CN103072994B - Electrophoretic assistant slag forming and boron removing method - Google Patents
Electrophoretic assistant slag forming and boron removing method Download PDFInfo
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- CN103072994B CN103072994B CN201310044709.7A CN201310044709A CN103072994B CN 103072994 B CN103072994 B CN 103072994B CN 201310044709 A CN201310044709 A CN 201310044709A CN 103072994 B CN103072994 B CN 103072994B
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Abstract
The invention relates to the field of purification of solar grade polycrystalline silicon, and in particular to an electrophoretic assistant slag forming and boron removing method. The method comprises the steps of: filling raw material silicon to a graphite crucible and completely melting silicon to a silicon liquid; maintaining temperature of the silicon liquid at 1500-1800 DEG C, and adding a slag former to the silicon liquid to form slag; applying a direct current voltage to the silicon liquid in the graphite crucible so as to transfer borides and metal impurities after reaction to the cathode; carrying out directional solidification on the silicon liquid and cooling and taking out a silicon ingot as well as incising the upper impurity enriching area to obtain purified polycrystalline silicon. According to the method provided by the invention, a part of metal impurities is removed while the borides are removed. The use level of the slag former is reduced, the cost is lowered, and the industrial waste is reduced.
Description
Technical field
The present invention relates to solar-grade polysilicon purification field, especially relate to the auxiliary slagging boron removal method of a kind of electrophoresis.
Background technology
At current energy worsening shortages, under the day by day serious background of environmental pollution, solar energy power generating is due to features such as technology maturation, resource are never exhausted, environmental pressure is little, becomes 21 century to be hopeful one of clean energy of large-scale application most, with unique advantage, enjoys countries in the world to pay close attention to.Polysilicon is described as " blood of modern industry, the foundation stone of microelectronics information industry ", is basic raw material and the strategic material of development electronics and photovoltaic industry.
Polycrystalline silicon purifying mainly contains chemical method and metallurgy method at present.Chemical method mainly contains improved Siemens, silane thermal decomposition process and fluidized bed process, utilize chemical method to purify and can obtain polysilicon more than purity 9N, but chemical method investment is large, energy consumption is high and seriously polluted.Metallurgy method is produced polysilicon and is referred to take metallurgical grade industrial silicon as raw material, in the situation that not changing silicon materials physical property, silicon to be purified, the purity of Pure Silicon Metal is not less than 99.9999%, boron content is not higher than 0.3ppm, to be suitable as the requirement of solar cell material.This method most important feature is that production cost is low, and the pollution causing to environment is little, simple to operate, easily scale operation.
In polysilicon, impurity is divided into metallic impurity and nonmetallic impurity.Metallic impurity are because segregation coefficient is much smaller than 1, and available directional solidification method is removed.And nonmetallic impurity B, the P segregation coefficient in silicon is 0.8,0.35, far above metallic element, particularly B, close to 1, cannot remove by directional freeze, also cannot be as P because saturation steam forces down, and vacuum available melting is removed.At present except the main method of boron has slag making, air blowing, pickling, vacuum, electron beam, plasma body etc.Slagging boron removal is the at present main boron mode of removing, and effect is remarkable and cost is low, is suitable for industrialization and produces.
Patent No. CN101671023 discloses a kind of boron-removing purification method of polysilicon, by adding two kinds of slag formers to reach the object except boron.Patent No. CN101774584 discloses the method for purification of solar energy level silicon, by the method for pickling, ventilation, a large amount of slag former slag making, removes boron.Above-mentioned patent is used the quantity of slag large, bad except effect of boron, and easily introduces impurity.
Summary of the invention
Primary goal of the invention of the present invention is to propose the auxiliary slagging boron removal method of a kind of electrophoresis.
In order to realize object of the present invention, the technical scheme of employing is:
The present invention relates to the auxiliary slagging boron removal method of a kind of electrophoresis, described method comprises the following steps:
(1) raw silicon being packed into induction heating in plumbago crucible, to being molten into silicon liquid completely, keeps silicon liquid temp at 1500～1800 ℃;
(2) slag former is added in silicon liquid, after heat fused with the abundant contact reacts of silicon liquid;
(3) graphite cake is positioned over to the upper surface of molten silicon liquid, the negative pole of graphite cake and extraneous volts DS joins, the positive pole of plumbago crucible and extraneous volts DS joins, to plumbago crucible, apply volts DS, switch on after 1～6 hour, reacted boride and metallic impurity are entered in slag to negative pole migration;
(4) keep silicon liquid temp at 1450～1550 ℃, under switch-on regime, plumbago crucible is take the speed of 0.10～0.15mm/min as decline, leave heating zone, carry out directional freeze, cooling rear taking-up silicon ingot, and excise impurity enriched district, upper strata, polysilicon after being purified.
The first optimal technical scheme of the present invention is: in step (1), in described silicon, the content of impurity is: B is 2ppm, and Fe is 747ppm, and Al is 535ppm, and Ca is 29ppm.
The second optimal technical scheme of the present invention is: in step (2), described slag former is Na
2cO
3-TiO
2-SiO
2compound slag system, its composition is by mass percentage: Na
2cO
330～40%, TiO
210～20%, remaining is SiO
2; Preferably Na
2cO
330～35%, TiO
215～20%, remaining is SiO
2.
The 3rd optimal technical scheme of the present invention is: in step (2), the mass ratio of raw silicon and slag former is 1:0.5～1.
The 4th optimal technical scheme of the present invention is: in step (3), electrophoresis power is direct supply, and voltage is 10～100V, preferably 10～50V.
The 5th optimal technical scheme of the present invention is: in step (3), be 2～4 hours conduction time.
The 6th optimal technical scheme of the present invention is: in step (4), impurity enriched district, the upper strata thickness excising accounts for 10% of whole silicon ingot.
The 7th optimal technical scheme of the present invention is: in step (4), the content of the B in the target product obtaining is that the content of 0.2～0.3ppm, metallic impurity is less than 0.1ppm.
Below technical scheme of the present invention is made further explanation.
The technical superiority of deslagging method of the present invention is:
1. the present invention adopts Na
2cO
3-TiO
2-SiO
2compound slag system, reacts with the boron in silicon and produces boron oxide and boride; Slag making of the present invention be simple and easy to get, cost is low, abundant with boron reaction bonded;
2. after slag making, in silicon liquid, apply volts DS, make metallic impurity and boride move and enter in slag to slag, method of the present invention can, when removing boride, be removed a part of metallic impurity; And reduced the consumption of slag former, the cost of reduction, has reduced industrial waste;
3. after slag making, carry out directional freeze, remove metallic impurity, the metallic pollution of having avoided slag making to introduce is further removed residual boride in silicon simultaneously.
The specific embodiment of the present invention only limits to further explain and explanation the present invention, not to Composition of contents restriction of the present invention.
Embodiment
Embodiment 1
(1) get 100kg industrial silicon and pack in plumbago crucible, open intermediate frequency furnace melting switch, regulate intermediate frequency power to make industrial silicon completely molten
Turn to silicon liquid;
(2) adjust intermediate frequency furnace power, keep above-mentioned silicon liquid temp at 1500 ℃, in silicon liquid, add 50kg slag former, wherein Na
2cO
330%, TiO
210%, remaining is SiO
2;
(3) graphite cake is positioned over to the upper surface of molten silicon liquid, the negative pole of graphite cake and extraneous volts DS joins, the positive pole of plumbago crucible and extraneous volts DS joins, and to above-mentioned plumbago crucible, applies 10V volts DS 6h, and reacted slag and metallic impurity are moved to negative pole;
(4) keep silicon liquid temp at 1450 ℃, under switch-on regime, plumbago crucible is take the speed of 0.15mm/min as decline, leave heating zone, carry out directional freeze, cooling rear taking-up silicon ingot, and excising impurity enriched district, upper strata, impurity enriched district, the upper strata thickness excising accounts for 10% of whole silicon ingot.Obtain the silicon ingot after directional freeze, the content of boron, iron, aluminium and calcium is measured, result is as table 1.
Embodiment 2
(1) get 100kg industrial silicon and pack in plumbago crucible, open intermediate frequency furnace melting switch, regulate intermediate frequency power to make industrial silicon be molten into silicon liquid completely;
(2) adjust intermediate frequency furnace power, keep above-mentioned silicon liquid temp at 1650 ℃, in silicon liquid, add 70kg slag former, wherein Na
2cO
335%, TiO
215%, remaining is SiO
2;
(3) graphite cake is positioned over to the upper surface of molten silicon liquid, the negative pole of graphite cake and extraneous volts DS joins, the positive pole of plumbago crucible and extraneous volts DS joins, and to above-mentioned plumbago crucible, applies 50V volts DS 3h, and reacted slag and metallic impurity are moved to negative pole;
(4) keep silicon liquid temp at 1500 ℃, under switch-on regime, plumbago crucible is take the speed of 0.13mm/min as decline, leave heating zone, carry out directional freeze, cooling rear taking-up silicon ingot, and excising impurity enriched district, upper strata, impurity enriched district, the upper strata thickness excising accounts for 10% of whole silicon ingot.Obtain the silicon ingot after directional freeze, the content of boron, iron, aluminium and calcium is measured, result is as table 1.
Embodiment 3
(1) get 100kg industrial silicon and pack in plumbago crucible, open intermediate frequency furnace melting switch, regulate intermediate frequency power to make industrial silicon be molten into silicon liquid completely;
(2) adjust intermediate frequency furnace power, keep above-mentioned silicon liquid temp at 1800 ℃, in silicon liquid, add 100kg slag former, wherein Na
2cO
340%, TiO
220%, remaining is SiO
2;
(3) graphite cake is positioned over to the upper surface of molten silicon liquid, the negative pole of graphite cake and extraneous volts DS joins, the positive pole of plumbago crucible and extraneous volts DS joins, and to above-mentioned plumbago crucible, applies 100V volts DS 2h, and reacted slag and metallic impurity are moved to negative pole;
(4) keep silicon liquid temp at 1550 ℃, under switch-on regime, plumbago crucible is take the speed of 0.10mm/min as decline, leave heating zone, carry out directional freeze, cooling rear taking-up silicon ingot, and excising impurity enriched district, upper strata, impurity enriched district, the upper strata thickness excising accounts for 10% of whole silicon ingot.Obtain the silicon ingot after directional freeze, the content of boron, iron, aluminium and calcium is measured, result is as table 1.
By the result of gained in above-described embodiment, by ICP-MS, measure the content of B and metallic impurity in silicon, measuring result is as table 1.
Table 1:
| ? | B/ppm | Fe/ppm | Al/ppm | Ca/ppm |
| Raw material | 2 | 747 | 535 | 29 |
| Embodiment 1 | 0.28 | <0.05 | <0.05 | <0.05 |
| Embodiment 2 | 0.20 | <0.05 | <0.05 | <0.05 |
| Embodiment 3 | 0.21 | <0.05 | <0.05 | <0.05 |
Claims (9)
1. the auxiliary slagging boron removal method of electrophoresis, is characterized in that, described method comprises the following steps:
(1) raw silicon being packed into induction heating in plumbago crucible, to being molten into silicon liquid completely, keeps silicon liquid temp at 1500～1800 ℃;
(2) slag former is added in silicon liquid, after heat fused with the abundant contact reacts of silicon liquid; Described slag former is Na
2cO
3-TiO
2-SiO
2compound slag system, its composition is by mass percentage: Na
2cO
330～40%, TiO
210～20%, remaining is SiO
2;
(3) graphite cake is positioned over to the upper surface of molten silicon liquid, the negative pole of graphite cake and extraneous volts DS joins, the positive pole of plumbago crucible and extraneous volts DS joins, to plumbago crucible, apply volts DS, switch on after 1～6 hour, reacted boride and metallic impurity are entered in slag to negative pole migration;
(4) keep silicon liquid temp at 1450～1550 ℃, under switch-on regime, plumbago crucible declines with the speed of 0.10～0.15mm/min, leave heating zone, carry out directional freeze, cooling rear taking-up silicon ingot, and excise impurity enriched district, upper strata, the polysilicon after being purified.
2. the auxiliary slagging boron removal method of a kind of electrophoresis according to claim 1, is characterized in that, in step (1), in described raw silicon, the content of impurity is: B is 2ppm, and Fe is 747ppm, and Al is 535ppm, and Ca is 29ppm.
3. the auxiliary slagging boron removal method of a kind of electrophoresis according to claim 1, is characterized in that, in step (2), and Na in described slag former
2cO
330～35%, TiO
215～20%, remaining is SiO
2.
4. the auxiliary slagging boron removal method of a kind of electrophoresis according to claim 1, is characterized in that, in step (2), the mass ratio of raw silicon and slag former is 1:0.5～1.
5. the auxiliary slagging boron removal method of a kind of electrophoresis according to claim 1, is characterized in that, in step (3), electrophoresis power is direct supply, and voltage is 10～100V.
6. the auxiliary slagging boron removal method of a kind of electrophoresis according to claim 5, is characterized in that, voltage is 10～50V.
7. the auxiliary slagging boron removal method of a kind of electrophoresis according to claim 1, is characterized in that, in step (3), be 2～4 hours conduction time.
8. the auxiliary slagging boron removal method of a kind of electrophoresis according to claim 1, is characterized in that in step (4), and impurity enriched district, the upper strata thickness excising accounts for 10% of whole silicon ingot.
9. the auxiliary slagging boron removal method of a kind of electrophoresis according to claim 1, is characterized in that in step (4), and in the polysilicon after the purification obtaining, the content of B is that the content of 0.2～0.3ppm, metallic impurity is less than 0.1ppm.
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| CN103420378B (en) * | 2013-08-05 | 2015-02-25 | 大连理工大学 | Slag former for smelting polycrystalline silicon medium and use method of slag former |
| CN103420377B (en) * | 2013-08-05 | 2015-04-22 | 大连理工大学 | Slag-forming agent for removing boron during medium melting of polycrystallization silicon and using method of slag-forming agent |
| CN103420599A (en) * | 2013-08-05 | 2013-12-04 | 大连理工大学 | Slag former for removing boron in process of smelting polycrystalline silicon medium and use method of slag former |
| CN104724704B (en) * | 2015-03-18 | 2017-11-14 | 中国科学院过程工程研究所 | A kind of method of electric field-enhanced slag Refining silicon alloy |
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| CN101456558A (en) * | 2007-12-14 | 2009-06-17 | 邹学柏 | Production process of solar polycrystalline silicon material |
| CN101824650B (en) * | 2010-05-20 | 2012-06-06 | 上海太阳能电池研究与发展中心 | Purifying system of high purity polysilicon and purifying method |
| CN102139878B (en) * | 2011-02-18 | 2013-02-06 | 厦门大学 | Method for removing boron impurity from industrial silicon by using titanium-containing compound |
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Effective date of registration: 20210616 Address after: No.1-2, fukeng huyangtangbei Road, Sheshan village, Nanyang Town, Shanghang County, Longyan City, Fujian Province 364211 Patentee after: Fujian Shanghang Xingheng silicon products Co.,Ltd. Address before: 364211 No.1, Yanhe Road, Mayang cave, Nanyang Town, shangkeng County, Longyan City, Fujian Province Patentee before: FUJIAN XING THE ZHAOYANG SILICON MATERIALS Co.,Ltd. |