Single crystal furnace

Abstract

The utility model belongs to the technical field of production of monocrystalline silicon, and particularly relates to a single crystal furnace which comprises a furnace body, the crucible is arranged in the furnace body in a liftable manner; the exhaust device is arranged below the crucible and comprises an air suction end and an exhaust end, the air suction end is located in the furnace body, the exhaust end is communicated to the outside of the furnace body, and at least the air suction end synchronously ascends and descends along with the crucible. When the single crystal furnace disclosed by the utility model is used for drawing a single crystal silicon rod, the liquid level of a molten silicon material in the crucible is gradually reduced, the crucible is gradually lifted, and the suction end of the exhaust device is lifted along with the crucible. According to the scheme, the air suction end can synchronously lift along with the crucible, so that the distance between the opening edge of the crucible and the air suction end can be kept constant, on one hand, the exhaust path of SiO from the bottom of the crucible to the exhaust device is effectively shortened, and on the other hand, vortexes are prevented from being formed below the crucible; the problem that the oxygen content of the silicon single crystal rod is increased due to the fact that discharging of SiO is blocked can be solved.

Description

Technical Field

[0001] This utility model relates to the field of monocrystalline silicon production technology, and in particular to a monocrystalline furnace. Background Technology

[0002] In the preparation of single-crystal silicon rods, the oxygen content is a key process parameter determining the quality of the silicon rod. The main source of oxygen is gaseous SiO generated by the continuous reaction between the quartz crucible and molten silicon at high temperatures. This gaseous SiO is carried into the silicon single-crystal growth interface by thermal convection of the melt, thus entering the single-crystal silicon rod. To reduce the oxygen content in the single-crystal silicon rod, an inert gas is typically introduced into the single-crystal furnace during preparation. The gas flow formed by the inert gas promptly carries away the gaseous SiO, thereby reducing the amount of gaseous SiO entering the single-crystal growth interface and lowering the oxygen content in the single-crystal silicon rod. The inert gas flow generally carries the gaseous SiO, first transferring it from the surface of the molten silicon to the edge of the crucible opening, then descending along the outer wall of the crucible to the bottom, and finally exiting the single-crystal furnace cavity through the exhaust port at the bottom of the furnace.

[0003] During the crystal pulling process, as the liquid level of the molten silicon material decreases, the position of the crucible needs to be raised accordingly to maintain the stability of the solid-liquid interface. However, at this stage, the inert gas flow carrying SiO is obstructed from being discharged, resulting in oxygen reversal in the oxygen content of the single crystal silicon rod (the phenomenon of increased oxygen content at the tail of the single crystal silicon rod). Utility Model Content

[0004] To improve the problem of oxygen content in single-crystal silicon rods warping due to obstructed SiO discharge, this invention provides a single-crystal furnace.

[0005] A single crystal furnace according to an embodiment of the present invention includes:

[0006] Furnace body;

[0007] The crucible is height-adjustable and is installed inside the furnace body;

[0008] An exhaust device is provided in a guide pipe located below the crucible. The guide pipe includes an intake end and an exhaust end located below the intake end. The intake end is located inside the furnace body, and the exhaust end is connected to a vacuum system outside the furnace body. At least the intake end moves up and down synchronously with the crucible.

[0009] In some embodiments, the exhaust device includes a vertically arranged guide pipe, the upper end of which is the intake end and the lower end of which is the exhaust end.

[0010] In some embodiments, the exhaust end is connected to the evacuation system outside the furnace body via an exhaust port opened at the bottom of the furnace body.

[0011] In some embodiments, the exhaust device further includes a guide ring connected to the intake end, the guide ring having a guide channel leading from below the crucible to the intake end.

[0012] In some embodiments, the guide ring has a hollow annular chamber inside, and the top end face of the guide ring is provided with a plurality of first air guide holes communicating with the annular chamber. The bottom end face of the guide ring is connected to the second air guide hole communicating with the air intake end. The first air guide holes, the annular chamber, and the second air guide holes form the guide channel.

[0013] In some embodiments, the top end face and the bottom end face of the flow guide ring are recessed downwards.

[0014] In some embodiments, the exhaust device further includes a liftable lifting rod and a driver for driving the lifting rod to move up and down. The top of the lifting rod is fixedly connected to the end face of the bottom of the guide ring, and the bottom of the lifting rod movably passes through the bottom of the furnace body and extends out of the furnace body to connect with the driver.

[0015] In some embodiments, the exhaust end and the intake end can be raised and lowered synchronously.

[0016] In some embodiments, the exhaust end is fixed and the flow guide pipe is retractable.

[0017] In some embodiments, the single crystal furnace further includes a heater and a heat insulation cylinder, the heater being arranged around the outer periphery of the single crystal furnace, and the heat insulation cylinder being disposed below the heater;

[0018] The inner diameter of the insulation cylinder is smaller than the outer diameter of the support leg of the heater, and the insulation cylinder has a notch inside for the support leg to pass through.

[0019] In the single-crystal furnace of this invention, during the pulling of single-crystal silicon rods, the liquid level of the molten silicon material in the crucible gradually decreases, while the crucible gradually rises, and the suction end of the exhaust device rises along with the crucible. Compared to the traditional single-crystal furnace where gaseous SiO enters below the crucible and can only be discharged from the exhaust port at the bottom of the furnace under the action of airflow, the suction end of this embodiment can rise and fall synchronously with the crucible, so that the distance between the edge of the crucible opening and the suction end can remain constant. On the one hand, this effectively shortens the path of SiO from the bottom of the crucible to the exhaust device; on the other hand, it guides the discharge path of SiO from the bottom of the crucible to the bottom of the furnace, avoiding the formation of vortices below the crucible. This can accelerate the discharge speed of SiO and improve the problem of the oxygen content of the single-crystal silicon rod warping due to obstructed SiO discharge. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the internal structure of the furnace body for single crystal in this embodiment;

[0021] Figure 2 This is an exploded schematic diagram showing the exhaust device and evacuation system of the single crystal furnace in this embodiment connected through the furnace bottom;

[0022] Figure 3 This is a schematic diagram of the connection between the flow guide pipe and the flow guide ring;

[0023] Figure 4 for Figure 3 Schematic diagram of the cross-sectional structure at point AA;

[0024] Figure 5 This is a schematic diagram of the structure of the insulation cylinder;

[0025] Figure 6 This is a schematic diagram of the structure at the bottom of the furnace body;

[0026] Figure 7 This is a schematic diagram of the airflow inside the single crystal furnace in this embodiment;

[0027] Figure 8 This is a schematic diagram of the airflow inside an existing single crystal furnace.

[0028] In the diagram: Furnace body 10; Exhaust port 11; Crucible 20; Heater 30; Support leg 31; Lifting shaft 40; Bracket 41; Insulation cylinder 50; Notch 51; Guide pipe 60; Intake end 61; Exhaust end 62; Guide ring 70; Annular chamber 71; First air guide hole 72; Second air guide hole 73; Guide channel 74; Vacuum system 80; Inlet section 81; Transition section 82; Collector section 83; Outlet section 84; Lifting rod 90. Detailed Implementation

[0029] To make the objectives, technical solutions, and advantages of this utility model clearer, the present utility model will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the present utility model and are not intended to limit the present utility model.

[0030] The structures, proportions, sizes, etc., shown in the accompanying drawings of this specification are only for the purpose of assisting those skilled in the art in understanding and reading the content disclosed in the specification, and are not intended to limit the conditions under which this utility model can be implemented. Any modifications to the structure, changes in the proportions, or adjustments to the size, without affecting the effects and purposes that this utility model can produce, should still fall within the scope of the technical content disclosed in this utility model.

[0031] The orientations or positional relationships indicated by terms such as "upper," "lower," "left," "right," "middle," "longitudinal," "transverse," "horizontal," "inner," "outer," "radial," and "circumferential" used in this specification are based on the orientations or positional relationships shown in the accompanying drawings and are only for the purpose of simplifying the description. They do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as limiting the present invention. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0032] like Figure 8 As shown, in existing single-crystal furnaces, as the molten silicon level decreases and the crucible position is correspondingly raised, the inert gas flow carrying SiO is obstructed from exiting, leading to an oxygen reversal in the oxygen content of the single-crystal silicon rod. The main reasons for this are:

[0033] 1. After the crucible is raised, the distance between the bottom of the crucible and the exhaust port at the bottom of the furnace increases, which prolongs the exhaust path of SiO gas and increases the difficulty of SiO exhaust.

[0034] 2. After the crucible is lifted, the blank area formed between it and the bottom of the furnace becomes larger. This blank area can easily cause the airflow to generate cyclones, which can hinder the normal discharge of SiO.

[0035] like Figure 1As shown, this embodiment provides a single crystal furnace, including a furnace body 10, a crucible 20, an exhaust device, and a vacuum system 80. The crucible 20 is vertically detachable inside the furnace body 10 and contains silicon material. According to one embodiment, the single crystal furnace further includes a lifting shaft 40, positioned below the crucible 20. A bracket 41 is provided at the top of the lifting shaft 40 to support the bottom of the crucible 20. The bottom of the lifting shaft 40 movably passes through the bottom of the furnace body 10 and extends out of the furnace body 10, so that a drive component for driving the lifting shaft 40 is connected to the bottom of the lifting shaft 40. The vacuum system 80 is located outside the furnace body 10 and is used to evacuate the interior of the furnace body 10. It should be noted that the furnace body 10, crucible 20, lifting shaft 40, drive component, and vacuum system 80 of this embodiment are all prior art; therefore, their specific structures will not be described in detail in this embodiment. An exhaust device 20 is located below the crucible 20, including an intake end 61 and an exhaust end 62 located below the intake end 61. The intake end 61 is located inside the furnace body 10, and the exhaust end 62 is connected to the external evacuation system 80 of the furnace body 10. At least the intake end 61 moves up and down with the crucible 20. The intake end 61 is located above the exhaust end 62, allowing the airflow to enter the intake end 61 and be smoothly discharged from the exhaust end 62 after being guided by the exhaust device. The exhaust end 62 is connected to the external evacuation system 80, allowing the airflow to exit the single crystal furnace under the action of the evacuation system 80 after exiting the exhaust end 62. Therefore, after being guided by the exhaust device, the airflow can be facilitated to exit the single crystal furnace. In this embodiment, the suction end 61 rises and falls synchronously with the crucible 20. During the preparation of the single crystal silicon rod, when the crucible is raised, the suction end 61 rises and falls with the crucible 20, which allows the airflow to enter the suction end 61 more quickly after flowing out from the upper rear edge of the crucible, and then be quickly discharged under the guidance of the exhaust device, reducing the residence time of the airflow under the crucible.

[0036] In this embodiment, during the pulling of single-crystal silicon rods, the liquid level of the molten silicon in the crucible 20 gradually decreases, while the crucible 20 gradually rises. The suction end 61 of the guide pipe 60 rises along with the crucible 20; that is, the distance between the suction end 61 of the guide pipe 60 and the crucible 20 remains constant. See details... Figure 7 and Figure 8 Compared to the traditional method of discharging SiO from the exhaust port 11 without the guidance of an exhaust device, the exhaust device added in this embodiment effectively shortens the path of SiO from the bottom of the crucible 20 to the exhaust device, and guides the path of SiO from the bottom of the crucible 20 to the furnace bottom, avoiding the formation of vortices below the crucible 20. This can accelerate the discharge speed of SiO and improve the problem of the oxygen content of the single crystal silicon rod warping due to the obstruction of SiO discharge.

[0037] See details Figure 2In this embodiment, the exhaust port 11 of the single crystal furnace is located at the bottom of the furnace body 10. The exhaust device includes a vertically arranged guide pipe 60, with an intake end 61 at the top and an exhaust end 62 at the bottom. The exhaust end 62 is connected to the vacuum system 80 outside the furnace body 10 through the exhaust port 11. The guide pipe 60 connects to the vacuum system 80 through the existing exhaust port 11, eliminating the need to change the layout of existing components in a traditional single crystal furnace and reducing modification costs. The number of guide pipes 60 in this embodiment can be set according to actual needs; for example, if two exhaust ports 11 are provided at the bottom of the furnace body 10, then the number of guide pipes 60 is two.

[0038] In some embodiments, the exhaust end 62 and the intake end 61 can be raised and lowered synchronously. The exhaust end 61 is located outside the furnace body 10 and can be raised and lowered relative to the exhaust port 11. In some embodiments, the exhaust end 62 is fixedly installed, and the guide pipe 60 is retractable. In other embodiments, the guide pipe 60 can be implemented in any form, as long as the intake end 61 can be raised and lowered.

[0039] For example, the guide pipe 60 is non-extendable, the intake end 61 and the exhaust end 62 rise and fall synchronously, and the exhaust end 62 can be inserted into the pipe of the vacuum system 80 and rise and fall within the pipe of the vacuum system 80.

[0040] For example, the flow guide duct 60 may include at least two spliced ​​rigid pipe sections, which are nested to form a telescopic tubular structure, allowing the intake end 61 of the flow guide duct 60 to rise and fall with the crucible 20, while the exhaust end 62 of the flow guide duct 60 remains fixed. In some embodiments, the flow guide duct 60 may also be a flexible pipe, such as a corrugated pipe, allowing the intake end 61 of the flow guide duct 60 to rise and fall with the crucible 20, while the exhaust end 62 of the flow guide duct 60 remains fixed.

[0041] In this embodiment, the evacuation system 80 includes a suction pipe and a suction pump. Preferably, the suction pipe includes an inlet section 81 for connecting to the exhaust port 11. The inlet section 81 is vertically positioned below the exhaust port 11. The suction pipe 80 also preferably includes a transition section 82, a collecting section 83, and an outlet section 84, which are sequentially connected to the inlet section 81. The outlet section 84 is connected to the suction pump. Gas in the inlet section 81 first passes through the transition section 82 and is collected in the collecting section 83, then passes through the outlet section 84 and is drawn out by the suction pump. The transition section 82 extends laterally along the inlet section 81 to avoid interference between the suction pipe 80 and the drive component at the bottom of the lifting shaft 40.

[0042] As described above, when the intake end 61 and exhaust end 62 of the guide pipe 60 rise and fall synchronously, the exhaust end 62 can move vertically through the intake section 81. In this case, the diameter of the intake section 81 is slightly larger than the diameter of the guide pipe 60, allowing the guide pipe 60 to move vertically through the intake section 81. The intake section 81 is fitted onto the outer periphery of the portion of the guide pipe 60 that extends out of the furnace body 10, allowing the guide pipe 60 to move vertically within the intake section 81 to meet the rising and falling requirements of the entire guide pipe 60.

[0043] See details Figure 3-4 The exhaust device in this embodiment also includes a guide ring 70 connected to the intake end 61. The guide ring 70 is coaxially disposed below the crucible 20 and communicates with the intake end 61 of the guide pipe 60. The guide ring 70 has a guide channel 74 that guides the air from below the crucible 20 to the intake end 61.

[0044] The guide ring 70 in this embodiment is preferably hollow, with a hollow annular chamber 71 inside. Multiple first air guide holes 72 are provided on the top end face of the guide ring 70, communicating with the annular chamber 71, making the guide ring 70 porous. A second air guide hole 73 is provided on the bottom end face of the guide ring 70, communicating with the suction end 61 of the guide pipe 60. The first air guide holes 72, the annular chamber 71, and the second air guide holes 73 form the aforementioned guide channel 74. The connection between the guide ring 70 and the suction end 61 allows the guide ring 70 to rise and fall synchronously with the suction end 61, thereby allowing synchronous rise and fall with the crucible 20. This guide ring 70 not only fills the empty area between the crucible 20 and the bottom of the furnace body 10, but also, in conjunction with its porous structure, effectively reduces the probability of cyclone formation, improving the problem of SiO discharge obstruction. It should be noted that the guide ring 70 in some embodiments can also be designed as a trumpet shape or other existing guide structure shapes as needed.

[0045] In this embodiment, the top end face and the bottom end face of the guide ring 70 are preferably concave downwards. The shape of this concavity can guide SiO to enter the guide pipe 60 sequentially through the first air guide hole 72, the annular chamber 71 and the second air guide hole 73, thereby changing the flow path of SiO and further reducing the probability of airflow generating cyclones in the blank area.

[0046] See details Figure 2 and Figure 6The exhaust device in this embodiment also includes a lifting rod 90 and a driver for driving the lifting rod 90 to rise and fall. The top of the lifting rod 90 is fixedly connected to the end face of the bottom of the guide ring 70, and the bottom of the lifting rod 90 movably extends through the bottom of the furnace body 10 to below the furnace body 10, so that the bottom of the lifting rod 90 can be connected to the driver for driving the lifting rod 90 to rise and fall. The driver drives the lifting rod 90 to rise and fall, and the lifting rod 90 is connected to the end face of the bottom of the guide ring 70, thereby driving the guide ring 70 to rise and fall. The bottom end of the guide ring 70 is connected to the suction end 61, thereby driving the suction end 61 to rise and fall. The driver for driving the suction end 61 to rise and fall and the driving component for driving the crucible 20 to rise and fall can come from the same power source, which can reduce costs. In some embodiments, a separate power source can also be set to drive the suction end 61 to rise and fall as needed. The number of lifting rods 90 can be set as needed. In this embodiment, two lifting rods 90 are specifically set, and the two lifting rods 90 are distributed on opposite sides of the guide ring 70 to ensure that the guide ring 70 rises and falls smoothly.

[0047] See details Figure 1 and Figure 5 The single crystal furnace in this embodiment also includes a heater 30 surrounding the crucible 20 and a heat insulation cylinder 50 disposed below the heater 30. The thickened heat insulation cylinder 50 not only improves the heat insulation effect and reduces heat loss within the single crystal furnace, but also fills more of the empty area between the bottom of the crucible 20 and the bottom of the furnace body 10, thereby reducing the probability of airflow generating vortices in the empty area. Preferably, the inner diameter of the heat insulation cylinder 50 is smaller than the inner diameter of the support leg 31 of the heater 30. A notch 51 is provided inside the heat insulation cylinder 50 to allow the support leg 31 to pass through, thus preventing interference between the heat insulation cylinder 50 and the heater 30. The inward thickening of the heat insulation cylinder 50 further reduces the space below the crucible, further weakening the airflow vortices generated in the space below the crucible.

[0048] In the single-crystal silicon rod preparation process of this embodiment, as the molten silicon level gradually decreases due to crystal growth, the driving component raises the quartz crucible 20 via the lifting shaft 40 to maintain the stability of the solid-liquid interface. The lifting rod 90 drives the guide ring 70 and the suction end 61 to rise synchronously, ensuring that the suction end 61 of the guide pipe 60 and the crucible 20 maintain a constant distance at all times. For details of this process, please refer to... Figure 7Inert gas is injected from the top of the furnace body 10. Under the action of the suction device at the bottom of the furnace body 10, the inert gas forms a directional airflow. This airflow carries the gaseous SiO generated by the reaction on the surface of the silicon material and enters the suction end 61 under the action of the guide ring 70. Under the action of the guide pipe 60, it enters the vacuum system from the exhaust end 62 and is discharged from the furnace body 10. The inert gas flow first carries the gaseous SiO and transfers it along the surface of the liquid to the edge of the opening of the crucible 20. Then it goes down along the outer wall of the crucible 20 to the bottom of the crucible 20. Then it is guided by the guide ring 70 and the guide pipe 60 through the exhaust port 11 and finally discharged by the suction device.

[0049] Because an exhaust device is added below the crucible 20 in this embodiment, the distance between the edge of the crucible 20 opening and the suction end 61 of the exhaust device remains constant. Firstly, this effectively shortens the path of SiO from the bottom of the crucible 20 to the exhaust device. Secondly, it fills the blank area between the bottom of the crucible 20 and the bottom of the furnace body 10, thereby improving the probability of airflow forming vortices in the blank area. Thirdly, it guides the discharge path of SiO from the bottom of the crucible 20 to the bottom of the furnace, avoiding the formation of vortices below the crucible 20, thereby accelerating the discharge speed of SiO and improving the problem of oxygen content in the single crystal silicon rod warping due to obstructed SiO discharge.

[0050] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0051] The embodiments described above are merely illustrative of several implementations of this utility model, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the utility model patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this utility model, and these all fall within the protection scope of this utility model. Therefore, the protection scope of this utility model patent should be determined by the appended claims.

Claims

1. A single crystal furnace, characterized in that, include: Furnace body (10); The crucible (20) is vertically and retractably installed inside the furnace body (10); An exhaust device is provided below the crucible (20), including an intake end (61) and an exhaust end (62) located below the intake end (61). The intake end (61) is located inside the furnace body (10), and the exhaust end (62) is connected to a vacuum system (80) outside the furnace body (10). At least the intake end (61) moves up and down synchronously with the crucible (20).

2. The single crystal furnace according to claim 1, characterized in that, The exhaust device includes a vertically arranged guide pipe (60), the upper end of which is the intake end (61) and the lower end of which is the exhaust end (62).

3. The single crystal furnace according to claim 1, characterized in that, The exhaust end (62) is connected to the evacuation system (80) outside the furnace body (10) through the exhaust port (11) opened at the bottom of the furnace body (10).

4. The single crystal furnace according to any one of claims 1-3, characterized in that: The exhaust device also includes a guide ring (70) connected to the intake end (61), the guide ring (70) having a guide channel (74) that guides the air from below the crucible (20) to the intake end (61).

5. The single crystal furnace according to claim 4, characterized in that: The guide ring (70) has a hollow annular chamber (71) inside. The top end face of the guide ring (70) is provided with a plurality of first air guide holes (72) communicating with the annular chamber (71). The bottom end face of the guide ring (70) is provided with a second air guide hole (73) communicating with the air intake end (61). The first air guide holes (72), the annular chamber (71), and the second air guide holes (73) form the guide channel (74).

6. The single crystal furnace according to claim 5, characterized in that: The top end face and the bottom end face of the guide ring (70) are recessed downwards.

7. The single crystal furnace according to claim 4, characterized in that: The exhaust device also includes a liftable lifting rod (90) and a driver for driving the lifting rod (90) to rise and fall. The top of the lifting rod (90) is connected to the end face of the bottom of the guide ring (70), and the bottom of the lifting rod (90) is movable through the bottom of the furnace body (10) and extends out of the furnace body (10) to be connected to the driver.

8. The single crystal furnace according to claim 2, characterized in that, The exhaust end (62) and the intake end (61) can be raised and lowered synchronously.

9. The single crystal furnace according to claim 2, characterized in that, The exhaust end (62) is fixed and the guide pipe (60) is retractable.

10. The single crystal furnace according to any one of claims 1-3, characterized in that: It also includes a heater (30) and a heat insulation cylinder (50), wherein the heater (30) is arranged around the outer periphery of the crucible (20), and the heat insulation cylinder (50) is arranged below the heater (30); The inner diameter of the insulation cylinder (50) is smaller than the outer diameter of the support leg (31) of the heater (30), and the insulation cylinder (50) has a notch (51) for the support leg (31) to pass through.

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