Thermal field of single crystal pulling furnace

Abstract

The invention discloses a single crystal pulling furnace thermal field, and belongs to the field of single crystal silicon production. The invention relates to a single crystal pulling furnace thermal field, which comprises a heat preservation base, a heating assembly, a heat insulation assembly and a heat insulation assembly, and is characterized in that the heat preservation base is provided with a crucible; the heat preservation cylinder comprises a first heat preservation cylinder and a second heat preservation cylinder, and the first heat preservation cylinder is fixedly installed above the heat preservation base and surrounds the crucible; the second heat preservation cylinder is detachably erected and installed above the first heat preservation cylinder, the first heat preservation cylinder supports the second heat preservation cylinder, the second heat preservation cylinder is provided with a flow guide cylinder, and the flow guide cylinder is located above the crucible; the lifting assembly is connected with the second heat preservation barrel and used for enabling the second heat preservation barrel to ascend and descend. The device has the effects of realizing rapid cooling of the thermal field and saving the cost.

Description

Technical Field

[0001] The present application relates to the field of single crystal silicon production, and in particular to a thermal field of a single crystal pulling furnace. Background Art

[0002] With the rapid development of fields such as artificial intelligence and new energy, the demand for semiconductor devices and photovoltaic cells is increasing. Silicon wafers are one of the important raw materials for semiconductor devices and photovoltaic cells. The production and research and development of silicon wafers have become a key factor in promoting industry upgrading.

[0003] Silicon crystals are generally divided into single crystals and polycrystals. The arrangement of atoms, ions or molecules inside a single crystal is uniform, and the entire crystal has only one crystal orientation and does not contain grain boundaries; while polycrystals are composed of many small grains, each of which has its own unique crystal orientation, and these grains are randomly oriented on a macro scale. Different structural characteristics give single crystals and polycrystals different properties. Single crystals have higher electron mobility and higher photoelectric efficiency, while polycrystals have lower production costs.

[0004] Due to the great structural differences between single crystals and polycrystalline, single crystals and polycrystalline are produced using different processes. Polycrystalline is mainly produced by directional solidification technology. Usually, the polycrystalline silicon material is melted in the ingot furnace first, and then the heating is stopped and cooled from the bottom of the ingot furnace to form a temperature gradient, so that the molten polycrystalline silicon liquid solidifies along the direction, and finally a polycrystalline silicon ingot is cast. Quasi-single crystals are also produced based on the process of polycrystalline ingot casting; single crystals are mainly produced by crystal rod pulling technology. After the polycrystalline silicon material is melted at high temperature in the crystal pulling furnace, the seed crystal is vertically dripped into the furnace. Through rotation and pulling, the silicon atoms will automatically form cylindrical crystals along the vertical seed crystal to form a single crystal silicon rod.

[0005] At present, the furnace for single crystal pulling needs to be cooled down before the single crystal silicon rod is taken out after being formed. Cooling is achieved by filling argon gas into the furnace, but the cooling speed is slow and the argon consumption cost is high. Summary of the invention

[0006] In order to achieve rapid cooling of the thermal field and save costs, the present application provides a thermal field of a single crystal pulling furnace.

[0007] The present application provides a single crystal pulling furnace thermal field adopts the following technical solution: A single crystal pulling furnace thermal field, comprising: A heat-insulating base, wherein the heat-insulating base is provided with a crucible: A heating assembly, used for heating the crucible; The heat-insulating cylinder comprises a first heat-insulating cylinder and a second heat-insulating cylinder, wherein the first heat-insulating cylinder is fixedly installed above the heat-insulating base and surrounds the crucible; the second heat-insulating cylinder is detachably mounted above the first heat-insulating cylinder, the first heat-insulating cylinder supports the second heat-insulating cylinder, and the second heat-insulating cylinder is provided with a guide cylinder, which is located above the crucible; A lifting component is connected to the second heat-insulating cylinder, and the lifting component is used to lift the second heat-insulating cylinder.

[0008] By adopting the above technical solution, the insulation tube is divided into two parts, the upper and lower parts, so that the insulation tube structure is improved from the original one-piece type to a detachable type, and the first insulation tube and the second insulation tube can be separated and combined by the lifting assembly. After the production of the single crystal silicon rod is completed in the hot field, the first insulation tube and the second insulation tube are separated to open the hot field. The heat inside the hot field is quickly dissipated to the furnace shell, and the furnace shell of the crystal pulling furnace remains closed at this time. The external air will not enter the hot field. The heat of the hot field is exchanged with the water-cooled wall of the furnace shell to achieve rapid cooling, and there is no need to introduce too much argon gas, reducing the argon consumption cost. In addition, the hot field can be opened by lifting the second insulation tube, so that the lifting load is small and easy to operate.

[0009] Optionally, a contact interface between the first heat-insulating cylinder and the second heat-insulating cylinder is stepped.

[0010] By adopting the above technical solution, the insulation tube structure is detachable. After the first insulation tube is combined with the second insulation tube, the stepped contact interface can effectively block the air flow channel of the contact interface, thereby reducing the occurrence of temperature leakage and improving the sealing of the thermal field.

[0011] Optionally, a first flexible ring is fixedly connected to the upper surface of the first insulation tube, and a second flexible ring is fixedly connected to the lower surface of the second insulation tube. The contact interface between the first flexible ring and the second flexible ring is stepped, the density of the first flexible ring is smaller than the density of the first insulation tube, and the density of the second flexible ring is smaller than the density of the second insulation tube.

[0012] By adopting the above technical solution, due to the different densities of the flexible ring and the insulation tube and the flexible characteristics, when the second insulation tube presses down the first insulation tube, the flexible ring is deformed, further compressing the air flow channel at the contact interface and reducing temperature leakage.

[0013] Optionally, the outer diameter of the first flexible ring is greater than the outer diameter of the second flexible ring.

[0014] By adopting the above technical solution, the supporting effect of the first heat-insulating tube on the second heat-insulating tube can be better exerted, thereby improving the stability of the overall structure of the heat-insulating tube.

[0015] Optionally, the contact interface between the first flexible ring and the second flexible ring includes an upper contact surface and a lower contact surface, the upper contact surface is higher than the lower contact surface, the adjacent surface between the upper contact surface and the lower contact surface is the interface, the upper contact surface is close to the outside of the thermal field, and the lower contact surface is close to the inside of the thermal field.

[0016] By adopting the above technical solution, when the first insulation tube is combined with the second insulation tube, the first flexible ring is easily aligned and contacted with the second flexible ring, so that the first insulation tube and the second insulation tube are combined while the flexible rings are deformed with each other.

[0017] Optionally, the first flexible ring is bounded by the interface, with the side close to the inside of the thermal field being the first hard part, and the side close to the outside of the thermal field being the first soft part; the second flexible ring is bounded by the interface, with the side close to the inside of the thermal field being the second soft part, and the side close to the outside of the thermal field being the second hard part, the density of the first hard part is greater than the density of the first soft part and greater than the density of the second soft part, and the density of the second hard part is greater than the density of the second soft part and greater than the density of the first soft part.

[0018] By adopting the above technical solution, the first hard part is closest to the crucible, so a larger density is set to reduce heat loss, and the overall density of the flexible ring is set to be non-uniform to promote mutual deformation of the flexible rings, making the contact interface between the first flexible ring and the second flexible ring tighter, thereby improving the sealing of the insulation tube.

[0019] Optionally, a first reinforcement ring is fixedly connected to the upper surface of the first insulation tube, and the first reinforcement ring is located inside the first hard part; a second reinforcement ring and a third reinforcement ring are fixedly connected to the lower surface of the second insulation tube, and the second reinforcement ring is located inside the second soft part, and the third reinforcement ring is located inside the second hard part; the density of the first reinforcement ring, the second reinforcement ring and the third reinforcement ring are all greater than the density of the first flexible ring.

[0020] By adopting the above technical scheme, the first reinforcement ring, the second reinforcement ring and the third reinforcement ring can enhance the supporting strength of the flexible ring and play a heat insulating role. At the same time, the density difference inside the flexible ring and the stepped interface make the contact interface present a slight undulating structure. The second soft part deforms outward to further compress the interface, and the first soft part deforms upward to increase the degree of sealing of the outer end of the contact interface, thereby greatly improving the sealing of the insulation tube, forming a thermal field with high sealing, reducing heat loss during the crystal pulling process, and also reducing heat loss to the insulation tube structure.

[0021] Optionally, the lifting assembly includes a driving member and a suspension rod, the suspension rod is connected to the second heat insulation cylinder, and the driving member is used to drive the suspension rod to rise and fall.

[0022] By adopting the above technical solution, the lifting and lowering of the second heat-insulating cylinder is achieved.

[0023] Optionally, the heating assembly includes a first heater and a second heater, the first heater is arranged around a side wall of the crucible, and the second heater is arranged at the bottom of the crucible.

[0024] By adopting the above technical solution, the crucible is fully heated to achieve melting of the polysilicon material.

[0025] Optionally, a support ring is provided on the top of the second heat-insulating tube, and the guide tube is mounted on the support ring.

[0026] In summary, this application has the following beneficial effects: 1. The present application divides the insulation tube into two parts, the upper and lower parts, so that the insulation tube structure is improved from the original one-piece type to a detachable type, and the first insulation tube and the second insulation tube can be separated and combined through the lifting assembly. After the production of the single crystal silicon rod is completed in the hot field, the first insulation tube and the second insulation tube are separated to open the hot field. The heat inside the hot field is quickly dissipated to the furnace shell, and the furnace shell of the crystal pulling furnace remains closed at this time. The external air will not enter the hot field. The heat of the hot field is exchanged with the water-cooled wall of the furnace shell to achieve rapid cooling, and there is no need to introduce too much argon gas, reducing the argon consumption cost. In addition, the hot field can be opened by lifting the second insulation tube, so that the lifting load is small and easy to operate.

[0027] 2. The present application also arranges a flexible ring and a reinforcement ring between the first insulation tube and the second insulation tube. The reinforcement ring can enhance the supporting strength of the flexible ring and play a heat insulating role. At the same time, the density difference inside the flexible ring and the stepped interface make the contact interface present a slight undulating structure. The second soft part deforms outward to further compress the interface, and the first soft part deforms upward to increase the degree of sealing of the outer end of the contact interface, thereby greatly improving the sealing of the insulation tube, forming a thermal field with high sealing, reducing heat loss during the crystal pulling process, and also reducing heat loss to the insulation tube structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a cross-sectional schematic diagram of the thermal field of the single crystal pulling furnace of Example 1 of the present application.

[0029] Figure 2 yes Figure 1 A partial enlarged view of middle A.

[0030] Figure 3 It is a cross-sectional schematic diagram of the thermal field of the single crystal pulling furnace of Example 2 of the present application.

[0031] Figure 4 yes Figure 3 A partial enlarged view of B.

[0032] Figure 5 It is a cross-sectional schematic diagram of the thermal field of the single crystal pulling furnace of Example 3 of the present application.

[0033] Figure 6 yes Figure 5 A partial enlarged view of C in the middle.

[0034] Description of reference numerals: 1. Furnace shell; 11. Water-cooled wall; 2. Insulation base; 21. Crucible; 3. Insulation tube; 31. First insulation tube; 32. Second insulation tube; 33. Support ring; 34. Guide tube; 4. First heater; 41. Second heater; 5. Hanging rod; 51. Fixing nut; 6. First flexible ring; 61. First hard part; 62. First soft part; 63. First reinforcement ring; 7. Second flexible ring; 71. Second hard part; 72. Second soft part; 73. Second reinforcement ring; 74. Third reinforcement ring; 8. Interface; 81. Upper contact surface; 82. Lower contact surface. DETAILED DESCRIPTION

[0035] The following is combined with Figure 1-6 This application is described in further detail.

[0036] In the prior art, a single crystal pulling furnace includes a furnace shell and a heat field. The furnace shell forms a closed space around the heat field. Polysilicon material is melted in the heat field and is pulled by seed crystal to form a single crystal silicon rod. Finally, the furnace shell and the heat field are opened to take out the single crystal silicon rod.

[0037] After the production of single crystal silicon rods is completed, the inside of the hot field is still in a high temperature state. If the furnace shell is opened directly to dissipate heat, outside air will enter. At high temperatures, oxygen will oxidize the hot field and damage the hot field. Therefore, people usually continue to introduce argon gas, use the flow of argon gas to take away the heat to achieve cooling of the hot field, and then open the furnace shell, but the argon gas consumption cost is relatively high.

[0038] Example 1 The present application embodiment discloses a single crystal pulling furnace thermal field. Figure 1 and Figure 2 As shown, a thermal field of a single crystal pulling furnace includes an insulation base 2, an insulation tube 3, a heating component and a lifting component. The insulation base 2 is installed with a crucible 21, and the crucible 21 is used to melt polysilicon material to form a melt. The seed crystal is suspended from the top of the crucible 21 into the melt, and a single crystal silicon rod is formed by rotating and pulling.

[0039] The heat field is arranged inside the furnace shell 1, and the furnace shell 1 forms a closed space around the heat field. The inner wall of the furnace shell 1 is arranged as a water-cooled wall 11, which effectively reduces the high temperature of the heat field from being transferred to the environment outside the furnace shell 1, and keeps the crystal pulling workshop at a normal temperature.

[0040] The insulation tube 3 includes a first insulation tube 31 and a second insulation tube 32. The first insulation tube 31 is fixedly installed above the insulation base 2. The first insulation tube 31 is arranged around the crucible 21, and there is a gap between the first insulation tube 31 and the crucible 21. The second insulation tube 32 is detachably mounted above the first insulation tube 31. The first insulation tube 31 supports the second insulation tube 32. The second insulation tube 32 is equipped with a guide tube 34. The guide tube 34 is located above the crucible 21. The top of the second insulation tube 32 is provided with a support ring 33. The guide tube 34 is mounted on the support ring 33. The seed crystal is suspended into the crucible 21 through the guide tube 34. The insulation tube 3 is made of sintered carbon-carbon composite material.

[0041] The heating assembly includes a first heater 4 and a second heater 41. The first heater 4 and the second heater 41 can be graphite heaters. The first heater 4 is arranged around and close to the side wall of the crucible 21, and the second heater 41 is arranged at the bottom of the crucible 21, so as to fully heat the crucible 21 and melt the polysilicon material.

[0042] The lifting assembly is connected to the second heat-insulating tube 32, and the lifting assembly includes a driving member and a suspension rod 5. The driving member can be electrically driven, pneumatically driven or hydraulically driven. The driving member can be an electric push rod, and the driving member is installed on the furnace shell 1. The suspension rod 5 is vertically penetrated in the second heat-insulating tube 32, and the bottom of the suspension rod 5 is threadedly connected with a fixing nut 51 to realize the load-bearing of the second heat-insulating tube 32 and make the suspension rod 5 move synchronously with the second heat-insulating tube 32. There are multiple suspension rods 5, and specifically four can be distributed at intervals along the circumferential direction. The driving member drives the suspension rod 5 to rise and fall, which can realize the lifting and falling of the second heat-insulating tube 32, and realize the separation and combination of the first heat-insulating tube 31 and the second heat-insulating tube 32.

[0043] When the production of the single crystal silicon rod is completed in the hot field, the second insulation tube 32 is pulled up by the lifting assembly to separate the first insulation tube 31 and the second insulation tube 32, so that the hot field is opened, and the heat inside the hot field is quickly dissipated to the furnace shell 1. At this time, the furnace shell 1 will not be opened and remain in a closed state, and the external air will not enter the hot field, forming a protection for the hot field. The heat of the hot field is heat exchanged with the water-cooled wall 11 of the furnace shell 1 to achieve rapid cooling. After cooling, the furnace shell 1 is opened to take out the single crystal silicon rod. Therefore, there is no need to introduce too much argon during the cooling process, thereby reducing the argon consumption cost.

[0044] In addition, the heat field can be opened only by lifting the second insulation tube 32, so the lifting load is relatively small, and when the first insulation tube 31 and the second insulation tube 32 are combined, the first insulation tube 31 and the insulation base 2 are fixedly connected, and the stability of the first insulation tube 31 and the insulation base 2 is relatively high. The suspension rod 5 does not need to continuously lift the second insulation tube 32, and the second insulation tube 32 is pressed against the upper surface of the first insulation tube 31 by gravity, which is easy to operate.

[0045] Since the first insulation tube 31 and the second insulation tube 32 need to be separated and combined, in order to ensure the airtightness of the insulation tube 3, in the present embodiment, the upper surface of the first insulation tube 31 and the lower surface of the second insulation tube 32 are contact-connected, and the contact interface between the first insulation tube 31 and the second insulation tube 32 is stepped, blocking the air flow path at the contact interface, thereby reducing the occurrence of temperature leakage and further saving energy consumption costs.

[0046] Example 2 In this embodiment, if Figure 3 and Figure 4 As shown, the difference from Example 1 is that the upper surface of the first heat-insulating tube 31 and the lower surface of the second heat-insulating tube 32 are both planes, and a first flexible ring 6 and a second flexible ring 7 are arranged between the first heat-insulating tube 31 and the second heat-insulating tube 32. The first flexible ring 6 and the second flexible ring 7 are both annular structures, and the first flexible ring 6 is fixedly connected to the upper surface of the first heat-insulating tube 31, and the second flexible ring 7 is fixedly connected to the upper surface of the second heat-insulating tube 32. The contact interface between the first flexible ring 6 and the second flexible ring 7 is stepped, and the air flow channel between the contact interfaces is also blocked.

[0047] Specifically, the contact interface between the first flexible ring 6 and the second flexible ring 7 includes an upper contact surface 81 and a lower contact surface 82. The upper contact surface 81 is higher than the lower contact surface 82. The adjacent surface between the upper contact surface 81 and the lower contact surface 82 is the interface 8. The upper contact surface 81 is close to the outside of the thermal field, and the lower contact surface 82 is close to the inside of the thermal field.

[0048] The first flexible ring 6 and the second flexible ring 7 are both made of uncarbonized carbon fiber soft felt. The density of the first flexible ring 6 is smaller than that of the first thermal insulation tube 31 , and the density of the second flexible ring 7 is smaller than that of the second thermal insulation tube 32 .

[0049] Specifically, the thickness of the first flexible ring 6 and the second flexible ring 7 are both 15-25 mm, preferably 25 mm, and the density of the first flexible ring 6 and the second flexible ring 7 are both 0.05-0.08 g / cm 3 , preferably 0.05g / cm 3 The density of the first heat preservation tube 31 and the second heat preservation tube 32 are both 0.15~0.20g / cm 3 , preferably 0.15g / cm 3 By controlling the density difference, the pressure when the second insulation tube 32 and the first insulation tube 31 are combined enables the flexible rings to deform flexibly with each other, so that the bonding interface between the second insulation tube 32 and the first insulation tube 31 is tighter, so that even if the insulation tube 3 is a detachable structure, the thermal insulation performance of the insulation tube 3 can still be guaranteed.

[0050] In addition, the outer diameter of the first flexible ring 6 is greater than the outer diameter of the second flexible ring 7 , so that the first thermal insulation tube 31 can better support the second thermal insulation tube 32 , thereby improving the stability of the overall structure of the thermal insulation tube 3 .

[0051] Example 3 In this embodiment, if Figure 5 and Figure 6 As shown, the difference from Example 2 is that the first flexible ring 6 is bounded by the interface 8, and the side close to the inside of the thermal field is the first hard part 61, and the side close to the outside of the thermal field is the first soft part 62; the second flexible ring 7 is bounded by the interface 8, and the side close to the inside of the thermal field is the second soft part 72, and the side close to the outside of the thermal field is the second hard part 71, the density of the first hard part 61 is greater than the density of the first soft part 62 and greater than the density of the second soft part 72, and the density of the second hard part 71 is greater than the density of the second soft part 72 and greater than the density of the first soft part 62.

[0052] Specifically, the density of the first soft part 62 and the second soft part 72 are both 0.02-0.04 g / cm 3 , preferably 0.02 g / cm 3 The density of the first hard part 61 and the second hard part 71 are both 0.05-0.08 g / cm 3 , preferably 0.05g / cm 3 .

[0053] A first reinforcement ring 63 is fixedly connected to the upper surface of the first heat-insulating tube 31 , and a second reinforcement ring 73 and a third reinforcement ring 74 are fixedly connected to the lower surface of the second heat-insulating tube 32 . The first reinforcement ring 63 , the second reinforcement ring 73 and the third reinforcement ring 74 are made of sintered carbon-carbon composite materials.

[0054] The first reinforcement ring 63, the second reinforcement ring 73 and the third reinforcement ring 74 are all annular structures. The first flexible ring 6 and the second flexible ring 7 are both provided with corresponding mounting grooves, so that the first reinforcement ring 63 is located inside the first hard part 61, the second reinforcement ring 73 is located inside the second soft part 72, and the third reinforcement ring 74 is located inside the second hard part 71. The density of the first reinforcement ring 63, the second reinforcement ring 73 and the third reinforcement ring 74 is 0.12~0.15g / cm 3 , preferably 0.12 g / cm 3 The first reinforcement ring 63, the second reinforcement ring 73 and the third reinforcement ring 74 can enhance the support strength of the flexible ring and play a role in heat insulation.

[0055] Specifically, viewed from the horizontal direction, the first reinforcement ring 63 is located between the second reinforcement ring 73 and the interface 8, and the distance between the third reinforcement ring 74 and the interface 8 is greater than the distance between the second reinforcement ring 73 and the interface 8, thereby controlling and adjusting the deformation of the flexible ring. At the same time, the density difference inside the flexible ring and the stepped interface make the contact interface present a slight undulating structure. The second soft portion 72 deforms outward to further compress the interface 8. In addition, the outer diameter of the first flexible ring 6 is greater than the outer diameter of the second flexible ring 7, so that the first soft portion 62 deforms upward to increase the degree of sealing of the outer end of the contact interface, forming a thermal field with high sealing properties, reducing heat loss during the crystal pulling process, and also reducing heat loss to the insulation tube 3 structure.

[0056] In practical applications, it is shown that compared with the thermal field of application example 1, the energy consumption of the thermal field of embodiment 3 is reduced by 7.1%, and compared with the thermal field of application example 2, the energy consumption of the thermal field of embodiment 3 is reduced by 5.4%.

[0057] The implementation principle of the thermal field of a single crystal pulling furnace in the embodiment of the present application is: After the seed crystal is formed into a single crystal silicon rod by rotating and pulling in the polycrystalline melt in the crucible 21, the driving part is started to drive the suspension rod 5 to lift, so that the second insulation tube 32 is separated from the first insulation tube 31, and the thermal field is opened. The heat inside the thermal field is quickly dissipated to the furnace shell 1. At this time, the furnace shell 1 of the crystal pulling furnace remains in a closed state, and the external air does not enter the thermal field. The heat of the thermal field is heat exchanged with the water-cooled wall 11 of the furnace shell 1 to achieve rapid cooling.

[0058] This specific implementation manner is merely an explanation of the present application and is not a limitation of the present application. After reading this specification, those skilled in the art may make non-creative modifications to the specific implementation manner as needed, but such modifications are protected by the patent law as long as they are within the scope of the claims of the present application.

Claims

1. A single crystal pulling furnace thermal field, characterized in that: include: A heat-insulating base (2), wherein the heat-insulating base (2) is provided with a crucible (21): A heating component, used for heating the crucible (21); The heat-insulating cylinder (3) comprises a first heat-insulating cylinder (31) and a second heat-insulating cylinder (32), wherein the first heat-insulating cylinder (31) is fixedly mounted above the heat-insulating base (2), and the first heat-insulating cylinder (31) is arranged around the crucible (21); the second heat-insulating cylinder (32) is detachably mounted above the first heat-insulating cylinder (31), the first heat-insulating cylinder (31) supports the second heat-insulating cylinder (32), and the second heat-insulating cylinder (32) is provided with a guide cylinder (34), and the guide cylinder (34) is located above the crucible (21); A lifting component is connected to the second heat-insulating cylinder (32), and the lifting component is used to lift and lower the second heat-insulating cylinder (32).

2. The single crystal pulling furnace thermal field according to claim 1, characterized in that: The contact interface between the first heat-insulating cylinder (31) and the second heat-insulating cylinder (32) is in a stepped shape.

3. The single crystal pulling furnace thermal field according to claim 1, characterized in that: A first flexible ring (6) is fixedly connected to the upper surface of the first heat-insulating tube (31), and a second flexible ring (7) is fixedly connected to the lower surface of the second heat-insulating tube (32). The contact interface between the first flexible ring (6) and the second flexible ring (7) is stepped. The density of the first flexible ring (6) is smaller than that of the first heat-insulating tube (31), and the density of the second flexible ring (7) is smaller than that of the second heat-insulating tube (32).

4. The single crystal pulling furnace thermal field according to claim 3, characterized in that: The outer diameter of the first flexible ring (6) is greater than the outer diameter of the second flexible ring (7).

5. The thermal field of a single crystal pulling furnace according to claim 3, characterized in that: The contact interface between the first flexible ring (6) and the second flexible ring (7) comprises an upper contact surface (81) and a lower contact surface (82), wherein the upper contact surface (81) is higher than the lower contact surface (82), and the surface adjacent to the upper contact surface (81) and the lower contact surface (82) is a contact surface (8), wherein the upper contact surface (81) is close to the outside of the thermal field, and the lower contact surface (82) is close to the inside of the thermal field.

6. The thermal field of a single crystal pulling furnace according to claim 5, characterized in that: The first flexible ring (6) is bounded by the interface (8), the side close to the inside of the thermal field is the first hard part (61), and the side close to the outside of the thermal field is the first soft part (62); the second flexible ring (7) is bounded by the interface (8), the side close to the inside of the thermal field is the second soft part (72), and the side close to the outside of the thermal field is the second hard part (71), the density of the first hard part (61) is greater than the density of the first soft part (62) and greater than the density of the second soft part (72), and the density of the second hard part (71) is greater than the density of the second soft part (72) and greater than the density of the first soft part (62).

7. The thermal field of a single crystal pulling furnace according to claim 6, characterized in that: A first reinforcement ring (63) is fixedly connected to the upper surface of the first heat-insulating tube (31), and the first reinforcement ring (63) is located inside the first hard part (61). A second reinforcement ring (73) and a third reinforcement ring (74) are fixedly connected to the lower surface of the second heat-insulating tube (32), and the second reinforcement ring (73) is located inside the second soft part (72), and the third reinforcement ring (74) is located inside the second hard part (71). The density of the first reinforcement ring (63), the second reinforcement ring (73) and the third reinforcement ring (74) are all greater than the density of the first flexible ring (6).

8. A single crystal pulling furnace thermal field according to any one of claims 1 to 7, characterized in that: The lifting assembly comprises a driving member and a suspension rod (5), wherein the suspension rod (5) is connected to the second heat-insulating cylinder (32), and the driving member is used to drive the suspension rod (5) to rise and fall.

9. A single crystal pulling furnace thermal field according to any one of claims 1 to 7, characterized in that: The heating assembly comprises a first heater (4) and a second heater (41), wherein the first heater (4) is arranged around the side wall of the crucible (21), and the second heater (41) is arranged at the bottom of the crucible (21).

10. A single crystal pulling furnace thermal field according to any one of claims 1 to 7, characterized in that: A support ring (33) is provided on the top of the second heat-insulating cylinder (32), and the flow guide cylinder (34) is mounted on the support ring (33).

Images