CN108128779A - A kind of method of carbon, nitrogen impurity in removal polysilicon - Google Patents
A kind of method of carbon, nitrogen impurity in removal polysilicon Download PDFInfo
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- CN108128779A CN108128779A CN201810090948.9A CN201810090948A CN108128779A CN 108128779 A CN108128779 A CN 108128779A CN 201810090948 A CN201810090948 A CN 201810090948A CN 108128779 A CN108128779 A CN 108128779A
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- C01B33/037—Purification
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Abstract
The invention belongs to polycrystalline silicon smelting technical field, more particularly to a kind of method for removing carbon, nitrogen impurity in polysilicon.The present invention builds the melting environment of oxidisability, the carbon dissolved in silicon, nitrogen is made to be combined to form volatile oxidizing gas with oxygen, so as to be removed by the way that during electron-beam smelting, glass sand is added into raw material.Product carbon made from this method, nitrogen impurity removal effect are good, and have the characteristics that at low cost, purification efficiency is high.
Description
Technical field
The invention belongs to polycrystalline silicon smelting technical field, more particularly to a kind of method for removing carbon, nitrogen impurity in polysilicon.
Background technology
Solar-grade polysilicon is the main raw material(s) of photovoltaic industry, with the sustainable development of photovoltaic industry, to polysilicon
The demand of material is growing.China has become the output state of polysilicon maximum and demand state, and largely relies on import, and it is still necessary to expand
Big production scale.However, being reallocated by the impurity in preparation process and melting environment pollutes, the yield of polycrystalline silicon ingot casting
Less than 70%, ingot top region, rich in nitrogen impurity, can not directly be utilized rich in carbon impurity, edge.The part silicon material is carried out
Purification, regains the polycrystalline silicon material of high-purity, realizes the regeneration of silicon materials, economy and social effect are great.
After metallurgy method prepares the ingot casting process of solar-grade polysilicon, the yield of ingot casting is only 70%, top and
The ingot casting region of side nearly 30% has accumulated a large amount of SiC, Si3N4It is mingled with and metal impurities, the purity in these regions is only 3N
(99.9%).By preceding described, metal impurities have extremely effective purification mode at present.But for C, N and its generation is precipitated
SiC, Si3N4Nonmetal inclusion particle, due to the diversity in its source in various techniques, but also studying its distribution and going
Except there are certain difficulty, though achieving certain effect to the control of carbon, nitrogen impurity in traditional handicraft now, still cannot
Meet requirement of the higher quality solar cell to silicon materials, the also extremely difficult recycling of discarded tailing.
Existing method and shortcoming：
1st, it filters
Filtering technique is mainly using ceramic sponge strainer, the polyethylene glycol and oil in divided silicon slurry material at room temperature
Dirt or the at high temperature SiC and Si in divided silicon tailing3N4Particulate Inclusion.When flowing through filter device containing the silicon liquid being mingled with,
Si3N4The main surface for being enriched in filter screen, and SiC is mainly attached to ceramic material surfaces in the hole in strainer, fills out simultaneously
Hole has been mended, particle has further been hindered and passes through strainer.The process of filtering is the process of a gradation in batches, can not be realized continuous
Production, and have preferable separating effect only for particle of the grain size more than 10 μm, the smaller Particulate Inclusion of grain size is detached
Inefficiency, and a large amount of silicon liquids are adhered in inner wall in the process, cause the loss of silicon material.
2nd, electromagnetism detaches
Electromagnetic separation technology is widely used in the nonmetal inclusion particle in separation metal bath now.Since silicon is melting
Conductivity under state differs larger compared with SiC, is considered as conductive melt.Therefore researcher considers to pass through electromagnetism in recent years
The separation to realize SiC particulate and Si in silicon tailing is detached, domestic scholars have studied high frequency magnetic field, strong sensing electric current in silicon
The centrifugation of SiC finds that SiC is due to the trend of the oriented melt edge enrichment of the effect of electromagnetic force after applying high-intensity magnetic field.But
It studies the high frequency magnetic field using more than 50kHz, and current value greatly wastes the energy in more than 200A, separation process.
3rd, directional solidification
Since the directional solidification technique that polycrystalline silicon ingot or purifying furnace uses is molten with segregating to for impurity of the segregation coefficient less than 1
Effect at the top of body.Since C the and N segregation coefficients in silicon are respectively less than 1.By the mode impurity segregation of directional solidification to molten
So as to have the function that C and N in divided silicon at the top of body.But due to the extremely weak mobility of melt in directional solidification furnace, although trip
From C and N can with solid liquid interface promote and segregate to final set region, but its supersaturation be precipitated particle phase SiC and
Si3N4The ingot casting being distributed widely in after solidification, can not realize the separation of particle and silicon.
Invention content
To solve the above problem of the existing technology, carbon in polysilicon, nitrogen impurity are removed the present invention provides a kind of
Method.By the way that during electron-beam smelting, glass sand is added into raw material, the melting environment of oxidisability is built, makes silicon
The carbon of middle dissolving, nitrogen are combined to form volatile oxidizing gas with oxygen, so as to be removed.Product made from this method
Carbon, nitrogen impurity removal effect are good, and have the characteristics that at low cost, purification efficiency is high.
To achieve the above object, the technical solution adopted by the present invention is as follows：The side of carbon, nitrogen impurity in a kind of removal polysilicon
Method, it is characterized in that：Include the following steps：
A. dispensing：Using the top cladding that polysilicon generates in ingot casting or purification process as raw material, the content of silicon in raw material
For 90-99wt%, rich in SiC, Si3N4Hard inclusions calculate the quality of required each section raw material according to raw material proportioning formula：
In formula, n is the quality of quartz sand, and m is the quality of silicon raw material, MSiO2、MCAnd MNIt is silica, carbon, nitrogen member respectively
The molal weight of element, wCAnd wNIt is the content for pushing up carbon and nitrogen in cladding respectively；
B. it feeds：After silicon raw material according to said ratio is cleaned, mixing, it is respectively charged into feed bin, melting kettle, feeding trolley
In, with high-purity silicon material shop fixtures in solidification crucible；
C. pre- thermionic electron guns：After charging, electron beam furnace vacuumizes, and starts preheating 3 when vacuum degree is less than 0.5Pa
Electron gun, wherein 2 irradiate melting kettle electron gun, another 1 irradiates solidification crucible electron gun, preheats 20-40min, has preheated
Enter the melting silicon materials stage into rear；
D. melting silicon materials：The situation of change of vacuum degree is protected in the melting conditions and fusion process observed in window according to the observation
It demonstrate,proves vacuum and is less than 0.5Pa, the electron gun power of 2 irradiation melting kettles is gradually increased to 300kW, according to 10kW-30kW-
50kW-100kW-150kW-200kW-250kW -300kW (single rifle) increase monitor system, and power is kept to make melting earthenware in 300kW
Silicon material is completely melt in crucible, and starts to react with quartz sand；The electron gun power of irradiation solidification crucible is gradually increased to 250kW,
Increase monitor system according to 10kW-30kW-50kW-100kW-150kW-200kW-250kW, power is kept to make solidification in 250kW
The silicon material of shop fixtures is completely melt in crucible；
E. silicon material melting：The electron gun power of 2 irradiation melting kettles continues to keep 300kW melting silicon materials 10-60min；
F. silicon liquid is toppled over：The 2 of melting kettle will be irradiated to close electron gun, silicon liquid is toppled over, after the completion of toppling over, by another 1
The electron gun power for irradiating solidification crucible keeps 250kW；
G. after the completion of toppling over, feed bin valve is opened, then a certain amount of silicon raw material is added in melting kettle, irradiation solidification
The electron gun of crucible still keeps 250kW, in addition 2 the electron gun of irradiation melting kettle is carried out silicon again according to step C to step E
Expect fusing, silicon material melting, silicon material toppling process, number of repetition is carried out according to the quality of required silicon ingot；
H. drop beam solidification：After melting, the electron gun for irradiating solidification crucible carries out drop beam solidification, takes silicon ingot after cooling
Go out.
The purity of high-purity silicon material is in more than 5N in the step B.
Beam is dropped in the step H and is solidified as 250kW-200kW-150kW-120kW -0, interval is 5 minutes.
The present invention selects the top cladding that polycrystalline silicon ingot casting/purification process generates to be used as raw material by adding quartz sand
Oxygen source using the feature environment of electron-beam smelting structure temperature and pressure-oxidisability, makes carbon, nitrogen be combined to be formed with oxygen and easily wave
Stimulating food matter so as to be evaporated removal, removes the significant effect of carbon, azepine prime element in silicon, and industrial applications have a extensive future.
Specific embodiment
The present invention is further described with reference to embodiments：
Embodiment 1
The method of carbon, nitrogen impurity, specifically includes following steps in a kind of removal polysilicon：
A. dispensing：Using the top cladding that polysilicon generates in ingot casting or purification process as raw material, the content of silicon in raw material
For 90-99wt%, rich in SiC, Si3N4Etc. hard inclusions.The matter of required each section raw material is calculated according to raw material proportioning formula
Amount：
In formula, n is the quality of quartz sand, and m is the quality of silicon raw material, MSiO2、MCAnd MNIt is silica, carbon, nitrogen member respectively
The molal weight of element, wCAnd wNIt is the content for pushing up carbon and nitrogen in cladding respectively；
B. it feeds：After silicon raw material according to said ratio is cleaned, mixing, it is respectively charged into feed bin, melting kettle, feeding trolley
In.With high-purity silicon material shop fixtures in solidification crucible, the purity of high-purity silicon material is in more than 5N；
C. pre- thermionic electron guns：After charging, electron beam furnace vacuumizes, and starts preheating 3 when vacuum degree is less than 0.5Pa
Electron gun, wherein 2 irradiate melting kettle electron gun, another 1 irradiates solidification crucible electron gun, 20min is preheated, after the completion of preheating
Into the melting silicon materials stage；
D. melting silicon materials：The situation of change of vacuum degree is protected in the melting conditions and fusion process observed in window according to the observation
It demonstrate,proves vacuum and is less than 0.5Pa, the electron gun power of 2 irradiation melting kettles is gradually increased to 300kW, according to 10kW-30kW-
50kW-100kW-150kW-200kW-250kW -300kW (single rifle) increase monitor system, and power is kept to make melting earthenware in 300kW
Silicon material is completely melt in crucible, and starts to react with quartz sand；The electron gun power of irradiation solidification crucible is gradually increased to 250kW,
Increase monitor system according to 10kW-30kW-50kW-100kW-150kW-200kW-250kW, power is kept to make solidification in 250kW
The silicon material of shop fixtures is completely melt in crucible；
E. silicon material melting：The electron gun power of 2 irradiation melting kettles continues to keep 300kW melting silicon materials 10min；
F. silicon liquid is toppled over：The 2 of melting kettle will be irradiated to close electron gun, silicon liquid is toppled over, after the completion of toppling over, by another 1
The electron gun power for irradiating solidification crucible keeps 250kW；
G. after the completion of toppling over, feed bin valve is opened, then a certain amount of silicon raw material is added in melting kettle, irradiation solidification
The electron gun of crucible still keeps 250kW, in addition 2 the electron gun of irradiation melting kettle is carried out silicon again according to step C to step E
Expect fusing, silicon material melting, silicon material toppling process, number of repetition is carried out according to the quality of required silicon ingot；
H. drop beam solidification：After melting, the electron gun for irradiating solidification crucible carries out drop beam solidification, 250kW-200kW-
150kW-120kW -0 (interval 5 minutes), takes out silicon ingot after cooling.
Embodiment 2
Carbon in a kind of removal polysilicon described in the present embodiment, nitrogen impurity each step of method with phase in embodiment 1
Together, different technical parameters is：
1) step C electron guns preheating 30min；
2) melting silicon material 35min in step E.
Embodiment 3
Carbon in a kind of removal polysilicon described in the present embodiment, nitrogen impurity each step of method with phase in embodiment 1
Together, different technical parameters is：
1) step C electron guns preheating 40min；
2) melting silicon material 60min in step E.
Finally it should be noted that：The above embodiments are only used to illustrate the technical solution of the present invention., rather than its limitations；To the greatest extent
Pipe is described in detail the present invention with reference to foregoing embodiments, it will be understood by those of ordinary skill in the art that：Its according to
Can so modify to the technical solution recorded in foregoing embodiments either to which part or all technical features into
Row equivalent replacement；And these modifications or replacement, various embodiments of the present invention technology that it does not separate the essence of the corresponding technical solution
The range of scheme.
Claims (3)
1. a kind of method for removing carbon, nitrogen impurity in polysilicon, it is characterized in that：Include the following steps：
A. dispensing：Using the top cladding that polysilicon generates in ingot casting or purification process as raw material, the content of silicon is 90- in raw material
99wt%, rich in SiC, Si3N4Hard inclusions calculate the quality of required each section raw material according to raw material proportioning formula：
In formula, n is the quality of quartz sand, and m is the quality of silicon raw material,MCAnd MNIt is silica, carbon, nitrogen respectively
Molal weight, wCAnd wNIt is the content for pushing up carbon and nitrogen in cladding respectively；
B. it feeds：After silicon raw material according to said ratio is cleaned, mixing, it is respectively charged into feed bin, melting kettle, feeding trolley,
With high-purity silicon material shop fixtures in solidification crucible；
C. pre- thermionic electron guns：After charging, electron beam furnace vacuumizes, and starts preheating 3 when vacuum degree is less than 0.5Pa electronics
Rifle, wherein 2 irradiate melting kettle electron gun, another 1 irradiates solidification crucible electron gun, 20-40min is preheated, after the completion of preheating
Into the melting silicon materials stage；
D. melting silicon materials：The situation of change of vacuum degree ensures true in the melting conditions and fusion process observed in window according to the observation
Sky is less than 0.5Pa, the electron gun power of 2 irradiation melting kettles is gradually increased to 300kW, according to 10kW-30kW-50kW-
100kW-150kW-200kW-250kW -300kW (single rifle) increase monitor system, and power is kept to make silicon in melting kettle in 300kW
Material is completely melt, and starts to react with quartz sand；The electron gun power of irradiation solidification crucible is gradually increased to 250kW, according to
10kW-30kW-50kW-100kW-150kW-200kW-250kW increases monitor system, and power is kept to make solidification crucible in 250kW
The silicon material of interior shop fixtures is completely melt；
E. silicon material melting：The electron gun power of 2 irradiation melting kettles continues to keep 300kW melting silicon materials 10-60min；
F. silicon liquid is toppled over：The 2 of melting kettle will be irradiated to close electron gun, silicon liquid is toppled over, after the completion of toppling over, by another 1 irradiation
The electron gun power of solidification crucible keeps 250kW；
G. after the completion of toppling over, feed bin valve is opened, then a certain amount of silicon raw material is added in melting kettle, irradiates solidification crucible
Electron gun still keep 250kW, in addition 2 the electron gun of irradiation melting kettle carried out silicon material again according to step C to step E melt
Change, silicon material melting, silicon material toppling process, number of repetition are carried out according to the quality of required silicon ingot；
H. drop beam solidification：After melting, the electron gun for irradiating solidification crucible carries out drop beam solidification, takes out silicon ingot after cooling.
2. a kind of method for removing carbon, nitrogen impurity in polysilicon according to claim 1, it is characterized in that：In the step B
The purity of high-purity silicon material is in more than 5N.
3. a kind of method for removing carbon, nitrogen impurity in polysilicon according to claim 1, it is characterized in that：In the step H
Drop beam is solidified as 250kW-200kW-150kW-120kW -0, and interval is 5 minutes.
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