CN102126726A - A method and equipment for efficiently purifying polysilicon powder by electron beam - Google Patents

Abstract

The invention belongs to the technical field of purifying polycrystalline silicon by using a physical metallurgy technology. A method for efficiently purifying polysilicon powder by electron beams comprises the following steps: putting a high-purity silicon material with low phosphorus and low metal into a melting crucible with a cooling bottom, and adding high-phosphorus and high-metal silicon powder to be purified into a powder charging barrel; the second step of pretreatment: vacuumizing the vacuum chamber; cooling the smelting crucible and the ingot pulling mechanism to 25-45 ℃; preheating the electron gun; and a third step of purification: opening an electron gun for smelting, and removing volatile impurity phosphorus; the smelted low-phosphorus silicon liquid is solidified in a directional solidification mode, and metal impurities are gathered on the upper part of a silicon ingot; and closing the electron gun, continuing vacuumizing for 15-30 minutes, opening the air release valve to release air, opening the vacuum cover, taking out the silicon ingot and cutting off the part containing more metal impurities on the upper part of the silicon ingot. The invention simultaneously realizes the double effects of phosphorus removal and directional solidification metal removal of the electron beam melting silicon powder, and achieves the purposes of efficiently melting the silicon powder and quickly removing impurities.

Description

A method and equipment for efficiently purifying polysilicon powder by electron beam

technical field

The invention belongs to the technical field of purifying polysilicon by physical metallurgy technology, in particular relates to a method for removing phosphorus and metal impurities in polysilicon, and also relates to its equipment.

Background technique

In a society where energy is scarce and low-carbon environmental protection is advocated, solar energy, as an environmentally friendly new energy, has great application value. Solar cells can convert solar energy into electrical energy, and solar-grade polycrystalline silicon materials are important raw materials for solar cells. Therefore, the preparation technology of solar grade polysilicon material is particularly important. At present, the main technical routes for preparing solar-grade polysilicon materials worldwide include: improved Siemens method, silane method, and metallurgical method. The principle of the improved Siemens method is to use high-purity hydrogen to reduce high-purity trichlorosilane on a high-purity silicon core at a temperature of about 1100 ° C, and generate polysilicon to deposit on the silicon core. However, the improved Siemens method has high energy consumption and serious pollution, and is an old technology that has been eliminated in Europe and the United States. The silane method is a method of thermally decomposing silane (SiH ₄ ) to prepare polysilicon, but this process is dangerous during production and operation (silane is flammable and explosive), and the overall production cost is relatively high. Metallurgical methods mainly include: electron beam smelting method, plasma beam smelting method, directional solidification method, slagging method, electrolysis method, carbothermal reduction method, etc. Compared with the improved Siemens method, the metallurgical method has the advantages of low energy consumption and less pollution.

Metallurgy has become a hotspot of research and development by countries all over the world. Some use electron beam smelting to remove impurities such as phosphorus and aluminum with high saturated vapor pressure through surface evaporation, and some use directional solidification to remove impurity metals by using segregation coefficient. Known patents and literatures do not yet have a purification method for removing phosphorus in polysilicon by electron beam smelting powdered silicon material and removing impurity metals by directional solidification. The known invention patent with the application number of 200810011631.8 uses induction heating and electron beams to achieve the purpose of removing phosphorus and metal impurities in polycrystalline silicon, but the disadvantage of this method is that bulk silicon material is smelted and purified, and the distribution of impurities is similar to that of powdered silicon material. relatively uneven.

Contents of the invention

The purpose of the present invention is to overcome the above-mentioned disadvantages, provide a method for efficiently purifying polysilicon powder with electron beams, combine the use of electron beams to smelt powdered silicon material and directional solidification technology, and remove impurities phosphorus and metal impurities at the same time to achieve solar-grade polysilicon materials usage requirements. Another object of the present invention is to provide a device for efficiently purifying polysilicon powder with electron beams, which has a simple structure, is easy to operate, and has high purification precision.

The technical solution adopted by the present invention for achieving the above purpose is: a method for efficiently purifying polysilicon powder by electron beams, the carrier high-purity silicon material forms a high-purity silicon molten pool under electron beam heating, and then continuously adds silicon powder to be purified, The silicon powder is smelted by electron beam, and the impurity phosphorus in the silicon powder is quickly removed. The low-phosphorus silicon liquid overflows into the ingot pulling mechanism to pull the ingot to achieve the directional solidification effect. The steps are as follows:

The first step of material preparation: put the high-purity silicon material with low phosphorus and low metal into the melting crucible with cooling at the bottom, add the high phosphorus and high metal silicon powder to be purified into the powder loading barrel, close the powder loading cover, and turn off the vacuum build;

The second step of pretreatment: evacuate the vacuum chamber, and use vacuum equipment to evacuate the vacuum chamber to a high vacuum below 0.001Pa; cool the melting crucible with cooling at the bottom and the ingot pulling mechanism, and maintain the temperature at 25-45°C; Preheat the electron gun, set the high voltage to 28-30kw, after high-voltage preheating for 5-10 minutes, turn off the high voltage, set the electron gun beam current to 100-200mA, and perform preheating, after preheating for 10-15 minutes, turn off the electron gun beam;

The third step of purification: turn on the high voltage and beam of the electron gun, and after stabilization, use the electron gun to bombard the low-phosphorus, low-metal high-purity silicon material in the melting crucible with cooling at the bottom with a 200-300mA beam to make the low-phosphorus, low-metal high-purity silicon The material is melted to form a low-phosphorus molten pool; after the formation of a low-phosphorus molten pool, increase the beam flow of the electron gun to 300-500mA, open the bottom outlet of the powder loading barrel, and the high-phosphorus and high-metal silicon powder will fall into the smelting crucible with cooling at the bottom , for smelting to remove volatile impurity phosphorus; after smelting for a period of time, the low-phosphorus silicon liquid in the melting crucible with cooling at the bottom overflows and flows into the quartz crucible of the ingot pulling mechanism. Minutes, the ingot is pulled down by the water-cooled ingot rod, and the low-phosphorus silicon liquid solidifies in a directional solidification manner, and metal impurities gather on the upper part of the silicon ingot; Gas, open the vacuum cover, take out the silicon ingot and cut off the upper part of the silicon ingot that contains more metal impurities.

An equipment for efficiently purifying polysilicon powder with electron beams. The vacuum equipment consists of a vacuum cover, a furnace wall and a powder loading cover. The inner cavity of the vacuum equipment is a vacuum chamber; Powder loading cover, the powder loading cover is located on the wall of the vacuum furnace, the bottom of the powder loading barrel has a discharge port, the discharge port is equipped with an external drive powder baffle, the bottom of the powder loading barrel discharge port is equipped with a melting crucible, and the bottom of the melting crucible is The supporting rod is fixed on the bottom of the vacuum chamber, the ingot pulling mechanism is placed under the outlet of the melting crucible, the electron gun is installed on the upper part of the vacuum chamber, and the electron beam is aimed at the silicon block.

The vacuum equipment is equipped with a vacuum device, and the vacuum device adopts a diffusion pump, a Roots pump and a mechanical pump installed on the side of the furnace wall, and an air release valve is also provided on the furnace wall.

The ingot pulling mechanism adopts a water-cooled ingot rod installed on the bottom of the vacuum furnace wall. A copper plate is installed on the upper part of the water-cooled ingot rod. A graphite base is installed on the copper plate. A quartz crucible is placed on the graphite base. A cooling device is installed in the water-cooled ingot rod and the copper plate. Runner, the cooling runner is connected to the cooling source.

A support base is installed on the periphery of the water-cooled spindle rod, a graphite heating element is installed on the support base, and a thermal insulation sheath is installed on the periphery of the graphite heating element.

The externally driven powder baffle is an L-shaped powder baffle, one end of the powder baffle is rotatably installed in a rotating mechanism, and the rotating mechanism is installed outside the vacuum furnace wall.

The remarkable effect of the present invention is to use the method of electron beam smelting polysilicon powder and directional solidification at the same time, remove impurity phosphorus in polysilicon by electron beam smelting technology, and then remove impurity metals in polysilicon with small segregation coefficient by directional solidification technology, and improve The purity of the polysilicon material makes it meet the requirements for the use of solar-grade polysilicon materials. This process has a good effect of removing phosphorus and impurity metals, and the method is simple. Melting polysilicon according to high-energy-density electron beams can remove volatile impurities with high saturated vapor pressure. The principle is to use electron beams to bombard high-purity silicon blocks to form a stable molten pool. After adding powdered silicon materials, it can quickly melt and remove impurity phosphorus. The dual effect of smelting silicon powder to remove phosphorus and directional solidification to remove metal achieves the purpose of efficiently smelting silicon powder and quickly removing impurities.

The invention has the advantages of simple equipment, stable technology, less energy consumption, and low cost. The whole equipment simultaneously uses electron beam smelting silicon powder and directional solidification technology, thereby achieving dual effects of phosphorus removal and metal removal, and is suitable for mass production of silicon materials.

Description of drawings

The accompanying drawing is a schematic structural diagram of equipment used in a method for efficiently purifying polysilicon powder by electron beam smelting. In the figure, 1. Powder filling cover, 2. Electron gun, 3. Vacuum chamber, 4. Furnace wall, 5. Vacuum cover, 6. Low phosphorus silicon liquid, 7. Quartz crucible, 8. Graphite heating element, 9. Thermal protection Set, 10. Low phosphorus silicon liquid, 11. Support base, 12. Graphite base, 13. Water-cooled copper plate, 14. Water-cooled ingot rod, 15. Support rod, 16. Air release valve, 17. Water-cooled copper crucible, 18 . Mechanical pump, 19. Roots pump, 20. Diffusion pump, 21. Low phosphorus molten pool, 22. Powder baffle, 23. Rotating mechanism, 24. High phosphorus silicon powder, 25. Powder loading barrel.

Detailed ways

The present invention will be described in detail below in conjunction with specific embodiments and drawings, but the present invention is not limited to specific embodiments.

Example 1

A method for efficiently purifying polysilicon powder with electron beams. The carrier high-purity silicon material forms a high-purity silicon molten pool under electron beam heating, and then continuously adds silicon powder to be purified, and electron beams melt the silicon powder to quickly remove impurities in the silicon powder. Phosphorus, low-phosphorus silicon liquid overflows into the ingot pulling mechanism to pull the ingot to achieve the directional solidification effect. The steps are as follows:

The first step of material preparation: put the high-purity silicon material with low phosphorus and low metal into the smelting crucible with cooling at the bottom, open the powder loading cover 1 and add the high phosphorus and high metal silicon powder 24 to be purified into the powder loading bucket 25, Close the powder loading cover 1, close the vacuum cover 5;

The second step of pretreatment: vacuumize the vacuum chamber 3, and use vacuum equipment to evacuate the vacuum chamber 3 to a high vacuum of 0.001Pa or less; cool the melting crucible 17 with cooling at the bottom and the ingot pulling mechanism, and maintain the temperature at 25- 45°C; Preheat the electron gun 2, set the high voltage to 28-30kw, after 5-10 minutes of high-pressure preheating, turn off the high voltage, set the beam current of the electron gun 2 to 100-200mA, preheat, and turn off after 10-15 minutes of preheating Electron gun 2 beams;

The third step of purification: open the high voltage and beam current of the electron gun 2, and after stabilization, use the electron gun 2 to bombard the low-phosphorus, low-metal high-purity silicon material in the smelting crucible 17 with cooling at the bottom with a 200-300mA beam current to make the low-phosphorus, low-metal high-purity silicon material The high-purity silicon material is melted to form a low-phosphorus molten pool 21; after the low-phosphorous molten pool 21 is formed, the beam flow of the electron gun 2 is increased to 300-500mA, and the bottom outlet of the powder loading energy is opened, and the high-phosphorus and high-metal silicon powder 24 falls into the In the smelting crucible 17 with cooling at the bottom, smelting is carried out to remove volatile impurity phosphorus; after smelting for a period of time, the low-phosphorus silicon liquid in the smelting crucible 17 with cooling at the bottom overflows, flows into the quartz crucible 7 of the ingot pulling mechanism, and is heated and kept warm Maintain the liquid state, wait for 1-2 minutes after the powder falling, pull the ingot down through the water-cooled ingot rod 14, the low-phosphorus silicon liquid 10 solidifies in a directional solidification manner, and the metal impurities gather on the upper part of the silicon ingot; after the directional solidification is completed, turn off the electron gun 2, Continue vacuuming for 15-30 minutes, open the air release valve 16 to deflate, open the vacuum cover 5, take out the silicon ingot and cut off the part containing more metal impurities on the upper part of the silicon ingot.

Example 2

As shown in Fig. 1, a kind of equipment for efficiently purifying polysilicon powder by electron beam, in the equipment, vacuum equipment is composed of vacuum cover 5, furnace wall 4 and powder loading cover 1, and the inner cavity of vacuum equipment is vacuum chamber 3; the upper part of the vacuum chamber is equipped with The powder loading barrel has a powder loading cover on the top of the powder loading bucket, and the powder loading cover is located on the wall of the vacuum furnace. The bottom of the powder loading bucket has a discharge port. The powder plate 22 is an L-shaped powder baffle, and one end of the powder baffle is rotated and installed in the rotating mechanism 23, and the rotating mechanism 23 is installed outside the vacuum furnace wall. A melting crucible is installed at the bottom of the outlet of the powder loading barrel, and the melting crucible is a water-cooled copper crucible. 17. The bottom of the melting crucible is fixed on the bottom of the vacuum chamber through the support rod 15, and the ingot pulling mechanism is placed under the discharge port of the melting crucible. There is a copper plate 13, a graphite base 12 is installed on the copper plate 13, a quartz crucible 7 is placed on the graphite base, a cooling flow channel is opened in the water-cooled ingot rod and the copper plate, the cooling flow channel is connected to a cooling source, and a supporting base is installed on the periphery of the water-cooled ingot rod 14 Seat 11, graphite heating element 8 is installed on the supporting base 11, and thermal insulation sheath 9 is installed on the periphery of graphite heating element 8. The electron gun is installed on the upper part of the vacuum chamber, and the electron beam is aimed at the silicon ingot; the vacuum equipment is equipped with a vacuum device, and the vacuum device adopts a diffusion pump 20, a Roots pump 19 and a mechanical pump 18 installed on the left side of the furnace wall 4, and the furnace wall There is also an air release valve 16 on it.

Example 3

The equipment described in Example 2 is used to efficiently purify polysilicon powder with electron beams. The first step is to prepare materials: put high-purity silicon materials with a phosphorus content of 0.00004% and a total metal content of 0.0002% into a water-cooled copper crucible 17, low in phosphorus, The amount of low-metal high-purity silicon material is three-quarters of the height of the water-cooled copper crucible 17, and the powder baffle 22 is rotated to the bottom of the powder loading bucket 25 by the rotating mechanism 23 to block the bottom of the powder loading bucket 25 Tribe the powder hole, open the powder loading cover 1 and add high phosphorus and high metal silicon powder 24 in the powder loading bucket 25, the high phosphorus and high metal silicon powder 24 loading is slightly lower than the position on the upper edge of the powder loading bucket 25, close the loading Powder cover 1, close vacuum cover 5;

The second step of pretreatment: vacuumize the vacuum chamber 3, and simultaneously use the mechanical pump 18 and the Roots pump 19 to pump the vacuum chamber 3 to a low vacuum of 6Pa, and then use the diffusion pump 20 to pump the vacuum chamber 3 to a high vacuum of 0.001Pa; Pass cooling water into the water-cooled copper crucible 17 through the water-cooled support rod 15, pass into the cooling water in the water-cooled copper plate 13 through the water-cooled ingot rod 14, the temperature of the water-cooled copper crucible and the water-cooled copper plate is maintained at 44 °; preheating electron gun 2 , set the high voltage to 30kw, after 10 minutes of high voltage preheating, turn off the high voltage, set the electron gun 2 beam current to 200mA, and perform preheating, after 10 minutes of preheating, turn off the electron gun 2 beam current;

The third step of purification: open the high voltage and beam current of the electron gun 2, after stabilization, use the electron gun 2 to bombard the low-phosphorus, low-metal high-purity silicon material in the water-cooled copper crucible 17 with a 300mA beam current, so that the low-phosphorus, low-metal high-purity silicon material is melted Form low-phosphorus molten pool 21; after forming low-phosphorous molten pool 21, increase the beam flow of electron gun 2 to 500mA, rotate powder baffle plate 22 by rotating mechanism 23, and powder baffle plate 22 leaves the bottom position of powder loading barrel 25, so that the discharge barrel The high-phosphorus silicon powder 24 in 25 falls into the water-cooled copper crucible 17 for smelting; after smelting for a period of time, the low-phosphorus silicon liquid in the water-cooled copper crucible 17 overflows and flows into the quartz crucible 7, and the low-phosphorus silicon liquid is passed through the graphite heating element 8. The silicon liquid is heated and kept in a liquid state, and is kept in a liquid state with the heat preservation sheath 9 to keep it warm; 2 minutes after the powder falling is completed, the ingot is pulled down through the water-cooled ingot drawing rod 14, and the low-phosphorus silicon liquid 10 is solidified in a directional solidification manner; when the directional solidification is completed Finally, close the electron gun 2, and continue vacuuming for 10 minutes; close the diffusion pump 20, continue vacuuming for 10 minutes, then further close the Roots pump 19, the mechanical pump 18, open the air release valve 16, deflate, and open the vacuum cover 5, from The silicon ingot is taken out from the quartz crucible 7, and finally the part containing more metal impurities on the top of the silicon ingot is cut off. It is measured that the phosphorus content of the obtained silicon ingot is less than 0.00004%, and the total content of metal impurities is less than 0.0002%.

Claims (6)

1. the method for the efficient purifying polycrystalline silicon powder of electron beam, it is characterized in that: carrier HIGH-PURITY SILICON material forms the HIGH-PURITY SILICON molten bath under the electron beam heating, add continuously then and need the purification silica flour, the electron beam melting silica flour, remove the foreign matter of phosphor in the silica flour fast, low-phosphorous silicon hydrorrhea goes out to flow into ingot pulling mechanism and draws ingot, realizes directional solidification effect, and its step is as follows:

The first step is got the raw materials ready: band refrigerative smelting pot bottom the HIGH-PURITY SILICON material of low-phosphorous, low metal is put into, in dress powder bucket, add high phosphorus, the high metallic silicon power that needs purification, and close dress powder lid, close vacuum cover;

The second step pre-treatment: vacuum chamber is vacuumized, use vacuum apparatus that vacuum chamber is extracted into below the high vacuum 0.001Pa simultaneously; Bottom band refrigerative smelting pot and ingot pulling mechanism are cooled off, and temperature maintenance is at 25-45 ℃; Pre-thermionic electron guns, it is 28-30kw that high pressure is set, and the high pressure preheating was closed high pressure after 5-10 minute, and the electron beam gun line is set to 100-200mA, carries out preheating, after preheating 10-15 minute, closes the electron beam gun line;

The 3rd step purified: open the high pressure and the line of electron beam gun, stable back with low-phosphorous, the low metal HIGH-PURITY SILICON material in the band refrigerative smelting pot of 200-300mA line bombardment bottom, makes low-phosphorous, low metal HIGH-PURITY SILICON material fusing form low-phosphorous molten bath with electron beam gun; After forming low-phosphorous molten bath, increase the electron beam gun line to 300-500mA, open dress powder bucket bottom discharge mouth, high phosphorus, high metallic silicon power fall into bottom band refrigerative smelting pot, carry out melting, remove volatile impunty phosphorus; After melting for some time, low-phosphorous silicon hydrorrhea in the band refrigerative smelting pot of bottom goes out, flow in the quartz crucible of ingot pulling mechanism, heat tracing is kept liquid state, wait that powder finishes 1-2 minute, draw spindle blade to pull down ingot by water-cooled, low-phosphorous silicon liquid solidifies in the directional freeze mode, and metallic impurity are gathered in silicon ingot top; Directional freeze is closed electron beam gun after finishing, and continues to vacuumize 15-30 minute, opens the purging valve venting, opens vacuum cover, and the taking-up silicon ingot cuts the silicon ingot top more part of containing metal impurity and gets final product.

2. the equipment of the efficient purifying polycrystalline silicon powder of electron beam is characterized in that: form vacuum apparatus by vacuum cover (5), furnace wall (4) and dress powder lid (1) in the equipment, the vacuum apparatus inner chamber is vacuum chamber (3); The vacuum chamber internal upper part is equipped with the powder bucket, dress powder bucket top has dress powder lid, dress powder lid is positioned on the vacuum furnace wall, dress powder bucket bottom has discharge port, and discharge port is equipped with the outer formula powder blocking plate that drives, and smelting pot is equipped with in dress powder bucket discharge port bottom, the smelting pot bottom is fixed on the vacuum chamber bottom by support bar, ingot pulling mechanism is placed in smelting pot discharge port below, and electron beam gun is installed in vacuum chamber top, and electronic beam current is aimed at silico briquette.

3. the equipment of the efficient purifying polycrystalline silicon powder of a kind of electron beam according to claim 2, it is characterized in that: described vacuum apparatus is equipped with vacuum extractor, vacuum extractor adopts (4) left surface installation diffusion pump (20), lobe pump (19) and mechanical pump (18) in the furnace wall, also offers purging valve (16) on the furnace wall.

4. the equipment of the efficient purifying polycrystalline silicon powder of a kind of electron beam according to claim 2, it is characterized in that: ingot pulling mechanism adopts water-cooled to draw spindle blade to be installed in the bottom of vacuum furnace wall, water-cooled draws spindle blade top that copper coin is installed, the graphite base is installed on the copper coin, place quartz crucible on the graphite base, water-cooled is drawn in spindle blade and the copper coin and is offered coolant flow channel, and coolant flow channel is connected cooling source.

5. the equipment of the efficient purifying polycrystalline silicon powder of a kind of electron beam according to claim 4, it is characterized in that: water-cooled is drawn the peripheral supporting base (11) of installing of spindle blade (14), graphite heater (8) is installed on the supporting base (11), at the peripheral heat insulation sheath (9) of installing of graphite heater (8).

6. according to the equipment of the efficient purifying polycrystalline silicon powder of the arbitrary described a kind of electron beam of claim 2-5, it is characterized in that: driving the formula powder blocking plate outward is L shaped powder blocking plate, and powder blocking plate one end is rotatably installed in the rotating mechanism, and rotating mechanism is installed in outside the vacuum furnace wall.

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