A preparation method of a quartz crucible capable of improving a single crystal pulling bar rate

Abstract

The application discloses a preparation method of a quartz crucible capable of improving the whole rod rate of crystal pulling, relates to the technical field of quartz crucible preparation, and aims to solve the defects of low first whole rod rate, high broken line rate, abnormal bubble expansion and thick crystal layer in the prior art. The method comprises the following steps: laying four layers of quartz sand raw materials from outside to inside in a rotating crucible mold, and accurately controlling the mass ratio and particle size distribution; feeding the blank into a melting furnace; adopting a four-stage coordinated melting process; adjusting the electrode spacing, current and vacuum state in stages; and directly taking out the mold after melting. The application can significantly improve the density of the inner surface of the crucible, reduce micro-bubbles, inhibit abnormal bubble expansion and crystal layer thickening, make the first whole rod rate greater than or equal to 85%, the broken line rate 10.5%-14.5%, the service life 550-680h, and enable 6-8 single crystal rods to be stably pulled, thereby being suitable for large-scale industrial production.

Description

Technical Field

[0001] This invention patent relates to the field of quartz crucible preparation technology, specifically to a method for preparing a quartz crucible that can improve the yield of whole crystal pulling rods. Background Technology

[0002] Quartz crucibles are essential materials for pulling large-diameter single-crystal silicon and developing large-scale integrated circuits. They are used to hold raw materials during the single-crystal silicon pulling process. In the photovoltaic industry, achieving a complete ingot yield on the first pull has always been a challenge. Improving the first-pull ingot yield, reducing the breakage rate, and increasing the yield per unit are the industry's goals.

[0003] In the prior art, CN108059325B discloses a method for preparing a quartz crucible using composite quartz sand and the quartz crucible itself. This method involves separately weighing natural quartz sand and high-purity quartz sand for pre-processing and a single-stage melting process, with a mass ratio of natural quartz sand to high-purity quartz sand of 3:1 to 4:2. The resulting quartz crucible comprises, from the inside out, a composite inner layer and a thin bubble outer layer. The composite inner layer further includes a transparent layer and a bubble composite layer. The main improvement of this prior art lies in reducing the expansion and rupture of bubbles in the bubble composite layer through the composite sand layer structure, thereby extending the service life of the quartz crucible to 190 hours, meeting the requirement of pulling at least 3-4 single crystal rods.

[0004] However, this existing technology still has the following problems: 1. The particle size control of the quartz sand is not precise enough. The high-purity quartz sand only requires that the proportion of particles with a particle size ≤150μm per unit weight be 50%. The design for the proportion of high-purity ultrafine quartz sand is not optimized, and the operation details of layering are not clearly defined. This results in insufficient density of the inner surface of the crucible and a large number of microbubbles. During the first crystal pulling process, the expansion of bubbles can easily cause the wire to break. The first whole rod rate needs to be improved. 2. The material layer structure design only distinguishes between the composite inner layer and the thin bubble outer layer, without setting a dedicated high-purity ultrafine quartz sand inner layer. This fails to fully utilize the advantages of ultrafine powder in reducing microbubbles and improving surface purity. Furthermore, it lacks control over the feeding, scraping, and mold conditions, resulting in poor uniformity of the billet structure and a high risk of wire breakage during crystal pulling. 3. The process control parameters are too broad. During the melting process, no multi-stage collaborative control scheme was designed to match the characteristics of high-purity ultrafine quartz sand. Furthermore, the vacuum stage was not set properly, making it difficult to achieve efficient escape and elimination of microbubbles. During the cooling process, temperature stress can easily cause the crucible to crack or the crystallization layer to thicken, affecting the stability of crystal pulling and the first-round whole bar yield.

[0005] Therefore, in view of the problems of low first-stage whole rod yield and high wire breakage rate in the existing technology, there is an urgent need for a quartz crucible preparation method that improves the whole rod yield of crystal pulling by optimizing the layered laying process, quartz sand preparation and precise melting and molding control. Summary of the Invention

[0006] In view of this, the purpose of this invention is to provide a method for preparing a quartz crucible that can improve the yield of whole crystal rods in crystal pulling. The method provided by this invention can significantly improve the surface density of the crucible, reduce microbubbles, suppress abnormal bubble expansion and crystal thickening, so that the yield of the first and second whole crystal rods is ≥85%, the wire breakage rate is 10.5%-14.5%, the service life is 550-680h, and it can stably pull 6-8 single crystal rods, which is suitable for large-scale industrial production.

[0007] The present invention discloses a method for preparing a quartz crucible that can improve the yield of whole crystal pulling rods, which includes the following steps: (1) Raw material preparation: In the rotating crucible mold, from the outside to the inside, the outer layer of quartz sand, the middle layer of quartz sand, the first inner layer of high-purity quartz sand, and the second inner layer of high-purity ultrafine quartz sand are prepared in sequence. The particle size distribution of the second inner layer of high-purity ultrafine quartz sand satisfies the following: Second inner layer: <50 mesh 0.00%, 50 mesh-70 mesh 0.00%, 70 mesh-80 mesh 0.00%, 80 mesh-100 mesh 0.00%, 100 mesh-120 mesh 0. 00%, 120 mesh-140 mesh 2.00%-2.40%, 140 mesh-200 mesh 43.50%-44.00%, >200 mesh 54.00%-54.50%; During the laying process, materials are simultaneously added and scraped manually to ensure uniform thickness of each layer and obtain a quartz sand blank. (2) Melting and molding: The crucible mold containing the quartz sand blank from step (1) is transported to the melting furnace and melted and shaped in four stages, specifically: First stage: Adjust the position of the three graphite electrodes so that the distance between the lower end of each graphite electrode and the upper opening of the crucible mold is 380-420mm. Then, apply a current of 5400-5600A for 35-45s and simultaneously evacuate the vacuum. The wide electrode spacing combined with the strong current rapidly melts the raw materials of each layer, and the simultaneous vacuum evacuation efficiently removes a large number of air bubbles in the early stage, laying a bubble-free foundation for subsequent dense molding.

[0008] Second stage: Maintain the distance between the graphite electrode and the top of the crucible mold at 380-420mm, change the current to 2000-2200A, and then increase it to 2700-3000A at a rate of 40-60A every 1.5-2.5 minutes, while continuously evacuating the vacuum; by gradually increasing the medium current, the raw material is kept in a state of near melting but not melting, and a uniform and dense transparent inner surface layer is slowly formed. At the same time, the vacuum is continuously evacuated to remove the micro-bubbles generated during the molding process and to avoid bubble encapsulation.

[0009] Third stage: Stop vacuuming, then adjust the distance between the lower end of the graphite electrode and the upper opening of the crucible mold to 180-220mm, and then restore the current of 5400-5600A and maintain it for 160-200s; use the narrow electrode spacing to enhance the arc heating intensity, promote the natural aggregation and escape of residual microbubbles, and at the same time stop vacuuming to avoid turbulent flow of the melt and ensure the structural integrity of the formed transparent layer.

[0010] Fourth stage: Maintain the distance between the graphite electrode and the upper opening of the crucible mold at 180-220mm, change the current to 2900-3100A, maintain it for 200-300s, and then stop the power supply; achieve precise shaping of the crucible through a stable medium-low current, ensure dimensional accuracy and structural stability, and provide conditions for subsequent direct demolding.

[0011] (3) Demolding: After the melting and molding in step (2) is completed, the furnace is opened directly, and the quartz crucible is taken out from the crucible mold to complete the preparation.

[0012] Furthermore, in step (1), the rotation speed of the crucible mold is 60-61 r / min.

[0013] Furthermore, in step (1), the particle size distribution of the raw materials in the outer layer, middle layer, and first inner layer satisfies: Outer layer: <60 mesh 10-40%, 60-80 mesh 20-40%, 80-100 mesh 10-20%, 100-120 mesh 10-20%, 120-140 mesh <10%, 140-200 mesh <5%, >200 mesh <1%; Middle layer: <60 mesh <25%, 60-80 mesh 10-30%, 80-100 mesh 10-25%, 100-120 mesh 10-20%, 120-140 mesh 5-15%, 140-200 mesh 5-15%, >200 mesh <10%; First inner layer: <50 mesh 0.00%, 50 mesh-70 mesh 0.00%, 70 mesh-80 mesh 0.00%, 80 mesh-100 mesh 0.00%, 100 mesh-120 mesh 9.50%-1 0.00%, 120 mesh-140 mesh 22.00%-23.00%, 140 mesh-200 mesh 46.50%-47.00%, >200 mesh 20.50%-21.50%.

[0014] Furthermore, the total impurity content of the outer and middle layers of quartz sand is ≤20ppm.

[0015] Furthermore, the total impurity content of the first inner layer of high-purity quartz sand and the second inner layer of high-purity ultrafine quartz sand is ≤12ppm.

[0016] Furthermore, in step (2), the vacuum conditions are: vacuum degree of -0.09MPa to -0.07MPa and frequency of 65-75Hz.

[0017] Advantages of this invention: 1. This invention discloses a method for preparing a quartz crucible that can improve the yield of whole crystal pulling rods. Through precise particle size distribution design, its density is significantly improved: a second inner layer of high-purity ultrafine quartz sand is specially designed, with the proportion of the preceding particle size range (<50 mesh to 100-120 mesh) fixed at 0.00%, and the proportion of ultrafine powder >200 mesh reaching 54.00%-54.50%. Combined with the precise particle size design of the first inner layer, outer layer, and middle layer, this solves the problem of inaccurate particle size control in existing technologies, resulting in a crucible inner surface density ≥2.2 g / cm³. 3 The number of microbubbles in the straight wall section is reduced to 0-3 (detection depth 0.5mm), while the number of microbubbles in the R-corner section is 6-13 (detection depth 0.5mm).

[0018] 2. This invention discloses a method for preparing a quartz crucible that can improve the yield of whole crystal pulling rods. Through material layer structure optimization, it has strong functional synergy: it adopts a four-layer structure design, with the outer layer providing structural support, the middle layer balancing stress, the first inner layer laying the foundation for the transparent layer, and the second inner layer leveraging the advantages of ultrafine powder to reduce foaming. At the same time, through manual feeding and scraping and mold rotation control, the uniformity of the billet structure is greatly improved, and the risk of wire breakage during crystal pulling is reduced. 3. This invention discloses a method for preparing a quartz crucible that can improve the yield of whole crystal pulling rods. It achieves efficient bubble removal through coordinated control of the melting process: the electrode spacing is adjusted in stages and the role of each stage is clarified. Combined with differentiated vacuum control (vacuuming in the first two stages and stopping vacuuming in the last two stages) and precise current adjustment, it can not only achieve efficient removal of a large number of bubbles in the early stage, but also avoid bubble encapsulation or structural deformation caused by vacuum fluctuations in the later stages. The microbubble removal rate is improved by more than 50% compared with the prior art. 4. This invention discloses a method for preparing a quartz crucible that can improve the yield of crystal pulling rods, which achieves a leap in crystal pulling performance and optimizes production efficiency: the yield of the first and second crystal pulling rods is increased to ≥85%, which is more than 30% higher than the prior art; at the same time, the service life and the number of crystal pulling rods are significantly improved (service life reaches 550-680h, and 6-8 single crystal rods can be pulled stably), which is suitable for the needs of large-scale industrial production. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 Photograph of the cross-sectional structure of the quartz crucible fragment after use, prepared in Example 1 of this invention.

[0021] Figure 2 Photograph of the cross-sectional structure of the quartz crucible fragment after use, prepared for Comparative Example 2. Detailed Implementation

[0022] The present invention will be further described in detail below through embodiments.

[0023] Example 1 (1) Raw material laying: Start the crucible mold, adjust the rotation speed to 60 r / min, and lay the raw materials from the outside to the inside according to the mass ratio of outer layer: middle layer: first inner layer: second inner layer = 4:2:2:2; Outer layer quartz sand (impurity content 18ppm): <60 mesh 30%, 60-80 mesh 30%, 80-100 mesh 15%, 100-120 mesh 15%, 120-140 mesh 8%, 140-200 mesh 4%, >200 mesh 0.5%; Intermediate-layer quartz sand (impurity content 16ppm): <60 mesh 22%, 60-80 mesh 25%, 80-100 mesh 20%, 100-120 mesh 15%, 120-140 mesh 10%, 140-200 mesh 10%, >200 mesh 8%; The first inner layer of high-purity quartz sand (impurity content 10ppm): <50 mesh 0.00%, 50 mesh-70 mesh 0.00%, 70 mesh-80 mesh 0.00%, 80 mesh-100 mesh 0.00%, 100 mesh-120 mesh 9.70%, 120 mesh-140 mesh 22.50%, 140 mesh-200 mesh 46.80%, >200 mesh 21.00%; The second inner layer is high-purity ultrafine quartz sand (impurity content 8ppm): <50 mesh 0.00%, 50-70 mesh 0.00%, 70-80 mesh 0.00%, 80-100 mesh 0.00%, 100-120 mesh 0.00%, 120-140 mesh 2.20%, 140-200 mesh 43.70%, >200 mesh 54.10%; During the laying process, materials are simultaneously added and scraped manually to ensure uniform thickness of each layer and obtain a quartz sand blank. (2) Melting and molding: The mold containing the quartz sand blank is conveyed to the melting furnace; First stage: Adjust the distance between the electrode and the top of the mold to 400mm, apply a current of 5500A and maintain it for 40s, and simultaneously evacuate the vacuum (vacuum degree -0.08MPa, frequency 70Hz). Second stage: Maintain an electrode spacing of 400mm, an initial current of 2100A, increase the current by 50A every 2 minutes until it reaches 2800A, and continue to pump vacuum (vacuum degree -0.08MPa, frequency 70Hz). Third stage: Stop vacuuming, adjust the electrode spacing to 200mm, and apply a current of 5500A for 180s; Fourth stage: Maintain an electrode spacing of 200mm, apply a current of 3000A for 250s, then stop applying the current; (3) Demolding: After melting is complete, the furnace is opened directly, and the quartz crucible is removed from the mold to obtain the finished product.

[0024] Example 2 (1) Raw material laying: Start the crucible mold and adjust the rotation speed to 60 r / min. Lay out each layer of raw material from the outside to the inside according to the mass ratio of outer layer: middle layer: first inner layer: second inner layer = 3.5: 1.5: 1.5: 1.5. Outer layer quartz sand (impurity content 19ppm): <60 mesh 20%, 60-80 mesh 30%, 80-100 mesh 15%, 100-120 mesh 15%, 120-140 mesh 8%, 140-200 mesh 4%, >200 mesh 0.5%; Intermediate layer quartz sand (impurity content 17ppm): <60 mesh 20%, 60-80 mesh 20%, 80-100 mesh 15%, 100-120 mesh 15%, 120-140 mesh 8%, 140-200 mesh 8%, >200 mesh 6%; First inner layer high-purity quartz sand (impurity content 11ppm): <50 mesh 0.00%, 50-70 mesh 0.00%, 70-80 mesh 0.00%, 80-100 mesh 0.00%, 100-120 mesh 9.50%, 120-140 mesh 22.00%, 140-200 mesh 46.50%, >200 mesh 20.50%; The second inner layer is high-purity ultrafine quartz sand (impurity content 9ppm): <50 mesh 0.00%, 50-70 mesh 0.00%, 70-80 mesh 0.00%, 80-100 mesh 0.00%, 100-120 mesh 0.00%, 120-140 mesh 2.00%, 140-200 mesh 43.50%, >200 mesh 54.00%; During the laying process, materials are simultaneously added and scraped manually to ensure uniform thickness of each layer and obtain a quartz sand blank. (2) Melting and molding: The mold containing the blank is conveyed to the melting furnace; First stage: Adjust the distance between the electrode and the top of the mold to 380mm, apply a current of 5400A and hold for 35s, and simultaneously evacuate (vacuum degree -0.09MPa, frequency 65Hz). Second stage: Maintain an electrode spacing of 380mm, an initial current of 2000A, increase the current by 40A every 1.5min, until it reaches 2700A, and continue to pump vacuum (vacuum degree -0.09MPa, frequency 65Hz). Third stage: Stop vacuuming, adjust the electrode spacing to 180mm, and apply a current of 5400A for 160s; Fourth stage: Maintain an electrode spacing of 180mm, apply a current of 2900A for 200s, then stop applying the current; (3) Demolding: After melting is complete, the furnace is opened directly, and the quartz crucible is removed from the mold to obtain the finished product.

[0025] Example 3 (1) Raw material laying: Start the crucible mold and adjust the rotation speed to 61 r / min. Lay out each layer of raw material from the outside to the inside according to the mass ratio of outer layer: middle layer: first inner layer: second inner layer = 4.5: 2.5: 2.5: 2.5. Outer layer quartz sand (impurity content 15ppm): <60 mesh 40%, 60-80 mesh 20%, 80-100 mesh 10%, 100-120 mesh 10%, 120-140 mesh 8%, 140-200 mesh 4%, >200 mesh 0.5%; Intermediate layer quartz sand (impurity content 14ppm): <60 mesh 24%, 60-80 mesh 30%, 80-100 mesh 10%, 100-120 mesh 10%, 120-140 mesh 15%, 140-200 mesh 15%, >200 mesh 9%; The first inner layer of high-purity quartz sand (impurity content 10ppm): <50 mesh 0.00%, 50 mesh-70 mesh 0.00%, 70 mesh-80 mesh 0.00%, 80 mesh-100 mesh 0.00%, 100 mesh-120 mesh 10.00%, 120 mesh-140 mesh 23.00%, 140 mesh-200 mesh 47.00%, >200 mesh 21.50%; The second inner layer is high-purity ultrafine quartz sand (impurity content 7ppm): <50 mesh 0.00%, 50-70 mesh 0.00%, 70-80 mesh 0.00%, 80-100 mesh 0.00%, 100-120 mesh 0.00%, 120-140 mesh 2.40%, 140-200 mesh 44.00%, >200 mesh 54.50%; During the laying process, materials are simultaneously added and scraped manually to ensure uniform thickness of each layer and obtain a quartz sand blank. (2) Melting and molding: The mold containing the blank is conveyed to the melting furnace; First stage: Adjust the distance between the electrode and the top of the mold to 420mm, apply a current of 5600A and hold for 45s, and simultaneously evacuate (vacuum degree -0.07MPa, frequency 75Hz). Second stage: Maintain an electrode spacing of 420mm, an initial current of 2200A, increase the current by 60A every 2.5min, up to 3000A, and continue to pump vacuum (vacuum degree -0.07MPa, frequency 75Hz). Third stage: Stop vacuuming, adjust the electrode spacing to 220mm, and apply a current of 5600A for 200s; Fourth stage: Maintain an electrode spacing of 220mm, apply a current of 3100A for 300s, then stop applying the current; (3) Demolding: After melting is complete, the furnace is opened directly, and the quartz crucible is removed from the mold to obtain the finished product.

[0026] Comparative Example 1 Quartz crucibles were prepared according to the method disclosed in CN108059325B: natural quartz sand and high-purity quartz sand (mass ratio 3:1) were weighed separately, and a quartz crucible with a composite inner layer and a thin bubble outer layer structure was obtained through prefabrication and one-time melting; the high-purity quartz sand was only required to have a particle size ≤150μm of 50%, and no special high-purity ultrafine powder inner layer was set. The electrode spacing and vacuum parameters were not adjusted in stages during the melting process.

[0027] Comparative Example 2 The preparation method is basically the same as that in Example 1 of this invention. The core difference is that: the second inner layer of high-purity ultrafine quartz sand set in this invention is not used. Only a three-layer material structure of outer layer, middle layer and inner layer is set. The mass ratio of the three layers of raw materials is outer layer: middle layer: inner layer = 4: 2: 4. The electrode spacing and vacuum parameters are not adjusted in stages during the melting process.

[0028] experiment: 1. Experimental Samples Quartz crucibles prepared in Examples 1-3 of the present invention were selected, and Comparative Example 1 and Comparative Example 2 were selected as control samples, with 3 samples in each group.

[0029] 2. Testing Items and Methods (1) Basic performance testing: Microbubble count: The number of microbubbles was measured using a microbubble detector, set to the number of gas and liquid per 15.3 square millimeters; the detection depth was 0.5 mm, and the number of microbubbles in the straight wall and round corner sections were counted separately. Density: The density of the transparent layer on the inner surface was measured using the water displacement method; Maximum bubble diameter: The maximum bubble diameter was observed and measured using a microscope; (2) Crystal pulling performance test: Crystal pulling experiments were conducted under the same crystal pulling equipment and process conditions (silicon purity, crystal pulling temperature, pulling speed, etc. were consistent), and the results were recorded. First secondary crystal pulling: number of breakages, overall ingot finishing conditions, and calculation of the first secondary ingot yield; Service life: Record the duration from the start of crystal pulling to when the crucible can no longer be used; Number of crystal rods: The number of single crystal rods successfully pulled during the service life; Wire breakage rate: The ratio of the number of wire breakage failures during crystal pulling to the total number of crystal pulling operations is recorded and the wire breakage rate is calculated. Wire breakage failure refers to the situation where the connection between the single crystal rod and the silicon melt breaks during crystal pulling, resulting in the interruption of crystal pulling. The lower the wire breakage rate, the better the stability of crucible crystal pulling.

[0030] After crystal pulling, the quartz crucible fragments from Comparative Example 2 and Example 1 were photographed and analyzed to obtain... Figure 1 and Figure 2 .

[0031] 3. Experimental Results (1) Basic performance test results Table 1 Basic performance test results

[0032] As can be seen from Table 1, the quartz crucibles prepared in Examples 1-3 of this invention all have an inner surface density ≥ 2.2 g / cm³. 3 The number of microbubbles in the straight wall and R-corner areas was significantly less than that in Comparative Example 1 and Comparative Example 2, and the maximum bubble diameter was also smaller. This indicates that the present invention effectively improves the density of the inner surface of the crucible and reduces microbubbles through precise particle size design, four-layer material structure and synergistic melting process. Comparative Example 2 had the worst density and foam reduction effect because it did not have a second inner layer of high-purity ultrafine quartz sand, which further verifies the necessity of setting a second inner layer.

[0033] (2) Crystal pulling performance test results Table 2 Crystal pulling performance test results

[0034] As shown in Table 2, the quartz crucibles of Examples 1-3 of this invention have a first-round whole rod rate of ≥85%, a service life of 550-680 hours, and a breakage rate of only 10.5%-14.5%. All crystal pulling performances far exceed those of Comparative Examples 1 and 2. The breakage rate is particularly outstanding. The breakage rate of the examples is reduced by more than 65% compared with Comparative Example 1 (42.0%) and by more than 75% compared with Comparative Example 2 (58.0%). This is mainly due to the precise particle size control, four-layer material structure, and synergistic melting process of this invention, which effectively reduces the number of microbubbles in the crucible and improves the internal surface density, thereby reducing the breakage failure caused by bubble expansion during crystal pulling. Comparative Example 2, lacking a second inner layer of high-purity ultrafine quartz sand, exhibited the highest breakage rate, the lowest first-growth ingot rate, the least service life, and the fewest crystal rods. This fully demonstrates that the four-layer material structure, precise particle size control, and synergistic melting process of the present invention can effectively improve crystal pulling performance and solve the pain points of low first-growth ingot rate and high breakage rate in existing technologies. Furthermore, within the service life of the quartz crucibles in Examples 1-3 of the present invention, 6-8 single crystal rods can be stably pulled, which is about 50% higher than that of Comparative Example 1, fully verifying the superiority of the method of the present invention.

[0035] from Figure 1 and Figure 2 As can be seen, after high-temperature service, the crucible of Example 1 with added high-purity ultrafine quartz sand only underwent uniform and controllable normal expansion of the bubble layer without breaking through to the surface. The absolutely transparent layer was still intact, and the growth of the inner crystallization layer was significantly suppressed and the thickness was relatively thin. In contrast, the crucible of Comparative Example 2 without added high-purity ultrafine quartz sand showed abnormal expansion of the bubble layer to the surface, almost complete loss of the absolutely transparent layer, and significant thickening of the inner crystallization layer, indicating structural deterioration. This comparison directly proves that high-purity ultrafine quartz sand can effectively suppress abnormal bubble expansion of quartz crucibles at high temperatures, delay the loss of the transparent layer, and reduce the growth of inner crystallization, thereby significantly improving the high-temperature structural stability and service reliability of the crucible.

[0036] The above are preferred embodiments of the present invention. For those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a quartz crucible that can improve the yield of whole crystal pulling rods, characterized in that, It includes the following steps: (1) Raw material preparation: In the rotating crucible mold, from the outside to the inside, the outer layer of quartz sand, the middle layer of quartz sand, the first inner layer of high-purity quartz sand, and the second inner layer of high-purity ultrafine quartz sand are prepared in sequence. The particle size distribution of the second inner layer of high-purity ultrafine quartz sand satisfies the following: Second inner layer: <50 mesh 0.00%, 50 mesh-70 mesh 0.00%, 70 mesh-80 mesh 0.00%, 80 mesh-100 mesh 0.00%, 100 mesh-120 mesh 0. 00%, 120 mesh-140 mesh 2.00%-2.40%, 140 mesh-200 mesh 43.50%-44.00%, >200 mesh 54.00%-54.50%; During the laying process, materials are simultaneously added and scraped manually to ensure uniform thickness of each layer and obtain a quartz sand blank. (2) Melting and molding: The crucible mold containing the quartz sand blank from step (1) is transported to the melting furnace and melted and shaped in four stages, specifically: First stage: Adjust the position of the three graphite electrodes so that the distance between the lower end of each graphite electrode and the upper opening of the crucible mold is 380-420mm. Then, apply a current of 5400-5600A and hold it for 35-45s while simultaneously drawing a vacuum. Second stage: Maintain the distance between the graphite electrode and the top of the crucible mold at 380-420mm, change the current to 2000-2200A, and then increase it to 2700-3000A at a rate of 40-60A every 1.5-2.5min, while continuously evacuating the vacuum. Third stage: Stop vacuuming, then adjust the distance between the lower end of the graphite electrode and the upper opening of the crucible mold to 180-220mm, and then restore the current of 5400-5600A and hold it for 160-200s. Fourth stage: Maintain the distance between the graphite electrode and the upper opening of the crucible mold at 180-220mm, change the current to 2900-3100A, maintain it for 200-300s, and then stop the power supply; (3) Demolding: After the melting and molding in step (2) is completed, the furnace is opened directly, and the quartz crucible is taken out from the crucible mold to complete the preparation.

2. The method for preparing a quartz crucible that can improve the yield of whole crystal pulling rods according to claim 1, characterized in that, In step (1), the rotation speed of the crucible mold is 60-61 r / min.

3. The method for preparing a quartz crucible that can improve the yield of whole crystal pulling rods according to claim 1, characterized in that, In step (1), the particle size distribution of the raw materials in the outer layer, middle layer, and first inner layer satisfies: Outer layer: <60 mesh 10-40%, 60-80 mesh 20-40%, 80-100 mesh 10-20%, 100-120 mesh 10-20%, 120-140 mesh <10%, 140-200 mesh <5%, >200 mesh <1%; Middle layer: <60 mesh <25%, 60-80 mesh 10-30%, 80-100 mesh 10-25%, 100-120 mesh 10-20%, 120-140 mesh 5-15%, 140-200 mesh 5-15%, >200 mesh <10%; First inner layer: <50 mesh 0.00%, 50 mesh-70 mesh 0.00%, 70 mesh-80 mesh 0.00%, 80 mesh-100 mesh 0.00%, 100 mesh-120 mesh 9.50%-1 0.00%, 120 mesh-140 mesh 22.00%-23.00%, 140 mesh-200 mesh 46.50%-47.00%, >200 mesh 20.50%-21.50%.

4. The method for preparing a quartz crucible that can improve the yield of whole crystal pulling rods according to claim 3, characterized in that, The total impurity content of the outer and middle layers of quartz sand is ≤20ppm.

5. The method for preparing a quartz crucible that can improve the yield of whole crystal pulling rods according to claim 3, characterized in that, The total impurity content of the first inner layer of high-purity quartz sand and the second inner layer of high-purity ultrafine quartz sand is ≤12ppm.

6. The method for preparing a quartz crucible that can improve the yield of whole crystal pulling rods according to claim 1, characterized in that, In step (2), the vacuum conditions are: vacuum degree of -0.09MPa to -0.07MPa and frequency of 65-75Hz.

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