CN102219221A - Method for purifying polycrystalline silicon by directional solidification and slag refining - Google Patents

Method for purifying polycrystalline silicon by directional solidification and slag refining Download PDF

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Publication number
CN102219221A
CN102219221A CN2011101521638A CN201110152163A CN102219221A CN 102219221 A CN102219221 A CN 102219221A CN 2011101521638 A CN2011101521638 A CN 2011101521638A CN 201110152163 A CN201110152163 A CN 201110152163A CN 102219221 A CN102219221 A CN 102219221A
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polycrystalline silicon
silicon
directional solidification
directional
slag
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CN102219221B (en
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谭毅
许富民
张磊
胡跟兄
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Dalian University of Technology
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Dalian University of Technology
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Abstract

The invention belongs to the technical field of purifying polycrystalline silicon by physical metallurgy technology. A method for purifying polycrystalline silicon by directional solidification and slag refining comprises the following steps: firstly, mixing polycrystalline silicon material and acid slag former uniformly so as to form mixture, then arranging the mixture into a melting crucible of a directional solidification furnace, slagging and melting the mixture in the melting crucible, simultaneously, conducting directional solidification so as to concentrate metal impurity and waste slag on the top of a silicon ingot, removing boron and metal impurity, and finally cutting the top of the silicon ingot, thus obtaining polycrystalline silicon ingot with low boron and metal content. The method has the following obvious effects: the acid slag former for slagging and melting and the directional solidification are adopted simultaneously, the impurity boron in the polycrystalline silicon is removed by the slagging of the acid slag former and the refining, simultaneously, the metal impurity with a smaller segregation coefficient in the polycrystalline silicon is removed by the directional solidification technology, the purity of the polycrystalline silicon material is improved, so that polycrystalline silicon material achieves the using requirement of solar-level polycrystalline silicon material.

Description

A kind of method of directional freeze slag making refining purifying polycrystalline silicon
Technical field
The invention belongs to the technical field with physical metallurgy technology purifying polycrystalline silicon, particularly a kind of directional solidification technique that utilizes carries out the slag making melting, thereby removes the method for boron and metallic impurity in the polysilicon.
Background technology
In energy scarcity, the society that advocates low-carbon environment-friendly, sun power has great application value as a kind of environmental protection new forms of energy.In recent years, the global solar photovoltaic industry increases rapidly, and solar cell yield increases fast, direct pull the rapid expansion of solar energy polycrystalline silicon demand.
The method of purifying solar energy polysilicon mainly contains chemical purification and physical purification at present, and chemical purification mainly is a Siemens Method, and its advantage is the product purity height, quality better, but its technology grasps in minority developed country, and corresponding investment is big, the cost height also can produce obnoxious flavour.Metallurgy method is to make the popular method of polysilicon at present, its output height, less investment, cost is low, pollution-free, along with the fast development of this research field in recent years, it is ripe that the technological line of metallurgy method purifying solar energy level polysilicon is tending towards, the employing directional solidification processes can effectively be removed metallic impurity wherein, and electron beam melting can be removed impurity P, and the difficult point of concentrating is the removal to impurity B at present, because the segregation coefficient of B big (being 0.8), saturation steam forces down, and can't remove with aforesaid way, is badly in need of a kind of less energy-consumption at present and can effectively removes the method for B.
The slag making melting is a kind of method of effective removal B impurity, mode by high temperature slag making melting can effectively generate boron oxide compound with the B impurity and the reaction of the oxidisability composition in the slag agent of melting in the silicon, sepn process with slag agent and silicon liquid is removed, and therefore utilizing slag making to remove B is a kind of efficient ways.Slag making melting slag former commonly used has CaO-SiO 2, Na 2O-CaO-SiO 2, CaF 2-CaO-SiO 2Deng, the Suzuki of Japan and Sano studied calcium be slag remove B effect, BaO-CaO-SiO 2The maximum allocated coefficient that system obtains is about 2, and therefore will reach the solar energy level silicon material requirements just need carry out repeatedly slag making, perhaps very big slag silicon ratio, and this feasibility in requiring the low-cost industrial popularization is little.The Morita of Japan etc. has done systematic research to the slag making melting, draws the basicity that the principal element that influences partition ratio has the slag agent, oxygen partial pressure and the B distribution in melt, but finally neither be very desirable, be difficult to reach industrialization demands.
Disclose the patent No. in the prior art and be the preparation method of a kind of solar energy level silicon of 200810068908.0 and the patent No. and be 201010215098.4 metallurgy method and prepared the method for solar-grade polysilicon and the polysilicon of this method preparation, but the type of heating of the directional solidification furnace that the slag making melting is adopted in these two patents is the induction melting heating, this type of heating produces bigger disturbance to the white residue melt, be unfavorable for the stable separation of reacted waste residue from melt, the removal effect of boron is not good.
Summary of the invention
The objective of the invention is to overcome above-mentioned not enough problem, a kind of method of directional freeze slag making refining purifying polycrystalline silicon is provided,, remove boron and metallic impurity simultaneously, reach the service requirements of solar grade polycrystalline silicon material in conjunction with utilizing slag making melting and directional solidification technique.
The technical scheme that the present invention is adopted for achieving the above object is: a kind of method of directional freeze slag making refining purifying polycrystalline silicon, at first polycrystalline silicon material and acid slag former are uniformly mixed to form compound, then compound is put in directional solidification furnace (referring to patent of invention: a kind of polysilicon directional freezing equipment, ZL200810012354.2) in the smelting pot, in smelting pot, carry out the slag making melting, carrying out directional freeze simultaneously makes metallic impurity and waste residue accumulate in the top of silicon ingot, remove boron and metallic impurity simultaneously, cut the top of silicon ingot at last, obtain low boron, the polycrystal silicon ingot of low metal.
Described concrete steps are as follows:
At first, put into 60 ℃ of oven dry of drying baker, the polycrystalline silicon material and the acid slag former of drying is uniformly mixed to form compound in proportion polycrystalline silicon material washed with de-ionized water 4-5 time;
Then compound is slowly poured in the smelting pot in the directional solidification furnace, close bell, opening mechanical pump is evacuated to below the 900Pa, after open lobe pump and be evacuated to below the 4Pa, open the top of directional solidification furnace, three graphite heaters in sidepiece and bottom, and keep the power of three heating elements identical, the beginning heat temperature raising, when temperature is increased to 1100-1200 ℃, the argon shield of feed flowing is incubated 0.5-3h after being warming up to 1500-1700 ℃, reduces bottom graphite heater power earlier, the back reduces sidepiece graphite heater power, make the white residue melt from the bottom to top formation temperature gradient, reduce simultaneously the temperature of white residue melt according to the rate of cooling of 0.1-5 ℃/min, produce directional freeze, the white residue melt all solidifies the after-acceleration cooling, up to being cooled to room temperature;
Take out silicon ingot at last, cut silicon ingot top metal impurity and waste residue, can obtain the polycrystal silicon ingot of low boron, low metal.
The polycrystalline silicon material of described adding is piece material or powder.
The acid slag former of described adding is SiO 2-CaO-Na 2CO 3Or SiO 2-CaO-Na 2O, wherein SiO 2Mass percent is 60-80%, and the CaO mass percent is 15-25%, Na 2CO 3Or Na 2The O mass percent is 5-15%.
The ratio of acid slag former and silicon material is 0.1-1.5 in the described compound.
Described smelting pot can be quartz crucible, plumbago crucible, SiC crucible, MgO crucible and Si 3N 4Crucible.
Unusual effect of the present invention is a method of using acid slag former slag making melting and directional freeze simultaneously, by the boron impurities in the acid slag former slag making refining removal polysilicon, remove the less metallic impurity of segregation coefficient in the polysilicon by directional solidification technique simultaneously, improve the purity of polycrystalline silicon material, make it reach the service requirements of solar grade polycrystalline silicon material, this technology is removed boron, it is effective to remove metallic impurity, method is simple, use the stronger acid slag former oxidisable impurity boron of oxidisability to form the oxide compound of boron earlier, this oxide compound will be attached among the slag agent, after carry out directional freeze the slag agent constantly assembled to melt top, directional freeze also makes metallic impurity to the enrichment of melt top simultaneously, cut the silicon ingot top of being rich in impurity and can remove boron and metallic impurity, realize that simultaneously acid slag former slag making melting removes the double effects that boron and directional freeze are removed metallic impurity, reaches quick, effectively remove the purpose of impurity in the polysilicon.
Description of drawings
Accompanying drawing 1 is the method flow diagram of directional freeze slag making refining purifying polycrystalline silicon of the present invention.
Embodiment
Describe the present invention in detail below in conjunction with specific embodiments and the drawings, but the present invention is not limited to specific embodiment.
Embodiment 1
At first getting boron content is 0.001%, and total metal content is 0.05% polysilicon block material, uses washed with de-ionized water 5 times, puts into 60 ℃ of oven dry down of drying baker, gets the polysilicon block material and the acid slag former SiO of 500g of 500g oven dry 2-CaO-Na 2CO 3By slag silicon ratio is 1 uniform mixing, forms compound, wherein acid slag former SiO 2-CaO-Na 2CO 3The shared mass percent of each component is SiO 280%, CaO15% and Na 2CO 35%;
Then compound is slowly poured in the plumbago crucible in the directional solidification furnace, close bell, open mechanical pump and be evacuated to 800Pa, after open lobe pump and be evacuated to 3Pa, open the top of directional solidification furnace, three graphite heaters in sidepiece and bottom, and keep the power of three heating elements identical, the beginning heat temperature raising, when temperature is increased to 1200 ℃, the argon shield of feed flowing is incubated 1h after being warming up to 1500 ℃, reduces bottom graphite heater power earlier, the back reduces sidepiece graphite heater power, make the white residue melt from the bottom to top portion formation temperature gradient, reduce simultaneously the temperature of white residue melt according to the rate of cooling of 0.1 ℃/min, produce directional solidification effect, the white residue melt all solidifies the after-acceleration cooling, up to being cooled to room temperature;
Take out silicon ingot at last, cut silicon ingot top metal impurity and waste residue, the polycrystal silicon ingot that obtains boron content by analysis is lower than 0.0001%, and the metallic impurity total content is lower than 0.0005%.
Embodiment 2
At first getting boron content is 0.0015%, and total metal content is 0.06% polysilicon block material, uses washed with de-ionized water 5 times, puts into 60 ℃ of oven dry down of drying baker, gets the polysilicon block material and the acid slag former SiO of 600g of 500g oven dry 2-CaO-Na 2O is 1.2 to be uniformly mixed to form compound, wherein acid slag former SiO by slag silicon ratio 2-CaO-Na 2The shared mass percent of each component of O is SiO 260%, CaO25% and Na 2O15%;
Then compound is slowly poured in the plumbago crucible in the directional solidification furnace, close bell, open mechanical pump and be evacuated to 800Pa, after open lobe pump and be evacuated to 3Pa, open the top of directional solidification furnace, three graphite heaters in sidepiece and bottom, and keep the power of three heating elements identical, the beginning heat temperature raising, when temperature is increased to 1200 ℃, the argon shield of feed flowing is incubated 2h after being warming up to 1600 ℃, reduces bottom graphite heater power earlier, the back reduces sidepiece graphite heater power, make the white residue melt from the bottom to top portion formation temperature gradient, reduce simultaneously the temperature of white residue melt according to the rate of cooling of 0.2 ℃/min, produce directional solidification effect, the white residue melt all solidifies the after-acceleration cooling, up to being cooled to room temperature;
Take out silicon ingot at last, cut silicon ingot top metal impurity and waste residue, the polycrystal silicon ingot that obtains boron content by analysis is lower than 0.00008%, and the metallic impurity total content is lower than 0.0008%.
The present invention removes boron, consistent through case test except that metal effect, and refining effect is good, and energy consumption is little, and cost is low, and technology is simple, and the cycle is short, and production efficiency is higher.

Claims (6)

1. the method for a directional freeze slag making refining purifying polycrystalline silicon, it is characterized in that, at first polycrystalline silicon material and acid slag former are uniformly mixed to form compound, then compound is put in the smelting pot of directional solidification furnace, in smelting pot, carry out the slag making melting, carry out directional freeze simultaneously and make metallic impurity and waste residue accumulate in the top of silicon ingot, remove boron and metallic impurity, cut the top of silicon ingot at last, obtain the polycrystal silicon ingot of low boron, low metal.
2. the method for a kind of directional freeze slag making refining purifying polycrystalline silicon according to claim 1 is characterized in that concrete steps are as follows:
At first, put into 60 ℃ of oven dry of drying baker, the polycrystalline silicon material and the acid slag former of drying is uniformly mixed to form compound by a certain percentage polycrystalline silicon material washed with de-ionized water 4-5 time;
Then compound is slowly poured in the smelting pot in the directional solidification furnace, close bell, opening mechanical pump is evacuated to below the 900Pa, after open lobe pump and be evacuated to below the 4Pa, open the top of directional solidification furnace, three graphite heaters in sidepiece and bottom, and keep the power of three heating elements identical, the beginning heat temperature raising, when temperature is increased to 1100-1200 ℃, the argon shield of feed flowing is incubated 0.5-3h after being warming up to 1500-1700 ℃, reduces bottom graphite heater power earlier, the back reduces sidepiece graphite heater power, make the white residue melt from the bottom to top portion formation temperature gradient, reduce simultaneously the temperature of white residue melt according to the rate of cooling of 0.1-5 ℃/min, produce directional solidification effect, the white residue melt all solidifies the after-acceleration cooling, up to being cooled to room temperature;
Take out silicon ingot at last, cut silicon ingot top metal impurity and waste residue, can obtain the polycrystal silicon ingot of low boron, low metal.
3. require the method for described directional freeze slag making refining purifying polycrystalline silicon according to right 1 or 2, it is characterized in that described acid slag former is SiO 2-CaO-Na 2CO 3Or SiO 2-CaO-Na 2O, wherein SiO 2Mass percent is 60-80%, and the CaO mass percent is 15-25%, Na 2CO 3Or Na 2The O mass percent is 5-15%.
4. require the method for described directional freeze slag making refining purifying polycrystalline silicon according to right 1 or 2, it is characterized in that, the acid slag former of described compound and the ratio of silicon material are 0.1-1.5.
5. require the method for described directional freeze slag making refining purifying polycrystalline silicon according to right 1 or 2, it is characterized in that the polycrystalline silicon material of described adding is piece material or powder.
6. require the method for described directional freeze slag making refining purifying polycrystalline silicon according to right 1 or 2, it is characterized in that described smelting pot can be quartz crucible, plumbago crucible, SiC crucible, MgO crucible and Si 3N 4Crucible.
CN 201110152163 2011-06-08 2011-06-08 Method for purifying polycrystalline silicon by directional solidification and slag refining Expired - Fee Related CN102219221B (en)

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Cited By (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN102530954A (en) * 2012-03-07 2012-07-04 昆明理工大学 Composite refining agent for secondary refining to purify industrial silicon and remove boron
CN102730697A (en) * 2012-06-26 2012-10-17 上海太阳能电池研究与发展中心 System and method for purifying polysilicon through continuous slagging under electric field
CN103043664A (en) * 2012-12-13 2013-04-17 青岛隆盛晶硅科技有限公司 Method and device for directionally solidifying and purifying polysilicon by vacuum extraction of tailing
CN104195638A (en) * 2014-09-01 2014-12-10 大连理工大学 Method for preparing boron master alloy by using metallurgy method
CN104817087A (en) * 2015-05-04 2015-08-05 佳科太阳能硅(龙岩)有限公司 Method of refining silicon with non-graphite crucible on medium-frequency furnace
TWI498282B (en) * 2012-06-25 2015-09-01 Silicor Materials Inc Flux composition useful in directional solidification for purifying silicon and method thereof
CN105063749A (en) * 2015-06-08 2015-11-18 朱超 High-purity polycrystalline silicon preparation method
CN107099841A (en) * 2017-04-24 2017-08-29 武汉理工大学 A kind of method that short route, high efficiency and inexpensive purification prepare polycrystalline silicon used for solar battery
CN107523861A (en) * 2017-08-10 2017-12-29 镇江仁德新能源科技有限公司 A kind of method that impurity is captured in directional solidification process
CN110156024A (en) * 2019-06-14 2019-08-23 宝兴易达光伏刃料有限公司 A method of HIGH-PURITY SILICON is refined by metallic silicon
CN112064113A (en) * 2020-10-22 2020-12-11 新余学院 Polycrystalline silicon ingot furnace convenient to get rid of impurity layer

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CN101323972A (en) * 2008-07-14 2008-12-17 大连理工大学 Polysilicon directional freezing equipment
CN101920960A (en) * 2010-06-29 2010-12-22 华南师范大学 Method for preparing solar grade polysilicon by metallurgy method and polysilicon prepared thereby
CN102040220A (en) * 2009-10-13 2011-05-04 上海太阳能科技有限公司 Manufacturing method of solar-grade polycrystalline silicon

Patent Citations (3)

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Publication number Priority date Publication date Assignee Title
CN101323972A (en) * 2008-07-14 2008-12-17 大连理工大学 Polysilicon directional freezing equipment
CN102040220A (en) * 2009-10-13 2011-05-04 上海太阳能科技有限公司 Manufacturing method of solar-grade polycrystalline silicon
CN101920960A (en) * 2010-06-29 2010-12-22 华南师范大学 Method for preparing solar grade polysilicon by metallurgy method and polysilicon prepared thereby

Cited By (15)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN102530954B (en) * 2012-03-07 2015-05-20 昆明理工大学 Composite refining agent for secondary refining to purify industrial silicon and remove boron
CN102530954A (en) * 2012-03-07 2012-07-04 昆明理工大学 Composite refining agent for secondary refining to purify industrial silicon and remove boron
US9512008B2 (en) 2012-06-25 2016-12-06 Silicor Materials, Inc. Flux composition useful in directional solidification for purifying silicon
TWI498282B (en) * 2012-06-25 2015-09-01 Silicor Materials Inc Flux composition useful in directional solidification for purifying silicon and method thereof
CN102730697A (en) * 2012-06-26 2012-10-17 上海太阳能电池研究与发展中心 System and method for purifying polysilicon through continuous slagging under electric field
CN103043664B (en) * 2012-12-13 2014-08-27 青岛隆盛晶硅科技有限公司 Method and device for directionally solidifying and purifying polysilicon by vacuum extraction of tailing
CN103043664A (en) * 2012-12-13 2013-04-17 青岛隆盛晶硅科技有限公司 Method and device for directionally solidifying and purifying polysilicon by vacuum extraction of tailing
CN104195638A (en) * 2014-09-01 2014-12-10 大连理工大学 Method for preparing boron master alloy by using metallurgy method
CN104817087A (en) * 2015-05-04 2015-08-05 佳科太阳能硅(龙岩)有限公司 Method of refining silicon with non-graphite crucible on medium-frequency furnace
CN105063749A (en) * 2015-06-08 2015-11-18 朱超 High-purity polycrystalline silicon preparation method
CN105063749B (en) * 2015-06-08 2017-07-18 朱超 A kind of method for preparing high-purity polycrystalline silicon
CN107099841A (en) * 2017-04-24 2017-08-29 武汉理工大学 A kind of method that short route, high efficiency and inexpensive purification prepare polycrystalline silicon used for solar battery
CN107523861A (en) * 2017-08-10 2017-12-29 镇江仁德新能源科技有限公司 A kind of method that impurity is captured in directional solidification process
CN110156024A (en) * 2019-06-14 2019-08-23 宝兴易达光伏刃料有限公司 A method of HIGH-PURITY SILICON is refined by metallic silicon
CN112064113A (en) * 2020-10-22 2020-12-11 新余学院 Polycrystalline silicon ingot furnace convenient to get rid of impurity layer

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