Reduction furnace for improving gas flow field

Abstract

A reduction furnace for improving a gas flow field relates to the field of artificial lens preparation, and comprises a furnace body and a plurality of groups of overlapped silicon core groups, a plurality of gas inlets are arranged at the furnace bottom of the furnace body, the gas inlets are communicated with a feed gas conveying pipeline, each silicon core group comprises two vertical silicon cores arranged vertically and a cross beam arranged at the upper ends of the vertical silicon cores, an auxiliary air inlet pipe is arranged at the upper end of at least one air inlet, the upper end of the auxiliary air inlet pipe is located on the upper portion of the furnace body, a hollow space of the auxiliary air inlet pipe is an air inlet channel, one end of the air inlet channel is communicated with the air inlets, and the other end of the air inlet channel is communicated with the space on the upper portion of the polycrystalline silicon reduction furnace. According to the utility model, the hollow space of the auxiliary gas inlet pipe is used as a gas inlet channel, so that feed gas can enter the cover body from the upper part of the polycrystalline silicon reduction furnace, the problems of leakage and the like caused by forming a gas inlet above the cover body can be avoided, and a gas flow field in the polycrystalline silicon reduction furnace can be more uniform.

Description

TECHNICAL FIELD

[0001] The utility model relates to the artificial crystal preparation field, and specifically the utility model relates to a reducing furnace for improving gas flow field. BACKGROUND

[0002] The hydrogen reduction method of trichlorosilane (i.e. Siemens method) is a preparation technology of high-purity polysilicon invented by Siemens Company in Germany in 1954 and widely used. High-purity trichlorosilane and high-purity hydrogen have a reduction reaction on a heated high-purity polysilicon core, and new high-purity polysilicon is generated and deposited on the silicon core through chemical vapor deposition.

[0003] The commonly used silicon cores are generally divided into solid silicon cores and hollow silicon cores. When the deposition rate per unit area is constant, the larger the surface area is, the more polysilicon is deposited. Therefore, the technical scheme of using hollow silicon cores to grow polysilicon rods (for example, US4062714A, CN101432460B and CN103160926A, etc.) can make the diameter of the hollow silicon core much larger than that of the solid silicon core under the condition that the weights are basically equal, thereby improving the production efficiency and reducing the production cost. In addition, the use of hollow silicon cores can also overcome the silicon core lodging phenomenon during the reduction process.

[0004] The reducing furnace is the main equipment in the above-mentioned Siemens method polysilicon production process. The existing reducing furnace is usually a vertical bell-shaped reactor, mainly including a cover body, a furnace bottom, a silicon core group after lapping, and an air inlet and an exhaust outlet arranged at the furnace bottom.

[0005] Specifically, the cover body is connected with a cover body lifting device, and the cover body lifting device drives the cover body to ascend and descend and rotate left and right to realize the purpose of disassembling and assembling the furnace. The cover body is placed above the furnace bottom, and the cover body and the furnace bottom combine to form a closed chamber. A plurality of silicon core groups after lapping are arranged on the furnace bottom, and each silicon core group after lapping is connected with a set of heating electrodes, and the silicon core group is heated by the heating electrodes. The furnace bottom is also provided with an air inlet and an exhaust outlet. The mixed gas of trichlorosilane and hydrogen enters the closed chamber from the air inlet, and the tail gas is discharged from the exhaust outlet.

[0006] Due to the structure limitation of the reduction furnace itself, the gas inlet is from the bottom, and the tail gas outlet is also at the bottom of the furnace, so the gas sprayed from the existing structure of the gas inlet nozzle is difficult to reach the upper part of the cover body, thereby forming a stagnant zone at the top of the reduction furnace, and the gas is difficult to form a good uniform distribution in the reduction furnace, that is, the gas flow field (gas concentration distribution and flow condition) is not uniform. In the middle of the reduction deposition process of the silicon rod, due to the existence of the stagnant zone at the top of the cover body, the newly-incoming raw material gas cannot reach the reaction zone at the top of the cover body, so that the stagnant gas at the top cannot enter the gas circulation system, resulting in high temperature at the top of the cover body. And with the increase of the diameter of the silicon rod, the required raw material for reduction must also be continuously increased, so that the amount of raw material reaction gas at the top is particularly insufficient. With the progress of the deposition reaction, the diameter of the silicon rod increases, the turbulent flow becomes worse, and the boundary layer effect of the deposition carrier surface is enhanced, so that the silicon rod grows unevenly, and structure interlayers are easily formed. The crystal grains are deposited in a loose and rough form, and then develop into nodules (i.e. the upper end of the polycrystalline silicon rod is prone to form popcorn), which often contain bubbles and impurities, and are difficult to remove by acid treatment and corrosion. In the later use of the Czochralski furnace to draw single crystal melt, the molten silicon liquid surface fluctuates, and even the molten silicon is splashed and silicon jumps, which seriously affects the drawing of the crystal. The polycrystalline silicon at the upper end of the silicon rod grows slowly and is loose and not dense, forming a rough and loose upper part and a dense and solid lower part. This causes difficulties in the subsequent corrosion cleaning and crystal drawing processes.

[0007] In order to overcome the above problems, CN101748482B once proposed an improved method and device for preparing high-density structure polycrystalline silicon, which is to change the gas flow field in the reduction furnace, so that the gas flow field in the reduction furnace is more uniform. However, in practice, it is found that this method cannot effectively improve the uniformity of the gas flow field in the whole reduction furnace. In addition, due to the high temperature at the upper part of the reduction furnace and the presence of a large amount of hydrogen and other flammable, explosive and toxic gases, if the gas inlet is arranged on the upper head of the furnace chamber, the connection between the gas inlet and the upper head is prone to fatigue corrosion (for example, hydrogen can corrode stainless steel, etc.) due to temperature difference stress, thereby causing leakage and safety accidents. In addition, the gas inlet needs to be connected by a pipeline, and the cover body will be lifted up and down and rotated left and right during the disassembly and assembly process, so there is a risk of pipeline breakage during this process. SUMMARY

[0008] In order to overcome the deficiencies in the background art, the utility model discloses a reduction furnace for improving the gas flow field, which forms a door-shaped conductive loop by lapping the upper ends of the two vertical silicon cores with the cross beam, and simultaneously introduces mixed gas into the gas inlet channel of the auxiliary gas inlet pipe, so that the mixed gas reaches the upper part of the furnace chamber through the gas inlet channel, thereby achieving the technical effect of lower gas inlet and lower gas outlet + upper gas inlet and lower gas outlet without opening a gas inlet on the top of the furnace chamber.

[0009] In order to achieve the above-mentioned purpose of the application, the utility model discloses the following technical scheme:

[0010] A reducing furnace for improving gas flow field, comprising a furnace body and a plurality of groups of silicon core groups after lapping, a plurality of gas inlets are arranged at the furnace bottom of the furnace body, the gas inlets are communicated with raw material gas conveying pipelines, the silicon core group comprises two vertical silicon cores arranged vertically and a crossbeam arranged at the upper end of the vertical silicon core, an auxiliary gas inlet pipe is arranged at the upper end of at least one gas inlet, the upper end of the auxiliary gas inlet pipe is located at the upper part of the furnace body, the hollow space of the auxiliary gas inlet pipe is a gas inlet channel, one end of the gas inlet channel is communicated with the gas inlet, and the other end is communicated with the space at the upper part of the polycrystalline silicon reducing furnace.

[0011] The reducing furnace for improving gas flow field, and the vertical silicon core is any one of a solid silicon core or a hollow silicon pipe.

[0012] The reducing furnace for improving gas flow field, and the vertical silicon core is fixed on the furnace bottom through a base.

[0013] The reducing furnace for improving gas flow field, and the middle part of the furnace bottom is provided with a gas outlet.

[0014] The reducing furnace for improving gas flow field, and the upper end of the auxiliary gas inlet pipe is provided with a gas nozzle.

[0015] The reducing furnace for improving gas flow field, and a gas flow regulating valve is arranged on the raw material gas conveying pipeline.

[0016] The reducing furnace for improving gas flow field, and the auxiliary gas inlet pipe is a composite pipe composed of a high-temperature ceramic pipe or a quartz pipe or a metal pipe outside which is sleeved with a high-temperature ceramic pipe or a composite pipe composed of a metal pipe outside which is sleeved with a quartz pipe.

[0017] Through the above disclosure, the utility model has the beneficial effects that:

[0018] The utility model discloses the hollow space of auxiliary gas inlet pipe as gas inlet channel, realizes the technical effect of lower gas inlet lower gas outlet + upper gas inlet lower gas outlet without setting gas inlet on the cover body, so that raw material gas can enter the upper part of the cover body from the bottom of the polycrystalline silicon reducing furnace, not only can avoid the leakage and other problems caused by setting gas inlet on the cover body, but also can make the gas flow field in the polycrystalline silicon reducing furnace more uniform. ACCURACY OF DRAWINGS

[0019] Fig. 1 It is the structure schematic diagram of the utility model;

[0020] Fig. 2 It is the furnace chamber gas flow field simulation diagram when the auxiliary gas inlet pipe is ventilated in the embodiment of the utility model furnace bottom gas inlet, furnace bottom gas outlet; It is the furnace chamber gas flow field simulation diagram when the auxiliary gas inlet pipe is ventilated in the embodiment of the utility model furnace bottom gas inlet, furnace bottom gas outlet;

[0021] In the figure: 1, crossbeam; 2, auxiliary air inlet pipe; 3, vertical silicon core; 4, air inlet channel; 5, air outlet; 6, base; 7, air inlet; 8, furnace bottom. DETAILED DESCRIPTION

[0022] The utility model is further described below in combination with examples; the following examples are not a limitation on the utility model, and are only used as a mode for supporting the implementation of the utility model; any equivalent structure replacement within the technical framework disclosed by the utility model is within the protection scope of the utility model;

[0023] In combination with the drawings Figs. 1-2 The utility model discloses a reducing furnace that improves gas flow field, including furnace body (not shown in the figure) and multiple groups of silicon core groups after lapping, the furnace body mainly includes cover body (not shown in the figure), furnace bottom 8, silicon core group after lapping and multiple air inlets 7, air outlets 5 etc. arranged at furnace bottom 8, the silicon core group after lapping can be fixed on furnace bottom 8 through base 6 on furnace bottom 8, for example, raw material gas composed of trichlorosilane and hydrogen is transported to air inlet 7 through raw material gas conveying pipeline (not shown in the figure) and then enters the inside of furnace body. The structure of furnace body is prior art, so it is not repeated here.

[0024] The silicon core group includes two vertical silicon cores 3 arranged vertically and a crossbeam 1 arranged at the upper end of the vertical silicon cores 3. Specifically, the two vertical silicon cores 3 are arranged at intervals. The present application does not limit the way in which the vertical silicon cores 3 are fixed on the furnace bottom 8. The vertical silicon cores 3 are fixed on the furnace bottom 8 through the base 6 as an example for description below. The vertical silicon cores 3 can also be fixed on the furnace bottom 8 through other ways. The vertical silicon cores 3 are any one of solid silicon cores or hollow silicon tubes.

[0025] The furnace bottom 8 of the furnace body is provided with multiple air inlets 7. The air inlets 7 are in communication with the raw material gas conveying pipeline. The silicon core group includes two vertical silicon cores 3 arranged vertically and a crossbeam 1 arranged at the upper end of the vertical silicon cores 3. An auxiliary air inlet pipe 2 is arranged at the upper end of at least one air inlet 7. The upper end of the auxiliary air inlet pipe 2 is located at the upper part of the furnace body. The hollow space of the auxiliary air inlet pipe 2 is an air inlet channel 4. One end of the air inlet channel 4 is in communication with the air inlet 7, and the other end is in communication with the space at the upper part of the polysilicon reducing furnace.

[0026] In implementation, the vertical silicon cores 3 are fixed on the furnace bottom 8 through the base 6.

[0027] Further, the middle part of the furnace bottom 8 is provided with an air outlet 5.

[0028] Further, the upper end of the auxiliary air inlet pipe 2 is provided with a gas jet nozzle.

[0029] Further, a gas flow regulating valve is arranged on the raw material gas conveying pipeline.

[0030] Further, the auxiliary gas inlet pipe 2 is a high-temperature ceramic pipe or a quartz pipe or a composite pipe composed of a high-temperature ceramic pipe or a quartz pipe sleeved outside a metal pipe.

[0031] In order to solve the problem of uneven gas flow field in the polycrystalline silicon reduction furnace, in the present application, the raw material gas can also enter the upper part of the furnace body through the auxiliary gas inlet pipe 2, that is, the hollow space of the auxiliary gas inlet pipe 2 is an inlet channel 4, one end (lower end) of which is in communication with part of the gas inlets 7, and the other end (upper end) is in communication with the space in the upper part of the polycrystalline silicon reduction furnace.

[0032] It should be noted that the present application does not limit the position and structure of part of the gas inlets 7.

[0033] It should be noted that the part of the gas inlets 7 in communication with the inlet channel 4 can use the same raw material gas conveying pipeline for gas supply as the other gas inlets 7 (i.e. the gas inlets directly in communication with the inside of the furnace body and not in communication with the inlet channel 4), or use different raw material gas conveying pipelines for gas supply.

[0034] In order to control the flow rate of the raw material gas, a gas flow regulating valve is arranged on the raw material gas conveying pipeline. When different raw material gas conveying pipelines are used to supply gas to the gas inlets 7, the gas flow rates of different gas inlets 7 can be controlled respectively.

[0035] In the present embodiment, part of the raw material gas composed of trichlorosilane and hydrogen directly enters the inside of the furnace body through the gas inlets 7, and part of the raw material gas enters the inlet channel 4 of the auxiliary gas inlet pipe 2 through the gas inlets 7, and then enters the upper part of the furnace body.

[0036] The above gives an exemplary embodiment of using the inlet channel 4 of the auxiliary gas inlet pipe 2 to provide raw material gas for the upper part of the furnace body, and the present application does not limit the specific structure of the silicon core group.

[0037] The present application does not need to open gas inlets above the cover body, and can realize simultaneous gas inlet from the bottom and the upper part of the polycrystalline silicon reduction furnace. Fig. 2 is a simulation diagram of the gas flow field in the polycrystalline silicon reduction furnace of the present application. Specifically, a three-dimensional design software is used to simulate the gas flow field in the polycrystalline silicon reduction furnace.

[0038] In simulation, a polysilicon reduction furnace model with 12 groups of silicon core groups is selected to simulate the flow field, the total height of the polysilicon reduction furnace body is set to 2.7 m, the diameter is set to 1.2 m, the height of the silicon core group is set to 2.4 m, the outer diameter of the vertical silicon core 3 is set to 80 mm, the polysilicon reduction furnace model has 6 main air inlets and 1 air outlet, the air outlet hole is arranged in the middle of the furnace bottom, the 6 main air inlets are uniformly arranged around the air outlet, and auxiliary air pipes 2 are arranged on two main air inlets respectively, wherein the air inlet amount of the four main air inlets connected with the auxiliary air pipes 2 is 5 cubic meters per second, and the air inlet amount of the air inlet channel 4 of the auxiliary air pipe 2 is 4.5 cubic meters per second.

[0039] From Fig. 2 It can be seen that, by using the method of simultaneously introducing air from the bottom and the upper part of the polysilicon reduction furnace, the stagnant zone at the top of the cover body is avoided, the gas flow field in the polysilicon reduction furnace is more uniform, and the problem of popcorn material generated on the upper part of the silicon rod is solved.

[0040] In order to avoid too much raw material gas entering the upper part of the polysilicon reduction furnace, causing the upper gas flow to be too dense and affecting the production effect, the gas flow rate of the raw material gas entering the upper part of the furnace body through the air inlet channel 4 is less than that of the raw material gas directly entering the furnace body through the air inlet 7.

[0041] In summary, the hollow space of the auxiliary air pipe 2 is used as an air inlet channel in the present application, so that the raw material gas can enter the cover body from the upper part of the polysilicon reduction furnace, which not only avoids the problem of leakage caused by opening the air inlet on the top of the cover body, but also makes the gas flow field in the polysilicon reduction furnace more uniform.

[0042] The part not described in the present application is prior art.

[0043] In order to disclose the invention purpose of the present application, the embodiments selected in the text are currently considered to be appropriate, but it should be understood that the present application is intended to include all changes and improvements of the embodiments within the scope of the present concept and invention.

Claims

1. A reduction furnace for improving gas flow field, comprising a furnace body and multiple sets of overlapping silicon cores, wherein multiple air inlets (7) are provided at the furnace bottom (8) of the furnace body, the air inlets (7) being connected to a raw material gas conveying pipeline, and the silicon cores comprising two vertically arranged vertical silicon cores (3) and a crossbeam (1) disposed at the upper end of the vertical silicon cores (3), characterized in that: At least one of the air inlets (7) is provided with an auxiliary air inlet pipe (2) at its upper end. The upper end of the auxiliary air inlet pipe (2) is located at the upper part of the furnace body. The hollow space of the auxiliary air inlet pipe (2) is an air inlet channel (4). One end of the air inlet channel (4) is connected to the air inlet (7), and the other end is connected to the space at the upper part of the reduction furnace.

2. The reduction furnace for improving the gas flow field according to claim 1, characterized in that: The vertical silicon core (3) can be either a solid silicon core or a hollow silicon tube.

3. The reduction furnace for improving the gas flow field according to claim 1, characterized in that: The vertical silicon core (3) is fixed to the furnace bottom (8) by the base (6).

4. The reduction furnace for improving the gas flow field according to claim 1, characterized in that: The furnace bottom (8) is provided with an air outlet (5) in the middle.

5. The reduction furnace for improving the gas flow field according to claim 1, characterized in that: The upper end of the auxiliary air intake pipe (2) is provided with an air nozzle.

6. The reduction furnace for improving gas flow field according to claim 1, characterized in that: The raw material gas conveying pipeline is equipped with a gas flow regulating valve.

7. The reduction furnace for improving the gas flow field according to claim 1, characterized in that: The auxiliary air intake pipe (2) is a composite pipe consisting of a high-temperature ceramic tube, a quartz tube, or a metal tube with a high-temperature ceramic tube attached to the outside, or a metal tube with a quartz tube attached to the outside.

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