Electronic-grade polycrystalline silicon reduction furnace capable of feeding air in surrounding manner

Abstract

The electronic-grade polycrystalline silicon reduction furnace comprises a furnace barrel, a chassis and a support platform, the furnace barrel is a jacketed furnace barrel, a cooling water inlet is formed in the side wall of the bottom of the jacketed furnace barrel, and a cooling water outlet is formed in the side wall, close to the top, of the jacketed furnace barrel; a plurality of vertically-arranged air inlet branch pipes are evenly arranged in an interlayer of the jacket type furnace barrel in the circumferential direction. And the air inlet end of the air inlet nozzle hermetically penetrates through the inner layer of the jacketed furnace barrel and is hermetically connected with the communicating port. The invention has the advantages that the plurality of air inlet nozzles are arranged on the upper air inlet branch pipe from top to bottom, so that material feeding air flow can be formed in the furnace barrel from top to bottom at the full height, the flow field of a top sealing head area of the reduction furnace can be effectively improved, the upper part of a silicon rod and the surface of the cross beam can be scoured and disturbed by gas at a certain flow speed, and the phenomenon of popcorn can be reduced and even avoided; and meanwhile, the problems of overhigh temperature and small flow speed of the upper space in the furnace caused by a traditional lower air inlet mode can be solved, and the conversion rate is increased.

Description

Technical Field

[0001] The present invention relates to the field of polysilicon preparation, and particularly to an electronic-grade polysilicon reduction furnace with circumferential air intake. Background Art

[0002] The bell-jar reduction furnace is the core equipment for preparing crystalline silicon by the improved Siemens method. Its working principle is that the silicon core installed on the chassis generates heat through resistance, and the raw material gases SiHCl3 and H2 undergo a chemical vapor deposition reaction on the surface of the electrically heated silicon core to form polysilicon rods. The traditional polysilicon reduction furnace uses a bottom-inlet and bottom-outlet method, that is, several air inlets are opened on the chassis, and the air inlets are arranged on the chassis at equal distances and equal radii in a concentric circle manner. SiHCl3 and H2 are mixed, preheated and then sent into the reduction furnace through the above air inlets. After a series of chemical reactions, the reaction tail gas flows out from several air outlets opened on the chassis. In addition to the inlet and outlet ports, several pairs of electrode holes are also opened on the chassis.

[0003] However, due to the limitations of its own structure, the traditional polysilicon reduction furnace with a bottom-outlet method has unreasonable flow fields and thermal fields in the upper space of the reduction furnace, resulting in serious "popcorn" phenomena in the upper part of the silicon rod. In severe cases, a large amount of amorphous silicon powder will be generated during gas-phase decomposition, causing waste of raw materials, increasing the operation difficulty, affecting the appearance and quality of the silicon rod. Therefore, it cannot meet the higher requirements of high-purity polysilicon in terms of purity, density, surface morphology, cleanliness, and the small proportion of abnormal materials such as cauliflower materials.

[0004] Chinese Patent with application number: CN202211249262.2 and title: A polysilicon reduction furnace growth system discloses a solution to the above problems: by designing rotating upper and lower electrodes, the silicon rod rotates during growth. The upper electrode is located at the top of the furnace body, the lower electrode is located at the bottom of the furnace body, the upper electrode and the lower electrode are arranged opposite to each other, and both the upper electrode and the lower electrode are rotatably connected to the furnace body. The silicon core is installed between the upper electrode and the lower electrode, and the upper electrode and the lower electrode can drive the silicon core to rotate. To a certain extent, it solves the problems of the silicon rod having yin-yang surfaces, pits, and being prone to growing cauliflower materials at the crossbeam due to uneven temperature and flow field distributions in the furnace. However, due to the complex equipment, precise control is required, the rotating airflow is affected by changes in the furnace, and due to the large cost investment and high operation requirements, there is still a risk of generating cauliflower materials. Therefore, it is difficult to completely solve the above quality problems. At the same time, the increased metal equipment and lubricating media in the furnace greatly increase the possibility of metal pollution and C pollution, and cannot meet the requirements for product quality of electronic-grade polysilicon.

[0005] The Chinese patent with the application number CN201420221899.5 and the name "A novel polycrystalline silicon reduction furnace with inlet and outlet gas structures" discloses a reduction furnace with simultaneous upper and lower gas inlet. Its top inlet pipe enters the furnace body through a head; the bottom inlet pipe is connected to an inlet small pipe, and the inlet small pipe enters the furnace body through the chassis. This gas inlet method makes the gas flow field distribution in the reduction furnace more uniform, which is beneficial to the gas reaction to generate silicon rods and can improve the silicon rod growth efficiency to a certain extent; however, the upper gas inlet method using a head connection makes the reduction furnace and the upper gas inlet pipeline in an open state, and the reduction furnace will be polluted by the external environment during the furnace starting process and cannot meet the quality requirements either. Summary of the Invention

[0006] To solve the above problems, the purpose of the present invention is to provide an electron-grade polycrystalline silicon reduction furnace with circumferential gas inlet, which is mainly applicable to the improved Siemens method (CVD for producing polycrystalline silicon). The present invention is implemented by the following technical solutions: An electron-grade polycrystalline silicon reduction furnace with circumferential gas inlet, including a furnace barrel, a chassis and a support platform. The horizontally arranged chassis is fixed on the support platform. During production, the bottom end of the furnace barrel is hermetically and openably fixedly connected to the chassis; when the product is taken out of the furnace, the furnace barrel and the chassis can be separated. A number of pairs of electrodes are arranged on the chassis, and detachable graphite chucks are connected to each pair of electrodes. Silicon cores can be inserted into the graphite chucks; a number of tail gas holes are opened on the chassis, and the tail gas holes are hermetically connected to a tail gas branch pipe placed outside the furnace barrel, and the tail gas branch pipe is hermetically connected to a tail gas main pipe. A nitrogen inlet and a nitrogen outlet communicating with the inside of the furnace barrel are respectively opened on the side wall of the furnace barrel. The furnace barrel is a jacketed furnace barrel. A cooling water inlet is opened on the bottom side wall of the jacketed furnace barrel, and a cooling water outlet is opened on the side wall of the jacketed furnace barrel near the top. A number of vertically arranged inlet branch pipes are uniformly arranged in the circumferential direction in the interlayer of the jacketed furnace barrel; the top end of the inlet branch pipe is a closed structure and extends to the upper part of the jacketed furnace barrel; the bottom end of the inlet branch pipe hermetically passes through the chassis and is hermetically communicated with an inlet main pipe placed outside the jacketed furnace barrel. A plurality of communication ports are uniformly opened on each inlet branch pipe in the interlayer of the jacketed furnace barrel from top to bottom, and a number of inlet nozzles equal to the number of the communication ports are arranged in the jacketed furnace barrel. The inlet end of the inlet nozzle hermetically passes through the inner layer of the jacketed furnace barrel and is hermetically connected to the communication port.

[0007] Further, each of the intake branch pipes includes an upper intake branch pipe and a lower intake branch pipe; the upper intake branch pipe is placed inside the sandwich layer of the jacketed furnace barrel, and has a structure with a closed top end and an open bottom end; the lower intake branch pipe is placed outside the jacketed furnace barrel and has a structure with both ends open; On the chassis, branch pipe connection ports equal in number to the intake branch pipes are provided, and the bottom end of the upper intake branch pipe and the top end of the lower intake branch pipe are respectively and hermetically connected to the upper end and the lower end of the branch pipe connection port.

[0008] Further, an intake flow regulating valve is provided on each of the lower intake branch pipes.

[0009] Further, the number of the intake branch pipes is half of the number of electrode pairs located on the outer circle.

[0010] Further, the number of pairs of the electrodes is 12 to 60 pairs.

[0011] Further, an observation eyepiece is provided on the side wall of the jacketed furnace barrel.

[0012] Further, the chassis is of a hollow structure, and a water inlet and a water outlet are respectively provided on the chassis.

[0013] Further, the gas outlet end of the intake nozzle is of a reduced diameter structure.

[0014] Advantages of the present invention: By arranging a plurality of intake nozzles from top to bottom on the upper intake branch pipe, the present invention can enable there to be a material feeding air flow throughout the entire height from top to bottom inside the furnace barrel, effectively improve the flow field in the top head region of the reduction furnace, enable the upper part of the silicon rod and the surface of the cross beam to be scoured and disturbed by a gas with a certain flow rate, reduce or even avoid the occurrence of the "popcorn" phenomenon; at the same time, it can also solve the problems of too high temperature and too small flow rate in the upper space inside the furnace caused by the traditional lower intake method, weaken the generation conditions of amorphous silicon powder, and improve the conversion rate; moreover, the temperature inside the furnace is uniform up and down, avoiding the continuous supply of high current to ensure the temperature in the low temperature region, reducing energy waste, effectively reducing the power consumption of the reduction furnace, and reducing costs; in addition, the upper intake branch pipe located inside the jacket is surrounded by high-temperature cooling water, which can preheat the mixed gas entering the furnace, fully gasify the gas entering the furnace, improve the contact efficiency between the gas and the silicon core, and promote the progress of the chemical vapor deposition reaction; since the upper intake branch pipe is surrounded by cooling water, it can also effectively prevent the high temperature from damaging the intake pipeline and extend the service life of the equipment. Description of the drawings

[0015] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the accompanying drawings required for the description of the embodiments or the prior art. Obviously, the accompanying drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other accompanying drawings can be obtained based on these drawings.

[0016] Figure 1 is the structural schematic diagram of this embodiment; Figure 2 is the structural schematic diagram of the chassis in this embodiment.

[0017] In the figure: furnace barrel 1, chassis 2, support platform 3, electrode 4, U-shaped silicon core 5, tail gas hole 6, tail gas branch pipe 7, tail gas main pipe 8, nitrogen inlet 9, nitrogen outlet 10, cooling water inlet 11, cooling water outlet 12, intake branch pipe 13, upper intake branch pipe 131, lower intake branch pipe 132, intake main pipe 14, intake nozzle 15, branch pipe connection port 16, intake flow regulating valve 17, observation eyepiece 18, water inlet 19, water outlet 20. Detailed implementation manners

[0018] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, rather than all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0019] Embodiment 1: As Figure 1 、 Figure 2 shown, an electronic-grade polysilicon reduction furnace with circumferential intake air includes a furnace barrel 1, a chassis 2, and a support platform 3. The horizontally arranged chassis 2 is fixed on the support platform 3, and the bottom end of the furnace barrel 1 is hermetically and fixedly connected to the chassis 2; the chassis 2 is a hollow structure, and a water inlet 19 and a water outlet 20 are respectively opened on the chassis 2, and cooling water is passed through to cool the chassis 2.

[0020] A number of pairs of electrodes 4 are arranged on the chassis 2, and the number of pairs of electrodes 4 can be 12 pairs, 18 pairs, 36 pairs, 40 pairs, 54 pairs, 60 pairs, etc. A U-shaped silicon core 5 is inserted on each pair of electrodes 4 to form a closed loop; a number of tail gas holes 6 are opened on the chassis 2, and the tail gas holes 6 are hermetically connected to a tail gas branch pipe 7 placed outside the furnace barrel 1, and the tail gas branch pipe 7 is hermetically connected to a tail gas main pipe 8; On the side wall of the furnace barrel 1, a nitrogen inlet 9 and a nitrogen outlet 10 communicating with the inside of the furnace barrel 1 are respectively provided, through which high-purity nitrogen can be sent into the furnace barrel 1 for replacing the gas in the furnace (discharging the air to ensure product quality); on the side wall in the middle of the jacketed furnace barrel 1, an observation eyepiece 18 is provided for observing the growth situation in the furnace.

[0021] The furnace barrel 1 is a jacketed furnace barrel 1. A cooling water inlet 11 is provided on the bottom side wall of the jacketed furnace barrel 1, and a cooling water outlet 12 is provided on the side wall near the top of the jacketed furnace barrel 1. Cooling water is passed through to cool the furnace barrel 1. In the interlayer of the jacketed furnace barrel 1, a number of vertically arranged intake branch pipes 13 are evenly arranged in the circumferential direction. The number of intake branch pipes 13 is half of the number of pairs of electrodes 4 located in the outer ring; the top end of the intake branch pipe 13 is a closed structure and extends to the upper part of the jacketed furnace barrel 1; the bottom end of the intake branch pipe 13 is sealed through the chassis 2 and is hermetically connected to an intake main pipe 14 placed outside the jacketed furnace barrel 1. On each intake branch pipe 13 in the interlayer of the jacketed furnace barrel 1, a plurality of communication ports are evenly opened from top to bottom, preferably 2 to 4; in the furnace barrel 1, a number of intake nozzles 15 equal to the number of communication ports are provided. The intake end of the intake nozzle 15 is sealed through the inner layer of the jacketed furnace barrel 1 and is hermetically connected to the communication port. The outlet end of the intake nozzle 15 is a constricted structure, which can increase the flow rate of the gas when it is ejected, make the gas jet farther, ensure a more uniform flow field is formed in the furnace barrel 1, and further optimize the growth environment of the silicon rod. In this embodiment, each intake branch pipe 13 includes an upper intake branch pipe 131 and a lower intake branch pipe 132; the upper intake branch pipe 131 is placed in the interlayer of the jacketed furnace barrel 1 and has a closed top end and an open bottom end structure; the lower intake branch pipe 132 is placed outside the jacketed furnace barrel 1 and has an open structure at both ends; an intake flow regulating valve 17 is provided on each lower intake branch pipe 132.

[0022] On the chassis 2, branch pipe connection ports 16 equal in number to the intake branch pipes 13 are provided. The bottom end of the upper intake branch pipe 131 and the top end of the lower intake branch pipe 132 are respectively hermetically connected to the upper end and the lower end of the branch pipe connection port 16.

[0023] Working description: When using this embodiment, after the U-shaped silicon core 5 and the electrode 4 are installed and fixed, the furnace barrel 1 is covered on the chassis 2 and fastened and sealed. At the same time, both the upper intake branch pipe 131 and the lower intake branch pipe 132 are hermetically connected to the branch pipe connection port 16. Then, nitrogen is first introduced into the furnace barrel 1 to displace the air in the furnace barrel 1, and the displaced gas is discharged through the exhaust gas hole 6 opened on the chassis 2, through the exhaust gas branch pipe 7 and the exhaust gas main pipe 8; then a mixed gas of SiHCl3 and H2 is introduced. SiHCl3 and H2 enter the intake main pipe 14 through the mixer, then enter the lower intake branch pipe 132 and the upper intake branch pipe 131 in sequence, and finally SiHCl3 and H2 are sent into the furnace barrel 1 through the intake nozzle 15, and a chemical vapor deposition reaction occurs with the silicon core that is energized and heated, generating a silicon rod, and the tail gas is discharged through the exhaust gas hole 6, through the exhaust gas branch pipe 7 and the exhaust gas main pipe 8. At the same time, cooling water is introduced into both the jacket of the furnace barrel 1 and the chassis 2 to cool the side wall of the furnace barrel 1 and the heating parts such as the chassis 2, thereby taking away the heat in the furnace barrel 1 and preventing deposition due to temperature rise. At the same time, the growth situation of the silicon rod in the furnace barrel 1 is observed through the observation eyepiece 18, and the intake air volume and the current magnitude are adjusted.

[0024] In this embodiment, by arranging a plurality of intake nozzles 15 from top to bottom on the upper intake branch pipe 131, a material feeding air flow can be provided throughout the entire height from top to bottom in the furnace barrel 1, so that the raw material gas forms a surround around the silicon core from top to bottom, effectively avoiding the problems of too high temperature and too small flow rate in the upper space of the furnace barrel 1 caused by the traditional lower intake method, eliminating factors such as uneven temperature and uneven air flow in the furnace that are not conducive to the uniform deposition of the silicon rod, weakening the generation conditions of amorphous silicon powder, and improving the conversion rate. At the same time, with a stable temperature field and flow field, when formulating a polysilicon rod growth formula, more accurate current and voltage feedback can be provided, controlling the polysilicon growth rate and generating a more dense crystal structure, thereby increasing the yield. Moreover, the temperature in the furnace is uniform up and down, avoiding the continuous high current provided to ensure the temperature in the low-temperature area, reducing energy waste, effectively reducing the power consumption of the reduction furnace, and reducing costs.

[0025] The intake nozzle 15 located above blows the mixed gas of SiHCl3 and H2 into the furnace barrel 1 from above, which can improve the flow field in the top head area of the furnace barrel 1, enabling the upper part of the silicon rod and the surface of the cross beam to be scoured and disturbed by a gas flow with a certain flow rate, avoiding the occurrence of the "popcorn" phenomenon.

[0026] In addition, in this embodiment, the upper intake branch pipe 131 located in the jacket is surrounded by high-temperature cooling water, which can preheat the mixed gas entering the furnace, fully vaporize the gas entering the furnace, improve the contact efficiency between the gas and the silicon core, and promote the progress of the chemical vapor deposition reaction. At the same time, since the upper intake branch pipe 131 is surrounded by cooling water, it can also effectively prevent the damage of the intake pipeline by high temperature and extend the service life of the equipment.

[0027] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. An electronic-grade polysilicon reduction furnace with a circumferential intake, comprising a furnace cylinder, a chassis, and a support platform. The horizontally arranged chassis is fixedly mounted on the support platform, and the bottom end of the furnace cylinder is hermetically and fixedly connected to the chassis; A number of pairs of electrodes are provided on the chassis, and a U-shaped silicon core is inserted on each pair of electrodes; a number of tail gas holes are formed in the chassis, and the tail gas holes are hermetically connected to a tail gas branch pipe disposed outside the furnace cylinder, and the tail gas branch pipe is hermetically connected to a tail gas main pipe; A nitrogen inlet and a nitrogen outlet communicating with the interior of the furnace cylinder are respectively formed on the side wall of the furnace cylinder; Characterized in that, The furnace cylinder is a jacketed furnace cylinder, a cooling water inlet is formed on the bottom side wall of the jacketed furnace cylinder, and a cooling water outlet is formed on the side wall of the jacketed furnace cylinder near the top; A number of vertically arranged intake branch pipes are uniformly arranged circumferentially in the interlayer of the jacketed furnace cylinder; the top end of the intake branch pipe is a closed structure and extends to the upper part of the jacketed furnace cylinder; the bottom end of the intake branch pipe hermetically passes through the chassis and is hermetically communicated with an intake main pipe disposed outside the jacketed furnace cylinder; A plurality of communication ports are uniformly formed on each intake branch pipe in the interlayer of the jacketed furnace cylinder from top to bottom, and a number of intake nozzles equal to the number of the communication ports are provided in the jacketed furnace cylinder. The intake end of the intake nozzle hermetically passes through the inner layer of the jacketed furnace cylinder and is hermetically connected to the communication port.

2. The electronic grade polysilicon reduction furnace with a circumferential intake according to claim 1, wherein Each intake branch pipe comprises an upper intake branch pipe and a lower intake branch pipe; the upper intake branch pipe is disposed in the interlayer of the jacketed furnace cylinder and has a structure with a closed top end and an open bottom end; the lower intake branch pipe is disposed outside the jacketed furnace cylinder and has a structure with both ends open; Branch pipe connection ports equal to the number of the intake branch pipes are formed in the chassis, and the bottom end of the upper intake branch pipe and the top end of the lower intake branch pipe are respectively hermetically connected to the upper end and the lower end of the branch pipe connection port.

3. The electronic grade polysilicon reduction furnace with a surrounding air intake according to claim 2, characterized in that An intake flow regulating valve is provided on each lower intake branch pipe.

4. The electronic grade polysilicon reduction furnace with a surrounding air intake according to claim 1, characterized in that, The number of the intake branch pipes is half of the number of pairs of electrodes located on the outer circle.

5. The electronic-grade polysilicon reduction furnace with a surrounding air intake according to claim 1, characterized in that, The number of pairs of the electrodes is 12 to 60 pairs.

6. The electronic-grade polysilicon reduction furnace with a surrounding air intake according to claim 1, wherein, An observation eyepiece is provided on the side wall of the jacketed furnace cylinder.

7. The electronic grade polysilicon reduction furnace with a surrounding air intake according to claim 1, characterized in that, The chassis is a hollow structure, and a water inlet and a water outlet are respectively formed in the chassis.

8. The electronic grade polysilicon reduction furnace with circumferential intake according to claim 1, wherein, The air outlet end of the intake nozzle is a reduced diameter structure.

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