Combined crucible for continuous crystal pulling and preparation method thereof

Abstract

The invention discloses a combined crucible for continuous crystal pulling and a preparation method thereof, the combined crucible comprises a first crucible and a second crucible, the second crucible is arranged in the first crucible, the second crucible and the first crucible form a melt interlayer, the side wall of the second crucible is provided with at least one first through hole, and the second crucible is communicated with the first crucible. According to the combined crucible for continuous crystal pulling, the two crucible sleeves are adopted to form a communicating structure, and the problems that in the existing crystal pulling process, the liquid level is lowered, efficiency is low, and the influence of granular silicon on silicon liquid in the second crucible is large are solved.

Description

Technical Field

[0001] The present invention relates to the technical field of crucibles, and more specifically to a combined crucible for continuous crystal pulling of single crystal silicon and a preparation method thereof. Background Art

[0002] The current technology for preparing single crystal silicon is mainly divided into two types: floating zone melting method and Czochralski method. Czochralski method is relatively cheaper, has a faster growth rate, and is more suitable for pulling large-sized single crystal silicon rods. Currently, single crystal silicon is mainly produced by Czochralski method. CZ is a common method for growing crystals from melts. It requires the crystals to be uniformly eutectic. Its main advantage is that it is an intuitive technology that can grow large single crystals without dislocations in a short time.

[0003] Disadvantages: 1. Generally, a quartz crucible is used as a container, which leads to varying degrees of contamination of the melt; 2. When the melt contains volatile substances, it is difficult to control the composition; 3. Whether it is the batch pulling method or the RCZ method, the silicon melt in the crucible will become less as the single crystal silicon rod is pulled, causing the liquid level to drop, resulting in the instability of the thermodynamic environment in the pulling environment, which is easy to cause the properties of the pulled single silicon crystal rod to be uneven. . As the growth process proceeds, the melt level in the crucible will continue to drop, and the inner wall of the crucible will gradually be exposed. Since the temperature of the crucible wall is very high, it has a great impact on the temperature field in the crystal and melt, and even causes interface flipping. 4. When a drawn crystal is cooled in the gate, the silicon raw material for the next drawing is added to the remaining silicon melt in the crucible through the feeding tube. Therefore, the addition of silicon material is completed when the crystal is cooled. However, before the next drawing, it is necessary to wait for the single silicon crystal rod to be cooled and removed in the gate chamber, resulting in low efficiency of industrial production of the RCZ method.

[0004] Single crystal silicon wafers are classified into 6-inch, 8-inch, 12-inch and 18-inch sizes according to their diameters. The larger the diameter of the wafer, the higher the requirements for materials and technology. Existing single crystal silicon wafers are generally pulled using quartz crucibles, but quartz crucibles have a short service life, and quartz will react with silicon liquid, causing oxygen to be doped into the silicon wafer. If silicon nitride is used, the maximum diameter of the high-strength silicon nitride crucible prepared by the existing isostatic pressing method is about 12 inches, which makes it difficult to prepare large-sized silicon wafers. Summary of the invention

[0005] In view of the above shortcomings of the existing Czochralski method for producing single crystal silicon, the present invention provides a combined crucible for continuous pulling of single crystal silicon and a preparation method thereof, which solves the problems of liquid level drop, uneven temperature and low efficiency by combining the crucibles.

[0006] In order to achieve the above-mentioned object of the invention, the present invention adopts the following technical scheme:

[0007] A combined crucible for continuous crystal pulling comprises a first crucible and a second crucible. The second crucible is placed in the first crucible to form a molten material interlayer with the first crucible. The side wall of the second crucible is provided with at least one first through hole to connect the second crucible with the first crucible.

[0008] Further technology of the present invention:

[0009] Preferably, the number of the first through holes of the second crucible is even and they are arranged opposite to each other.

[0010] Preferably, a mixer is provided in the second crucible.

[0011] Preferably, the mixer has a cylindrical structure, a second through hole is provided on the surface, and the mixer port is connected to the first through hole on the side wall of the second crucible.

[0012] Preferably, the first crucible comprises a quartz outer crucible and a silicon nitride inner crucible embedded in the quartz outer crucible, and the silicon nitride inner crucible is formed by splicing a plurality of plate-shaped first silicon nitride components.

[0013] Preferably, the second crucible comprises one of a monolithic silicon nitride crucible and a combined silicon nitride crucible.

[0014] Preferably, the combined silicon nitride crucible comprises:

[0015] Upper body: formed by a plurality of plate-shaped second silicon nitride components surrounded by a clamping piece;

[0016] Lower body: the upper end has a card slot;

[0017] The lower end of the upper body is inserted into the slot at the upper end of the lower body, and the first through hole is arranged on the lower body.

[0018] Preferably, a separator is provided between the first crucible and the second crucible.

[0019] Preferably, a plurality of third through holes are provided on the surface of the isolator.

[0020] Preferably, the isolator is in a cylindrical shape or a trumpet shape.

[0021] The present invention also provides a method for preparing a combined crucible for continuous crystal pulling, comprising the following steps:

[0022] Step S1, mixing silicon powder, sintering aid and binder solution into a uniform slurry, forming a green body by cold isostatic pressing, and debinding the green body;

[0023] Step S2, after the binder removal is completed, the green body is sintered in a sintering furnace to obtain a silicon nitride component with a dense structure;

[0024] Step S3, assembling a complete silicon nitride crucible from a plurality of silicon nitride components, and clamping a fused quartz crucible layer onto the surface of the silicon nitride crucible under negative pressure to obtain a first crucible;

[0025] Step S4: placing the second crucible in the first crucible to form a molten material sandwich with the first crucible, and providing at least one first through hole on the side wall of the second crucible to connect the second crucible with the first crucible.

[0026] In a further technical solution, the average particle size of the silicon powder is 0.5-1.5 μm. The preparation cost of silicon powder with a smaller particle size is higher, and silicon powder with a larger particle size is more difficult to be completely nitrided, so the particle size of the silicon powder needs to be controlled within an appropriate range.

[0027] As a preferred technical solution, the silicon powder is selected from two specifications of silicon powder with average particle sizes of 0.6-0.7 μm and 1.3-1.4 μm, and is combined in a mass ratio of 1:(2-3), so that the obtained composite crucible has a longer service life.

[0028] In a further technical solution, the binder solution is a solution prepared by dissolving a binder in an organic solvent, and the binder content is 1 to 3 wt%.

[0029] In a further technical solution, the organic solvent includes but is not limited to at least one of ethanol, methanol and acetone, and any organic solvent that can dissolve the binder and has low toxicity can be used.

[0030] In a further technical solution, the binder includes but is not limited to at least one of polyvinyl butyral (PVB) and polyethylene glycol (PEG). An organic binder or an inorganic binder can be used. When an inorganic binder is used, water is used instead of an organic solvent to prepare the slurry.

[0031] In a further technical solution, the sintering aid includes but is not limited to at least one of yttrium oxide, aluminum oxide, lanthanum oxide, and zirconium oxide.

[0032] In a further technical solution, the amount of the sintering aid is 0-5wt% of the total amount of silicon powder and the sintering aid, that is, the sintering aid may be added or not.

[0033] In a further technical solution, the solid content of the slurry is 40-55%. If the solid content is too small or too large, the viscosity of the slurry will be different, and the size of the particles obtained by granulation will also be different.

[0034] In a further technical solution, the slurry is spray granulated before cold isostatic pressing. The granules obtained by spray granulation are conducive to subsequent molding, and the solvent can also be removed during the granulation process.

[0035] In a further technical solution, the pressure of the cold isostatic pressing is 180-250 MPa. The structural density of the silicon nitride blank is improved by the cold isostatic pressing process.

[0036] In a further technical solution, the debinding is vacuum debinding at 400-600° C. The function of debinding is to decompose and remove organic matter, and vacuum debinding avoids oxidation of silicon.

[0037] In a further technical solution, the sintering includes pre-nitriding sintering, complete nitriding sintering and densification sintering; preferably, the pre-nitriding sintering is carried out in a nitrogen and / or ammonia atmosphere, at a temperature of 1200-1300°C, for 4-8 hours, and at a pressure of 1 atmosphere; the complete nitriding sintering is carried out in a nitrogen and / or ammonia atmosphere, first at a temperature of 1300-1400°C and a pressure of 1 atmosphere for 24-36 hours, and then at a temperature of 1400-1480°C and a pressure of 1 atmosphere for 12-24 hours; the densification sintering is carried out in a nitrogen atmosphere, at a temperature of 1650-1800°C, for 1-4 hours, and at a pressure of 5-10 MPa.

[0038] In the present invention, the size of the silicon nitride crucible assembly may change during the nitriding process using silicon powder as the raw material. Therefore, in order to improve the precision of the silicon nitride crucible assembly, the silicon nitride crucible assembly may be machined (such as turning, milling, planing, and grinding) between the pre-nitriding sintering and the complete nitriding sintering. By adopting step-by-step nitriding, the size of the blank changes little during the nitriding process, and the hardness of the blank after pre-nitriding is small, which makes it easier to machine.

[0039] In the present invention, the silicon nitride crucible assembly can be finely processed and then assembled into a complete silicon nitride crucible, further improving the dimensional accuracy and reducing the gap. The reason for the two-step processing is that the hardness of the blank after pre-nitridation is relatively small and easy to process. At this time, rough processing is performed first, and fine processing is performed after complete nitridation.

[0040] In a further technical solution, the clamping temperature of the fused quartz crucible layer is preferably 1650-1750°C.

[0041] As a preferred technical solution, the specific operation of the tightening is to place the silicon nitride crucible in a quartz crucible, and the quartz crucible generates compressive stress on the silicon nitride crucible after being heated, thereby tightening the inner silicon nitride crucible.

[0042] As a preferred technical solution, the specific operation of the tightening is to turn the silicon nitride crucible upside down, heat it to soften the quartz, and the molten quartz is coated on the outer wall of the silicon nitride crucible under the action of gravity.

[0043] The beneficial effects of the present invention are:

[0044] (1) The combined crucible for continuous crystal pulling of the present invention uses two crucibles to form a connected structure, which solves the problems of liquid level drop, low efficiency and great influence of granular silicon on silicon liquid in the second crucible in the existing crystal pulling process.

[0045] (2) The combined crucible for continuous crystal pulling of the present invention solves the problem of large temperature fluctuation of silicon liquid in the second crucible by providing an isolator and a mixer.

[0046] (3) The combined crucible for continuous crystal pulling of the present invention adopts a combined silicon nitride crucible, which solves the problem that the existing high-strength silicon nitride crucible made by isostatic pressing is difficult to prepare in larger size and the oxygen content in the silicon wafer is high.

[0047] (4) A first crucible is prepared by negative pressure, and the inner silicon nitride crucible and the outer quartz crucible are tightly fitted to avoid pores. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] Figure 1 It is a schematic diagram of the structure of a combined crucible for continuous crystal pulling disclosed in the present invention;

[0049] Figure 2 It is a schematic diagram of the first crucible structure disclosed in the present invention;

[0050] Figure 3 It is a schematic diagram of the structure of the silicon nitride inner crucible disclosed in the present invention;

[0051] Figure 4 It is a schematic diagram of the structure of the second crucible disclosed in the present invention;

[0052] Figure 5 It is a schematic diagram of the lower split structure of the second crucible disclosed in the present invention;

[0053] Figure 6 This is a schematic diagram of the structure of the second silicon nitride component disclosed in the present invention;

[0054] Figure 7 It is a schematic diagram of the structure of a combined crucible for continuous crystal pulling according to Example 4 disclosed in the present invention;

[0055] Figure 8 It is a schematic diagram of the structure of a cylindrical isolator according to Embodiment 4 disclosed in the present invention;

[0056] Fig. 9 It is a schematic diagram of the structure of a combined crucible for continuous crystal pulling according to Example 5 disclosed in the present invention;

[0057] Fig.10 It is a schematic diagram of the structure of the horn-shaped isolator of Example 5 disclosed in the present invention;

[0058] Fig.11This is a schematic diagram of the structure of the combined crucible for continuous crystal pulling according to Example 6 disclosed in the present invention;.

[0059] Fig.12 This is a schematic diagram of the structure of the mixer of Example 6 disclosed in the present invention;

[0060] Fig.13 This is a schematic diagram of the first crucible negative pressure molding disclosed in the present invention.

[0061] Explanation of the symbols in the schematic diagram:

[0062] 1. First crucible; 11. Quartz outer crucible; 12. Silicon nitride inner crucible; 13. Support portion; 14. Heating furnace; 121. First silicon nitride component; 2. Second crucible; 21. Upper split body; 211. Second silicon nitride component; 212. Connector; 22. Lower split body; 221. Slot; 3. First through hole; 4. Mixer; 41. Second through hole; 5. Cylindrical isolator; 51. Third through hole; 6. Trumpet-shaped isolator. DETAILED DESCRIPTION

[0063] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be further described in detail below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention but not all. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0064] Example 1: Figure 1-6 As shown, a combined crucible for continuous crystal pulling includes a first crucible 1 and a second crucible 2. The second crucible 2 is placed in the first crucible 1 to form a molten material interlayer with the first crucible 1. A first through hole 3 is provided on the side wall of the second crucible 2 to connect the second crucible 2 with the first crucible 1. Granular silicon is put into the molten material interlayer and enters the second crucible 2 through the first through hole 3 after melting.

[0065] The preparation method comprises the following preparation steps:

[0066] Step S1, dissolving PVB in ethanol to prepare a binder solution, wherein the PVB content is 1wt%; uniformly mixing silicon powder with an average particle size of 0.5μm and yttrium oxide with the binder solution to form a slurry with a solid content of 40wt%, wherein the mass ratio of silicon powder to yttrium oxide is 95:5, and then spray granulation is performed, wherein the average particle size is 60μm, and a green body is obtained by cold isostatic pressing, and the green body is debinded under vacuum conditions at 400°C.

[0067] Step S2, after the debinding is completed, the green body is pre-nitrided and sintered in a nitrogen atmosphere in a sintering furnace at a temperature of 1200°C, a time of 8 hours, and a pressure of 1 atmosphere; the silicon nitride crucible assembly is machined; the machined silicon nitride crucible assembly is completely nitrided and sintered, first at a temperature of 1300°C and a pressure of 1 atmosphere for 36 hours, and then at a temperature of 1400°C and a pressure of 1 atmosphere for 24 hours; finally, densification sintering is performed at a temperature of 1650°C, a time of 4 hours, and a pressure of 10MPa to obtain a silicon nitride crucible assembly with a dense structure.

[0068] Step S3, finely process the silicon nitride crucible assembly, and then assemble it into a complete silicon nitride crucible, place the silicon nitride crucible in a fused quartz crucible, invert it on the support part 13, put it in a heating furnace 14, heat it to 1650°C, and evacuate it to a pressure of -100 kPa, as shown in FIG. Fig.13 As shown, a fused silica crucible is clamped onto the surface of a silicon nitride crucible to obtain a first crucible.

[0069] Step S4: placing the second crucible in the first crucible to form a molten material sandwich with the first crucible, and providing at least one first through hole on the side wall of the second crucible to connect the second crucible with the first crucible.

[0070] The second crucible 2 is a combined silicon nitride crucible comprising: an upper body 21, which is formed by a plurality of plate-shaped second silicon nitride components 211 surrounded by a clamping member 212; and a lower body 22, which has a clamping groove 221 at its upper end. The lower end of the upper body 21 is inserted into the clamping groove 221 at the upper end of the lower body 22.

[0071] Embodiment 2, as Figure 1-6 As shown, a combined crucible for continuous crystal pulling includes a first crucible 1 and a second crucible 2. The second crucible 2 is placed in the first crucible 1 to form a molten material interlayer with the first crucible 1. A first through hole 3 is provided on the side wall of the second crucible 2 to connect the second crucible 2 with the first crucible 1. Granular silicon is put into the molten material interlayer and enters the second crucible 2 through the first through hole 3 after melting.

[0072] The preparation method comprises the following preparation steps:

[0073] Step S1, dissolving PVB in ethanol to prepare a binder solution, wherein the PVB content is 2wt%; uniformly mixing silicon powder with an average particle size of 1.1μm and yttrium oxide with the binder solution to form a slurry with a solid content of 40wt%, wherein the mass ratio of silicon powder to yttrium oxide is 98:2, and then spray granulation is performed, wherein the average particle size is 80μm, and a green body is obtained by cold isostatic pressing, and the green body is debinded under vacuum conditions at 500°C.

[0074] Step S2, after the debinding is completed, the green body is pre-nitrided and sintered in a nitrogen atmosphere in a sintering furnace at a temperature of 1250°C, a time of 6 hours, and a pressure of 1 atmosphere; the silicon nitride crucible assembly is machined; the machined silicon nitride crucible assembly is completely nitrided and sintered, first at a temperature of 1350°C and a pressure of 1 atmosphere for 30 hours, and then at a temperature of 1450°C and a pressure of 1 atmosphere for 20 hours; finally, densification sintering is performed at a temperature of 1700°C, a time of 2 hours, and a pressure of 8MPa to obtain a silicon nitride crucible assembly with a dense structure.

[0075] Step S3, finely process the silicon nitride crucible assembly, and then assemble it into a complete silicon nitride crucible, place the silicon nitride crucible in a fused quartz crucible, invert it on the support part 13, put it in a heating furnace 14, heat it to 1700°C, and evacuate it to a pressure of -80 kPa, as shown in FIG. Fig.13 As shown, a fused silica crucible is clamped onto the surface of a silicon nitride crucible to obtain a first crucible.

[0076] Step S4: placing the second crucible in the first crucible to form a molten material sandwich with the first crucible, and providing at least one first through hole on the side wall of the second crucible to connect the second crucible with the first crucible.

[0077] The second crucible 2 is a combined silicon nitride crucible comprising: an upper body 21, which is formed by a plurality of plate-shaped second silicon nitride components 211 surrounded by a clamping member 212; and a lower body 22, which has a clamping groove 221 at its upper end. The lower end of the upper body 21 is inserted into the clamping groove 221 at the upper end of the lower body 22.

[0078] Embodiment 3, as Figure 1-6 As shown, a combined crucible for continuous crystal pulling includes a first crucible 1 and a second crucible 2. The second crucible 2 is placed in the first crucible 1 to form a molten material interlayer with the first crucible 1. A first through hole 3 is provided on the side wall of the second crucible 2 to connect the second crucible 2 with the first crucible 1. Granular silicon is put into the molten material interlayer and enters the second crucible 2 through the first through hole 3 after melting.

[0079] The preparation method comprises the following preparation steps:

[0080] Step S1, dissolving PVB in ethanol to prepare a binder solution, wherein the PVB content is 3wt%; mixing silicon powder with an average particle size of 1.5μm and the binder solution evenly to form a slurry with a solid content of 50wt%, and then spray granulating the slurry to obtain an average particle size of 100μm; and obtaining a green body by cold isostatic pressing, and debinding the green body under vacuum conditions at 600°C.

[0081] Step S2, after the debinding is completed, the green body is pre-nitrided and sintered in a nitrogen atmosphere in a sintering furnace at a temperature of 1300°C, a time of 4 hours, and a pressure of 1 atmosphere; the silicon nitride crucible assembly is machined; the machined silicon nitride crucible assembly is completely nitrided and sintered, first at a temperature of 1400°C and a pressure of 1 atmosphere for 24 hours, and then at a temperature of 1480°C and a pressure of 1 atmosphere for 12 hours; finally, densification sintering is performed at a temperature of 1800°C, a time of 1 hour, and a pressure of 5MPa to obtain a silicon nitride crucible assembly with a dense structure.

[0082] Step S3, finely process the silicon nitride crucible assembly, and then assemble it into a complete silicon nitride crucible, place the silicon nitride crucible in a fused quartz crucible, invert it on the support part 13, put it in a heating furnace 14, heat it to 1750°C, and evacuate it to a pressure of -60 kPa, as shown in FIG. Fig.13 As shown, a fused silica crucible is clamped onto the surface of a silicon nitride crucible to obtain a first crucible.

[0083] Step S4: placing the second crucible in the first crucible to form a molten material sandwich with the first crucible, and providing at least one first through hole on the side wall of the second crucible to connect the second crucible with the first crucible.

[0084] The second crucible 2 is a combined silicon nitride crucible comprising: an upper body 21, which is formed by a plurality of plate-shaped second silicon nitride components 211 surrounded by a clamping member 212; and a lower body 22, which has a clamping groove 221 at its upper end. The lower end of the upper body 21 is inserted into the clamping groove 221 at the upper end of the lower body 22.

[0085] The use of a combined silicon nitride crucible solves the problem that the existing high-strength silicon nitride crucible made by isostatic pressing is difficult to prepare in larger sizes and the problem that the oxygen content in the silicon wafer is high.

[0086] Example 4: Figure 7-8 As shown, on the basis of any one of embodiments 1-3, a cylindrical separator 5 is provided between the first crucible 1 and the second crucible 2 , and the granular silicon is blocked between the first crucible 1 and the cylindrical separator 5 .

[0087] The granular silicon is unevenly distributed in the upper and lower parts of the melt interlayer, and the temperature fluctuations in the upper and lower parts of the melt interlayer are large. The cylindrical separator 5 effectively avoids affecting the temperature in the second crucible 2.

[0088] The cylindrical separator 5 is provided with a plurality of third through holes 51 so that the granular silicon can pass through after being melted. The cylindrical separator 5 and the first crucible 1 form a melt interlayer, and the side wall of the second crucible 2 is provided with a first through hole 3 so that the second crucible 2 is connected with the first crucible 1. The granular silicon is put into the melt interlayer, passes through the third through holes 51 of the cylindrical separator 5 after being melted, and then enters the second crucible 2 through the first through hole 3.

[0089] Example 5: Figure 9-10 As shown, based on any one of the embodiments 1-3, a trumpet-shaped isolator 6 is provided between the first crucible 1 and the second crucible 2, and the granular silicon is blocked between the first crucible 1 and the trumpet-shaped isolator 6. The trumpet-shaped isolator 6 differs from the cylindrical isolator 5 in the embodiment 2 only in appearance.

[0090] Embodiment 6, as Figure 11-12 As shown, on the basis of any one of the embodiments 1-3, two opposite first through holes 3 are provided on the side wall of the second crucible 2, and a mixer 4 is provided in the second crucible 2. The mixer 4 has a cylindrical structure, and a second through hole 41 is provided on the surface. The ports at both ends of the mixer 4 are connected to the first through holes 3 on the side wall of the second crucible 2.

[0091] The granular silicon is put into the melt interlayer, and after melting, it enters the mixer 4 through the first through hole 3. After entering the mixer 4, the silicon liquid flows into the second crucible 2 through the second through hole 41 on the surface of the mixer 4.

[0092] In this article, relational terms such as first and second, etc. are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "comprise", "include" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the statement "comprise a ..." do not exclude the presence of other identical elements in the process, method, article or device including the elements.

[0093] In the description of the present invention, it is also necessary to explain that, unless otherwise clearly specified and limited, the terms "set", "install", "connect", and "connect" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0094] The above contents are merely examples and explanations of the structure of the present invention. The technicians in this technical field may make various modifications or additions to the specific embodiments described or replace them in a similar manner. As long as they do not deviate from the structure of the invention or exceed the scope defined by the claims, they should all fall within the protection scope of the present invention.

Claims

1. A combined crucible for continuous crystal pulling, characterized in that: The second crucible comprises a first crucible and a second crucible. The second crucible is placed in the first crucible to form a molten material interlayer with the first crucible. The side wall of the second crucible is provided with at least one first through hole to connect the second crucible with the first crucible.

2. A combined crucible for continuous crystal pulling according to claim 1, characterized in that: A mixer is arranged in the second crucible.

3. A combined crucible for continuous crystal pulling according to claim 2, characterized in that: The mixer has a cylindrical structure, a second through hole is arranged on the surface, and a mixer port is connected to the first through hole on the side wall of the second crucible.

4. The combined crucible for continuous crystal pulling according to claim 1, characterized in that: The second crucible includes one of an integral silicon nitride crucible and a combined silicon nitride crucible.

5. A combined crucible for continuous crystal pulling according to claim 4, characterized in that: The combined silicon nitride crucible comprises: Upper body: formed by a plurality of plate-shaped second silicon nitride components surrounded by a clamping piece; Lower body: with a slot at the upper end; The lower end of the upper body is inserted into the slot at the upper end of the lower body, and the first through hole is arranged on the lower body.

6. The method for preparing a combined crucible for continuous crystal pulling according to claim 1, characterized in that: An insulator is arranged between the first crucible and the second crucible, and a plurality of third through holes are arranged on the surface of the insulator.

7. The combined crucible for continuous crystal pulling according to claim 1, characterized in that: The preparation method comprises the following steps: Step S1, mixing silicon powder, sintering aid and binder solution into a uniform slurry, forming a green body by cold isostatic pressing, and debinding the green body; Step S2, after the binder removal is completed, the green body is sintered in a sintering furnace to obtain a silicon nitride component with a dense structure; Step S3, assembling a complete silicon nitride crucible from a plurality of silicon nitride components, and clamping a fused quartz crucible layer onto the surface of the silicon nitride crucible under negative pressure to obtain a first crucible; Step S4: placing the second crucible in the first crucible to form a molten material sandwich with the first crucible, and providing at least one first through hole on the side wall of the second crucible to connect the second crucible with the first crucible.

8. The method for preparing a combined crucible for continuous crystal pulling according to claim 7, characterized in that: The average particle size of the silicon powder is 0.5 to 1.5 μm.

9. The method for preparing a combined crucible for continuous crystal pulling according to claim 7, characterized in that: The binder solution is prepared by dissolving a binder in an organic solvent, and the binder content is 1-3 wt %.

10. The method for preparing a combined crucible for continuous crystal pulling according to claim 7, characterized in that: The sintering includes pre-nitriding sintering, complete nitriding sintering and densification sintering; The pre-nitridation sintering is carried out in a nitrogen and / or ammonia atmosphere at a temperature of 1200-1300° C. for 4-8 hours at a pressure of 1 atmosphere; The complete nitridation sintering is carried out in a nitrogen and / or ammonia atmosphere, first at a temperature of 1300-1400° C. and a pressure of 1 atmosphere for 24-36 hours, and then at a temperature of 1400-1480° C. and a pressure of 1 atmosphere for 12-24 hours; The densification sintering is carried out in a nitrogen atmosphere at a temperature of 1650-1800° C., a time of 1-4 hours, and a pressure of 5-10 MPa.

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