Seed crystal assembly

Abstract

The utility model discloses a seed crystal assembly, which relates to the field of casting monocrystalline silicon ingots, is suitable for casting monocrystalline silicon ingots, and comprises a seed crystal layer, a seed crystal layer and a crystal layer, the seed crystal layer comprises a plurality of seed crystals which are laid at the bottom of the crucible; a splicing seam is formed between every two adjacent seed crystals; a cushion block layer; the cushion block layer comprises a plurality of cushion blocks, and the plurality of cushion blocks are distributed on the seed crystal layer at intervals and cannot cover any splicing seam; a cover layer; the covering layer comprises a single or a plurality of silicon blocks; and the covering layer is arranged on the cushion block layer and partially or completely covers the seed crystal layer. According to the utility model, the three layers of seed crystal components are adopted, so that gaps exist in splicing seams; and the pressure of the splicing seam is reduced, so that the generation of a dislocation source is reduced, the dislocation density in the silicon ingot is reduced, and the weight of the monocrystalline silicon ingot is improved.

Description

Technical Field

[0001] The utility model relates to the field of casting single crystal silicon, in particular to a seed crystal component. Background Art

[0002] The cast single crystal silicon ingot is a product between the cast multicrystalline silicon ingot and the Czochralski single crystal silicon ingot. It has the advantages of low defects of Czochralski single crystal silicon, and can form a pyramid-shaped texture through the alkali texturing method to improve the absorption of light, thereby improving the conversion efficiency. At the same time, cast single crystal silicon also has the advantages of low production cost and high output of cast polycrystalline silicon.

[0003] The existing method for growing a cast single crystal silicon ingot requires that the bottom of the crucible be filled with seed crystals, and the single crystal silicon ingot is cast through the seed crystal seeding growth position when the seed crystals are not melted. In the actual production process, (1) since the seed crystals are laid at the bottom of the crucible, hundreds of kilograms of silicon material are usually placed above the seed crystals, resulting in huge pressure. In particular, the stress of the silicon material on the seed crystals at high temperatures can easily induce the generation of dislocation defects. (2) The seed crystals for casting single crystal silicon ingots are generally prepared by using CZ single crystal silicon blocks or high-quality cast single crystal silicon blocks. However, since the diameter of the CZ single crystal silicon ingot and the size of the high-quality cast single crystal silicon block are much smaller than the size of the crucible used to prepare the cast single crystal silicon ingot, in actual production, the seed crystal layer at the bottom of the crucible needs to be spliced ​​with multiple seed crystals. There will be splicing seams between the seed crystals, and thermal stress will be generated in such gaps, which are prone to crystal defects and seriously affect the quality of the cast single crystal silicon ingot.

[0004] Patent CN111910248B discloses a cast single crystal seed crystal, a cast single crystal silicon ingot and a preparation method thereof, a cast single crystal silicon wafer and a preparation method thereof, which mainly adopts a doping concentration between 3×10 16 atoms / cm3~1.5×10 19 A gallium-doped ingot single crystal seed crystal with a concentration of 100 atoms / cubic centimeter is used as the seed layer, so that oxygen precipitation can be significantly inhibited during the heat treatment process in the melting stage before crystal growth, so as to maintain the perfection of the crystal structure after heat treatment in the melting stage, reduce the breeding of dislocations, improve the ingot yield and silicon wafer efficiency, and thus achieve the purpose of reducing costs and increasing efficiency. However, due to the low segregation coefficient of gallium, the doping concentration of gallium-doped seed crystals is difficult to control and the preparation cost is relatively high. The concentration of gallium-doped seed crystals in the patent is relatively high. Excessive doping concentration will form a large number of point defects in the seed crystals, and dislocations are easily generated during high temperature processes, which is not conducive to the control of seeding defects. Therefore, it is difficult to apply in batches in actual production.

[0005] Therefore, there is an urgent need for a new seed crystal that can reduce crystal defects and improve the quality of cast single crystal silicon ingots. Utility Model Content

[0006] The utility model aims to solve at least one of the technical problems existing in the prior art. To this end, the purpose of the utility model is to provide a seed crystal assembly and cast single crystal silicon. The seed crystal assembly of the present application can significantly reduce the crystal defects of cast single crystal silicon ingots and improve the quality of cast single crystal silicon ingots.

[0007] The utility model discloses a seed crystal assembly, which is suitable for casting a single crystal silicon ingot, and comprises:

[0008] A seed crystal layer; the seed crystal layer comprises a plurality of seed crystals, and the plurality of seed crystals are laid on the bottom of the crucible; and a joint seam is formed between adjacent seed crystals;

[0009] A pad layer; the pad layer comprises a plurality of pads, the plurality of pads are spaced and distributed on the seed layer and cannot cover any of the joint seams;

[0010] The covering layer comprises a single silicon block or multiple silicon blocks; the covering layer is arranged on the pad layer and partially or completely covers the seed crystal layer.

[0011] Optionally, the total height difference of the seed crystal layer is 0-3 mm.

[0012] Furthermore, the upper surface and the lower surface of the pad are flat, and the total height difference between the pad layer and the seed crystal layer is less than 1 mm.

[0013] Furthermore, the thickness of the pad layer is 5-30 mm

[0014] Optionally, the distance between the edge of the pad disposed on the seed crystal and the adjacent joint seam is not less than 1 / 5 of the length or width of the seed crystal in the same direction;

[0015] Optionally, the length of the spacer block is 1 / 5-4 / 5 of the length of the seed crystal; the width of the spacer block is 1 / 5-4 / 5 of the width of the seed crystal.

[0016] Optionally, the spacers are evenly spaced and placed on the seed crystal layer.

[0017] Optionally, the spacer is placed on each of the seed crystals.

[0018] Optionally, the length of the seed crystal is 100-200 mm; the width of the seed crystal is 100-200 mm; and / or the height of the seed crystal is 10-30 mm.

[0019] Optionally, the silicon block is a single crystal silicon block, a cast single crystal silicon block or a polycrystalline silicon block.

[0020] Optionally, the seed crystal is a single crystal silicon block, and / or the spacer block is a single crystal silicon block, a cast single crystal silicon block or a polycrystalline silicon block.

[0021] Compared with the prior art, the beneficial effects of the utility model are:

[0022] (1) The utility model adopts a three-layer seed crystal assembly, a pad layer is arranged on the seed crystal layer, the pad layer does not cover the splicing seam, the covering layer covers the pad layer, and the splicing seam is located between the gaps between the pads, so that the splicing seam is left empty; the pressure of the splicing seam is reduced, thereby reducing the generation of dislocation sources, reducing the dislocation density in the silicon ingot, and increasing the weight of the cast single crystal silicon ingot.

[0023] (2) The pad layer used in the utility model can compensate for the height difference of the seed crystal layer, relieve the pressure on the joint seam with the height difference, and make the force on the seed crystal layer more uniform, thereby reducing the pressure on the joint seam, reducing the generation of dislocation sources, reducing the dislocation density in the silicon ingot, and increasing the weight of the cast single crystal silicon ingot. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is a front view schematic diagram of an embodiment of a quartz crucible filled with silicon material and including a seed crystal assembly of the utility model;

[0025] Figure 2 It is a top view schematic diagram of an embodiment of the seed crystal layer of the utility model;

[0026] Figure 3 It is a top view schematic diagram of an embodiment of the seed crystal layer and the pad layer of the utility model;

[0027] Figure 4 It is a top view schematic diagram of an embodiment of a seed crystal assembly of the utility model;

[0028] Figure 5 is a front view schematic diagram of an embodiment of a quartz crucible filled with silicon material including a seed crystal layer in the prior art;

[0029] Figure 6 is a schematic diagram of photoluminescence of a cast single crystal silicon block prepared according to the prior art;

[0030] Figure 7 This is a schematic diagram of the photoluminescence of a cast single crystal silicon block prepared in Example 1 of the utility model;

[0031] Figure 8 This is a schematic diagram of the photoluminescence of a cast single crystal silicon block prepared in Example 2 of the utility model;

[0032] Reference numerals:

[0033] 10-seed crystal assembly; 11-seed crystal layer; 110-seed crystal; 12-pad layer; 120-pad; 13-covering layer; 130-silicon block; 101-joining seam; 20-silicon material; 30-crucible; 40-dislocation. DETAILED DESCRIPTION

[0034] Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings. However, it should be understood that these descriptions are exemplary only and are not intended to limit the scope of the present disclosure. In addition, in the following description, descriptions of well-known structures and technologies are omitted to avoid unnecessary confusion of the concepts of the present disclosure.

[0035] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present utility model, the meaning of "multiple" is two or more, unless otherwise clearly and specifically defined. The meaning of "several" is one or more, unless otherwise clearly and specifically defined.

[0036] In the prior art, such as Figure 5-6 As shown, Figure 5 The schematic diagram of the crucible 30 with the seed crystal layer 11 and filled with silicon material 20 in the prior art is shown in the figure. As can be seen from the figure, since the bottom of the crucible 30 is relatively large and the size of a single seed crystal is relatively small, it is necessary to splice multiple seed crystals to form a large seed crystal to cover the bottom of the crucible 30. However, due to the uneven bottom of the crucible 30 or the large thickness deviation of the seed crystal, there is a height difference between the splicing areas of the seed crystals (such as Figure 5 As shown by the black circle in the figure, the pressure of the silicon material 30 on the joint seam 101 between the seed crystals will be affected, thereby generating dislocations; Figure 6 As shown, Figure 6 To adopt Figure 5 The photoluminescence image of the cast single crystal silicon block prepared by the prior art shows that the black coils in the image are dislocations 40. Due to the height difference, a large number of dislocations 40 are generated at the joint seam 101. The area ratio of the dislocations 40 is greater than 20%. The dislocation source continues to proliferate and diffuse in the subsequent growth, eventually causing the quality of the cast single crystal silicon ingot to deteriorate.

[0037] In this regard, Figure 1-4As shown, the utility model provides a seed crystal assembly 10, which is suitable for casting single crystal silicon ingots, and the seed crystal assembly 10 includes a seed crystal layer 11, a cushion layer 12 and a covering layer 13; the seed crystal layer 11 is laid on the bottom of the crucible 30, the cushion layer 12 is arranged above the seed crystal layer 11, and the covering layer 13 is arranged above the cushion layer 12; wherein, the seed crystal layer 11 includes a plurality of seed crystals 110, and the plurality of seed crystals 110 are laid on the bottom of the crucible 30; a joint seam 101 is formed between adjacent seed crystals 110; the cushion layer 12 includes a plurality of cushion blocks 120, and the plurality of cushion blocks 120 are arranged on the seed crystal layer 11 at intervals and cannot cover any joint seam 101; the covering layer 13 includes a single or multiple silicon blocks 130; the covering layer 13 is arranged on the cushion layer 12, partially or completely covering the seed crystal layer 11. Therefore, by arranging a pad layer 12 on the seed crystal 110 layer, the pad layer 12 does not cover the joint seam 101, and the covering layer 13 covers the pad layer 12, and the joint seam 101 is located between the gaps between the pads 120 and the pads 120, so that there is a space in the joint seam 101; when the silicon material 20 is placed on the covering layer 13, the gravity of the silicon material 20 is applied to the covering layer 13, and the covering layer 13 is transferred to the seed crystal layer 11 through the pad layer 12. Since there is a space in the joint seam 101, the pressure received is less. The seed crystal layer 11 is mainly subjected to force on the contact area of ​​the seed crystal 110 in contact with the pad 120, thereby effectively reducing the pressure of the joint seam 101, further reducing the generation of dislocation sources, and then effectively reducing the dislocation density in the silicon ingot, and increasing the weight of the single crystal silicon ingot.

[0038] Among them, Figure 2 As shown, the seed crystal layer 11 includes the seed crystal layer 11 comprising a plurality of seed crystals 110, the seed crystals 110 are rectangular or cube-shaped; the plurality of seed crystals is two or more, the plurality of seed crystals 110 are spliced ​​together by contact between the edges, and adjacent seed crystals 110 form a splicing seam 101, and the size of the splicing seam 101 is slightly different according to the flatness and size of the contact edges between the seed crystals 110 and the adjacent seed crystals 110.

[0039] In an optional manner, the length of the seed crystal 110 may be 100-200 mm, for example, 110 mm, 120 mm, 125 mm, 130 mm, 135 mm, 140 mm, 145 mm, 150 mm, 155 mm, 160 mm, 165 mm, 170 mm, 175 mm, 180 mm, 185 mm, 190 mm, 195 mm or 200 mm;

[0040] In an optional manner, the width of the seed crystal 110 may be 100-200 mm, for example, 110 mm, 120 mm, 125 mm, 130 mm, 135 mm, 140 mm, 145 mm, 150 mm, 155 mm, 160 mm, 165 mm, 170 mm, 175 mm, 180 mm, 185 mm, 190 mm, 195 mm or 200 mm;

[0041] In an optional manner, the height of the seed crystal 110 may be 10-30 mm, for example, 11 mm, 12 mm, 13 mm, 14 mm, 16 mm, 17 mm, 18 mm, 19 mm, 20 mm, 21 mm, 22 mm, 23 mm, 24 mm, 25 mm, 26 mm, 27 mm, 28 mm, 29 mm or 30 mm;

[0042] Therefore, by selecting seed crystals 110 with sizes that are as consistent as possible, the size of the joint seam 101 can be made more uniform.

[0043] In an optional manner, there is a certain height difference in the seed crystal layer 11, and the total height difference of the seed crystal layer 11 ranges from 0 to 3 mm, for example, it can be 0 mm, 0.5 mm, 1 mm, 1.5 mm, 2 mm, 2.5 mm or 3 mm; the smaller the height difference of the seed crystal layer 11, the better, but due to the influence of cost, the seed crystal layer 11 inevitably has a height difference. When the height difference is 0-3 mm, the present invention can compensate for the height difference by setting the subsequent pad layer 12, and does not affect the subsequent crystal growth. It should be noted that the total height difference of the seed crystal layer 11 refers to the difference between the highest point and the lowest point on the upper surface of the seed crystal layer 11; the height difference caused by the uneven crucible 30 is also calculated into the height difference range of the seed crystal layer 11.

[0044] In an optional manner, the seed crystal 110 is a single crystal silicon block, thereby growing a higher quality cast single crystal silicon ingot.

[0045] Furthermore, if Figure 3 As shown, the pad layer 12 includes multiple pads 120, and the pads 120 are columns, for example, they can be cubes, rectangular parallelepipeds, or irregular trapezoidal columns; the multiple pads are at least two or more, and since a covering layer 13 needs to be set above the pad layer 12, at least two pads 120 are required to support the covering layer 13. Preferably, the multiple pads are at least four or more, and the four pads 120 are distributed at intervals within the outer circumference of the seed layer 11, so that the subsequent covering layer 13 can more comprehensively cover the pad layer 12; the upper and lower surfaces of the pads 120 are flat, so that they can be placed on the seed layer 11 more stably, and the pads 120 are distributed at intervals on the seed layer 11 and cannot cover any joint seams 101.

[0046] In an optional manner, the total height difference between the pad layer 12 and the seed layer 11 is less than 1 mm; thus, by providing the pad layer 12, the thickness difference of the seed layer 11 can be compensated, so that the pressure of the silicon material 20 on the subsequent seed layer 11 can be more uniform, reducing the generation of dislocations. It should be noted that the total height difference between the pad layer 12 and the seed layer 11 refers to the difference between the highest point and the lowest point on the upper surface of the pad layer 12; the height difference caused by the uneven crucible 30 and the height difference of the seed layer 11 are also calculated within the height difference range of the total height difference between the pad layer 12 and the seed layer 11.

[0047] Among them, the height of the pad 120 can be 5-30mm, for example, it can be 5mm, 6mm, 7mm, 8mm, 9mm, 10mm, 11mm, 12mm, 13mm, 14mm, 16mm, 17mm, 18mm, 19mm, 20mm, 21mm, 22mm, 23mm, 24mm, 25mm, 26mm, 27mm, 28mm, 29mm or 30mm; the height of the pad layer 12 affects the total height deviation between the pad layer 12 and the seed layer 11 and affects the stress of the covering layer 13. When the height of the pad layer 12 is in the range of 5-30mm, it can make up for the height difference of the seed layer 11, thereby growing a higher quality cast single crystal silicon ingot.

[0048] Among them, the distance between the edge of the pad 120 arranged on the seed crystal 110 and the adjacent splicing seam 101 is not less than 1 / 5 of the length or width of the seed crystal 110 in the same direction; in the length direction of the seed crystal 110, the minimum distance between the edge of the pad 120 placed on the seed crystal 110 and the splicing seam 101 is greater than or equal to one-fifth of the length of the seed crystal 110; similarly, in the width direction of the seed crystal 110, the minimum distance between the edge of the pad 120 and the splicing seam 101 is greater than one-fifth of the length of the seed crystal 110; thereby, it can be prevented that the distance between the pad and the splicing seam is too close, resulting in the pad moving and covering the splicing seam during the subsequent installation of the covering layer or the addition of silicon material, and the pad layer can more stably support the weight of the covering layer and the silicon material.

[0049] Furthermore, the side width of a single pad 120 is smaller than the side width of the seed crystal 110; in a specific embodiment, the length of the pad 120 is 1 / 5-4 / 5 of the length of the seed crystal 110; for example, it can be 1 / 5, 2 / 5, 3 / 5 or 4 / 5; the width of the pad 120 is 1 / 5-4 / 5 of the width of the seed crystal 110, for example, it can be 1 / 5, 2 / 5, 3 / 5 or 4 / 5. Since the pad 120 cannot cover the joint seam 101 of the seed crystal layer 11, a single pad 120 cannot be set on two or more seed crystals 110, but can only be set on a single seed crystal 110. In order to make the subsequent seed crystal layer 11 more uniformly stressed and in the subsequent addition of silicon material 20, the pad layer 12 may move a small amount to cover the joint seam 101, so the size of a single pad 120 is preferably in the range of 1 / 5-4 / 5 of the length of the seed crystal 110.

[0050] Furthermore, a pad 120 is placed on each seed crystal 110 ; since a pad 120 is disposed on each seed crystal 110 , the force applied to the seed crystal layer 11 will be more uniform.

[0051] More preferably, the central axis of a single seed crystal 110 coincides with the central axis of the cushion block 120 , so that the force on the seed crystal 110 is at the center position, making the force on the seed crystal layer 11 more uniform.

[0052] In an optional manner, the pad 120 can be a single crystal silicon block, a cast single crystal silicon block or a polycrystalline silicon block. Thus, the pad layer 12 can not only make the seed layer 11 more uniformly stressed, but also can be used as a raw material for casting single crystal silicon ingots, thereby increasing the production capacity of casting single crystal silicon ingots.

[0053] Among them, Figure 4 As shown, a covering layer 13 is arranged above the pad layer 12, and the covering layer 13 partially or completely covers the seed crystal layer 11; by arranging the covering layer 13 on the pad layer 12, the covering layer 13 can bear the gravity of the silicon material 20, so that the pad 120 can evenly transfer the pressure to the seed crystal layer 11; the covering layer 13 needs to prevent the silicon material 20 from falling onto the seed crystal layer 11, so it is necessary to at least mostly or completely cover the seed crystal layer 11; when the silicon material 20 is a block raw material and the block size is relatively large, the peripheral area of ​​the covering layer 13 may not completely cover the seed crystal layer 11, and at this time the silicon block cannot enter the seed crystal layer 11 through the blank area above the seed crystal layer 11. Preferably, the covering layer 13 completely covers the seed crystal layer 11, thereby preventing the silicon material 20 from falling into the seed crystal layer 11 and affecting the stress condition of the seed crystal layer 11.

[0054] Preferably, the cover layer 13 completely covers the spacer layer 12 , and the spacer layers 12 are evenly spaced and distributed on the seed crystal layer 11 , so that the seed crystal layer 11 is subjected to a more uniform pressure from the silicon material 20 thereon.

[0055] The cover layer 13 may be a single silicon block 130, such as a single crystal silicon block, a cast single crystal silicon block or a polycrystalline silicon block. Thus, the pad layer 12 can not only make the seed layer 11 more uniformly stressed, but also can be used as a raw material for casting single crystal silicon ingots, thereby increasing the production capacity of casting single crystal silicon ingots.

[0056] In an optional manner, the covering layer 13 can be at least two silicon blocks 130, and adjacent silicon blocks are tightly spliced ​​together and placed on the pad 120, so that there will be no large gaps between the silicon blocks 130 on the covering layer 13, thereby preventing the silicon material 20 from falling from the gaps onto the seed crystal layer 11 and affecting the force on the splicing seam 101 of the seed crystal 110.

[0057] The main preparation method for casting a single crystal silicon ingot is to lay out the seed crystal assembly 10, place a block silicon material 20 of regular size on the covering layer 13, and place an irregular-sized silicon material 20 or a granular silicon material 20 on the silicon material 20 of regular size; after the loading is completed, the ingot is cast, and during the melting process, the silicon material in the crucible gradually melts from top to bottom, and the seed crystal layer 11 melts last, and the seed crystal 110 is detected by a quartz rod, so that the single crystal silicon seed crystal 110 is not completely melted and then enters the crystal growth, and finally a cast single crystal silicon ingot is obtained.

[0058] In the utility model, by setting a three-layer seed crystal 110 assembly, the seed crystal 110 layers are subjected to uniform force during the entire melting process of the silicon material, and gaps are left on the joints, which are not affected by concentrated pressure; the pressure on the seed crystal 110 layers is relatively uniform from beginning to end, thereby effectively reducing the generation of dislocations.

[0059] The seed crystal 110 assembly disclosed in the present invention is described in detail below with reference to several specific embodiments. It is worth noting that the following description is only for illustrative purposes and is not a specific limitation of the invention. Example

[0060] Select a single crystal silicon block seed crystal 110, the size of the seed crystal 110 is 168mm×168mm×25mm (length×width×height), during the selection process, the size error of the seed crystal 110 is less than or equal to + / -2mm, the seed crystal 110 is spliced ​​at the bottom of the crucible, adjacent seed crystals 110 cover the bottom of the crucible, and the height difference of the seed crystal 110 layer is 1-3mm;

[0061] Pads are laid on the upper surface of each seed crystal 110. The pads are single crystal silicon blocks with a size of 100 mm×100 mm×15 mm (length×width×height). The size error of the pads is less than or equal to + / -2 mm. The distance between the edge of the pads and the nearest joint is 30-60 mm. After the pads are laid, the total thickness difference between the seed crystal 110 layer and the pad layer is less than or equal to 1 mm.

[0062] A covering layer is laid on the pad layer. The covering layer is a polycrystalline silicon block. The size of the covering layer is 158mm×158mm×30mm (length×width×height). The size error of the covering layer is less than or equal to + / -2mm. Multiple polycrystalline silicon blocks are spliced ​​together to completely cover the seed crystal 110 layers.

[0063] Silicon material is filled on the cover layer, and then crystal growth is carried out to obtain a cast single crystal silicon ingot.

[0064] like Figure 7 As shown, the cast single crystal silicon ingot was squared to obtain a silicon block and tested for photoluminescence images. The area ratio of dislocation defects in the figure is less than 1.5%. Example

[0065] Select a single crystal silicon block seed crystal with a size of 158mm×158mm×25mm (length×width×height). During the selection process, the size error of the seed crystal is less than or equal to + / -2mm. Splice the seed crystal at the bottom of the crucible, and the adjacent seed crystals cover the bottom of the crucible. The height difference of the seed crystal layer is 0.5-2mm.

[0066] Pads are laid on the upper surface of each seed crystal. The pads are single crystal silicon blocks with a size of 100mm×100mm×10mm (length×width×height). The size error of the pads is less than or equal to + / -2mm. The distance between the edge of the pads and the nearest joint is 20-50mm. After the pads are laid, the total thickness difference between the seed crystal layer and the pad layer is less than or equal to 1mm.

[0067] A covering layer is laid on the pad layer. The covering layer is a polysilicon block. The size of the covering layer is 158mm×158mm×20mm (length×width×height). The size error of the covering layer is less than or equal to + / -2mm. Multiple polysilicon blocks are spliced ​​together to completely cover the pad layer.

[0068] Silicon material is filled on the cover layer, and then crystal growth is carried out to obtain a cast single crystal silicon ingot.

[0069] like Figure 8 As shown, the cast single crystal silicon ingot was squared to obtain a silicon block and tested for photoluminescence images. The area ratio of dislocation defects in the figure is less than 2%.

[0070] It can be seen that the utility model adopts a three-layer seed crystal assembly, a pad layer is arranged on the seed crystal layer, the pad layer does not cover the splicing seam, the covering layer covers the pad layer, and the splicing seam is located between the gaps between the pads, so that the splicing seam is left empty; the pressure on the splicing seam is reduced, thereby reducing the generation of dislocation sources, and the pad layer makes up for the height difference of the seed crystal layer, so that the area ratio of the dislocation is reduced from more than 20% to less than 5%.

[0071] Although the present invention is described herein in conjunction with various embodiments, in the process of implementing the claimed invention, those skilled in the art may understand and implement other changes to the disclosed embodiments by viewing the drawings, the disclosure, and the appended claims. In the claims, the word "comprising" does not exclude other components or steps, and "one" or "an" does not exclude multiple situations. A single processor or other unit may implement several functions listed in a claim. Certain measures are recorded in mutually different dependent claims, but this does not mean that these measures cannot be combined to produce good results.

[0072] Although the utility model has been described in conjunction with specific features and embodiments thereof, it is obvious that various modifications and combinations may be made thereto without departing from the spirit and scope of the utility model. Accordingly, this specification and the drawings are merely exemplary illustrations of the utility model as defined by the appended claims, and are deemed to have covered any and all modifications, variations, combinations or equivalents within the scope of the utility model. Obviously, those skilled in the art may make various modifications and variations to the utility model without departing from the spirit and scope of the utility model. Thus, if these modifications and variations of the utility model fall within the scope of the claims of the utility model and their equivalents, the utility model is also intended to include these modifications and variations.

Claims

1. A seed crystal assembly suitable for casting single crystal silicon ingots, It is characterized in that include: seed layer; The seed crystal layer comprises a plurality of seed crystals, and the plurality of seed crystals are laid on the bottom of the crucible; and a joint seam is formed between adjacent seed crystals; A pad layer; the pad layer comprises a plurality of pads, and the plurality of pads are arranged on the seed layer in an interval and cannot cover any of the joint seams; The covering layer comprises a single silicon block or multiple silicon blocks; the covering layer is arranged on the pad layer and partially or completely covers the seed crystal layer.

2. The seed crystal assembly according to claim 1, It is characterized in that The total height difference of the seed layer is 0-3 mm.

3. The seed crystal assembly according to claim 2, It is characterized in that The upper surface and the lower surface of the pad are flat, the total height difference between the pad layer and the seed crystal layer is less than 1 mm, and / or the thickness of the pad layer is 5-30 mm.

4. The seed crystal assembly according to claim 1, It is characterized in that The distance between the edge of the pad set on the seed crystal and the adjacent joint seam is not less than 1 / 5 of the length or width of the seed crystal in the same direction, and / or the length of the pad is 1 / 5-4 / 5 of the length of the seed crystal; the width of the pad is 1 / 5-4 / 5 of the width of the seed crystal.

5. The seed crystal assembly according to claim 1, It is characterized in that The pads are evenly spaced and placed on the seed crystal layer.

6. The seed crystal assembly according to claim 1, It is characterized in that The spacer is placed on each of the seed crystals.

7. The seed crystal assembly according to claim 1, It is characterized in that The length of the seed crystal is 100-200 mm; the width of the seed crystal is 100-200 mm; and / or the height of the seed crystal is 10-30 mm.

8. The seed crystal assembly according to claim 1, It is characterized in that The silicon block is a single crystal silicon block, a cast single crystal silicon block or a polycrystalline silicon block.

9. The seed crystal assembly according to claim 1, It is characterized in that The seed crystal is a single crystal silicon block, and / or the spacer block is a single crystal silicon block, a cast single crystal silicon block or a polycrystalline silicon block.

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