CN111705358A - Cast monocrystalline silicon ingot and preparation method thereof - Google Patents
Cast monocrystalline silicon ingot and preparation method thereof Download PDFInfo
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- 229910021421 monocrystalline silicon Inorganic materials 0.000 title claims abstract description 59
- 238000002360 preparation method Methods 0.000 title claims abstract description 15
- 239000013078 crystal Substances 0.000 claims abstract description 297
- 230000007547 defect Effects 0.000 claims abstract description 87
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 claims abstract description 75
- 229910052710 silicon Inorganic materials 0.000 claims abstract description 63
- 239000010703 silicon Substances 0.000 claims abstract description 63
- 238000000034 method Methods 0.000 claims abstract description 31
- 239000002210 silicon-based material Substances 0.000 claims abstract description 20
- 238000010438 heat treatment Methods 0.000 claims abstract description 8
- 238000011068 loading method Methods 0.000 claims abstract description 5
- 238000005520 cutting process Methods 0.000 claims description 21
- 229910052581 Si3N4 Inorganic materials 0.000 claims description 20
- HQVNEWCFYHHQES-UHFFFAOYSA-N silicon nitride Chemical compound N12[Si]34N5[Si]62N3[Si]51N64 HQVNEWCFYHHQES-UHFFFAOYSA-N 0.000 claims description 20
- 239000002002 slurry Substances 0.000 claims description 15
- 238000011049 filling Methods 0.000 claims description 12
- 239000011863 silicon-based powder Substances 0.000 claims description 12
- 238000004519 manufacturing process Methods 0.000 claims description 11
- 239000011268 mixed slurry Substances 0.000 claims description 6
- 238000001035 drying Methods 0.000 claims description 4
- 239000000945 filler Substances 0.000 claims description 3
- 239000012535 impurity Substances 0.000 abstract description 16
- 230000000052 comparative effect Effects 0.000 description 10
- 238000012360 testing method Methods 0.000 description 7
- 238000002844 melting Methods 0.000 description 5
- 230000008018 melting Effects 0.000 description 5
- 238000005266 casting Methods 0.000 description 4
- 239000007788 liquid Substances 0.000 description 4
- OKKJLVBELUTLKV-UHFFFAOYSA-N Methanol Chemical compound OC OKKJLVBELUTLKV-UHFFFAOYSA-N 0.000 description 3
- 230000000694 effects Effects 0.000 description 3
- 230000002093 peripheral effect Effects 0.000 description 3
- 238000005475 siliconizing Methods 0.000 description 3
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 description 2
- 238000006243 chemical reaction Methods 0.000 description 2
- 239000008187 granular material Substances 0.000 description 2
- 238000005424 photoluminescence Methods 0.000 description 2
- 229910021420 polycrystalline silicon Inorganic materials 0.000 description 2
- 239000000843 powder Substances 0.000 description 2
- 239000002904 solvent Substances 0.000 description 2
- 238000003756 stirring Methods 0.000 description 2
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 2
- 239000003513 alkali Substances 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 238000009826 distribution Methods 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 230000031700 light absorption Effects 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000010899 nucleation Methods 0.000 description 1
- 230000000737 periodic effect Effects 0.000 description 1
- 239000012466 permeate Substances 0.000 description 1
- 238000010248 power generation Methods 0.000 description 1
- 239000002244 precipitate Substances 0.000 description 1
- 238000004064 recycling Methods 0.000 description 1
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- C—CHEMISTRY; METALLURGY
- C30—CRYSTAL GROWTH
- C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
- C30B11/00—Single-crystal growth by normal freezing or freezing under temperature gradient, e.g. Bridgman-Stockbarger method
-
- C—CHEMISTRY; METALLURGY
- C30—CRYSTAL GROWTH
- C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
- C30B11/00—Single-crystal growth by normal freezing or freezing under temperature gradient, e.g. Bridgman-Stockbarger method
- C30B11/14—Single-crystal growth by normal freezing or freezing under temperature gradient, e.g. Bridgman-Stockbarger method characterised by the seed, e.g. its crystallographic orientation
-
- C—CHEMISTRY; METALLURGY
- C30—CRYSTAL GROWTH
- C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
- C30B29/00—Single crystals or homogeneous polycrystalline material with defined structure characterised by the material or by their shape
- C30B29/02—Elements
- C30B29/06—Silicon
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- Engineering & Computer Science (AREA)
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- Crystals, And After-Treatments Of Crystals (AREA)
Abstract
The invention relates to a cast monocrystalline silicon ingot and a preparation method thereof. The preparation method of the cast monocrystalline silicon ingot comprises the following steps: laying single crystal seed crystals at the bottom of the crucible to form a single crystal seed crystal layer; laying at least one single crystal strip around the single crystal seed crystal layer, and splicing the single crystal strip and the adjacent single crystal seed crystals, wherein the defect ratio of the single crystal strip is greater than that of the adjacent single crystal seed crystals; and (3) loading silicon materials on the monocrystalline seed crystal layer and at least one monocrystalline strip, heating to completely melt the silicon materials and partially melt the monocrystalline seed crystal layer, and growing crystals to obtain the cast monocrystalline silicon ingot. According to the preparation method of the cast monocrystalline silicon ingot, impurities are easily adsorbed at the defect position in the monocrystalline strip in the growth process of the monocrystal, so that the impurity content of corner silicon blocks and the generation probability of the corner silicon block defects are reduced. The area with larger defect ratio can release the growth stress at the edge of the silicon ingot, thereby reducing the generation and increment of defects. In addition, the invention also relates to a cast monocrystalline silicon ingot prepared by the preparation method.
Description
Technical Field
The invention relates to the technical field of solar photovoltaic materials, in particular to a cast monocrystalline silicon ingot and a preparation method thereof.
Background
Solar photovoltaic power generation is one of the fastest-developing forms of sustainable energy utilization, and is rapidly developed in all countries in recent years. Currently, a method for producing a single crystal silicon for solar use by a casting method is receiving more and more attention. The cast monocrystalline silicon has the advantage of low defect of czochralski monocrystalline silicon, and a pyramid-shaped texture can be formed by an alkali texturing method, so that the absorption of light is improved, and the conversion efficiency is improved; meanwhile, the cast monocrystalline silicon also has the advantages of low production cost and high yield of cast polycrystalline silicon. Therefore, the cast monocrystalline silicon inherits the advantages of the czochralski monocrystalline silicon and the cast polycrystalline silicon, overcomes the respective defects of the two modes, and the quality of the produced monocrystalline silicon is close to that of the czochralski monocrystalline silicon. The conversion efficiency of the battery is improved by more than 1% on the premise of not obviously increasing the cost of the silicon chip. Becomes an important way to reduce the production cost of the solar cell.
The traditional preparation method of the cast monocrystalline silicon ingot comprises the following steps: laying a certain amount of single crystal seed crystals at the bottom of the crucible, laying a silicon material above the single crystal seed crystals, heating and melting the silicon material, and simultaneously controlling the incomplete melting of the single crystal seed crystals so that the crystals grow into cast single crystals on the incompletely melted single crystal seed crystals. However, in the production process of actually casting a single crystal silicon ingot, the corner silicon block near the edge of the crucible is easily extruded by the polycrystal, resulting in high defect of the corner silicon block.
Disclosure of Invention
In view of the above, it is necessary to provide a cast single crystal silicon ingot and a method for preparing the same, which can reduce the defects of corner silicon blocks.
A preparation method of a cast monocrystalline silicon ingot comprises the following steps:
laying single crystal seed crystals at the bottom of the crucible to form a single crystal seed crystal layer;
laying at least one single crystal strip around the single crystal seed crystal layer, and splicing the single crystal strip and the adjacent single crystal seed crystal, wherein the defect ratio of the single crystal strip is greater than that of the adjacent single crystal seed crystal;
and loading silicon materials on the single crystal seed crystal layer and at least one single crystal strip, heating to completely melt the silicon materials and partially melt the single crystal seed crystal layer, and growing crystals to obtain the cast single crystal silicon ingot.
According to the preparation method of the cast monocrystalline silicon ingot, impurities are easily adsorbed at the defect position in the monocrystalline strip in the growth process of the monocrystal, so that the impurity content of corner silicon blocks and the generation probability of the corner silicon block defects are reduced. In addition, the region with larger defect ratio can release the growth stress at the edge of the silicon ingot, thereby reducing the generation and increment of defects in the cast single crystal silicon ingot.
In one embodiment, the single crystal strip is prepared by the following method: and cutting the cast single crystal block to obtain a head, detecting the defect ratio of the cutting surface, and cutting the head with the defect ratio of the cutting surface being more than 50% into a plurality of single crystal strips.
In one embodiment, in the operation of laying at least one single crystal strip around the single crystal seed layer, the cutting surface of the single crystal strip with the defect ratio of more than 50% faces the adjacent single crystal seed crystal.
In one embodiment, the single crystal strip is a cuboid, the length and the height of the single crystal strip are the same as those of adjacent single crystal seed crystals, and the width of the single crystal strip is 5-40 mm.
In one embodiment, the single crystal strips spliced with each other have different side crystal directions from the adjacent single crystal seed crystals.
In one embodiment, the number of the single crystal strips is a plurality, the single crystal strips are sequentially spliced end to end, and the side crystal directions of two adjacent single crystal strips spliced with each other are different.
In one embodiment, the method further comprises the following steps before the silicon material is filled:
and filling silicon-based slurry around the single crystal strip, wherein the silicon-based slurry is mixed slurry of silicon nitride and silicon powder or silicon nitride slurry, and drying to form the silicon-based filling strip.
In one embodiment, in the mixed slurry of silicon nitride and silicon powder, the mass ratio of the silicon nitride to the silicon powder is (2-10): 1.
in one embodiment, the ratio of the height of the silicon-based filling bar to the height of the single crystal seed crystal is (5-7): 10.
also provides a cast monocrystalline silicon ingot prepared by the preparation method of the cast monocrystalline silicon ingot.
According to the preparation method of the cast monocrystalline silicon ingot, impurities are easily adsorbed at the defect position in the monocrystalline strip in the growth process of the monocrystal, so that the impurity content of corner silicon blocks and the generation probability of the corner silicon block defects are reduced. In addition, the region with larger defect ratio can release the growth stress at the edge of the silicon ingot, thereby reducing the generation and increment of defects in the cast single crystal silicon ingot. Therefore, the cast silicon single crystal ingot produced by the above-described method for producing a cast silicon single crystal ingot has fewer defects.
Drawings
FIG. 1 is a flow chart of a method of manufacturing a cast single crystal silicon ingot in accordance with one embodiment of the present invention;
FIG. 2 is a schematic side view of a crucible, a single crystal seed layer and a single crystal strip in accordance with one embodiment of the present invention;
FIG. 3 is a schematic plan view of a crucible, a single crystal seed layer and a single crystal strip in accordance with one embodiment of the present invention;
FIG. 4 is a schematic view of a crucible, a single crystal seed layer and a single crystal strip in accordance with another embodiment of the present invention;
FIG. 5 is a PL diagram of a cut surface of a cast single-crystal head ingot in example 1;
FIG. 6 is a side view PL of the cast single crystal silicon ingot of example 1;
FIG. 7 is a side PL view of a cast single crystal silicon ingot of comparative example 1;
FIG. 8 is a photograph of a bottom corner block of the cast single crystal silicon ingot of example 2;
FIG. 9 is a photograph of a bottom corner block of the cast single crystal silicon ingot of example 3;
FIG. 10 is a photograph of a bottom corner block of the cast single crystal silicon ingot of comparative example 2.
Detailed Description
In order to make the aforementioned objects, features and advantages of the present invention comprehensible, embodiments accompanied with figures are described in detail below. In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein.
Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terminology used in the description of the invention herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items.
Referring to fig. 1, a method for preparing a cast silicon single crystal ingot according to an embodiment of the present invention includes the following steps:
and S10, laying single crystal seed crystals at the bottom of the crucible to form a single crystal seed crystal layer.
Referring also to fig. 2-4, crucible 110 is a crucible commonly used in the art for casting monocrystalline silicon ingots. Wherein, the seed crystal is a small crystal with the same crystal orientation as the needed crystal, and is a seed for growing a single crystal, also called seed crystal. The single crystal seed layer 120 is used to prepare a seeding layer for casting a single crystal silicon ingot.
In the operation of laying the single crystal seed crystals at the bottom of the crucible, the crystal orientation of the single crystal seed crystals is not limited, and the single crystal seed crystals are laid at the central position of the bottom of the crucible in a closely-arranged mode, so that gaps among the single crystal seed crystals are as small as possible, and crystal boundaries and dislocation introduced from the gaps of the seed crystals are reduced.
S20, laying at least one single crystal strip around the single crystal seed crystal layer, and splicing the single crystal strip and the adjacent single crystal seed crystal, wherein the defect ratio of the single crystal strip is greater than that of the adjacent single crystal seed crystal.
Referring to fig. 2 to 4, the defect ratio of the single crystal bar 130 refers to the ratio of defects in the single crystal bar 130 to defects in the single crystal bar 130. The defect ratio of a single crystal seed refers to the fraction of defects within the single crystal seed that are within the single crystal seed. The method for calculating the defect ratio of the single crystal strip 130 to the single crystal seed crystal comprises the following steps: after testing with PL (photoluminescence) equipment, a ratio of the area of the black region (defect) to the measured single crystal area was calculated by software. By testing the defect ratio of the surface, the defect ratio of the entire single crystal strip 130 or the single crystal seed can be estimated, and the variation trends of the defect ratio and the defect ratio are the same. Wherein defects refer to a disruption of the periodic symmetry of the crystal, such that the actual crystal deviates from the crystal structure of the ideal crystal. According to the dimension of the defect, the defect can be classified into a point defect, a line defect, a surface defect and a bulk defect. The point defects include vacancies, interstitial atoms, microdefects, and the like. The line defects include dislocations and the like. The surface defects mainly include grain boundaries in homogeneous crystals, small-angle grain boundaries, stacking faults, phase boundaries between heterogeneous crystals, and the like. There are many types of body defects, including inclusions, bubbles, voids, micro-precipitates, etc. The defects may be located either within the single crystal ribbon or single crystal seed or on the surface of the single crystal ribbon or single crystal seed.
In one embodiment, the single crystal ribbon 130 is prepared by the following method: and cutting the cast single crystal block to obtain a head, detecting the defect ratio of the cutting surface, and cutting the head with the defect ratio of the cutting surface being more than 50% into a plurality of single crystal strips.
Wherein, PL (photoluminescence) technology can be adopted to detect the defect distribution and calculate the defect ratio of the cutting surface. The defect ratio is equal to the ratio of the defect area to the silicon area. The larger the defect ratio, the more defects are indicated. It should be noted that the defect ratio of the cut surface is not much different from the defect ratio of the entire head, and therefore, the defect ratio of the cut surface measured by PL is equivalent to the obtained defect ratio value of the entire head.
The method for preparing the single crystal strip 130 is beneficial to recycling the head of the cast single crystal block with higher defects and improving the utilization value of the cast single crystal block.
In one embodiment, in the operation of laying at least one single crystal strip around the single crystal seed layer, the cutting surface of the single crystal strip with the defect ratio of more than 50% faces the adjacent single crystal seed crystal. Therefore, in the crystal growth process, the cutting surface of the single crystal strip is close to the single crystal seed crystal, so that the defects in the cutting surface of the single crystal strip can adsorb the impurities around the single crystal seed crystal spliced with the cutting surface of the single crystal strip, and the impurity content of the corner silicon block and the generation probability of the corner silicon block defects are reduced.
In one embodiment, the single crystal strip 130 is a rectangular parallelepiped, the length and height of the single crystal strip 130 are the same as those of the adjacent single crystal seed crystal, and the width of the single crystal strip 130 is 5mm to 40 mm. Herein, the height refers to the dimension of the element in the direction perpendicular to the plane of the bottom of the crucible 110. Correspondingly, length refers to the dimension of the element perpendicular to the height direction. Width refers to the dimension perpendicular to both the height and length directions.
Therefore, the matching of the single crystal strip 130 and the adjacent single crystal seed crystals is facilitated, namely the single crystal strip 130 with the same length is spliced with the single crystal seed crystals, the single crystal seed crystals at the corner positions are always protected by the single crystal strips 130 with the same peripheral length in the crystal growing process, and the impurity content of corner silicon blocks and the generation probability of the corner silicon block defects are further facilitated to be reduced.
In one embodiment, the single crystal ribbon 130 is spliced to one another in a lateral crystallographic orientation different from that of the adjacent single crystal seed. Therefore, dislocation sources caused by gaps spliced between the single crystal strips and adjacent single crystal seed crystals can be reduced, and the effect of reducing dislocation of the cast single crystal is achieved.
In one embodiment, the number of the single crystal strips 130 is several, the several single crystal strips 130 are sequentially spliced end to end, and the side crystal directions of two adjacent single crystal strips 130 spliced with each other are different. At this time, the plurality of single crystal strips 130 are arranged around the periphery of the single crystal seed layer 120, and impurities are easily adsorbed at the defects of the plurality of single crystal strips 130 in the growth process of the single crystal, so that the impurity content of the silicon blocks at the peripheral corners is reduced, and the generation probability of the defects of the silicon blocks at the peripheral corners is reduced. The dislocation source caused by the splicing gap between two adjacent single crystal strips can be reduced due to different crystal orientations of the side surfaces, and the effect of reducing the dislocation of the cast single crystal is achieved.
Further, referring to fig. 4, before loading the silicon material, the method further includes the following steps:
silicon-based slurry is filled around the single crystal bar 130, the silicon-based slurry is mixed slurry of silicon nitride and silicon powder or silicon nitride slurry, and the silicon-based filler bar 140 is formed after drying.
Wherein, the solvent in the silicon-based slurry is water, alcohol or methanol. Of course, other solvents capable of dissolving the silicon-based slurry may also be used.
Since the silicon-based filling strips 140 are positioned around the single crystal strips 130, the silicon-based filling strips can play a role in preventing silicon liquid from permeating into the bottoms of the seed crystals of the corner blocks in the high-temperature melting stage.
Further, in the mixed slurry of silicon nitride and silicon powder, the mass ratio of the silicon nitride to the silicon powder is (2-10): 1. silicon nitride is mixed with silicon powder, has combined the great silicon powder of granule and the less silicon nitride of granule, can guarantee to be difficult to the fracture after the drying like this, can play the effect that blocks the monocrystalline seed crystal bottom that the silicon liquid permeates the corner piece in the high temperature melting stage.
Further, the ratio of the height of the silicon-based filling strips to the height of the single crystal seed crystals is (5-7): 10. the height of the crystal seed after being melted is kept consistent, so that the crystal seed can fully prevent silicon liquid from permeating into the bottom of the single crystal seed of the corner block in the high-temperature melting stage in the crystal growing process.
And S30, loading silicon materials on the monocrystalline seed crystal layer and at least one monocrystalline strip, heating to completely melt the silicon materials and partially melt the monocrystalline seed crystal layer, and growing crystals to obtain the cast monocrystalline silicon ingot.
Wherein, a conventional crystal growth process can be adopted, which is not described herein.
According to the preparation method of the cast monocrystalline silicon ingot, impurities are easily adsorbed at the defect position in the monocrystalline strip in the growth process of the monocrystal, so that the impurity content of corner silicon blocks and the generation probability of the corner silicon block defects are reduced. In addition, the region with larger defect ratio can release the growth stress at the edge of the silicon ingot, thereby reducing the generation and increment of defects in the cast single crystal silicon ingot.
The cast single crystal silicon ingot of an embodiment is produced by the above-described method for producing a cast single crystal silicon ingot.
According to the preparation method of the cast monocrystalline silicon ingot, impurities are easily adsorbed at the defect position in the monocrystalline strip in the growth process of the monocrystal, so that the impurity content of corner silicon blocks and the generation probability of the corner silicon block defects are reduced. In addition, the region with larger defect ratio can release the growth stress at the edge of the silicon ingot, thereby reducing the generation and increment of defects in the cast single crystal silicon ingot. Therefore, the cast silicon single crystal ingot produced by the above-described method for producing a cast silicon single crystal ingot has fewer defects.
The cast single crystal silicon ingot and the method for producing the same according to the present invention will be further described with reference to the following specific examples.
Example 1
The cast single crystal ingot was cut to obtain a head, and subjected to PL test.
The cast single-crystal head single-crystal ingot having a defect ratio not lower than that shown in FIG. 5 was selected.
And cutting the head single crystal block with the larger defect ratio into a plurality of single crystal strips with the length of 159mm, the width of 30mm and the height of 25 mm.
6 x 6 seed cubes of 159mm x 25mm were laid in the crucible.
And splicing and laying a plurality of cut single crystal strips end to end in sequence around the single crystal seed crystals.
After the laying, silicon materials are loaded on the monocrystalline seed crystal layer and the plurality of monocrystalline strips, the heating is carried out to completely melt the silicon materials and partially melt the monocrystalline seed crystal layer, and the cast monocrystalline silicon ingot of the embodiment 1 is obtained after crystal growth.
Example 2
The cast single crystal ingot was cut to obtain a head, and subjected to PL test.
The cast single-crystal head single-crystal ingot having a defect ratio not lower than that shown in FIG. 5 was selected.
And cutting the head single crystal block with the larger defect ratio into a plurality of single crystal strips with the length of 158mm, the width of 40mm and the height of 20 mm.
6 x 6 blocks of 158mm x 20mm single crystal seeds were laid in the crucible.
And splicing and laying a plurality of cut single crystal strips end to end in sequence around the single crystal seed crystals.
In a sharp-nose bottle, the weight ratio of the components is 1: 1, adding silicon nitride powder and water, and stirring uniformly to prepare the silicon nitride slurry. And filling the silicon nitride slurry around the plurality of single crystal strips, and naturally airing to form the silicon-based filling strips.
And then, silicon materials are loaded on the single crystal seed crystal layer and the plurality of single crystal strips, the silicon materials are completely melted by heating, the part of the single crystal seed crystal layer is partially melted, and the cast single crystal silicon ingot of the embodiment 2 is obtained after crystal growth.
Example 3
The cast single crystal ingot was cut to obtain a head, and subjected to PL test.
The cast single-crystal head single-crystal ingot having a defect ratio not lower than that shown in FIG. 5 was selected.
And cutting the head single crystal block with the larger defect ratio into a plurality of single crystal strips with the length of 158mm, the width of 5mm and the height of 20 mm.
6 x 6 blocks of 158mm x 20mm single crystal seeds were laid in the crucible.
And splicing and laying a plurality of cut single crystal strips end to end in sequence around the single crystal seed crystals.
In a sharp-nose bottle, according to the weight ratio of 2: 1: 1, adding silicon nitride powder, silicon powder and alcohol, and stirring uniformly to prepare the silicon nitride slurry. And filling the silicon nitride slurry around the plurality of single crystal strips, and naturally airing to form the silicon-based filling strips.
And then, silicon materials are loaded on the single crystal seed crystal layer and the plurality of single crystal strips, the silicon materials are completely melted by heating, the part of the single crystal seed crystal layer is partially melted, and the cast single crystal silicon ingot of the embodiment 3 is obtained after crystal growth.
Comparative example 1
6 x 6 seed cubes of 159mm x 25mm were laid in the crucible.
After the completion of the laying, a silicon material was charged on the single crystal seed layer, and then the same growth conditions as those in example 1 were successively applied to obtain a cast single crystal silicon ingot of comparative example 1.
Comparative example 2
Seed cubes of 6 x 6 of 158mm x 20mm were laid in the crucible.
After the completion of the laying, a silicon material was charged on the single crystal seed layer, and then the same growth conditions as those in example 2 were successively applied to obtain a cast single crystal silicon ingot of comparative example 2.
And (3) performance testing:
PL tests were performed on the side surfaces of the cast single crystal silicon ingots obtained in example 1 and comparative example 1, respectively, to obtain PL graphs shown in fig. 6 and 7. As can be seen from fig. 6, the cast silicon single crystal ingot obtained by the method for preparing a cast silicon single crystal ingot of example 1 had a small ratio of edge defects. As can be seen from fig. 7, the cast silicon single crystal ingot obtained by the method for preparing a cast silicon single crystal ingot according to comparative example 1 had a large ratio of edge defects. The method for preparing the cast monocrystalline silicon ingot can reduce the impurity content of corner silicon blocks and the probability of generating the defects of the corner silicon blocks.
Photographs were taken of the bottom corner blocks of the cast single crystal silicon ingots obtained in example 2, example 3 and comparative example 2 to obtain fig. 8, 9 and 10. As can be seen from fig. 8 and 9, the cast single crystal silicon ingots obtained in examples 2 and 3 did not show the phenomenon of siliconizing. The lower right corner of fig. 10 shows the state after the siliconizing, and it can be seen from fig. 10 that the siliconizing occurred at the bottom corner position of the cast single crystal silicon ingot obtained in comparative example 2. This shows that the silicon-based filler strips filled around the single crystal strips can effectively prevent silicon liquid from permeating into the bottom of the single crystal seed crystals of the corner blocks.
The technical features of the embodiments described above may be arbitrarily combined, and for the sake of brevity, all possible combinations of the technical features in the embodiments described above are not described, but should be considered as being within the scope of the present specification as long as there is no contradiction between the combinations of the technical features.
The above-mentioned embodiments only express several embodiments of the present invention, and the description thereof is more specific and detailed, but not construed as limiting the scope of the invention. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the inventive concept, which falls within the scope of the present invention. Therefore, the protection scope of the present patent shall be subject to the appended claims.
Claims (10)
1. A preparation method of a cast monocrystalline silicon ingot is characterized by comprising the following steps:
laying single crystal seed crystals at the bottom of the crucible to form a single crystal seed crystal layer;
laying at least one single crystal strip around the single crystal seed crystal layer, and splicing the single crystal strip and the adjacent single crystal seed crystal, wherein the defect ratio of the single crystal strip is greater than that of the adjacent single crystal seed crystal;
and loading silicon materials on the single crystal seed crystal layer and at least one single crystal strip, heating to completely melt the silicon materials and partially melt the single crystal seed crystal layer, and growing crystals to obtain the cast single crystal silicon ingot.
2. The method of preparing a cast single crystal silicon ingot according to claim 1, wherein the single crystal ingot is prepared by the method comprising: and cutting the cast single crystal block to obtain a head, detecting the defect ratio of the cutting surface, and cutting the head with the defect ratio of the cutting surface being more than 50% into a plurality of single crystal strips.
3. The method of manufacturing a cast single crystal silicon ingot as set forth in claim 2, wherein in the step of laying at least one single crystal strip around the single crystal seed layer, a cut surface of the single crystal strip having a defect ratio of more than 50% faces an adjacent single crystal seed crystal.
4. The method of preparing a cast single crystal silicon ingot according to claim 1, wherein the single crystal strip is a rectangular parallelepiped, the length and height of the single crystal strip are the same as those of the adjacent single crystal seed crystal, and the width of the single crystal strip is 5mm to 40 mm.
5. The method of preparing a cast single crystal silicon ingot as set forth in claim 1 wherein the side crystal orientation of the single crystal strips being spliced to each other is different from the side crystal orientation of the adjacent single crystal seed crystals.
6. The method according to claim 1, wherein the number of the single crystal strips is several, the several single crystal strips are sequentially spliced end to end, and the side crystal directions of two adjacent single crystal strips spliced with each other are different.
7. The method of claim 6, further comprising the step of, prior to charging the silicon charge:
and filling silicon-based slurry around the single crystal strip, wherein the silicon-based slurry is mixed slurry of silicon nitride and silicon powder or silicon nitride slurry, and drying to form the silicon-based filling strip.
8. The method according to claim 7, wherein the mass ratio of the silicon nitride to the silicon powder in the mixed slurry of the silicon nitride and the silicon powder is (2-10): 1.
9. the method of claim 7, wherein the ratio of the height of the silicon-based filler strips to the height of the single crystal seed crystal is (5-7): 10.
10. a cast silicon single crystal ingot produced by the method for producing a cast silicon single crystal ingot according to any one of claims 1 to 9.
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| CN113293434A (en) * | 2021-05-27 | 2021-08-24 | 江苏协鑫硅材料科技发展有限公司 | Seed crystal laying method and monocrystalline silicon casting method |
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