside the cavity of the melting chamber. They were not extracted and removed in time by the exhaust system 4, and therefore remained in the cavity environment.

[0064] In the fifth stage of the present invention, the air intake system 1, the helium intake system 3 and the mold vacuum system 5 are shut off; the gas inside the mold 6 is discharged outward through the exhaust system 4 at a speed of 2mm / s to 3mm / s (such as 2mm / s, 2.5mm / s or 3mm / s, etc.).

[0065] The fifth stage mentioned above is the unloading stage. After unloading, a certain exhaust speed is maintained to remove as much residual harmful gas as possible from the environment.

[0066] Continuing from the above, in the preparation process proposed in this invention, the first stage is mainly used to control the environmental conditions inside the melting chamber, the second stage is used to prepare the transparent layer 7, the third stage is used to prepare the bubble layer 8, the fourth stage is mainly used as the cooling stage, and the fifth stage is mainly used as the unloading stage. By controlling the conditions such as gas entry, gas exit, and vacuum degree in each stage, the gas and impurities generated by the graphite electrode 2 during the melting process can be effectively discharged in a timely manner, reducing the impurity content or impurity enrichment on the inner wall of the crucible, reducing microbubbles on the inner surface of the crucible, thereby reducing structural defects caused by bubble rupture, and reducing the number of brown rings generated after the crucible is used at high temperatures. In addition, by controlling the above conditions, it is also possible to avoid quartz particles falling off and adhering to the inner wall of the crucible, causing defects on the inner wall surface of the crucible (such as surface scratches or micro cracks), which would lead to an increase in the number of brown rings after high-temperature use. It should be noted that the melting chamber structure and other melting conditions not described in detail in this invention can be found in the relevant prior art, and will not be elaborated further here.

[0067] In addition, the present invention also provides a synthetic quartz crucible prepared by the above method.

[0068] In some alternative embodiments, the thickness of the transparent layer 7 in the synthetic quartz crucible can be 2 mm to 4 mm, and the thickness of the bubble layer 8 can be 12 mm to 14 mm.

[0069] In some alternative embodiments, the outer diameter of the synthetic quartz crucible can be 809 mm to 813 mm, and the height can be 500 mm to 530 mm.

[0070] In some alternative embodiments, after crystal pulling, the number of brown rings in the straight-walled region of the synthetic quartz crucible does not exceed 5 per cm. 2 The number of brown rings in region R does not exceed 2 per cm. 2 .

[0071] The number of brown rings in this synthetic quartz crucible is effectively suppressed compared to ordinary quartz crucibles, which helps to improve the quality and yield of monocrystalline silicon.

[0072] The features and performance of the present invention will be further described in detail below with reference to embodiments.

[0073] Example 1 This embodiment provides a synthetic quartz crucible preparation device, which includes a melting chamber, an air inlet system 1, an electrode 2, a helium gas inlet system 3, an exhaust system 4, a mold vacuum system 5, and a mold 6.

[0074] The mold 6, mold vacuum system 5, and electrode 2 are all located within the melting chamber. The melting chamber is connected to the air inlet system 1, helium inlet system 3, and exhaust system 4. The mold vacuum system 5 is located outside the mold 6, and the mold 6 has an airflow channel connected to the mold vacuum system 5 to allow the mold vacuum system 5 to evacuate the mold 6. The electrode 2 is located above the mold 6. The air inlet system 1, helium inlet system 3, and exhaust system 4 are all connected to the melting chamber via pipes, and each pipe is equipped with a valve.

[0075] The air intake system 1, arranged sequentially from the outside to the inside, includes a pre-filter, a medium-efficiency filter, and a high-efficiency filter, according to the airflow direction. The pre-filter intercepts larger particles (≥5μm in diameter); the medium-efficiency filter removes smaller particles (e.g., 1.0μm~10μm in diameter); and the high-efficiency filter removes even smaller particles (≥0.3μm in diameter). A temperature control device and a humidity control device are also provided between the pre-filter and the medium-efficiency filter. The temperature control device is a cooling device (e.g., a cooling plate or cooling pipe) or a heating device (e.g., a heating plate or heating pipe). The humidity control device is a humidifier or a dehumidifier. The temperature of the air entering the melting chamber is controlled at 25℃~28℃ by the temperature control device, and the humidity of the air entering the melting chamber is controlled at 45%~65% by the humidity control device.

[0076] Example 2 This embodiment provides a synthetic quartz crucible with an outer diameter of 809 mm and a height of 500 mm, which is prepared using the preparation equipment provided in Example 1. The thickness of the transparent layer 7 in this synthetic quartz crucible is 2 mm, and the thickness of the bubble layer 8 is 14 mm.

[0077] The preparation process of the synthetic quartz crucible includes: first, laying high-purity natural quartz sand, then laying synthetic quartz sand mold 6 in the order from the outside to the inside, and then controlling the conditions of the air inlet system 1, helium air inlet system 3, and exhaust system 4 in the following five stages.

[0078] The quartz sand used to prepare the synthetic quartz crucible comprises, by mass percentage, 8% synthetic quartz sand and the remainder being high-purity natural quartz sand. The synthetic quartz sand has a particle size of 150μm~200μm and a purity of not less than 99.99999%; the high-purity natural quartz sand has a particle size of 200μm~250μm and a purity of not less than 99.9999%.

[0079] During the preparation process, the rotation speed of mold 6 is 67 rpm.

[0080] Phase 1: Air is introduced into mold 6 at a speed of 1 mm / s through air intake system 1, while helium is introduced into mold 6 at a gauge pressure of -0.08 MPa through helium intake system 3. The gas inside mold 6 is discharged outward through exhaust system 4 at a speed of 2 mm / s. Mold vacuum system 5 is used to evacuate mold 6 to maintain a vacuum level of -0.02 MPa. During this phase, the volume of helium in the melting chamber is 10% of the total volume of helium and air.

[0081] The second stage involves introducing air into mold 6 at a speed of 6 mm / s through air intake system 1, while simultaneously introducing helium into mold 6 at a gauge pressure of -0.1 MPa through helium intake system 3. The exhaust system 4 then expels the gas from inside mold 6 at a speed of 5 mm / s. A vacuum system 5 is used to evacuate mold 6, maintaining a vacuum level of -0.095 MPa. This process is further enhanced by arc melting via electrode 2, forming a transparent layer 7 of quartz sand in the arc-affected area. The arc melting conditions include: a current of 2200 A, an arc duration of 8 minutes, an electrode spacing of 20 mm, and a vertical distance of 150 mm between the arc-initiating tip of electrode 2 and the upper port of the rotating mold 6.

[0082] The third stage involves: introducing air into mold 6 through air intake system 1 at a speed of 6 mm / s; closing helium intake system 3; exhausting gas from mold 6 through exhaust system 4 at a speed of 5 mm / s; and evacuating mold 6 through mold vacuum system 5 to maintain a vacuum level of -0.030 MPa. This process also involves arc melting via electrode 2, causing the quartz sand in the arc-affected area to form a bubble layer 8. The arc melting conditions include: a current of 2700 A, an arc duration of 12 min, an electrode spacing of 30 mm, and a vertical distance of 100 mm between the arc-initiating end of electrode 2 and the upper port of the rotating mold 6.

[0083] Fourth stage: Air is introduced into mold 6 through air intake system 1 at a speed of 3 mm / s; helium intake system 3 is closed; gas in mold 6 is discharged out through exhaust system 4 at a speed of 4 mm / s; mold vacuum system 5 is closed.

[0084] Fifth stage: Shut down the air intake system 1, helium intake system 3 and mold vacuum system 5; exhaust the gas in the mold 6 through the exhaust system 4 at a speed of 2mm / s.

[0085] Example 3 This embodiment provides a synthetic quartz crucible with an outer diameter of 811 mm and a height of 515 mm, which is prepared using the preparation equipment provided in Example 1. The thickness of the transparent layer 7 in this synthetic quartz crucible is 3 mm, and the thickness of the bubble layer 8 is 13 mm.

[0086] The preparation process of the synthetic quartz crucible includes: first, laying high-purity natural quartz sand, then laying synthetic quartz sand mold 6 in the order from the outside to the inside, and then controlling the conditions of the air inlet system 1, helium air inlet system 3, and exhaust system 4 in the following five stages.

[0087] The quartz sand used to prepare the synthetic quartz crucible comprises, by mass percentage, 9% synthetic quartz sand, with the remainder being high-purity natural quartz sand. The synthetic quartz sand has a particle size of 150μm~200μm and a purity of not less than 99.99999%; the high-purity natural quartz sand has a particle size of 200μm~250μm and a purity of not less than 99.9999%.

[0088] During the preparation process, the rotation speed of mold 6 is 68 rpm.

[0089] Phase 1: Air is introduced into mold 6 through air intake system 1 at a speed of 1.2 mm / s, while helium is introduced into mold 6 through helium intake system 3 at a gauge pressure of -0.1 MPa. The exhaust system 4 expels the gas from inside mold 6 at a speed of 2.5 mm / s. Mold vacuum system 5 evacuates mold 6 to maintain a vacuum level of -0.025 MPa. During this phase, the volume of helium in the melting chamber is 5% of the total volume of helium and air.

[0090] The second stage involves introducing air into mold 6 through air intake system 1 at a speed of 6.5 mm / s, while simultaneously introducing helium into mold 6 through helium intake system 3 at a gauge pressure of -0.1 MPa. Exhaust system 4 expels the gas from mold 6 at a speed of 5.5 mm / s. Mold vacuum system 5 maintains a vacuum level of -0.098 MPa within mold 6. This process is further enhanced by arc melting via electrode 2, forming a transparent layer 7 of quartz sand in the arc-affected area. The arc melting conditions include: a current of 2000 A, an arc duration of 8 minutes, an electrode spacing of 22 mm, and a vertical distance of 180 mm between the arc-initiating end of electrode 2 and the upper port of the rotating mold 6.

[0091] The third stage involves: introducing air into mold 6 through air intake system 1 at a speed of 6.5 mm / s; closing helium intake system 3; exhausting gas from mold 6 through exhaust system 4 at a speed of 5.5 mm / s; and evacuating mold 6 through mold vacuum system 5 to maintain a vacuum level of -0.035 MPa. This process also involves arc melting via electrode 2, causing the quartz sand in the arc-affected area to form a bubble layer 8. The arc melting conditions include: a current of 2850 A, an arc duration of 13 min, an electrode spacing of 33 mm, and a vertical distance of 130 mm between the arc-initiating end of electrode 2 and the upper port of the rotating mold 6.

[0092] Fourth stage: Air is introduced into mold 6 through air intake system 1 at a speed of 3.5 mm / s; helium intake system 3 is closed; gas in mold 6 is discharged out through exhaust system 4 at a speed of 4.5 mm / s; mold vacuum system 5 is closed.

[0093] Fifth stage: Shut down the air intake system 1, helium intake system 3 and mold vacuum system 5; exhaust the gas in the mold 6 through the exhaust system 4 at a speed of 2.5 mm / s.

[0094] Example 4 This embodiment provides a synthetic quartz crucible with an outer diameter of 813 mm and a height of 530 mm, which is prepared using the preparation equipment provided in Example 1. The thickness of the transparent layer 7 in this synthetic quartz crucible is 4 mm, and the thickness of the bubble layer 8 is 12 mm.

[0095] The preparation process of the synthetic quartz crucible includes: first, laying high-purity natural quartz sand, then laying synthetic quartz sand mold 6 in the order from the outside to the inside, and then controlling the conditions of the air intake system 1, helium intake system 3, and exhaust system 4 in the following five stages.

[0096] The quartz sand used to prepare the synthetic quartz crucible comprises, by mass percentage, 10% synthetic quartz sand and the remainder high-purity natural quartz sand. The synthetic quartz sand has a particle size of 150μm~200μm and a purity of not less than 99.99999%; the high-purity natural quartz sand has a particle size of 200μm~250μm and a purity of not less than 99.9999%.

[0097] During the preparation process, the rotation speed of mold 6 is 69 rpm.

[0098] Phase 1: Air is introduced into mold 6 at a speed of 1.5 mm / s through air intake system 1, while helium is introduced into mold 6 at a gauge pressure of -0.12 MPa through helium intake system 3. The exhaust system 4 expels the gas from inside mold 6 at a speed of 3 mm / s. Mold vacuum system 5 evacuates mold 6 to maintain a vacuum level of -0.03 MPa. During this phase, the volume of helium in the melting chamber is 15% of the total volume of helium and air.

[0099] The second stage involves introducing air into mold 6 at a speed of 7 mm / s through air intake system 1, while simultaneously introducing helium into mold 6 at a gauge pressure of -0.15 MPa through helium intake system 3. The exhaust system 4 then expels the gas from inside mold 6 at a speed of 6 mm / s. A mold vacuum system 5 is used to evacuate mold 6 to maintain a vacuum level of -0.099 MPa. This process is further enhanced by arc melting via electrode 2, forming a transparent layer 7 of quartz sand in the arc-affected area. The arc melting conditions include: a current of 2300 A, an arc duration of 6 minutes, an electrode spacing of 25 mm, and a vertical distance of 200 mm between the arc-initiating tip of electrode 2 and the upper port of the rotating mold 6.

[0100] The third stage involves: introducing air into the mold 6 through the air intake system 1 at a speed of 7 mm / s; closing the helium intake system 3; expelling the gas from the mold 6 through the exhaust system 4 at a speed of 6 mm / s; and maintaining a vacuum of -0.040 MPa in the mold 6 through the mold vacuum system 5. This process also involves arc melting via the action of electrode 2, causing the quartz sand in the arc-affected area to form a bubble layer 8. The arc melting conditions include: a current of 3000 A, an arc duration of 15 min, an electrode spacing of 35 mm, and a vertical distance of 150 mm between the arc-initiating end of electrode 2 and the upper port of the rotating mold 6.

[0101] Fourth stage: Air is introduced into mold 6 through air intake system 1 at a speed of 4 mm / s; helium intake system 3 is closed; gas in mold 6 is discharged out through exhaust system 4 at a speed of 5 mm / s; mold vacuum system 5 is closed.

[0102] Fifth stage: Shut down the air intake system 1, helium intake system 3 and mold vacuum system 5; exhaust the gas in the mold 6 through the exhaust system 4 at a speed of 3mm / s.

[0103] Comparative Example 1 The difference between this comparative example and Example 2 is that no helium gas was introduced in either the first or second stage.

[0104] Comparative Example 2 The difference between this comparative example and Example 2 is that in the first stage, the volume of helium is 2% of the total volume of helium and air.

[0105] Comparative Example 3 The difference between this comparative example and Example 2 is that in the second stage, the air intake velocity is 6 mm / s and the air exhaust velocity is 6.5 mm / s; that is, the air intake velocity is less than the air exhaust velocity.

[0106] Comparative Example 4 The difference between this comparative example and Example 2 is that in the fourth stage, the air intake velocity and the air exhaust velocity are equal, both being 4 mm / s.

[0107] Comparative Example 5 The difference between this comparative example and Example 2 is that in the fourth stage, the air intake velocity is 4.5 mm / s and the air exhaust velocity is 4 mm / s; that is, the air intake velocity is greater than the air exhaust velocity.

[0108] Comparative Example 6 The difference between this comparative example and Example 2 is that no temperature and humidity control device is installed between the primary filter and the secondary filter; that is, no temperature and humidity control is performed before the air enters the melting chamber.

[0109] Test case Using a commercially available conventional quartz crucible of the same size as a control, the synthetic quartz crucibles prepared in Examples 2-4 and Comparative Examples 1-6, as well as the aforementioned control quartz crucibles, were subjected to crystal pulling under the same conditions. The average number of brown rings in the straight-wall region and R region of each quartz crucible after crystal pulling was compared. The results are shown in Table 1 and... Figures 3 to 6 As shown.

[0110] Table 1 Test Results

[0111] As can be seen from Table 1, the method for preparing synthetic quartz crucibles provided by the present invention can effectively reduce the number of brown rings after the synthetic quartz crucibles are used.

[0112] Depend on Figure 3 and Figure 5 Comparison, and Figure 4 and Figure 6The comparison shows that the synthetic quartz crucible prepared in Example 2 has significantly fewer brown rings on both the surface of the straight arm region and the surface of the R region after crystal pulling compared to the control quartz crucible.

[0113] In summary, this invention improves the environmental system during the preparation of synthetic quartz crucibles. In the second stage, positive pressure is introduced to reduce harmful gases generated by the ablation of graphite electrode 2 and the formation of impurity-rich zones on the inner surface of the synthetic quartz crucible due to graphite impurities. This reduces the probability of brown ring formation caused by the presence of these impurity-rich zones. By combining the air intake system 1 and the helium intake system 3, the problem of uncontrollable environment in the original melting process, which led to severe contamination of the inner surface of the produced synthetic quartz crucibles and bubble rupture, is addressed, further reducing the probability of brown ring formation. In the fourth stage, controlling the exhaust and intake air speeds prevents some residual quartz particles floating in the melting chamber from falling back into the crucible, causing quartz particles to adhere to the inner surface and create structural defects. Therefore, the solution provided by this invention can improve environmental pollution and structural defects during the production of large-size synthetic quartz crucibles, thereby reducing the number of brown rings formed on the inner surface of the synthetic quartz crucible after use.

[0114] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A synthetic quartz crucible preparation apparatus, characterized in that, This includes the melting chamber, air intake system, electrodes, helium gas intake system, exhaust system, mold vacuum system, and mold; The mold, the mold vacuum system, and the electrode are all located in the melting chamber; the melting chamber is connected to the air inlet system, the helium gas inlet system, and the exhaust system; the mold vacuum system is located on the outside of the mold, and the mold has an airflow channel connected to the mold vacuum system so that the mold vacuum system can evacuate the mold; the electrode is located above the mold.

2. The preparation apparatus according to claim 1, characterized in that, According to the airflow direction, the air intake system includes a pre-filter, a medium-efficiency filter, and a high-efficiency filter arranged sequentially from the outside to the inside.

3. The preparation apparatus according to claim 2, characterized in that, Between the primary filter and the secondary filter, there is at least one of a temperature control device and a humidity control device.

4. A method for suppressing brown rings on the inner surface of a synthetic quartz crucible, characterized in that, The preparation is carried out using the preparation equipment described in any one of claims 1 to 3; The preparation process includes: laying quartz sand in a mold, and then controlling the conditions of the air intake system, helium intake system, and exhaust system in the following five stages: Phase 1: Air is introduced into the mold through the air intake system at a speed of 1 mm / s to 1.5 mm / s, while helium is introduced into the mold through the helium intake system at a gauge pressure of -0.08 MPa to -0.12 MPa. The gas inside the mold is discharged outward through the exhaust system at a speed of 2 mm / s to 3 mm / s. The mold vacuum system is used to evacuate the mold to maintain a vacuum level of -0.02 MPa to -0.03 MPa. The second stage involves introducing air into the mold through the air intake system at a speed of 6 mm / s to 7 mm / s, while simultaneously introducing helium into the mold through the helium intake system at a gauge pressure of -0.1 MPa to -0.15 MPa. The exhaust system then expels the gas from the mold outwards at a speed of 5 mm / s to 6 mm / s, with the intake speed exceeding the exhaust speed. Finally, the mold vacuum system is used to evacuate the mold to maintain a vacuum level of -0.095 MPa to -0.099 MPa. The third stage involves: introducing air into the mold through the air intake system at a speed of 6 mm / s to 7 mm / s; closing the helium intake system; exhausting the gas from the mold through the exhaust system at a speed of 5 mm / s to 6 mm / s; and using the mold vacuum system to evacuate the mold to maintain a vacuum level of -0.030 MPa to -0.040 MPa. Fourth stage: Air is introduced into the mold through the air intake system at a speed of 3mm / s to 4mm / s; the helium intake system is closed; the gas in the mold is discharged outward through the exhaust system at a speed of 4mm / s to 5mm / s, and the exhaust speed is greater than the intake speed; the mold vacuum system is closed. Fifth stage: shut down the air intake system, the helium intake system, and the mold vacuum system; exhaust the gas inside the mold through the exhaust system at a speed of 2mm / s to 3mm / s.

5. The method according to claim 4, characterized in that, In the first stage, the volume of helium in the melting chamber is 5% to 15% of the total volume of helium and air.

6. The method according to claim 4, characterized in that, In the second stage, electric arc melting is performed through electrodes to form a transparent layer of quartz sand in the area affected by the electric arc. The conditions for arc melting include: a current of 2000A~2300A, an arc duration of 6min~8min, an electrode spacing of 20mm~25mm, and a vertical distance of 150mm~200mm between the arc-starting end of the electrode and the upper port of the rotating mold.

7. The method according to claim 4, characterized in that, In the third stage, electric arc melting is performed through electrodes to form a bubble layer in the quartz sand in the area affected by the electric arc. The conditions for arc melting include: a current of 2700A~3000A, an arc duration of 12min~15min, an electrode spacing of 30mm~35mm, and a vertical distance of 100mm~150mm between the arc-starting end of the electrode and the upper port of the rotating mold.

8. The method according to claim 4, characterized in that, During the preparation process, the mold rotates at a speed of 67 rpm to 69 rpm.

9. The method according to claim 4, characterized in that, The quartz sand used to prepare the synthetic quartz crucible comprises 8% to 10% synthetic quartz sand by mass percentage, with the remainder being high-purity natural quartz sand. The synthetic quartz sand has a particle size of 150μm to 200μm and a purity of not less than 99.99999%; the high-purity natural quartz sand has a particle size of 200μm to 250μm and a purity of not less than 99.9999%.

10. A synthetic quartz crucible, characterized in that, It is prepared by the method described in any one of claims 4 to 9.

Images