Method for producing granular polycrystalline silicon by plasma method

Abstract

The invention provides a method for producing granular polycrystalline silicon by a plasma method, and aims to solve the technical problems of low primary conversion rate of silicon raw materials and unstable quality of the prepared polycrystalline silicon in the existing polycrystalline silicon preparation process. According to the method, atomized silicon raw materials are fed into a plasma reaction chamber in a multi-stage mode at the speed of 0.1 m / min to 100 m / min, plasma reaction is carried out at the temperature ranging from 1500 DEG C to 5000 DEG C and the pressure ranging from 0 MPa to 10 MPa in the plasma carrier gas atmosphere, and therefore silicon liquid drops and tail gas are generated. The silicon liquid drops are led to a forming chamber to form silicon particles, the tail gas can be subjected to corresponding silicon powder collection and gas recovery through a gas-solid treatment device, and at least one stage of jet feeding in the multi-stage jet feeding is rotary feeding. The quality stability of the silicon particles prepared by the method is high, the yield of the silicon particles reaches 90% or above, and the production efficiency is greatly improved.

Description

Technical Field

[0001] The present application relates to the field of polysilicon production, and in particular to a method for producing granular polysilicon by a plasma process. Background Art

[0002] Polysilicon is the basic raw material of the photovoltaic industry, and the demand for polysilicon is increasing year by year. Currently, there are two major schools of thought in the preparation of polysilicon, namely the modified Siemens method and the silane fluidized bed method.

[0003] The modified Siemens method is the mainstream method in the industry. It mainly uses hydrogen to reduce trichlorosilane and produces it on a silicon core by chemical vapor deposition. Since the reduction of trichlorosilane by hydrogen is a reversible reaction, a large number of side reactions will occur during the main reaction, generating chlorosilanes such as silicon tetrachloride and dichlorodihydrosilane, which will slow down the reaction. In order to remove the by-products from the reaction environment in time and promote the smooth progress of the main reaction, the tail gas generated by the reduction will be immediately taken away, resulting in a waste of energy. Moreover, the current maximum conversion rate of trichlorosilane through the reduction furnace is only 20%, which is inefficient.

[0004] The silanization fluidized bed method mainly utilizes thermal cracking of silane gas to perform chemical vapor deposition production on seed crystals. Since the method uses a fluidized bed in the production process, it can only produce granular polysilicon (commonly known as granular silicon). Although this method uses silane gas with the lowest reaction temperature, which can greatly reduce the reaction energy consumption while ensuring continuous production, the production process is inseparable from seed crystals, and the quality of the prepared polysilicon is highly dependent on the purity of the seed crystals. Since the seed crystals are silicon particles with micron-sized particles, they are extremely susceptible to contamination during the production and transportation processes, which greatly affects the quality control stability of polysilicon products. In addition, due to the limitation of the deposition rate, although the conversion rate of silane gas in one pass is higher than that of the Siemens method, it is still only 20~30%, resulting in the need to purify the gas after the reaction in addition to the need to deal with silicon dust, which greatly increases the production cost. Summary of the invention

[0005] The present invention provides a method for producing granular polysilicon by a plasma process to solve the problems raised in the above background technology.

[0006] A method for producing granular polysilicon by a plasma process comprises the following steps:

[0007] S10, raw material preparation: atomizing the silicon raw material with an atomizer;

[0008] S20, plasma reaction: the atomized silicon raw material is fed into the plasma reaction chamber by multi-stage injection at 0.1-100 m³ / min, and the plasma reaction is carried out at a temperature of 1500-5000°C, a pressure of 0-10 MPa, and a plasma carrier gas atmosphere, thereby generating silicon droplets and tail gas;

[0009] S30, molding: the silicon droplets are led to a molding chamber connected below the plasma reaction chamber to be cooled into silicon particles;

[0010] Among the multi-stage injection feeding, at least one stage of injection feeding is rotary feeding.

[0011] Furthermore, the plasma reaction adopts a passive plasma generator, and the passive plasma adopted by the passive plasma generator is a plasma whose plasma energy and supply method do not contact the plasma.

[0012] Furthermore, the passive plasma device is any one of an inductively coupled plasma reactor, a microwave plasma reactor, a plasma cloud reactor, a dielectric barrier plasma reactor, and a negative pressure plasma reactor.

[0013] Furthermore, the method for producing granular polysilicon by plasma method also includes: S31, tail gas treatment: the tail gas generated by S20 is subjected to gas-solid separation treatment to realize the collection of silicon powder, and the classified recovery of plasma carrier gas and silicon material reaction gas; wherein, the recovered plasma carrier gas is used for carrier gas supplement of plasma reaction; the recovered silicon material reaction gas is used as silicon raw material for plasma reaction.

[0014] Furthermore, the silicon raw material is one or more of silane, monochlorosilane, dichlorosilane, trichlorosilane, silicon tetrachloride and the like.

[0015] Furthermore, the plasma carrier gas may be one or more of hydrogen, argon, chlorine, hydrogen chloride, helium, etc.

[0016] Furthermore, the plasma reaction chamber is provided with upper and lower stages of injection feeding.

[0017] Furthermore, the upper-stage injection feed is a rotary feed, which can be achieved by rotatably connecting the nozzle ring to the mounting tube and installing the mounting tube to the plasma reaction chamber; the nozzle adopts a bent tube structure.

[0018] Furthermore, the plasma generator, the atomizer, the nozzle group and each connecting pipe are made of high temperature resistant non-metallic material.

[0019] Furthermore, the yield of the silicon particles is greater than 90%.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] (1) Taking advantage of the high temperature and high reaction activity of plasma, this scheme adopts a passive plasma generator and uses a multi-stage feeding method to allow silicon materials to enter the plasma reaction chamber with a feed flow rate of 0.1~100m³ / min. The plasma reaction temperature is regulated to be 1500~5000℃ and the pressure is 0~10MPa. While maintaining the stability of product quality, it can also maximize the product quality. Moreover, the primary conversion rate of silicon raw materials can reach more than 90%, and the yield of polysilicon produced can reach more than 90%, greatly improving the production efficiency.

[0022] (2) By performing gas-solid separation on the tail gas, the collection of silicon powder, the classified recycling of plasma carrier gas and silicon material reaction gas are realized, and energy is saved. Among them, the recycled silicon material reaction gas can be used as silicon raw material again, which improves the material utilization rate and the output of polysilicon; and the recycled plasma carrier gas can enter the plasma reaction chamber again to maintain the stability of the plasma reaction. Therefore, the plasma reaction only needs to add additional gas in the initial stage, and can subsequently rely on the gas generated by the reaction to operate automatically, which is conducive to continuous production. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0024] Figure 1 A flow chart of a method for producing granular polysilicon by a plasma method according to the present application;

[0025] Figure 2 A schematic diagram of the connection of equipment used in a method for producing granular polysilicon by a plasma method of the present application;

[0026] Figure 3 This is a schematic structural diagram of a nozzle ring assembly installation tube used in a method for producing granular polysilicon by a plasma method of the present application.

[0027] Reference numerals:

[0028] 1. Plasma reaction chamber; 10. Plasma reactor; 12. Injection feed end; 13. Nozzle ring; 14. Mounting tube; 15. Initial plasma carrier gas input end;

[0029] 3. Molding room; 32. Unloading end of molding room;

[0030] 4. Gas-solid separation device;

[0031] 51. Reaction gas recovery pipeline; 52. Carrier gas recovery pipeline;

[0032] 6. Atomizer. DETAILED DESCRIPTION

[0033] In the following, only some exemplary embodiments are briefly described. As those skilled in the art will appreciate, the described embodiments may be modified in various ways without departing from the spirit or scope of the present invention. Therefore, the drawings and descriptions are considered to be exemplary and non-restrictive in nature.

[0034] In the present invention, unless otherwise clearly specified and limited, the term "connection" and other terms should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection; it can be directly connected or indirectly connected through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present utility model can be understood according to specific circumstances.

[0035] The embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0036] Example 1-1

[0037] 1. Preparation of granular polysilicon:

[0038] The present invention provides a plasma method for producing granular polysilicon. Figure 1-Figure 3 , the polysilicon production method comprises the following steps:

[0039] S10, raw material preparation: atomize the silicon raw material with an atomizer 6; wherein the selected silicon raw material can be one or more of silane, monochlorosilane, dichlorosilane, trichlorosilane, silicon tetrachloride, etc. The atomizer used can be any one of a thermal vaporizer, an ultrasonic atomizer, a compression atomizer, and a bubbling atomizer.

[0040] S20, plasma reaction: the atomized silicon raw material is fed into the plasma reaction chamber 1 in multiple stages at 0.1~100m³ / min, and the plasma reaction is carried out at a temperature of 1500~5000℃, a pressure of 0~10MPa, and a plasma carrier gas atmosphere, thereby generating silicon droplets and tail gas. Among them, at least one stage of the multi-stage injection feeding is a rotary feeding. The rotary feeding can be achieved by rotating the nozzle ring 13 and the mounting tube 14, and then rotating the mounting tube 14 to the plasma reaction chamber 1, and the nozzle adopts a bent pipe structure. The plasma generator 10 used in the plasma reaction is a passive plasma generator. The passive plasma used by the passive plasma generator is a plasma whose plasma energy and supply mode are not in contact with the plasma, which is conducive to reducing the introduction of metal impurities during the plasma reaction. The passive plasma generator can specifically be an inductively coupled plasma reactor, a microwave plasma reactor, a plasma cloud reactor, a dielectric barrier plasma reactor, a negative pressure plasma reactor, etc. One or more of hydrogen, argon, chlorine, hydrogen chloride, helium and the like are selected as initial plasma carrier gases and introduced into the plasma reaction chamber 1 .

[0041] S30, the process of forming silicon droplets into silicon particles may include the following steps:

[0042] S301, cooling: the unloading end 32 of the molding chamber is blocked, and the silicon droplets are passed into the molding chamber and cooled into silicon particles and then accumulated in the molding chamber;

[0043] S302, waste gas replacement: the silicon droplet feeding end of the molding chamber 3 is blocked, nitrogen or argon is filled into the molding chamber 3, and waste gases such as hydrogen and hydrogen chloride are replaced by a waste gas replacement device;

[0044] S303, silicon granule feeding: the feeding end 32 of the molding chamber is turned on to achieve the feeding of silicon granules. The silicon granules are cooled to 50°C and then directly packaged. Before packaging, the primary conversion rate of the granular polysilicon product is calculated to be more than 90%, and the yield is more than 90%.

[0045] S31, tail gas treatment: the tail gas generated by the S20 is passed through the gas-solid separation device 4 to realize the collection of silicon powder, and the classified recovery of plasma carrier gas and silicon material reaction gas; wherein, the recovered plasma carrier gas is led to the initial plasma carrier gas input end 15 through the carrier gas recovery pipeline 52, and is used for the carrier gas replenishment of the plasma reaction; the recovered silicon material reaction gas is led to the injection feed end 12 through the reaction gas recovery pipeline 51, and is used as a silicon raw material for plasma reaction.

[0046] 2. Calculation of batch qualification rate of granular polysilicon:

[0047] (1) 15 batches of granular polysilicon products were prepared. For each batch of granular polysilicon: random sampling was performed, and the samples were tested for relevant grade technical indicators such as surface metal impurity content, matrix metal impurity content, donor impurity concentration, and acceptor impurity concentration according to the method of GB / T 25074-2017, thereby determining whether the batch of products was a special grade product. If so, the batch was recorded as qualified;

[0048] (2) The stability of product quality is measured by calculating the batch qualification rate of all the above batches. After calculation, it is found that the batch qualification rate exceeds 95%.

[0049] Example 1-2

[0050] Based on Example 1, the plasma method for producing granular polysilicon comprises the following steps:

[0051] S10, same as in Example 1;

[0052] S20, plasma reaction: hydrogen is used as the initial plasma carrier gas, the reaction temperature is 4980°C, and the pressure is 0.15 MPa. The atomized silicon raw material is injected into the plasma reaction chamber at a rate of 95.60 m³ / min in two stages to generate a plasma reaction, thereby generating silicon droplets and tail gas; wherein, the upper stage injection feeding is a rotary feeding.

[0053] S30 and S31 are the same as those in Example 1.

[0054] The primary conversion rate of polysilicon produced by the above plasma method is 94.67%, the yield is 98.42%, and the batch qualification rate is 98.45%.

[0055] Examples 1-3

[0056] Based on Example 1-2, the plasma method for producing granular polycrystalline silicon only changes the reaction conditions of S20 as follows:

[0057] S20, plasma reaction: hydrogen is used as the initial plasma carrier gas, the reaction temperature is 1500°C, and the pressure is 0.01MPa. The atomized silicon raw material is injected into the plasma reaction chamber at 3.15 m³ / min in two stages to generate plasma reaction, thereby generating silicon droplets and tail gas; wherein, the upper stage injection feeding is rotary feeding.

[0058] The primary conversion rate of polysilicon produced by the above plasma method is 90.21%, the yield is 92.35%, and the batch qualification rate is 97.45%.

[0059] Comparative Example 1-1

[0060] Based on Example 1-2, only the reaction conditions in S20 were changed as follows:

[0061] S20, plasma reaction: hydrogen is used as the initial plasma carrier gas, the reaction temperature is 1495°C, and the pressure is 1.51MPa. The atomized silicon raw material is injected into the plasma reaction chamber at a rate of 75.01 m³ / min in two stages to generate a plasma reaction, thereby generating silicon droplets and tail gas; wherein, the upper stage injection feeding is a rotary feeding.

[0062] The primary conversion rate of polysilicon produced by the above plasma method is 82.35%, the yield is 32.01%, and the batch qualification rate is 88.02%.

[0063] Comparative Example 1-2

[0064] Based on Example 1-2, only the reaction conditions in S20 were changed as follows:

[0065] S20, plasma reaction: hydrogen is used as the initial plasma carrier gas, the reaction temperature is 5050°C, and the pressure is 10.50MPa. The atomized silicon raw material is fed into the plasma reaction chamber at an upper and lower level at a rate of 2.77 m³ / min to cause a plasma reaction, thereby generating silicon droplets and tail gas; wherein, the upper level injection feed is a rotary feed.

[0066] The primary conversion rate of polysilicon produced by the above plasma method is 77.53%, the yield is 89.66%, and the batch qualification rate is 90.02%.

[0067] Comparative Examples 1-3

[0068] Based on Example 1-2, only the reaction conditions in S20 were changed as follows:

[0069] S20, plasma reaction: hydrogen was used as the initial plasma carrier gas, the reaction temperature was 4980℃, and the pressure was 0.15 MPa. The atomized silicon raw material was fed into the plasma reaction chamber at 95.60 m³ / min for upper and lower injection to generate plasma reaction, thereby generating silicon droplets and tail gas. Among them, the upper injection feed was changed to fixed feed, so that the primary conversion rate of polysilicon obtained was 86.21%, the yield was 80.35%, and the batch qualified rate was 92.32%.

Claims

1. A method for producing granular polysilicon by plasma method, characterized in that: The method comprises the following steps: S10, raw material preparation: atomizing the silicon raw material with an atomizer; S20, plasma reaction: the atomized silicon raw material is fed into the plasma reaction chamber by multi-stage injection at 0.1-100 m³ / min, and the plasma reaction is carried out at a temperature of 1500-5000°C, a pressure of 0-10 MPa, and a plasma carrier gas atmosphere, thereby generating silicon droplets and tail gas; S30, molding: the silicon droplets are led to a molding chamber connected to the bottom of the plasma reaction chamber to be cooled into silicon particles; Among the multi-stage injection feeding, at least one stage of injection feeding is rotary feeding.

2. The method for producing granular polysilicon by plasma method according to claim 1, characterized in that: The plasma reaction adopts a passive plasma generator, and the passive plasma adopted by the passive plasma generator is a plasma whose plasma energy and supply mode are not in contact with the plasma.

3. The method for producing granular polysilicon by plasma method according to claim 2, characterized in that: The passive plasma generator may be any one of an inductively coupled plasma reactor, a microwave plasma reactor, a plasma cloud reactor, a dielectric barrier plasma reactor, and a negative pressure plasma reactor.

4. The method for producing granular polysilicon by plasma method according to claim 2, characterized in that: The method for producing granular polysilicon by plasma method also includes: S31, tail gas treatment: the tail gas generated by S20 is subjected to gas-solid separation treatment to realize the collection of silicon powder, and the classified recovery of plasma carrier gas and silicon material reaction gas; wherein the recovered plasma carrier gas is used for carrier gas supplement of plasma reaction; the recovered silicon material reaction gas is used as silicon raw material for plasma reaction.

5. The method for producing granular polysilicon by plasma method according to claim 4, characterized in that: The silicon raw material is one or more of silane, monochlorosilane, dichlorosilane, trichlorosilane, silicon tetrachloride and the like.

6. The method for producing granular polysilicon by plasma method according to claim 4, characterized in that: The plasma carrier gas may be one or more of hydrogen, argon, chlorine, hydrogen chloride, helium, etc.

7. The method for producing granular polysilicon by plasma method according to claim 6, characterized in that: The plasma reaction chamber is provided with upper and lower stages of injection feeding.

8. The method for producing granular polysilicon by plasma method according to claim 7, characterized in that: The upper-stage injection feeding is a rotary feeding, which can be realized by rotatably connecting the nozzle ring to the mounting tube and installing the mounting tube to the plasma reaction chamber; the nozzle adopts a bent tube structure.

9. The method for producing granular polysilicon by plasma method according to claim 8, characterized in that: The plasma generator, the atomizer, the nozzle group and each connecting pipeline are made of high temperature resistant non-metallic material.

10. The method for producing granular polysilicon by plasma method according to claim 4, characterized in that: The yield of the silicon particles is greater than 90%.

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