CN101597787B - Method for casting nitrogen-doped monocrystalline silicon with controllable nitrogen concentration under nitrogen - Google Patents
Method for casting nitrogen-doped monocrystalline silicon with controllable nitrogen concentration under nitrogen Download PDFInfo
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- CN101597787B CN101597787B CN2009100999908A CN200910099990A CN101597787B CN 101597787 B CN101597787 B CN 101597787B CN 2009100999908 A CN2009100999908 A CN 2009100999908A CN 200910099990 A CN200910099990 A CN 200910099990A CN 101597787 B CN101597787 B CN 101597787B
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- silico briquette
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Abstract
The present invention discloses a method for casting nitrogen-doped monocrystalline silicon with controllable nitrogen concentration under nitrogen. The method comprises the following steps: casting monocrystalline silicon under the protective atmosphere of the nitrogen, so that the nitrogen is doped in the casting process of polycrystalline silicon; adjusting the nitrogen doping concentration through controlling the pressure and the flow capacity of the nitrogen; directionally solidifying and casting the monocrystalline silicon through taking a monocrystalline silicon block which is not melted and is not partially dislocated as a seed crystal; and obtaining the cast nitrogen-doped monocrystalline silicon with controllable nitrogen concentration. The invention further discloses the nitrogen-dopedmonocrystalline silicon prepared by adopting the method, which contains boron, gallium and phosphor with the concentration of 1*10<15>-1*10<17>/cm<3>, and further contains the nitrogen with the concentration of 1*10<13>-5*10<15>/cm<3.
Description
Technical field
The present invention relates to technical field of semiconductors, relate in particular to the method for under nitrogen, casting the controlled doped monocrystalline silicon of nitrogen concentration.
Background technology
The energy and environment are the two large problems of world today's extensive concern, and sun power becomes the focus of people's R and D naturally as a kind of reproducible green energy resource.Since U.S.'s Bell Laboratory in 1954 was successfully developed first monocrystaline silicon solar cell, through the unremitting effort of whole world science and technology and industrial community, solar battery technology and industry had obtained great development.And the development of solar cell mainly is to be based upon on the basis of semiconductor silicon material.
Generally speaking, the preparation of silicon single crystal utilizes vertical pulling technology or zone melting technique and obtains, and can be used in electronic industry and photovoltaic industry, the efficiency of solar cell height of its preparation, but crystal preparation cost height, energy consumption height.
And utilize the directional casting technology, and can prepare casting polycrystalline silicon, can be used in the photovoltaic industry, though cost is relatively low,, not monocrystalline because it is a polycrystalline, so the solar battery efficiency of its preparation is low, limited its widespread use at solar cell.
In addition, dislocation is more in the silicon materials that prepare in the directional casting technology, so physical strength is lower.And current to influence the widely used major obstacle of solar cell be that cost is higher.The cost of solar cell is mainly at silicon chip, as reduces the thickness of each sheet silicon chip, makes the material usage of each sheet silicon chip reduce, and can effectively reduce the cost of solar cell.But because the physical strength of casting silicon chip is low, in case reduce the thickness of single silicon chip, silicon chip is dressed up in the process such as assembly in processing, cell preparation and series of cells, damage and broken is taken place easily, the percentage of damage of silicon chip increases, and still causes the increase of cost.Therefore, existing cast silicon is difficult to make the defective of thin silicon chip, causes the silicon chip cost to increase, and has also limited its use.
Summary of the invention
The invention provides the method for under nitrogen, casting the controlled doped monocrystalline silicon of nitrogen concentration, may further comprise the steps:
(1) dislocation-free raw material monocrystalline silico briquette is paved with crucible bottom, polysilicon is placed on the raw material monocrystalline silico briquette again, and the charging capacity of doping content calculating according to target adds electroactive adulterant, shove charge;
Wherein, described electroactive adulterant is boron, gallium or phosphorus; The concentration of electroactive adulterant in the target product that described target doping content will prepare for the present invention.Among the present invention, the target doping content of electroactive adulterant is 1 * 10
15～1 * 10
17/ cm
3
The thickness of described raw material monocrystalline silico briquette is preferably 5～20mm.Use too thin monocrystalline silico briquette, higher to the design requirements of foundry furnace thermal field, the control of the actual process of growth of casting monocrystalline silicon simultaneously requires too high; And use too thick monocrystalline silico briquette, will cause the increase of casting monocrystalline silicon cost.
(2) furnace chamber is evacuated back feeds argon gas, adjusts the position of stay-warm case in the stove, makes electroactive adulterant, polysilicon and be heated near the part material monocrystalline silico briquette of polysilicon; Be heated to gradually and make more than 1400 ℃ that polysilicon begins to melt, and maintain the temperature at for some time more than 1400 ℃, make the part material monocrystalline silico briquette of electroactive adulterant, polysilicon and close polysilicon be melted into liquid formation silicon melt, and the part material monocrystalline silico briquette of crucible bottom bottom does not melt.
Exist part material monocrystalline silico briquette not melted so that as the seed crystal of growing single-crystal silicon owing to will guarantee the crucible bottom bottom, in the optimized technical scheme, the thickness of the part material monocrystalline silico briquette of Rong Huaing is not at least 10% of raw material monocrystalline silico briquette total thickness, and promptly the thickness of the part material monocrystalline silico briquette of Rong Huaing is no more than 90% of raw material monocrystalline silico briquette total thickness; Simultaneously, in order to guarantee all to melt fully with the contacted polysilicon of raw material monocrystalline silico briquette, in the optimized technical scheme, the thickness of the part material monocrystalline silico briquette of thawing is at least 10% of raw material monocrystalline silico briquette total thickness.Therefore, in optimized technical scheme, be arranged in the silicon single crystal raw material of crucible bottom, place top, near polysilicon, thickness is that 10%～90% part silicon single crystal raw material of raw material monocrystalline silico briquette total thickness melts.
(3) when crystal growth, change argon gas into nitrogen, nitrogen gas pressure is 5～200Torr, and flow is 1～200L/min, cools off crucible bottom then, makes the heat exchange of silicon melt mainly occur in crucible bottom; Simultaneously the speed with 1～4mm/min promotes stay-warm case in the stove, make silicon melt from the bottom directional freeze gradually upwards because crucible bottom remains with the part silicon single crystal that does not melt, as the seed crystal induced growth, to contain nitrogen concentration be 1 * 10 thereby form at this
13～5 * 10
15/ cm
3Doped monocrystalline silicon.
Preferred employing purity is 99.999～99.9999% nitrogen among the present invention, can guarantee can not cross the low impurity effect quality product of introducing because of purity, and is unlikely again because of using highly purified nitrogen to increase cost.
Among the present invention, regulate thermal field by stay-warm case position in cooling crucible bottom and the adjustment stove, (the crystalline direction of growth vertically upward to form unidirectional hot-fluid, direction of heat flow is vertically downward) carry out directional freeze, only there is certain axial-temperature gradient in this process at the solid-liquid interface place, and, thereby the growth of realization from bottom to up casting monocrystalline silicon less at horizontal areal temperatuer gradient.Usually, take to be blown into cooling gas or to feed water coolant to cool off the crucible bottom in crucible bottom.Wherein, the gas commonly used that cooling gas can adopt safety cheaply to be easy to get adopts cooling rare gas element or cool nitrogen usually.
The doped monocrystalline silicon that aforesaid method makes, containing concentration is 1 * 10
15～1 * 10
17/ cm
3Boron, gallium or phosphorus, also containing concentration is 1 * 10
13～5 * 10
15/ cm
3Nitrogen.
Usually, the preparation of silicon single crystal employing vertical pulling method in the process of Grown by CZ Method silicon single crystal, must so that discharge dislocation, be avoided occurring crackle too much owing to dislocation in the crystal pulling process, even be caused crystalline fracture through the necking down stage behind seeding.Among the present invention,, cover the crucible bottom by the dislocation-free single crystal silico briquette that tiles in advance in crucible bottom, and control by thermal field, does not melt the bottom that keeps the dislocation-free single crystal silico briquette, with its seed crystal when melting back directional freeze at polysilicon, induced growth silicon single crystal; Simultaneously, thermal field control makes and only axially produces thermograde at solid-liquid interface, carries out directional freeze, has realized that no necking down casting is not contained the monocrystalline silico briquette of crystal boundary.Among the present invention, avoid vertical pulling method to prepare the problem of the expensive and high energy consumption of silicon single crystal, used directional solidification casting method production cheaply to have the silicon single crystal of higher battery conversion efficiency.
Further; among the present invention; employing is casting monocrystalline silicon under nitrogen protection atmosphere; make nitrogen in the polysilicon castingprocesses, mix; the doping content of nitrogen can be regulated by control nitrogen gas pressure and flow; thereby be implemented in the purpose of controlled nitrating in the casting monocrystalline silicon, obtain the controlled nitrating casting monocrystalline silicon of nitrogen concentration.Since nitrogen can pinning silicon in dislocation, improve the physical strength of casting monocrystalline silicon, so the preparation method of the controlled nitrating casting monocrystalline silicon of nitrogen concentration among the present invention, the preparation that realizes the casting monocrystalline silicon that physical strength is controlled is had important meaning.
Description of drawings
Fig. 1 is the optical microscope photograph after the nitrating casting monocrystalline silicon bottom sample corrosion that obtains in the embodiment of the invention 1.
Embodiment
Embodiment 1
The dislocation-free raw material monocrystalline silico briquette that with thickness is 20mm earlier is paved with crucible bottom, and the polysilicon with 240kg places crucible then, mixes the doping agent boron of 10mg, realizes shove charge.The furnace chamber back that is evacuated is fed argon gas, adjust the position of stay-warm case in the stove and be heated to 1430 ℃, the thick monocrystalline silico briquette of 5mm of boron, polysilicon and close polysilicon is heated, maintain the temperature at more than 1430 ℃, make all to be melted into liquid, form silicon melt near the thick monocrystalline silico briquette of the 5mm of polysilicon, whole polysilicon and boron.When crystal growth, change high-purity argon gas into nitrogen, the purity of nitrogen is 99.999%, nitrogen gas pressure is 10Torr, and flow is 100L/min, feeds water coolant in crucible bottom then, and promote stay-warm case with the speed of 1mm/min, make silicon melt from the bottom directional freeze gradually upwards, the thick monocrystalline silico briquette of the 15mm that does not melt by being layered on crucible bottom subordinate portion is as the seed crystal induced growth, casting forms the silicon single crystal of nitrating.
By four probe method test resistance rate and infrared absorption spectrum test nitrogen concentration, the concentration that obtains boron in the above-mentioned nitrating casting monocrystalline silicon is 3 * 10
15/ cm
3, the concentration of nitrogen is 1 * 10
15/ cm
3
After adopting preferential etch liquid that the bottom sample of the above-mentioned nitrating casting monocrystalline silicon that obtains is corroded, its defective is exaggerated, and observes by opticmicroscope, and the result as shown in Figure 1.The corrosive fluid that adopts is the Secco corrosive fluid, and its proportioning is HF: 0.15M K
2Cr
4O
7=1: 2.Can see in the crystal (being nitrating casting monocrystalline silicon B of the present invention) on the interface C of the single crystal B of the seed crystal A of bottom and casting there is not crystal boundary among Fig. 1, be silicon single crystal.
The room temperature fracture physical strength that records the casting monocrystalline silicon of nitrating in the present embodiment by 3 curved methods is 270N/mm
2, and under the similarity condition not the room temperature of the casting monocrystalline silicon of nitrating fracture physical strength be 200N/mm
2, the casting monocrystalline silicon ratio of nitrating or not casting monocrystalline silicon physical strength increases about 35%.
Embodiment 2
The dislocation-free single crystal silico briquette that with thickness is 10mm earlier is paved with crucible bottom, and the polysilicon with 240kg places crucible then, mixes the doping agent boron of 36mg, realizes shove charge.The furnace chamber back that is evacuated is fed argon gas, adjust the position of stay-warm case in the stove and be heated to 1450 ℃, the thick monocrystalline silico briquette of 3mm of boron, polysilicon and close polysilicon is heated, maintain the temperature at more than 1450 ℃, make all to be melted into liquid, form silicon melt near the thick monocrystalline silico briquette of the 3mm of polysilicon, whole polysilicon and boron.When crystal growth, change high-purity argon gas into nitrogen, the purity of nitrogen is 99.9999%, nitrogen gas pressure is 10Torr, and flow is 10L/min, is blown into the cooling helium in crucible bottom then, and promote stay-warm case with the speed of 3mm/min, make silicon melt from the bottom directional freeze gradually upwards, the thick monocrystalline silico briquette of the 7mm that does not melt by being layered on crucible bottom subordinate portion is as the seed crystal induced growth, casting forms the silicon single crystal of nitrating.
By four probe method test resistance rate and infrared absorption spectrum test nitrogen concentration, the concentration that obtains boron in the cast silicon monocrystalline of nitrating is 1 * 10
16/ cm
3, the concentration of nitrogen is 1 * 10
14/ cm
3
The room temperature fracture physical strength that records the casting monocrystalline silicon of nitrating in the present embodiment by 3 curved methods is 240N/mm
2, and under the similarity condition not the room temperature of the casting monocrystalline silicon of nitrating fracture physical strength be 200N/mm
2, the casting monocrystalline silicon of nitrating is than the not casting monocrystalline silicon physical strength increase by 20% of nitrating.
Claims (2)
1. under nitrogen, cast the method for the controlled doped monocrystalline silicon of nitrogen concentration, may further comprise the steps:
(1) dislocation-free raw material monocrystalline silico briquette is paved with crucible bottom, again polysilicon is placed on the raw material monocrystalline silico briquette, add electroactive adulterant, shove charge;
Wherein, described electroactive adulterant is boron, gallium or phosphorus;
(2) furnace chamber is evacuated back feeds argon gas, and the position of adjusting stay-warm case in the stove also is heated to more than 1400 ℃, makes electroactive adulterant, polysilicon and be melted into liquid near the part material monocrystalline silico briquette of polysilicon;
The thickness of the part material monocrystalline silico briquette of described thawing be raw material monocrystalline silico briquette total thickness 10%～90%;
(3) when crystal growth, change argon gas into nitrogen, nitrogen gas pressure is 5～200Torr, and flow is 1～200L/min; Promote in the stove stay-warm case and cool off the crucible bottom with the speed of 1～4mm/min then, as seed crystal, directional freeze forms that to contain nitrogen concentration be 1 * 10 with the part material monocrystalline silico briquette that do not melt in the crucible bottom bottom
13～5 * 10
15/ cm
3Doped monocrystalline silicon;
The add-on of described electroactive adulterant is 1 * 10 with boron, gallium or the phosphorus concentration that contains in the doped monocrystalline silicon that forms
15～1 * 10
17/ cm
3Meter.
2. method according to claim 1 is characterized in that: in the step (1), the thickness of described dislocation-free raw material monocrystalline silico briquette is 5～20mm.
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Families Citing this family (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101597788B (en) * | 2009-06-24 | 2011-12-07 | 浙江大学 | Method for preparing cast nitrogen-doped monocrystalline silicon through melting polycrystalline silicon under nitrogen |
| CN102168312A (en) * | 2011-03-09 | 2011-08-31 | 浙江大学 | High-nitrogen-doped silicon chip and rapid nitrogen doping method |
| CN102206857A (en) * | 2011-04-30 | 2011-10-05 | 常州天合光能有限公司 | 111 crystal orientation cast silicon monocrystal and preparation method thereof |
| CN102817071A (en) * | 2012-06-20 | 2012-12-12 | 合肥景坤新能源有限公司 | Preparation technology of heat radiation resistant Czochralski polysilicon or monocrystalline silicon |
| CN107385507A (en) * | 2017-07-19 | 2017-11-24 | 内蒙古中环光伏材料有限公司 | A kind of method of monocrystalline silicon crystal pulling device and the application device |
| CN108315820A (en) * | 2018-04-13 | 2018-07-24 | 内蒙古中环光伏材料有限公司 | A method of producing pulling of crystals silicon rod using doped monocrystalline silicon reclaimed materials |
| CN113862775B (en) * | 2021-09-30 | 2022-06-10 | 西安奕斯伟材料科技有限公司 | Equipment and method for manufacturing nitrogen-doped monocrystalline silicon |
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