Czochralski crystal growing furnace feeding system

Abstract

The invention discloses a Czochralski single crystal furnace feeding system in the field of Czochralski single crystal manufacturing, and aims to solve the technical problem of temperature difference between the inside and the outside of a double-layer crucible caused by continuous feeding during continuous Czochralski single crystal. The system comprises a furnace body and a silicon material feeding device located outside the furnace body, and the silicon material feeding device penetrates through and extends into the furnace body through a discharging pipeline; a double-layer crucible is mounted in the furnace body, a guide cylinder is arranged right above the double-layer crucible, and the guide cylinder is fixed at the top in the furnace body; the double-layer crucible comprises an outer-layer crucible and an inner-layer crucible, and a feeding interlayer is formed between the outer-layer crucible and the inner-layer crucible; the discharging pipeline is provided with a discharging opening, and the discharging opening corresponds to an opening of the feeding interlayer. And the silicon material feeding device is provided with a plurality of microwave heating devices for heating the granular silicon passing through the microwave heating devices, so that the temperature difference between the granular silicon and the silicon liquid in the double-layer crucible is reduced. The damage rate of the inner-layer crucible can be reduced, and the temperature gradient of the silicon rod is avoided.

Description

TECHNICAL FIELD

[0001] The present application relates to a kind of straight pull single crystal furnace feeding system, belongs to straight pull single crystal manufacturing technical field. BACKGROUND

[0002] In the field of straight pull single crystal manufacturing, granular polysilicon is widely used in the feeding process as raw material. However, when adding granular silicon to the molten silicon liquid, there is a significant temperature difference between the two, which can easily cause thermal shock. This thermal shock not only causes the silicon liquid to splash, increasing the risk of impurity introduction, but also forms a large temperature gradient between the inner and outer layers of the double-layer crucible, affecting the stability of the thermal field. Excessive temperature difference can exacerbate the thermal stress of the inner crucible, leading to an increase in the breakage rate of the crucible, and may also cause the lower temperature silicon liquid in the outer layer to enter the inner layer, further causing uneven temperature of the inner silicon liquid, ultimately affecting the quality of the single crystal silicon rod, forming lattice defects or crystal breakage.

[0003] In the prior art, microwave radiation is often used to heat granular polysilicon or through high-temperature pyrolysis and ozone oxidation to reduce the carbon content in granular silicon. The former takes advantage of the difference in microwave absorption capacity between micro-nano silicon powder and larger particles, making the micro-silicon powder more easily melt and adhere to the surface of the larger particles, thereby reducing dust scattering. This process is usually carried out in a vacuum or inert atmosphere, and by controlling the microwave power and heating rate, the turbidity of the silicon material can be effectively reduced at lower energy consumption. The latter uses microwave heating to create micro-cracks in granular silicon, exposing internal carbon impurities, which then react with ozone gas to reduce carbon impurity content to a lower level, avoiding oxidation of the silicon material and improving the purity of the final product.

[0004] Although the above technologies have advantages in dust removal and impurity removal, they do not effectively solve the problems of thermal shock, crucible life, and single crystal growth quality stability caused by excessive temperature difference between granular silicon and molten silicon liquid during continuous feeding. Therefore, there is still a need for a feeding system solution that can effectively regulate the temperature difference, improve the thermal field distribution, and thus improve the efficiency of crystal pulling and the quality of silicon rods. SUMMARY

[0005] The purpose of the present application is to provide a straight pull single crystal furnace feeding system that can reduce the breakage rate of the inner crucible and avoid the generation of temperature gradient in the silicon rod, improving the quality of crystal pulling.

[0006] To solve the above technical problems, the present application is implemented by using the following technical solutions.

[0007] On the one hand, the present application provides a straight pull single crystal furnace feeding system, which includes a furnace body and a silicon material feeding device located outside the furnace body. The silicon material feeding device extends through a feeding pipe to the inside of the furnace body. The furnace body is internally provided with a double-layered crucible, the top of the double-layered crucible is provided with a flow guide cylinder, and the flow guide cylinder is fixed to the top of the furnace body; the double-layered crucible comprises an outer-layered crucible and an inner-layered crucible, and a feeding interlayer is formed between the outer-layered crucible and the inner-layered crucible; the discharging pipeline is provided with a discharging opening, and the discharging opening corresponds to the opening of the feeding interlayer. The silicon material feeding device is provided with a plurality of microwave heating devices to heat the granular silicon passing through the microwave heating devices, so as to reduce the temperature difference between the granular silicon and the silicon liquid in the double-layered crucible.

[0008] Preferably, the double-layered crucible is provided below with a supporting structure, the supporting structure comprises in sequence from top to bottom a graphite heating body, a tray and a drag rod, the top end of the drag rod supports the tray, and the graphite heating body is installed on the tray.

[0009] Preferably, one end of the drag rod is connected to the tray, and the other end penetrates through the bottom of the furnace body.

[0010] Preferably, the outer periphery of the double-layered crucible is further provided with a heater, the heater is connected with a heating electrode, the heating electrode penetrates through the bottom of the furnace body and is connected with a power supply outside the furnace body.

[0011] Preferably, the double-layered crucible and the heater are both cylindrical structures.

[0012] Preferably, the outer periphery of the opening end of the flow guide cylinder is surrounded by a reverse-docking flow guide cover.

[0013] Preferably, the top of the flow guide cylinder is provided with a stretching device for stretching the silicon liquid in the inner-layered crucible to form a single crystal silicon rod, the stretching device is provided with an inert gas inlet, and the inert gas inlet is connected to an inert gas source. The inert gas source enters the flow guide cylinder through the stretching device and moves towards the inner-layered crucible under the guidance of the flow guide cover.

[0014] Preferably, the side of the furnace body is provided below with an inert gas suction port, and the inert gas suction port is connected with a negative pressure device.

[0015] Preferably, the inner wall of the furnace body is provided with a heat preservation layer, and the bottom of the furnace body is provided with a reflection layer.

[0016] Preferably, the radiation heating power of the microwave heating device is 500-5000W, and the temperature rising rate of the microwave heating device is 25-250℃ / min.

[0017] Compared with the prior art, the present application has the following beneficial effects: The present application preheats the granular silicon before it enters the double-layer crucible, and the granular silicon is quickly and uniformly heated by the microwave heating mode, effectively reducing the temperature difference between the granular silicon and the silicon liquid in the double-layer crucible, thereby significantly reducing the thermal shock to the crucible during the feeding process, avoiding damage to the inner layer crucible due to excessive temperature difference, and at the same time inhibiting the temperature gradient caused by the entry of the outer layer silicon liquid into the inner layer, ultimately improving the drawing quality and yield of the single crystal silicon rod, and having good industrial application prospect, and the opening of the feeding nozzle corresponds to the opening of the feeding interlayer, realizing accurate feeding of the granular silicon. BRIEF DESCRIPTION OF DRAWINGS

[0018] Figure 1 Fig. 1 is a structural schematic diagram of a feeding system of a Czochralski furnace provided by an embodiment of the present application; In the figure: 1, furnace body; 2, double-layer crucible; 201, outer layer crucible; 202, inner layer crucible; 203, feeding interlayer; 3, graphite heating body; 4, tray; 5, drag rod; 6, flow guide cylinder; 7, flow guide cover; 8, feeding and silicon adding device; 9, stretching device; 10, inert gas inlet; 11, heat preservation layer; 12, reflection layer; 13, heater; 14, inert gas outlet; 15, microwave heating device; 16, heating electrode; 17, discharging pipeline; 18, discharging port. DETAILED DESCRIPTION

[0019] The technical scheme of the present application will be described in detail below by means of the accompanying drawings and specific embodiments, and it should be understood that the specific features in the embodiments and the specific embodiments are detailed descriptions of the technical scheme of the present application, and are not limitations of the technical scheme of the present application. In the case of no conflict, the technical features in the embodiments and the specific embodiments can be combined with each other.

[0020] The term "and / or", only describes the association relationship of the associated objects, which means that there can be three kinds of relationships, for example, A and / or B, which can represent the three cases of A alone, A and B together, and B alone. In addition, the character " / ", generally represents that the associated objects before and after are in an "or" relationship. Embodiment 1

[0021] Reference Figure 1The embodiment introduces a feeding system of a Czochralski furnace, which comprises a furnace body 1 and a silicon material feeding device 8 located outside the furnace body 1. The silicon material feeding device 8 extends through a feeding pipe 17 to the inside of the furnace body 1. The inside of the furnace body 1 is configured with a double-layer crucible 2 in a cylindrical structure, which comprises an outer layer crucible 201 and an inner layer crucible 202, and a feeding interlayer 203 for receiving granular silicon is formed between the two. The feeding pipe 17 is provided with a feeding opening 18, and the outlet end of the feeding opening 18 corresponds to the opening (feeding port) of the feeding interlayer 203, so that the granular silicon can be accurately fed into the feeding interlayer 203, which temporarily stores or guides the granular silicon into the inner layer crucible 202. The whole conveying process is controlled by the valve provided on the feeding pipe 17, so as to ensure that the amount of granular silicon added is controllable and stable.

[0022] To further optimize the process effect, a plurality of microwave heating devices 15 are integrated at the silicon material feeding device 8, so as to preheat the granular silicon before it enters the double-layer crucible 2 (microwave radiation heating power is 100-6000 W, and the temperature rising rate is 5-300 ℃ / min). The preheating process effectively reduces the temperature difference between the solid granular silicon and the existing molten silicon liquid in the double-layer crucible 2, thereby reducing the thermal shock in the feeding process, stabilizing the thermal field environment, and helping to improve the growth quality of the single crystal silicon rod and prolong the service life of the crucible. Embodiment 2

[0023] Referring to Figure 1 On the basis of embodiment 1, the feeding system of the Czochralski furnace is further refined, and the specific implementation is as follows: A support structure is arranged below the double-layer crucible 2, which comprises a graphite heating body 3, a tray 4 and a drag rod 5 from top to bottom in sequence. The top end of the drag rod 5 supports the tray 4, and the graphite heating body 3 is installed on the tray 4 and directly acts on the bottom of the double-layer crucible 2, which not only plays a supporting role, but also provides a heat source.

[0024] In a further embodiment of the present application, one end of the drag rod 5 is connected to and supports the tray 4, and the other end is arranged through the bottom of the furnace body 1 and connected to an external lifting mechanism. The lifting mechanism controls the lifting of the drag rod 5, so as to adjust the height of the double-layer crucible 2 in the furnace body 1, and ensure that it is in the best heating zone. A heater 13 with the same shape (cylindrical shape) as the double-layer crucible 2 is arranged on the outer periphery of the double-layer crucible 2. The heater 13 is connected with a heating electrode 16, the heating electrode 16 penetrates through the bottom of the furnace body 1 and is connected with a power supply outside the furnace body 1, so as to realize auxiliary and uniform heating of the double-layer crucible 2.

[0025] In further embodiments of the application, a flow guide cylinder 6 is arranged directly above the double-layer crucible 2, the flow guide cylinder 6 is fixed at a top position in the furnace body 1, and a flow guide cover 7 with a reverse joint is further arranged around the open end of the flow guide cylinder 6. A stretching device 9 is arranged above the flow guide cylinder 6 for stretching the silicon liquid in the inner-layer crucible 202 to form a single crystal silicon rod. The stretching device 9 is provided with an inert gas inlet 10 connected to an inert gas source. In actual operation, the inert gas source enters the stretching device 9 from the inert gas inlet 1, is guided downward by the stretching device 9 into the flow guide cylinder 6, and is guided by the flow guide cover 7 to move along the direction of the inner-layer crucible 202, thereby effectively inhibiting the upward diffusion of the inert gas, continuously flushing the surface of the growing single crystal silicon rod to remove volatile impurities such as silicon oxide and reduce crystal defects.

[0026] In order to further control the atmosphere in the furnace, an inert gas suction port 14 is arranged below the bottom side of the furnace body 1, which is connected to a negative pressure device for discharging the inert gas in the furnace body 1.

[0027] In order to improve the efficiency of the thermal field, a heat preservation layer 11 is arranged on the inner wall of the furnace body 1, and a reflective layer 12 is arranged at the bottom, which together reduces heat loss and maintains a stable high temperature environment.

[0028] In further embodiments of the application, a plurality of downward microwave heating devices 15, preferably two, are arranged at the upper part of the silicon material feeding device 8, and a plurality of upward microwave heating devices 15, preferably two, are arranged at the lower part. In actual work, the granular silicon passes through the channel formed between the upper and lower groups of microwave heating devices 15. This opposite arrangement allows the granular silicon to be uniformly irradiated by microwaves from different directions while moving, thereby achieving rapid and uniform preheating. By arranging multiple microwave heating devices 15, the power of a single microwave heating device 15 is reduced, and the microwave heating is more uniform. The preferred heating power is set to 500-5000W, and the heating rate is set to 25-250℃ / min.

[0029] The embodiments of the application are described above in conjunction with the drawings, but the application is not limited to the specific embodiments described above, which are only illustrative and not limiting. Those skilled in the art can make many forms under the inspiration of the application without departing from the purpose of the application and the scope protected by the claims. These are all within the protection of the application.

Claims

1. A feeding system for a Czochralski single crystal furnace, characterized in that, It includes a furnace body (1) and a silicon material feeding device (8) located outside the furnace body (1), the silicon material feeding device (8) extending through a feeding pipe (17) into the interior of the furnace body (1); The furnace body (1) is equipped with a double-layer crucible (2), and a guide tube (6) is provided directly above the double-layer crucible (2). The guide tube (6) is fixed to the top of the furnace body (1). The double-layer crucible (2) includes an outer crucible (201) and an inner crucible (202). A feeding jacket (203) is formed between the outer crucible (201) and the inner crucible (202). The feeding pipe (17) is provided with a feeding port (18), which corresponds to the opening of the feeding jacket (203). The silicon material feeding device (8) is equipped with multiple microwave heating devices (15) to heat the granular silicon passing through the microwave heating devices (15), thereby reducing the temperature difference between the granular silicon and the silicon liquid in the double-layer crucible (2).

2. The feeding system for the Czochralski single crystal furnace according to claim 1, characterized in that, The double-layer crucible (2) is provided with a support structure below it. The support structure includes a graphite heating element (3), a tray (4) and a drag rod (5) from top to bottom. The top of the drag rod (5) supports the tray (4), and the graphite heating element (3) is installed on the tray (4).

3. The feeding system for the Czochralski single crystal furnace according to claim 2, characterized in that, One end of the drag bar (5) is connected to the tray (4), and the other end is disposed at the bottom of the furnace body (1).

4. The feeding system for a Czochralski single crystal furnace according to claim 1, characterized in that, A heater (13) is also provided on the outer periphery of the double-layer crucible (2). The heater (13) is connected to a heating electrode (16). The heating electrode (16) penetrates the bottom of the furnace body (1) and is connected to a power source outside the furnace body (1).

5. The feeding system for a Czochralski single crystal furnace according to claim 4, characterized in that, Both the double-layer crucible (2) and the heater (13) are cylindrical structures.

6. The feeding system for a Czochralski single crystal furnace according to claim 1, characterized in that, The outer periphery of the opening end of the guide tube (6) is provided with an inverted guide shroud (7).

7. The Czochralski single crystal furnace feeding system according to claim 6, characterized in that, Above the guide tube is a stretching device (9) for stretching the molten silicon in the inner crucible (202) to form a single crystal silicon rod. The stretching device (9) is provided with an inert gas inlet (10), which is connected to an inert gas source. The inert gas source enters the guide tube (6) through the stretching device (9) and moves toward the inner crucible (202) under the guidance of the guide hood (7).

8. The feeding system for a Czochralski single crystal furnace according to claim 1, characterized in that, An inert gas intake port (14) is provided on the lower side of the furnace body (1), and the inert gas intake port (14) is connected to a negative pressure device.

9. The feeding system for a Czochralski single crystal furnace according to claim 1, characterized in that, The furnace body (1) has an insulation layer (11) on its inner wall and a reflective layer (12) at its bottom.

10. The Czochralski single crystal furnace feeding system according to claim 1, characterized in that, The microwave heating device has a radiation heating power of 500-5000W and a heating rate of 25-250℃ / min.

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