CN102424389A - Solar-grade polysilicon dephosphorization purification method - Google Patents
Solar-grade polysilicon dephosphorization purification method Download PDFInfo
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- CN102424389A CN102424389A CN2011102686695A CN201110268669A CN102424389A CN 102424389 A CN102424389 A CN 102424389A CN 2011102686695 A CN2011102686695 A CN 2011102686695A CN 201110268669 A CN201110268669 A CN 201110268669A CN 102424389 A CN102424389 A CN 102424389A
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Abstract
The invention relates to a solar-grade polysilicon dephosphorization purification method. A high-vacuum induction furnace is adopted, metal silicon raw materials are granules or block materials, and the purity of the metal silicon raw materials is 99 percent. The method comprises the operation steps that: (1) a vacuum system of the high-vacuum induction furnace is started so that a high-vacuum state is reached in a furnace chamber; (2) the metal silicon raw materials are filled into a graphite crucible positioned in the high-vacuum induction furnace, and a high-frequency induction power supply is switched on for melting metal silicon; (3) after the metal silicon raw materials in the second step are melted, the temperature is maintained at 1560 to 1600 DEG C for 12 to 20h, a metal silicon raw material continuous feeding device is started, and the rest metal silicon raw materials are fed into the graphite crucible in the furnace for continuous dephosphorization; and (4) the dephosphorized metal silicon melt volume reaches 2/3 to 3/4 of the crucible volume, the metal silicon melt is poured into another crucible in the same furnace chamber, and the dephosphorized polysilicon is obtained through natural cooling. The method has the advantage that the production cost is low.
Description
Technical field
The present invention relates to a kind of method of purification of solar-grade polysilicon dephosphorization, particularly relate to a kind of method of purification that adopts the continous vacuum dephosphorization.
Background technology
The solar electrical energy generation most important new forms of energy of 21 century of being known as are because sun power has cleaning, safety, resourceful advantage, simultaneously problem such as ability energy shortage and serious.Along with development of science and technology, the electric energy of photovoltaic output is the most high-grade energy, and its Application Areas is extensive, all can play a role in fields such as the electricity consumption of family and public place, street lamp, communication, traffic signal systems.Very application prospects is also arranged in fields such as electronic information, aerospace.Effective development and use of solar energy resources have been played huge pushing effect to The development in society and economy, give the photovoltaic industry with bigger market development space.
But the needed solar energy level silicon of photovoltaic generation mainly is the raw material of producing with chemical technologies such as improvement siemenss at present, though purity is high, its cost can be in any more yet, and there is problem of environment pollution caused in Siemens Method production.But along with the fast development of photovoltaic industry is badly in need of silicon materials in a large number, thereby the silicon raw material has become one of main problem of photovoltaic industry development.
For this reason; Countries in the world are all in the novel process of trying to explore production HIGH-PURITY SILICON material at present; Wherein the physical metallurgy method is because less investment, pollution is little, the construction period is short, production energy consumption is low; And purity satisfies the purity requirement of solar level silicon materials fully about 6N, is considered to can reduce the production of polysilicon cost techniques effectively.The metallurgy method purifying polycrystalline silicon relate generally to technologies such as hydrometallurgy, air blowing, slag making, directional freeze, vacuum induction melting, electron beam, plasma reaction, fused salt electrolysis, alloying smelting.
The content of phosphorus must be less than 0.1ppm in the solar-grade polysilicon.Because the segregation coefficient of phosphorus in silicon is bigger, in pure silicon, reaches 0.35, be difficult to remove through methods such as directional freeze or zone meltings.Developed at present the method for phosphorus impurities in the multiple removal solar-grade polysilicon in the world, like pickling dephosphorization, alloy directionally solidified and vacuum dephosphorization etc.
The method of purification of the polysilicon dephosphorization of more than mentioning has its limitation; Takeshi Yoshikawa and Kazuki Morita. like Tokyo Univ Japan teach the paper of on " Metallurgical And Materials Transaction B " impurity, delivering " pickling adds the thermodynamic study of calcium dephosphorization " (2004; 4:Vol 35BP); The method research that utilizes chemical equilibrium is the interaction of calcium and silicon in the fused silicon under 1732K; Draw and add calcium and help reducing phosphorus segregation coefficient in silicon, form Ca
3P
2, be deposited in SiCa
2Near utilize pickling can remove Ca
3P
2Wherein used pickling, certainly will bring pollution environment.This is not the physics method purifying technique truly that we advocated.
People (Masao Miyake such as Masao Miyake; Tomoki Hiramatus and masafumi Maeda; Removal of Phosphorus and Antimony in Silicon by Electron Beam Melting at low Vacuum, Journal of the Japan Institute of Metals [J], 2006; 70 (1): 43) adopt electron beam melting process 1h under the vacuum condition of 5～7Pa, phosphorus can drop to 1ppmw from 200ppmw.Use the equipment that electron beam involves great expense in this method, be unfavorable for developing the route of low-cost solar level polysilicon industrialization.
The vacuum dephosphorization is because phosphorus saturated vapor pressure at high temperature is far longer than silicon, therefore can under certain high vacuum, the phosphorus volatilization got in the gas phase through the method for vacuum metling, can obtain good phosphor-removing effect.Like people (Noriyoshi Yuge such as Noriyoshi Yuge; Et al.; Removal of Phosphorus, Aluminum and calcium by Evaporation in Molten Silicon [J]. Nippon Kinzoku Gakkaishi/ Journal of the Japan Institute of Metals, 1997; 61 (10): 1 086.) at temperature 1915K, vacuum tightness 8.0 * 10
-3～3.6 * 10
-2Content with phosphorus under the condition of Pa is reduced to below the 0.1ppmw.The index that this method obtains is fine, but its vacuum dephosphorization mode belongs to single crucible intermittent type phosphorus removing method.
Summary of the invention
The technical problem that the present invention will solve is to overcome the difficult problem that above-mentioned prior art is made the polysilicon dephosphorization, and a kind of continous vacuum dephosphorization method of purification of polysilicon cheaply is provided.
The method of purification of polysilicon dephosphorization of the present invention comprises following process step:
(1) selecting Pure Silicon Metal is starting material;
(2) open the vacuum system of high vacuum induction furnace, open prime mechanical pump and DP successively and make and reach high vacuum state in the furnace chamber; Described high vacuum is meant and is controlled at 1.2 * 10
-3～2.4 * 10
-3Pa;
The metallic silicon raw material that (3) will account for plumbago crucible capacity 1/10 is packed into and is arranged in the plumbago crucible of high vacuum induction furnace, opens high frequency induction power supply Pure Silicon Metal is melted; Described high frequency induction power supply power is preferably 200～280KW;
(4) treat to make the Pure Silicon Metal liquid temp remain on 1560～1600 ℃ after the fusing of (3) step metallic silicon raw material, constant temperature time is that the required time of whole dephosphorizing process is 12～20 hours.
Opening metal silicon raw material continuous feeding device drops in the plumbago crucible in residual metallic silicon raw material to the stove and carries out continuous dephosphorization;
(5) the Pure Silicon Metal melt volume behind the dephosphorization reaches crucible volumetrical 2/3～3/4 o'clock, and with in another crucible in the furnace chamber, naturally cooling 5 hours obtains the dephosphorization polysilicon with the impouring of Pure Silicon Metal melt.
In the described step (1), the particle diameter of said Pure Silicon Metal is 5～100mm, and the purity of its Pure Silicon Metal is more than 99% (2N), and wherein B content is 5ppm, and P content is 25ppm.
In the described step (4), described continuous feeding mechanism is meant and can successive Pure Silicon Metal be sent into the molten indoor dephosphorization purifying plant of high vacuum.Adopt dephosphorization method of purification of the present invention, can make the content of P be reduced to below the 0.1ppm, meet the required purity requirement of solar-grade polysilicon P content fully.
The present invention is raw material with the Pure Silicon Metal, obtains the production of the low-phosphorous polysilicon of solar level cheaply through successive polysilicon dephosphorizing technology.Because the production process of dephosphorization of the present invention is continuously Pure Silicon Metal to be added in the high vacuum furnace in the crucible, has so just improved the efficient of dephosphorization greatly.This dephosphorizing method does not need expensive equipments such as plasma body, electron beam gun.The present invention can also combine with the vertical pulling demetal process and be integrated into the demetallated technology of a cover successive dephosphorization, has considerable market outlook.Because this dephosphorization demetalization is the continous way operation, this just is fit to extensive industrialization very much.And the cost that utilizes the 6N level solar-grade polysilicon that this invention produces is well below in the market polysilicon price.
Embodiment
Below provide solar-grade polysilicon dephosphorization method of purification specific embodiment of the present invention.
Embodiment 1:
Employing can hold the plumbago crucible of metallic silicon raw material 200kg, and taking by weighing P concentration is the metallic silicon raw material 200kg of 25ppm.The prime mechanical pump of open vacuum system and high-performance DP are evacuated to 1.2 * 10 with vacuum in the furnace chamber successively
-3Pa.Send into metallic silicon raw material 20kg to plumbago crucible through pay-off, open the high frequency electric source heating and make silicon be molten into silicon melt, the silicon melt temperature is controlled at 1500 ℃, and power is 200KW.Open the continuous feeding device remaining 180kg metallic silicon raw material dropped in the crucible, until the silicon melt volume reach the plumbago crucible volume 2/3 after, pour silicon melt into be arranged in same furnace chamber another crucible and be cooled to silicon ingot, accomplishing dephosphorizing process is 12 hours.Cooled silicon ingot sampling is detected, and P content is 0.1ppm.
Embodiment 2
Technological process is with embodiment 1, and taking by weighing P concentration is 25ppm feed metal silicon 200kg.Employing can hold the plumbago crucible of 200kg silicon material.The prime mechanical pump of open vacuum system and high-performance DP are evacuated to 2.0 * 10 with vacuum in the furnace chamber successively
-3Pa.Send into the 20kg Pure Silicon Metal to plumbago crucible through pay-off, open the high frequency electric source heating and make the silicon fusing, melt temperature is controlled at 1600 ℃, and power is 240KW.Open the continuous feeding device feed metal silicon dropped in the crucible, until the silicon melt volume reach the plumbago crucible volume 3/4 after, be poured into another crucible that is arranged in same furnace chamber, whole completion dephosphorizing process is 16 hours.With therefrom sampling detection after the silicon ingot cooling, P content is 0.06ppm.
Embodiment 3
Technological process is with embodiment 1, and P concentration is 25ppm feed metal silicon 300kg in the silicon material.Employing can hold the plumbago crucible of 300kg silicon material.Vacuum is evacuated to 1.0 * 10 in the furnace chamber
-3Pa.Melt temperature is controlled at 1650 ℃, and power is 280KW.Whole completion dephosphorizing process is 20 hours.With therefrom sampling detection after the silicon ingot cooling, P content is 0.02ppm.
Claims (1)
1. the method for purification of a solar-grade polysilicon dephosphorization is characterized in that equipment for purifying adopts high vacuum induction furnace, and particle diameter is that the Pure Silicon Metal of 5～100mm is a raw material; The purity of metallic silicon raw material is 99%; Be more than the 2N, wherein B content is 5ppm, and P content is 25ppm; Its operation steps is:
(1) opens the vacuum system of high vacuum induction furnace, open prime mechanical pump and DP successively and make and reach high vacuum state in the furnace chamber; Described high vacuum is meant and is controlled at 1.2 * 10
-3～2.4 * 10
-3Pa;
The metallic silicon raw material that (2) will account for plumbago crucible capacity 1/10 is packed into and is arranged in the plumbago crucible of high vacuum induction furnace, opens high frequency induction power supply Pure Silicon Metal is melted; Described high frequency induction power supply power is 200～280KW;
(3) treat to make the Pure Silicon Metal liquid temp remain on 1560～1600 ℃ after the fusing of (2) step metallic silicon raw material; Need to keep 12 to 20 hours; Opening metal silicon raw material continuous feeding device drops in the plumbago crucible in residual metallic silicon raw material to the stove and carries out continuous dephosphorization;
(4) the Pure Silicon Metal melt volume behind the dephosphorization reaches crucible volumetrical 2/3～3/4 o'clock, and with in another crucible in the furnace chamber, naturally cooling 5 hours just obtains the dephosphorization polysilicon with the impouring of Pure Silicon Metal melt.
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102815700A (en) * | 2012-09-18 | 2012-12-12 | 复旦大学 | Method for preparing nanometer silicon carbide by recycling silicon cut wastes |
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|---|---|---|---|---|
| CN101318655A (en) * | 2008-06-19 | 2008-12-10 | 大连理工大学 | Method and device for removing foreign matter of phosphor in polysilicon |
| CN101628719A (en) * | 2009-08-19 | 2010-01-20 | 厦门大学 | Method for removing phosphorus impurities in silicon by vacuum induction melting |
| US20100239484A1 (en) * | 2009-03-19 | 2010-09-23 | Jiawei Solar (Wuhan) Co., Ltd. | Method for Refining Solar Grade (SoG) Silicon by Using Physical Metallurgy |
| CN102120579A (en) * | 2011-01-29 | 2011-07-13 | 大连隆田科技有限公司 | Method and device for efficiently and continuously smelting and purifying polysilicon with electron beams |
| CN102173424A (en) * | 2011-01-31 | 2011-09-07 | 大连理工大学 | Method and equipment for removing phosphorus and metal impurities in ganister sand through vacuum induction melting |
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2011
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Patent Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101318655A (en) * | 2008-06-19 | 2008-12-10 | 大连理工大学 | Method and device for removing foreign matter of phosphor in polysilicon |
| US20100239484A1 (en) * | 2009-03-19 | 2010-09-23 | Jiawei Solar (Wuhan) Co., Ltd. | Method for Refining Solar Grade (SoG) Silicon by Using Physical Metallurgy |
| CN101628719A (en) * | 2009-08-19 | 2010-01-20 | 厦门大学 | Method for removing phosphorus impurities in silicon by vacuum induction melting |
| CN102120579A (en) * | 2011-01-29 | 2011-07-13 | 大连隆田科技有限公司 | Method and device for efficiently and continuously smelting and purifying polysilicon with electron beams |
| CN102173424A (en) * | 2011-01-31 | 2011-09-07 | 大连理工大学 | Method and equipment for removing phosphorus and metal impurities in ganister sand through vacuum induction melting |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102815700A (en) * | 2012-09-18 | 2012-12-12 | 复旦大学 | Method for preparing nanometer silicon carbide by recycling silicon cut wastes |
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