Novel electronic-grade zone-melting polycrystalline silicon CVD (Chemical Vapor Deposition) reaction system

Abstract

The utility model relates to the technical field of electronic grade polycrystalline silicon production, in particular to a novel electronic grade zone-melting polycrystalline silicon CVD (chemical vapor deposition) reaction system which comprises a CVD reaction furnace chassis and a CVD reaction furnace, the CVD reaction furnace chassis comprises a chassis, an inner ring gas outlet is formed in the middle of the chassis, and outer ring gas inlets which are annularly distributed at equal intervals are formed in the inner side of the chassis; a first electrode mounting hole and a second electrode mounting hole for mounting the first electrode and the second electrode are formed in the inner side of the chassis; the CVD reaction furnace comprises an outer ring furnace barrel, an outer ring is fixedly connected to the inner side of the outer ring furnace barrel, a first heat dissipation interlayer used for temperature adjustment and protection is arranged in the outer ring, an outer ring air inlet is formed in the bottom of the outer ring furnace barrel, an inner ring air inlet is formed in the top of the inner ring furnace barrel, an inner ring air outlet is formed in the bottom of the inner ring furnace barrel, and overall airflow forms a U-shaped loop. And the gas which does not finish the reduction reaction in the outer ring can continuously react in the inner ring, so that the single-furnace conversion rate can be improved, the comprehensive productivity can be improved, and the cost can be reduced.

Description

Technical Field

[0001] The utility model relates to the technical field of electronic-grade polysilicon production, in particular to a novel electronic-grade zone melting polysilicon CVD reaction system. Background Art

[0002] The modified Siemens method is the mainstream process for the production of electronic-grade polysilicon, among which the chemical vapor deposition method is the main method for producing electronic-grade zone melting polysilicon rods. The bell-shaped CVD reactor is the core equipment for preparing crystalline silicon using the modified Siemens method. Its working principle is that the silicon core installed on the chassis generates heat through resistance, and the raw gas SiHCl3 and H2 react with chemical vapor deposition on the surface of the hot silicon core to generate crystalline silicon. The product silicon is finally extracted from the reduction furnace in the form of rods;

[0003] The traditional polysilicon reduction furnace adopts the bottom inlet and outlet method, that is, SiHCl3 and H2 are sprayed into the CVD reactor from several air inlets opened on the chassis. After a series of chemical reactions, the reaction tail gas flows out from several air outlets opened on the chassis. In addition to the air inlet and outlet, the chassis is also provided with several electrode holes. The purity of electronic-grade polysilicon in the semiconductor industry is extremely high. Therefore, compared with photovoltaic-grade polysilicon, the quality requirements of electronic-grade zone melting polysilicon are higher. Not only the high density of silicon rods but also the surface morphology of silicon rods need to be guaranteed. Therefore, the conversion rate of electronic-grade polysilicon is low and the growth rate is slow. At present, the conversion rate of trichlorosilane in the industry is generally around 13%, while that of electronic-grade is less than 10%. In addition, the output of zone melting polysilicon is extremely low. At present, there is no enterprise in China that can fully mass-produce 100%. Therefore, it is extremely important to increase the output of electronic-grade zone melting polysilicon.

[0004] Patent CN202120922650.7 describes an improved reduction furnace chassis air intake structure and a reduction furnace, the air intake structure includes an air intake main pipe, a ring pipe and a branch pipe, a plurality of branch pipes are provided, the branch pipes are located above the ring pipe and connected to the ring pipe, and the characteristic is that an air intake port is provided on the ring pipe, and the air intake direction of the air intake port is perpendicular or parallel to the plane where the ring pipe is located. When the air intake direction of the air intake port is perpendicular to the plane where the ring pipe is located, the air intake port is provided with a single or multiple air intake ports, and when the air intake direction of the air intake port is parallel to the plane where the ring pipe is located, the air intake port is provided with a single or multiple air intake ports. In a plane, multiple air inlet openings are evenly distributed along the circumference of the ring tube, and the air inlet openings are all connected to the air inlet main pipe. The reduction furnace includes a furnace body, and an improved reduction furnace chassis air inlet structure is arranged on the furnace body chassis. Compared with the prior art, the utility model has the advantages of uniform airflow and improved reduction furnace quality, but the utility model has a complex structure and does not improve the production capacity. Therefore, the optimization of output and conversion rate still needs to be developed and verified. Therefore, in view of the above problems, a new electronic-grade zone melting polysilicon CVD reaction system is proposed. Utility Model Content

[0005] The utility model aims to provide a novel electronic-grade zone melting polysilicon CVD reaction system to solve the problems of complex structure of the original reduction furnace and low output and conversion rate.

[0006] In order to achieve the above purpose, the utility model provides the following technical solutions:

[0007] A novel electronic-grade zone melting polysilicon CVD reaction system comprises a CVD reaction furnace chassis and a CVD reaction furnace, wherein the CVD reaction furnace chassis comprises a chassis, an inner ring air outlet is provided in the middle of the chassis, an outer ring air inlet is provided in an annular and equidistantly distributed manner on the inner side of the chassis, a first electrode mounting hole and a second electrode mounting hole are provided on the inner side of the chassis for mounting a first electrode and a second electrode; the CVD reaction furnace comprises an outer ring furnace barrel, an outer ring is fixedly connected to the inner side of the outer ring furnace barrel, a first heat dissipation interlayer for temperature regulation and protection is provided inside the outer ring, the inner top of the outer ring is fixedly connected to the inner ring furnace barrel through a connecting block, an inner ring is fixedly connected to the inner ring furnace barrel, and a first heat dissipation interlayer for temperature regulation and protection is provided inside the inner ring; The second heat dissipation interlayer for degree adjustment and protection, the inner circle furnace barrel and the inner circle upper end are provided with an inner circle air inlet, the inner circle furnace barrel and the inner circle bottom are installed in the annular sealing groove provided on the inner side of the chassis, and the CVD reactor and the CVD reactor chassis are welded and fixed by connecting pads; a first water pipe is installed at the bottom end of the first heat dissipation interlayer, and a second water pipe is installed at the bottom end of the second heat dissipation interlayer, the bottom end of the outer circle air inlet is fixedly connected with the air intake ring pipe through an air pipe, and a ring pipe air supply port for introducing a mixed gas of SiHCl3 and H2 is provided at the bottom end of the air intake ring pipe, a first electrode for providing current is installed on the inner side of the first electrode mounting hole, and a second electrode for providing current is installed on the inner side of the second electrode mounting hole.

[0008] Preferably, the position where the chassis contacts the bottom of the outer ring is the outer ring of the chassis, the position where the chassis contacts the bottom of the inner ring is the inner ring of the chassis, the diameter of the chassis is 2500mm, the diameter of the outer ring of the chassis to the inner ring of the chassis is 600mm, the diameter of the inner ring of the chassis is 950mm, the outer ring air inlet is opened between the outer ring of the chassis and the inner ring of the chassis, the first electrode is installed between the outer ring of the chassis and the inner ring of the chassis, and the second electrode is installed on the inner side of the inner ring of the chassis.

[0009] Preferably, there are 8 pairs of second electrodes installed between the outer ring and the inner ring of the chassis, 15 air inlets are opened in the outer ring, 4 pairs of first electrodes are installed on the inner side of the inner ring of the chassis, and there is one air outlet in the inner ring.

[0010] Preferably, the inner ring and the outer ring are both cylindrical with an open lower end, and the center points of the inner ring, the outer ring and the chassis are arranged on the same vertical line.

[0011] Preferably, the inner ring air inlets are provided with a plurality of air inlets, and the inner ring air inlets are evenly distributed in the inner ring furnace barrel and the upper end of the inner ring in a ring shape, and the interior of the inner ring is connected with the interior of the outer ring through the inner ring air inlets.

[0012] Preferably, the first electrode mounting hole is twice as long as the first electrode, the second electrode mounting hole is twice as long as the second electrode, and both the first electrode and the second electrode are U-shaped.

[0013] Preferably, partitions are installed inside the first heat dissipation interlayer and the second heat dissipation interlayer, two first water pipes are installed at the bottom end of the first heat dissipation interlayer, one of the first water pipes is a water inlet pipe, and the other first water pipe is a water outlet pipe, and two second water pipes are installed at the bottom end of the second heat dissipation interlayer, one of the second water pipes is a water inlet pipe, and the other second water pipe is a water outlet pipe.

[0014] Preferably, the connecting pad is arranged in an annular shape, the vertical section of the outer ring furnace drum is T-shaped, the outer diameter of the connecting pad is equal to the outer diameter of the bottom end of the outer ring furnace drum, and the inner diameter of the connecting pad is equal to the inner diameter of the bottom end of the outer ring furnace drum.

[0015] Preferably, the SiHCl3 and H2 mixed gas enters the inner ring in the reverse direction through the inner ring gas outlet.

[0016] Compared with the prior art, the beneficial effects of the utility model are:

[0017] In the utility model, a double-layer furnace tube cover is formed by arranging an outer ring furnace tube, an inner ring furnace tube, an inner ring and an outer ring. An outer ring air inlet is provided at the bottom of the outer ring furnace tube, an inner ring air inlet is provided at the top of the inner ring furnace tube, and an inner ring air outlet is provided at the bottom. The overall airflow forms a U-shaped loop, and the gas that has not completed the reduction reaction in the outer ring will continue to react in the inner ring, thereby improving the conversion rate of a single furnace, increasing the comprehensive production capacity, reducing costs, and the structure is also relatively simple. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a schematic diagram of the overall structure of the utility model;

[0019] Figure 2 This is a schematic diagram of the chassis structure of the utility model;

[0020] Figure 3 This is a flow chart of preheating the outer ring of electronic-grade zone melting polysilicon processing in the utility model;

[0021] Figure 4 This is a flow chart of inner ring preheating in electronic-grade zone melting polysilicon processing according to the utility model.

[0022] In the figure: 1. outer ring furnace drum; 2. chassis; 3. inner ring furnace drum; 4. inner ring air inlet; 5. outer ring air inlet; 6. inner ring; 7. inner ring air outlet; 8. outer ring; 9. air inlet ring pipe; 10. first heat dissipation interlayer; 11. second heat dissipation interlayer; 12. connection pad; 13. first electrode mounting hole; 14. first water pipe; 15. second water pipe; 16. ring pipe air supply port; 17. second electrode; 18. first electrode; 19. second electrode mounting hole. DETAILED DESCRIPTION

[0023] Embodiment 1:

[0024] See also Figure 1-3 , the utility model provides a technical solution:

[0025] A novel electronic-grade zone melting polysilicon CVD reaction system comprises a CVD reactor chassis and a CVD reactor, wherein the CVD reactor chassis comprises a chassis 2, an inner ring air outlet 7 is provided in the middle of the chassis 2, an outer ring air inlet 5 is provided on the inner side of the chassis 2 and is distributed in an annular manner and is equidistantly, a first electrode mounting hole 13 and a second electrode mounting hole 19 are provided on the inner side of the chassis 2 for mounting a first electrode 18 and a second electrode 19; the CVD reactor comprises an outer ring furnace barrel 1, an outer ring 8 is fixedly connected to the inner side of the outer ring furnace barrel 1, a first heat dissipation interlayer 10 for temperature regulation and protection is provided inside the outer ring 8, the inner top of the outer ring 8 is fixedly connected to the inner ring furnace barrel 3 through a connecting block, an inner ring 6 is fixedly connected to the inner ring furnace barrel 3, and a first heat dissipation interlayer 10 for temperature regulation and protection is provided inside the inner ring 8 The second heat dissipation interlayer 11 is protected, the inner circle furnace drum 3 and the inner circle 6 are provided with an inner circle air inlet 4 at the upper ends, the inner circle furnace drum 3 and the inner circle 6 are installed at the bottom of the annular sealing groove provided on the inner side of the chassis 2, and the CVD reactor and the CVD reactor chassis are welded and fixed by a connecting pad 12; a first water pipe 14 is installed at the bottom end of the first heat dissipation interlayer 10, a second water pipe 15 is installed at the bottom end of the second heat dissipation interlayer 11, the bottom end of the outer circle air inlet 5 is fixedly connected with the air intake ring pipe 9 through an air pipe, and a ring pipe air supply port 16 for introducing a mixed gas of SiHCl3 and H2 is provided at the bottom end of the air intake ring pipe 9, a first electrode 18 for providing current is installed at the inner side of the first electrode mounting hole 13, and a second electrode 17 for providing current is installed at the inner side of the second electrode mounting hole 19.

[0026] As a further implementation of this solution, the position where the chassis 2 contacts the bottom of the outer ring 8 is the chassis outer ring, the position where the chassis 2 contacts the bottom of the inner ring 6 is the chassis inner ring, the diameter of the chassis 2 is 2500mm, the diameter of the chassis outer ring to the chassis inner ring is 600mm, and the diameter of the chassis inner ring is 950mm. The outer ring air inlet 5 is provided between the chassis outer ring and the chassis inner ring, the first electrode 18 is installed between the chassis outer ring and the chassis inner ring, and the second electrode 17 is installed on the inner side of the chassis inner ring, forming a double-layer furnace cover, which can make the incoming airflow form a U-shaped loop, and then the mixed gas can be preheated;

[0027] As a further implementation of this scheme, 8 pairs of second electrodes 17 are installed between the outer ring of the chassis and the inner ring of the chassis, 15 air inlets 5 of the outer ring are opened, 4 pairs of first electrodes 18 are installed on the inner side of the inner ring of the chassis, and one air outlet 7 of the inner ring is opened. Both the inner ring 6 and the outer ring 8 are cylindrical with an opening at the lower end, and the center points of the inner ring 6, the outer ring 8 and the chassis 2 are arranged on the same vertical line. Through the above arrangement, the stability of the overall structure of the device is further improved;

[0028] As a further implementation of this scheme, a plurality of inner ring air inlets 4 are provided, and the inner ring air inlets 4 are evenly distributed in an annular shape on the inner ring furnace barrel 3 and the upper end of the inner ring 6. The inner ring 6 is connected to the inner ring 8 through the inner ring air inlet 4, so that the preheated gas can be evenly transported to the inner ring 6.

[0029] As a further implementation of this scheme, the SiHCl3 and H2 mixed gas is a state in which high-purity trichlorosilane and hydrogen are mixed and vaporized in a certain molar ratio. SiHCl3 and H2 are heated at 1050 ~ The main equation for chemical vapor deposition reaction on the silicon core surface at 1150°C is:

[0030] SiHCl2(g)+H2(g)=Si(s)+3HCl(g)

[0031] 2SiHCl,(g)=Si(s)+2HCl(g)+SiCI(g), which can improve the uniformity of mixing SiHCl3 and H2 mixed gas;

[0032] As a further implementation of this solution, the first electrode mounting hole 13 is twice as large as the first electrode 18, the second electrode mounting hole 19 is twice as large as the second electrode 17, and both the first electrode 18 and the second electrode 17 are U-shaped, which can improve the stable current;

[0033] As a further implementation of the present scheme, partitions are installed inside the first heat dissipation interlayer 10 and the second heat dissipation interlayer 11. Two first water pipes 14 are installed at the bottom of the first heat dissipation interlayer 10, one of which is a water inlet pipe and the other is a water outlet pipe. Two second water pipes 15 are installed at the bottom of the second heat dissipation interlayer 11, one of which is a water inlet pipe and the other is a water outlet pipe, so as to facilitate the injection of cooling water for cooling and protect the furnace drum.

[0034] As a further implementation scheme of the present scheme, the connecting pad 12 is arranged in a ring shape, the vertical section of the outer ring furnace drum 1 is T-shaped, the outer diameter of the connecting pad 12 is equal to the outer diameter of the bottom end of the outer ring furnace drum 1, and the inner diameter of the connecting pad 12 is equal to the inner diameter of the bottom end of the outer ring furnace drum 1, thereby improving the stability of the connection between the CVD reactor and the CVD reactor chassis.

[0035] Workflow: After high-purity trichlorosilane and hydrogen are mixed and vaporized in a certain molar ratio, they enter the reduction furnace through the feed nozzle arranged on the reduction furnace base plate (i.e., through the air inlet ring 9), and chemical vapor deposition reaction is carried out on the silicon core surface at 1050~1150℃. The inner ring 6 and the outer ring 8 can independently control the temperature of each area. The temperature control is achieved by injecting cold water into the first heat dissipation interlayer 10 and the second heat dissipation interlayer 11. The mixed gas enters the position inside the outer ring 8 and outside the inner ring 6 for pre-mixing and heating. The reaction process strictly controls the temperature of the silicon rod in the furnace (the temperature is controlled between 1000℃-1200℃). When the preheated mixed gas rises to the top of the outer ring 8, it enters the inner ring 6 through the inner ring air inlet 4. The temperature gas field of the inner ring 6 will reach the optimal stable state. The gas reacted by the outer ring 8 will continue to react in a more stable gas field in the inner ring 6. The conversion rate of the inner ring 6 will be higher, and the zone melting capacity will be more stable. Finally, it is discharged through the inner ring outlet 7;

[0036] In actual use, the above arrangement uses a double-layer furnace cover, an outer ring furnace 1 has an outer ring air inlet 5 at the bottom, an inner ring furnace 3 has an inner ring air inlet 4 at the top, and an inner ring air outlet 7 at the bottom. The overall airflow forms a U-shaped loop, so the gas that has not completed the reduction reaction in the outer ring 8 will continue to react in the inner ring 6, thereby improving the conversion rate of a single furnace, increasing the overall production capacity, and reducing costs.

[0037] Embodiment 2:

[0038] See also Figure 1 , Figure 2 and Figure 4 , the utility model provides a technical solution:

[0039] A novel electronic-grade zone melting polysilicon CVD reaction system, wherein a mixed gas of SiHCl3 and H2 enters the inner ring 6 in the reverse direction through an inner ring gas outlet 7.

[0040] The same positions as those in Example 1 are not described again, except that:

[0041] After high-purity trichlorosilane and hydrogen are mixed and vaporized in a certain molar ratio, they enter the reduction furnace through the inner ring outlet 7 and perform chemical vapor deposition reaction on the silicon core surface at 1050-1150°C. The inner ring 6 and the outer ring 8 can independently control the temperature of each area. The temperature control is achieved by injecting cold water into the first heat dissipation interlayer 10 and the second heat dissipation interlayer 11. The mixed gas enters the position inside the inner ring 6 for pre-mixing and heating. The reaction process strictly controls the temperature of the silicon rod in the furnace (the temperature is controlled between 1000°C and 1200°C). When the pre-heated mixed gas rises to the top of the inner ring 6, it enters between the outer ring 8 and the inner ring 6 through the inner ring air inlet 4. The temperature gas field between the outer ring 8 and the inner ring 6 will reach the optimal stable state. The gas reacted by the inner ring 6 will continue to react in a more stable gas field at the position between the outer ring 8 and the inner ring 6. The conversion rate between the outer ring 8 and the inner ring 6 will be higher, and the zone melting capacity will be more stable. Finally, it is discharged through the outer ring air inlet 5.

[0042] In the above method, by adjusting the air inlet and outlet directions, the inner circle 6 is changed into the first reaction circle for preheating, and the outer circle 8 is the second reaction circle for the main reaction, which can also achieve the above effect.

[0043] This article uses specific examples to illustrate the principles and implementation methods of the utility model. The above examples are only used to help understand the method and core ideas of the utility model. The above is only a preferred implementation method of the utility model. It should be pointed out that due to the limitations of textual expression and the objective existence of infinite specific structures, ordinary technicians in this technical field can make several improvements, modifications or changes without departing from the principles of the utility model, and can also combine the above technical features in an appropriate manner; these improvements, modifications, changes or combinations, or the direct application of the concept and technical solution of the utility model to other occasions without improvement, should be regarded as the protection scope of the utility model.

Claims

1. A novel electronic grade zone melting polysilicon CVD reaction system, comprising a CVD reaction furnace chassis and a CVD reaction furnace, characterized in that: The CVD reactor chassis comprises a chassis (2), an inner ring air outlet (7) is provided in the middle of the chassis (2), an outer ring air inlet (5) is provided in an annular shape and equidistantly distributed on the inner side of the chassis (2), and a first electrode mounting hole (13) and a second electrode mounting hole (19) for mounting a first electrode (18) and a second electrode (17) are provided on the inner side of the chassis (2); The CVD reactor comprises an outer ring furnace barrel (1), an outer ring (8) is fixedly connected to the inner side of the outer ring furnace barrel (1), a first heat dissipation interlayer (10) for temperature regulation and protection is provided inside the outer ring (8), the top end of the inner ring (8) is fixedly connected to the inner ring furnace barrel (3) through a connecting block, the inner ring furnace barrel (3) is fixedly connected to the inner ring (6), a second heat dissipation interlayer (11) for temperature regulation and protection is provided inside the inner ring (6), an inner ring air inlet (4) is provided at the upper ends of the inner ring furnace barrel (3) and the inner ring (6), the bottom ends of the inner ring furnace barrel (3) and the inner ring (6) are mounted inside an annular sealing groove provided inside the chassis (2), and the CVD reactor and the CVD reactor chassis are fixed by welding via a connecting pad (12); A first water pipe (14) is installed at the bottom end of the first heat dissipation interlayer (10), a second water pipe (15) is installed at the bottom end of the second heat dissipation interlayer (11), the bottom end of the outer ring air inlet (5) is fixedly connected to the air inlet ring pipe (9) via an air pipe, the bottom end of the air inlet ring pipe (9) is provided with an air supply port (16) for allowing a mixed gas of SiHCl3 and H2 to enter, a first electrode (18) for providing current is installed inside the first electrode mounting hole (13), and a second electrode (17) for providing current is installed inside the second electrode mounting hole (19).

2. A novel electronic grade melt zone polysilicon CVD reaction system according to claim 1, characterized in that: The position where the chassis (2) contacts the bottom of the outer ring (8) is the chassis outer ring, and the position where the chassis (2) contacts the bottom of the inner ring (6) is the chassis inner ring. The diameter of the chassis (2) is 2500 mm, the diameter of the chassis outer ring to the chassis inner ring is 600 mm, and the diameter of the chassis inner ring is 950 mm. The outer ring air inlet (5) is provided between the chassis outer ring and the chassis inner ring. The first electrode (18) is installed between the chassis outer ring and the chassis inner ring, and the second electrode (17) is installed on the inner side of the chassis inner ring.

3. A novel electronic grade melt zone polysilicon CVD reaction system according to claim 1, characterized in that: There are 8 pairs of second electrodes (17) installed between the outer ring and the inner ring of the chassis, 15 air inlets (5) are provided on the outer ring, 4 pairs of first electrodes (18) are installed on the inner side of the inner ring of the chassis, and there is one air outlet (7) on the inner ring.

4. A novel electronic grade melt zone polysilicon CVD reaction system according to claim 1, characterized in that: The inner ring (6) and the outer ring (8) are both cylindrical with an open lower end, and the center points of the inner ring (6), the outer ring (8) and the chassis (2) are arranged on the same vertical line.

5. A novel electronic grade melt zone polysilicon CVD reaction system according to claim 1, characterized in that: The inner ring air inlets (4) are provided with a plurality of them. The inner ring air inlets (4) are evenly distributed in an annular shape on the inner ring furnace barrel (3) and the upper end of the inner ring (6). The interior of the inner ring (6) is connected to the interior of the outer ring (8) through the inner ring air inlets (4).

6. A novel electronic grade melt zone polysilicon CVD reaction system according to claim 1, characterized in that: The first electrode mounting hole (13) is twice as large as the first electrode (18), the second electrode mounting hole (19) is twice as large as the second electrode (17), and both the first electrode (18) and the second electrode (17) are U-shaped.

7. The novel electronic grade melt zone polysilicon CVD reaction system according to claim 1 is characterized by: The first heat dissipation interlayer (10) and the second heat dissipation interlayer (11) are both internally provided with partitions. Two first water pipes (14) are installed at the bottom end of the first heat dissipation interlayer (10), one of which is a water inlet pipe and the other is a water outlet pipe. Two second water pipes (15) are installed at the bottom end of the second heat dissipation interlayer (11), one of which is a water inlet pipe and the other is a water outlet pipe.

8. The novel electronic grade melt zone polysilicon CVD reaction system according to claim 1 is characterized by: The connection pad (12) is arranged in an annular shape, the vertical cross-section of the outer ring furnace drum (1) is T-shaped, the outer diameter of the connection pad (12) is equal to the outer diameter of the bottom end of the outer ring furnace drum (1), and the inner diameter of the connection pad (12) is equal to the inner diameter of the bottom end of the outer ring furnace drum (1).

9. The novel electronic grade melt zone polysilicon CVD reaction system according to claim 1 is characterized by: The SiHCl3 and H2 mixed gas enters the inner ring (6) in the reverse direction through the inner ring gas outlet (7).

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