CN103789829B - The method of silicon ingot bottom die homogeneous nucleation - Google Patents
The method of silicon ingot bottom die homogeneous nucleation Download PDFInfo
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- CN103789829B CN103789829B CN201410047496.8A CN201410047496A CN103789829B CN 103789829 B CN103789829 B CN 103789829B CN 201410047496 A CN201410047496 A CN 201410047496A CN 103789829 B CN103789829 B CN 103789829B
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Abstract
The invention discloses a kind of method of silicon ingot bottom die homogeneous nucleation, relate to the method and technology field that preparation has the homogeneous polycrystalline material of a fixed structure.Comprise the following steps: (1) transforms the thermal field in polycrystalline silicon ingot or purifying furnace, between the quartz crucible and graphite base plate of polycrystalline silicon ingot or purifying furnace, lay graphite flake; (2) heat, utilize well heater to heat the silicon material in quartz crucible; (3) melt, the temperature controlled in crucible carries out melt processed to silicon material; (4) long brilliant, the temperature and time controlled in polycrystalline silicon ingot or purifying furnace carries out growing brilliant process; (5) anneal; (6) cool.Use the silicon ingot that described method manufactures, the grain size of crystal is more even, and Impurity Distribution is also more average, and defect concentration reduces further, the final photoelectric transformation efficiency effectively improving solar cell.
Description
Technical field
The present invention relates to the method and technology field that preparation has the homogeneous polycrystalline material of a fixed structure, particularly relate to a kind of method of silicon ingot bottom die homogeneous nucleation.
Background technology
Polycrystalline silicon ingot or purifying furnace is a kind of heating installation for the production of polycrystal silicon ingot.Polycrystalline ingot furnace technological process comprises: heating (H), fusing (M), growth (G), annealing (A) and cooling (C) double teacher.The effect of heating phase carries out preheating to ingot furnace inside thermal field and silicon material; The object of fusion stage heats up gradually, finally makes silicon material all become the liquid-state silicon of melting; The object of growth phase is by cooling and the mode slowly promoting heat-insulation cage, completes the crystallisation process of liquid-state silicon to solid state si; The object of annealing stage eliminates polycrystal silicon ingot internal stress; The object of cooling stages is lowered the temperature to polycrystal silicon ingot, treats that temperature is to 450 DEG C, can come out of the stove.
Desirable crystal is atom is regular, periodic arrangement formation at three-dimensional space, but in practice, it is very regular and complete that atom can not arrange, and existence more or less departs from the region of ideal structure, these deflected areas are exactly lattice defect, and the number of defect is exactly defect concentration.As the new forms of energy of clean environment firendly, the application of solar cell is more and more universal, and traditional manufacture of solar cells process efficiency is lower, and the generated energy of unit surface is lower, because solar cell major part is installed on the ground, considerably increase the floor space of solar panel like this.Need to use silicon chip in the process manufacturing solar cell, silicon chip is formed by silicon ingot cutting, ingot furnace can be used in the process that silicon ingot makes, in prior art, the crucible of ingot furnace directly contacts with graphite base plate, because crucible edge is close to well heater, make crucible bottom have certain horizontal thermograde, have the trend of transverse growth after making crucible bottom nucleation, this is the major cause that bottom dendrite is formed and grain size is uneven.
In addition, in existing silicon ingot manufacture craft, heat-insulation cage adopts completely closed state to carry out material (fusion stage), after silicon material all changes into liquid, slowly opens heat-insulation cage and dispels the heat, in crucible bottom surface according to cold and hot different sequencing, and nucleation successively.First the crystal grain of nucleation can transversely be grown up, and the crystal grain then formed is totally less than normal, causes the symbiosis of bottom surface dendrite and large grain size and little crystal grain like this, causes grain size inconsistent.
Summary of the invention
Technical problem to be solved by this invention is to provide a kind of nucleation method of silicon ingot bottom even crystal grain, use the silicon ingot that described method manufactures, the grain size of crystal is more even, Impurity Distribution is also more average, defect concentration reduces further, the final photoelectric transformation efficiency effectively improving solar cell.
For solving the problems of the technologies described above, the technical solution used in the present invention is: a kind of method of silicon ingot bottom die homogeneous nucleation, is characterized in that comprising the following steps:
(1) thermal field in polycrystalline silicon ingot or purifying furnace is transformed, between the quartz crucible and graphite base plate of polycrystalline silicon ingot or purifying furnace, lay graphite flake;
(2) heat, utilize well heater to heat the silicon material in quartz crucible;
(3) melt, the temperature controlled in crucible carries out melt processed to silicon material;
(4) long brilliant, the temperature and time controlled in polycrystalline silicon ingot or purifying furnace carries out growing brilliant process;
(5) anneal;
(6) cool.
Preferably, described graphite flake is three-back-shaped, between graphite flake, fill graphite carbon felt.
Preferably, the thickness of described graphite flake is 5mm, and the edge of outermost graphite flake flushes with the edge of graphite base plate.
Preferably, described fusing is divided into two stages, and the first stage, control temperature was at 1550-1570 DEG C, and it is 5-7cm/h that heat-insulation cage promotes speed, and the time length is 0.5-1.5 hour; Subordinate phase keeps the position of heat-insulation cage, and control temperature is constant, and the time length is 9.5-10.5 hour.
Preferably, described long brilliant temperature controls at 1450-1470 DEG C, and it is 16-20cm/h that heat-insulation cage promotes speed, and the time length is 15-25 minute.
Preferably, described fusing is divided into two stages, and first stage control temperature is at 1560 DEG C, and it is 6cm/h that heat-insulation cage promotes speed, and the time length is 1 hour; Subordinate phase keeps the position of heat-insulation cage, and control temperature is constant, and the time length is 10 hours.
Preferably, described long brilliant temperature controls at 1460 DEG C, and it is 18cm/h that heat-insulation cage promotes speed, and the time length is 20 minutes.
The beneficial effect adopting technique scheme to produce is: present method has laid " Back Word type " graphite flake zonal structure of one deck 5mm height between graphite base plate and quartz crucible, the edge of zonal structure flushes with the edge of graphite base plate, graphite carbon felt is provided with between three-back-shaped graphite flake, graphite carbon felt has good heat insulation effect, lay can form localized temperature gradients in crucible bottom with such structure, be conducive under the cooperation of quick process for cooling, the rapid nucleation in crucible bottom surface multiple spot formation condensate depression, finally form the uniform little crystal grain of one deck in crucible bottom surface.
Present method keeps the aperture of heat-insulation cage at 6cm in the later stage of fusing, be that 0cm(is namely completely closed relative to existing technique heat-insulation cage aperture) state, be conducive to first giving out a part of heat, reduce the temperature of crucible bottom, after entering long brilliant section, heat-insulation cage is opened rapidly greatly, and in 20 minutes, heat-insulation cage is promoted to 12cm by 6cm, and shed amount of heat; Rate of temperature fall was down to 1460 by 2 hours of the prior art by 1560 simultaneously, became 20 minutes and was down to 1460 by 1560, reduce design temperature rapidly, meaned the thermal value reducing rapidly well heater.Well heater thermal value sharply reduces, and heat radiation simultaneously rolls up, and causes crucible bottom temperature to cool fast, final fast nucleation, coordinates " Back Word type " zonal structure in thermal field transformation, finally forms the uniform little crystal grain of one deck in crucible bottom surface.Impurity can be made like this to be distributed in crystal boundary more uniformly go, thus effectively reduce the defect concentration of crystals, the final overall quality improving silicon ingot, battery efficiency obtains the lifting of 0.2%, thus reaches the object reducing sun power use cost.
Accompanying drawing explanation
Below in conjunction with the drawings and specific embodiments, the present invention is further detailed explanation.
Fig. 1 is process flow sheet of the present invention;
Fig. 2 is the plan structure schematic diagram of graphite flake and the graphite carbon felt laid in the present invention;
Wherein: 1, graphite flake 2, graphite carbon felt.
Embodiment
As shown in Figure 1, a kind of method of silicon ingot bottom die homogeneous nucleation, comprises the following steps: (1) transforms the thermal field in polycrystalline silicon ingot or purifying furnace, between the quartz crucible and graphite base plate of polycrystalline silicon ingot or purifying furnace, lay graphite flake; Described graphite flake is three-back-shaped, graphite flake can be more than two circles, the width of graphite flake and number can adjust according to the structure of polycrystalline furnace, the good graphite carbon felt of heat-insulating property is filled between graphite flake and graphite flake, for the formation of thermograde, the thickness of described graphite flake is 5mm, and the outward flange of outermost graphite flake flushes with the edge of graphite base plate.(2) heat, utilize well heater to heat the silicon material in quartz crucible, this step is identical with casting ingot method of the prior art, does not repeat; (3) melt, described fusing is divided into two stages, and the first stage, control temperature was at 1550-1570 DEG C, and it is 5-7cm/h that heat-insulation cage promotes speed, and the time length is 0.5-1.5 hour; Subordinate phase keeps the position of heat-insulation cage, and control temperature is constant, and the time length is 9.5-10.5 hour; (4) long brilliant, described long brilliant temperature controls at 1450-1470 DEG C, and it is 16-20cm/h that heat-insulation cage promotes speed, and the time length is 15-25 minute; (5) anneal, this step is identical with casting ingot method of the prior art, does not repeat; (6) cool, this step is identical with casting ingot method of the prior art, does not repeat.
Described method has carried out the improvement of two aspects relative to prior art, first aspect, thermal field aspect: present method has laid " Back Word type " graphite flake zonal structure of one deck 5mm height between graphite base plate and quartz crucible, as shown in Figure 2, the edge of zonal structure flushes with the edge of graphite base plate, graphite carbon felt is provided with between three-back-shaped graphite flake, graphite carbon felt has good heat insulation effect, lay can form localized temperature gradients in crucible bottom with such structure, be conducive under the cooperation of quick process for cooling, the rapid nucleation in crucible bottom surface multiple spot formation condensate depression, finally form the uniform little crystal grain of one deck in crucible bottom surface.
Second aspect, process aspect: prior art processes is as shown in the table:
The technique of present method is as shown in the table:
Present method keeps the aperture of heat-insulation cage at 6cm in the later stage of fusing, be that 0cm(is namely completely closed relative to existing technique heat-insulation cage aperture) state, be conducive to first giving out a part of heat, reduce the temperature of crucible bottom, after entering growth section, heat-insulation cage is opened rapidly greatly, and in 20 minutes, heat-insulation cage is promoted to 12cm by 6cm, and shed amount of heat; Rate of temperature fall was down to 1460 by 2 hours of the prior art by 1560 simultaneously, became 20 minutes and was down to 1460 by 1560, reduce design temperature rapidly, meaned the thermal value reducing rapidly well heater.Well heater thermal value sharply reduces, and heat radiation simultaneously rolls up, and causes crucible bottom temperature to cool fast, final fast nucleation, coordinates " Back Word type " zonal structure in thermal field transformation, finally forms the uniform little crystal grain of one deck in crucible bottom surface.Impurity can be made like this to be distributed in crystal boundary more uniformly go, thus effectively reduce the defect concentration of crystals, the final overall quality improving silicon ingot, as shown in the table, the efficiency of solar cell finally obtains the lifting of 0.2%, thus reaches the object reducing sun power use cost.
Efficiency comparative's table of solar cell:
Apply specific case herein to set forth principle of the present invention and embodiment thereof, the explanation of above embodiment is only used to help to understand method of the present invention and core concept thereof.It should be pointed out that for the person of ordinary skill of the art, can also carry out some improvement and modification under the premise without departing from the principles of the invention to the present invention, these improve and modify and also fall in the protection domain of the claims in the present invention.
Claims (6)
1. a method for silicon ingot bottom die homogeneous nucleation, is characterized in that comprising the following steps:
(1) transform the thermal field in polycrystalline silicon ingot or purifying furnace, between the quartz crucible and graphite base plate of polycrystalline silicon ingot or purifying furnace, lay graphite flake, described graphite flake is three-back-shaped, between graphite flake, fill graphite carbon felt;
(2) heat, utilize well heater to heat the silicon material in quartz crucible;
(3) melt, the temperature controlled in crucible carries out melt processed to silicon material;
(4) long brilliant, the temperature and time controlled in polycrystalline silicon ingot or purifying furnace carries out growing brilliant process;
(5) anneal;
(6) cool.
2. the method for silicon ingot bottom die homogeneous nucleation according to claim 1, is characterized in that: the thickness of described graphite flake is 5mm, and the outward flange of outermost graphite flake flushes with the edge of graphite base plate.
3. the method for silicon ingot bottom die homogeneous nucleation according to claim 1, is characterized in that: described fusing is divided into two stages, and the first stage, control temperature was at 1550-1570 DEG C, and it is 5-7cm/h that heat-insulation cage promotes speed, and the time length is 0.5-1.5 hour; Subordinate phase keeps the position of heat-insulation cage, and control temperature is constant, and the time length is 9.5-10.5 hour.
4. the method for silicon ingot bottom die homogeneous nucleation according to claim 1, is characterized in that: described long brilliant temperature controls at 1450-1470 DEG C, and it is 16-20cm/h that heat-insulation cage promotes speed, and the time length is 15-25 minute.
5. the method for silicon ingot bottom die homogeneous nucleation according to claim 3, is characterized in that: described fusing is divided into two stages, and first stage control temperature is at 1560 DEG C, and it is 6cm/h that heat-insulation cage promotes speed, and the time length is 1 hour; Subordinate phase keeps the position of heat-insulation cage, and control temperature is constant, and the time length is 10 hours.
6. the method for silicon ingot bottom die homogeneous nucleation according to claim 4, is characterized in that: described long brilliant temperature controls at 1460 DEG C, and it is 18cm/h that heat-insulation cage promotes speed, and the time length is 20 minutes.
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| CN102330148A (en) * | 2011-07-30 | 2012-01-25 | 常州天合光能有限公司 | Polysilicon ingot casting method with low defect and high output and thermal field structure thereof |
| CN202246974U (en) * | 2011-08-30 | 2012-05-30 | 常州天合光能有限公司 | Polysilicon thermal field with local cooling device |
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| TWI441962B (en) * | 2011-10-14 | 2014-06-21 | Sino American Silicon Prod Inc | Crystalline silicon ingot and method of fabricating the same |
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| CN102330148A (en) * | 2011-07-30 | 2012-01-25 | 常州天合光能有限公司 | Polysilicon ingot casting method with low defect and high output and thermal field structure thereof |
| CN202246974U (en) * | 2011-08-30 | 2012-05-30 | 常州天合光能有限公司 | Polysilicon thermal field with local cooling device |
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