An electronic-grade polysilicon reduction furnace with surrounding air intake

Abstract

The present invention discloses an electronic-grade polysilicon reduction furnace with a surround-type air intake, comprising a furnace drum, a chassis, and a support platform. The furnace drum is a jacketed furnace drum, a cooling water inlet is provided on the bottom side wall of the jacketed furnace drum, and a cooling water outlet is provided on the side wall of the jacketed furnace drum near the top. A plurality of vertically arranged air intake branches are uniformly arranged along the circumference within the interlayer of the jacketed furnace drum. The air intake end of the air intake nozzle is sealed and passes through the inner layer of the jacketed furnace drum and is sealed and connected to the connecting port. Advantages: By arranging multiple air intake nozzles from top to bottom on the upper air intake branch pipe, a material feed airflow can be provided throughout the entire height of the furnace drum from top to bottom, which can effectively improve the flow field in the top head area of ​​the reduction furnace, and can subject the upper part of the silicon rod and the surface of the crossbeam to gas scouring disturbance at a certain flow rate, thereby reducing or even avoiding the occurrence of the "popcorn" phenomenon. At the same time, it can also solve the problems of excessively high temperature and low flow rate in the upper space of the furnace caused by the traditional bottom air intake method, thereby improving the conversion rate.

Description

Technical Field

[0001] The present invention relates to the field of polysilicon preparation, and in particular to an electronic-grade polysilicon reduction furnace with a surround-type air intake. Background Art

[0002] The bell-shaped reduction furnace is the core equipment for producing crystalline silicon using the modified Siemens process. Its operating principle is that the silicon core mounted on the chassis generates resistive heat, and the raw gas SiHCl3 and H2 undergo a chemical vapor deposition reaction on the electrically heated surface of the silicon core to form polycrystalline silicon rods. Traditional polysilicon reduction furnaces use a bottom-inlet and outlet method, with several air inlets arranged concentrically and equidistantly on the chassis. After mixing and preheating, the SiHCl3 and H2 are fed into the reduction furnace through these inlets. After a series of chemical reactions, the reaction exhaust flows out through several outlets on the chassis. In addition to the inlet and outlet ports, the chassis also features several paired electrode holes.

[0003] However, the traditional polysilicon reduction furnace using the bottom gas outlet method is limited by its own structure, which makes the flow field and thermal field in the upper space of the reduction furnace unreasonable, resulting in serious "popcorn" phenomenon on the upper part of the silicon rod. In severe cases, a large amount of amorphous silicon powder will be produced during gas phase decomposition, resulting in raw material waste, increasing operation difficulty, and affecting the appearance and quality of the silicon rod. Therefore, it cannot meet the higher requirements of high-purity polysilicon silicon material for purity, density, surface morphology, cleanliness, and a small proportion of abnormal materials such as cauliflower material.

[0004] The Chinese patent application number CN202211249262.2, entitled "A Polycrystalline Silicon Reduction Furnace Growth System," discloses a solution to the aforementioned problems: The design involves rotating upper and lower electrodes to enable silicon rods to rotate during growth. The upper electrode is located at the top of the furnace, while the lower electrode is located at the bottom. The upper and lower electrodes are positioned opposite each other and are both rotatably connected to the furnace. A silicon core is mounted between the upper and lower electrodes, and the upper and lower electrodes drive the silicon core's rotation. This approach addresses, to a certain extent, the problems of uneven temperature and flow distribution within the furnace, which can lead to the formation of yin and yang surfaces, pits, and the growth of cauliflower on the crossbars. However, this technology is complex and requires precise control. The rotating airflow is affected by changes within the furnace. Due to the high cost and high operational requirements, there is still a risk of cauliflower, making it difficult to fully resolve the aforementioned quality issues. Furthermore, the addition of metal equipment and lubricants within the furnace significantly increases the potential for metal and carbon contamination, making it impossible to meet the product quality requirements for electronic-grade polycrystalline silicon.

[0005] The Chinese patent application number is CN201420221899.5 and is titled: A polysilicon reduction furnace with a new type of air inlet and outlet structure. It discloses a reduction furnace with simultaneous upper and lower air intake, wherein the top air inlet pipe enters the furnace body through a head; the bottom air inlet pipe is connected to a small air inlet tube, and the small air inlet tube enters the furnace body through a chassis. This air intake method makes the gas flow field in the reduction furnace more uniform, which is conducive to the gas reaction to generate silicon rods and can improve the silicon rod growth efficiency to a certain extent; however, the upper air intake method using the head connection will cause the reduction furnace and the upper air inlet pipe to be in an open state, and the reduction furnace will be polluted by the external environment during the startup process, and cannot meet quality requirements. Summary of the Invention

[0006] In order to solve the above problems, the purpose of the present invention is to provide an electronic-grade polysilicon reduction furnace with a surround-type air intake, which is mainly suitable for the modified Siemens process (CVD production of polysilicon).

[0007] The present invention is implemented by the following technical solutions:

[0008] An electronic-grade polysilicon reduction furnace with a surround-type air intake comprises a furnace drum, a chassis, and a support platform. The horizontally arranged chassis is fixed to the support platform. During production, the bottom end of the furnace drum is sealed and openably fixedly connected to the chassis. When the product is removed from the furnace, the furnace drum and the chassis can be separated.

[0009] A plurality of pairs of electrodes are provided on the chassis, and a detachable graphite chuck is connected to each pair of electrodes, and a silicon core can be inserted into the graphite chuck; a plurality of exhaust holes are opened on the chassis, and the exhaust holes are sealedly connected to the exhaust branch pipe disposed outside the furnace, and the exhaust branch pipe is sealedly connected to the exhaust main pipe;

[0010] A nitrogen inlet and a nitrogen outlet communicating with the interior of the furnace are respectively provided on the side wall of the furnace;

[0011] The furnace drum is a jacketed furnace drum, a cooling water inlet is provided on the bottom side wall of the jacketed furnace drum, and a cooling water outlet is provided on the side wall of the jacketed furnace drum near the top;

[0012] A plurality of vertically arranged air intake branches are evenly arranged along the circumference in the interlayer of the jacketed furnace drum; the top ends of the air intake branches are closed structures and extend to the upper part of the jacketed furnace drum; the bottom ends of the air intake branches are sealed and pass through the bottom plate and are sealed and connected to the air intake main pipe arranged outside the jacketed furnace drum;

[0013] A plurality of connecting openings are evenly arranged on each of the air inlet branch pipes in the interlayer of the jacketed furnace drum from top to bottom, and a number of air inlet nozzles equal in number to the connecting openings are arranged in the jacketed furnace drum, and the air inlet ends of the air inlet nozzles are sealed through the inner layer of the jacketed furnace drum and are sealed and connected to the connecting openings.

[0014] Furthermore, each of the air inlet branch pipes includes an upper air inlet branch pipe and a lower air inlet branch pipe; the upper air inlet branch pipe is placed in the interlayer of the jacketed furnace drum, and has a top closed and bottom open structure; the lower air inlet branch pipe is placed outside the jacketed furnace drum, and has a two-end open structure;

[0015] The chassis is provided with branch pipe connection ports equal in number to the intake branch pipes, and the bottom end of the upper intake branch pipe and the top end of the lower intake branch pipe are sealedly connected to the upper end and the lower end of the branch pipe connection ports respectively.

[0016] Furthermore, an air intake flow regulating valve is provided on each of the lower air intake branches.

[0017] Furthermore, the number of the intake branch pipes is half the number of the electrode pairs located on the outer circle.

[0018] Furthermore, the number of pairs of electrodes is 12 to 60 pairs.

[0019] Furthermore, an observation eyepiece is provided on the side wall of the jacketed furnace.

[0020] Furthermore, the chassis is a hollow structure, and a water inlet and a water outlet are respectively provided on the chassis.

[0021] Furthermore, the air outlet end of the air inlet nozzle is a constricted structure.

[0022] Advantages of the present invention:

[0023] By arranging multiple air inlet nozzles from top to bottom on the upper air inlet branch pipe, the present invention ensures that the material feed airflow is uniform throughout the entire height of the furnace drum from top to bottom, effectively improving the flow field in the top head area of ​​the reduction furnace. The upper portion of the silicon rod and the surface of the crossbeam are subjected to gas scouring disturbance at a certain flow rate, thereby reducing or even avoiding the occurrence of the "popcorn" phenomenon. At the same time, it also solves the problems of excessively high temperature and low flow rate in the upper space of the furnace caused by the traditional bottom air inlet method, weakening the conditions for the generation of amorphous silicon powder and improving the conversion rate. Moreover, the temperature in the upper and lower parts of the furnace is uniform, avoiding the continuous supply of high current to ensure the temperature in the low-temperature area, reducing energy waste, effectively lowering the power consumption of the reduction furnace, and reducing costs. In addition, the upper air inlet branch pipe 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. Since the upper air inlet branch pipe is surrounded by cooling water, it can also effectively prevent high temperature from damaging the air inlet pipe, thereby extending the service life of the equipment. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0025] Figure 1 Schematic diagram of the structure of this embodiment;

[0026] Figure 2 Schematic diagram of the structure of the chassis in this embodiment.

[0027] In the figure: furnace 1, chassis 2, support platform 3, electrode 4, U-shaped silicon core 5, exhaust hole 6, exhaust branch pipe 7, exhaust main pipe 8, nitrogen inlet 9, nitrogen outlet 10, cooling water inlet 11, cooling water outlet 12, air intake branch pipe 13, upper air intake branch pipe 131, lower air intake branch pipe 132, air intake main pipe 14, air intake nozzle 15, branch pipe connecting port 16, air intake flow regulating valve 17, observation eyepiece 18, water inlet 19, water outlet 20. DETAILED DESCRIPTION

[0028] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0029] Example 1:

[0030] like Figure 1 、 Figure 2 The electronic-grade polysilicon reduction furnace shown in the figure has a surround-type air intake and 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 sealed 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, through which cooling water flows for cooling the chassis 2.

[0031] Several pairs of electrodes 4 are provided on the chassis 2. The number of pairs of electrodes 4 can be 12, 18, 36, 40, 54, or 60. A U-shaped silicon core 5 is inserted into each pair of electrodes 4, forming a closed circuit. Several exhaust holes 6 are provided on the chassis 2. These exhaust holes 6 are sealed with exhaust branch pipes 7 located outside the furnace tube 1. The exhaust branch pipes 7 are sealed with an exhaust main pipe 8.

[0032] A nitrogen inlet 9 and a nitrogen outlet 10 connected to the interior of the furnace barrel 1 are respectively provided on the side walls of the furnace barrel 1, through which high-purity nitrogen can be fed into the furnace barrel 1 to replace (expel air to ensure product quality) the gas in the furnace; an observation eyepiece 18 is provided on the side wall in the middle of the jacketed furnace barrel 1 for observing the growth conditions in the furnace.

[0033] The furnace drum 1 is a jacketed furnace drum 1. A cooling water inlet 11 is provided on the bottom side wall of the jacketed furnace drum 1. A cooling water outlet 12 is provided on the side wall of the jacketed furnace drum 1 near the top. Cooling water flows through the furnace drum 1 to cool the furnace drum 1.

[0034] Several vertically arranged air intake branches 13 are evenly arranged along the circumference of the interlayer of the jacketed furnace drum 1. The number of the air intake branches 13 is half the number of the electrode pairs 4 located on the outer circle. The top ends of the air intake branches 13 are closed and extend to the upper part of the jacketed furnace drum 1. The bottom ends of the air intake branches 13 are sealed and pass through the bottom plate 2 and are sealed and connected to the air intake main pipe 14 located outside the jacketed furnace drum 1.

[0035] Each air inlet branch pipe 13 within the interlayer of the jacketed furnace barrel 1 is uniformly provided with multiple connecting ports, preferably 2 to 4, from top to bottom. A number of air inlet nozzles 15 are provided within the jacketed furnace barrel 1, equal to the number of connecting ports. The air inlet end of the air inlet nozzle 15 is sealed through the inner layer of the jacketed furnace barrel 1 and is sealed and connected to the connecting port. The air outlet end of the air inlet nozzle 15 is a tapered structure, which can increase the flow rate of the gas during ejection, allowing the gas to be ejected farther, ensuring a more uniform flow field within the furnace barrel 1, and further optimizing the growth environment of the silicon rod. In this embodiment, each air inlet branch pipe 13 includes an upper air inlet branch pipe 131 and a lower air inlet branch pipe 132. The upper air inlet branch pipe 131 is placed within the interlayer of the jacketed furnace barrel 1 and has a closed top and open bottom structure. The lower air inlet branch pipe 132 is placed outside the jacketed furnace barrel 1 and has an open end structure. Each lower air inlet branch pipe 132 is provided with an air inlet flow regulating valve 17.

[0036] The chassis 2 is provided with branch pipe connection ports 16 equal in number to the intake branch pipes 13 , and the bottom end of the upper intake branch pipe 131 and the top end of the lower intake branch pipe 132 are sealedly connected to the upper and lower ends of the branch pipe connection ports 16 respectively.

[0037] Job Description:

[0038] When using this embodiment, after the U-shaped silicon core 5 and electrode 4 are installed and secured, the furnace drum 1 is placed over the chassis 2 and sealed. At the same time, the upper and lower air intake branches 131, 132 are both sealed and connected to the branch pipe connection port 16. Nitrogen is then introduced into the furnace drum 1 to displace the air within. The displaced gas is then discharged through the exhaust port 6 provided in the chassis 2, through the exhaust branch pipe 7, and then through the exhaust main pipe 8. A mixed gas of SiHCl3 and H2 is then introduced. The SiHCl3 and H2 enter the main pipe 14 through a mixer, and then sequentially enter the lower and upper air intake branches 132, 131, before being delivered into the furnace drum 1 through the air intake nozzle 15. The SiHCl3 and H2 react with the heated silicon cores to produce silicon rods through a chemical vapor deposition reaction, and the exhaust gas is then discharged through the exhaust port 6, through the exhaust branch pipe 7, and finally through the exhaust main pipe 8. At the same time, cooling water is introduced into the jacket of furnace drum 1 and into the bottom plate 2 to cool the heat-generating areas, such as the sidewalls and bottom plate 2 of furnace drum 1. This removes heat from the furnace drum 1 and prevents temperature rise and deposition. Meanwhile, the growth of silicon rods in furnace drum 1 is monitored through eyepiece 18, and the air intake and current are adjusted accordingly.

[0039] In this embodiment, by arranging multiple air inlet nozzles 15 from top to bottom on the upper air inlet branch 131, a material feed airflow can be provided throughout the entire height of the furnace barrel 1 from top to bottom, so that the raw gas surrounds the silicon core from top to bottom, effectively avoiding the problems of excessively high temperature and low flow rate in the upper space of the furnace barrel 1 caused by the traditional bottom air intake method, eliminating factors such as uneven temperature and uneven airflow in the furnace that are not conducive to the uniform deposition of silicon rods, weakening the conditions for the production of amorphous silicon powder, and improving the conversion rate. At the same time, the stable temperature field and flow field can provide more accurate current and voltage feedback when formulating the polycrystalline silicon rod growth formula, control the polycrystalline silicon growth rate, generate a denser crystal structure, and thus improve the yield. Moreover, the uniform temperature above and below the furnace avoids the continuous high current provided to ensure the temperature in the low temperature area, which can reduce energy waste, effectively reduce the power consumption of the reduction furnace, and reduce costs.

[0040] The air inlet nozzle 15 located at the top blows a mixture of SiHCl3 and H2 from the top of the upper furnace tube 1, which can improve the flow field in the top head area of ​​the furnace tube 1 and make the upper part of the silicon rod and the surface of the beam be disturbed by the gas at a certain flow rate, thus avoiding the occurrence of the "popcorn" phenomenon.

[0041] Furthermore, in this embodiment, the upper air intake manifold 131, located within the jacket, is surrounded by high-temperature cooling water. This preheats the mixed gas entering the furnace, fully vaporizing it and improving contact between the gas and the silicon core, thus promoting the chemical vapor deposition reaction. Furthermore, since the upper air intake manifold 131 is surrounded by cooling water, it effectively prevents high-temperature damage to the air intake pipe, thereby extending the service life of the equipment.

[0042] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. An electronic-grade polysilicon reduction furnace with a surround-type air intake, comprising a furnace drum, a chassis, and a support platform, wherein the horizontally arranged chassis is fixed to the support platform, and the bottom end of the furnace drum is sealed and fixedly connected to the chassis; A plurality of pairs of electrodes are provided on the chassis, and a U-shaped silicon core is inserted into each pair of electrodes; a plurality of tail gas holes are opened on the chassis, and the tail gas holes are sealedly connected to the tail gas branch pipes arranged outside the furnace, and the tail gas branch pipes are sealedly connected to the tail gas main pipe; A nitrogen inlet and a nitrogen outlet communicating with the interior of the furnace are respectively provided on the side wall of the furnace; It is characterized by: The furnace drum is a jacketed furnace drum, a cooling water inlet is provided on the bottom side wall of the jacketed furnace drum, and a cooling water outlet is provided on the side wall of the jacketed furnace drum near the top; A plurality of vertically arranged air intake branches are evenly arranged along the circumference in the interlayer of the jacketed furnace drum; the top ends of the air intake branches are closed structures and extend to the upper part of the jacketed furnace drum; the bottom ends of the air intake branches are sealed and pass through the bottom plate and are sealed and connected to the air intake main pipe arranged outside the jacketed furnace drum; A plurality of connecting openings are evenly arranged on each of the air inlet branch pipes in the interlayer of the jacketed furnace drum from top to bottom, and a number of air inlet nozzles equal to the number of the connecting openings are arranged in the jacketed furnace drum, and the air inlet end of the air inlet nozzle is sealed through the inner layer of the jacketed furnace drum and is sealed and connected to the connecting opening; the air outlet end of the air inlet nozzle is a contracted structure.

2. The electronic-grade polysilicon reduction furnace with a surround-type air intake according to claim 1, characterized in that: Each of the air inlet branch pipes includes an upper air inlet branch pipe and a lower air inlet branch pipe; the upper air inlet branch pipe is placed in the interlayer of the jacketed furnace drum, and has a top closed and bottom open structure; the lower air inlet branch pipe is placed outside the jacketed furnace drum, and has a two-end open structure; The chassis is provided with branch pipe connection ports equal in number to the intake branch pipes, and the bottom end of the upper intake branch pipe and the top end of the lower intake branch pipe are sealedly connected to the upper end and the lower end of the branch pipe connection ports respectively.

3. The electronic-grade polysilicon reduction furnace with a surround-type air intake according to claim 2, characterized in that: An air intake flow regulating valve is provided on each of the lower air intake branches.

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

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

6. The electronic-grade polysilicon reduction furnace with a surround-type air intake according to claim 1, characterized in that: An observation eyepiece is provided on the side wall of the jacketed furnace drum.

7. The electronic-grade polysilicon reduction furnace with a surround-type 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 opened on the chassis.

Images