CN102020278A - Method for removing impurity phosphorus in silicon - Google Patents
Method for removing impurity phosphorus in silicon Download PDFInfo
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- CN102020278A CN102020278A CN2009101027814A CN200910102781A CN102020278A CN 102020278 A CN102020278 A CN 102020278A CN 2009101027814 A CN2009101027814 A CN 2009101027814A CN 200910102781 A CN200910102781 A CN 200910102781A CN 102020278 A CN102020278 A CN 102020278A
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Abstract
The invention relates to a method for removing impurity phosphorus in silicon, belonging to the technical field of physical metallurgical silicon purification. The method for removing impurity phosphorus in silicon is characterized by adopting a vacuum induction furnace, using a calcium-containing alloy or a calcium compound with strong reducibility as a dephosphorization agent and using a calcium halide as a fluxing agent to carry out a dephosphorization reaction in the melted state of silicon under the protection of an inert gas argon. The operation process comprises the following steps of: proportionally compounding the industrial silicon material, the dephosphorization agent and the fluxing agent, mixing evenly, putting the mixture in a crucible and putting the crucible in an airtight vacuum induction heating furnace; vacuumizing the furnace, keeping the heating furnace at tiny negative pressure, stopping vacuumizing and filling the heating furnace with argon so as to keep pressure inside and outside the furnace constant; carrying out induction heating and keeping for 20-30 min when the temperature inside the furnace reaches 1,450-1,600 DEG C; slowly and naturally cooling to a room temperature after dephosphorization is finished; and soaking and treating a silicon block in dilute hydrochloric acid for 2-4 h to remove impurities. The silicon block subjected to dephosphorization treatment contains the phosphorus of less than 2 ppm and can be used as a silicon raw material for solar cells after boron and metal impurities are removed from the silicon block.
Description
Technical field: the invention belongs to the technical field of physical metallurgy technology purified silicon, particularly under protection of inert gas, add with silicon in the impurity reactive material, phosphorus in the silicon is removed made in the silicon phosphorus content effectively less than the method for 2ppm.
Technical background: in recent years, because the anxiety of the energy becomes the solar cell of electric energy to obtain paying close attention to widely solar energy converting.HIGH-PURITY SILICON is the main raw material of preparation solar cell, because the core technology of purified silicon monopolize by external seven large manufacturers, it is 8-10 times of traditional thermal power generation that the costliness of silicon price causes cost for solar power generation again.Therefore, seek a kind of purified silicon cost techniques that can reduce and become the focus that people pay close attention to, study.
At present, the proven technique of production HIGH-PURITY SILICON mainly is the improvement Siemens Method, and this method weak point is that it has taked the thermal chemical vapor deposition that falls behind on the core link of flow process, the link of technical process is too much, one time transformation efficiency is low, causes the flow process time oversize, and energy consumption is too high.Therefore, having occurred is the metallurgy method technology of characteristics with the low cost, in numerous novel procesies, utilizes the segregation coefficient difference of metallic impurity elements in the silicon to carry out the mode of directional freeze, has characteristics such as energy consumption is low, environmental pollution is little.But this simple directional solidification process can't be removed the bigger foreign matter of phosphor of segregation coefficient, and in numerous impurity of silicon, phosphorus is deleterious impurity, has directly influenced the resistivity and the minority carrier lifetime of silicon materials, and then has influenced the photoelectric transformation efficiency of solar cell.
For the removal of phosphorus, because its saturation vapour pressure at high temperature is far longer than silicon, the therefore method by vacuum melting, under certain high vacuum, the phosphorus volatilization is entered in the gas phase, use high-vacuum apparatus and extract evaporable foreign gas in the silicon melt out, reach the purpose of removing impurity.Publication number CN101318655A, denomination of invention is a kind of method and device of removing foreign matter of phosphor in the silicon, and this method adopts the dephosphorization of twin-cathode ray beam refining purification techniques below high vacuum 10-3pa, realized working continuously, sample is in a small amount well removed the phosphorus effect.This method exists deficiency to be, produce so high vacuum condition, and facility investment is relatively large, the energy consumption height, and high-vacuum apparatus is difficult for being amplified to the suitability for industrialized production level of extensiveization.In addition, people such as Japanese Takeshi Yoshikawa have studied in the sial melt in the 1173-1373K temperature range, remove phosphorus with the method for directional freeze.Because under relative low temperature, phosphorus and aluminium have strong avidity, also effectively dephosphorization.But new impurity has been brought in the adding of aluminium again into, how effectively to remove the key that aluminium impurity is present method.The people such as TOMOHITO of Japan from thermodynamic study under 1732K the character of fused silicon and phosphorus effect, the interpolation that draws calcium metal is beneficial to and reduces the segregation coefficient of phosphorus in silicon, the calcium phosphide that forms is deposited near the second phase calcium silicide, utilize the method for pickling can the flush away calcium phosphide, the calcium addition is 5.7% o'clock, and the clearance of phosphorus reaches 80%.Publication number CN101302013A, denomination of invention is a kind of preparation method of low-phosphorus solar-grade silicon, employing is being carried out high melt by Pure Silicon Metal and calcium metal under the high-purity argon gas environment in flowability under 1400 ℃ of-1600 ℃ of high temperature, phosphorus partial gasification in the Pure Silicon Metal is taken away with the mobile argon gas, phosphorus can generate calcium phosphide with the calcium metal reaction simultaneously, by wet purification, the calcium phosphide of generation and metallic impurity are dissolved in the different mineral acids at last, thereby reach the purpose of purification.This invention, can drop to phosphorus content in the 5g silicon below the 2PPM from 12PPM in conjunction with wet purification by high melt.Because calcium metal is very active metal, have very strong reductibility, in the environment of aerobic, be easy to oxidation, high temperature is volatile, how to prevent at high temperature volatilization of calcium and not oxidized, will influence the utilization ratio of calcium.
Summary of the invention: the objective of the invention is to overcome the deficiency of aforesaid method, provide a kind of industrialization be easy to realize, low-cost, remove the method for phosphorus in the silicon efficiently, through after the invention process, phosphorus content is less than 2ppm in the product silicon.
Know-why of the invention process:
Phosphorus belongs to V group element in the periodic table of elements, the outermost layer of phosphorus atom has 5 valence electrons, and it can lose 5 valence electrons fully and become positive 5 valencys, also can obtain 3 electronics and become negative 3 valencys.Because the avidity of silicon and oxygen is greater than the avidity of phosphorus and oxygen, silicon is easy to oxidation, and it is infeasible that the employing oxidation style removes in the silicon phosphorus.And there is not the oxidized problem of silicon in dephosphorization under reducing atmosphere, under reducing atmosphere, adds in strong reducible agent and the silicon phosphorus formation phosphide and changes slag over to and be removed and be considered to feasible.
The boiling point of calcium metal is 1483 ℃ under 1 normal atmosphere, if be higher than this temperature, calcium will exist with gaseous state, and pass silicon melt with high speed, and therefore the chance that high speed calcium steam flow and phosphorus meet seldom greatly reduces dephosphorization effect.For the dephosphorization effect that improves calcium metal must manage to reduce the vapour pressure of calcium, promptly under the prerequisite that dephosphorisation reaction carries out smoothly, improve furnace atmosphere pressure and can significantly improve dephosphorization effect.In experiment, we find, in calcium containing alloy, the vapour pressure of calcium is reduced, and therefore, the excellent calcium alloy of using of the present invention is as dephosphorizing agent, calcium alloy comprises CaAl, CaSi, CaSiAl, CaSiMg, CaMg, but is not limited thereto, also other calcareous reducing substances such as CaC
2
Because Calcium Fluoride (Fluorspan) not only can reduce the activity of calcium phosphide, well absorbs the dephosphorization product, thereby promote the carrying out of dephosphorisation reaction, and because the fusing point of himself is lower, easy and other composition forms low melting component, and the dephosphorizing agent of adding is melted rapidly, increaseization slag speed is impelled CaC
2Decomposition, thereby accelerate dephosphorization speed, therefore, preferred fluorinated calcium of the present invention is as fusing assistant, also other halogenide of calcium.
The invention provides a kind of method of removing foreign matter of phosphor in the silicon, be included in dephosphorization under reducing atmosphere and the wet method pickling carried out under the protection of inert gas, it is characterized in that adopting vacuum induction furnace, under protection of inert gas, comprise CaC with having strong reducible agent
2, CaAl, CaMg be as dephosphorizing agent, the halogenide that adopts chemically pure reagent calcium carries out dephosphorisation reaction as fusing assistant under the silicon molten state, dephosphorisation reaction promptly carries out the wet method pickling after finishing.
Its operation steps is successively: 1. industrial silicon material, dephosphorizing agent, fusing assistant are prepared in proportion, mixing is contained in the crucible, and crucible is placed the enclosed vacuum induction heater; 2. extract furnace air out, make process furnace keep little negative pressure, stop to vacuumize, in process furnace, fill argon gas, make stove inner and outer air pressure unanimity; 3. induction heating when temperature in the stove reaches 1450 ℃-1600 ℃, is kept 20-30min; Dephosphorization slowly naturally cools to room temperature after finishing; 4. immersion treatment silico briquette 2-4 hour under dilute hydrochloric acid is removed the phosphide and the metallic impurity that are soluble in acid.Through the silico briquette after the dephosphorization treatment, phosphorus content is less than 2ppm.
In a kind of method of removing foreign matter of phosphor in the silicon of the present invention, described vacuum induction furnace carries out melting under the rare gas element argon shield, and the crucible top is in protection of inert gas atmosphere in the stove.
In a kind of method of removing foreign matter of phosphor in the silicon of the present invention, described dephosphorizing agent also comprises CaC
2, among CaAl, CaMg, CaSi, CaSiAl, CaSiMg, the CaMg one or more, preferably CaC
2Or CaAl;
The present invention is a kind of to remove in the method for foreign matter of phosphor in the silicon, and described fusing assistant is the halogenide of calcium, wherein preferred fluorinated calcium CaF
2
The present invention is a kind of to remove in the method for foreign matter of phosphor in the silicon, and the mass ratio of described dephosphorizing agent and fusing assistant is 3.5～5: 1, is preferably 4: 1.
The present invention is a kind of to remove in the method for foreign matter of phosphor in the silicon, and dephosphorizing agent and fusing assistant account for the 5-8% of siliceous amount, and preferred 6%.
The present invention is a kind of to remove in the method for foreign matter of phosphor in the silicon, and the silicon raw materials quality that need are purified does not require, and disposable dephosphorization rate is greater than more than 90%.
The present invention is a kind of to remove in the method for foreign matter of phosphor in the silicon, in the described stove temperature range at 1450 ℃-1600 ℃, preferred 1500 ℃.
In a kind of method of removing foreign matter of phosphor in the silicon, described dephosphorization time dimension is held in 20-30min according to the present invention.
In a kind of method of removing foreign matter of phosphor in the silicon, described wet processing is to soak under dilute hydrochloric acid 2-4 hour according to the present invention, and the mass concentration of hydrochloric acid is in the 10-20% scope.
The present invention has not only removed the phosphorus in the silicon in the wet processing process of dephosphorization under reducing atmosphere, also removed most of metallic impurity.
Effect of the present invention: technological process of the present invention is simple, the vacuum melting furnace equipment and technology maturation of dephosphorization, and investment in fixed assets is less relatively; Adopt the method for slag making, carry out under normal pressure, easy handling is easy to large-scale industrialization and implements; Adopt rational fusing assistant, improved the dephosphorizing agent utilization ratio greatly, and effectively removed the impurity element phosphorus in the silicon.Do not use high vacuum, do not use electron beam, thereby reduced energy consumption, reduced the silicon cost for purification.The product phosphorus content that obtains is less than 2ppm.
Embodiment:
Specific embodiment 1:
A kind of method of removing foreign matter of phosphor in the silicon, its operation steps is:
1, will contain in the crucible immediately behind 50kg industrial silicon, 2.4kg carbide of calcium, the 0.6kg analytically pure calcium fluoride mixing, and crucible is placed the enclosed vacuum induction heater, wherein feed metal silicon granularity be 10 orders;
2, extract furnace air out with vacuum pump, make the process furnace 9000pa that keep-ups pressure, stop to bleed, in process furnace, fill argon gas, the stove inner and outer air pressure is maintained under the normal pressure;
3, stove is carried out electromagnetic induction heating, when temperature in the stove reaches 1500 ℃, keep reaction dephosphorization time 25min;
4, after dephosphorization finishes, stop heating, silicon melt is slowly naturally cooled to room temperature;
5, be immersion treatment silico briquette 3 hours under 15% the dilute hydrochloric acid in mass concentration, then by centrifuging, with the silica flour washing to neutral oven dry, sampling analysis.Table 1 is listed in the quality contrast before and after the dephosphorization.
Specific embodiment 2:
In order to illustrate the influence of dephosphorizing agent to dephosphorization, carry out in the mode of similar embodiment 1, change dephosphorizing agent into calcium metal, other condition is constant, and experimental result is listed in table 1.
Specific embodiment 3:
A kind of method of removing foreign matter of phosphor in the silicon, its operation steps is:
1, will contain in the crucible immediately behind 50kg industrial silicon, 2.5kg carbide of calcium, the 0.5kg analytically pure calcium fluoride mixing, and crucible is placed the enclosed vacuum induction heater, wherein feed metal silicon granularity be 10 orders;
2, extract furnace air out with vacuum pump, make the process furnace 10000pa that keep-ups pressure, stop to bleed, in process furnace, fill argon gas, the stove inner and outer air pressure is maintained under the normal pressure;
3, stove is carried out electromagnetic induction heating, when temperature in the stove reaches 1450 ℃, keep reaction dephosphorization time 30min;
4, after dephosphorization finishes, stop heating, silicon melt is slowly naturally cooled to room temperature;
5, be immersion treatment silico briquette 3 hours under 18% the dilute hydrochloric acid in mass concentration, then by centrifuging, with the silica flour washing to neutral oven dry, sampling analysis.Table 1 is listed in the quality contrast before and after the dephosphorization.
Specific embodiment 4:
A kind of method of removing foreign matter of phosphor in the silicon, its operation steps is:
1, will contain in the crucible immediately behind 50kg industrial silicon, 2kg silicocalcium CaSi, the 0.5kg analytically pure calcium fluoride mixing, and crucible is placed the enclosed vacuum induction heater, wherein feed metal silicon granularity be 10 orders;
2, extract furnace air out with vacuum pump, make the process furnace 10000pa that keep-ups pressure, stop to bleed, in process furnace, fill argon gas, the stove inner and outer air pressure is maintained under the normal pressure;
3, stove is carried out electromagnetic induction heating, when temperature in the stove reaches 1450 ℃, keep reaction dephosphorization time 30min;
4, after dephosphorization finishes, stop heating, silicon melt is slowly naturally cooled to room temperature;
5, be immersion treatment silico briquette 3 hours under 18% the dilute hydrochloric acid in mass concentration, then by centrifuging, with the silica flour washing to neutral oven dry, sampling analysis.Table 1 is listed in the quality contrast before and after the dephosphorization.
Specific embodiment 5:
A kind of method of removing foreign matter of phosphor in the silicon, its operation steps is:
1, will contain in the crucible immediately behind 50kg industrial silicon, 2kg silumin, the 0.5kg analytically pure calcium fluoride mixing, and crucible is placed the enclosed vacuum induction heater, wherein feed metal silicon granularity be 10 orders;
2, extract furnace air out with vacuum pump, make the process furnace 10000pa that keep-ups pressure, stop to bleed, in process furnace, fill argon gas, the stove inner and outer air pressure is maintained under the normal pressure;
3, stove is carried out electromagnetic induction heating, when temperature in the stove reaches 1450 ℃, keep reaction dephosphorization time 30min;
4, after dephosphorization finishes, stop heating, silicon melt is slowly naturally cooled to room temperature;
5, be immersion treatment silico briquette 3 hours under 18% the dilute hydrochloric acid in mass concentration, then by centrifuging, with the silica flour washing to neutral oven dry, sampling analysis.Table 1 is listed in the quality contrast before and after the dephosphorization.
Quality contrast unit: ppm before and after table 1 dephosphorization
| Sequence number Fe Al Ca P |
| Dephosphorization preceding 4,752 3,400 280 33 |
| Embodiment 1 300 210 50 0.8 |
| Embodiment 2 320 208 48 3.5 |
| Embodiment 3 310 200 45 1.2 |
| Embodiment 4 300 210 48 0.8 |
| Embodiment 5 304 198 42 1.6 |
As can be seen from Table 1, embodiment 1 dephosphorization effect is best, and as dephosphorizing agent, because calcium exists with gaseous state under 1500 ℃, gasiform calcium leaves silicon face with calcium metal for embodiment 2, reduced with silicon melt in the phosphorus chance of meeting, therefore greatly reduce dephosphorization effect.Embodiment 3 adopts at a lower temperature, and the dephosphorization time increases, and also can reach good dephosphorization effect.Embodiment 4 adopts silicocalcium to make dephosphorizing agent, and Comparative Examples 3 dephosphorization effects are more or less the same.
Below in conjunction with the embodiments the present invention detailed explanation and explanation have been carried out, but those skilled in the art understand, do not breaking away from the spirit and scope of the invention, any change, improvement, variant and the equivalent of the embodiment of the invention is all in the scope of the invention of claims definition.
Claims (10)
1. method of removing foreign matter of phosphor in the silicon; be included in dephosphorization under reducing atmosphere and the wet method pickling carried out under the protection of inert gas; it is characterized in that adopting vacuum induction furnace; under protection of inert gas; comprise that with having strong reducible agent CaC2, CaAl, CaSi are as dephosphorizing agent; the halogenide that adopts chemically pure reagent calcium carries out dephosphorisation reaction as fusing assistant under the silicon molten state, dephosphorisation reaction promptly carries out the wet method pickling after finishing.
2. the crucible top is in argon shield in a kind of method of removing foreign matter of phosphor in the silicon according to claim 1, wherein said vacuum induction furnace stove.
3. a kind of method of removing foreign matter of phosphor in the silicon according to claim 1, wherein said have strong reducible agent and also comprise CaC
2, among CaAl, CaMg, CaSi, CaSiAl, the CaSiMg one or more, preferably CaC
2Or CaSi.
4. a kind of method of removing foreign matter of phosphor in the silicon according to claim 1, wherein said fusing assistant is Calcium Fluoride (Fluorspan) preferably.
5. a kind of method of removing foreign matter of phosphor in the silicon according to claim 1, the mass ratio 3.5～5: 1 of wherein said dephosphorizing agent and fusing assistant is preferably 4: 1.
6. a kind of method of removing foreign matter of phosphor in the silicon according to claim 1 wherein adds the 5-8% that dephosphorizing agent in the silicon and fusing assistant account for siliceous amount altogether, preferred 6%.
7. according to the described a kind of method of removing foreign matter of phosphor in the silicon of one of claim 1～6, its operation steps is successively: 1. industrial silicon material, dephosphorizing agent, fusing assistant are prepared in proportion, mixing is contained in the crucible, and crucible is placed the enclosed vacuum induction heater; 2. extract furnace air out, make process furnace keep little negative pressure, stop to vacuumize, in process furnace, fill argon gas, make stove inner and outer air pressure unanimity; 3. induction heating when temperature in the stove reaches 1450 ℃-1600 ℃, is kept 20-30min; Dephosphorization slowly naturally cools to room temperature after finishing; 4. immersion treatment silico briquette 2-4 hour under dilute hydrochloric acid is removed the phosphide and the metallic impurity that are soluble in acid, and through the silico briquette after the dephosphorization treatment, phosphorus content removes boron again, goes metallic impurity to handle less than 2ppm, can be used as solar cell silicon raw material.
8. a kind of method of removing foreign matter of phosphor in the silicon according to claim 7, in the wherein said stove temperature range at 1450 ℃-1600 ℃, preferred 1500 ℃.
9. according to claim 7 or 2 described a kind of methods of removing foreign matter of phosphor in the silicon, wherein the dephosphorization time dimension is held in 20-30min.
10. a kind of method of removing foreign matter of phosphor in the silicon according to claim 7, wherein said wet processing are to soak under dilute hydrochloric acid 2-4 hour, and the mass concentration of hydrochloric acid is in the 10-20% scope.
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| CN2009101027814A CN102020278A (en) | 2009-09-09 | 2009-09-09 | Method for removing impurity phosphorus in silicon |
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Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103318895A (en) * | 2013-07-05 | 2013-09-25 | 昆明理工大学 | Method for removing impurity phosphorous in silicon |
| CN104512894A (en) * | 2013-09-27 | 2015-04-15 | 东莞市长安东阳光铝业研发有限公司 | Treatment method of silicon block |
| CN104837577A (en) * | 2012-12-10 | 2015-08-12 | 昭和电工株式会社 | Method for producing silicon-containing aluminum alloy ingot |
| CN111792647A (en) * | 2020-07-21 | 2020-10-20 | 昆明理工大学 | Method for smelting silicon wafer cutting waste under micro-negative pressure |
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2009
- 2009-09-09 CN CN2009101027814A patent/CN102020278A/en active Pending
Cited By (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN104837577A (en) * | 2012-12-10 | 2015-08-12 | 昭和电工株式会社 | Method for producing silicon-containing aluminum alloy ingot |
| CN104837577B (en) * | 2012-12-10 | 2016-08-24 | 昭和电工株式会社 | The manufacture method of siliceous aluminium alloy ingot bar |
| CN103318895A (en) * | 2013-07-05 | 2013-09-25 | 昆明理工大学 | Method for removing impurity phosphorous in silicon |
| CN103318895B (en) * | 2013-07-05 | 2016-02-24 | 昆明理工大学 | A kind of method removing foreign matter of phosphor in silicon |
| CN104512894A (en) * | 2013-09-27 | 2015-04-15 | 东莞市长安东阳光铝业研发有限公司 | Treatment method of silicon block |
| CN111792647A (en) * | 2020-07-21 | 2020-10-20 | 昆明理工大学 | Method for smelting silicon wafer cutting waste under micro-negative pressure |
| CN111792647B (en) * | 2020-07-21 | 2021-09-10 | 昆明理工大学 | Method for smelting silicon wafer cutting waste under micro-negative pressure |
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