Preparation method of phosphorus-doped granular silicon and preparation method of monocrystalline silicon

Abstract

The invention provides a preparation method of phosphorus-doped granular silicon and a preparation method of monocrystalline silicon. The preparation method of the phosphorus-doped granular silicon comprises the following steps: providing a fluidized bed reactor; loading a seed crystal into the fluidized bed reactor; introducing phosphine gas, hydrogen and silane gas into the fluidized bed reactor; the temperature and the pressure of the vapor deposition reaction in the fluidized bed reactor are controlled through the control unit; discharging a reaction product in the fluidized bed reactor out of the fluidized bed reactor through a particle discharging device, and separating phosphorus-doped particle silicon from the reaction product; the tail gas is discharged out of the fluidized bed reactor through the gas discharging device. The preparation method of the phosphorus-doped granular silicon and the preparation method of the monocrystalline silicon are simple in process and relatively low in cost, and the prepared silicon wafer is relatively high in purity.

Description

Technical Field

[0001] The present invention relates to the technical field of silicon wafer production, and in particular to a method for preparing phosphorus-doped granular silicon and a method for preparing single crystal silicon. Background Art

[0002] The Czochralski method for growing single crystal silicon is currently the most widely used technology for producing single crystal silicon. In the process of Czochralski single crystal, N-type silicon wafers are produced by using trace amounts of phosphorus as a dopant. However, the sublimation temperature of phosphorus is below 600°C and the melting point of silicon is 1420°C. Therefore, phosphorus cannot be added before the solid silicon is in a molten state.

[0003] Currently, the main method is to use the continuous direct crystal pulling (CCZ) method, adding granular silicon for crystal pulling while adding phosphorus to ensure that the silicon crystal has a sufficient phosphorus concentration. The high-concentration phosphorus silicon rods pulled by the CCZ method are then manually crushed. This process will introduce a large amount of impurities, seriously polluting the crystal concentration.

[0004] The granular silicon is turned into high-concentration phosphorus silicon rods, which are then cut and processed into silicon wafers. The silicon wafers are crushed to form granular silicon-like phosphorus-containing particles, which are also called master alloys. The master alloy is used to adjust the resistivity of the crystal during the crystal pulling process to match the diffusion process of the battery manufacturer. This method is more complicated and costly, and a large amount of impurities will be introduced into the master alloy, resulting in poor quality of single crystal silicon.

[0005] In view of this, it is necessary to improve the existing preparation methods of phosphorus-doped granular silicon and single crystal silicon to solve the above problems. Summary of the invention

[0006] The object of the present invention is to provide a method for preparing phosphorus-doped granular silicon and a method for preparing single crystal silicon, which have simple process, low cost and high purity of the prepared silicon wafers.

[0007] To achieve the above-mentioned object of the invention, the present invention provides a method for preparing phosphorus-doped granular silicon, comprising the following steps:

[0008] Providing a fluidized bed reactor;

[0009] loading seed crystals into the fluidized bed reactor;

[0010] Passing phosphine gas, hydrogen gas and silane gas into the fluidized bed reactor;

[0011] The temperature and pressure of the vapor deposition reaction in the fluidized bed reactor are controlled by a control unit;

[0012] The reaction product in the fluidized bed reactor is discharged from the fluidized bed reactor through a particle discharge device, and phosphorus-doped granular silicon is separated from the reaction product;

[0013] The tail gas is discharged from the fluidized bed reactor through a gas discharge device.

[0014] As a further improvement of the present invention, the method for preparing phosphorus-doped granular silicon also includes screening out the seeds that meet preset conditions before performing the step of "loading the seeds into the fluidized bed reactor", and the preset conditions include preset particle size, preset sphericity and preset purity.

[0015] As a further improvement of the present invention, the control unit controls the temperature of the vapor deposition reaction in the fluidized bed reactor to be within a range of 600 to 800°C.

[0016] As a further improvement of the present invention, the control unit controls the pressure of the vapor deposition reaction in the fluidized bed reactor within a range of 0.5 to 1 MPa.

[0017] As a further improvement of the present invention, the method for preparing phosphorus-doped granular silicon further includes preparing phosphine gas before the step of "introducing phosphine gas, hydrogen gas and silane gas into the fluidized bed reactor".

[0018] As a further improvement of the present invention, the step of "preparing phosphine gas" specifically includes: introducing white phosphorus and hydrogen into a phosphine reactor for chemical reaction, and controlling the reaction temperature to be 240 to 500° C. and the reaction pressure to be 2 to 5 MPa.

[0019] As a further improvement of the present invention, the step of "preparing phosphine gas" further includes subjecting the reaction product of the white phosphorus and hydrogen to a double cooling and separation treatment to obtain the phosphine gas.

[0020] As a further improvement of the present invention, the step of "introducing phosphine gas, hydrogen gas and silane gas into the fluidized bed reactor" specifically includes controlling the flow rate and flow rate of the introduced gas through a circulating gas compression unit.

[0021] As a further improvement of the present invention, the method for preparing phosphorus-doped granular silicon also includes selecting a predetermined amount of phosphorus-doped granular silicon for heating, melting and crystallization, and performing a resistivity test on the crystallized silicon ingot to confirm whether the obtained phosphorus-doped granular silicon meets preset requirements.

[0022] To achieve the above-mentioned object of the invention, the present invention also provides a method for preparing single crystal silicon, which comprises:

[0023] Adding phosphorus-doped granular silicon prepared by the above-mentioned preparation method of phosphorus-doped granular silicon into a crucible;

[0024] Melting the phosphorus-doped granular silicon at high temperature to obtain molten silicon liquid;

[0025] A seed crystal with a single crystal structure is inserted into the silicon liquid to seed the crystal to obtain single crystal silicon.

[0026] Beneficial effects of the present invention: The method for preparing phosphorus-doped granular silicon of the present invention comprises the following steps: introducing phosphine gas, silane gas and hydrogen into the fluidized bed reactor and carrying out a vapor deposition reaction therein, controlling the temperature and pressure of the vapor deposition reaction in the fluidized bed reactor by a control unit, discharging the reaction products in the fluidized bed reactor by a particle discharge device, and separating the phosphorus-doped granular silicon from the reaction products, thereby eliminating the process of making high-concentration phosphorus silicon rods and crushing them, and directly obtaining the required phosphorus-doped granular silicon. In the process of preparing single crystal silicon, there is no need to add a master alloy to adjust the resistivity of the crystal, and the resistivity of the single crystal silicon can also be effectively adjusted to match the diffusion process of the battery manufacturer. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a schematic diagram of the system structure of the method for preparing phosphorus-doped granular silicon of the present invention.

[0028] Figure 2 yes Figure 1 A flowchart of further processing of separated doped granular silicon in the method for preparing phosphorus-doped granular silicon is shown.

[0029] Figure 3 It is a schematic flow chart of the method for preparing single crystal silicon of the present invention. DETAILED DESCRIPTION

[0030] The present invention will be described in detail below in conjunction with the embodiments shown in the accompanying drawings. However, the embodiments do not limit the present invention, and any structural, methodological, or functional changes made by a person skilled in the art based on the embodiments are all within the protection scope of the present invention.

[0031] The terms used herein, such as "upper", "lower", "left", "right", "front", "back", etc., which indicate relative positions in space, are used for the purpose of convenience to describe the relationship between one feature and another feature as shown in the drawings. It is understood that, depending on the placement of the product, the terms of relative positions in space may be intended to include different orientations in addition to the orientation shown in the drawings, and should not be construed as limitations on the claims. In addition, the descriptor "horizontal" used herein is not completely equivalent to being perpendicular to the direction of gravity, and a certain angle of inclination is allowed.

[0032] Please refer to Figures 1 to 3 The figure shows a schematic diagram of a method for preparing phosphorus-doped granular silicon and a method for preparing single crystal silicon according to the present invention; wherein Figure 1 It is a schematic diagram of the system structure of the method for preparing phosphorus-doped granular silicon of the present invention; Figure 2 yes Figure 1A flowchart of further processing of separated doped silicon granules in the method for preparing phosphorus-doped silicon granules shown; Figure 3 It is a schematic flow chart of the method for preparing single crystal silicon of the present invention.

[0033] For details, please refer to Figure 1 and Figure 2 As shown, the method for preparing phosphorus-doped granular silicon of the present invention comprises the following steps:

[0034] Providing a fluidized bed reactor;

[0035] loading seed crystals into the fluidized bed reactor;

[0036] Passing phosphine gas, hydrogen gas and silane gas into the fluidized bed reactor;

[0037] The temperature and pressure of the vapor deposition reaction in the fluidized bed reactor are controlled by a control unit;

[0038] The reaction product in the fluidized bed reactor is discharged from the fluidized bed reactor through a particle discharge device, and phosphorus-doped granular silicon is separated from the reaction product;

[0039] The tail gas is discharged from the fluidized bed reactor through a gas discharge device.

[0040] In the present invention, the method for preparing phosphorus-doped granular silicon is as follows: phosphine gas, silane gas and hydrogen are introduced into the fluidized bed reactor and a vapor deposition reaction is carried out therein, the temperature and pressure of the vapor deposition reaction in the fluidized bed reactor are controlled by a control unit, the reaction products in the fluidized bed reactor are discharged from the fluidized bed reactor by a particle discharge device, and the phosphorus-doped granular silicon is separated from the reaction products, thereby eliminating the process of making high-concentration phosphorus silicon rods and crushing them, and directly obtaining the required phosphorus-doped granular silicon. In the process of preparing single crystal silicon, there is no need to add master alloy to adjust the resistivity of the crystal. At the same time, the resistivity of the single crystal silicon can also be effectively adjusted to match the diffusion process of the battery manufacturer. Therefore, the production process can be effectively simplified, the production cost can be reduced, and the quality and production capacity can be improved.

[0041] In some embodiments of the present invention, the method for preparing phosphorus-doped granular silicon also includes screening out the seeds that meet preset conditions before performing the step of "loading the seeds into the fluidized bed reactor", wherein the preset conditions include preset particle size, preset sphericity and preset purity.

[0042] In the present invention, by screening out crystal seeds that meet the preset conditions, the particle size, sphericity and purity of the crystal seeds are guaranteed, so that the concentration of phosphorus doped in the granular silicon can be better guaranteed. When the molten silicon liquid is subsequently prepared in the crucible, the uniformity of the phosphorus element in the phosphorus-doped granular silicon and the resistivity of the single crystal silicon can be guaranteed to meet the requirements.

[0043] Specifically, in one embodiment of the present invention, the preset particle size range of the seed crystal is 300-1000 μm, the preset sphericity is 0.7-0.95, and the preset purity includes total metal content ≤1ppbw, carbon content ≤0.3ppma, phosphorus content ≤0.3ppba, and boron content ≤0.1ppba.

[0044] In this way, by controlling the particle size, sphericity and purity of the seed crystal within a specific range, the uniformity of the seed crystal particles can be improved, the growth rate can be fast, the yield can be high, and the purity can be high, thus avoiding the resistivity of the subsequently prepared single crystal silicon not meeting the requirements due to the uneven phosphorus content in the phosphorus-doped granular silicon.

[0045] In the above-mentioned embodiments of the present invention, the size, sphericity, purity, and phosphorus-doped concentration of the seed crystals can be well controlled to ensure the uniformity of the phosphorus-doped silicon granules obtained by chemical vapor deposition of the seed crystals in a fluidized bed reactor, while making the volume of the obtained phosphorus-doped silicon granules smaller.

[0046] In the preparation process of phosphorus-doped granular silicon of the present invention, silane gas, hydrogen gas and phosphine gas are introduced from the bottom of the fluidized bed reactor at a certain speed, and screened high-purity seed crystals are added from the upper part of the fluidized bed reactor and guided to the fluidized state. Under the action of the external heater of the fluidized bed reactor, the silane gas, hydrogen gas and phosphine gas undergo chemical vapor deposition reaction on the surface of the high-purity silicon particles, so that the high-purity seed crystals gradually grow, and large-sized granular products with a certain phosphorus concentration are discharged from the bottom of the fluidized bed reactor. Silicon seed crystals are continuously replenished from the upper part of the fluidized bed reactor, thereby realizing continuous production and greatly reducing energy consumption and costs.

[0047] In one embodiment of the present invention, the control unit controls the temperature of the vapor deposition reaction in the fluidized bed reactor within a range of 600 to 800° C. In this way, the fluidized state in the fluidized bed reactor is ensured, the reaction effect of the chemical vapor deposition reaction in the fluidized bed reactor is improved, the volatilization of carbon in the graphite material is reduced, and the uniformity and efficiency of the chemical vapor deposition reaction are ensured.

[0048] The control unit controls the pressure of the vapor deposition reaction in the fluidized bed reactor within the range of 0.5 to 1 MPa. Thus, by controlling the pressure of the chemical vapor deposition reaction in the fluidized bed reactor within the range of 0.5 to 1 MPa, the reaction time in the fluidized bed reactor is sufficient, thereby ensuring that the phosphine gas, silane gas and hydrogen introduced in the fluidized bed reactor can fully undergo vapor deposition reaction with the seed crystals, and at the same time ensuring the output of phosphorus-doped granular silicon.

[0049] Furthermore, in one embodiment of the present invention, the method for preparing phosphorus-doped granular silicon also includes preparing phosphine gas before the step of "introducing phosphine gas, hydrogen and silane gas into the fluidized bed reactor", so that the seed crystals can be effectively doped with phosphorus element in the fluidized bed reactor, thereby simplifying the production process and reducing the production cost of single crystal silicon.

[0050] Furthermore, in one embodiment of the present invention, the step of "preparing phosphine gas" specifically includes: introducing white phosphorus and hydrogen into a phosphine reactor for a chemical reaction, and controlling the reaction temperature to be 240 to 500° C. and the reaction pressure to be 2 to 5 MPa.

[0051] The present invention uses white phosphorus and hydrogen to generate phosphine gas in the following chemical reaction:

[0052] 3P4+6H2=4PH3

[0053] In the present invention, the flow rate is controlled by controlling the reaction pressure to ensure that white phosphorus and hydrogen can fully react to produce phosphine.

[0054] In addition, in one embodiment of the present invention, the step of "preparing phosphine gas" also includes subjecting the reaction product after the chemical reaction of the white phosphorus and hydrogen to two cooling and separation treatments to obtain the phosphine gas, thereby effectively removing impurities through the two cooling and separations, improving the yield and purity of phosphine, and ensuring the stability of the subsequent vapor deposition reaction and the uniformity of phosphorus doping.

[0055] In one embodiment of the present invention, the step of "introducing phosphine gas, hydrogen gas and silane gas into the fluidized bed reactor" specifically includes controlling the flow rate and flow rate of the introduced gas by a circulating gas compression unit.

[0056] The flow rate of the phosphine gas is controlled at 150-250 liters per minute, so as to effectively control the concentration of phosphorus-doped silicon and thereby ensure the uniformity and generation efficiency of phosphorus-doped silicon particles.

[0057] In one embodiment of the present invention, the step of "discharging the reaction products in the fluidized bed reactor from the fluidized bed reactor through a particle discharge device, and separating the phosphorus-doped granular silicon from the reaction products" specifically includes cooling the reaction products discharged from the fluidized bed reactor through a filtering and cooling unit, and separating the phosphorus-doped granular silicon, unreacted gas and impurities from the reaction products. Specifically, the phosphorus-doped granular silicon can be separated from the reaction products by filtration or centrifugation.

[0058] The method for preparing doped granular silicon also includes recovering and treating the tail gas after the step of "discharging the tail gas from the fluidized bed reactor through the gas exhaust device", thereby realizing the recovery and recycling of the tail gas and saving energy.

[0059] In the present invention, the step of "discharging the reaction product in the fluidized bed reactor from the fluidized bed reactor through a particle discharge device, and separating phosphorus-doped granular silicon from the reaction product" and the step of "discharging the exhaust gas from the fluidized bed reactor through a gas discharge device" are carried out simultaneously, and the exhaust gas is discharged, recovered and treated while preparing and obtaining phosphorus-doped granular silicon, so as to improve resource utilization and reduce environmental pollution.

[0060] Please refer to Figure 2 As shown, in one embodiment of the present invention, the method for preparing phosphorus-doped granular silicon also includes, after the step of "discharging the reaction products in the fluidized bed reactor from the fluidized bed reactor through the particle discharge device, and separating the phosphorus-doped granular silicon from the reaction products", selecting a predetermined amount of phosphorus-doped granular silicon for heating, melting and crystallization, and performing a resistivity test on the silicon ingot formed by the crystallization to confirm whether the obtained phosphorus-doped granular silicon meets the preset requirements.

[0061] Furthermore, the resistivity of the phosphorus-doped granular silicon is marked according to the resistivity test result for subsequent use.

[0062] In addition, please refer to Figure 3 As shown, in the present invention, a method for preparing single crystal silicon is also provided, which comprises the following steps:

[0063] Adding phosphorus-doped granular silicon prepared by the above-mentioned method for preparing phosphorus-doped granular silicon into a crucible;

[0064] Melting the phosphorus-doped granular silicon at high temperature to obtain molten silicon liquid;

[0065] A seed crystal with a single crystal structure is inserted into the silicon liquid to seed the crystal to obtain single crystal silicon.

[0066] In the present invention, the phosphorus-doped granular silicon prepared by the above-mentioned method for preparing phosphorus-doped granular silicon has phosphorus element uniformly doped into the granular silicon, so that phosphorus-doped granular silicon with relatively high uniformity is obtained. Therefore, when preparing single crystal silicon, there is no need to input additional master alloy, the preparation process is relatively simple, and the uniformity of phosphorus doping in the obtained molten silicon liquid is better, so that the resistivity distribution of single crystal silicon prepared by this preparation method is more uniform.

[0067] In summary, the method for preparing phosphorus-doped granular silicon and the method for preparing single crystal silicon in the present invention are as follows: phosphine gas, silane gas and hydrogen are introduced into the fluidized bed reactor and a vapor deposition reaction is carried out therein, the temperature and pressure of the vapor deposition reaction in the fluidized bed reactor are controlled by a control unit, the reaction product in the fluidized bed reactor is discharged from the fluidized bed reactor by a particle discharge device, and the phosphorus-doped granular silicon is separated from the reaction product, thereby eliminating the process of making high-concentration phosphorus silicon rods and crushing them, and directly obtaining the required phosphorus-doped granular silicon. In the process of preparing single crystal silicon, it is no longer necessary to add a master alloy to adjust the resistivity of the crystal. The preparation process is relatively simple, and the uniformity of the doped elements in the obtained molten silicon liquid is better, so that the resistivity distribution of the single crystal silicon is more uniform, so as to match the diffusion process of the battery manufacturer.

[0068] It should be understood that although this specification is described according to implementation modes, not every implementation mode contains only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each implementation mode may also be appropriately combined to form other implementation modes that can be understood by those skilled in the art.

[0069] The series of detailed descriptions listed above are only specific descriptions of feasible implementation methods of the present invention. They are not intended to limit the scope of protection of the present invention. Any equivalent implementation methods or changes that do not deviate from the technical spirit of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for preparing phosphorus-doped granular silicon, characterized in that: The following steps are involved: Providing a fluidized bed reactor; loading seed crystals into the fluidized bed reactor; Passing phosphine gas, hydrogen gas and silane gas into the fluidized bed reactor; The temperature and pressure of the vapor deposition reaction in the fluidized bed reactor are controlled by a control unit; The reaction product in the fluidized bed reactor is discharged from the fluidized bed reactor through a particle discharge device, and phosphorus-doped granular silicon is separated from the reaction product; The tail gas is discharged from the fluidized bed reactor through a gas discharge device.

2. The method for preparing phosphorus-doped granular silicon according to claim 1, characterized in that: The method for preparing phosphorus-doped granular silicon also includes screening out the seeds that meet preset conditions before performing the step of "loading the seeds into the fluidized bed reactor", wherein the preset conditions include a preset particle size, a preset sphericity, and a preset purity.

3. The method for preparing phosphorus-doped granular silicon according to claim 1, characterized in that: The control unit controls the temperature of the vapor deposition reaction in the fluidized bed reactor to be within the range of 600 to 800°C.

4. The method for preparing phosphorus-doped granular silicon according to claim 1, characterized in that: The control unit controls the pressure of the vapor deposition reaction in the fluidized bed reactor within a range of 0.5 to 1 MPa.

5. The method for preparing phosphorus-doped granular silicon according to any one of claims 1 to 4, characterized in that: The method for preparing phosphorus-doped granular silicon further includes preparing phosphine gas before the step of "introducing phosphine gas, hydrogen gas and silane gas into the fluidized bed reactor".

6. The method for preparing phosphorus-doped granular silicon according to claim 5, characterized in that: The step of "preparing phosphine gas" specifically includes: introducing white phosphorus and hydrogen into a phosphine reactor for chemical reaction, and controlling the reaction temperature to be 240 to 500° C. and the reaction pressure to be 2 to 5 MPa.

7. The method for preparing phosphorus-doped granular silicon according to claim 6, characterized in that: The step of "preparing phosphine gas" also includes cooling and separating the reaction product after the white phosphorus and hydrogen react with each other twice to obtain the phosphine gas.

8. The method for preparing phosphorus-doped granular silicon according to any one of claims 1 to 4, characterized in that: The step of "introducing phosphine gas, hydrogen gas and silane gas into the fluidized bed reactor" specifically includes controlling the flow rate and flow rate of the introduced gas through a circulating gas compression unit.

9. The method for preparing phosphorus-doped granular silicon according to any one of claims 1 to 4, characterized in that: The method for preparing phosphorus-doped granular silicon also includes selecting a predetermined amount of phosphorus-doped granular silicon for heating, melting and crystallization, and performing a resistivity test on the crystallized silicon ingot to confirm whether the prepared phosphorus-doped granular silicon meets preset requirements.

10. A method for preparing single crystal silicon, characterized in that: include: Adding the phosphorus-doped granular silicon prepared by the preparation method according to any one of claims 1 to 9 into a crucible; Melting the phosphorus-doped granular silicon at high temperature to obtain molten silicon liquid; A seed crystal with a single crystal structure is inserted into the silicon liquid to carry out seeding to obtain single crystal silicon.

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