Reactor for preparing electronic grade polycrystalline silicon and method for cleaning silicon core in reactor

Abstract

The invention provides a reactor for preparing electronic grade polycrystalline silicon and a method for cleaning a silicon core in the reactor, and belongs to the technical field of polycrystalline silicon production. The reactor for preparing the electronic grade polycrystalline silicon comprises a base plate, a furnace barrel covering the base plate and a silicon core arranged on the base plate, a raw material gas inlet and a byproduct gas outlet are formed in the base plate, and a first gas port and a second gas port are further formed in the base plate. According to the invention, the first gas port and the second gas port are formed in the chassis, and before raw material gas is introduced from the raw material gas inlet to prepare polycrystalline silicon, etching gas is introduced into the reactor through one of the first gas port and the second gas port to etch the silicon core, so that attachments, pollutants and oxides on the surface of the silicon core can be effectively stripped; an oxidation film on the surface of a silicon core can be effectively stripped, the oxygen content in a polycrystalline silicon product is reduced, and tail gas after etching carries pollutants to be discharged from the other group of gas ports, so that the cleanliness of the atmosphere in a reactor and a carrier is improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of polysilicon production, and particularly relates to a reactor for preparing electronic-grade polysilicon and a method for cleaning silicon cores in the reactor. Background Art

[0002] The production of electronic-grade polysilicon by the improved Siemens method uses electronic-grade high-purity trichlorosilane as a raw material, which is mixed with high-purity hydrogen in a certain ratio and then fed into a reactor (bell reactor). Multiple pairs of silicon cores arranged in a concentric circle form are provided on the chassis. After applying a certain voltage and current, the silicon cores are heated to about 1000 °C for polysilicon deposition reaction.

[0003] The purity of electronic-grade polysilicon is usually above 9N, and it has strict control requirements for impurities. During the production process, the cleanliness of the reactor, the cleanliness of the silicon cores, and the environmental cleanliness will introduce foreign impurities into the polysilicon product, resulting in insufficient product purity. To improve the purity of electronic-grade polysilicon, generally, the purity is improved from aspects such as the reactor and the silicon cores. For example, on the inner wall of the reactor, a silver plating or a silver-steel composite is carried out to inhibit the precipitation of metal impurities on the inner wall in a chlorine-containing atmosphere, thereby avoiding contamination of the polysilicon. Another example is to perform pickling treatment on the silicon cores to improve the cleanliness of the silicon core surface and reduce the influence of the silicon cores on the purity of the polysilicon product. However, due to the intermittent disassembly and assembly of the reactor during the production process, and the periodic installation of the silicon cores, during the operation process, water vapor in the environment, floating particulate matter, dust attachments inside the furnace barrel, and contamination during the manual operation process are all inevitable. As a result, attachments and contamination are formed on the surface of the silicon cores, introducing impurities during the reaction deposition of polysilicon, resulting in unstable or abnormal quality of the electronic-grade polysilicon product. Therefore, how to further improve the cleanliness inside the reactor, especially the silicon cores, has become an urgent technical problem in this field. Summary of the Invention

[0004] The purpose of the present invention is to provide a reactor for preparing electronic-grade polysilicon and a method for cleaning silicon cores in the reactor. The reactor provided by the present invention can improve the cleanliness of the silicon cores in the reactor, thereby improving the purity of electronic-grade polysilicon.

[0005] To achieve the above-mentioned invention purpose, the present invention provides the following technical solutions: The present invention provides a reactor for preparing electronic-grade polysilicon, including a chassis, a furnace barrel covering the chassis, and silicon cores provided on the chassis. A raw material inlet and a by-product outlet are provided on the chassis, and a first air port and a second air port are also provided on the chassis.

[0006] Preferably, the silicon cores are arranged in a concentric array around the center of the chassis; the first air port is located on the chassis inside the innermost silicon core, and the second air port is located on the chassis outside the outermost silicon core; the number of the first air ports is 1; the number of the second air ports is an even number.

[0007] Preferably, the first air port is arranged at the center of the chassis, and the second air ports are symmetrically distributed in pairs with the first air port as the center.

[0008] Preferably, the number of the second air ports is 4, 6 or 8.

[0009] The present invention also provides a method for cleaning the silicon cores in the reactor of the above technical solution, including: Replacing the internal atmosphere of the reactor with hydrogen and then sealing it, then heating the silicon cores, and then opening the first air port and the second air port, introducing an etching gas into the reactor to etch the silicon cores, and discharging the obtained etching reactants from the reactor; the etching gas is introduced through the first air port, and the obtained etching reactants are discharged through the second air port, or the etching gas is introduced through the second air port, and the obtained etching reactants are discharged through the first air port.

[0010] Preferably, the etching gas is a mixture of hydrogen chloride and hydrogen, or hydrogen chloride.

[0011] Preferably, when the etching gas is hydrogen chloride, the flow rate of the hydrogen chloride is 10-200 Nm 3 / h, and the temperature of the silicon cores is 800-900 °C.

[0012] Preferably, when the etching gas is a mixture of hydrogen chloride and hydrogen, the flow rate of the hydrogen chloride is 10-200 Nm 3 / h, the flow rate of the hydrogen is 10-300 Nm 3 / h, and the temperature of the silicon cores is 900-1000 °C.

[0013] Preferably, the time for introducing the etching gas is 5-30 min.

[0014] Preferably, the number of cleaning times is more than 2, and the inlets of the etching gas and the outlets of the etching reactants are alternately changed for adjacent two cleanings.

[0015] The present invention provides a reactor for preparing electronic-grade polysilicon, comprising a chassis, a furnace barrel covered on the chassis, and a silicon core arranged on the chassis, wherein the chassis is provided with a raw material air inlet and a byproduct air outlet, and the chassis is also provided with a first air inlet and a second air inlet. The reactor provided by the present invention is provided with a first air inlet and a second air inlet on the chassis, and before the raw material gas is introduced into the raw material air inlet to prepare polysilicon, the etching gas is introduced into the reactor through one of the first air inlet and the second air inlet to etch the silicon core, which can effectively strip off the attachments, pollutants and oxides on the surface of the silicon core, and avoid impurities from entering the polysilicon under the conditions of incomplete cleaning of the silicon core, environmental pollution or improper human operation, and at the same time, the oxide film on the surface of the silicon core can be effectively stripped off, and the oxygen content in the polysilicon product can be reduced. The tail gas after etching carries pollutants and is discharged from another group of air inlets, thereby improving the cleanliness of the atmosphere and the carrier inside the reactor, and further improving the purity of the electronic-grade polysilicon. Experimental results show that the purity of the electronic-grade polysilicon prepared by the reactor provided by the present invention is 10N or above. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 This is a schematic diagram of the structure of the chassis in the reactor of Example 2. DETAILED DESCRIPTION

[0017] The present invention provides a reactor for preparing electronic grade polysilicon, comprising a chassis, a furnace barrel covered on the chassis and a silicon core arranged on the chassis, wherein the chassis is provided with a raw material air inlet and a by-product air outlet, and the chassis is also provided with a first air port and a second air port.

[0018] The reactor provided by the invention comprises a bottom plate, a furnace barrel covered on the bottom plate and a silicon core arranged on the bottom plate.

[0019] The present invention has no special limitation on the material and size of the furnace barrel and the bottom plate, and furnace barrels and bottom plates well known to those skilled in the art may be used.

[0020] The present invention has no special limitation on the size of the silicon core, and any silicon core well known to those skilled in the art may be used.

[0021] In the present invention, the silicon cores are arranged in a concentric array around the center of the chassis.

[0022] like Figure 1 As shown, as an embodiment of the present invention, the silicon cores are arranged in a concentric array around the center of the chassis. The present invention arranges the silicon cores in a concentric array around the center of the chassis, which helps to increase the yield of polysilicon and reduce production costs and energy consumption.

[0023] like Figure 1As shown, in one embodiment of the present invention, the silicon cores are arranged in two concentric circular arrays around the center of the chassis; the number of silicon cores in the inner circle is 4, and the number of silicon cores in the outer circle is 8. The silicon cores in the same circle are arranged at equal intervals.

[0024] The present invention does not have special limitations on the total number of the silicon cores, which can be determined according to the device specifications according to common knowledge in the art, such as 12 pairs, 24 pairs or 36 pairs.

[0025] In the present invention, a raw material inlet and a by-product outlet are provided on the chassis. The present invention does not have special limitations on the sizes and distribution manners of the raw material inlet and the by-product outlet, and can be adjusted according to actual needs by means well-known to those skilled in the art. In the present invention, the raw material inlet is used to introduce a mixed gas of trichlorosilane and hydrogen, which is the raw material gas for polysilicon; the by-product outlet is used to discharge the raw material gas and by-products (such as chlorosilane, hydrogen and hydrogen chloride).

[0026] As Figure 1 shown, in one embodiment of the present invention, the raw material inlets are arranged in two concentric arrays around the center of the chassis; the inner raw material inlets are arranged inside the inner silicon cores; the number of the inner raw material inlets is 4; the outer raw material inlets are arranged between the inner silicon cores and the outer silicon cores; the number of the outer raw material inlets is 8. The raw material inlets in the same circle are arranged at equal intervals. Setting the positions of the raw material inlets in the above positions in the present invention can enable the raw material gas to be evenly deposited on the surfaces of the silicon cores, improving the production efficiency.

[0027] As Figure 1 shown, in one embodiment of the present invention, the by-product outlets are arranged on the chassis outside the outer silicon cores and are arranged in a circular array at equal intervals with the center of the chassis as the center of the circle; the number of the by-product outlets is 4. Setting the positions of the by-product outlets in the above positions in the present invention is beneficial to the better discharge of the by-products.

[0028] In the present invention, a first gas port and a second gas port are further provided on the chassis. In the present invention, one of the first gas port and the second gas port is used to introduce an etching gas to etch the silicon cores, and the other is used to discharge etching products such as trichlorosilane and silicon tetrachloride, which are chlorosilane and hydrogen.

[0029] The present invention does not have special limitations on the sizes of the first gas port and the second gas port, and can be adjusted according to actual needs.

[0030] In the present invention, the first gas port is located on the chassis inside the innermost silicon core; the second gas port is located on the chassis outside the outermost silicon core; the second gas ports are symmetrically distributed in pairs with the first gas port as the center. Setting the first gas port and the second gas port in the above positions in the present invention is beneficial to uniformly etching the silicon core, thereby improving the cleanliness of the silicon core in the reactor and further improving the purity of electronic-grade polysilicon.

[0031] As Figure 1 shown, the number of the first gas ports is 1; the number of the second gas ports is an even number. As an implementation manner, the number of the second gas ports can be 4, 6 or 8.

[0032] As Figure 1 shown, in an embodiment of the present invention, the first gas port is located at the center of the chassis; the number of the second gas ports is 4; the second gas ports are arranged in a circular pattern around the center of the chassis, and the second gas ports are arranged at equal intervals.

[0033] The reactor provided by the present invention is provided with the first gas port and the second gas port on the chassis. Before introducing the raw material gas through the raw material inlet to prepare polysilicon, the etching gas is introduced into the reactor through one of the first gas port and the second gas port to etch the silicon core, which can effectively strip the attachments, pollutants and oxides on the surface of the silicon core, avoid impurities from entering the polysilicon in the case of incomplete cleaning of the silicon core, environmental pollution or improper manual operation, etc., and at the same time can effectively strip the oxide film on the surface of the silicon core, reduce the oxygen content in the polysilicon product, and the tail gas after etching carries pollutants and is discharged from the other gas port, thereby improving the cleanliness of the internal atmosphere and the carrier in the reactor and further improving the purity of electronic-grade polysilicon.

[0034] The starting point of the present invention is to thoroughly clean the silicon core after the reactor is installed. Through etching with the etching gas, the surface of the silicon core is purified, thereby improving the quality of polysilicon.

[0035] The present invention also provides a method for cleaning the silicon core in the reactor described in the above technical solution, including: Replacing the internal atmosphere of the reactor with hydrogen and then sealing it, then heating the silicon core, then opening the first gas port and the second gas port, introducing the etching gas into the reactor to etch the silicon core, and discharging the obtained etching reactants from the reactor; the etching gas is introduced through the first gas port, and the obtained etching reactants are discharged through the second gas port, or the etching gas is introduced through the second gas port, and the obtained etching reactants are discharged through the first gas port.

[0036] In the present invention, the operation of replacing the internal atmosphere of the reactor with hydrogen is preferably to seal the reactor, then open the raw material inlet, introduce nitrogen into the reactor for the first replacement, then introduce hydrogen into the reactor for the second replacement, and then close the raw material inlet.

[0037] The present invention has no special limitation on the operation of the sealing. It is only necessary to use the well-known operation for sealing in the art and pass the leak detection.

[0038] The present invention has no special limitation on the operation of opening the raw material inlet. It is only necessary to use the well-known operation in the art.

[0039] In the present invention, the preferred flow rate of the nitrogen introduced is 50-200 Nm 3 / h; the preferred time for introducing the nitrogen is 0.5-1.5 h, more preferably 1 h. As an implementation manner, the flow rate of the nitrogen introduced can be 100-150 Nm 3 / h. By introducing nitrogen, the present invention can displace the air in the reactor and avoid the influence of air on the purity of polysilicon.

[0040] In the present invention, the preferred flow rate of the hydrogen introduced is 50-200 Nm 3 / h; the preferred time for introducing the hydrogen is 0.5-1.5 h, more preferably 1 h. As an implementation manner, the flow rate of the hydrogen introduced can be 100-150 Nm 3 / h. By introducing hydrogen, the present invention can displace the nitrogen in the reactor. Hydrogen is the gas required for the preparation of polysilicon and will not affect the purity of polysilicon.

[0041] The present invention has no special limitation on the operation of closing the raw material inlet. It is only necessary to use the well-known operation in the art.

[0042] The present invention has no special limitation on the operation of heating the silicon core. It is only necessary to use the well-known operation in the art, such as the operation of breaking through the silicon core, applying voltage and current.

[0043] The present invention has no special limitation on the operation of opening the first gas port and the second gas port. It is only necessary to use the well-known operation in the art.

[0044] In the present invention, the etching gas is preferably a mixture of hydrogen chloride and hydrogen, or hydrogen chloride. The present invention uses a mixture of hydrogen chloride and hydrogen, or hydrogen chloride as the etching gas, which can react with the silicon core at high temperature to generate chlorosilanes such as trichlorosilane and tetrachlorosilane and hydrogen. The tail gas after etching is not recycled as the raw material gas and is treated harmlessly as waste gas.

[0045] In the present invention, when the etching gas is hydrogen chloride, the preferred flow rate of the hydrogen chloride is 10-200 Nm 3 / h; the temperature of the silicon core is preferably 800 - 900 °C; the purity of the hydrogen chloride is preferably above 5N, more preferably 6N. As an embodiment, the flow rate of the hydrogen chloride can be 50 - 150 Nm 3 / h, and can also be 100 Nm 3 / h; the temperature of the silicon core can be 810 °C, 820 °C, 830 °C, 840 °C, 850 °C, 860 °C, 870 °C, 880 °C or 890 °C. Limiting the temperature of the hydrogen chloride and the silicon core within the above ranges in the present invention can improve the etching uniformity, thereby further improving the purity of the electronic-grade polysilicon.

[0046] In the present invention, when the etching gas is a mixture of hydrogen chloride and hydrogen, the flow rate of the hydrogen chloride is preferably 10 - 200 Nm 3 / h; the flow rate of the hydrogen is preferably 10 - 300 Nm 3 / h; the temperature of the silicon core is preferably 900 - 1000 °C; the purity of the hydrogen chloride is preferably ≥5N, more preferably 6N. As an embodiment, the flow rate of the hydrogen chloride can be 50 - 150 Nm 3 / h, and can also be 100 Nm 3 / h; the flow rate of the hydrogen can be 50 - 250 Nm 3 / h, and can also be 100 - 150 Nm 3 / h; the temperature of the silicon core can be 910 °C, 920 °C, 930 °C, 940 °C, 950 °C, 960 °C, 970 °C, 980 °C or 990 °C. Limiting the temperature of the hydrogen chloride, hydrogen and the silicon core within the above ranges in the present invention can improve the etching uniformity, thereby further improving the purity of the electronic-grade polysilicon.

[0047] In the present invention, the etching gas is introduced through the first gas port, and the obtained etching reactant is discharged through the second gas port, or the etching gas is introduced through the second gas port, and the obtained etching reactant is discharged through the first gas port.

[0048] In the present invention, the time for introducing the etching gas is preferably 5 - 30 min. As an embodiment, the time for introducing the etching gas can be 10 min, 15 min, 20 min or 25 min. Limiting the time for introducing the etching gas within the above ranges in the present invention can further improve the etching uniformity, thereby further improving the purity of the electronic-grade polysilicon.

[0049] In the present invention, the number of cleanings is preferably more than 2 times, more preferably an even number; the inlet of the etching gas and the outlet of the etching reactant of two adjacent cleanings are preferably replaced alternately. As an embodiment, the number of cleanings can be 4 or 6 times. The present invention realizes the swapping of the inlet and outlet by repeatedly switching the pipelines, which can change the flow direction of the etching gas and avoid uneven etching of the silicon core, so that the dirt on the surface of the silicon core is completely removed as the surface of the silicon core is etched and peeled off.

[0050] When the etching gas etches the silicon core, the present invention repeats the process for many times and repeatedly switches the first gas port and the second gas port, which can effectively utilize the repeated flushing effect of hydrogen chloride, accelerate the stripping and shedding of pollutants, and improve the effective contact between hydrogen chloride and the surface of the silicon core, avoid the generation of airflow dead zones, and cause the problem of incomplete etching of the silicon core, thereby achieving uniform etching of all parts of the silicon core and improving the cleanliness of the surface of the silicon core.

[0051] In the present invention, after each cleaning is completed, preferably one of the first and second gas ports is closed, and then the reactor is evacuated through the other gas port, and then the gas port is closed. The present invention uses vacuuming to exhaust the etching gas and tail gas in the reactor and completely exhaust pollutants.

[0052] The present invention has no special limitation on the vacuuming operation, and the vacuuming can be carried out to below 3 Pa and maintained for 10 minutes.

[0053] The present invention can effectively strip off the attachments and pollutants on the surface of the silicon core by performing an etching reaction on the surface of the silicon core, thereby preventing impurities from entering the polysilicon product in the case of incomplete cleaning of the silicon core, environmental pollution or improper human operation; a first air port and a second air port are respectively arranged on the chassis, and the tail gas after etching carries pollutants and is discharged from one of the groups of air ports, thereby preventing the pollutants stripped from the surface of the silicon core from entering the tail gas (gas outlet) of the reaction material and entering the high-purity material after the tail gas is dry-recovered, thereby reducing the purity of the raw material chlorosilane; utilizing the characteristic that hydrogen chloride and silicon undergo a corrosion reaction at high temperature, the pollutants on the surface of the silicon core in the reactor are removed, the cleanliness of the surface of the silicon core is improved, and thus the quality of the electronic-grade polysilicon deposited on the surface of the silicon core is improved; during the etching process, the direction of the airflow is switched to improve the uniformity and cleanliness of the silicon core etching, thereby avoiding the problem of dead zones or incomplete removal of pollutants during the etching process.

[0054] The technical solutions in the present invention will be described clearly and completely below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0055] Example 1 A reactor consists of a chassis, a furnace barrel covering the chassis, and silicon cores arranged on the chassis. The chassis is provided with a raw material inlet and a by-product outlet, and the chassis is also provided with a first gas port and a second gas port.

[0056] Example 2 A reactor for preparing electronic-grade polysilicon consists of a chassis, a furnace barrel covering the chassis, and silicon cores arranged on the chassis. The chassis is provided with a raw material inlet and a by-product outlet, and the chassis is also provided with a first gas port and a second gas port; The structural schematic diagram of the chassis is as Figure 1 shown; As Figure 1 shown, the silicon cores are arranged in two concentric circle arrays around the center of the chassis; the number of inner circle silicon cores is 4, and the number of outer circle silicon cores is 8. The silicon cores in the same circle are arranged at equal intervals; The raw material inlets are arranged in two concentric arrays around the center of the chassis; among them, the inner circle raw material inlets are arranged inside the inner circle silicon cores, and the outer circle raw material inlets are arranged between the inner circle silicon cores and the outer circle silicon cores; the number of inner circle raw material inlets is 4, and the number of outer circle raw material inlets is 8; the raw material inlets in the same circle are arranged at equal intervals; The by-product outlets are arranged on the chassis outside the outer circle silicon cores and are arranged at equal intervals in a circular array with the center of the chassis as the center; the number of the by-product outlets is 4; The first gas port is located at the center of the chassis, and the number of the first gas ports is 1; The second gas ports are located on the chassis outside the outermost circle silicon cores, and the second gas ports are symmetrically distributed in pairs with the first gas port as the center; the number of the second gas ports is 4; the adjacent two second gas ports are arranged at equal intervals.

[0057] Example 3 A method for cleaning the silicon cores in the reactor for preparing electronic-grade polysilicon in Example 2 is as follows: (1) Seal the reactor, then open the raw material inlet, introduce nitrogen into the reactor for the first replacement, then introduce hydrogen into the reactor for the second replacement, and then close the raw material inlet; among them, the flow rate of nitrogen introduced is 100 Nm 3 / h; the time for introducing nitrogen is 1 h; the flow rate of hydrogen introduced is 100 Nm 3 / h; the time for introducing hydrogen is 1 h; (2) Heat the silicon cores, then open the first gas port and the second gas ports, introduce the etching gas into the reactor through the first gas port to etch the silicon cores, and discharge the obtained etching reactants out of the reactor through the second gas ports; among them, the etching gas is hydrogen chloride, and the flow rate is 100 Nm3 / h, the temperature of the silicon core is 800 °C, and the etching gas is introduced for 30 min; the purity of hydrogen chloride is preferably 5N; (3)Close the first gas port, then evacuate the reactor through the second gas port for 10 min to below 3 Pa, and then change the second gas port.

[0058] Use the reactor cleaned in Example 3 to prepare electronic-grade polysilicon. Feed the mixed gas of trichlorosilane and hydrogen as the raw material gas through the raw material inlet. The temperature of the silicon core is 1050 °C, and the tail gas is discharged from the by-product outlet to obtain electronic-grade polysilicon with a purity of 10N.

[0059] Example 4 A method for cleaning the silicon core in the reactor used in Example 2 for preparing electronic-grade polysilicon is as follows: According to the cleaning method of Example 3, repeat the cleaning 4 times; the inlets of the etching gas and the outlets of the etching reactants for two adjacent cleanings are not alternately changed; After each cleaning is completed, close the first gas port, then evacuate the reactor through the second gas port and maintain it for 10 min to below 3 Pa, and then close the second gas port.

[0060] Use the reactor cleaned in Example 4 to prepare electronic-grade polysilicon. Feed the mixed gas of trichlorosilane and hydrogen as the raw material gas through the raw material inlet. The temperature of the silicon core is 1050 °C, and the tail gas is discharged from the by-product outlet to obtain electronic-grade polysilicon with a purity of 11N.

[0061] Comparing Example 3 and Example 4, it can be seen that increasing the number of cleanings can improve the purity of electronic-grade polysilicon, but not alternately changing the inlets of the etching gas and the outlets of the etching reactants for two adjacent cleanings will result in incomplete and uneven etching.

[0062] Example 5 According to the cleaning method of Example 3, repeat the cleaning 4 times, and alternately change the inlets of the etching gas and the outlets of the etching reactants for two adjacent cleanings; After each cleaning is completed, close the first gas port, then evacuate the reactor through the second gas port and maintain it for 10 min to below 3 Pa, and then close the second gas port.

[0063] Use the reactor cleaned in Example 5 to prepare electronic-grade polysilicon. Feed the mixed gas of trichlorosilane and hydrogen as the raw material gas through the raw material inlet. The temperature of the silicon core is 1050 °C, and the tail gas is discharged from the by-product outlet to obtain electronic-grade polysilicon with a purity of over 11N.

[0064] Comparing Example 4 and Example 5, it can be seen that alternately changing the inlets of the etching gas and the outlets of the etching reactants for two adjacent cleanings can improve the purity of electronic-grade polysilicon.

[0065] Comparative Example 1 (existing method, without etching) The difference from Example 2 is that the first gas port and the second gas port are not provided, and other conditions are the same as those in Example 2.

[0066] The reactor of Comparative Example 1 was purged with hydrogen, then sealed, and then the raw material inlet was opened. Nitrogen was introduced into the reactor for the first purge, and then hydrogen was introduced into the reactor for the second purge. Subsequently, the raw material inlet was closed; among them, the flow rate of nitrogen introduced was 100 Nm 3 / h; the time for introducing nitrogen was 1 h; the flow rate of hydrogen introduced was 100 Nm 3 / h; the time for introducing hydrogen was 1 h. Then, electronic-grade polysilicon was prepared. A mixed gas of trichlorosilane (impurity content less than 10 ppta) and hydrogen (purity > 9N) was introduced from the raw material inlet. The temperature of the silicon core was 1050 °C, and the tail gas was discharged from the by-product gas outlet. The purity stability of the obtained electronic-grade polysilicon was not high, and it could only reach 8 - 9N.

[0067] Comparing Comparative Example 1 and Example 2, it can be seen that by setting the first gas port and the second gas port, the present invention can improve the cleanliness of the reactor, and thus improve the purity of electronic-grade polysilicon.

[0068] From the above examples and comparative examples, it can be seen that the reactor provided by the present invention can improve the cleanliness of the reactor, and thus improve the purity of electronic-grade polysilicon.

[0069] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A reactor for preparing electronic grade polysilicon, comprising a chassis, a furnace barrel covered on the chassis and a silicon core arranged on the chassis, wherein the chassis is provided with a raw material air inlet and a by-product air outlet, characterized in that: The chassis is also provided with a first air port and a second air port.

2. The reactor according to claim 1, characterized in that The silicon cores are arranged in a concentric array around the center of the chassis; the first air ports are located on the chassis inside the innermost circle of silicon cores, and the second air ports are located on the chassis outside the outermost circle of silicon cores; the number of the first air ports is 1; the number of the second air ports is an even number.

3. The reactor according to claim 2, characterized in that The first air port is arranged at the center of the chassis, and the second air ports are symmetrically distributed in pairs with the first air port as the center.

4. The reactor according to claim 2 or 3, characterized in that The number of the second gas ports is 4, 6 or 8.

5. A method for cleaning a silicon core in a reactor according to any one of claims 1 to 4, characterized in that: include: The internal atmosphere of the reactor is replaced with hydrogen and then sealed, and then the silicon core is heated, and then the first gas port and the second gas port are opened to pass the etching gas into the reactor to etch the silicon core, and the obtained etching reactants are discharged from the reactor; The etching gas is introduced through the first gas port, and the obtained etching reactant is discharged through the second gas port, or the etching gas is introduced through the second gas port, and the obtained etching reactant is discharged through the first gas port.

6. The method according to claim 5, characterized in that The etching gas is a mixture of hydrogen chloride and hydrogen, or hydrogen chloride.

7. The method according to claim 6, characterized in that When the etching gas is hydrogen chloride, the flow rate of hydrogen chloride is 10~200Nm 3 / h, and the temperature of the silicon core is 800~900℃.

8. The method according to claim 6, characterized in that When the etching gas is a mixture of hydrogen chloride and hydrogen, the flow rate of the hydrogen chloride is 10-200 Nm 3 / h, the flow rate of hydrogen is 10~300Nm 3 / h, the temperature of the silicon core is 900~1000℃.

9. The method according to claim 5, characterized in that The etching gas is introduced for 5 to 30 minutes.

10. The method according to claim 5, characterized in that The cleaning is performed more than twice, and the inlet of the etching gas and the outlet of the etching reactant are alternately replaced in two adjacent cleanings.

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