How to make high quality quartz crucibles

Abstract

The present invention relates to a method for producing a high-quality quartz crucible, and the melting method is a vacuum arc method. The graphite electrode position movement and the residence time at each position meet the following conditions: the position of the end surface of the upper opening of the mold is zero point, the end of the graphite electrode is + above zero point, and - below zero point. The initial position of the graphite electrode is +0.10~0.30 times the outer diameter of the crucible, and the residence time is ≧2 minutes. Then, the position is sequentially lowered according to the stepwise movement method, and a certain time is required for each position to be lowered. The graphite electrode is held at the bottom of the crucible and moves at least three times before reaching the bottom polishing position, which is the lowest position reached by the graphite electrode and enters the inside of the initial crucible product, and is 300-550 mm away from the bottom of the crucible, where the graphite electrode is held at the bottom of the crucible and performs high-temperature polishing and volatilization removal, and then rises to the finishing stage, which is +0.05 to 0.07 times the outer diameter of the crucible, and where the upper part of the inner wall of the quartz crucible is polished at high temperature and volatilized. The present invention is used to improve the purity of the transparent layer of the quartz crucible and improve the high-temperature deformation resistance, etc.

Description

[Technical field]

[0001] The present invention relates to the technical field of producing silicon single crystals, and more specifically to a method for producing a quartz crucible used in producing silicon single crystals by the Czochralski method (hereinafter abbreviated as CZ Czochralski method). [Background technology]

[0002] Silicon single crystals are one of the most important materials for the manufacture of silicon-based semiconductor materials and solar cells. Silicon single crystals are mainly obtained by the CZ Czochralski method. In the CZ Czochralski method, polycrystalline silicon raw material is placed in a quartz crucible, molten silicon is heated, and a rod lowers a seed crystal to contact the silicon melt, and then the seed crystal is slowly pulled up to form a silicon single crystal ingot. Quartz crucibles generally have a two-layer structure, with the inner wall being a transparent layer that does not contain bubbles, and the outer wall being a non-transparent layer with a high bubble content. Since the inner wall comes into contact with the silicon melt, if there are bubbles on the inner wall at high temperatures, the bubbles will be eroded by the silicon melt and burst, and the broken pieces will dissolve in the silicon melt, which will affect the yield and quality of the silicon single crystal. The outer wall needs to uniformly scatter the heat from the heater, so a certain number and size of bubbles are required, and the silicon melt is heated uniformly. As the only material in contact with the silicon solution, the quality of the quartz crucible has a great influence on the quality of the silicon single crystal, such as the bubble content on the inner wall of the quartz crucible, the purity of the quartz crucible, and the high-temperature deformation resistance of the quartz crucible.

[0003] Quartz crucibles are generally manufactured by the vacuum arc method. When this method is adopted, high-purity quartz sand raw material is placed in a graphite or metal mold, and the quartz sand raw material is uniformly molded on the inner surface of the mold by a molding device. Then, the quartz sand is melted at a high temperature of 3000°C or higher by a high-temperature arc (usually three graphite electrodes in a three-phase arc furnace), and finally, a quartz (glass) crucible is formed by quenching. In the process of manufacturing quartz crucibles by the vacuum arc method, the temperature of the arc has a great influence on the quality of the quartz crucible, such as the content of bubbles on the inner wall of the crucible, purity, high-temperature deformation resistance, and degree of vitrification, so it is important to optimize the control of the arc.

[0004] In controlling the arc temperature, the movement of the graphite electrode (the position of the end of the electrode relative to the upper end surface of the mold) can greatly improve the production quality of the quartz crucible when the current is constant (when the power device does not change). However, currently, the movement of the electrode in the process of manufacturing the quartz crucible generally adopts a fixed position melting method (referred to as the fixed movement method or fixed type method in this application, abbreviated as the FT method). The movement of the graphite electrode in the FT method is fixed, and the graphite electrode is periodically lowered to compensate for wear (lowered by one step to compensate for the loss of the electrode), and at the same time, the production quality of the quartz crucible is improved only by adjusting the magnitude of the current. However, in actual production, the improvement of the quality of the quartz crucible by only adjusting the magnitude of the current is very limited, and the production equipment has a limited current that can be withstood when its component hardware is assembled, so it is difficult to improve the production quality of the crucible by replacing the large current, and the cost of changing the hardware and rebuilding the equipment is also very high. Up to now, the production method for improving the quality of the quartz crucible is still a problem that researchers in the industry need to solve. Summary of the Invention

[0005] (1) Technical issues to be resolved

[0006] In view of the above-mentioned shortcomings and deficiencies of the prior art, the present invention provides a method for manufacturing a high-quality quartz crucible, which mainly manufactures a high-quality quartz crucible by controlling the position movement of the graphite electrode and the time allocation of each position, thereby improving the high-temperature resistance strength suitable for the crucible, improving the purity of the transparent layer, reducing bubbles on the inner wall of the crucible, and so on, thereby solving the technical problems associated with the prior art of changing the current in a fixed movement to improve the quality of the crucible.

[0007] (2)Technical plan

[0008] To achieve the above objectives, the main technical solutions adopted in the present invention include:

[0009] According to a first aspect, the present invention provides a method for manufacturing a high-quality quartz crucible, which adopts a vacuum arc method and includes the following steps:

[0010] High-purity quartz sand raw material is placed into a crucible mold, and a molding device is used to uniformly mold the quartz sand raw material on the inner surface of the mold to form a crucible initial product. The entire crucible mold is then transferred to an arc smelting furnace, and a high-temperature arc is emitted by a graphite electrode to melt the quartz sand. Finally, it is quenched to form a quartz crucible blank. In the process of emitting a high-temperature arc using the graphite electrode, the positional movement of the graphite electrode in the height direction and the residence time at each position are controlled to satisfy the following conditions:

[0011] The position of the end surface of the upper opening of the mold is the zero point, the end of the graphite electrode is marked with + when it is above the zero point, and marked with - when it is below the zero point. During the smelting process, the initial position of the graphite electrode is +(0.10-0.30) times the outer diameter of the crucible, and the residence time is ≧2 minutes. Then, the position is sequentially lowered according to the step movement method, and each position is lowered and stayed for a certain time, so that the graphite electrode continuously emits high-temperature arc during the corresponding period of the corresponding position to melt the crucible initial product, and after moving at least three times, it reaches the bottom polishing position, and the bottom polishing position is the lowest position reached by the graphite electrode and enters the inside of the crucible (the position is negative), and is 300-550 mm away from the bottom of the crucible. At the bottom polishing position, the graphite electrode stays for a certain time to perform high-temperature polishing and volatilization removal at the bottom of the crucible;

[0012] After the graphite electrode leaves the bottom grinding position, it rises to a finishing stage, which is +(0.05-0.07) times the outer diameter of the crucible, where the upper part of the inner wall of the quartz crucible is polished at high temperature and volatilized off.

[0013] Here, when the number of movements from the initial position to the bottom polishing position is three, the height difference between two adjacent positions is ≧50 mm, and when the number of movements from the initial position to the bottom polishing position is more than three, the height difference between two steps does not need to be ≧50 mm.

[0014] According to a preferred embodiment of the present invention, during the entire smelting process, the movement of the graphite electrode includes an initial position, a second position, a third position, a fourth position, a fifth position, a bottom grinding position and a finishing stage, where it descends stepwise from the initial position to the bottom grinding position and stays at each position for a certain time.

[0015] According to a preferred embodiment of the present invention, the residence time of the graphite electrode at each position is 0.4-0.5t, the residence time at the fourth position is 0.1-0.2t, the residence time at the fifth position is 0.1t, the residence time at the bottom polishing position is 0.2-0.3t, and the residence time at the finishing stage is 0.1t, where t is the total melting time of the target quartz crucible.

[0016] According to a preferred embodiment of the present invention, the residence time of the graphite electrode at each position according to different dimensions of the quartz crucible is as follows: quartz crucible with an outer diameter of 24 inches: the sum of the residence times at the initial position, the second position and the third position is 0.4t, the residence time at the fourth position is 0.2t, the residence time at the fifth position is 0.1t, the residence time at the bottom grinding position is 0.2t, and the residence time at the finishing stage is 0.1t; the total melting time is 14-16 minutes, and preferably 15 minutes;

[0017] Quartz crucible with an outer diameter of 26 inches: the sum of the residence times in the initial position, the second position, and the third position is 0.45t, the residence time in the fourth position is 0.15t, the residence time in the fifth position is 0.1t, the residence time in the bottom grinding position is 0.2t, and the residence time in the finishing stage is 0.1t; the total melting time is 17-19 minutes, preferably 18 minutes;

[0018] Quartz crucible with an outer diameter of 28 inches: the sum of the residence times in the initial position, the second position, and the third position is 0.45t, the residence time in the fourth position is 0.1t, the residence time in the fifth position is 0.1t, the residence time in the bottom grinding position is 0.25t, and the residence time in the finishing stage is 0.1t, and the total melting time is 22-26 minutes, preferably 24 minutes;

[0019] Quartz crucible with an outer diameter of 32 inches: the sum of the residence times at the initial position, the second position and the third position is 0.4t, the residence time at the fourth position is 0.1t, the residence time at the fifth position is 0.1t, the residence time at the bottom polishing position is 0.3t, the residence time at the finishing stage is 0.1t, and the total melting time is 28-32 minutes, preferably 30 minutes.

[0020] According to a preferred embodiment of the present invention, the graphite electrode has a positioning accuracy of ±5 mm from one position to another during the movement process.

[0021] According to a preferred embodiment of the present invention, the vacuum level is controlled at -0.093Mpa to -0.1Mpa during the entire smelting process, and the power of the graphite electrodes is 500-2000KW.

[0022] According to a preferred embodiment of the present invention, when a quartz crucible with an outer diameter of 24 inches is melted, the power of the graphite electrode is 750-850 KW, when a quartz crucible with an outer diameter of 26 inches is melted, the power of the graphite electrode is 850-950 KW, when a quartz crucible with an outer diameter of 28 inches is melted, the power of the graphite electrode is 1000-1100 KW, and when a quartz crucible with an outer diameter of 32 inches is melted, the power of the graphite electrode is 1300-1400 KW.

[0023] According to a preferred embodiment of the present invention, during the movement of the graphite electrode, when the melting at each position is completed, the graphite electrode is blown out to purge and remove volatiles accumulated on the surface of the graphite electrode.

[0024] According to a preferred embodiment of the invention, the height difference between the bottom grinding position (or bottoming position, ie also the lowest position reached by the graphite electrode) and the fifth position is greater than or equal to 100 mm.

[0025] According to a preferred embodiment of the present invention, the manufactured quartz crucible blanks are cut, inspected, cleaned, dried, and packaged in order.

[0026] The movement of the graphite electrode of the present invention is controlled by the PLC module program.

[0027] According to a second aspect, the present invention provides a high-quality quartz crucible manufactured using the manufacturing method according to any one of the above embodiments.

[0028] (3) Beneficial Effects

[0029] The present invention can greatly improve the quality of the quartz crucible by precisely controlling the initial position of the graphite electrode, and then sequentially descending it to the bottom polishing position (the position is negative) by a step-by-step moving method in accordance with the residence time (the time to emit high-temperature arc) at each position, including reducing bubbles on the inner wall of the quartz crucible, improving the purity of the transparent layer of the crucible, improving the high-temperature deformation resistance performance, and reducing the sagging rate of the crucible wall during the crystal growth process, thereby providing support for improving the yield and production quality of silicon single crystals produced by the CZ Czochralski method.

[0030] Compared with the fixed moving method, the present invention does not simply improve the quality of the crucible by increasing the working current of the graphite electrode, but is more flexible and suitable for the production of crucibles with various specifications without changing each hardware of the quartz crucible equipment. The graphite electrode reaches the inside of the crucible by descending from the initial position to the bottom polishing position at least three times, and approaches the bottom of the crucible. During the entire melting process, the graphite electrode gradually approaches the center of the inside of the crucible initial product, and according to the allocation of the electrode residence time at each position, the inner surface of the crucible is uniformly distributed heat to each part such as the straight wall surface, the arc-shaped excess part and the bottom, and is locally subjected to further high temperature concentrated treatment, so that the impurities contained in the inner surface of the crucible are volatilized at high temperature, the purity of the transparent layer of the crucible is improved, and the quality of the silicon single crystal is further guaranteed. After the graphite electrode reaches the lowest position and polishes the bottom of the crucible at high temperature, it moves above the crucible mold to the finishing stage and rises to process the upper opening of the crucible, and removes the impurities that have accumulated on the upper part of the inner wall of the crucible after volatilization. By comparison, the present invention can effectively reduce the content of impurities on the inner wall surface of the crucible, improve the high-temperature deformation resistance of the crucible, and reduce the sagging rate of the crucible wall during the crystal growth process. [Brief description of the drawings]

[0031] [Figure 1] FIG. 2 is a schematic diagram of the structure of a quartz crucible. [Diagram 2] FIG. 1 is a schematic diagram of a quartz crucible manufactured using a high temperature arc melting process. [Diagram 3]FIG. 2 is a diagram showing the initial position and zero point position of the graphite electrode in the process of manufacturing a quartz crucible using a high-temperature arc melting method. [Figure 4] FIG. 2 is a diagram showing the movement positions of the graphite electrodes and the time allocation at each position when manufacturing a 26-inch quartz crucible in Example 1. [Diagram 5] FIG. 13 is a diagram showing the movement positions of the graphite electrodes and the time allocation at each position when manufacturing a 26-inch quartz crucible in Example 2. [Figure 6] FIG. 11 is a diagram showing the movement position of the graphite electrode and the time allocation at each position when manufacturing a 26-inch quartz crucible in Example 3. [Figure 7] FIG. 13 is a diagram showing the movement position of the graphite electrode and the time allocation at each position when manufacturing a 24-inch quartz crucible in Example 4. [Figure 8] FIG. 13 is a diagram showing the movement position of the graphite electrode and the time allocation at each position when manufacturing a 28-inch quartz crucible in Example 5. [Figure 9] FIG. 13 is a diagram showing the movement position of the graphite electrode and the time allocation at each position when manufacturing a 32-inch quartz crucible in Example 6. [Figure 10] FIG. 2 is a diagram showing the sagging state of the end face of a quartz crucible after a silicon single crystal is produced by the CZ method. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0032] In order to make the present invention easier to understand, the present invention will now be described in detail with reference to specific embodiments and with reference to the drawings.

[0033] As shown in Figure 1, the schematic diagram of a quartz crucible includes an inner transparent layer 1 and an outer non-transparent layer 2. The transparent layer 1 is in direct contact with the silicon melt. The transparent layer 1 has a straight wall surface H, an arc-shaped transition surface L, and a bottom surface W.

[0034] As shown in FIG. 2, FIG. 2 is a schematic diagram of a quartz crucible manufactured using a high-temperature arc melting method in the prior art. In the prior art, a graphite electrode 3 enters the inside of a crucible mold, and the graphite electrode 3 emits a high-temperature arc to melt quartz raw material. As the graphite electrode 3 wears out in the process of emitting a high-temperature arc, the graphite electrode 3 moves constantly, but the distance between the lower end of the graphite electrode and the bottom of the crucible is constant during the entire melting process. This technology may be defined as a fixed movement method in this application. Fixed movement means that the distance from the lower end of the graphite electrode to the opening upper end surface (zero point) of the mold does not change.

[0035] As shown in FIG. 3, the present invention improves the distribution of heat in the quartz crucible melting process by changing the position of the lower end of the graphite electrode in the prior art, specifically, by gradually changing the distance of the lower end of the graphite electrode relative to the upper end surface of the mold opening (hereinafter simply referred to as the position of the graphite electrode). In the process of changing the graphite electrode position, the present invention adopts a stepwise descending mode controlled by the PLC module program. When the graphite electrode reaches the inside of the crucible to grind the bottom of the crucible to a high temperature, this position is called the bottom grinding position. The stepwise descending includes two layers, the first layer being the continuous descending of the graphite electrode position, and the second layer being the dwelling at each position for a certain time, during which the graphite electrode continuously emits a high-temperature arc to heat the crucible to melt and remove impurities by high-temperature volatilization. During the high-temperature arc emission, the temperature can reach 3000-3600 degrees, and some metal impurities volatilize at this temperature, thereby cleaning the transparent layer 1 of the crucible and ensuring the production quality of silicon single crystals. After the bottom grinding operation is completed, the graphite electrode rises again above the opening of the mold, and the impurities accumulated on the upper part of the inner wall of the crucible are volatilized at high temperatures (during the bottom grinding, some of the impurities volatilize and are re-deposited in the area where the temperature drops). After the melting is completed, it is cooled to obtain a quartz crucible blank, which is then cut, inspected, cleaned, dried, and packaged for storage.

[0036] As shown in Figure 3, the position of the upper end surface of the mold is the zero point, and the end of the graphite electrode is marked + above the zero point, and marked - below the zero point.

[0037] In the smelting process, the initial position of the graphite electrode is +(0.10-0.30) times the outer diameter of the crucible, and the residence time is ≧2 minutes. Then, the position is sequentially lowered according to the step movement method, and the graphite electrode stays at each position for a certain time, and the graphite electrode continuously emits high-temperature arc during the corresponding period of the corresponding position to smelt the crucible initial product, and after moving at least three times, it reaches the bottom polishing position, which is the lowest position reached by the graphite electrode and enters the inside of the crucible (the position is negative), and is 300-550 mm away from the bottom of the crucible. At the bottom polishing position, the graphite electrode stays for a certain time to perform high-temperature polishing and volatilization removal at the bottom of the crucible;

[0038] After the graphite electrode leaves the bottom polishing position, it rises to a finishing stage, which is +(0.05-0.07) times the outer diameter of the crucible, where the upper part of the inner wall of the quartz crucible is polished at high temperature and volatilized off.

[0039] During the entire smelting process, the movement of the graphite electrode includes an initial position, a second position, a third position, a fourth position, a fifth position, a bottom grinding position and a finishing stage, where it descends stepwise from the initial position to the bottom grinding position and stays at each position for a certain time, and the positioning accuracy of the graphite electrode at each position is ±5mm.

[0040] Preferably, the residence time at each position of the graphite electrode is 0.4-0.5t, the residence time at the fourth position is 0.1-0.2t, the residence time at the fifth position is 0.1t, the residence time at the bottom polishing position is 0.2-0.3t, and the residence time at the finishing stage is 0.1t, where t is the total melting time of the target quartz crucible.

[0041] In addition, the residence time of the graphite electrode at each position according to different specifications of the quartz crucible is as follows: quartz crucible with an outer diameter of 24 inches: the sum of the residence times at the initial position, the second position and the third position is 0.4t, the residence time at the fourth position is 0.2t, the residence time at the fifth position is 0.1t, the residence time at the bottom polishing position is 0.2t, and the residence time at the finishing stage is 0.1t, and the total melting time is 14-16 minutes, preferably 15 minutes;

[0042] Quartz crucible with an outer diameter of 26 inches: the sum of the residence times in the initial position, the second position, and the third position is 0.45t, the residence time in the fourth position is 0.15t, the residence time in the fifth position is 0.1t, the residence time in the bottom grinding position is 0.2t, and the residence time in the finishing stage is 0.1t; the total melting time is 17-19 minutes, preferably 18 minutes;

[0043] Quartz crucible with an outer diameter of 28 inches: the sum of the residence times in the initial position, the second position, and the third position is 0.45t, the residence time in the fourth position is 0.1t, the residence time in the fifth position is 0.1t, the residence time in the bottom grinding position is 0.25t, and the residence time in the finishing stage is 0.1t, and the total melting time is 22-26 minutes, preferably 24 minutes;

[0044] Quartz crucible with an outer diameter of 32 inches: the sum of the residence times at the initial position, the second position and the third position is 0.4t, the residence time at the fourth position is 0.1t, the residence time at the fifth position is 0.1t, the residence time at the bottom polishing position is 0.3t, the residence time at the finishing stage is 0.1t, and the total melting time is 28-32 minutes, preferably 30 minutes.

[0045] Preferably, the degree of vacuum is controlled to -0.093 MPa to -0.1 MPa throughout the entire smelting process, and the power of the graphite electrodes is 500-2000 kW.

[0046] Preferably, when a quartz crucible with an outer diameter of 24 inches is melted, the power of the graphite electrode is 750-850 KW, when a quartz crucible with an outer diameter of 26 inches is melted, the power of the graphite electrode is 850-950 KW, when a quartz crucible with an outer diameter of 28 inches is melted, the power of the graphite electrode is 1000-1100 KW, and when a quartz crucible with an outer diameter of 32 inches is melted, the power of the graphite electrode is 1300-1400 KW.

[0047] Preferably, during the movement of the graphite electrode, when the melting at each position is completed, the graphite electrode is blown out to purge and remove volatiles accumulated on the surface of the graphite electrode.

[0048] Preferably, the height difference between the bottom grinding position (or bottoming position, ie also the lowest position reached by the graphite electrode) and the fifth position is greater than or equal to 100 mm.

[0049] The features and advantages of the present invention will be described below with reference to the preferred embodiments of the present invention. Unless otherwise specified, in the following examples, the raw materials are all quartz raw materials from the same batch, and the purity of the high-purity quartz sand is ≧99.99%.

[0050] Example 1

[0051] This embodiment provides a method for manufacturing a high-quality quartz crucible with an outer diameter of 26 inches, using the vacuum arc method, and the manufacturing steps are as follows:

[0052] (1) High-purity quartz sand powder is mixed uniformly in a crucible mold and molded.

[0053] (2) The mold is then loaded into the arc furnace.

[0054] (3) The position of the open top end surface of the mold is set as the zero point, and the movement of the graphite electrode controlled by the PLC program melts the quartz crucible as shown in Figure 4. In the figure, the graphite electrode operates at a total of seven positions, staying at the initial position for 3 min, the second position for 3 min, the third position for 3 min, the fourth position for 1.8 min, the fifth position for 1.8 min, the bottom polishing position for 3.6 min (310 mm away from the bottom of the crucible), and the finishing stage for 1.8 min.

[0055] During the smelting process, the output of the graphite electrode is 900KW, the accuracy at each position is ±5mm, and the degree of vacuum is controlled at -0.093MPa to -0.1Mpa. When smelting at each step is completed, a blowout is performed on the graphite electrode to purge and remove the accumulated volatiles.

[0056] (4) After melting, the quartz crucible is cooled and removed from the furnace to complete the production of the quartz crucible blank.

[0057] (5) The manufactured quartz crucible blanks are cut, inspected, cleaned, dried, packaged, and stored in the following order.

[0058] Example 2

[0059] In this embodiment, based on the embodiment 1, the movement of the graphite electrode controlled by the PLC program melts the quartz crucible as shown in Fig. 5. In the figure, the graphite electrode operates in a total of seven positions, staying at the initial position for 3 min, at the second position for 2 min, at the third position for 3.1 min, at the fourth position for 2.7 min, at the fifth position for 1.8 min, at the bottom polishing position for 3.6 min (300 mm away from the crucible bottom), and at the finishing stage for 1.8 min.

[0060] Example 3

[0061] In this embodiment, based on the embodiment 1, the graphite electrode travels under the control of a PLC program to melt the quartz crucible, as shown in Fig. 6. In the figure, the graphite electrode operates at a total of seven positions, staying at the initial position for 3 min, at the second position for 2 min, at the third position for 2.2 min, at the fourth position for 3.6 min, at the fifth position for 1.8 min, at the bottom polishing position for 3.6 min (350 mm away from the bottom of the crucible), and at the finishing stage for 1.8 min.

[0062] Comparative Example 1

[0063] In this embodiment, a quartz crucible having an outer diameter of 26 inches is manufactured by the fixed moving method, and the manufacturing steps are as follows.

[0064] (1) High-purity quartz sand powder is uniformly mixed in a crucible mold, and the quartz raw material is made the same batch raw material as in Example 1.

[0065] (2) The mold is then loaded into the arc furnace.

[0066] (3) The graphite electrode is positioned at -150 mm, the graphite electrode output is controlled to 900 kW, the vacuum level is controlled to -0.093 MPa to -0.1 MPa, and the graphite electrode is blown out every 3 minutes to purge and remove the accumulated volatiles. As the graphite electrode wears, the graphite electrode is adaptively moved downward to maintain the distance from the bottom end of the graphite electrode to the top end of the opening of the mold at -150 mm (310 mm away from the bottom of the crucible).

[0067] (4) After melting, the quartz crucible is cooled and removed from the furnace to complete the production of the quartz crucible blank.

[0068] (5) The manufactured quartz crucible blanks are cut, inspected, cleaned, dried, packaged, and stored in the following order.

[0069] Example 4

[0070] This embodiment provides a method for manufacturing a high-quality quartz crucible with an outer diameter of 24 inches, which adopts the vacuum arc method and the manufacturing steps are as follows:

[0071] (1) High-purity quartz sand powder is mixed uniformly in a crucible mold and molded.

[0072] (2) The mold is then loaded into the arc furnace.

[0073] (3) The position of the open top end face of the mold is set as the zero point, and the movement of the graphite electrode controlled by the PLC program is as shown in Figure 7, in which the quartz crucible is melted. In the figure, the graphite electrode operates at a total of seven positions, staying at the initial position for 2 minutes, the second position for 2 minutes, the third position for 2 minutes, the fourth position for 3 minutes, the fifth position for 1.5 minutes, the bottom polishing position for 3 minutes (340 mm away from the bottom of the crucible), and the finishing stage for 1.5 minutes.

[0074] During the smelting process, the output of the graphite electrode is 800KW, the accuracy at each position is ±5mm, and the degree of vacuum is controlled at -0.093MPa to -0.1Mpa. When smelting at each step is completed, a blowout is performed on the graphite electrode to purge and remove the accumulated volatiles.

[0075] (4) After melting, the quartz crucible is cooled and removed from the furnace to complete the production of the quartz crucible blank.

[0076] (5) The manufactured quartz crucible blanks are cut, inspected, cleaned, dried, packaged, and stored in the following order.

[0077] Example 5

[0078] This embodiment provides a method for manufacturing a high-quality quartz crucible with an outer diameter of 28 inches, using the vacuum arc method, and the manufacturing steps are as follows:

[0079] (1) High-purity quartz sand powder is mixed uniformly in a crucible mold and molded.

[0080] (2) The mold is then loaded into the arc furnace.

[0081] (3) The position of the open top end face of the mold is set as the zero point, and the movement of the graphite electrode controlled by the PLC program is as shown in Figure 8, in which the quartz crucible is melted. In the figure, the graphite electrode operates at a total of seven positions, staying at the initial position for 3.6 min, the second position for 3.6 min, the third position for 3.6 min, the fourth position for 2.4 min, the fifth position for 2.4 min, the bottom polishing position for 6 min (420 mm away from the bottom of the crucible), and the finishing stage for 2.4 min.

[0082] During the smelting process, the output of the graphite electrode is 1050KW, the accuracy at each position is ±5mm, and the degree of vacuum is controlled at -0.093MPa to -0.1Mpa. When smelting at each step is completed, a blowout is performed on the graphite electrode to purge and remove the accumulated volatiles.

[0083] (4) After melting, the quartz crucible is cooled and removed from the furnace to complete the production of the quartz crucible blank.

[0084] (5) The manufactured quartz crucible blanks are cut, inspected, cleaned, dried, packaged, and stored in the following order.

[0085] Example 6

[0086] This embodiment provides a method for manufacturing a high-quality quartz crucible with an outer diameter of 32 inches, using the vacuum arc method, and the manufacturing steps are as follows:

[0087] (1) High-purity quartz sand powder is mixed uniformly in a crucible mold and molded.

[0088] (2) The mold is then loaded into the arc furnace.

[0089] (3) The position of the open top end face of the mold is set as the zero point, and the movement of the graphite electrode controlled by the PLC program is as shown in Figure 9, in which the quartz crucible is melted. In the figure, the graphite electrode operates at a total of seven positions, staying at the initial position for 4 minutes, the second position for 4 minutes, the third position for 4 minutes, the fourth position for 3 minutes, the fifth position for 3 minutes, the bottom polishing position for 9 minutes (500 mm away from the bottom of the crucible), and the finishing stage for 3 minutes.

[0090] During the smelting process, the output of the graphite electrode is 1400KW, the accuracy at each position is ±5mm, and the degree of vacuum is controlled at -0.093MPa to -0.1Mpa. When smelting at each step is completed, a blowout is performed on the graphite electrode to purge and remove the accumulated volatiles.

[0091] (4) After melting, the quartz crucible is cooled and removed from the furnace to complete the production of the quartz crucible blank.

[0092] (5) The manufactured quartz crucible blanks are cut, inspected, cleaned, dried, packaged, and stored in the following order.

[0093] A performance comparison is performed for the quartz crucible manufactured in the embodiment, and when one silicon single crystal is manufactured by the CZ method (requiring 100 hours), the sagging state of the quartz crucible and the content of impurity elements in the transparent layer of the quartz crucible are compared.

[0094] The inner transparent layers 1 of the quartz crucibles of Examples 1-6 and Comparative Example 1 were taken, and the innermost impurity element contents were detected by atomic absorption spectrometry. The results are shown in the table below.

[0095] Impurity element content ppm JPEG2025502519000002.jpg30107

[0096] As can be seen from the above comparison, the surface impurity content of the inner transparent layer 1 of the quartz glass crucible manufactured in Examples 1-6 of the present invention is lower and purer, which reduces the introduction of impurities during the manufacturing process of silicon single crystal by pulling, and ensures the product quality of silicon single crystal. In addition, the quartz glass crucible of Examples 1-6 is detected to have no cracks, no dents, and no bubbles or protruding points on the surface by visual inspection.

[0097] As shown in FIG. 10, after the quartz crucible is used to manufacture silicon single crystals by the CZ method, sagging inevitably occurs due to high-temperature melting. In the manufacturing process, the quartz crucible is placed and positioned in the graphite crucible, and pure silicon melt is contained in the quartz crucible. After one silicon single crystal is produced, the sagging height of the quartz crucible in Example 1 is 3.6 mm, and that of Comparative Example 1 is 8.8 mm. As a result, the quartz crucible manufactured in Comparative Example 1 has poor high-temperature deformation resistance, but the technical solution provided by the present invention can improve this problem.

[0098] Finally, it should be understood that the above embodiments are merely for illustrating the technical solutions of the present invention and are not limited thereto. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art may still modify the technical solutions described in the above embodiments or make equivalent substitutions to some or all of the technical features therein, and such modifications or substitutions do not cause the essence of the corresponding technical solutions to depart from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for manufacturing a high-quality quartz crucible, the method adopting a vacuum arc method, includes the following steps: High-purity quartz sand raw material is placed into a crucible mold, and the quartz sand raw material is uniformly molded on the inner surface of the mold by a molding device to form a crucible initial product. Then, the entire crucible mold is transferred to an arc melting furnace, and a high-temperature arc is emitted by a graphite electrode to melt the quartz sand. Finally, the quartz crucible blank is formed by quenching. In the process of emitting a high-temperature arc using the graphite electrode, the positional movement of the graphite electrode in the height direction and the residence time at each position are controlled to satisfy the following conditions: The position of the end surface of the upper opening of the mold is the zero point, the end of the graphite electrode is marked with + when it is above the zero point, and marked with - when it is below the zero point. During the smelting process, the initial position of the graphite electrode is +0.10-0.30 times the outer diameter of the crucible, and the residence time is ≧2 minutes. Then, the position is sequentially lowered according to the step movement method, and each position is lowered and stayed for a certain time, so that the graphite electrode continuously emits high-temperature arc during the corresponding period of the corresponding position to melt the crucible initial product, and after moving at least three times, it reaches the bottom polishing position, which is the lowest position reached by the graphite electrode and enters the inside of the crucible, and is 300-550 mm away from the bottom of the crucible. At the bottom polishing position, the graphite electrode stays for a certain time to perform high-temperature polishing and volatilization removal at the bottom of the crucible. The graphite electrode is raised to a finishing stage after leaving the bottom grinding position, the finishing stage being +0.05 to 0.07 times the crucible outer diameter, and the upper part of the inner wall of the quartz crucible is high-temperature ground and volatilized away at this position.

2. The manufacturing method according to claim 1, characterized in that during the entire smelting process, the movement of the graphite electrode includes an initial position, a second position, a third position, a fourth position, a fifth position, a bottom grinding position and a finishing stage, in which the graphite electrode descends stepwise from the initial position to the bottom grinding position and stays at each position for a certain period of time.

3. The manufacturing method according to claim 2, characterized in that the residence time of each position of the graphite electrode is 0.4-0.5t, the sum of the residence time of the initial position, the second position and the third position is 0.4-0.5t, the residence time of the fourth position is 0.1-0.2t, the residence time of the fifth position is 0.1t, the residence time of the bottom polishing position is 0.2-0.3t, and the residence time of the finishing stage is 0.1t, and t is the total melting time of the target quartz crucible.

4. The residence time of the graphite electrode at each position of the different sized quartz crucibles is as follows: Quartz crucible with outer diameter of 24 inches: the sum of the residence times at the initial position, the second position and the third position is 0.4t, the residence time at the fourth position is 0.2t, the residence time at the fifth position is 0.1t, the residence time at the bottom polishing position is 0.2t, and the residence time at the finishing stage is 0.1t, and the total melting time is 14-16 minutes; Quartz crucible with an outer diameter of 26 inches: the sum of the residence times in the initial position, the second position, and the third position is 0.45t, the residence time in the fourth position is 0.15t, the residence time in the fifth position is 0.1t, the residence time in the bottom polishing position is 0.2t, the residence time in the finishing stage is 0.1t, and the total melting time is 17-19 minutes; Quartz crucible with an outer diameter of 28 inches: the sum of the residence times at the initial position, the second position, and the third position is 0.45t, the residence time at the fourth position is 0.1t, the residence time at the fifth position is 0.1t, the residence time at the bottom polishing position is 0.25t, the residence time at the finishing stage is 0.1t, and the total melting time is 22-26 minutes; The method according to claim 3, characterized in that: quartz crucible with an outer diameter of 32 inches: the sum of the residence time at the initial position, the second position and the third position is 0.5t, the residence time at the fourth position is 0.1t, the residence time at the fifth position is 0.1t, the residence time at the bottom polishing position is 0.3t, the residence time at the finishing stage is 0.1t, and the total melting time is 28-32 minutes.

5. 2. The manufacturing method according to claim 1, wherein the graphite electrode has a positioning accuracy of ±5 mm at each position during the movement process.

6. The method according to claim 1, characterized in that the degree of vacuum is controlled to -0.093 MPa to -0.1 MPa during the entire smelting process, and the power of the graphite electrodes is 500-2000 kW.

7. The manufacturing method according to claim 6, characterized in that the power of the graphite electrode is 750-850 KW when a quartz crucible with an outer diameter of 24 inches is melted, the power of the graphite electrode is 850-950 KW when a quartz crucible with an outer diameter of 26 inches is melted, the power of the graphite electrode is 1000-1100 KW when a quartz crucible with an outer diameter of 28 inches is melted, and the power of the graphite electrode is 1300-1400 KW when a quartz crucible with an outer diameter of 32 inches is melted.

8. 2. The method according to claim 1, further comprising the steps of: blowing out the graphite electrode when melting at each position is completed during the movement of the graphite electrode; and purging and removing volatiles deposited on the surface of the graphite electrode.

9. 3. The method according to claim 2, wherein the height difference between the bottom polishing position and the fifth position is 100 mm or more.

10. A high-quality quartz crucible, characterized in that it is manufactured using the manufacturing method according to any one of claims 1 to 9.

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