CN102452652A - Dephosphorizing method under vacuum solid volatilization in preparation of solar grade polysilicon - Google Patents
Dephosphorizing method under vacuum solid volatilization in preparation of solar grade polysilicon Download PDFInfo
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- CN102452652A CN102452652A CN2010105283422A CN201010528342A CN102452652A CN 102452652 A CN102452652 A CN 102452652A CN 2010105283422 A CN2010105283422 A CN 2010105283422A CN 201010528342 A CN201010528342 A CN 201010528342A CN 102452652 A CN102452652 A CN 102452652A
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Abstract
The invention discloses a dephosphorizing method under vacuum solid volatilization in preparation of solar grade polysilicon, which comprises the steps of: 1) removing the oxide layers on the surfaces of silicon particles and the metal impurities on the grain boundary by way of acid-washing, then washing with water and drying; 2) adding the nanoscale silica powder into the dried silicon particles and tabletting after mixing; and 3) heating and preserving temperature for the tabletted mixture under vacuum. By the dephosphorizing method under vacuum solid volatilization in preparation of solar grade polysilicon, silicon is not to be melted so that the method is low in energy consumption and easy to operate.
Description
Technical field
The present invention relates to the phosphorus removing method in a kind of polysilicon preparation, particularly relate to the method for the vacuum solid volatilization dephosphorization in a kind of solar-grade polysilicon preparation.
Background technology
The polysilicon power consumption is big, cost is high because Siemens Method is produced, and therefore, the technology that adopts metallurgy method directly Pure Silicon Metal to be purified to the purity of the needed 6N of solar-energy photo-voltaic cell from 2N purity is paid attention to by people and carried out extensive studies.Mainly contain metallic impurity iron, aluminium, calcium and nonmetallic impurity phosphorus, boron etc. in the Pure Silicon Metal,, can utilize the method for directional freeze to remove wherein because metallic impurity have very little segregation coefficient.And phosphorus, boron impurity are because its segregation coefficient big (near 1) adopts the directional freeze method of purification not obvious to its removal effect.
To phosphorus impurities,, can utilize to heat under the vacuum its evaporable method is removed because its vapour pressure is higher.Existing dephosphorization process mainly is through under vacuum, making silicon fusion dephosphorization with electron beam, or under vacuum, is incubated, and phosphorus is evaporated from molten silicon.Liquid dephosphorization down; Because the specific surface area of liquid-state silicon is less relatively; Especially during industrial production; The silicon liquor ratio surface of big volume becomes littler, and volatilization needs the long time from the surface thereby phosphorus is from silicon liquid internal divergence to silicon liquid surface, and the down long-time insulation of the application of electron beam and high temperature causes energy consumption big.
Summary of the invention
The technical problem that the present invention will solve provides the method for the vacuum solid volatilization dephosphorization in a kind of solar-grade polysilicon preparation.Through preparing in the process, adopt solid state reaction evaporable method to remove phosphorus impurities in the silicon at solar-grade polysilicon.The present invention need not the silicon fusing, and energy consumption is low, and processing ease.
For solving the problems of the technologies described above, the method for the vacuum solid volatilization dephosphorization in the solar-grade polysilicon preparation of the present invention comprises step:
1) method of employing pickling is removed the metallic impurity (as: Fe, Al, Ca) on silicon grain surface oxide layer (like silicon oxide) and the crystal boundary, washing then, drying;
2) add the nanometer grade silica powder in the dried silicon grain, mix the back compressing tablet;
3) mixture behind the compressing tablet is carried out heat tracing under vacuum.
Acid in the said step 1) is one or more the sour mixed solutions in hydrochloric acid, nitric acid, sulfuric acid and the hydrofluoric acid, and wherein, hydrochloric acid, nitric acid, sulfuric acid and hydrofluoric acid mass concentration scope separately is 5～20%, and the time of pickling can be 10～600 minutes; Washing be use deionized water or pure water clean to pH value be 7; Drying is to be under 0.1～10Pa in vacuum tightness, dry 1-10 hour.
The granularity of the silicon grain in the said step 1) is less than 100 orders, and the granularity of preferred silicon grain is 400～1000 orders.
The granularity of the nanometer grade silica powder said step 2) is 1～100,000 order; Purity is more than 99.9%; The silicon dioxide powder add-on is 0.1%～5% of a silicon grain weight, and wherein, the additional proportion of silicon dioxide powder is to decide according to the phosphorus content of analyzing in the silicon grain; Phosphorus content is high more, and the silicon dioxide powder of adding is many more.
Said step 2) the compressing tablet thickness in is 1～3mm.
Vacuum in the said step 3) is that vacuum tightness is the vacuum under 0.1～10Pa, and Heating temperature is 800～1100 ℃, and soaking time is 10～30 hours, and wherein, soaking time is to decide according to the phosphorus content in the silicon grain, and phosphorus content is high more, and heat-up time is long more.
The present invention is the high vapour pressure of utilizing phosphorus equally, and its volatilization is removed, but different with the liquid state volatilization technology that extensively adopted in the past be that what the present invention adopted is solid-state diffusion evaporable method.
Under the high temperature, silicon and silicon dioxde reaction generate the silicon monoxide volatilization, simultaneously the phosphorus on silicon grain surface are taken away, and the inner phosphorus of silicon grain constantly spreads to particle surface, thereby total phosphorous content is reduced.Solid state reaction dispensing volatile and liquid volatilization compared with techniques, same volume, solid granulates have the specific surface area more much bigger than liquid-state silicon, can improve the volatilization efficient of phosphorus impurities greatly.And than liquid dephosphorization, solid-state the dephosphorization Heating temperature is lower down, has reduced energy consumption.
Adopt method of the present invention, can the phosphorus impurities content in the Pure Silicon Metal be reduced to below the 2ppm from 5～10ppm.
In addition, adopt method dephosphorization of the present invention after, can directly heat up silicon fusing, carry out next step purification or ingot casting.
Embodiment
Below each embodiment be merely that the present invention narrates for example; But citedly in the instance do not constitute the limited field of the protection authority of the technology that the present invention is narrated like temperature, granularity, isoparametric concrete numerical value of time, the result in the instance do not represent yet the present invention the LIMIT RESULTS that can reach.
In following examples, the add-on of nanometer grade silica powder (granularity is 1～100,000 order) is to be basic calculation with silicon grain weight, and the purity of nanometer grade silica powder is more than 99.9%.
Embodiment 1
The method of the vacuum solid volatilization dephosphorization in the solar-grade polysilicon preparation may further comprise the steps:
1) is 400～1000 purpose particles with metal silico briquette raw material crushing, adopts the mixed solution of hydrochloric acid and hydrofluoric acid to clean 1 hour, remove the metallic impurity on silicon grain surface oxide layer and the crystal boundary; Use washed with de-ionized water then; To pH value be 7, be under the 0.1Pa in vacuum tightness again, vacuum-drying 10 hours; Wherein, phosphorus impurities content is 10ppm in the metal silico briquette raw material; The mass concentration of hydrochloric acid is 12%, and the mass concentration of hydrofluoric acid is 18%, and the mixed volume ratio of hydrochloric acid and hydrofluoric acid is 3: 1;
2) add 5% nanometer grade silica powder (weight that is the nanometer grade silica powder be silicon grain weight 5%) in the dried silicon grain, mix the back compressing tablet, compressing tablet thickness is 3mm;
3) be to be heated to 1000 ℃ under the vacuum of 0.1Pa in vacuum tightness with the mixture behind the compressing tablet, be incubated 10 hours.
Silicon after handling is carried out content analysis with ICP-MS (plasma mass spectrograph), and obtaining phosphorus content is 2ppm.
Embodiment 2
The method of the vacuum solid volatilization dephosphorization in the solar-grade polysilicon preparation may further comprise the steps:
1) be 400～1000 purpose particles with metal silico briquette raw material crushing; Adopt nitric acid and vitriolic mixed solution to clean 3 hours, the metallic impurity on removal silicon grain surface oxide layer and the crystal boundary, use then pure water clean to pH value be 7; Be under the 1Pa in vacuum tightness again, vacuum-drying 8 hours; Wherein, phosphorus impurities content is 10ppm in the metal silico briquette raw material, and the mass concentration of nitric acid is 10%, and the vitriolic mass concentration is 15%, and nitric acid is 1: 2 with vitriolic mixed volume ratio;
2) the nanometer grade silica powder of adding 5% in the dried silicon grain mixes the back compressing tablet, and compressing tablet thickness is 3mm;
3) be to be heated to 1000 ℃ under the vacuum of 1Pa in vacuum tightness with the mixture behind the compressing tablet, be incubated 30 hours.
Silicon after handling is carried out content analysis with ICP-MS (plasma mass spectrograph), and obtaining phosphorus content is 1.2ppm.
Embodiment 3
The method of the vacuum solid volatilization dephosphorization in the solar-grade polysilicon preparation may further comprise the steps:
1) be 400～1000 purpose particles with metal silico briquette raw material crushing; Adopt hydrochloric acid, nitric acid and vitriolic mixed solution to clean 5 hours, remove the metallic impurity on silicon grain surface oxide layer and the crystal boundary, using washed with de-ionized water to pH value then is 7; Be under the 3Pa in vacuum tightness again, vacuum-drying 6 hours; Wherein, phosphorus impurities content is 8ppm in the metal silico briquette raw material; The mass concentration of hydrochloric acid is 15%, and the mass concentration of nitric acid is 10%, and the vitriolic mass concentration is 5%, and hydrochloric acid, nitric acid and vitriolic mixed volume ratio are 1: 2: 5;
2) the nanometer grade silica powder of adding 3.5% in the dried silicon grain mixes the back compressing tablet, and compressing tablet thickness is 3mm;
3) be to be heated to 1000 ℃ under the vacuum of 3Pa in vacuum tightness with the mixture behind the compressing tablet, be incubated 20 hours.
Silicon after handling is carried out content analysis with ICP-MS (plasma mass spectrograph), and obtaining phosphorus content is 1.8ppm.
Embodiment 4
The method of the vacuum solid volatilization dephosphorization in the solar-grade polysilicon preparation may further comprise the steps:
1) be 400～1000 purpose particles with metal silico briquette raw material crushing; Adopt hydrochloric acid and vitriolic mixed solution to clean after 8 hours, remove the metallic impurity on silicon grain surface oxide layer and the crystal boundary, using washed with de-ionized water to pH value then is 7; Be under the 5Pa in vacuum tightness again, vacuum-drying 4 hours; Wherein, phosphorus impurities content is 5ppm in the metal silico briquette raw material, and the mass concentration of hydrochloric acid is 20%, and the vitriolic mass concentration is 5%, and nitric acid is 2: 1 with vitriolic mixed volume ratio;
2) the nanometer grade silica powder of adding 3% in the dried silicon grain mixes the back compressing tablet, and compressing tablet thickness is 3mm;
3) be to be heated to 1000 ℃ under the vacuum of 5Pa in vacuum tightness with the mixture behind the compressing tablet, be incubated 20 hours.
Silicon after handling is carried out content analysis with ICP-MS (plasma mass spectrograph), and obtaining phosphorus content is 1.3ppm.
Embodiment 5
The method of the vacuum solid volatilization dephosphorization in the solar-grade polysilicon preparation may further comprise the steps:
1) be 400～1000 purpose particles with metal silico briquette raw material crushing; Adopt the mixed solution of hydrochloric acid, nitric acid, sulfuric acid and hydrofluoric acid to clean 10 minutes; Remove the metallic impurity on silicon grain surface oxide layer and the crystal boundary; Use then pure water clean to pH value be 7, be under the 8Pa in vacuum tightness again, vacuum-drying 2 hours; Wherein, phosphorus impurities content is 5ppm in the metal silico briquette raw material, and the mass concentration of hydrochloric acid, nitric acid, sulfuric acid and hydrofluoric acid all is 5%, and the mixed volume ratio of hydrochloric acid, nitric acid, sulfuric acid and hydrofluoric acid is 1: 1: 1: 1;
2) the nanometer grade silica powder of adding 0.1% in the dried silicon grain mixes the back compressing tablet, and compressing tablet thickness is 1mm;
3) mixture behind the compressing tablet is heated to 800 ℃ under vacuum, is incubated 12 hours.
Silicon after handling is carried out content analysis with ICP-MS (plasma mass spectrograph), and obtaining phosphorus content is 1.5ppm.
Embodiment 6
The method of the vacuum solid volatilization dephosphorization in the solar-grade polysilicon preparation may further comprise the steps:
1) be 400～1000 purpose particles with metal silico briquette raw material crushing; Adopting mass concentration is that 20% hydrochloric acid cleaned 10 hours, removes the metallic impurity on silicon grain surface oxide layer and the crystal boundary, and using washed with de-ionized water to pH value then is 7; Be under the 10Pa in vacuum tightness again, vacuum-drying 1 hour; Wherein, phosphorus impurities content is 5ppm in the metal silico briquette raw material;
2) the nanometer grade silica powder of adding 1% in the dried silicon grain mixes the back compressing tablet, and compressing tablet thickness is 2mm;
3) be to be heated to 1100 ℃ under the vacuum of 10Pa in vacuum tightness with the mixture behind the compressing tablet, be incubated 15 hours.
Silicon after handling is carried out content analysis with ICP-MS (plasma mass spectrograph), and obtaining phosphorus content is 1.2ppm.
Claims (8)
1. the method for the vacuum solid volatilization dephosphorization during a solar-grade polysilicon prepares comprises step:
1) method of employing pickling is removed the metallic impurity on silicon grain surface oxide layer and the crystal boundary, washing then, drying;
2) add the nanometer grade silica powder in the dried silicon grain, mix the back compressing tablet;
3) mixture behind the compressing tablet is carried out heat tracing under vacuum.
2. the method for the vacuum solid volatilization dephosphorization in the solar-grade polysilicon preparation as claimed in claim 1; It is characterized in that: the acid in the said step 1) is one or more the sour mixed solutions in hydrochloric acid, nitric acid, sulfuric acid and the hydrofluoric acid; Wherein, hydrochloric acid, nitric acid, sulfuric acid and hydrofluoric acid mass concentration separately is 5～20%; The time of pickling is 10～600 minutes.
3. the method for the vacuum solid volatilization dephosphorization in the solar-grade polysilicon as claimed in claim 1 preparation is characterized in that: the washing in the said step 1) be use deionized water or pure water clean to pH value be 7; Drying in the step 1) is to be under 0.1～10Pa in vacuum tightness, dry 1-10 hour.
4. the method for the vacuum solid volatilization dephosphorization in the solar-grade polysilicon preparation as claimed in claim 1, it is characterized in that: the granularity of the silicon grain in the said step 1) is less than 100 orders.
5. the method for the vacuum solid volatilization dephosphorization in the solar-grade polysilicon preparation as claimed in claim 4, it is characterized in that: the granularity of the silicon grain in the said step 1) is 400～1000 orders.
6. the method for the vacuum solid volatilization dephosphorization in the solar-grade polysilicon preparation as claimed in claim 1; It is characterized in that: the granularity of the nanometer grade silica powder said step 2) is 1～100,000 order; Purity is more than 99.9%, and the silicon dioxide powder add-on is 0.1%～5% of a silicon grain weight.
7. the method for the vacuum solid volatilization dephosphorization in the solar-grade polysilicon preparation as claimed in claim 1, it is characterized in that: the compressing tablet thickness said step 2) is 1～3mm.
8. the method for the vacuum solid volatilization dephosphorization in the solar-grade polysilicon preparation as claimed in claim 1, it is characterized in that: the vacuum in the said step 3) is that vacuum tightness is the vacuum under 0.1～10Pa; Heating temperature is 800～1100 ℃, and soaking time is 10～30 hours.
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Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3010797A (en) * | 1957-07-26 | 1961-11-28 | Robert S Aries | High purity elemental silicon |
| JP2000327488A (en) * | 1999-05-25 | 2000-11-28 | Shin Etsu Chem Co Ltd | Production of silicon substrate for solar battery |
| CN1803598A (en) * | 2006-01-25 | 2006-07-19 | 昆明理工大学 | Method for preparing solar grade polysilicon |
| CN101122047A (en) * | 2007-09-14 | 2008-02-13 | 李绍光 | Method for manufacturing polycrystalline silicon used for solar battery |
| CN101628718A (en) * | 2008-07-16 | 2010-01-20 | 佳科太阳能硅(厦门)有限公司 | Method for removing impurity of phosphorus from metallurgical grade silicon |
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Patent Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3010797A (en) * | 1957-07-26 | 1961-11-28 | Robert S Aries | High purity elemental silicon |
| JP2000327488A (en) * | 1999-05-25 | 2000-11-28 | Shin Etsu Chem Co Ltd | Production of silicon substrate for solar battery |
| CN1803598A (en) * | 2006-01-25 | 2006-07-19 | 昆明理工大学 | Method for preparing solar grade polysilicon |
| CN101122047A (en) * | 2007-09-14 | 2008-02-13 | 李绍光 | Method for manufacturing polycrystalline silicon used for solar battery |
| CN101628718A (en) * | 2008-07-16 | 2010-01-20 | 佳科太阳能硅(厦门)有限公司 | Method for removing impurity of phosphorus from metallurgical grade silicon |
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