CN100372762C - Method for preparing solar grade polysilicon - Google Patents
Method for preparing solar grade polysilicon Download PDFInfo
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- CN100372762C CN100372762C CNB2006100106548A CN200610010654A CN100372762C CN 100372762 C CN100372762 C CN 100372762C CN B2006100106548 A CNB2006100106548 A CN B2006100106548A CN 200610010654 A CN200610010654 A CN 200610010654A CN 100372762 C CN100372762 C CN 100372762C
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- 238000000034 method Methods 0.000 title claims abstract description 24
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- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 claims description 114
- 239000000377 silicon dioxide Substances 0.000 claims description 56
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- PYRZPBDTPRQYKG-UHFFFAOYSA-N cyclopentene-1-carboxylic acid Chemical compound OC(=O)C1=CCCC1 PYRZPBDTPRQYKG-UHFFFAOYSA-N 0.000 abstract 1
- 238000007598 dipping method Methods 0.000 abstract 1
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- 238000005516 engineering process Methods 0.000 description 9
- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 description 8
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- 239000010936 titanium Substances 0.000 description 7
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- 229910052791 calcium Inorganic materials 0.000 description 5
- OAICVXFJPJFONN-UHFFFAOYSA-N Phosphorus Chemical compound [P] OAICVXFJPJFONN-UHFFFAOYSA-N 0.000 description 4
- 229910052759 nickel Inorganic materials 0.000 description 4
- 238000011160 research Methods 0.000 description 4
- ZAMOUSCENKQFHK-UHFFFAOYSA-N Chlorine atom Chemical compound [Cl] ZAMOUSCENKQFHK-UHFFFAOYSA-N 0.000 description 3
- 238000005660 chlorination reaction Methods 0.000 description 3
- 239000000460 chlorine Substances 0.000 description 3
- 229910052801 chlorine Inorganic materials 0.000 description 3
- 150000001875 compounds Chemical class 0.000 description 3
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- 239000000203 mixture Substances 0.000 description 3
- 229910052698 phosphorus Inorganic materials 0.000 description 3
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- 229910000551 Silumin Inorganic materials 0.000 description 2
- 238000006243 chemical reaction Methods 0.000 description 2
- SLLGVCUQYRMELA-UHFFFAOYSA-N chlorosilicon Chemical compound Cl[Si] SLLGVCUQYRMELA-UHFFFAOYSA-N 0.000 description 2
- 238000001035 drying Methods 0.000 description 2
- BHEPBYXIRTUNPN-UHFFFAOYSA-N hydridophosphorus(.) (triplet) Chemical compound [PH] BHEPBYXIRTUNPN-UHFFFAOYSA-N 0.000 description 2
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- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 1
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Abstract
The present invention relates to a method for preparing solar-grade polycrystalline silicon. Metallurgical-grade silicon is adopted as raw material, and can be formed into silicon powder material of which the grain size is more than 50 mesh after ground and broken; the silicon powder material can separately carry out acid dipping treatment with Hydrochloric acid of which the concentration is from 1 to 6 mol/l, nitric acid of which the concentration is from 0.5 to 6 mol/l, and Hydrofluoric acid of which the concentration is from 1 to 5 mol/l, the silicon powder material after dipped by acid is added to a vacuum furnace to carry out vacuum refining treatment which can be divided into two stages, a first stage is vacuum oxidation refinement, the temperature in the furnace can be controlled from 1430 DEG C to 1500 DEG C, and the vacuum degree is from 90000 to 1000 Pa. A second stage is a vacuum distillation refining and vacuum degassing stage, the vacuum degree of the furnace can be controlled from 10-2 to 10-5 Pa, and the temperature is from 1430 DEG C to 1500 DEG C; finally, a solar-grade polycrystalline product can be obtained through directional solidification and top crop treatment. The purity of silicon is more than 99.9999 percent, and the specific resistivity is over 0.4 omega. Cm so that requirements of required silicon raw material in solar cell industry can be met.
Description
One, technical field: belong to the technology that the vacuum metallurgy legal system is equipped with solar energy level silicon.
Two, background technology: the polysilicon that China produces all is to adopt external chlorination purification techniques, and this technology is that metallurgical grade silicon and anhydrous hydrogen chloride are reacted generation SiHCl
3, adopt distillation to purify then and obtain purer SiHCl
3, under 1100 ℃ of temperature condition, use high-purity hydrogen to reduce again, obtain polycrystalline silicon material.Owing to be subjected to blockade on new techniques abroad, the state of the art of China is very low at present, and annual production has only about 60 tons.This production technology is not only invested greatly, production cost is high, and production process needs chlorine, poor stability, on the other hand, silicon material for solar cells mainly comes from the waste material and the substandard products of semi-conductor industry, occurred the raw material supply problem of shortage, and it is too high and to reduce potentiality little directly to use existing chlorination refining process to produce the solar energy level silicon cost.Some experts novel method that solar energy level silicon is produced that begun one's study.
The United States Patent (USP) silicon method of refining (patent No. 5788945 of application such as Anders Schei, authorization date on August 4th, 1998), this invention at raw material be some waste materials that semicon industry produces because its boron-containing impurities is higher, can not satisfy the requirement of solar cell silicon.Therefore the summary of the invention of this patent is for to remove some impurity in the silicon by molten silicon slag making technology, particularly at boron impurities to remove effect better.
Kazuki professor Morita of Japan etc. publishes thesis " solar energy level silicon refining heat mechanics " (2003 on " intermetallics " magazine, 11:1111-1117), this paper utilizes phasor and crystalline phase theory to study silicon purified thermodynamic process from principle, the thermodynamic relation between some impurity and silicon particularly is for the preparation of HIGH-PURITY SILICON provides some theoretical foundations.
The applicant's Marvin's can wait to have studied and utilize useless optical fiber to be the research of feedstock production solar energy level silicon novel process (Chinese rare-earth journal, supplementary issue in 2004: 607-610).This research mainly utilizes high-purity silicon dioxide to be raw material, adopts high temperature hydrogen-argon thermal plasma that silicon-dioxide is reduced, and under the argon shield condition silicon for preparing is separated with unreacted silicon-dioxide then, obtains solar energy level silicon.
The strong grade of the Ji Chuan of Tokyo Univ Japan utilizes Si-Al alloy liquation characteristics to propose to prepare the solar energy level silicon novel process with the metallurgical grade silicon for raw material low temperature, and the physical and chemical process of this process carried out more deep research (Tokyo Univ Japan's doctorate paper, 2005), but aluminum content is higher in the silicon that obtains at present, also need further be optimized research.
For the health that realizes solar cell industry develops rapidly, composition and performance characteristics according to industrial silicon, the application carries the people and has gone out a kind of low-cost solar-grade silicon technology of preparing that does not rely on existing semiconductor grade silicon production technology, this technology not only has characteristics such as less investment, manufacturing cost be low, and process does not need chlorine, environmental pollution is little, belongs to clearer production technology.
Three, summary of the invention:
The purpose of this invention is to provide a kind of method of making each solar-grade polysilicon, adopt metallurgical grade silicon as raw material, through acidleach, add in the vacuum oven and carry out vacuum refinement, obtain the solar-grade polysilicon product, the purity of its silicon is more than 99.9999%, surpasses 0.4 Ω cm than resistance, to satisfy the required silicon raw material of solar cell industry.
The present invention finishes according to the following steps.
1, broken mill: with metallurgical grade silicon as raw material, being ground to granularity earlier is the 20-150 order, and the iron contamination that adopts magnet will grind in the silica flour of back then reduces, and then powder classification is sieved, obtain the above silica flour material of 50 orders and be for further processing, the following silica flour of 50 orders can be used as product and sells;
2, acidleach:
1), the silica flour material behind the broken mill is that the hydrochloric acid of 1-6mol/l carries out acidleach and handles with concentration earlier, extraction temperature 40-80 ℃, extraction time is 0.5-2 days, with distilled water cleaning 2-5 time, vacuum filtration separates silica flour with leach liquor more then;
2), be 0.5-6mol/l with isolated silica flour material concentration of nitric acid, temperature 40-80 ℃, secondary leached 0.5-2 days, carrying out the vacuum filtration separation after using distilled water to clean 2-5 time then separates silica flour with leach liquor; This process is mainly removed impurity iron, aluminium, nickel and titanium etc., and wherein impurity iron can be removed 30%-90%, and impurity aluminum can be removed 40%-95%, and impurity nickel can be removed 20-40%, and the impurity titanium can be removed 35-80%.For improving the acidleach process reaction speed of hydrochloric acid and nitric acid, extraction temperature remains on 40-80 ℃, to improve speed of reaction, the present invention is for cutting down the consumption of energy, shorten the treatment time, also can use microwave heating or intensified by ultrasonic wave to improve acidleach temperature and shortening treatment time except using conventional electrically heated, power is 300-1000W;
3) adopting concentration again, at last is the hydrofluoric acid of 1-5mol/l, temperature 40-80 ℃, soaks 0.5-1 days; Remove the silicon-dioxide on silica flour material surface and the oxide compound on impurity surface, clean 3-8 final vacuum suction filtration with distilled water then, the silica flour material is separated with leach liquor, silica flour feed purity after the processing can reach 99.9-99.99%, infusion solution and lime are neutralized, require to handle discharging according to local environment;
3, the silica flour material after the acidleach processing is carried out vacuum-drying, drying temperature is 80-120 ℃, and vacuum tightness is 30000-90000Pa, and be 12-36 hour time of drying, removes the air of moisture and silicon powder surface absorption, makes in the silica flour moisture less than 5%;
4, to carry out vacuum refinement in the adding of the silica flour material after the vacuum-drying vacuum oven charge cask, the vacuum refinement process is divided into two stages, fs is vor refining, utilize induction heating that silica flour is melted, and temperature is 1430-1500 ℃ in the maintenance stove, vacuum tightness is 90000-1000Pa, then with the mixed gas of argon gas and water vapor with flow 5-151/min, pressure is 80000-10000pa, forming plasma body feeds in the vacuum oven, melting 1-8 hour, stir melt by plasma body on the one hand, improve the rate of diffusion of chemical reaction rate and impurity, on the other hand by the water vapor of adding and the boron in the raw material, impurity such as carbon react, this process the content of boron impurities and carbon can be reduced to 0.3ppmw respectively and below the 5ppmw, the gas of adding is taken away by vacuum pump, to guarantee the vacuum tightness requirement of stove; After oxidation refining is finished, close plasma body, vacuum refinement changes subordinate phase over to, i.e. vacuum distilling refining and vacuum outgas stage, this stage keeps stove vacuum tightness 10
-2-10
-5Pa, furnace 1430-1500 ℃, redistillation refining 1-8 hour is on the one hand mainly removed impurity such as phosphorus and the calcium of not removing fully, aluminium, and the content of foreign matter of phosphor can be reduced to below the 0.1ppmw, impurity calcium can reduce 10-50%, impurity aluminum can reduce 10-30%, and is phosphorous higher in the distillment, measures also less, can be used as the phosphorous chemical industry raw material, remove dissolved gases in the silicon melt by vacuum outgas on the other hand;
5, after the vacuum refinement silica flour material melt is carried out directional freeze and handle, this stage keeps stove vacuum tightness 10
-2-10
-5Pa, 1430-1500 ℃ of silica flour material melt portion temperature, speed of cooling is the 0.1-2 mm/min, further remove impurity such as iron that the last stage do not eliminate, aluminium, calcium, titanium, these foreign matter contents all can be reduced to below the 0.1ppmw, simultaneously proceed vacuum outgas in process of cooling, oxygen level is reduced to below the 3ppmw, and the gas that significantly reduces the polycrystalline silicon material forming process is mingled with;
6, treat to carry out the crop processing treatment after the material cooling, excise last cooling segment, obtain solar energy level silicon product and ferrosilicon, silumin, the purity of silicon is more than 99.9999% in the polysilicon product, surpass 0.4 Ω cm than resistance, ferrosilicon, silumin can be used as reductive agent and sell.
Compare the advantage that the present invention has with existing chlorination purification techniques:
1. its initial cost of the less identical production-scale manufacturer of initial cost can reduce 70%;
2. equipment is simple, security is good because the refining process after the wet method reason is finished under the vacuum environment condition, and equipment is simple, and subsystem is few, and safe;
3. its power consumption can reduce more than 50% in the low production process of few, the production cost of power consumption, and production cost can reduce more than 50%;
4. environmental pollution is little because vacuum metallurgy equipment carries out in closed system, do not need chlorine in the production process, so this novel process environmental pollution is little, can realize cleaner production.
Four, description of drawings: Fig. 1 is a process flow sheet of the present invention.
Five, embodiment:
Embodiment one
Use silicone content to be raw material, its major impurity composition Al content 440ppmw, Fe content 1300ppmw, Ca content 320ppmw as the metallurgical grade silicon of 99.5wt%.
Raw material is broken mill, and adopt magnet to remove the iron contamination of bringing in the broken mechanical milling process, sieve then, getting silicon particle size is 50-150 purpose silica flour material.
Be that the hydrochloric acid of 2mol/l carries out acidleach to the silica flour material and handles with concentration, in 50-60 ℃ water-bath, leached 1 day, adopt vacuum filtration that acid solution and silica flour material are separated then, and use distilled water to clean 3 times, and then be that the nitric acid of 2mol/l carries out acidleach to the silica flour material and handles with concentration, in 50-60 ℃ water-bath, leached 1 day, adopt vacuum filtration that acid solution and material are separated then, and use distilled water to clean 3 times, solution after acidleach gone out adopts sulfide lime to carry out neutralizing treatment, reach emission request, iron contamination content has reduced by 40% after twice acidleach handled, impurity aluminum content has reduced by 50%, and impurity nickel content has reduced by 30%, and the impurity titanium has removed 45%, it is that the hydrofluoric acid of 3mol/l is handled that silica flour material after treatment re-uses concentration, treatment time is 12 hours, the silicon-dioxide of particle surface and the oxide compound on impurity surface all can be removed, and be used distilled water to clean 5 times.Silicon powder delivery purity after the processing is 99.95%;
With the silica flour after the acidleach under 80000Pa vacuum condition and 100 ℃ of temperature dry 24 hours, water content is 3% in the silica flour material, and will carry out refining in the dried material adding vacuum oven, container is a plumbago crucible, utilize induction heating that temperature of charge is elevated to 1450-1500 ℃, stove vacuum tightness is 80000Pa, feeding content then is the argon plasma of the 1-15wt% water vapor of mixed gas total amount, argon flow amount is 101/min, pressure is 90000Pa, and melting is 4 hours under this condition, closes plasma body then, the vacuum tightness of rising stove, keeping stove vacuum tightness is 0.001Pa, and furnace still maintains 1450-1500 ℃, and is incubated 6 hours, carrying out vacuum outgas simultaneously handles, carry out directional freeze at last and handle, stove pressure is 0.001Pa, and the temperature of silicon melt part still maintains 1450-1500 ℃, rate of cooling is 0.8 mm/min, treats after stove drops to room temperature condensed silicon to be carried out the crop processing.
Silicon after treatment, its purity is 99.99996%, wherein all below 0.1ppmw, phosphorus content is 0.08ppmw to the content of impurity such as iron, aluminium, calcium, titanium, the content of boron is 0.15ppmw, carbon content is below 0.5ppmw, the ratio resistance of material is 0.6 Ω cm.
Embodiment two
Use silicone content to be raw material, its major impurity composition Al content 520ppmw, Fe content 1800ppmw, Ca content 380ppmw as the metallurgical grade silicon of 98wt%.
Raw material is broken mill, and adopt magnet to remove the iron contamination of bringing in the broken mechanical milling process, sieve then, getting the silica flour raw meal particle size is the 50-150 order.
Be that the hydrochloric acid of 2.5mol/l carries out acidleach to the silica flour material and handles with concentration, under microwave condition, handled 10 minutes, microwave power is 500W, in 60 ℃ water-bath, leached 1 day then, adopt vacuum filtration that acid solution and material are separated then, and use distilled water to clean 3 times, and then be that the nitric acid of 3.5mol/l carries out acidleach to the silica flour material and handles with concentration, handled 10 minutes under the ultrasonic wave condition, ultrasonic power is 500W, leaches 1 day in 50 ℃ water-bath then, adopt vacuum filtration that acid solution and silica flour material are separated then, and using distilled water to clean 3 times, the solution after acidleach is gone out adopts sulfide lime to carry out neutralizing treatment, reaches emission request.Iron contamination content has reduced by 50% after twice acidleach handled, and impurity aluminum content has reduced by 55%, and impurity nickel content has reduced by 36%, and the impurity titanium has removed 48%.It is that the hydrofluoric acid of 3mol/l is handled that silicon materials after treatment re-uses concentration, and the treatment time is 12 hours, the silicon-dioxide on silica flour material surface and the oxide compound on impurity surface all can be removed, and be used distilled water to clean 5 times.Silica flour purity after the processing is 99.98%.
With the silica flour material after handling under 80000Pa vacuum condition and 120 ℃ of temperature dry 20 hours, water content was 2% in the silica flour.And will carry out refining in the dried material adding vacuum oven, charge cask is a quartz crucible, utilize induction heating that temperature of charge is elevated to 1450-1500 ℃, stove vacuum tightness is 80000Pa, feed the argon plasma that contains the 1-15wt% water vapor then, argon flow amount is 101/min, pressure is 90000Pa, and refining is 6 hours under this condition, closes plasma body then, the vacuum tightness of rising stove, keeping stove vacuum tightness is 0.0001Pa, and furnace still maintains 1450-1500 ℃, and is incubated 8 hours, carrying out vacuum outgas simultaneously handles, carry out directional freeze at last and handle, stove pressure is 0.0001Pa, and the temperature of silica flour material melt part still maintains 1450-1500 ℃, rate of cooling is 0.2 mm/min, treats after stove drops to room temperature condensed silicon to be carried out the crop processing.
Silicon after treatment, its purity is 99.99993%, wherein all below 0.1ppmw, phosphorus content is 0.06ppmw to the content of impurity such as iron, aluminium, calcium, titanium, the content of boron is 0.1ppmw, carbon content is below 0.2ppmw, the ratio resistance of material is 0.8 Ω cm.
Claims (2)
1. method for preparing solar-grade polysilicon, it is characterized in that: it is finished according to the following steps,
(1), broken mill: use silicone content to be 99.5wt%, Al content 440ppmw, Fe content 1300ppmw, the metallurgical grade silicon of Ca content 320ppmw is that raw material breaks mill, and adopt magnet to remove the iron contamination of bringing in the broken mechanical milling process, sieve then, getting silicon particle size is 50-150 purpose silica flour material;
(2), acidleach: be that the hydrochloric acid of 2mol/l carries out acidleach to the silica flour material and handles with concentration, in 50-60 ℃ water-bath, leached 1 day, adopt vacuum filtration that acid solution and silica flour material are separated then, and use distilled water to clean 3 times, and then be that the nitric acid of 2mol/l carries out acidleach to the silica flour material and handles with concentration, in 50-60 ℃ water-bath, leached 1 day, adopt vacuum filtration that acid solution and silica flour material are separated again, and use distilled water to clean 3 times, solution after acidleach gone out adopts sulfide lime to carry out neutralizing treatment, reach emission request, silica flour material after treatment re-uses the hydrofluoric acid treatment 12 hours that concentration is 3mol/l, and use distilled water to clean 5 times, obtain powder purity and be 99.95% silica flour;
(3), with silica flour under 80000Pa vacuum condition and 100 ℃ of temperature dry 24 hours, at this moment water content is 3% in the silica flour;
(4), carry out refining in the dried material adding vacuum oven, container is a plumbago crucible, utilize induction heating that temperature of charge is elevated to 1450-1500 ℃, stove vacuum tightness is 80000Pa, feeding content then is the argon plasma of the 1-15wt% water vapor of mixed gas total amount, argon flow amount is 10l/min, and pressure is 90000Pa, and melting is 4 hours under this condition, close plasma body then, the vacuum tightness of rising stove, keeping stove vacuum tightness is 0.001Pa, furnace still is 1450-1500 ℃, and be incubated 6 hours, carry out vacuum outgas simultaneously and handle, carry out directional freeze at last and handle, stove pressure is 0.001Pa, the temperature of silicon melt part still maintains 1450-1500 ℃, rate of cooling 0.8 mm/min is treated after stove drops to room temperature condensed silicon to be carried out the crop processing, obtains the solar-grade polysilicon product.
2. method for preparing solar-grade polysilicon, it is characterized in that: it is finished according to the following steps,
(1), broken mill: use silicone content to be 98wt%, Al content 520ppmw, Fe content 1800ppmw, the metallurgical grade silicon of Ca content 380ppmw is that raw material breaks mill, and adopt magnet to remove the iron contamination of bringing in the broken mechanical milling process, sieve then, getting silicon particle size is 50-150 purpose silica flour material;
(2), acidleach: be that the hydrochloric acid of 2.5mol/l carries out acidleach to the silica flour material and handles with concentration, under microwave condition, handled 10 minutes earlier, microwave power is 500W, in 60 ℃ water-bath, leached 1 day then, adopt vacuum filtration that acid solution and silica flour material are separated again, and use distilled water to clean 3 times, and then be that the nitric acid of 3.5mol/l carries out acidleach to the silica flour material and handles with concentration, under the ultrasonic wave condition, handled 10 minutes, ultrasonic power is 500W, in 50 ℃ water-bath, leach then and adopt vacuum filtration that acid solution and silica flour material are separated after 1 day, and use distilled water to clean 3 times, solution after acidleach gone out adopts sulfide lime to carry out neutralizing treatment, reach emission request, it is that the hydrofluoric acid of 3mol/l carries out immersion treatment and used distilled water to clean in 12 hours 5 times that silicon materials after treatment re-uses concentration, obtains powder purity and be 99.98% silica flour;
(3), with silica flour under 80000Pa vacuum condition and 120 ℃ of temperature dry 20 hours, water content is 2% in this moment silica flour;
(4), to carry out refining in the dried material adding vacuum oven, charge cask is a quartz crucible, utilize induction heating that temperature of charge is elevated to 1450-1500 ℃, stove vacuum tightness is 80000Pa, feed the argon plasma that contains the 1-15wt% water vapor then, argon flow amount is 10l/min, pressure is 90000Pa, and plasma body is closed in refining 6 hours then, rising stove vacuum tightness is 0.0001Pa, furnace still maintains 1450-1500 ℃, and is incubated 8 hours, carries out vacuum outgas simultaneously and handles, carrying out directional freeze at last handles, stove pressure is 0.0001Pa, and the temperature of silica flour material melt part still maintains 1450-1500 ℃, and rate of cooling is 0.2 mm/min, treat after stove drops to room temperature condensed silicon to be carried out the crop processing, obtain the solar-grade polysilicon product.
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