Granular silicon secondary feeding method for single crystal furnace

Abstract

The invention discloses a secondary charging method of granular silicon for a single crystal furnace, which can effectively inhibit volatilization of silicon powder by adjusting the opening degrees of argon and a throttle valve of the single crystal furnace during charging. By arranging the placing positions of the blocky polycrystalline silicon material and the granular silicon raw material in the feeder, hydrogen in the granular silicon is released in advance by virtue of the fact that the raw material floats on the liquid surface, so that the condition that the granular silicon releases hydrogen when being molten on the molten silicon liquid surface and in the molten silicon and splashes the silicon liquid is avoided. Silicon powder attached to the inner wall of the water cooling screen is completely removed by adjusting the size of the argon channel and an external vibration device, and crystal pulling is prevented from being affected. And the problems of silicon powder volatilization, bubbling and silicon splashing during secondary charging of the existing granular silicon can be effectively solved, and powerful technical support is provided for large-scale popularization of the granular silicon.

Description

Technical Field

[0001] The invention belongs to the field of single crystal silicon production, and in particular relates to a secondary charging method for granular silicon for a single crystal furnace. Background Art

[0002] Granular silicon is a granular polysilicon material. With the continuous maturity of its production technology, the production cost of granular silicon has also been greatly reduced. However, due to many technical problems in the actual use of granular silicon, its large-scale promotion is slow. The existing application of granular silicon is mainly to pour granular silicon into a quartz feeder, and use a secondary feeder as a carrier to lift the granular silicon into the single crystal furnace for feeding. Due to the small particle size and low density of granular silicon, a large amount of silicon powder is attached to its surface. In addition, during transportation and use, the granular silicon squeezes and bumps against each other, and the silicon powder increases. During the actual secondary feeding, the silicon powder will volatilize in the single crystal furnace and adhere to the inner wall surface of the graphite parts and the water-cooled screen, which will have a negative impact on crystal pulling. In addition, when granular silicon is added into the quartz crucible, it will float on the surface of the molten silicon. Due to the special structure of the secondary feeder, the accumulated unmelted granular silicon is in the shape of a crater. The central granular silicon is lower in height and melts first. The granular silicon contains a small amount of hydrogen. After melting, the gas is released, causing the silicon liquid to bubble, forming a "crater phenomenon". The splashed silicon liquid can easily adhere to the external guide and the water-cooling screen, which has a negative impact on crystal pulling. In severe cases, it can scald through the water-cooling screen and cause a safety accident. Summary of the invention

[0003] Purpose of the invention: The technical problem to be solved by the present invention is to provide a method for secondary feeding of granular silicon in view of the shortcomings of the prior art, which effectively solves the defects of silicon powder volatilization and bubbling and splashing silicon, and provides strong technical support for the large-scale promotion of granular silicon.

[0004] In order to achieve the above object, the technical solution adopted by the present invention is as follows: A method for secondary feeding of granular silicon for a single crystal furnace comprises the following steps: (1) Pre-load the block polysilicon material in the lower part of the secondary feeder, and then fill the remaining space with granular silicon powder; (2) Before the second feeding, increase the power of the main heater and turn on the bottom heater at the same time; raise the water cooling screen to the upper limit and lower the quartz crucible to the lower limit; increase the argon flow rate and increase the throttle valve opening of the furnace main pump; (3) Lower the connecting rod of the secondary feeder to separate the conical tray from the special-shaped barrel to form a feeding gap, and add the block polysilicon material at the bottom of the secondary feeder into the quartz crucible first; (4) When the feeding of block polysilicon material is completed and the granular silicon powder begins to be fed, the flow rate of argon gas is increased again, and the secondary feeder is slowly raised to the lower edge of the water cooling screen and stays there until the granular silicon powder is fed; (5) After the silicon powder on the inner wall of the water-cooling screen is blown clean by argon gas, lift and remove the secondary feeder.

[0005] Specifically, in step (1), the linear size of the block polysilicon material is between 30-70 mm, and the particle size of the granular silicon powder is between 0.1-5 mm.

[0006] Furthermore, during the entire process of step (1) of feeding the raw materials into the feeder, the upper opening of the feeder must be completely placed under the dust hood to completely remove the silicon powder volatilized during the descent of the silicon material to the greatest extent possible.

[0007] Specifically, in step (1), the volume proportion of the block polysilicon material in the secondary feeder is 25-33%.

[0008] Specifically, in step (2), 10-20 minutes before the second feeding, the power of the main heater is increased to 100-120 kW, and the power of the bottom heater is turned on and set to 80-100 kW.

[0009] Specifically, in step (2), the argon gas flow rate is increased to 120-150 slpm, and the throttle valve opening of the furnace main pump is increased to 100%.

[0010] Specifically, in step (3), a feeder cover is provided at the upper opening of the secondary feeder. The feeder cover has a trumpet shape with a larger upper opening, and is used to introduce more argon gas from the upper opening of the feeder into the special-shaped barrel.

[0011] Specifically, in step (3), the special-shaped barrel and the conical tray can form a bell-shaped structure when unloading, so as to block the silicon powder volatilized inside the quartz crucible and prevent it from volatilizing upward.

[0012] Specifically, in step (4), the flow rate of argon gas is increased again to 180-200 slpm.

[0013] Specifically, in step (4), the secondary feeder is lifted to the lower edge of the water cooling screen and stays there for 5-10 minutes.

[0014] Specifically, in step (5), the external vibration device of the water inlet and outlet pipes of the water cooling screen is turned on to completely remove the silicon powder on the inner wall of the water cooling screen through vibration. Beneficial Effects

[0015] The present invention can effectively suppress the volatilization of silicon powder by adjusting the argon gas and throttle valve opening of the single crystal furnace during feeding. By setting the placement position of block polysilicon material and granular silicon raw material in the feeder, the hydrogen inside the granular silicon is released in advance by floating the two raw materials on the liquid surface, thereby avoiding the release of hydrogen and splashing of silicon liquid when the granular silicon melts on the molten silicon liquid surface and inside the molten silicon. By adjusting the size of the argon gas channel and the external vibration device, the silicon powder attached to the inner wall of the water cooling screen is completely removed to avoid affecting the crystal pulling. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments, and the above and / or other advantages of the present invention will become more clear.

[0017] Figure 1 It is a component composition diagram of the secondary feeder of the present invention.

[0018] Figure 2 It is a state diagram of the secondary feeder of the present invention after loading.

[0019] Figure 3 It is a schematic diagram of the secondary feeding process of the present invention.

[0020] Wherein, each reference numeral represents: 1-connecting rod; 2-feeder cover; 3-special-shaped barrel; 4-conical tray; 5-granular silicon powder; 6-block polysilicon material. DETAILED DESCRIPTION

[0021] The present invention can be better understood with reference to the following examples.

[0022] Combination Figure 1 As shown, the secondary feeder of the present invention comprises a connecting rod 1, a feeder cover 2, a special-shaped barrel 3 and a conical tray 4. The conical tray 4 is arranged at the bottom of the special-shaped barrel 3, the connecting rod 1 longitudinally penetrates the special-shaped barrel 3, and the bottom is connected to the conical tray 4, and the conical tray 4 is lifted or lowered by the connecting rod 1. When the conical tray 4 is lifted and blocked at the bottom opening of the special-shaped barrel 3, the special-shaped barrel 3 can be filled with granular silicon powder 5 and block polycrystalline silicon material 6. The feeder cover 2 covers the upper opening of the special-shaped barrel 3.

[0023] The specific process of the secondary feeding of granular silicon in the present invention is as follows: S1. Raw material preparation: 30-40kg of block polysilicon material 6 is preferentially loaded into the lower part of the secondary feeder. The linear size of the block polysilicon material 6 needs to be controlled between 30-70mm. Then the upper space of the remaining feeder is completely filled with granular silicon powder 5. The particle size of the granular silicon powder is 0.1-5mm. The volume proportion of block polysilicon material in the secondary feeder is about 25%. Figure 2When the raw materials are poured into the feeder, the upper opening of the feeder should be completely placed under the dust hood to completely remove the silicon powder volatilized during the silicon material descent process.

[0024] S2. 10-20 minutes before the second feeding, increase the main adding power to 100kw, and at the same time start the bottom adding and increase the bottom adding power to 80kw.

[0025] S3. Before adding the second material, it is necessary to confirm that the main bottom adding power has been increased to the target power and the temperature curve has been increased to the target temperature.

[0026] S4. Raise the water cooling screen to the upper limit, lower the crucible position to the lower limit, and adjust the space in the furnace to the maximum to ensure that there is enough space for subsequent material addition.

[0027] S5. When adding materials for the second time, increase the argon flow rate in advance, usually to 120-150slpm (normal value is 80slpm), and adjust the throttle valve opening of the furnace main pump to 100% (normal value is 30-40%) to increase the argon flow rate. Figure 3 shown.

[0028] S6, the silicon powder volatilized during the secondary feeding volatilizes upwards and is suppressed downwards by the rapidly circulating argon gas. Since the feeder cover 2 is provided at the upper opening of the feeder, the component is in the shape of a trumpet and has a larger upper opening, which can guide more argon gas from the upper opening of the feeder into the special-shaped barrel 3, and the silicon powder inside the special-shaped barrel 3 can be fully suppressed. After the secondary feeding raw materials fall into the quartz crucible, some silicon powder will still volatilize upwards. The bell-shaped structure formed by the special-shaped barrel 3 and the conical tray 4 can block the silicon powder volatilized inside the quartz crucible again to prevent it from volatilizing upwards. After the secondary feeding raw materials enter the quartz crucible, most of them float on the surface of the molten silicon liquid. The lower layer is the fast material, and the granular silicon is scattered on the surface of the block material. After being heated, it melts and releases the internal hydrogen in advance, avoiding the occurrence of silicon splashing abnormality caused by the granular silicon directly entering the molten silicon liquid surface to release hydrogen and splash silicon liquid.

[0029] S7. Adjust the argon gas in the furnace to 180-200slpm, lift the feeder to the bottom edge of the water-cooled screen, and stay there for 5 minutes. As the distance between the special-shaped barrel and the water-cooled screen decreases, the argon gas channel shrinks, the argon gas flow rate increases, and the silicon powder on the inner wall of the water-cooled screen is blown away and falls into the quartz crucible.

[0030] S8. After the silicon powder on the inner wall of the water-cooling screen is blown clean, lift the feeder to take it out, turn on the external vibration device on the inlet and outlet water pipes of the water-cooling screen, and completely remove the silicon powder on the inner wall of the water-cooling screen through vibration.

[0031] Through the implementation of the above-mentioned process method, the problem of silicon powder volatilization and bubbling and silicon splashing during the secondary feeding of existing granular silicon can be effectively solved, providing strong technical support for the large-scale promotion of granular silicon.

[0032] The present invention provides a method and idea for a secondary charging method of granular silicon for a single crystal furnace. There are many methods and ways to implement the technical solution. The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the protection scope of the present invention. All components not specified in this embodiment can be implemented by existing technologies.

Claims

1. A method for secondary feeding of granular silicon for a single crystal furnace, characterized in that: The steps include: (1) Pre-load the block polysilicon material in the lower part of the secondary feeder, and then fill the remaining space with granular silicon powder; (2) Before the second feeding, increase the power of the main heater and turn on the bottom heater at the same time; raise the water cooling screen to the upper limit and lower the quartz crucible to the lower limit; increase the argon flow rate and increase the throttle valve opening of the furnace main pump; (3) Lower the connecting rod of the secondary feeder to separate the conical tray from the special-shaped barrel to form a feeding gap, and add the block polysilicon material at the bottom of the secondary feeder into the quartz crucible first; (4) When the feeding of block polysilicon material is completed and the granular silicon powder begins to be fed, the flow rate of argon gas is increased again, and the secondary feeder is slowly raised to the lower edge of the water cooling screen and stays there until the granular silicon powder is fed; (5) After the silicon powder on the inner wall of the water-cooling screen is blown clean by argon gas, lift and remove the secondary feeder.

2. The method for secondary charging of granular silicon for a single crystal furnace according to claim 1, characterized in that: In step (1), the linear size of the block polysilicon material is between 30-70 mm, and the particle size of the granular silicon powder is between 0.1-5 mm.

3. The method for secondary charging of granular silicon for a single crystal furnace according to claim 1, characterized in that: In step (1), the volume of the block polysilicon material in the secondary feeder accounts for 25-33%.

4. The method for secondary charging of granular silicon for a single crystal furnace according to claim 1, characterized in that: In step (2), 10-20 minutes before the second feeding, the power of the main heater is increased to 100-120 kW, and the power of the bottom heater is turned on and set to 80-100 kW.

5. The method for secondary charging of granular silicon for a single crystal furnace according to claim 1, characterized in that: In step (2), the argon flow rate is increased to 120-150 slpm, and the throttle valve opening of the furnace main pump is increased to 100%.

6. The method for secondary charging of granular silicon for a single crystal furnace according to claim 1, characterized in that: In step (3), a feeder cover is provided at the upper opening of the secondary feeder. The feeder cover has a trumpet shape with a larger upper opening, and is used to introduce more argon gas from the upper opening of the feeder into the special-shaped barrel.

7. The method for secondary charging of granular silicon for a single crystal furnace according to claim 1, characterized in that: In step (3), the special-shaped barrel and the conical tray can form a bell-shaped structure when unloading, so as to block the silicon powder volatilized in the quartz crucible and prevent it from volatilizing upward.

8. The method for secondary charging of granular silicon for a single crystal furnace according to claim 1, characterized in that: In step (4), the flow rate of argon is increased again to 180-200 slpm.

9. The method for secondary charging of granular silicon for a single crystal furnace according to claim 1, characterized in that: In step (4), the secondary feeder is lifted to the lower edge of the water cooling screen and stays there for 5-10 minutes.

10. The method for secondary charging of granular silicon for a single crystal furnace according to claim 1, characterized in that: In step (5), the external vibration device of the water inlet and outlet pipes of the water cooling screen is turned on to completely remove the silicon powder on the inner wall of the water cooling screen through vibration.

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